HomeMy WebLinkAbout2024 General Sewer Plan Appendices Volume 1Appendix A
2019 Stormwater Management Plan
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Stormwater Management Plan
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January 2019
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January 2019 │ 553-2836-004
Stormwater Management Plan
Prepared for
City of Port Townsend
Prepared by
Parametrix
719 2nd Avenue, Suite 200
Seattle, WA 98104
T. 206.394.3700 F. 1.855.542.6353
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CITATION
Parametrix. 2019. Stormwater
Management Plan. Prepared by
Parametrix, Seattle, WA. January 2019.
Stormwater Management Plan
City of Port Townsend
January 2019 │ 553-2836-004 i
TABLE OF CONTENTS
1. INTRODUCTION AND PURPOSE ............................................................................................. 1-1
1.1 Public Input Process ...................................................................................................................... 1-1
1.2 Introduction .................................................................................................................................. 1-1
1.3 Comprehensive Program Mission ................................................................................................. 1-2
1.4 Plan Outline ................................................................................................................................... 1-2
1.5 Plan Resources .............................................................................................................................. 1-3
2. THE WATERSHEDS AND BASINS ............................................................................................ 2-1
2.1 Project Area Description ............................................................................................................... 2-1
2.2 Physical Conditions of the Area .................................................................................................... 2-1
2.2.1 Topography and Drainage................................................................................................ 2-1
2.2.2 Local Geology ................................................................................................................... 2-2
2.2.3 Soils .................................................................................................................................. 2-9
2.3 Area Climate and Hydrology ......................................................................................................... 2-9
2.3.1 Hydrology ......................................................................................................................... 2-9
2.4 Water Quality .............................................................................................................................. 2-10
2.5 Climate Change ........................................................................................................................... 2-10
3. THE BUILT ENVIRONMENT .................................................................................................... 3-1
3.1 Land Use ........................................................................................................................................ 3-1
3.1.1 Existing Land Cover .......................................................................................................... 3-2
3.1.2 Future Land Use and Land Cover ..................................................................................... 3-9
3.1.3 Estimating Runoff Potential ........................................................................................... 3-15
3.1.4 Catchments with Largest Increase Potential ................................................................. 3-25
3.2 Stormwater System Operation and Maintenance ...................................................................... 3-27
3.2.1 Asset Identification ........................................................................................................ 3-28
3.2.2 Level of Service .............................................................................................................. 3-28
3.2.3 Reporting ....................................................................................................................... 3-28
4. BASIN PLANNING .................................................................................................................. 4-1
4.1 Planning Objectives ....................................................................................................................... 4-1
4.2 Drainage Connectivity ................................................................................................................... 4-1
4.2.1 Drainage System Hierarchy .............................................................................................. 4-2
4.2.2 Drainage System Connectivity ......................................................................................... 4-6
4.2.3 Drainage System Protection ............................................................................................ 4-6
4.2.4 Evaluating Potential Capacity Needs and Impacts ........................................................... 4-8
4.2.5 Drainageway Potential Impact Assessment ................................................................... 4-21
4.2.6 Potential Impacts to Closed System Wetlands .............................................................. 4-25
4.3 Drainage System Stormwater Improvements ............................................................................ 4-25
4.4 Roadway Inventory for Upgrade Opportunities ......................................................................... 4-26
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City of Port Townsend
TABLE OF CONTENTS (CONTINUED)
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5. CAPITAL PROJECTS PLAN ....................................................................................................... 5-1
5.1 Proposed Capital Projects ............................................................................................................. 5-1
5.2 Proposed Recurring Capital Projects ............................................................................................ 5-5
6. IMPLEMENTATION ................................................................................................................ 6-1
6.1 Capital Plan Priorities and Schedule ............................................................................................. 6-1
6.1.1 Capital Projects for Existing Flood Control ...................................................................... 6-1
6.1.2 Non-Capital Recurring Projects ........................................................................................ 6-2
6.2 Stormwater Control Standards and Policies ................................................................................. 6-3
6.2.1 Stormwater Control from New Development ................................................................. 6-3
6.2.2 Drainage System Protection ............................................................................................ 6-4
6.2.3 Drainage System Review and Upgrades .......................................................................... 6-7
6.2.4 Other Drainage System Protection Measures ................................................................. 6-8
6.3 Funding and Resources ............................................................................................................... 6-10
6.3.1 Capital Projects .............................................................................................................. 6-10
6.4 Summary Implementation Plan .................................................................................................. 6-12
7. REFERENCES ......................................................................................................................... 7-1
LIST OF FIGURES
1 Stormwater Drainage Basins ......................................................................................................... 2-3
2 Drainage Basins Discharge Locations ............................................................................................ 2-4
3 Topography ................................................................................................................................... 2-5
4 Flood Hazard Zones ....................................................................................................................... 2-6
5 Area Geology ................................................................................................................................. 2-7
6 Annual Water Budget ................................................................................................................... 2-8
7 Hydrologic Soil Groups ................................................................................................................ 2-11
8 Drainage Catchment Areas ........................................................................................................... 3-7
9 Land Use ...................................................................................................................................... 3-11
10 Vacant Lands and Development Potential .................................................................................. 3-12
11 Catchment Nodes ....................................................................................................................... 3-17
12 Stormwater Facilities .................................................................................................................... 4-3
13 Stormwater System Levels ............................................................................................................ 4-4
14a Pipe Capacity “Look Up Table” ..................................................................................................... 4-9
14b Ditch Capacity “Look up Table” .................................................................................................. 4-10
15 Long Paths, CDCs & KDs .............................................................................................................. 4-11
16 Roadway Drainage for Long Path Conveyance Sizing ................................................................. 4-19
17 CDCs & KDs High Velocity Reaches ............................................................................................. 4-23
18 Future Impact Estimate Wetland Footprints .............................................................................. 4-27
19 Capital Projects ............................................................................................................................. 5-3
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City of Port Townsend
TABLE OF CONTENTS (CONTINUED)
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LIST OF TABLES
2-1 Rainfall Depths for 24-Hour Events .............................................................................................. 2-9
3-1 Existing Land Cover ....................................................................................................................... 3-2
3-2 Existing Land Use Model Inputs .................................................................................................... 3-4
3-3 Future Land Use Model Inputs ................................................................................................... 3-13
3-4 Buildable Area – Impervious Comparison................................................................................... 3-19
3-5a Peak Runoff at Nodes or for Total Catchment – Existing ............................................................ 3-23
3-5b Peak Runoff at Nodes or for Total Catchment – Future ............................................................. 3-24
3-6 Potential Change in Peak Flows by Catchment Area .................................................................. 3-25
3-7 Existing Inventory of Public Facilities .......................................................................................... 3-29
3-8 Maintenance Frequency and Personnel ..................................................................................... 3-30
4-1 Basins and Disposition or Discharge Point .................................................................................... 4-2
4-2a Pipe Capacity for Reaches of Different Slopes .............................................................................. 4-9
4-2b Ditch Capacity for Reaches of Different Slopes ............................................................................ 4-9
4-3 Catchment Area Peak flows and Maximum Required Drainage Conveyance ............................ 4-13
4-4 Drainage Facility Size Estimates for Drainage Paths Exceeding Minimum Conveyance Sizing .. 4-15
4-5 Peak Flows in Reaches for Structure Sizing ................................................................................. 4-17
4-6 Peak flows in Reaches for Long-Path Conveyance Sizing ........................................................... 4-18
4-7 Peak Flow Increase at Key Nodes due to future Development .................................................. 4-21
4-8 CDC and KD Velocity Thresholds ................................................................................................. 4-22
4-9 Potentially Impacted Wetlands................................................................................................... 4-25
5-1 Capital Projects ............................................................................................................................. 5-2
5-2 Other Built Capital Projects ........................................................................................................... 5-5
6-1 Capital Projects Rankings and Priority .......................................................................................... 6-1
6-2 Summary of the Roadway Drainage Improvement Plan .............................................................. 6-2
6-3 Summary of Stormwater Control and Drainage Protection ......................................................... 6-6
6-4 Summary of Drainage System Review and Upgrades ................................................................... 6-7
6-5 Summary of Other Drainage System Protection Measures .......................................................... 6-9
6-7 Summary Cost Plan – Capital (2019-2024) ................................................................................. 6-10
6-8 Summary Cost Plan - Resources .................................................................................................. 6-11
6-9 Summary Implementation Schedule .......................................................................................... 6-12
6-10 Updated CIP with $6 Surcharge and Development Fee.............................................................. 6-15
Stormwater Management Plan
City of Port Townsend
TABLE OF CONTENTS (CONTINUED)
iv January 2019 │ 553-2836-004
APPENDICES
A Kickoff Meetings
B Public Input Process
C FEMA Flood Mapping
D Modeling Analysis
E Roadway Inventory
F Small-Site Stormwater Management Guide
G Capital Projects Worksheets
H Stormwater Manual Comparison
I Updated Capital Improvements Plan
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City of Port Townsend
January 2019 │ 553-2836-004 v
ACRONYMS AND ABBREVIATIONS
BMP best management practice
CAO Critical Area Ordinance
CDC Critical Drainage Corridors
Ecology Washington State Department of Ecology
EDS Engineering Design Standards
FTE full time equivalent
HSG hydrologic soil groups
KD Key Drainageway
LID low impact development
MEP maximum extent practicable
NOAA National Oceanic and Atmospheric Administration
NPDES National Pollution Discharge Elimination System
NRCS Natural Resources Conservation Service
PTMC Port Townsend Municipal Code
RSL relative sea level
SMP Stormwater Management Plan
SWMMWW Stormwater Management Manual for Western Washington
USDA U.S. Department of Agriculture
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City of Port Townsend
January 2019│ 553-2836-004 1-1
1. INTRODUCTION AND PURPOSE
1.1 Public Input Process
The planning process included public participation via public open house, public comment periods and a
technical advisory task force committee. The first SMP Technical Advisory Task Force meeting was held
on August 30, 2017. The purpose of the Task Force was to provide a wide variety of perspectives on the
City’s existing stormwater utility and input on the creation and adoption of the SMP. A second task force
meeting was held on November 2, 2017. Materials provided in the two meetings are included in
Appendix A.
A public open house was held between the two Task Force meetings to present the plan purpose and
findings (to date) and solicit input from the general public, such as known flooding problems for capital
project.
During the SMP adoption process there were two public comment periods. The first comment period
was early in the process and the goal was to gain feedback on what topics the public would like to see
covered in the SMP and what was important regarding stormwater. The second comment period was to
provide comments on the draft version of the SMP
The input provided throughout the public participation process was reviewed by the Plan team and
included where appropriate in this final draft. The materials and minutes from city council sub-
committee meetings, planning commission meetings and workshops, and the city council meetings and
workshop are included in Appendix B.
1.2 Introduction
The City of Port Townsend is unique in many ways, notably when it comes to climate, landscape, and
history of its development. Annual rainfall of about 17 inches is 70 percent of the amount that falls in
Port Angeles, just 30 miles to the west, and 25 percent of Quilcene’s, 23 miles to the south. There are no
“streams” in our common understanding of the term and the City is surrounded on three sides by water:
the Strait of Juan de Fuca, Admiralty Inlet, and Port Townsend Bay (all parts of the Salish Sea). Much of
the land was platted in the 1890s, with no regard to topography, drainage patterns, or infrastructure.
These conditions result in challenges for the City and property owners to follow natural drainage
patterns, control changes from new development, and apply western Washington stormwater manual
standards that were developed for wetter climates with streams and more traditional land development
approaches.
In 1986, the City prepared the “Comprehensive Storm Water Drainage Plan for Port Townsend”
(CH2MHill et al. 1987) which was used as the basis for establishing the City’s municipal stormwater utility.
Deficiencies in this plan were noted when preparing the Growth Management Plan in the early 1990s,
which resulted in initiating a new comprehensive plan (Port Townsend 1996) and an updated Stormwater
Management Plan (SMP) (Port Townsend 1999). Notable in the draft 1999 SMP was the idea of a “natural
drainage systems” approach, which included the mapping of “Critical Drainage Corridors”. The draft 1999
plan was never adopted; however, the natural drainage systems approach was adopted through the 1996
Comprehensive Plan through policies and goals in both the Land Use and Utility Elements of the 1996
Comprehensive Plan. The Critical Drainage Corridors were protected through regulatory language in the
city’s Critical Area Ordinance (CAO).
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This SMP update addresses ongoing management of the existing system and plots a course for the
future of the system. While there are many pieces already in place—system mapping, adopted
standards, and a recognized need to consider development and protect resources—the SMP includes
analyses, approaches, priorities, specific projects, mechanisms, updated performance standards, and an
implementation plan. In addition, since stormwater practice and regulations continue to evolve and the
approach and responsibility of municipalities to control stormwater discharges and manage
infrastructure increases, this Plan recommends policy and regulatory updates. The SMP is an important
tool for the City to use for day-to-day development review, operations, and long-term planning.
The objectives of the SMP include:
• Updating and defining drainage connectivity and mapping;
• Preparing updated policies for protecting the natural and built drainage system;
• Describing approaches to protect and improve the existing roadway drainage system;
• Preparing standard designs for future road drainage infrastructure;
• Assessing the existing impacts and potential changes due to new development;
• Preparing concept designs for capital projects to address existing stormwater problem areas;
and
• Preparing site development information and review materials, including low impact development
(LID) measures, redevelopment, new site development, and water quality retrofitting.
The SMP presents the background objectives existing conditions summary, basin analysis, consideration
of future land use, recommended stormwater controls, and capital projects to address existing
stormwater problems.
1.3 Comprehensive Program Mission
The project kick-off with both the City and Parametrix teams was held on June 20, 2017. The purpose of
the kickoff was to develop the Plan vision and team mission to complete the plan, brainstorm the Plan
needs and goals, discuss risks and threats to project success, and finalize the schedule and work plan for
the adoption of an updated SMP. The team agreed on the following Vision and Mission statement:
A fully functional, achievable, and sustainable stormwater system that is integrated
into the landscape, supports envisioned growth, protects residents, and nurtures the
environment.
Additional information to help guide plan preparation was collected by the team. The kick-off meeting
day included a field tour of key areas and problem areas in the city. Notes from the meeting
brainstorming are provided in Appendix A.
1.4 Plan Outline
The Plan structure follows this general outline: Section 2 describes the study area, with a discussion of
the physical setting and natural drainage system; Section 3 describes the current built environment in
the context of how it affects water resources, such as land cover and stormwater facilities; Section 4
describes the basis for stormwater planning, establishes stormwater control targets, and presents the
proposed SMP approaches; Section 5 describes the proposed capital projects; and Section 6 includes the
implementation plan.
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1.5 Plan Resources
The City prepared the Draft Storm Water Management Plan in 1999 (Port Townsend 1999). This plan
was very thorough and provides a strong platform on which this SMP plan update was built. Key
material used for a starting point includes the original drainage basin mapping and critical drainage
corridors (CDC) map.
The existing available GIS mapping from the city was used extensively, including topography, the
mapped drainage basins, CDCs, road network, drainage patterns and conveyance, wetlands, floodplains
and soils mapping. The City staff also prepared new information for this plan, such as a roadway
inventory, new and revised catchment inventory, and updated CDC and key drainageway (KD) mapping.
Other information, such as water quality sampling and some rainfall data, was provided by the City.
Other geology and climate data were collected from reliable Internet sources.
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City of Port Townsend
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2. THE WATERSHEDS AND BASINS
2.1 Project Area Description
The City is located on the Quimper Peninsula, surrounded on three sides by the Strait of Juan de Fuca,
Admiralty Inlet, and Port Townsend Bay, all parts of the Salish Sea. Figure 1 shows the city limits, streets,
named receiving waters, wetlands and potential wetlands, CDCs, KDs, and drainage basins. There are no
well-defined perennial or named streams. There is a long linear depression that generally drains toward
“Chinese Gardens” which contains a connected series of wetlands and a designated floodplain. CDCs are
regulated by the City’s Critical Areas ordinance. KDs are defined in this Plan and regulated by
stormwater codes and design standards.
The general disposition of surface waters is shown on Figure 2. Drainage basins in the City drain either to
closed depressions or directly to the ocean. The basins that discharge to the ocean are via a storm sewer
system, flow through surface ravines or through outlets from the two large named wetlands, Chinese
Gardens and Kah Tai Lagoon. The closed basins discharge into groundwater at small wetlands. Additional
detailed discussion of the drainage basins is provided in the 1987 Comprehensive Stormwater Drainage
Plan (CH2M Hill et al. 1987).
2.2 Physical Conditions of the Area
2.2.1 Topography and Drainage
The landscape and general topography of the City indicates irregular and undulating slopes. Figure 3 is a
topographic map of the City which shows the location of the low-lying areas, closed depressions and
geologic drainage features. Generally, there are relatively flat “plateaus” along the east and west sides
of the City with a valley (low lands) going through the middle. High bluffs dominate the ocean edge.
Strong erosional drainage patterns are not well-seen and are generally limited to drainage from the
plateau, notably in the southwest corner of the city. The formation of the large-scale landforms found
are an outcome of many processes, including deposition by advancing and receding glaciers, changing
sea levels, isostatic rebound after the glaciers have gone, and other apparent significant land forming
events. However, there is little evidence of landscape-level changes due to streams and flowing water
over the last several thousand years since the glaciers retreated, other than very local drainage patterns.
The topography of the City indicates low-lying areas and subtle drainage paths to form the natural
drainage disposition shown on Figures 2 and 3. Topographic maps and the built environment (i.e., both
built drainage network and existing roads) were used to define the drainage basins and their discharge
location. Figure 3 indicates by shading the location of low-lying drainage patterns within the major
drainage basins that lead to receiving water. The drainage patterns described in this section and shown
on Figures 1 through 3 form the drainage network on which the stormwater planning is based.
As shown on Figure 2, stormwater runoff drains directly to: the ocean either via storm sewers (pipes) or
from the two large named wetlands (Chinese Gardens and Kah Tai Lagoon) via an overflow pipe or to
closed basins that discharge into the groundwater, often at small wetlands and surface ravines. The flow
path and disposition of stormwater is an important factor in the stormwater impact analysis, future
control decisions and policies and potential basin retrofitting.
Stormwater Management Plan
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Designated floodplains and coastal flood hazard zones as mapped by FEMA exist in the low coastline
areas along the entire City shoreline (Figure 4). The only non-coastal floodplain in the City has also been
mapped in Drainage Basin 4, for which detailed information can be found in Appendix C (Polaris 1996).
Wetlands have also been mapped throughout the city annotated as “wetlands” or “potential wetlands”
(Figure 4). A wetland has been delineated by a wetland specialist and documented by a wetland report;
a potential wetland is identified through aerial mapping by a topographic depression or wet area in the
landscape and does not have a delineation wetland report and has not been field verified.
2.2.2 Local Geology
The geology and climate of the area contribute substantially to defining stormwater planning
approaches for the City. The relatively poorly defined natural drainage paths are a direct result of the
recent geologic past and the lack of rainfall to form drainage patterns and provide perennial streams.
The dominant geologic formation that resulted in local landforms is known as the Vashon recessional
drift, made up of sediments deposited during and after the last retreat of the Puget Lobe glacier. The
landforms are made up of a combination of materials deposited during previous advances as till,
outwash coming from the glacier as it retreated, and materials left behind as the ice stagnated and
melted. Because the Vashon recessional drift is the last deposit left by the melting glacier, it is relatively
undisturbed (Washington State Department of Ecology [Ecology] 1981). No interpretations of the
existing smaller-scale landforms in the City were found, and virtually all of the City is mapped as “Vashon
Till (Qvt)” on the Surficial Geologic Map of the Port Townsend Quadrangle (Pessl et al. 1989) (Figure 5).
Small areas of “Marsh, Swamp, or Bog” (Qm), “Recessional-Continental” deposits (Qvrc) and “Advance
Outwash” (Qva) are also found. This mixture of material sources, depositional environments, and
geologic processes demonstrates that highly variable landforms.
As described earlier, annual rainfall in the City is very low when compared to nearby areas due to the
Olympic Mountains rain shadow. In addition, the historical forest cover before the arrival of European
settlement resulted in low basin response and runoff from the rain that does fall. Consequently, there
was limited water available to carve drainage channels. Low areas that appear to have been created by
water are present (see Figure3) and may have resulted from the last processes of the melting glaciers or
in the slow response to several thousand years of rainfall since the glaciers melted.
Ecology conducted a study of ground water resources in eastern Jefferson County (Ecology 1981) and
developed a compelling analysis of the annual water budgets for the Port Townsend area that
demonstrates the amount of water typically available for surface water runoff. Figure 6, replicated here
from Ecology 1981, shows the relative percentages of average annual rainfall needed to replenish soil
moisture and the resultant remaining water surplus available for runoff. The results show that the
average annual excess water available (water surplus) for runoff is just 0.6 inches (precipitation minus
evapotranspiration), although under seasonally variable infiltration and evapotranspiration or in
different locations, it could be more or less. This is a very small amount of water available for runoff. By
comparison, the excess available runoff (water surplus) in Quilcene, just 30 miles south of the City, is
29.7 inches (Ecology 1981). This excess runoff in Quilcene is also reflected in local drainage patterns and
development of channels in the same glacial materials. As the amount of average annual precipitation
increases moving south from Port Townsend, the number of streams also increases to the south
(Ecology 1981).
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Figure 1Stormwater Drainage Basins
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TopographyFigure 3
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City Limits
2019 Stormwater Management Plan Page 2 - 6
Area GeologyFigure 5
Surficial Geologic Map of the PortTownsend 30- by 60-Minute Quad-rangle, Puget Sound Region,Washington by Fred Pessl, Jr., D.P.Dethier, D.B. Booth, and J.P. Minard1989
Qb: Beach DepositsQd: Dune DepositsQm: Marsh, Bog, or SwampQvrc: Recessional-ContinentalQvt: Vashon Till
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Figure 6
Annual Water Budget(Ecology 1981)
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Stormwater Management Plan
City of Port Townsend
January 2019│ 553-2836-004 2-9
2.2.3 Soils
Soils in the area were mapped by the Natural Resources Conservation Service (NRCS), as shown on
Figure 7. The NRCS divides soils into four hydrologic soil groups (HSG) defined by the expected rainfall
infiltration and runoff response. These soils categories provide information for hydrologic modeling and
planning-level information regarding localized infiltration potential (or lack thereof). These data will be
used for testing potential impacts described in Section 4 below. Figure 7 has highlighted HSG “A” and
HSG “D” which represents the soils most likely to have high infiltration and low infiltration respectively.
The hydrologic soil groups will be used to support on-site infiltration feasibility7.
2.3 Area Climate and Hydrology
2.3.1 Hydrology
Port Townsend is located in the rain shadow of the Olympic Mountains. The precipitation in the area
usually falls as rain, with about 65 percent of the yearly precipitation occurring between October and
March. Current hydrological parameters in the City are:
• Average annual rainfall: 17.64 inches
• Mean storm events: 50
• Mean storm depth1: 0.266 inches
1 Data from the Port Townsend Station located at latitude 48.07, longitude 122.45 (Perrich 1992).
Rainfall depths for selected 24-hour storm events are shown in Table 2-1.
Table 2-1. Rainfall Depths for 24-Hour Events 2
Return Frequency Precipitation Depth (inches)
2-year 1.17
10-year 1.72
25-year 2.03
100-year 2.50
2 Data taken from National Oceanic and Atmospheric Administration (NOAA), U.S. Department of Commerce (reference needed)
Hydrologic modeling is used to predict runoff from under different land use scenarios. Modeling for this
Plan was done using MGSFlood. The predicted runoff rates are used for sizing conveyance structures such
as culverts and ditches. Stormwater models use the long-term regional rainfall records which are tailored
to the specific location being analyzed (i.e., Port Townsend). The maximum adjustment in the rainfall
record allowed by Ecology is a factor of 0.78, which does not fully reflect the reduction needed when
comparing Port Townsend rainfall records to nearby stations used in the long-term model record.
Consequently, the modeled rainfall amounts used, and the resultant peak flow rates (described in
sections below), may be higher than observed amounts. Because of this, conveyance structures may be
larger than needed for the design storms used. However, the structure sizing is not that sensitive to
modest changes in rainfall extremes, therefore the overall effect on results is expected to be minor. Also,
the impact analysis is comparative, using the same rainfall record, which means the existing and future
conditions are similarly different (high or low) but the comparative difference is reasonably accurate.
The rational method is another appropriate approach for calculating peak flows in for conveyance
design. However, the rainfall intensity numbers used in the rational method also rely on location-specific
rainfall data. These data have not been calculated for Port Townsend and the available nearby rainfall
Stormwater Management Plan
City of Port Townsend
2-10 January 2019│ 553-2836-004
stations do not have the type of data or length of records needed to be appropriate data sources.
Similar adjustments can be made to nearby available rainfall data if this method is used but is also
expected to over-predict runoff rates.
2.4 Water Quality
No stormwater quality data has been collected by the City at city outfalls. The Jefferson County Health
Department collected dry and wet weather samples to evaluate e coli from storm sewer outfalls in 2013
and 2014. The samples can inform some elements of stormwater planning which would be focused on
education (usually pet waste), source controls, and illicit discharges. There is insufficient available data
to inform a basin or outfall-specific stormwater quality retrofit prioritization plan, which is the norm, not
the exception, in most of Puget Sound communities. However, stormwater is a presumptive practice;
therefore, a surrogate such as the percentage of roadways and intensity of development in a basin can
be used to prioritize locations for stormwater treatment retrofits to improve water quality.
2.5 Climate Change
Change in climate is expected to result in more extreme weather such as larger storms of greater
intensity, changes in seasonal rainfall patterns, more extreme difference between wet and dry years, or
changes in snow and snow melt patterns. In addition, warming weather is resulting in higher sea levels
which can impact coastal communities, such as Port Townsend.
Change in the global climate is expected to increase temperatures in western Washington 4.2⁰ F to
5.4⁰ F by 2050 in the Puget Sound Region and more extreme weather may be expected. For example,
according to a study done by University of Washington (Mauger et al. 2015), the wettest days
(99th percentile of 24-hour precipitation totals) in the Pacific Northwest are projected to increase in
precipitation by 22 percent by the 2080s and the frequency of those events are predicted to increase
from 2 days per year historically (1970-1999) to 7 days per year in the future (2070-2099). According to
some models, around the Puget Sound watershed and Port Townsend, the maximum 24-hour
precipitation event is projected to have an increase precipitation of 6 percent to 10 percent by 2040,
and 10 percent to 11.5 percent by 2080.
Precipitation in general is projected to increase in fall, winter and spring and decrease in summer.
Around the Puget Sound watershed and Port Townsend, it is projected that winter precipitation will
increase on average of 7 percent to 8.5 percent by 2040, while summer precipitation will decrease on
average by 10 percent to 11.5 percent. Additionally, the average snowpack is predicted to decline in the
Puget Sound region, causing the spring peak in streamflow to occur earlier in the year and decreasing
summer minimum flows.
In addition, warming weather is resulting in higher sea levels which can impact coastal communities
such as Port Townsend. Based on a University of Washington study on projected sea level rise
(Miller et al. 2018), around Port Townsend there is a 99 percent probability that relative sea level (RSL)
will increase by 0.1 feet by 2030 and a 50 percent probability that RSL will increase by 0.4 feet. By 2070,
that increases to a 99 percent probability that the RSL will rise by 0.4 feet and 50 percent probability of
over 1.3 feet. These projections all assume high greenhouse gas scenario. In a low greenhouse gas
scenario, the projections remain the same for 2030, and decrease slightly to a 99 percent probability of
RSL rises by 0.3 feet and 50 percent probability of over 1.1 feet in 2070. Looking farther ahead, in 2150
there is a 99 percent probability that RSL will increase by 0.3 feet and 50 percent probability that RSL
will increase by 2.8 feet. Furthermore, in the event of a subduction zone earthquake, some parts of
Washington coast may be subject to land level changes, based on multiple seismic deformation models,
of 0 to 0.3 feet subduction.
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A - Low
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Variable
Hydrologic Soil Groups per 2005Stormwater Management Manualfor Western Washington
Runoff Potential
Drainage Basins
Cut and Fill, Rough Broken,Water, Reservoir
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City Limits
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2019 Stormwater Management Plan Page 2 - 11
Stormwater Management Plan
City of Port Townsend
January 2019│ 553-2836-004 3-1
3. THE BUILT ENVIRONMENT
Stormwater plans are prepared to address both current and proposed conditions: the effects of land
conversion on stream hydrology and the impacts of pollution-generating activities on water quality.
Land drainage has been included in design for centuries; stormwater management has been the norm
for the past several decades in Washington and continues to evolve as the practice learns from the past
and new issues come to the forefront. Existing land use and land cover have created drainage conditions
observed today, including some localized flooding and erosion impacts. Development of vacant
undeveloped lands, redevelopment, and infill will bring future potential impacts, if not properly
controlled. The measures and standards for control to be used in Port Townsend will follow the general
approach for stormwater management used elsewhere in western Washington, with adjustments due to
local conditions found in Port Townsend.
As described before, the City will be unique in its approach to addressing stormwater management
because of the following unique local conditions: there are no natural streams but there are obvious
pathways, drainage basins, and receiving waters; new development will be predominantly infill into pre-
platted areas with or without existing opened rights-of-way; rainfall is relatively low; and the road
system is the dominant drainage conveyance network.
In this section, existing land use (as defined by imperviousness) is estimated to evaluate existing
drainage needs, primarily in the road system, and identify areas with potentially high stormwater quality
impacts. There are no reliable mapped data for determining existing imperviousness, therefore
estimates were made using approaches described below. Future land use is estimated by both the
development potential and estimated allowable development. This generally tends to over predict
future impacts, which means the planning outcomes tend to be reliably protective.
Runoff modeling requires soils and land cover data. Figure 7 provides the source for soils data. Land
cover refers to the general type and condition of vegetated surfaces, such as forests, pastures, and open
landscapes, each of which has a different runoff response to precipitation. The City used visual
estimates for land cover data. In low precipitation areas with moderate soil runoff response such as Port
Townsend, runoff rates are relatively insensitive to land cover.
In addition, for purposes of hydrologic modeling, each drainage basin in the City was further divided into
subbasins, referred to as “catchment” areas as shown on Figure 8. The catchment boundaries are
defined by both topography and the built environment—existing roads and stormwater infrastructure.
3.1 Land Use
An inventory of impervious area and land cover, described in terms of aerial coverage within a
catchment, is needed to prepare modeling or characterization analyses that relate runoff potential or
quality characteristics to a point in the conveyance system. Impervious land cover can include amounts
and types of impervious surface, for example roads, sidewalks, rooftops, or parking lots, or a stormwater
management description like pollution generating or “effective” impervious surface. Available data to
make these characterizations varies widely between different jurisdictions. Fortunately, there are a
number of approaches to either translate available data into categories that are useful for stormwater
management or basin planning evaluations. Data are needed to characterize existing conditions and to
project the changes that could occur due to new development.
Stormwater Management Plan
City of Port Townsend
3-2 January 2019│ 553-2836-004
3.1.1 Existing Land Cover
Existing land use and imperviousness is estimated to evaluate existing conditions to determine drainage
needs, primarily in the road system, identify areas with potentially high stormwater quality impacts, and
provide a baseline for modeling existing runoff conditions. For the modeling analysis, imperviousness is
calculated for each catchment within a drainage basin. The approach for estimating existing
imperviousness is described below.
For rights-of-way, two categories were identified: opened rights-of-way (which means an existing public
road is present) and unopened rights-of-way (an undeveloped, platted right-of-way with no public road).
For opened rights-of-way, the length of roadways in the catchments were measured and multiplied by
22-feet to estimate the area of impervious surface. The right-of-way per catchment is shown in Table 3-
1. The opened rights-of-way are an estimated 40 percent imperviousness based on a typical roadway
width of 22-feet of pavement in a 60-foot wide platted right-of-way, plus some consideration of
sidewalks and driveways in the right-of-way. For unopened rights-of-way, imperviousness is assumed to
be zero.
The remaining land (i.e., not platted rights-of-way) was classified into developed land, critical areas
(undevelopable land including steep slopes, wetlands, and CDCs), or vacant land. For developed land,
the estimated imperviousness is 37 percent of the developed land area. Vacant land was further divided
into conservation or public lands (which are assumed will remain undeveloped) underdeveloped land
(which are large tracts with little development or a single house) and undeveloped (developable land
either platted land or not). For vacant land, the estimated imperviousness was assumed to be zero for
current baseline conditions.
Runoff modeling requires land cover data and soils types. Land cover refers to the general type and
condition of vegetated surfaces, such as forests, pastures, and open landscapes, each of which has a
different runoff response to precipitation. Visual estimates were used to provide data for land cover. In
low precipitation areas with moderate soil runoff response such as Port Townsend, runoff rates are
relatively insensitive to land cover. Figure 7 provides the source for soils data. Tables 3-1 and 3-2
provides a breakdown of total catchment area breakdown (see Figure 8), rights-of-way impervious area,
rights-of-way unopened area, developed area, critical areas, vacant conservation/public land and vacant
underdeveloped/developable land.
Table 3-1. Existing Land Cover
Catchment
Total
Area
(ac.)
Remaining Land
Right-of-Way Vacant
Open
(ac.)
Unopened
(ac.)
Developed
(ac.)
Critical Areas
(ac.) Conservation/public
Underdeveloped/
Developable
1 12.8 0.0 0.0 0.0 12.8 0.0 0.0
2 62.7 13.7 4.8 15.1 2.0 24.1 3.4
3 19.1 0.0 0.0 0.0 10.9 0.0 8.1
4a 46.5 0.0 0.0 0.0 46.5 0.0 0.0
4b 80.3 0.1 0.2 0.9 7.1 0.8 71.2
4c 122.4 15.0 4.2 7.4 8.9 21.9 65.0
4d 47.4 0.1 0.0 0.0 8.6 0.1 38.6
4e 26.7 4.6 1.0 5.2 1.5 7.9 6.7
4f 83.7 8.5 2.3 13.3 6.3 52.5 1.0
4g 107.6 17.5 15.2 27.6 19.8 25.4 2.2
Stormwater Management Plan
City of Port Townsend
Table 3-1. Existing Land Cover (continued)
January 2019│ 553-2836-004 3-3
Catchment
Total
Area
(ac.)
Remaining Land
Right-of-Way Vacant
Open
(ac.)
Unopened
(ac.)
Developed
(ac.)
Critical Areas
(ac.) Conservation/public
Underdeveloped/
Developable
4h 46.4 2.8 4.2 8.2 3.0 1.2 27.0
4i 114.2 7.2 26.8 43.3 11.3 9.9 15.7
4j 38.0 2.3 0.2 33.5 2.0 0.0 0.0
4k 129.9 13.9 24.1 66.3 11.2 13.6 0.8
4l 314.8 22.9 45.7 160.2 37.3 25.6 23.2
4m 38.4 3.7 8.6 16.3 1.7 8.1 0.0
5a 85.7 1.5 14.0 65.5 1.2 1.7 1.9
5b 54.8 2.6 1.9 17.8 9.5 23.0 0.0
5c 36.9 3.1 4.3 8.0 9.5 4.7 7.3
5d 61.4 1.8 17.9 34.4 2.4 1.8 3.1
6a 80.4 18.4 6.7 25.0 2.9 26.9 0.5
6b 14.6 3.6 1.3 5.7 0.0 4.0 0.0
6c 5.8 0.9 1.0 0.3 1.2 2.3 0.0
7a 19.6 3.4 2.0 4.6 3.1 6.4 0.0
7b 7.4 0.0 0.0 0.2 0.0 7.2 0.0
7c 48.5 16.5 3.1 5.8 0.7 22.4 0.0
7d 26.0 7.1 1.0 3.9 1.6 11.0 1.3
7e 18.8 1.4 0.5 13.0 0.1 3.9 0.0
7f 6.6 0.1 0.0 4.9 0.9 0.6 0.0
8a 70.8 13.7 4.2 11.7 0.9 40.1 0.2
8b 107.3 14.2 3.6 14.3 9.6 37.8 27.9
8c 61.9 12.3 6.3 18.4 3.3 21.2 0.5
8d 8.0 3.4 0.3 1.9 0.2 2.2 0.0
8e 2.7 0.6 0.0 1.1 0.0 0.9 0.0
8f 31.9 9.6 4.5 4.0 0.0 13.8 0.0
8g 13.9 3.1 0.9 3.3 0.2 5.6 0.8
8h 5.7 0.3 0.1 4.4 0.0 0.9 0.0
8i 50.6 4.7 8.3 30.1 0.4 6.6 0.4
8j 18.4 4.3 2.0 7.4 0.5 4.2 0.0
8k 32.6 2.8 4.3 13.8 8.4 3.0 0.2
9a 46.4 0.0 0.0 0.0 46.4 0.0 0.0
9b 137.7 34.6 16.2 33.5 1.3 52.0 0.0
9c 30.5 8.6 3.3 5.0 1.0 12.4 0.1
9d 39.0 13.6 1.0 2.0 0.1 22.2 0.0
9e 13.8 5.8 1.1 0.8 1.7 3.4 1.7
9f 108.8 24.2 16.3 11.5 7.7 35.2 21.4
9g 26.2 0.4 0.0 0.0 0.0 0.0 25.7
9h 39.9 7.4 0.5 6.6 0.0 25.4 0.0
9i 25.1 7.2 2.3 2.9 0.0 12.4 0.2
9j 99.6 16.3 6.3 35.0 13.2 28.7 0.0
9k 15.9 3.3 1.2 1.4 0.0 10.0 0.0
9l 49.3 16.4 4.1 10.4 0.2 18.2 0.0
Stormwater Management Plan
City of Port Townsend
Table 3-1. Existing Land Cover (continued)
3-4 January 2019│ 553-2836-004
Catchment
Total
Area
(ac.)
Remaining Land
Right-of-Way Vacant
Open
(ac.)
Unopened
(ac.)
Developed
(ac.)
Critical Areas
(ac.) Conservation/public
Underdeveloped/
Developable
9m 17.1 7.0 0.1 0.8 0.2 9.1 0.0
10a 103.9 24.7 6.3 15.1 12.0 45.7 0.1
10b 23.5 3.9 0.7 5.3 3.8 9.8 0.0
10c 51.0 2.2 1.3 0.0 1.0 46.5 0.0
10d 21.4 5.2 0.8 0.0 0.3 15.1 0.0
11a 72.1 2.0 9.8 41.2 14.9 3.5 0.7
11b 76.7 17.8 6.5 10.4 5.4 33.6 3.0
11c 28.8 5.5 1.5 7.4 6.8 7.7 0.0
11d 3.7 0.0 0.0 0.0 3.7 0.0 0.0
11e 26.7 4.4 1.5 4.7 9.3 6.2 0.6
11f 33.6 6.3 2.7 10.3 1.4 12.9 0.0
12a 86.6 32.9 3.8 4.4 2.0 43.5 0.1
12b 20.1 4.3 1.2 0.5 3.1 10.5 0.4
12c 26.9 10.9 0.5 0.4 1.6 13.4 0.1
12d 30.8 13.0 0.4 2.1 1.2 13.4 0.7
12e 13.5 3.6 0.4 0.6 1.3 6.7 0.9
12f 112.2 38.6 0.7 9.5 1.6 57.2 4.6
12g 14.3 2.0 0.1 1.3 0.5 10.5 0.0
13a 44.8 5.4 0.8 3.4 2.1 30.0 3.1
13b 51.9 15.9 1.1 4.1 1.6 24.5 4.6
13c 18.8 0.6 0.8 1.8 10.7 4.4 0.5
14 193.6 10.3 4.9 11.6 21.9 13.0 131.8
15a 131.7 5.1 7.8 77.8 30.1 10.9 0.0
15b 24.6 4.0 1.3 13.8 0.6 4.4 0.6
15c 24.0 1.3 0.3 12.0 2.3 4.2 3.8
16a 42.9 6.7 5.8 14.5 6.1 9.3 0.5
16b 62.7 8.3 5.4 22.5 6.6 19.9 0.0
16c 7.5 1.6 1.1 0.9 0.1 3.7 0.0
17a 53.7 7.0 5.5 34.1 0.7 6.4 0.0
17b 46.4 5.8 1.2 15.7 6.4 16.4 0.9
18a 141.6 5.0 4.4 105.0 15.1 12.1 0.0
18b 84.6 2.9 7.7 61.8 9.4 0.3 2.7
Table 3-2. Existing Land Use Model Inputs
Catchment
Total Area
(ac.)
Impervious
(ac.)
Percent
Impervious
Pervious (ac.)
Hydrologic Soil
Type A - Forest
Hydrologic Soil
Type C - Forest
Hydrologic Soil
Type D - Forest
1 12.8 0.00 0.0% 11.5 1.3 0.0
2 62.7 11.1 17.7% 35.1 16.5 0.0
3 19.1 0.01 0.1% 19.0 0.00 0.0
4a 46.5 0.00 0.0% 2.1 2.1 42.3
Stormwater Management Plan
City of Port Townsend
Table 3-2. Existing Land Use Model Inputs (continued)
January 2019│ 553-2836-004 3-5
Catchment
Total Area
(ac.)
Impervious
(ac.)
Percent
Impervious
Pervious (ac.)
Hydrologic Soil
Type A - Forest
Hydrologic Soil
Type C - Forest
Hydrologic Soil
Type D - Forest
4b 80.3 0.3 0.3% 66.8 11.80 1.4
4c 122.4 18.2 14.8% 47.9 53.35 2.9
4d 47.4 0.2 0.4% 16.3 22.0 8.9
4e 26.7 3.7 13.7% 17.7 3.6 1.8
4f 83.7 10.4 12.4% 40.1 32.5 0.8
4g 107.6 13.8 12.8% 27.1 66.7 0.0
4h 46.4 1.2 2.5% 32.8 12.4 0.0
4i 114.2 5.4 4.7% 87.3 21.6 0.0
4j 38.0 1.9 4.9% 10.7 25.5 0.0
4k 129.9 7.5 5.8% 107.1 15.3 0.0
4l 314.8 15.1 4.8% 274.0 0.0 25.8
4m 38.4 2.8 7.3% 14.7 20.9 0.0
5a 85.7 1.0 1.2% 30.5 54.3 0.0
5b 54.8 4.3 7.9% 12.5 38.0 0.0
5c 36.9 2.7 7.4% 20.6 10.1 3.5
5d 61.4 1.3 2.1% 23.8 36.4 0.0
6a 80.4 13.8 17.2% 33.9 32.7 0.0
6b 14.6 2.3 16.0% 5.6 6.7 0.0
6c 5.8 0.9 14.7% 0.0 5.0 0.0
7a 19.6 2.5 12.9% 13.7 3.3 0.0
7b 7.4 1.5 20.2% 0.0 5.9 0.0
7c 48.5 11.5 23.7% 26.4 10.6 0.0
7d 26.0 5.6 21.5% 8.7 12.1 0.0
7e 18.8 1.5 8.1% 4.6 12.7 0.0
7f 6.6 0.2 3.1% 0.0 6.4 0.0
8a 70.8 10.5 14.9% 60.1 0.2 0.0
8b 107.3 11.0 10.3% 42.2 54.1 0.0
8c 61.9 10.2 16.4% 42.4 9.4 0.0
8d 8.0 2.1 26.6% 3.7 2.1 0.0
8e 2.7 0.6 21.4% 0.0 2.1 0.0
8f 31.9 6.0 18.7% 22.3 3.6 0.0
8g 13.9 2.1 15.0% 0.4 11.5 0.0
8h 5.7 1.2 21.4% 0.0 4.5 0.0
8i 50.6 3.6 7.1% 0.0 47.1 0.0
8j 18.4 3.6 19.7% 14.8 0.0 0.0
8k 32.6 2.1 6.5% 30.2 0.0 0.3
9a 46.4 0.0 0.0% 0.0 5.5 40.9
9b 137.7 23.5 17.1% 102.6 11.6 0.0
9c 30.5 5.6 18.3% 22.7 2.2 0.0
9d 39.0 9.4 24.2% 25.6 4.0 0.0
9e 13.8 3.2 23.1% 3.5 7.1 0.0
9f 108.8 16.1 14.8% 46.4 44.8 1.5
9g 26.2 7.2 27.6% 8.0 11.0 0.0
Stormwater Management Plan
City of Port Townsend
Table 3-2. Existing Land Use Model Inputs (continued)
3-6 January 2019│ 553-2836-004
Catchment
Total Area
(ac.)
Impervious
(ac.)
Percent
Impervious
Pervious (ac.)
Hydrologic Soil
Type A - Forest
Hydrologic Soil
Type C - Forest
Hydrologic Soil
Type D - Forest
9h 39.9 6.6 16.6% 33.3 0.0 0.0
9i 25.1 8.3 32.9% 0.0 16.9 0.0
9j 99.6 9.5 9.5% 90.2 0.0 0.0
9k 15.9 6.3 39.2% 9.5 0.2 0.0
9l 49.3 9.0 18.2% 19.8 20.5 0.0
9m 17.1 13.3 77.9% 3.5 0.3 0.0
10a 103.9 11.5 11.0% 91.5 1.0 0.0
10b 23.5 4.6 19.7% 9.2 9.7 0.0
10c 51.0 6.1 12.0% 44.9 0.0 0.0
10d 21.4 2.3 10.7% 19.1 0.0 0.0
11a 72.1 9.6 13.3% 62.4 0.0 0.0
11b 76.7 8.6 11.2% 68.1 0.0 0.0
11c 28.8 2.9 10.0% 25.9 0.0 0.0
11d 3.7 1.1 30.6% 2.6 0.0 0.0
11e 26.7 6.0 22.3% 20.6 0.2 0.0
11f 33.6 13.7 40.9% 19.6 0.3 0.0
12a 86.6 15.5 17.9% 68.4 2.7 0.0
12b 20.1 6.1 30.3% 14.0 0.0 0.0
12c 26.9 8.1 30.0% 18.8 0.0 0.0
12d 30.8 6.0 19.5% 24.8 0.0 0.0
12e 13.5 15.21 112.7%1 -1.72 0.0 0.0
12f 112.2 17.5 15.6% 90.7 4.1 0.0
12g 14.3 5.5 38.6% 3.7 5.2 0.0
13a 44.8 9.3 20.7% 35.5 0.0 0.0
13b 51.9 8.1 15.5% 43.9 0.0 0.0
13c 18.8 6.0 32.0% 12.5 0.3 0.0
14.00 193.6 12.2 6.3% 161.7 19.7 0.0
15a 131.7 3.2 2.4% 102.4 25.3 0.8
15b 24.6 2.8 11.2% 15.3 6.6 0.0
15c 24.0 2.6 10.7% 12.5 9.0 0.0
16a 42.9 8.6 20.0% 34.3 0.0 0.0
16b 62.7 4.0 6.4% 58.7 0.0 0.0
16c 7.5 2.4 32.1% 5.1 0.0 0.0
17a 53.7 6.8 12.7% 46.9 0.0 0.0
17b 46.4 5.6 12.0% 40.8 0.0 0.0
18a 141.6 2.6 1.8% 119.8 19.2 0.0
18b 84.6 1.6 1.9% 83.0 0.0 0.0
1 The approach used to calculate existing impervious area resulted in an area larger than the basin. These numbers were adjusted to show the maximum area
possible.
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Glaspell
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11a
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Figure 8Drainage Catchment Areas
0 0.25 0.5 0.75 1
Miles
5a
Drainage Basins
Catchments
Potential Wetlands
Wetlands
(19
City Limits
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2019 Stormwater Management Plan Page 3 - 7
Stormwater Management Plan
City of Port Townsend
January 2019│ 553-2836-004 3-9
3.1.2 Future Land Use and Land Cover
Existing land use, as described above, is used in runoff models to evaluate existing drainage conditions
and needs and identify areas with potential stormwater impacts. Future land use, mainly in the form of
new impervious surfaces and converted land cover, is used to predict future potential runoff impacts.
Future potential impact areas are the focus of the SMP.
The unopened rights-of-way and the “developable land” categories are where the potential runoff
changes will occur. For planning purposes, potential land conversion estimates are made for full build-
out to predict where impacts could occur which then point to the need for measures to minimize or
manage those impacts.
For unopened rights-of-way, the total potential conversion of land area is estimated to be 40 percent
impervious, following the assumption used for existing opened rights-of-way in Section 3.1.1. Some of
the unopened rights-of-way are located adjacent to public and conservation lands and may never be
opened, resulting in an over-estimation of future imperviousness, thus the modeling results can be
considered conservative.
For vacant land, public and conservation lands are expected to remain pervious and undeveloped.
Underdeveloped and remaining developable lands are assumed to be developed to their full, allowable
potential. The estimated future fully developed impervious percentage is 37 percent, which was
provided by City staff to use in runoff modeling. This is a typical approach in stormwater planning,
although it has been found to overpredict actual development that occurs.
Larger tracts that will construct new roads within new rights-of-way use an estimate of 37 percent
future impervious (which is the same percent used for future developable land), while existing
unopened rights-of-way will use 40 percent imperviousness. The 3 percent difference is small and is not
expected to result in significantly different modeling outcomes.
Land cover conversion will assume that the remaining uncovered pervious lands will be “pasture” (which
includes lawns and non-forested open spaces; this is a modeling convention term) and or remain in part
forest. The land cover is visually estimated from recent aerial photos. For the model it will be assumed
that 50 percent of the forest in developable land will convert to pasture, and that pasture will remain
pasture.
The potential development and conversion to impervious surfaces described here are used to model
and predict the highest potential for future impacts to the natural drainage ways, drainage systems, and
existing wetlands. However, the reality is that runoff would be controlled to some extent at each site,
with full control following the stormwater manual at larger sites and to the maximum extent practicable
at small sites or individual platted lots. The amount of control or runoff reduction is catchment-specific,
considering soils conditions and developable tract types. In the modeling results, if the potential for
future impacts is found or exceeds thresholds, a closer catchment-specific analysis and adjustment may
be made if the conservative assumptions (developable and underdeveloped lands developed to their
full, allowable potential with no stormwater controls) result in an impact. Catchments that still could
have impacts after these adjustments are applied may become candidates for regional control facilities.
Existing Land Use is shown on Figure 9. Vacant lands and development potential are shown in Figure 10.
Soils mapping and potential for good infiltration conditions are shown in Figure 7. Using this
information, the estimates for future conditions for full buildout for the MGSFlood model are shown in
Table 3-3.
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ChineseGardens
HastingsPond
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BuckmansLake
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Figure 9Land-Use
0 0.25 0.5 0.75 1
Miles
Wetlands
Potential Wetlands
Drainage Basins
Residential Districts
Mixed Use Districts
C-II/MU Community Mixed Use
C-I/MU Neighborhood Mixed Use
C-I Neighborhood Commercial
C-II General Commercial
C-II(H) Hospital Commercial
C-III Historic Commercial
Commercial Districts
M-C Commercial / Light Manufacturing
M-II(A) Marine Related Uses
M-II(B) Marine Related Uses
Marine-Related and Manufacturing Districts
P-I Public / Infrastructure
P/OS Existing Park or Open Space
Public, Park and Open Space Districts
P/OS(B) Public / Mixed Use
R-I Min. 10,000 sq. ft. lot
R-II Min. 5,000 sq. ft. lot
R-III 10 to 16 d.u per 40,000 s.f.
R-IV 15 to 24 d.u per 40,000 s.f.
Wetlands and Stormwater Basins
(19
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2019 Stormwater Management Plan Page 3 - 11
((
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Kah Tai Lagoon
ChineseGardens
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LevinskiWetland
UmatillaAve.
BlueHeron
BuckmansLake
Glaspell
2 3
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Vacant Lands &Development Potential
Figure 10
0 0.25 0.5 0.75 1
Miles
Vacant & UnderdevelopedResidential Properties
Parks, Open-Space, &Cemeteries
Land Trust Properties
Slopes > 40%
Catchments
Developed Land
Development
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Potential Wetlands
Wetlands
Features
Critical Drainage Corridors
Key Drainageways
100 Year Flood
City Limits
Drainage Basins(19
2019 Stormwater Management Plan Page 3 - 12
Stormwater Management Plan
City of Port Townsend
3-13 January 2019│ 553-2836-004
Table 3-3. Future Land Use Model Inputs
Catchment
Total Area
(ac.)
Impervious
(ac.)
Percent
Impervious
Pervious (ac.)
Hydrologic Soil
Type A - Forest
Hydrologic Soil
Type C - Forest
Hydrologic Soil
Type D - Forest
1 12.8 0.1 7.6% 10.6 1.2 0.0
2 62.7 27.7 44.2% 23.8 11.2 0.0
3 19.1 0.00 0.1% 19.0 0.0 0.0
4a 46.5 0.1 0.3% 2.1 2.1 42.2
4b 80.3 0.1 1.2% 66.2 11.7 1.4
4c 122.4 30.7 25.1% 42.2 46.9 2.6
4d 47.4 0.2 0.5% 16.3 21.1 8.9
4e 26.7 8.9 33.3% 13.7 2.8 1.4
4f 83.7 35.8 42.8% 26.2 21.2 0.5
4g 107.6 41.6 38.7% 19.1 46.9 0.0
4h 46.4 6.3 13.7% 29.1 10.1 0.0
4i 114.2 36.5 31.9% 62.4 15.4 0.0
4j 38.0 14.4 37.7% 7.0 16.7 0.0
4k 129.9 48.1 37.0% 71.6 10.2 0.00
4l 314.8 106.8 33.9% 190.2 0.0 17.9
4m 38.4 15.3 39.8% 9.5 13.6 0.0
5a 85.7 31.5 36.8% 19.5 34.7 0.0
5b 54.8 20.2 36.8% 8.6 26.0 0.0
5c 36.9 9.9 26.8% 16.3 7.1 2.8
5d 61.4 21.1 35.8% 15.6 23.9 0.0
6a 80.4 35.1 44.7% 22.6 21.9 0.0
6b 14.6 6.4 44.1% 3.8 4.4 0.0
6c 5.8 2.4 40.5% 0.0 3.5 0.0
7a 19.6 7.6 38.9% 9.6 2.3 0.0
7b 7.4 4.2 57.1% 0.0 3.2 0.0
7c 48.5 23.2 47.9% 18.0 7.3 0.0
7d 26.0 11.5 44.4% 5.8 8.6 0.0
7e 18.8 7.7 42.3% 2.9 8.0 0.0
7f 6.6 2.3 34.3% 0.0 4.3 0.0
8a 70.8 31.4 44.3% 39.3 0.2 0.0
8b 107.3 32.1 29.9% 32.1 42.3 0.0
8c 61.9 27.5 44.4% 28.2 6.3 0.0
8d 8.0 3.8 47.4% 2.7 1.5 0.0
8e 2.7 1.3 49.7% 0.0 1.4 0.0
8f 31.9 14.4 45.0% 15.1 2.5 0.0
Stormwater Management Plan
City of Port Townsend
Table 3-3. Future Land Use Model Inputs (continued)
3-14 January 2019│ 553-2836-004
Catchment
Total Area
(ac.)
Impervious
(ac.)
Percent
Impervious
Pervious (ac.)
Hydrologic Soil
Type A - Forest
Hydrologic Soil
Type C - Forest
Hydrologic Soil
Type D - Forest
8g 13.9 5.8 41.5% 0.3 7.9 0.0
8h 5.7 3.2 56.2% 0.0 2.5 0.0
8i 50.6 20.5 40.5% 0.0 30.1 0.0
8j 18.4 8.8 47.7% 9.6 0.0 0.0
8k 32.6 10.5 32.1% 21.9 0.0 0.2
9a 46.4 1.9 4.1% 0.0 5.3 39.2
9b 137.7 61.6 44.8% 68.3 7.7 0.0
9c 30.5 13.6 44.5% 15.5 1.5 0.0
9d 39.0 18.8 48.3% 17.5 2.7 0.0
9e 13.8 5.3 38.6% 2.8 5.7 0.0
9f 108.8 41.2 37.9% 33.9 32.7 1.1
9g 26.2 7.2 27.7% 7.1 10.1 0.0
9h 39.9 18.7 46.8% 21.2 0.0 0.0
9i 25.1 14.9 59.2% 0.0 10.2 0.0
9j 99.6 36.1 36.2% 63.6 0.0 0.0
9k 15.9 10.9 68.7% 4.9 0.1 0.0
9l 49.3 21.2 43.0% 13.8 14.3 0.0
9m 17.1 17.0 99.5% 0.1 0.0 0.0
10a 103.9 37.3 35.9% 65.9 0.7 0.0
10b 23.5 10.5 44.6% 6.3 6.7 0.0
10c 51.0 23.9 46.8% 27.2 0.0 0.0
10d 21.4 8.2 38.4% 13.2 0.0 0.0
11a 72.1 31.4 43.6% 40.6 0.0 0.0
11b 76.7 27.8 36.2% 48.9 0.0 0.0
11c 28.8 9.4 32.7% 19.4 0.0 0.0
11d 3.7 1.2 30.7% 2.6 0.0 0.0
11e 26.7 11.5 42.9% 15.2 0.2 0.0
11f 33.6 23.4 69.7% 10.1 0.2 0.0
12a 86.6 34.9 40.3% 49.7 1.1 0.0
12b 20.1 10.9 54.1% 9.2 0.0 0.0
12c 26.9 13.5 50.3% 13.3 0.0 0.0
12d 30.8 11.1 38.8% 18.8 0.0 0.0
12e 13.5 13.5 100.0% 0.0 0.0 0.0
12f 112.2 42.5 37.9% 66.7 3.0 0.0
12g 14.3 9.9 69.1% 1.8 2.6 0.0
13a 44.8 22.2 49.5% 22.7 0.0 0.0
13b 51.9 19.1 36.8% 32.8 0.0 0.0
Stormwater Management Plan
City of Port Townsend
Table 3-3. Future Land Use Model Inputs (continued)
January 2019│ 553-2836-004 3-15
Catchment
Total Area
(ac.)
Impervious
(ac.)
Percent
Impervious
Pervious (ac.)
Hydrologic Soil
Type A - Forest
Hydrologic Soil
Type C - Forest
Hydrologic Soil
Type D - Forest
13c 18.8 9.9 52.6% 8.7 0.2 0.0
14.00 193.6 23.6 12.2% 151.5 18.5 0.0
15a 131.7 40.3 30.6% 72.8 17.1 0.6
15b 24.6 10.1 40.9% 10.2 4.4 0.0
15c 24.0 8.7 36.2% 8.9 6.4 0.0
16a 42.9 20.3 47.1% 22.7 0.0 0.0
16b 62.7 22.1 35.2% 40.6 0.0 0.0
16c 7.5 4.6 61.2% 2.9 0.0 0.0
17a 53.7 24.1 44.9% 29.6 0.0 0.0
17b 46.4 18.0 38.9% 28.3 0.0 0.0
18a 141.6 47.7 33.7% 80.9 13.0 0.0
18b 84.6 28.1 33.2% 56.5 0.0 0.0
3.1.3 Estimating Runoff Potential
As described in previous sections, the City has: low rainfall depth and intensity when compared to
elsewhere in western Washington, areas of relatively low runoff soils and land cover, and small
catchments with poorly defined natural drainage paths. These factors converge to result in a relatively
narrow range of peak flow rates, which often means that similar drainage infrastructure is needed in
many different locations. Modeling the entire system would be costly; a generalized modeling approach
can address much of the City’s system need. To define this need and confirm the expectation that
similar runoff results can be found across the city, some generalized runoff modeling was performed.
The land cover conversion analysis results, previously described in this section, are input into the
hydrologic model to find future peak runoff potential from the basin. The location at which this peak
flow rate occurs is described as “key locations” in the drainage system. In some catchments, the peak
flow rate is the entire runoff potential from the catchment, with no specific geographic location. An
example would be in Catchment 1, which has runoff that generally flows toward the Strait of Juan de
Fuca and discharges at multiple points. In the catchments where there is a defined location at which all
of the runoff is directed, a “node” is defined as the specific location of the calculated peak flow rate, as
shown on Figure 11. Table 3-4 lists the catchment area name, total catchment area in acres, percentage
of existing and future impervious area, and distribution of land cover.
Existing and future peak runoff for the 2-, 10-, 25-, and 100-year events were determined at the
catchment nodes shown on Figure 11 (unless there is no node, which means that the peak runoff rate is
total runoff potential from the entire basin). These modeling results will be used to define potentially
impacted areas. The future peak flows for the 25-year event will be used to assess drainage conveyance
needs in the roadway system, notably where the road drainage becomes the main flow path in the
basin. The 25-year peak flows will be used to assess potential impacts from future development to CDCs
and KDs as defined in Section 4. A comparison between existing (Table 3-5a) and future (Table 3-5b)
conditions for selected events (2-, 10-, 25-, and 100-year storm events) is also used to assess wetland
receiving waters, notably in Basins 4 through 9. The peak runoff modeling results for Existing and Future
Conditions are shown in Tables 3-5a and Table 3-5b, respectively.
Kah Tai Lagoon
ChineseGardens
HastingsPond
WinonaWetland
Tibbal'sLake
FroggyBottoms
LevinskiWetland
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Admiralty Inlet
BlueHeron
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Figure 11Catchment Nodes
0 0.25 0.5 0.75 1
Miles
Catchment Nodes
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9
Potential Wetlands
Wetlands
Features
Critical Drainage Corridors
Key Drainageways
100 Year Flood
City Limits
Catchments19
2019 Stormwater Management Plan Page 3 - 17
Stormwater Management Plan
City of Port Townsend
January 2019│ 553-2836-004 3-19
Table 3-4. Buildable Area – Impervious Comparison
Catchment
Total Area
(ac.)
Existing Impervious (ac.) Future Impervious (ac.)
ROW
Buildable
Area
Total Impervious
Percent ROW
Buildable
Area
Total Impervious
Percent
1 12.8 0.0 0.0 0.0% 1.0 0.0 7.6%
2 62.7 13.7 5.6 30.7% 15.8 20.0 57.2%
3 19.1 0.0 0.0 0.1% 0.0 0.0 0.1%
4a 46.5 0.0 0.0 0.0% 0.1 0.0 0.3%
4b 80.3 0.1 0.3 0.5% 0.2 0.9 1.3%
4c 122.4 15.0 7.8 18.7% 16.7 18.6 28.9%
4d 47.4 0.1 0.1 0.4% 0.1 0.1 0.5%
4e 26.7 4.6 1.6 23.2% 5.0 6.4 42.7%
4f 83.7 8.5 6.1 17.4% 9.6 30.4 47.7%
4g 107.6 17.5 5.7 21.5% 25.7 25.3 47.3%
4h 46.4 2.8 0.3 6.6% 4.5 3.7 17.7%
4i 114.2 7.2 2.6 8.6% 18.6 22.3 35.8%
4j 38.0 2.3 0.6 7.8% 2.4 13.0 40.7%
4k 129.9 13.9 1.7 12.0% 24.9 31.3 43.2%
4l 314.8 22.9 5.6 9.1% 45.8 74.4 38.2%
4m 38.4 3.7 1.3 12.9% 7.2 10.3 45.4%
5a 85.7 1.5 0.3 2.1% 7.2 25.2 37.7%
5b 54.8 2.6 2.8 9.9% 3.4 17.9 38.8%
5c 36.9 3.1 1.4 12.1% 5.5 6.1 31.5%
5d 61.4 1.8 0.4 3.6% 9.1 13.8 37.3%
6a 80.4 18.4 6.3 30.6% 21.3 25.5 58.1%
6b 14.6 3.6 1.2 32.8% 4.2 4.7 60.8%
6c 5.8 0.9 0.5 23.2% 1.4 1.4 48.9%
7a 19.6 3.4 1.1 23.2% 4.4 5.2 49.2%
7b 7.4 0.0 1.1 15.5% 0.0 3.9 52.4%
7c 48.5 16.5 4.6 43.4% 17.8 15.0 67.6%
7d 26.0 7.1 2.5 36.6% 7.5 8.0 59.6%
7e 18.8 1.4 1.0 12.8% 1.6 7.2 47.0%
7f 6.6 0.1 0.2 4.2% 0.1 2.2 35.4%
8a 70.8 13.7 4.4 25.6% 15.4 23.6 55.0%
8b 107.3 14.2 5.9 18.7% 16.0 25.1 38.3%
8c 61.9 12.3 4.2 26.6% 14.9 18.9 54.6%
8d 8.0 3.4 0.5 48.0% 3.5 2.0 68.8%
8e 2.7 0.6 0.3 35.8% 0.6 1.1 64.1%
8f 31.9 9.6 2.6 38.3% 11.4 9.2 64.6%
Stormwater Management Plan
City of Port Townsend
Table 3-4. Buildable Area – Impervious Comparison (continued)
3-20 January 2019│ 553-2836-004
Catchment
Total Area
(ac.)
Existing Impervious (ac.) Future Impervious (ac.)
ROW
Buildable
Area
Total Impervious
Percent ROW
Buildable
Area
Total Impervious
Percent
8g 13.9 3.1 1.1 29.9% 3.5 4.4 56.5%
8h 5.7 0.3 1.1 25.2% 0.4 3.1 60.0%
8i 50.6 4.7 1.4 12.2% 8.1 15.0 45.7%
8j 18.4 4.3 1.3 30.0% 5.1 5.6 58.0%
8k 32.6 2.8 1.0 11.9% 5.0 7.3 37.5%
9a 46.4 0.0 0.0 0.0% 1.9 0.0 4.1%
9b 137.7 34.6 10.3 32.6% 41.1 41.9 60.3%
9c 30.5 8.6 2.5 36.2% 10.1 9.0 62.3%
9d 39.0 13.6 3.8 44.6% 14.0 12.8 68.7%
9e 13.8 5.8 0.7 47.0% 6.4 2.3 62.5%
9f 108.8 24.2 7.6 29.2% 32.0 24.9 52.3%
9g 26.2 0.4 6.7 27.2% 0.4 6.7 27.2%
9h 39.9 7.4 2.8 25.7% 7.6 14.6 55.8%
9i 25.1 7.2 5.9 52.5% 8.2 11.6 78.9%
9j 99.6 16.3 2.1 18.5% 19.3 25.7 45.2%
9k 15.9 3.3 4.9 51.4% 3.8 9.1 80.8%
9l 49.3 16.4 2.7 38.8% 18.0 13.3 63.6%
9m 17.1 7.0 10.1 99.9% 7.1 13.7 121.5%
10a 103.9 24.7 2.5 26.2% 28.1 25.0 51.1%
10b 23.5 3.9 3.1 29.8% 4.2 8.7 54.8%
10c 51.0 2.2 2.3 8.9% 2.8 19.5 43.6%
10d 21.4 5.2 0.2 25.3% 5.5 5.8 52.9%
11a 72.1 2.0 8.1 14.1% 7.3 24.6 44.4%
11b 76.7 17.8 1.8 25.6% 20.7 18.1 50.6%
11c 28.8 5.5 0.0 19.0% 6.4 5.6 41.7%
11d 3.7 0.0 1.1 30.6% 0.0 1.1 30.7%
11e 26.7 4.4 3.8 30.8% 5.8 7.9 51.3%
11f 33.6 6.3 11.2 52.2% 7.4 19.8 81.0%
12a 86.6 32.9 4.3 42.9% 34.5 22.0 65.3%
12b 20.1 4.3 4.7 44.8% 5.0 8.8 68.5%
12c 26.9 10.9 4.1 55.9% 11.2 9.2 76.2%
12d 30.8 13.0 1.4 46.9% 13.2 7.2 66.2%
12e1 13.5 3.6 13.5 100.0% 3.8 16.6 151.6%
12f 112.2 38.6 1.5 35.7% 38.9 26.2 58.0%
12g 14.3 2.0 4.3 44.5% 2.1 8.7 74.9%
13a 44.8 5.4 5.5 24.3% 5.9 17.9 53.0%
Stormwater Management Plan
City of Port Townsend
Table 3-4. Buildable Area – Impervious Comparison (continued)
January 2019│ 553-2836-004 3-21
Catchment
Total Area
(ac.)
Existing Impervious (ac.) Future Impervious (ac.)
ROW
Buildable
Area
Total Impervious
Percent ROW
Buildable
Area
Total Impervious
Percent
13b 51.9 15.9 0.9 32.5% 16.4 11.5 53.8%
13c 18.8 0.6 5.9 34.7% 2.2 8.2 55.4%
14.00 193.6 10.3 0.9 5.8% 12.5 10.0 11.7%
15a 131.7 5.1 0.3 4.1% 9.5 33.1 32.3%
15b 24.6 4.0 0.2 17.1% 4.6 7.0 46.8%
15c 24.0 1.3 1.6 12.4% 1.5 7.6 37.9%
16a 42.9 6.7 4.6 26.3% 9.5 13.4 53.4%
16b 62.7 8.3 0.5 14.1% 10.6 16.2 42.9%
16c 7.5 1.6 2.1 48.8% 2.0 3.8 77.9%
17a 53.7 7.0 3.8 20.1% 9.3 18.7 52.2%
17b 46.4 5.8 2.6 18.0% 6.4 14.4 44.9%
18a 141.6 5.0 0.5 3.9% 6.7 43.9 35.7%
18b 84.6 2.9 0.0 3.4% 6.5 23.0 34.8%
1 Impervious area and impervious percent were changed to full basin area.
Stormwater Management Plan
City of Port Townsend
January 2019│ 553-2836-004 3-23
Table 3-5a. Peak Runoff at Nodes or for Total Catchment – Existing1
Existing Runoff (cfs)
Storm Event Basin 1 Basin 2 Basin 3 Basin 4a Basin 4b Basin 4c Basin 4d Basin 4e Basin 4f Basin 4g Basin 4h Basin 4i Basin 4j Basin 4k Basin 4l Basin 4m Basin 5a Basin 5b Basin 5c Basin 5d
2-Year 0.02 2.25 0.06 0.01 0.23 3.68 0.08 0.78 2.12 2.77 0.30 1.32 0.40 1.83 3.70 0.60 0.24 0.82 0.53 0.28
10-Year 0.11 3.45 0.30 0.01 1.13 5.65 0.33 1.19 3.24 4.24 0.72 2.35 0.61 3.10 7.13 0.92 0.45 1.26 0.85 0.47
25-Year 0.15 3.94 0.43 0.02 1.65 6.56 0.50 1.41 3.84 4.57 1.09 3.54 0.75 4.63 10.80 1.10 0.61 1.41 0.97 0.57
100-Year 0.20 4.65 0.56 0.09 2.12 7.76 0.62 1.68 4.55 5.43 1.22 3.77 0.90 4.98 11.34 1.31 0.98 1.78 1.18 0.89
Storm Event Basin 6a Basin 6b Basin 6c Basin 7a Basin 7b Basin 7c Basin 7d Basin 7e Basin 7f Basin 8a Basin 8b Basin 8c Basin 8d Basin 8e Basin 8f Basin 8g Basin 8h Basin 8i Basin 8j Basin 8k
2-Year 2.62 0.44 0.16 0.54 0.23 2.32 1.11 0.31 0.04 2.25 2.24 2.10 0.43 0.11 1.21 0.41 0.24 0.71 0.74 0.49
10-Year 4.05 0.68 0.26 0.83 0.34 3.54 1.70 0.48 0.06 3.44 3.43 3.20 0.65 0.17 1.85 0.62 0.36 1.06 1.13 0.82
25-Year 4.86 0.78 0.30 1.00 0.36 3.90 1.84 0.54 0.07 4.20 4.06 3.80 0.70 0.18 2.19 0.66 0.39 1.13 1.35 1.21
100-Year 5.67 0.96 0.35 1.19 0.41 4.63 2.15 0.64 0.07 5.03 4.82 4.51 0.83 0.20 2.59 0.75 0.44 1.27 1.60 1.32
Storm Event Basin 9a Basin 9b Basin 9c Basin 9d Basin 9e Basin 9f Basin 9g Basin 9h Basin 9i Basin 9j Basin 9k Basin 9l Basin 9m Basin 10a Basin 10b Basin 10c Basin 10d Basin 11a Basin 11b Basin 11c
2-Year 0.01 4.90 1.15 1.91 0.63 3.26 1.44 1.42 1.63 2.07 1.25 1.81 2.63 2.44 0.94 1.31 0.49 2.05 1.84 0.62
10-Year 0.02 7.53 1.75 2.93 0.97 5.01 2.19 2.17 2.44 3.20 1.91 2.76 3.97 3.75 1.43 2.00 0.76 3.14 2.82 0.95
25-Year 0.02 8.86 2.08 3.29 1.05 5.91 2.37 2.58 2.61 4.48 2.06 3.03 4.25 4.95 1.58 2.55 1.03 3.90 3.75 1.30
100-Year 0.19 10.54 2.47 3.89 1.20 7.00 2.73 3.07 2.92 5.22 2.42 3.59 4.79 5.95 1.88 3.07 1.22 4.67 4.50 1.54
Storm Event Basin 11d Basin 11e Basin 11f Basin 12a Basin 12b Basin 12c Basin 12d Basin 12e Basin 12f Basin 12g Basin 13a Basin 13b Basin 13c Basin 14 Basin 15a Basin 15b Basin 15c Basin 16a Basin 16b Basin 16c
2-Year 0.23 1.21 2.74 3.24 1.23 1.63 1.24 1.29 3.72 1.09 1.88 1.72 1.22 2.91 0.82 0.59 0.55 1.75 0.98 0.49
10-Year 0.35 1.86 4.19 5.00 1.88 2.49 1.89 1.97 5.70 1.67 2.89 2.63 1.85 4.90 2.04 0.90 0.84 2.68 1.68 0.74
25-Year 0.39 2.16 4.53 5.87 2.07 2.75 2.24 2.13 6.83 1.79 3.37 3.17 2.01 7.29 3.09 1.09 0.99 3.18 2.51 0.81
100-Year 0.46 2.56 5.28 6.98 2.46 3.26 2.66 2.41 8.15 2.04 3.98 3.79 2.39 7.90 3.47 1.31 1.18 3.77 2.70 0.96
Storm Event Basin 17a Basin 17b Basin 18a Basin 18b
2-Year 1.46 1.19 0.78 0.50
10-Year 2.23 1.82 2.29 1.52
25-Year 2.86 2.34 3.48 2.30
100-Year 3.43 2.82 4.10 2.75
1Note: The peak rates shown are for the total runoff generated by the catchment only. The actual peaks at the nodes that include upstream accumulated and routed drainage are not included in this table.
Stormwater Management Plan
City of Port Townsend
3-24 January 2019│ 553-2836-004
Table 3-5b. Peak Runoff at Nodes or for Total Catchment – Future1
Future Runoff (Full Buildout, cfs)
Storm Event Basin 1 Basin 2 Basin 3 Basin 4a Basin 4b Basin 4c Basin 4d Basin 4e Basin 4f Basin 4g Basin 4h Basin 4i Basin 4j Basin 4k Basin 4l Basin 4m Basin 5a Basin 5b Basin 5c Basin 5d
2-Year 0.21 4.39 0.06 0.01 0.27 5.65 0.08 1.41 6.11 6.20 0.73 4.14 0.42 4.80 10.14 1.84 1.39 2.52 1.31 1.75
10-Year 0.32 6.71 0.30 0.01 1.16 8.60 0.34 2.14 9.37 9.45 1.13 6.36 0.64 7.33 15.51 2.82 2.14 3.90 2.01 2.69
25-Year 0.39 7.27 0.43 0.02 1.74 9.32 0.50 2.35 10.07 10.14 1.59 7.45 0.77 8.71 18.52 3.05 2.56 4.42 2.25 3.01
100-Year 0.47 8.38 0.56 0.09 2.17 11.09 0.62 2.79 11.55 11.54 1.84 8.81 0.92 10.33 22.10 3.53 3.00 5.57 2.84 3.80
Storm Event Basin 6a Basin 6b Basin 6c Basin 7a Basin 7b Basin 7c Basin 7d Basin 7e Basin 7f Basin 8a Basin 8b Basin 8c Basin 8d Basin 8e Basin 8f Basin 8g Basin 8h Basin 8i Basin 8j Basin 8k
2-Year 5.03 0.82 0.42 1.19 0.75 4.17 1.99 0.63 0.08 5.42 5.34 4.14 0.61 0.18 2.56 0.90 0.32 1.85 1.22 1.11
10-Year 7.76 1.26 0.64 1.81 1.13 6.40 3.03 0.96 0.13 8.27 8.16 6.32 0.94 0.27 3.91 1.35 0.48 2.77 1.86 1.71
25-Year 8.69 1.41 0.72 1.95 1.20 6.88 3.25 1.04 0.14 8.94 8.83 6.83 1.01 0.29 4.24 1.44 0.51 2.96 2.02 2.02
100-Year 10.94 1.78 0.91 2.32 1.34 7.88 3.70 1.20 0.15 10.51 10.24 8.04 1.16 0.32 4.90 1.62 0.57 3.31 2.40 2.40
Storm Event Basin 9a Basin 9b Basin 9c Basin 9d Basin 9e Basin 9f Basin 9g Basin 9h Basin 9i Basin 9j Basin 9k Basin 9l Basin 9m Basin 10a Basin 10b Basin 10c Basin 10d Basin 11a Basin 11b Basin 11c
2-Year 0.01 9.86 2.34 3.58 1.00 7.36 1.44 3.24 2.72 4.68 2.06 3.42 3.31 6.42 1.69 4.73 1.65 3.28 4.84 1.35
10-Year 0.02 15.05 3.57 5.48 1.52 11.25 2.20 4.95 4.08 7.18 3.13 5.25 4.96 9.76 2.58 7.24 2.51 5.03 7.37 2.07
25-Year 0.02 16.26 3.86 5.90 1.63 12.18 2.38 5.35 4.35 8.25 3.35 5.64 5.29 10.66 2.78 7.81 2.71 5.80 8.06 2.37
100-Year 0.19 19.12 4.51 6.78 1.85 14.08 2.73 6.25 4.88 9.73 3.81 6.46 5.93 12.66 3.20 8.98 3.19 6.85 9.57 2.79
Storm Event Basin 11d Basin 11e Basin 11f Basin 12a Basin 12b Basin 12c Basin 12d Basin 12e Basin 12f Basin 12g Basin 13a Basin 13b Basin 13c Basin 14 Basin 15a Basin 15b Basin 15c Basin 16a Basin 16b Basin 16c
2-Year 0.23 1.94 3.87 6.66 2.11 2.65 2.24 2.07 7.81 1.86 4.14 3.55 1.83 4.11 2.47 1.01 0.86 2.98 2.77 0.84
10-Year 0.35 2.97 5.92 10.16 3.24 4.06 3.42 3.10 11.95 2.81 6.34 5.41 2.80 6.33 3.79 1.55 1.32 4.56 4.26 1.28
25-Year 0.39 3.21 6.34 10.98 3.47 4.37 3.70 3.33 12.90 3.00 6.84 5.85 3.02 8.63 4.96 1.74 1.48 4.92 4.99 1.37
100-Year 0.46 3.80 7.23 12.87 3.98 5.02 4.37 3.72 15.29 3.38 7.86 6.96 3.46 10.25 5.97 2.06 1.75 5.84 5.91 1.57
Storm Event Basin 17a Basin 17b Basin 18a Basin 18b
2-Year 2.33 2.47 2.06 1.29
10-Year 3.58 3.79 3.45 2.19
25-Year 4.21 4.24 5.11 3.28
100-Year 4.99 5.02 5.57 3.52
1Note: The peak rates shown are for the total runoff generated by the catchment only. The actual peaks at the nodes that include upstream accumulated and routed drainage are not included in this table.
Stormwater Management Plan
City of Port Townsend
January 2019│ 553-2836-004 3-25
3.1.4 Catchments with Largest Increase Potential
The existing and future peak runoff determined in Table 3-5a and Table 3-5b above provide an indicator
of where the highest potential impacts could occur or where there are priorities for further evaluation
or improvements. Table 3-6 shows the peak 25-year runoff rates under existing and future conditions
and the percent change. The highest potential changes shown can provide a basis for prioritizing other
improvements that may be identified in Section 4.
Table 3-6. Potential Change in Peak Flows by Catchment Area
Catchment Number
Existing Peak 25-year
Flow (cfs)
Future Peak 25-year
Flow (cfs) Percent Change
Rank (highest
change)
1 0.2 0.4 160% 10
2 3.9 7.3 84% 33
3 0.4 0.4 0% 82
4a 0.0 0.0 0% 83
4b 1.7 1.7 5% 77
4c 6.6 9.3 42% 72
4d 0.5 0.5 2% 79
4e 1.4 2.3 67% 52
4f 3.8 10.1 162% 8
4g 4.6 10.1 122% 13
4h 1.1 1.6 45% 69
4i 3.5 7.4 111% 19
4j 0.7 0.8 3% 78
4k 4.6 8.7 88% 29
4l 10.8 18.5 71% 46
4m 1.1 3.0 177% 6
5a 0.6 2.6 317% 2
5b 1.4 4.4 214% 4
5c 1.0 2.3 133% 12
5d 0.6 3.0 427% 1
6a 4.9 8.7 79% 42
6b 0.8 1.4 81% 39
6c 0.3 0.7 140% 11
7a 1.0 2.0 96% 25
7b 0.4 1.2 233% 3
7c 3.9 6.9 76% 44
7d 1.8 3.3 77% 43
7e 0.5 1.0 90% 27
7f 0.1 0.1 106% 22
8a 4.2 8.9 113% 18
8b 4.1 8.8 117% 15
8c 3.8 6.8 80% 40
8d 0.7 1.0 43% 70
Stormwater Management Plan
City of Port Townsend
Table 3-6. Potential Change in Peak Flows by Catchment Area (continued)
3-26 January 2019│ 553-2836-004
Catchment Number
Existing Peak 25-year
Flow (cfs)
Future Peak 25-year
Flow (cfs) Percent Change
Rank (highest
change)
8e 0.2 0.3 59% 56
8f 2.2 4.2 93% 26
8g 0.7 1.4 118% 14
8h 0.4 0.5 31% 74
8i 1.1 3.0 162% 9
8j 1.3 2.0 50% 62
8k 1.2 2.0 67% 51
9a 0.0 0.0 0% 84
9b 8.9 16.3 84% 36
9c 2.1 3.9 86% 32
9d 3.3 5.9 79% 41
9e 1.0 1.6 55% 60
9f 5.9 12.2 106% 21
9g 2.4 2.4 0% 81
9h 2.6 5.4 108% 20
9i 2.6 4.4 67% 50
9j 4.5 8.2 84% 35
9k 2.1 3.4 63% 54
9l 3.0 5.6 86% 31
9m 4.2 5.3 25% 75
10a 4.9 10.7 115% 16
10b 1.6 2.8 76% 45
10c 2.6 7.8 206% 5
10d 1.0 2.7 164% 7
11a 3.9 5.8 49% 65
11b 3.8 8.1 115% 17
11c 1.3 2.4 82% 37
11d 0.4 0.4 0% 80
11e 2.2 3.2 48% 66
11f 4.5 6.3 40% 73
12a 5.9 11.0 87% 30
12b 2.1 3.5 67% 49
12c 2.7 4.4 59% 57
12d 2.2 3.7 65% 53
12e 2.1 3.3 56% 59
12f 6.8 12.9 89% 28
12g 1.8 3.0 68% 48
13a 3.4 6.8 103% 23
13b 3.2 5.8 84% 34
13c 2.0 3.0 50% 64
14 7.3 8.6 18% 76
15a 3.1 5.0 61% 55
15b 1.1 1.7 59% 58
Stormwater Management Plan
City of Port Townsend
Table 3-6. Potential Change in Peak Flows by Catchment Area (continued)
January 2019│ 553-2836-004 3-27
Catchment Number
Existing Peak 25-year
Flow (cfs)
Future Peak 25-year
Flow (cfs) Percent Change
Rank (highest
change)
15c 1.0 1.5 50% 63
16a 3.2 4.9 55% 61
16b 2.5 5.0 99% 24
16c 0.8 1.4 70% 47
17a 2.9 4.2 47% 67
17b 2.3 4.2 81% 38
18a 3.5 5.1 47% 68
18b 2.3 3.3 42% 71
3.2 Stormwater System Operation and Maintenance
Proper operation and maintenance of the stormwater system is necessary to prolong life and
effectiveness of the system as well as reduce the potential for flooding and improve water quality. There
are several sources and guidelines as well as direct experience used to develop the City’s stormwater
practices.
Ecology provides guidance on best management
practices (BMPs) for municipal operations in the
Stormwater Management Manual for Western
Washington (SWMMWW). This manual was developed
in response to federal requirements and tailored to
conditions in the Pacific Northwest.
Below are the recommended BMPs from the SWMMWW the City of Port Townsend uses for guidance
for stormwater system maintenance.
• Maintenance of Public and Private Utility Corridors and Facilities
• Maintenance of Roadside Ditches
• Maintenance of Stormwater Drainage and Treatment Systems
• Spills of Oil and Hazardous Substances
• Urban Streets
• Recommendations for Management of Street Wastes.
The operation and maintenance of the stormwater system is funded by a stormwater utility fund and
includes 3.55 full time equivalents (FTEs) distributed amongst several employees. This number is likely to
increase as the stormwater system is extended or enhanced, increasing the need for maintenance.
Stormwater Management Plan
City of Port Townsend
3-28 January 2019│ 553-2836-004
Maintenance of the stormwater system includes:
• Cleaning, repairing and replacing ditches, swales, and storm drains;
• Cleaning and maintaining catch basins;
• Filter inspection and cleaning;
• Street sweeping to improve water quality;
• Maintaining stormwater ponds and infiltration galleries;
• Vegetation control;
• Repairing roadways damaged by stormwater;
• Checking for illicit discharges to the stormwater system;
• Stormwater utility locates; and
• Emergency response.
The City owns and operates the equipment necessary for most stormwater system maintenance such as
vacuum truck for removing debris from catch basins, a street sweeper, dump trucks, various heavy
equipment and related tools and implements.
The City of Port Townsend has developed a process over the years to identify, track and schedule
stormwater system operation and maintenance activities. Listed below are current elements and
activities.
3.2.1 Asset Identification
Most all stormwater system assets have been identified or are in the process of being identified and
mapped and are available electronically and summarized in Table 3-7. Mapping includes the location of
catch basins, culverts, detention ponds, biofiltration swales, infiltration trenches, drain pipe, rain
gardens, compost filters and roadside ditches. Roadside areas that do not have adequate drainage are
also noted. Data can be accessed electronically with a computer or device or available in printed map
sets. Streets, roadways, trails and open space are all considered part of the stormwater system.
3.2.2 Level of Service
The level of service is measured by frequency and labor requirements as suggested by Department of
Ecology guidelines and is listed in Table 3-8 for the City of Port Townsend.
3.2.3 Reporting
Most all work is issued via work order and reported and coded to the utility on timesheets. Summary
reports can be generated from work orders and timesheets to update the level and cost of service.
Stormwater Management Plan
City of Port Townsend
January 2019│ 553-2836-004 3-29
Table 3-7. Existing Inventory of Public Facilities
Facility Type Quantity Measurement Unit
Streets Swept
Street Swept 30 Miles
Total All Roads 94 Miles
Catch Basins 1,468 Each
Maintenance Holes 114 Each
Infiltration Trenches/Perforated Pipes 0.9 Miles
Solid Pipes 25 Miles
Swales 4.1 Miles
Detention Ponds/Retention 7 Each
Culverts 3,183 Linear Feet (LF)
Storm Filters 7 Each
Stormwater Pump Facilities 2 Each
Stormwater Management Plan
City of Port Townsend
3-30 January 2019│ 553-2836-004
Table 3-8. Maintenance Frequency and Personnel
Facility Type Frequency Level of Effort
Street Sweeping
Downtown 52 times/year 1 Maintenance Worker, 1 Sweeper
Arterials 12 times/year 1 Maintenance Worker, 1 Sweeper
Catch Basin
Cleaning 1 time/year 2 Maintenance Workers, 1 Vactor, 1 truck
Repair/Replace 1 time/3o years 3 Maintenance Workers1 Backhoe,
1 Dumptruck, 1 truck Traffic Control
Maintenance Holes
Cleaning 1 time/year 2 Maintenance Workers, 1 Vactor, 1 truck
Repair/Replace 1 time/30 years 3 Maintenance Workers1 Backhoe,
1 Dumptruck, 1 truck Traffic Control
Infiltration Trenches
Cleaning 1 time/year 2 Maintenance Workers, 1 Vactor, 1 truck
Repair/Replace 1 time/15 years 3 Maintenance Workers,
1 Backhoe, 1 Dumptruck, 1 truck Traffic Control
Pipes
Flushing/Vactor 1 time/3 years 2 Maintenance Workers, 1 Vactor, 1 truck
Repair 1time/50 years 3 Maintenance Workers
1 Backhoe, 1 Dump truck, 1 truck Traffic Control
Swales
Vegetation/Cleaning 4 time/year 2 Maintenance Workers, 1 Vactor, 1 truck
Repair/Replace 1 time/10 years 3 Maintenance Workers, 1 Backhoe, 1 Dumptruck
Detention Ponds/Retention
Control Structure
Cleaning 1 time/year 2 Maintenance Workers, 1 Vactor, 1 truck
Repair/Replace 1 time/30 years 3 Maintenance Workers,
1 Backhoe, 1 Dump truck, 1 truck
Pond
Cleaning/Vegetation 3 times/year 1 Maintenance Worker, 1 Weed Whip
Remove Sediment 1 time/5 years 3 Maintenance Workers,
1 Backhoe, 1 Dump truck, 1 truck
Ditches
Vegetation Control 3 times/year 2 Maintenance Workers, 1 Mower
Clean, Reshape, Remove
Sediment
1 time/5 years 4 Maintenance Workers, 1 Backhoe, 2 Dump trucks
Culverts
Clean 1 time/3 years 2 Maintenance Workers, 1 Vactor, 1 truck
Clean Inlets 2 times per year 2 Maintenance Workers, 1 truck
Stormwater Management Plan
City of Port Townsend
January 2019│ 553-2836-004 4-1
4. BASIN PLANNING
4.1 Planning Objectives
Stormwater planning needs and objectives were discussed with City staff and the task force during early
phases of the project. Technical assessments of the physical setting and watersheds were made, as
described in Section 2. Section 3 describes existing conditions and development potential. This section
describes the findings and recommended approaches to addressing existing and potential impacts to the
drainage and natural systems, based on the analysis in Chapter 3.
The following sections describe the systems and needs for which approaches have been developed to
maintain, protect, control, and upgrade natural and built stormwater systems, including:
• Assessing drainage connectivity and providing for protection of the natural and built drainage
system;
• Identifying potential impacts to drainage systems, natural drainage courses, and wetlands, and
techniques for reducing impact from future development (i.e., using LID to the maximum
practicable extent);
• Defining future road drainage guidelines;
• Identifying potential future impacts to the natural drainage system; and
• Identifying roadway water quality improvements in the right-of-way.
4.2 Drainage Connectivity
The City has been divided into 19 drainage basins, originally delineated using the boundaries in the 1987
Plan, and updated based on better topographic information, the roadside drainage network, and the
drainage flow path in existing pipes and swales (Figure 12). Each of the numbered basins has a final
disposition or discharge to a receiving water or location, except basin 17, which drains to basin 9.
Figure 2 shows the numbered basins and their disposition and Table 4-1 lists the basin number and the
discharge point. Several basins directly runoff or are conveyed via storm sewers to the Salish Sea
without entering natural drainage paths or wetlands. Two receiving waters, Kah Tai Lagoon and Chinese
Gardens, also discharge to the Salish Sea.
Stormwater Management Plan
City of Port Townsend
4-2 January 2019│ 553-2836-004
Table 4-1. Basins and Disposition or Discharge Point
Receiving Water1 or Discharge Point Basin Number Note
Salish Sea, direct 1, 2, 3, 10, 12, 13, 14 Sheet flow or storm sewer, often via multiple
discharge points
Ravines, unnamed channel 11, 16 Flows to points outside of city limits
Chinese Gardens 4
Kah Tai Lagoon 9 Basin 17 flows through Basin 9 to Kah Tai
Lagoon
Closed wetland or groundwater 52, 6, 7, 8, 19 Here is no surface water outlet from these
basins to the ocean
Jefferson County 15, 17, 18 Ultimate disposition was not determined
1 Receiving Water—a named or known “water of the state” or the Salish Sea.
2 Basin 5 can connect to Basin 4 if the water level rises high enough. There is no record of it doing so.
4.2.1 Drainage System Hierarchy
A key objective of the Plan is to define, provide, and protect a connected and well-defined built and
natural drainage system. One challenge of doing so in Port Townsend is the almost complete lack of
natural drainage systems such as streams and rivers. Without obvious natural watercourses and with
the extensive land pre-platting that has occurred, the flow paths to collect and carry stormwater to the
ocean are not well-structured and, in many cases, have no outlet to the ocean. Special measures are
needed to define and protect the built and natural drainage system. Consequently, a hierarchy to define
the drainage network was developed to describe its components and provide measures for protecting,
controlling, or improving a segment in a way that is consistent with its position in the network and
hierarchy. The recommended protection measures may include new or modified ordinances and
standards identifying mitigation or protection measures outlined in development guidance materials.
A system with four “levels” to define the drainage network was developed (Figure 13). Like a stream
ordering system, the highest level provides the backbone or trunk of the system (the highest order in
the hierarchy), while each subsequent level typically drains to the next higher numbered level in the
system. For Port Townsend, the levels are defined as follows:
Level 1 Receiving Locations – Level 1 are the terminus for each basin and includes all natural waters
(usually named), “waters of the state” or “waters of the United States”. Level 1 are the “Receiving
Waters” and includes the Salish Sea (Strait of Juan de Fuca, Admiralty Inlet, and Port Townsend Bay);
Chinese Gardens; Kah Tai Lagoon; named wetlands in Basins 5, 6, 7, and 8 (Blue Heron, 35th Street Park,
Froggy Bottoms, Glasbell, and Hastings Pond); the basin 5 terminus to groundwater; and the Quimper
Wildlife Corridor (as defined by the 100-year floodplain (see Figure 4). The extent or limits of a Level 1
water is the ordinary high-water line.
Level 2 Natural Drainage – Level 2 includes natural, piped, or planned main connectors to the Level 1
receiving locations for stormwater. They are the branches that connect to the trunk, often natural paths,
delivering runoff to Level 1 waters. Generally, they are located at the lowest point of the basins, or along
a main road in the basin. All Level 2 waters drain to or connect with Level 1 waters. The Level 2 Natural
Drainage hierarchy is divided into two types: Level 2a CDCs and Level 2b KDs. CDCs are protected
through the City’s CAO. The KDs are regulated through the Stormwater Plan and the City’s Engineering
Design Standards. They are both important connecting features of the City’s stormwater drainage
network (see Figure 13).
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2019 Stormwater Management Plan Page 4 - 3
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2019 Stormwater Management Plan Page 4 - 4
Stormwater Management Plan
City of Port Townsend
January 2019│ 553-2836-004 4-5
Level 2a and 2b routes were determined for this Plan by following the apparent center line of flow paths
using the topographic map of the city and connecting to Level 1 waters. In some instances, the Level 2a
CDCs cross built areas or roads; the CDC is considered continuous. The Level 2b KDs can follow a
constructed drainage path, usually a road drainage system, for part of its path.
Level 2a CDCs – Level 2a areas are defined in the City’s Critical Area Ordinance and includes natural low
areas and depressions in the landscape, often linear, and are characterized as a year-round or
intermittent naturally flowing watercourse which exhibits but is not limited to one or more of the
following characteristics:
a. A stream or watercourse formed by nature or modified by humans;
b. Generally consisting of a defined channel with a bed for a substantial portion of its length on the lot;
and
c. Perched ponds, ravines or other natural drainage features.
All CDCs (Level 2a drainage) are continuous and unbroken from its starting point downstream to its
connection with a Level 1 water. To provide network continuity for the purposes of this SMP, a CDC or
Level 2a water is considered continuous over and through wetlands that are encountered.
Level 2b KDs – Level 2b areas includes natural low areas and depressions in the landscape, to where
water would flow if enough runoff was generated by a storm, but moving water is not routinely seen or
has not been observed. In some instances, the Level 2b is a constructed drainage feature, for example a
road drainage system, for part of its path. Level 2b waters generally drain to or connect with Level 1
receiving locations.
Level 3 Connecting Drainage Paths and Infrastructure – Level 3 includes flow paths that connect the
built environment with the Level 1 waters or Level 2a and 2b drainageways. They provide continuity and
connectivity for drainage created by the roadways and land development to the natural topographic
flow paths. Level 3 drainage tends to be local and relatively short segments that include formal
(man-made ditches and storm sewers) and informal (poorly defined) flow paths and channels. Level 3
segments are not depicted on a figure, as they are ongoing and newly defined elements of the mapped
drainage system when identified and described. Level 3 segments can be defined by the city at any time
when a detailed drainage analysis or review is made for new development. The long-term objective of
defining and identifying Level 3 segments is for the city to gain control via easement or right-of-way to
allow for protection, improvement, operation and maintenance of those segments. The Level 3
connectors may need to be constructed by new developments, through off-site mitigation, where no
connection between a Level 2 or Level 4 exists.
Level 4a and 4b Constructed Drainage System – Level 4 includes the constructed drainage systems in
the road rights-of-way. Level 4 represents the constructed drainage infrastructure that follows the
roadway system and is either well-defined by ditches, swales, curbs, storm sewers and culverts or less
well-defined roadside drainage. Level 4 has been divided into Level 4a and 4b; Level 4a represents a
defined network of key constructed drainage pathways along major roads (e.g., arterials and collectors)
and Level 4b represent the rest of the road network (e.g., local access and neighborhood roads) where
the roadway drainage may be poorly defined or non-existent. Level 4 roadway drainage provides the
primary disposition for site drainage for development. Level 4 should connect to a higher Level for
disposition to a receiving water.
Stormwater Management Plan
City of Port Townsend
4-6 January 2019│ 553-2836-004
4.2.2 Drainage System Connectivity
The 19 basins were additionally broken down into catchment areas as shown on Figure 11. These areas
were defined by topography and the configuration and disposition of the drainage system as currently
understood and mapped. The CDCs and KDs (Levels 2a and 2b) provide a foundation for the network of
natural drainage patterns defined by topography and provide connectivity to Level 1 receiving waters.
The built drainage is almost completely located within the roadway network (Level 4). The network
shown in the hierarchy system shows connectivity, but it does not indicate the size, capacity, or
performance of the drainage system. To do so would require intensive data collection and modelling
which is outside the scope of this analysis and is not needed to provide guidance to inform the planning
effort.
Figures 8 and 13 show the catchment areas and associated KDs. The location of the peak flow rate in
each drainage path is indicated at the downstream end where it discharges into a different catchment.
4.2.3 Drainage System Protection
The purpose of the drainage system definition and connectivity system described above was to provide
a framework for analysis, protection, planning, and operations. Higher level systems (e.g., Level 1 and 2)
may need greater protection; lower level systems (e.g., Level 3 and 4) need more improvements and
maintenance. The following is general outline of key drainage resources needing protection and an
approach to evaluating those protections.
Level 1 Receiving Waters
Protection:
Most or all Level 1 receiving waters have protections through the Shoreline Management Plan, critical
areas ordinances, and floodplain management.
Guidelines:
Ordinance and Code should have language to protect the conveyance, flood control, water quality, and
hydrologic aspects of the resource (Port Townsend Municipal Code [PTMC] 19.05).
Provide measures for mitigating and providing the conveyance, flood control, and water quality aspects
of Level 1 at road crossings in unopened rights-of-way
Evaluation and Improvements:
Review protection guidelines
Prepare guidance for providing conveyance, flood control, and water quality mitigation measures when
impacts to Level 1 resource cannot be avoided.
Level 2 Natural Drainage via Critical Drainage Corridors or Key Drainageways
Protection:
Critical Drainage Corridors are protected by the critical areas ordinance.
Key Drainageways are defined and regulated by stormwater standards.
Guidelines:
CDC Ordinance and Code should have language to protect the conveyance, flood control, water quality,
and hydrologic aspects of the resource (PTMC 19.05).
Stormwater Management Plan
City of Port Townsend
January 2019│ 553-2836-004 4-7
KD should identify and protect the conveyance, flood control, water quality, and hydrologic aspects of
the resource, and provide measures to quantify and mitigate unavoidable impacts. Key Drainageways
may be modified by development provided the functionality is maintained.
Evaluation and Improvements:
Review and update KD maps as needed.
Provide definition, standards and review guidelines; prepare process for evaluating modifications; and
prepare standards for mitigating unavoidable impacts to Level 2 resources; and prepare guidance for
providing the conveyance and water quality aspects of Level 2 resources.
Level 3 Connecting Drainage
Protection:
Level 3 drainage connections should be identified and protected through easements, fee purchase, or
other related permission to maintain and protect drainage connectivity.
Guidelines:
Create requirement and approach to identify Level 3 connections during the development review
process.
Identify and catalogue Level 3 connections for prioritization and protection.
Evaluation and Improvements:
Review and update Level 3 connections maps or list as needed.
Prioritize Level 3 connections for protection.
Level 4 Constructed Drainage System
Protection:
Level 4 drainage is included in rights-of-way; no further ownership or regulation is needed.
Standards for right-of-way use are needed.
Guidelines:
Create or update right-of-way use permits.
Use sizing guidelines prepared in Section 4 for pipe size, ditch size, and minimum drainage
requirements.
Prepare Level 4b development requirements and funding strategy.
Prepare development review and fees for Level 4b program.
Evaluation and Improvements:
Inventory pipe and ditch deficiencies in Level 4a.
Prioritize Level 4a upgrade or repair needs.
Prioritize Level 4b upgrade and repair needs.
Prepare a strategy for regular improvements in Level 4a and 4b.
Stormwater Management Plan
City of Port Townsend
4-8 January 2019│ 553-2836-004
4.2.4 Evaluating Potential Capacity Needs and Impacts
In Section 3, basin characteristics were identified to estimate existing and future runoff in the basins.
Tables 3-5a (existing peak runoff) and 3-5b (future peak runoff) show the results of the modeling. The
analysis is used to determine two planning needs: where are there expected impacts due to existing and
future development and what pipe and ditch capacity is needed for roadway drainage. Details of runoff
modeling and conveyance capacity analysis are presented in Appendix D. The impact analysis and
drainage capacity were evaluated by modeling the catchment areas for the existing and future
(uncontrolled) runoff (see Tables 3-5a and 3-5b). The peak flows shown occur at the catchment area
nodes shown on Figure 11. Use of these data for drainage capacity and impact analysis are described in
the following sections.
4.2.4.1 Drainage Capacity
Drainage capacity refers to the size and configuration of the conveyance ways and drainage systems for
conveying stormwater to receiving waters, including the Level 1, 2, and 4 drainage paths. Modeling the
entire city drainage system would be a very costly task and is rarely done in smaller cities. Modeling the
Level 1 and Level 2a and 2b (CDCs and KD) for drainage capacity has limited utility as the corridors are
very large relative to the flows, although an impact analysis is important and described below in Section
4.2.5. In lieu of modeling all of the Level 4 drainage paths and systems, a generalized runoff and capacity
analysis was completed to provide information on pipe sizing under normal conditions. The results are
not expected to vary greatly from one location in the City to another due the low rainfall, similar
roadside conditions, and relatively insensitivity of standard pipe sizing to small flow differences.
The approach taken to evaluating drainage capacity is to consider the typical “long path” of drainage
within a catchment basin and use that as a basis for the peak flows expected in any drainage system in
the catchment. The peak runoff from the catchment was determined for different design storms, with
the understanding that the runoff from the entire catchment would always be greater than or equal to
the runoff from the longest drainage segment in the drainage area. Table 3-5b shows the peak runoff for
future uncontrolled runoff generated by a catchment.
To evaluate drainage needs, standard pipe slopes and roadside ditch configurations were considered.
The minimum pipe size allowed by current City Code (Engineering Design Standards) is 12-inches. The
standard roadside ditch has a bottom width between 2- and 8-feet with 3:1 slide slopes. Table 4-2a
shows the capacity of the standard minimum allowable pipes per slope percentage. Figure 14a is a
graphic representation of Table 4-2a, or “look-up table” which is used to select a pipe size when the
peak flow and slope are known. To use Figure 14a, enter the x-axis with the conveyance or existing ditch
slope and move vertically to the intercept with the peak design flow. The region of this intercept
indicates the pipe size needed. Table 4-2b shows the capacity of different ditch widths per slope
percentage. Figure 14b is a “look-up table” for ditch width and is used the same way as Figure 14a.
Stormwater Management Plan
City of Port Townsend
January 2019│ 553-2836-004 4-9
Table 4-2a. Pipe Capacity for Reaches of Different Slopes
Slope (percent) Capacity of 12" Pipe1 (cfs) Capacity of 18" Pipe (cfs)
0-2 5.0 14.9
2-4 7.1 21.0
4-6 8.7 25.7
6-8 10.1 29.7
8-10 11.3 33.2
1 This value is the minimum capacity of the standard required drainage conveyance systems
Figure 14a. Pipe Capacity “Look Up Table”
Table 4-2b. Ditch Capacity for Reaches of Different Slopes
Slope
(percent)
Capacity of 2-foot1 Ditch
(cfs)
Capacity of 4-foot ditch
(cfs)
Capacity of 6-foot ditch
(cfs)
Capacity of 8-foot ditch
(cfs)
0-2 1.8 3.2 4.7 6.1
2-4 2.5 4.6 6.6 8.7
4-6 3.1 5.6 8.1 10.6
6-8 3.6 6.4 9.3 12.3
8-10 4.0 7.2 10.4 13.7
0
5
10
15
20
25
30
35
40
45
50
0 2 4 6 8 10
Fl
o
w
(
c
f
s
)
Slope (%)
Capacity of 12" Pipe (cfs)Capacity of 18" Pipe (cfs)
>18"pipe size required
18" pipe size required
12" pipe size required
Stormwater Management Plan
City of Port Townsend
4-10 January 2019│ 553-2836-004
Figure 14b. Ditch Capacity “Look up Table”
4.2.4.2 Standard Drainage System Sizing
When designing or improving drainage in the roadway system, such as the Level 4 drainage system, the
peak expected flow rate and channel slope are needed to design the pipe or ditch sizes needed. The City
has standard minimum sizes for pipes (12-inch) and ditches (2-foot bottom), therefore many of
roadways will use the minimum conveyance sizes. The drainage system capacity should include future
conditions, which are not always known by persons proposing pipes in the right-of-way or the City when
improvements are needed.
Table 4-3 shows the 25-year peak flows expected in all catchments under future uncontrolled
conditions. This would be the largest peak flow expected at any location in the catchment except for
reaches that pass through the catchment that have accumulated upstream flows (Figure 15). A reach is
the primary path in which runoff is collected and conveyed in a catchment to the next downstream
catchment and reach. The flow rate in a reach with an upstream catchment is higher than the flows
generated by the catchment alone. Therefore, if the largest design peak flow in a catchment is smaller
than the minimum allowable pipe or ditch capacity, no additional calculations need to be made to size
conveyance systems in the roadside channels. The rows noted in Table 4-3 indicated by “Yes” means
that the maximum expected stormwater flow in the catchment can be handled by the minimum sizes,
and therefore no further evaluation of potential capacity is needed. The slope used for each catchment
is estimated from available topographic mapping provided by the City at the locations shown on
Figure 15. Note that the 2-foot ditch width fails in a majority of catchments. It is recommended that the
2-foot minimum ditch no longer be used unless site or project-specific calculations are made to
demonstrate that it provides adequate capacity.
0
5
10
15
20
25
30
35
40
0 2 4 6 8 10
Fl
o
w
(
c
f
s
)
Slope (%)
Capacity of 2' Ditch (cfs)Capacity of 4' Ditch (cfs)
Capacity of 6' Ditch (cfs)Capacity of 8' Ditch (cfs)
2' ditch required
4' ditch required
6' ditch required
8' ditch required
>8' ditch needed, further
evaluation needed
((
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Tibbal'sLake
FroggyBottoms
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2 3
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12 12
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Figure 15Long Paths, CDCs & KDs
0 0.25 0.5 0.75 1
Miles
Roadways
Q:
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Potential Wetlands
Wetlands
Features
Critical Drainage Corridors
Key Drainageways
100 Year Flood
City Limits
Drainage Basins(19
2019 Stormwater Management Plan Page 4 - 11
Stormwater Management Plan
City of Port Townsend
4-13 January 2019│ 553-2836-004
Table 4-3. Catchment Area Peak flows and Maximum Required Drainage Conveyance
Catchment
Node
Estimated
Slope (ft/ft)
Future 25-year
Peak Flow (cfs)
Pass
Criteria for
12" Pipe
Pass Criteria
for 2' Ditch
Pass
Criteria for
4' Ditch
Pass
Criteria for
6' Ditch
Pass
Criteria for
8' Ditch
1 4.0% 0.4 Yes Yes Yes Yes Yes
2 4.4% 7.3 Yes No No Yes Yes
3 4.0% 0.4 Yes Yes Yes Yes Yes
4a 4a is a wetland
4b 4.0% 1.7 Yes Yes Yes Yes Yes
4c 2.9% 9.3 No No No No No
4d 4.0% 0.5 Yes Yes Yes Yes Yes
4e 2.3% 2.3 Yes Yes Yes Yes Yes
4f 2.5% 10.1 No No No No No
4g 2.0% 10.1 No No No No No
4h 5.3% 1.6 Yes Yes Yes Yes Yes
4i 1.7% 7.4 No No No No No
4j 2.0% 0.8 Yes Yes Yes Yes Yes
4k 1.5% 8.7 No No No No No
4l 3.6% 18.5 No No No No No
4m 9.0% 3.0 Yes Yes Yes Yes Yes
5a 2.1% 2.6 Yes No Yes Yes Yes
5b 1.0% 4.4 Yes No No Yes Yes
5c 2.0% 2.3 Yes Yes Yes Yes Yes
5d 6.7% 3.0 Yes Yes Yes Yes Yes
6a 2.0% 8.7 No No No No Yes
6b 1.3% 1.4 Yes Yes Yes Yes Yes
6c 1.2% 0.7 Yes Yes Yes Yes Yes
7a 1.3% 2.0 Yes No Yes Yes Yes
7b 3.3% 1.2 Yes Yes Yes Yes Yes
7c 1.7% 6.9 No No No No No
7d 4.8% 3.3 Yes No Yes Yes Yes
7e 1.7% 1.0 Yes Yes Yes Yes Yes
7f 1.0% 0.1 Yes Yes Yes Yes Yes
8a 2.8% 8.9 No No No No No
8b 4.4% 8.8 Yes No No No Yes
8c 4.3% 6.8 Yes No No Yes Yes
8d 6.9% 1.0 Yes Yes Yes Yes Yes
8e 3.3% 0.3 Yes Yes Yes Yes Yes
8f 6.2% 4.2 Yes No Yes Yes Yes
8g 4.0% 1.4 Yes Yes Yes Yes Yes
Stormwater Management Plan
City of Port Townsend
Table 4-3. Catchment Area Peak flows and Maximum Required Drainage Conveyance (continued)
4-14 January 2019│ 553-2836-004
Catchment
Node
Estimated
Slope (ft/ft)
Future 25-year
Peak Flow (cfs)
Pass
Criteria for
12" Pipe
Pass Criteria
for 2' Ditch
Pass
Criteria for
4' Ditch
Pass
Criteria for
6' Ditch
Pass
Criteria for
8' Ditch
8h 4.0% 0.5 Yes Yes Yes Yes Yes
8i 1.8% 3.0 Yes No Yes Yes Yes
8j 0.4% 2.0 Yes No Yes Yes Yes
8k 1.0% 2.0 Yes No Yes Yes Yes
9a 9a is a wetland
9b 2.1% 16.3 No No No No No
9c 4.8% 3.9 Yes No Yes Yes Yes
9d 5.2% 5.9 Yes No No Yes Yes
9e 4.5% 1.6 Yes Yes Yes Yes Yes
9f 0.7% 12.2 No No No No No
9g 6.7% 2.4 Yes Yes Yes Yes Yes
9h 2.0% 5.4 Yes No No Yes Yes
9i 2.4% 4.4 Yes No Yes Yes Yes
9j 1.5% 8.2 No No No No No
9k 1.4% 3.4 Yes No No Yes Yes
9l 2.4% 5.6 Yes No No Yes Yes
9m 4.7% 5.3 Yes No Yes Yes Yes
10a 5.4% 10.7 No No No No No
10b 3.3% 2.8 Yes No Yes Yes Yes
10c 0.8% 7.8 No No No No No
10d 1.3% 2.7 Yes No Yes Yes Yes
11a 0.7% 5.8 No No No No Yes
11b 2.2% 8.1 No No No No Yes
11c 1.3% 2.4 Yes No Yes Yes Yes
11d 1.3% 0.4 Yes Yes Yes Yes Yes
11e 1.0% 3.2 Yes No No Yes Yes
11f 7.3% 6.3 Yes No Yes Yes Yes
12a 3.4% 11.0 No No No No No
12b 0.2% 3.5 Yes No No Yes Yes
12c 3.4% 4.4 Yes No Yes Yes Yes
12d 7.0% 3.7 Yes No Yes Yes Yes
12e 1.4% 3.3 Yes No No Yes Yes
12f 3.9% 12.9 No No No No No
12g 8.0% 3.0 Yes Yes Yes Yes Yes
13a 7.5% 6.8 Yes No No Yes Yes
13b 8.9% 5.8 Yes No Yes Yes Yes
13c 4.0% 3.0 Yes Yes Yes Yes Yes
Stormwater Management Plan
City of Port Townsend
Table 4-3. Catchment Area Peak flows and Maximum Required Drainage Conveyance (continued)
January 2019│ 553-2836-004 4-15
Catchment
Node
Estimated
Slope (ft/ft)
Future 25-year
Peak Flow (cfs)
Pass
Criteria for
12" Pipe
Pass Criteria
for 2' Ditch
Pass
Criteria for
4' Ditch
Pass
Criteria for
6' Ditch
Pass
Criteria for
8' Ditch
14 3.3% 8.6 No No No No Yes
15a 4.7% 5.0 Yes No Yes Yes Yes
15b 4.7% 1.7 Yes Yes Yes Yes Yes
15c 0.9% 1.5 Yes Yes Yes Yes Yes
16a 0.1% 4.9 Yes No No No Yes
16b 1.7% 5.0 No No No No Yes
16c 2.5% 1.4 Yes Yes Yes Yes Yes
17a 6.3% 4.2 Yes No Yes Yes Yes
17b 3.0% 4.2 Yes No Yes Yes Yes
18a 3.4% 5.1 Yes No No Yes Yes
18b 4.1% 3.3 Yes No Yes Yes Yes
4.2.4.3 Drainage System Sizing for Non-Standard Catchments
Table 4-4 lists the catchment areas where the 25-year peak flow in the catchment exceeds the minimum
pipe or ditch size capacity (catchments with “no” in Table 4-3) and may require a larger culvert or ditch
section for drainage in the catchment. The required screening-level pipe or ditch size is shown. It should
be noted that the longest path of drainage for this analysis may not include all of the drainage from the
catchment, and the peak flows are actually lower. When applying the screening-level data to a specific
catchment or drainage path, Table 4-3 should be reviewed to determine if pipe up-sizing is needed.
Figure 14a or 14b can be used if reduced peak flows are known. Generally, if the proportion of the
catchment actually draining to the pipe or ditch location is known, the peak flows shown in Table 4-3
can be adjusted by that proportion. In catchments that exceed the maximum ditch width of 8 feet, the
ditch should be piped using the size shown.
In addition, the peak flows shown are for uncontrolled future runoff. In reality, individual sites will be
infiltrating runoff to the maximum practical extent and larger developments will control flows, so the
actual accumulated peak flows will be lower. The approach to on-site controls to the maximum
practicable extent is shown in Appendix F. Site and project-specific analysis can be used for sizing;
however, future conditions should be applied and the same modeling assumptions used.
Table 4-4. Drainage Facility Size Estimates for Drainage Paths Exceeding Minimum Conveyance Sizing
Catchment Future 25-year Peak
Flow (cfs)
Pass Criteria for 12" Pipe or 2’
Ditch?
Predicted Pipe Size
(in)
Minimum Ditch bottom
Size
2 7.3 No 6.4
4c 9.3 No 15 10.2
4f 10.1 No 15 12.0
4g 10.1 No 18 13.4
4i 7.4 No 15 10.6
4k 8.7 No 18 13.4
Stormwater Management Plan
City of Port Townsend
Table 4-4. Drainage Facility Size Estimates for Drainage Paths Exceeding Minimum Conveyance Sizing
(continued)
4-16 January 2019│ 553-2836-004
Catchment Future 25-year Peak
Flow (cfs)
Pass Criteria for 12" Pipe or 2’
Ditch?
Predicted Pipe Size
(in)
Minimum Ditch bottom
Size
4l 18.5 No 18 18.5
5a 2.6 No 3.1
5b 4.4 No 8.1
6a 8.7 No 15 11.5
7a 2.0 No 3.0
7c 6.9 No 15 9.9
7d 3.3 No 2.5
8a 8.9 No 15 9.9
8b 8.8 No 7.7
8c 6.8 No 6.0
8f 4.2 No 2.8
8i 3.0 No 3.9
8j 2.0 No 5.7
8k 2.0 No 3.5
9b 16.3 No 18 21.3
9c 3.9 No 3.0
9d 5.9 No 4.6
9f 12.2 No 24 27.7
9h 5.4 No 7.0
9i 4.4 No 5.1
9j 8.2 No 15 12.6
9k 3.4 No 5.2
9l 5.6 No 6.6
9m 5.3 No 4.3
10a 10.7 No 15 8.5
10b 2.8 No 2.6
10c 7.8 No 18 16.5
10d 2.7 No 4.2
11a 5.8 No 15 13.0
11b 8.1 No 15 10.2
11c 2.4 No 3.7
11e 3.2 No 5.8
11f 6.3 No 6.2
12a 11.0 No 15 11.2
12b 3.5 No 14.7
12c 4.4 No 4.2
Stormwater Management Plan
City of Port Townsend
Table 4-4. Drainage Facility Size Estimates for Drainage Paths Exceeding Minimum Conveyance Sizing
(continued)
January 2019│ 553-2836-004 4-17
Catchment Future 25-year Peak
Flow (cfs)
Pass Criteria for 12" Pipe or 2’
Ditch?
Predicted Pipe Size
(in)
Minimum Ditch bottom
Size
12d 3.7 No 2.3
12e 3.3 No 5.0
12f 12.9 No 15 12.3
13a 6.8 No 4.4
13b 5.8 No 3.4
14 8.6 No 15 8.8
15a 5.0 No 4.1
16a 4.9 No 29.5
16b 5.0 No 15 7.0
17a 4.2 No 2.8
17b 4.2 No 4.3
18a 5.1 No 5.0
18b 3.3 No 2.7
4.2.4.4 Drainage System Sizing for Basin Reaches
Most of the 19 basins in the plan are defined around a principal drainage course that can convey
stormwater runoff to the receiving waters. The drainage reaches, defined and named for the catchment
in which they convey stormwater, are connected together and convey stormwater, adding the
cumulative flows from upstream of the catchment nodes (see Figure 11). Figure 15 shows the drainage
path for connected reaches.
Table 4-5 lists the peak flows at node points (see Figure 11) at the downstream end of the reach in the
catchment for which it is named and the catchments contributing runoff to these nodes. This
information is used for sizing culverts that are placed in the longer, connected reaches (usually CDCs and
KDs), such as at road crossings, or for storm drains and roadside ditches in the road drainage system
that conveys area-wide runoff. It should be noted that the culvert sizes shown are for uncontrolled
future development flow and that actual flows in the future may be lower. Also, the flow rates can be
used to size different types of structures.
Table 4-5. Peak Flows in Reaches for Structure Sizing
Reach/Node Catchments
Contributing to Node
Estimated
Slope
(ft/ft)
Future 25-year
Peak Flow (cfs)
Predicted
Pipe Size (in)
Required
Channel Width
(ft)
4k 4k 7.4% 8.7 12 <1.0
4l 4k, 4l 3.6% 27.2 24 2.8
4i 4k, 4l, 4i 1.7% 34.6 30 6.8
4h 4k, 4l, 4i, 4h 5.3% 36.2 24 3.3
4j 4k, 4l, 4i, 4h, 4j 2.0% 37.0 30 6.7
Stormwater Management Plan
City of Port Townsend
Table 4-5. Peak Flows in Reaches for Structure Sizing (continued)
4-18 January 2019│ 553-2836-004
Reach/Node Catchments
Contributing to Node
Estimated
Slope
(ft/ft)
Future 25-year
Peak Flow (cfs)
Predicted
Pipe Size (in)
Required
Channel Width
(ft)
4g 4k, 4l, 4i, 4h, 4j, 4g 2.0% 47.1 30 8.9
4f 4f 0.5% 10.1 24 2.8
4e 4e, 4f 2.5% 12.4 18 <1.0
5c 5c 3.3% 2.3 12 <1.0
5d 5c, 5d 6.7% 5.3 12 <1.0
5a 5c, 5d, 5a 2.1% 7.9 15 <1.0
7e 7a, 7c, 7e, 7d 1.7% 13.1 18 <1.0
8b 8b 4.2% 8.8 15 <1.0
8c 8c 1.0% 6.8 18 <1.0
8i 8i 3.0% 3.0 12 <1.0
9b 9j, 9h, 9b 2.1% 29.9 24 4.9
9c 9j, 9h, 9b, 9c 4.1% 33.7 24 3.6
9e 9l, 9e 4.1% 7.3 12 <1.0
11a 11a 0.7% 5.8 18 <1.0
11c 11a, 11c 1.3% 8.2 18 <1.0
11b 11a, 11c, 11b 2.2% 16.3 24 1.7
11e 11a, 11c, 11b, 11e 1.0% 19.5 24 4.5
11f 11f 7.3% 6.3 12 <1.0
16a 16a 7.0% 4.9 12 <1.0
16b 16b 1.5% 5.3 15 <1.0
This analysis was also used to evaluate the largest potential threats to the roadway drainage system that
carries area-wide runoff. For reaches in catchments with long segments in the built system, additional
analysis was prepared to determine where future runoff would exceed the minimum ditch and pipe
thresholds (Figure 16). Segments where the ditch or pipe size would increase are shown in Table 4-6
Table 4-6. Peak flows in Reaches for Long-Path Conveyance Sizing
Node Catchments
Contributing to Node
Estimated
Slope (ft/ft)
Future 25-year
Peak Flow (cfs)
Predicted
Pipe Size (in)
Predicted
Ditch Size
(ft)
9h 9h 2.0% 5.4 15 <1.0
9b 9h, 9b 2.1% 21.6 24 3.1
8a/ 9l 9h, 9b, 8a, 9l 2.8% 36.2 24 5.2
8f 9h, 9b, 8a, 9l, 8f 6.2% 40.4 24 3.5
10a 10a 5.4% 10.7 15 <1.0
9k 10a, 9k 1.4% 14 24 2.0
10c 10a, 9k, 10c 1.4% 21.8 24 4.2
10d 10a, 9k, 10c, 10d 1.4% 24.5 24 4.9
((
(
(
(
(
((
((
(
(
(
(
(
(
(
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Kah Tai Lagoon
ChineseGardens
HastingsPond
WinonaWetland
Tibbal'sLake
FroggyBottoms
LevinskiWetland
UmatillaAve.
Port Townsend Bay
Strait of Juan de Fuca
Admiralty Inlet
BlueHeron
BuckmansLake
Glaspell
D i s c o v e r y R d .Water S
t
.
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a
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K
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Mc
P
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t
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W St.
Sheridan
S
t
.
Redw
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.
Fir
S
t
.
Wa
l
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S
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14th St.
J
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s
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S
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.
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2 3
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6
7
5
8 13
12 12
10
9
11
16
17
15
18
1
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Figure 16
Roadway Drainage for LongPath Conveyance Sizing
0 0.25 0.5 0.75 1
Miles
Long Path Roadways
Q:
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Potential Wetlands
Wetlands
Features
Critical Drainage Corridors
Key Drainageways
100 Year Flood
City Limits
Drainage Basins(19
2019 Stormwater Management Plan Page 4 - 19
Stormwater Management Plan
City of Port Townsend
January 2019│ 553-2836-004 4-21
The greatest threats to the overall drainage system can be predicted by finding the node points with the
greatest peak flow change that could occur with full development. Table 4-7 shows the greatest percent
change in peak flows at the key node points. Table 4-5 can be used for sizing future drainage structures
at full build-out.
Table 4-7. Peak Flow Increase at Key Nodes due to future Development
Node
Catchments
Contributing to
Node
Estimated
Slope
(ft/ft)
Existing
25 year
(cfs)
Future 25-year
Peak Flow (cfs)
Percent
change
4k 4k 7.4% 3.8 8.7 56%
4l 4k, 4l 3.6% 15.4 27.2 43%
4i 4k, 4l, 4i 1.7% 19.0 34.6 45%
4h 4k, 4l, 4i, 4h 5.3% 20.1 36.2 44%
4j 4k, 4l, 4i, 4h, 4j 2.0% 20.8 37.0 44%
4g 4k, 4l, 4i, 4h, 4j, 4g 2.0% 25.4 47.1 46%
4f 4f 0.5% 3.8 10.1 62%
4e 4e, 4f 2.5% 5.2 12.4 58%
5c 5c 3.3% 1.0 2.3 57%
5d 5c, 5d 6.7% 1.5 5.3 72%
5a 5c, 5d, 5a 2.1% 2.2 7.8 72%
7e 7a, 7c, 7e, 7d 1.7% 7.3 13.1 44%
8b 8b 4.2% 4.1 8.8 53%
8c 8c 1.0% 3.8 6.8 44%
8i 8i 3.0% 1.1 3.0 63%
9b 9j, 9h, 9b 2.1% 15.9 29.9 47%
9c 9j, 9h, 9b, 9c 4.1% 18.0 33.7 47%
9e 9l, 9e 4.1% 4.1 7.3 44%
11a 11a 0.7% 3.9 5.8 33%
11c 11a, 11c 1.3% 5.2 8.2 37%
11b 11a, 11c, 11b 2.2% 8.9 16.3 45%
11e 11a, 11c, 11b, 11e 1.0% 11.1 19.5 43%
11f 11f 7.3% 4.5 6.3 29%
16a 16a 7.0% 3.2 4.9 35%
16b 16b 1.5% 2.5 5.3 53%
4.2.5 Drainageway Potential Impact Assessment
Because there are no streams or typical natural drainageways in the City, it is difficult to use metrics
commonly used for evaluating potential impacts such as flow-frequency increases or stream hydrology
changes (i.e., pulse counts and duration, flashiness indices). The existing natural drainage system,
represented in the City by Levels 1, 2a (CDCs) and 2b (KDs) were evaluated to determine if future
physical impacts to the natural drainage system could be expected due to anticipated growth and build-
Stormwater Management Plan
City of Port Townsend
4-22 January 2019│ 553-2836-004
out. The metric chosen for screening CDCs and KDs is based on the potential for exceeding channel
erosion thresholds that could cause the natural earthen channels found in the CDCs and KDs to erode
(USDA 2007). If future uncontrolled peak flows exceed the velocity threshold for the 25-year peak flow,
those affected CDCs and KDs are included in the Section 6 implementation plan as needing additional
hydrologic evaluation (i.e., peak flows may be lower due to stormwater controls or they nearly meet the
25-year threshold) or are threatened by future development and may require additional basin controls.
For the analysis, a typical standard CDC or KD channel section was defined (10-foot bottom, 3:1 side
slopes, 1-foot flow depth as shown in Appendix D) and reach-specific slopes were used. Channel reaches
that exceed the selected velocity threshold of 3.75 feet/second at the respective flow return frequency
are shown in Table 4-8 and Figure 17. The detailed channel conveyance and erosion analysis is provided
in Appendix D. The reaches not shown on the table but included in Figure 17 all pass the threshold
value.
Table 4-8. CDC and KD Velocity Thresholds
Reach
Catchments
Contributing to
Reach
Estimated
Slope
(ft/ft)
Future 25-
year Peak
Flow (cfs)
Estimated
Velocity for
10-year
Storm
Event
(ft/sec)
Estimated
Velocity for
25-year
Storm
Event
(ft/sec)
Estimated
Velocity for
50-year Storm
Event (ft/sec)
Estimated
Velocity for
100-year
Storm
Event
(ft/sec)
4l 4k, 4l 5.2% 27.2 4.21 4.47 4.59 4.74
4i 4k, 4l, 4i 1.2% 34.6 2.80 2.96 2.74 3.13
4h 4k, 4l, 4i, 4h 1.2% 36.2 2.84 3.00 3.07 3.17
4g 4k, 4l, 4i, 4h, 4j, 4g 6.5% 47.1 5.50 5.79 5.93 6.11
5d 5c, 5d 7.8% 5.3 2.69 2.82 2.94 3.06
5a 5c, 5d, 5a 1.9% 7.9 1.73 2.09 2.15 2.24
5b 5c, 5d, 5a 1.6% 7.9 1.88 1.98 2.04 2.12
9c 9j, 9h, 9b, 9c 8.5% 39.4 5.47 5.65 5.76 5.97
11b 11a, 11c, 11b 3.6% 16.3 3.18 3.32 3.38 3.51
11e 11a, 11c, 11b, 11e 5.2% 19.5 3.83 3.98 4.06 4.22
The reaches shown which exceed the 25-year 3.75 feet/second velocity threshold were further
examined for their location in the system and their actual potential threat. The Basin 4 reaches (4l and
4g) have fairly steep segments that account for the velocity failure. The change in runoff from
development is moderate (see Table 3-6) and there is extensive storage in wetlands throughout the
system. This is a lower priority for future analysis of additional stormwater controls or a regional system.
Reaches 9c and 11e have a higher potential for future impacts and are included in the implementation
plan as higher priority for additional analysis or regional controls. The remaining CDCs and KDs should
continue to be inspected and reviewed for observed impacts.
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Drainage Basins
Wetlands
Potential Wetlands
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Critical Drainage Corridors
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CDCs & KDsHigh Velocity Reaches
Figure 17
2019 Stormwater Management Plan Page 4 - 23
Stormwater Management Plan
City of Port Townsend
January 2019│ 553-2836-004 4-25
4.2.6 Potential Impacts to Closed System Wetlands
Depending on their size and the relative size of the drainage area, wetlands may be sensitive to
impervious surface changes in the basin. The drainage basins with discharges to wetlands—Basins 4
through 9—were assessed for potential impacts from new development. The analysis approach was
based on the 2005 SWMMWW Appendix 1-D and is summarized in Appendix D. New impervious
surfaces increase runoff to wetlands, potentially affecting peak stages and stage duration that can
change the wetland. Wetlands with surface outlets are less likely to change, while closed wetlands with
no surface outlet are more susceptible to change.
For the wetland impact potential analysis, an impact level of 1-foot increase was used, and the area of
new impervious surface in the basin that would result in this change was determined. The results are
shown in Table 4-9. Basins 6 and 8 show that potential impacts from new basin development could
occur. The wetland (Froggy Bottoms) in Catchment 6a has an outlet, so the potential for impact is
lessened. The approach to further evaluating potential impacts or mitigation of impacts is to reduce
allowable new development in those areas, provide additional controls through infiltration potential,
increase the protection area around the wetland to allow it to increase in size, or provide for a high-level
overflow of the wetlands—as is available in the Basin 6 wetland. Figure 18 shows the potential increased
footprint for wetlands in basins 5, 6, 7, and 8 at full buildout with no development controls.
Table 4-9. Potentially Impacted Wetlands
Wetland Name Wetland Area
(ac.)
Allowable Additional
Impervious Percent
Estimated Future Impervious
Percent Change
Wetland 4a 46.5 30 >30
Wetland 5b 5.2 5 >70
Wetland 6a 1.3 3 >70
Wetland 7f 0.9 2 >40
Wetland 8b 5.3 5 >40
Wetland 9a 46.4 37 >30
4.3 Drainage System Stormwater Improvements
The existing constructed drainage system is predominantly part of the road system, which collects and
conveys runoff from roadways and development to natural drainage areas and receiving waters.
Figure 15 shows the key drainage paths and Table 3-5 shows the estimated peak flow rates at catchment
node points (see Figure 11). In addition to drainage capacity, the roadway drainage system is also the
predominant location for existing incidental stormwater quality via runoff flowing through existing
grassy ditches or swales. As described in the previous section, modeling the entire drainage system for
capacity was not completed due to the relative homogeneity of the drainage areas and subsequent
runoff rates (see Table 3-5). Instead “typical” conveyance size for the design storm flow capacity was
defined and the findings can be applied to all drainage conveyance channels or ditches.
The prioritization for future implementation will be made by City staff based on known needs. For
example, the first priority is to upgrade roadside “ditches” to properly performing swales based on
conveyance needs and road condition. Often inadequate roadside drainage leads to premature road
failure. Level 4a roadways have not been assessed for existing capacity, which would be done by
applying the catchment flow results to each drainage reach. Generally, culverts must be a minimum of
Stormwater Management Plan
City of Port Townsend
4-26 January 2019│ 553-2836-004
12-inches in all systems except Discovery Road, Sims Way, and Hastings Avenue or ditches less than the
sizes indicated would be considered deficient.
Water quality sizing and the typical water quality roadway ditch section is smaller than that needed for
the peak conveyance flow. Upgrades to meet the minimum conveyance capacity will address water
quality. Road improvements are usually required to retrofit for flow control and water quality; having
funding available to achieve this will be a key part of the implementation plan. If new storm sewers are
proposed or constructed in Level 4a or 4b road segments, water quality treatment for that roadway
segment will be required per the Manual, usually in the form of bioretention or modular treatment.
The Level 4b road system will also need upgrades, although their role is to provide local drainage to
other levels, not to provide regional drainage. Consequently, the maximum design flow rates are
expected to be smaller. The minimum pipe size is 12-inches, which can handle all likely peak flows from
the Level 4b roadways (see Table 4-3). The minimum standard ditch section for conveyance is also
approximately the same as the required biofiltration section for these flows, therefore treatment will be
provided.
4.4 Roadway Inventory for Upgrade Opportunities
The Level 4a roadways were inventoried to determine where space was available for future drainage or
water quality improvements could be made. The inventory includes information on right-of-way and
pavement width, sidewalks, curb and gutter or ditch, and existing swales. Additional information for
each roadway segment is included in Appendix E.
BlueHeron
22' Contour
41stSt.
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Figure 18
Future Impact EstimateWetland Footprints
0 100 200 300 400
Feet
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2019 Stormwater Management Plan Page 4 - 27
Stormwater Management Plan
City of Port Townsend
January 2019│ 553-2836-004 5-1
5. CAPITAL PROJECTS PLAN
Capital projects are identified in basin plans to describe, estimate, and provide a basis for design of
proposed constructed facilities to address the stormwater needs identified in the plan. Most stormwater
capital project plans include:
• Solutions for chronic, known flooding and drainage problems;
• Typical concept designs and unit costs for improvements, such as roadway conveyance and
water quality retrofitting;
• Regional or neighborhood stormwater management facilities to support existing and future
development;
• Basin-specific stormwater retrofit projects to retroactively address stormwater impacts from
existing development;
• Basin planning studies; and
• Capital acquisition, such as land or equipment
Preliminary engineering is prepared for the constructed capital projects to develop planning-level cost
assumptions for programming and planning these projects. The implementation plan to prioritize and
schedule the capital projects is described in Section 6.
5.1 Proposed Capital Projects
A meeting between Parametrix and the City on June 20, 2017, revealed several known problem areas in
varied locations within the city limits. Five capital projects were identified by the City to be included in
the Plan, covering some of the typical categories listed above (Figure 19). Each problem area was visited
in the field on November 2, 2017 to collect data to aid in determining appropriate solutions. Preliminary
solutions were designed using information gathered in the field and in discussions with the City.
A brief description of the problem and proposed solution for each project is shown in Table 5-1. Project
plan sheets showing the preliminary design approach and planning-level costs are provided in Appendix G.
The total project costs are based on the conceptual plan layouts shown in Appendix G. Material
quantities, labor, mobilization costs (approximately 15 percent of subtotal), traffic control costs (a
minimum of 2 percent of the subtotal), and erosion and sedimentation control (a minimum of 2 percent
of the subtotal) were estimated. In addition, environmental permitting and documentation,
administration, and design and management costs have been considered. Lastly, a contingency factor of
30 percent has been added to the final cost.
Stormwater Management Plan
City of Port Townsend
5-2 January 2019│ 553-2836-004
Table 5-1. Capital Projects
Project No. and Title
Estimated
Cost Problem Description Proposed Solution
1 16th Street –
Sheridan Street to
Landes Street
$187,000 Site consists of an undeveloped right-of-
way. Stormwater from Sheridan Street,
14th Street, and 16th Street is conveyed
through a closed system to an outfall
located at 16th Street and Gise Street,
where severe erosion has occurred in
16th Street.
Install a closed conveyance system along the
17th Street Right-of-way between Gise
Street and Hill Street while maintaining
some flow in the 16th Street corridor.
2 12th Street ROW,
Logan Street, and
14th Street
$614,000 Several flooding issues occur near the
wetland located at McPherson Street and
the 12th Street right-of-way and at 14th
and McPherson Streets.
Construct roadside bioswales to convey
drainage from between McPherson St and
Logan St to a new storm sewer pipe that will
convey stormwater south along Thomas St
to an existing wetland. Runoff on 14th St
from Logan St to Rosecrans St will be
conveyed through proposed bioswales
directing runoff to an existing conveyance
system that discharges to a critical drainage
area on 16th St and Gise St. Additionally, an
existing swale from the 12th St ROW will be
connected to a proposed closed storm
system that will convey stormwater south to
an existing conveyance system before
discharge to a CDC.
3 Center Street –
San Juan Avenue
to Olympic
Avenue
$432,000 There exists a low point (sump) condition
along Center St between San Juan Ave
and Spruce St, along with a lack of well-
developed roadside drainage
infrastructure, which creates flooding
issues.
Construct roadside drainage ditches and
culverts per a standard roadway section
with closed conveyance to a wetland located
south of Cedar Street.
4 Hancock Street
and 32nd Street
$188,000 Poor drainage exists along Hancock Street
and in the intersection of Hancock Street
and 32nd Street. Ponding occurs in
roadway. Catch basin connected to
sanitary sewer system exists, and City
intends to separate.
Construct bioswales per standard roadway
section with a proposed culvert beneath
32nd Street to convey drainage north and
west to a critical drainage area. Stormwater
currently captured by an existing catch basin
tied existing sanitary system at 31st Street
and Hancock Street to be conveyed west
along 31st Street to critical drainage area.
5 Lawrence Street
at intersections of
Polk Street, Taylor
Street, and Tyler
Street
$858,000 Storm sewer catch basins located on
Lawrence Street at the intersections of
Polk Street, Taylor Street, and Tyler Street
are currently directly connected to
sanitary sewer system. City intends to
separate stormwater from sanitary sewer
system.
Construct new stormwater conveyance
system with trunk-line running north along
Lawrence Street with lateral pipes and catch
basins to collect stormwater on both sides
of Lawrence Street. A downstream capacity
analysis is necessary to verify the
practicability of this approach.
6 Rainier Street
Regional
Stormwater
Project
Underway in 2019
7 Logan Street
Stormwater Pond
Overflow
Underway in 2019
Total Cost $2,279,000
((
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Kah Tai Lagoon
ChineseGardens
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WinonaWetland
Tibbal'sLake
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LevinskiWetland
UmatillaAve.
Glaspell
D i s c o v e r y R d .Water S
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.
F St.
Mc
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S
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.
49th St.
W St.
Sheridan
S
t
.
Redw
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J
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Cook
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Ave.
Hastings Ave.
19th St.
2 3
14
6
7
5
8 13
12 12
10
9
11
16
17
15
18
1
19
4
Capital ProjectsFigure 19
0 0.25 0.5 0.75 1
Miles
16th Street
12th Street
Center Street
Hancock Street
Lawrence Street
Regional Facility Logan Pond
Drainage Basins
Capital Projects
Potential Wetlands
Wetlands
Features
Critical Drainage Corridors
Key Drainageways
100 Year Flood Area
(19
City Limits
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2019 Stormwater Management Plan Page 5 - 3
Stormwater Management Plan
City of Port Townsend
January 2019│ 553-2836-004 5-5
5.2 Proposed Recurring Capital Projects
The plan has considered the potential need for drainage improvements in the Level 4a and 4b road
systems. Deficiencies and priorities in these systems will be developed by an on-going and regular
evaluation by City maintenance and engineering staff. Funds to make repairs are needed to address the
program developed by staff. A lump cost was identified; the funding is identified in Table 5-2.
Table 5-2. Other Built Capital Projects
Project Title
Estimated
Cost total
over 6 years Distribution
1 Roadside
Conveyance
Improvements –
Major Collectors
and Minor Arterials
(Level 4a)
$300,000
Allocate $300,000 every 6 years starting
in 2021, to align with street upgrade
projects.
2 Roadside
Conveyance
Improvements –
Local Access Streets
(level 4b)
$100,000
Allocate $100,000 every 6 years starting
in 2022.
Total Cost $400,000
Stormwater Management Plan
City of Port Townsend
January 2019│ 553-2836-004 6-1
6. IMPLEMENTATION
The implementation plan summarizes specific plan actions, capital projects, policy needs, an
implementation schedule, and an itemized cost for each item. There are few outside drivers to plan
implementation, therefore it is likely to be executed as resources are applied or come available. Plan
costs for capital projects are estimated and a suggested annual cost for implementing recurring projects
and upgrades is provided. However, no final timeline is included for delivery of capital projects because
available funding stream information is still under evaluation and is not available.
6.1 Capital Plan Priorities and Schedule
Capital projects are identified in basin plans to address known flooding problems; capital improvements,
upgrades or repairs; new facilities, such as regional stormwater ponds or retrofitting projects; land
purchase and protection; and restoration or mitigation. The SWMP is primarily addressing flooding
problems and future projects to improve street drainage. Table 6-1 shows the relative ratings and
ranking for implementation priority.
6.1.1 Capital Projects for Existing Flood Control
The Capital Projects Plan includes 20 proposed capital projects. These projects include repair and
minimization of existing flooding problem areas; new regional facilities for retrofitting and new
development; and upgrades to existing facilities. The projects were ranked and prioritized according to
four categories:
• Area benefitted—the number of parcels or land area served
• Need/severity—the need for the solution or project to facilitate other work and the seriousness
of the problem
• Cost—low or no cost or many benefits for cost
• Opportunity—the project is ready to go, the land is owned by the City, and there are no
concerns or issues with implementation
Table 6-1. Capital Projects Rankings and Priority
Item
Number
Project
Number Project Name
Area
Benefitted
Need or
Severity Cost/Benefit
Opportunity or
Constraints
Rank
Total Rank
6.1.1 1 16th Street – Sheridan
Street to Landes Street
MED HIGH MED LOW 8 3
6.1.2 2 12th Street ROW,
Logan Street, and 14th
Street
LOW HIGH LOW LOW 6 7
6.1.3 3 Center Street – San
Juan Avenue to
Olympic Avenue
MED LOW HIGH MED 8 3
6.1.4 4 Hancock Street and
32nd Street
LOW MED MED MED 7 6
Stormwater Management Plan
City of Port Townsend
Table 6-1. Capital Projects Rankings and Priority (continued)
6-2 January 2019│ 553-2836-004
Item
Number
Project
Number Project Name
Area
Benefitted
Need or
Severity Cost/Benefit
Opportunity or
Constraints
Rank
Total Rank
6.1.5 5 Lawrence Street at
intersections of Polk
Street, Taylor Street,
and Tyler Street
MED MED MED MED 8 3
6.1.6 6 Rainier Street Regional
Stormwater Project
HIGH MED HIGH MED 10 1
6.1.7 7 Logan Street
Stormwater Pond
Overflow
HIGH LOW MED HIGH 9 2
N/A means projects not ranked.
6.1.2 Non-Capital Recurring Projects
Non-capital recurring projects, in the context of this plan, means minor, local, ongoing improvements,
upgrades, repairs, and replacements of the drainage system. They are often completed as part of a
larger project or are identified by a complaint. In addition, it can include systematic improvements or
upgrades to a part of the system that has been neglected or is changing due to new development. An
example of this is the Level 4b roadway network.
The analyses prepared in Section 4 identified future drainage system need on 4a and 4b roadways, on
continuous reaches of roadway drainage, crossings for long drainage reaches, and potential impacts on
CDCs and KDs. The analysis identified threats and areas for additional study; specific needs and found
problem areas was outside the scope of this plan. However, planning for future needs based on the
identified deficiencies is included in this implementation plan.
Table 6-2. Summary of the Roadway Drainage Improvement Plan
Item No.
Plan
Section
No. Action What it is Quantity
Effort and
Cost
Timeline
Priority
6.1.8 4.2.4 Future system
upgrades in
Level 4a
Provide a fund to
make roadway
drainage
improvements when
acute problems occur
in the Level 4a system
3 drainage
upgrades per year
that require new
pipes or
structures.
Moderate Annual
6.1.9 4.2.4 Future system
upgrades in
Level 4b
Provide a fund to
make roadway
drainage
improvements when
acute problems occur
in the Level 4a system
500 feet of ditch
drainage upgrades
per year and 500
feet of 12” pipe
per year.
Moderate Annual
6.1.10 4.2.3 Future system
upgrades in
Level 1-2
Provide a plan and
fund to make
drainage
improvements when
acute problems occur
1 Plan. Low Annual
Stormwater Management Plan
City of Port Townsend
Table 6-2. Summary of the Roadway Drainage Improvement Plan (continued)
January 2019│ 553-2836-004 6-3
Item No.
Plan
Section
No. Action What it is Quantity
Effort and
Cost
Timeline
Priority
6.1.11 4.2.4.4 Long-path road
drainage
upgrade analysis
Review the structures
and ditch in the long-
path drainage
systems. Prepare a
needs assessment and
add to Capital
Projects Plan
One study Low Early and
Moderate
6.1.12 4.2.4.4 Long-path road
drainage
upgrades
Implement identified
capital projects; up to
4 anticipated
1 drainage
upgrade per year
High Annual
starting in
Year 5;
Moderate
6.1.13 4.2.5 CDC and KD
impact
mitigation
analysis
Review the 4 CDCs or
KDs with potential
impacts. Identify
actual threat and
prepare scenarios for
mitigation
One study Low Early and
Moderate
6.1.14 4.2.5 CDC and KD
impact
mitigation
Implement study
results
One Plan High Year 3 and
Low
6.1.15 4.2.6 Closed Wetland
System impact
and mitigation
analysis
Review the 4
wetlands with
potential impacts.
Identify actual threat
and prepare scenarios
for mitigation
One study Moderate Year 3 and
Moderate
6.1.16 4.2.6 Closed Wetland
System impact
mitigation
Implement study
results
One Plan High Year 5 and
Low
6.2 Stormwater Control Standards and Policies
Basin planning is used to assess existing and future threats to the City’s ability to provide a level of
service to the community to protect the resource, minimize flooding and drainage problems, and
maintain safety. The nature of most threats are new development that increases runoff; changes in flow
paths and capacity; and/or a degrading and failing existing system that is not properly maintained. This
section describes measures to protect the existing system from new development.
6.2.1 Stormwater Control from New Development
Runoff from new development is usually controlled by using a system to minimize runoff changes from a
site or by constructing stormwater controls that serve multiple sites, such as a subdivision or regional
stormwater facility. Most stormwater in western Washington in National Pollution Discharge Elimination
System (NPDES) Municipal Permit communities is controlled by following Ecology’s SWMMWW or an
approved equivalent manual, which applies to new development or significant redevelopment
Stormwater Management Plan
City of Port Townsend
6-4 January 2019│ 553-2836-004
proposals. The City is using the 2005 SWMMWW (the City is not an NPDES community). A review
comparing the 2005 and 2014 SWMMWWs was made and the findings are shown in Appendix H. We
recommend that the City continue to use the 2005 SWMMWW for new development and
redevelopment that triggers review under the manual.
As described earlier, the City has areas with platted lots, often 5,000 square feet in size and rights-of-
way that are not developed. Proposed development or redevelopment of these lots may or may not
exceed SWMMWW thresholds for stormwater control. As described in the analysis in Section 4,
uncontrolled development of these areas does result in increased flows and can cause impacts. These
areas should control runoff to the maximum extent practicable (MEP). Policies and guidelines for
landowners with development projects that do not trigger SWMMWW thresholds are included in
Appendix F.
6.2.2 Drainage System Protection
Receiving waters (Level 1), Critical Drainage Corridors, and Key Drainageways (Level 2) were defined in
Section 4. These are areas that could be impacted by future uncontrolled stormwater or direct impacts
to their conveyance pathway. The following describes protection for Level 1 and 2 drainage, example
guidelines, and measures for protecting these resources.
Level 1 Receiving Waters
Protection:
• Most or all Level 1 receiving waters have protections through critical areas ordinances
and floodplain management.
Guidelines:
• Ordinance and Code should have language to protect the conveyance, flood control,
water quality, and hydrologic aspects of the resource.
• Provide measures for mitigating and providing conveyance, flood control, and water
quality aspects of Level 1 at road crossings in unopened rights-of-way.
Evaluation and Improvements:
• Review ordinances and protection guidelines
• Prepare guidance for providing conveyance, flood control, and water quality measures
when Level 1 resource impacts cannot be avoided.
Level 2 Natural Drainage via Critical Drainage Corridors or Key Drainageways
Protection:
• CDC are protected by the critical areas ordinance
• Key Drainageways are defined and protected through the stormwater code Guidelines:
• CDC Ordinance and Code should have language to protect the conveyance, flood
control, water quality, and hydrologic aspects of the resource.
• KD should identify and protect the conveyance, flood control, water quality, and
hydrologic aspects of the resource and provide measures to quantify and protect or
mitigate unavoidable impacts.
Stormwater Management Plan
City of Port Townsend
January 2019│ 553-2836-004 6-5
Evaluation and Improvements:
• Review and update KD maps as needed.
• Review and update the stormwater code to incorporate the regulatory framework for
protection and regulation of the KDs.
• Review and update the Engineering Design Standards (EDS) to reflect guidelines in this
Plan.
• Provide review ordinances guidelines.
• Prepare process for evaluating modifications and standards for mitigating and providing
the conveyance, flood control, and water quality aspects of Level 2 at road crossings in
unopened rights-of-way
Level 3 drainage connections, as described in Section 4.1, also need identification and protection
measures, as described below.
Level 3 Connecting Drainage
Protection:
• Level 3 drainage connections should be identified and protected through easements, fee
purchase, or other related permission to maintain and protect drainage connectivity
Guidelines:
• Create requirement and approach to identify Level 3 connections during site plan review.
• Identify and catalogue Level 3 connections for prioritization and protection
Evaluation and Improvements:
• Prioritize Level 3 connections for protection.
Level 4 drainage, which is collection and conveyance in the existing (and future) road system, requires
standards for allowable modifications, crossing standards, conveyance sizing for new roads, and
guidance for defining and upgrading deficient systems. Measures for defining and protecting this
drainage level include:
Level 4 Constructed Drainage System
Protection:
• Level 4 drainage is included in rights-of-way; no further ownership or regulation is
needed.
• Standards for right-of-way use permits
Guidelines:
• Update right-of-way use permits if needed.
• Use sizing guidelines prepared in Section 4 for pipe size, ditch size, and minimum
drainage requirements.
• Prepare Level 4b development requirements and funding strategy.
• Prepare development review and fees for Level 4b program.
• Review and update the EDS to reflect guidelines in this Plan.
Stormwater Management Plan
City of Port Townsend
6-6 January 2019│ 553-2836-004
Evaluation and Improvements:
• Inventory pipe and ditch deficiencies in Level 4a.
• Prioritize Level 4a upgrade or repair needs.
• Prioritize Level 4b upgrade and repair needs.
• Prepare a strategy for regular improvements in Level 4a and 4b.
Table 6-3. Summary of Stormwater Control and Drainage Protection
Item No.
Plan
Section
No. Action What it is Benefit
Effort and
Cost
Timeline
Priority
6.2.1 4.2.3 Adopt basin plan Guidance for
stormwater
management,
policy, land use
recommendations,
and capital
projects.
Establish basin
specific City
approaches and
priorities.
Moderate Early and High
6.2.2 Continue to use
2005 Ecology
Manual
The stormwater
manual for new
development and
redevelopment
In use and is
applicable and
appropriate to City
system
None; existing
action
N/A
6.2.3 Adopt guidance for
individual lot
stormwater controls
Adopt “maximum
extent
practicable”
stormwater
controls focused
on sites below the
stormwater
manual threshold
Stormwater
controls will be
applied that are
commensurate with
MEP and address
pre-platted lots
Low Early and High
6.2.4 4.2.3 Adopt drainage level
designations as
defined in the
SWMP in codes and
standards
A hierarchy to
define the
drainage network
to provide for
protecting,
controlling, or
improving a
segment
Streamline
development
process
Moderate Early and High
6.2.5 4.2.3 Update codes and
standards to
implement
protection measures
for Level 2b Key
Drainageways
Align Level 2b
waters with the
stormwater plan
recommendations
Have a process for
regulating Level 2b
(KDs)
Moderate Early and High
6.2.6 4.2.3 Implement
identification,
protection
measures, and
prioritization for
Level 3 drainage
Level 3 system
connects the built
system drainage
to the natural
drainage system
Connectivity will be
maintained
Moderate Year 1 and
Moderate
6.2.7 4.2.3 Implement
guidelines, permits,
inventory,
prioritization, and
Level 4 drainage
provides the built
system drainage
Connectivity will be
maintained,
drainage provided
for all development,
High Year 1 and
Moderate
Stormwater Management Plan
City of Port Townsend
Table 6-3. Summary of Stormwater Control and Drainage Protection (continued)
January 2019│ 553-2836-004 6-7
Item No.
Plan
Section
No. Action What it is Benefit
Effort and
Cost
Timeline
Priority
funding measures
for Level 4 drainage
via the road
network
a system for
upgrades is
provided
6.2.8 4.2.4 Adopt drainage
capacity analysis
and design tools
An analysis of the
general capacity
and drainage
sizing
requirements for
roadway drainage
Design calculations
and drainage needs
are standardized
across the city;
sizing is consistent
for future buildout
Low Early and High
6.2.3 Drainage System Review and Upgrades
The existing constructed drainage system is predominantly part of the road system, which collects and
conveys runoff from roadways and development to natural drainage areas and receiving waters.
Drainage capacity refers to the size and configuration of the conveyance ways and drainage systems for
conveying stormwater to receiving waters, including the Level 1, 2, and 4 drainage paths. The capacity of
the existing system was evaluated under future development conditions and the findings are provided in
Section 4. This section provides a summary of actions for continued evaluation and upgrades to the
system to repair existing deficiencies, inspect for ongoing problems, and prepare for future capacity.
Table 6-4. Summary of Drainage System Review and Upgrades
Item No.
Plan
Section
No. Action What it is Benefit
Effort and
Cost
Timeline
Priority
6.2.10 4.2.4.4 Review capacity
analysis in Table 4-5
and 4-6 for existing
system deficiencies
Analyses for the drainage
network were evaluated.
Deficiencies can be
documented.
Plan for upgrades
before flooding
occurs now or in
the future
Moderate Year 2 and
Moderate
6.2.11 4.2.4.4 Review capacity
analysis in Table 4-7
for drainage nodes
with the greatest
potential for increase
and future impacts
Analyses for future peak
flows from future
development were
determined. The highest
potential for future drainage
needs can be seen
Plan for upgrades
before flooding
occurs now or in
the future
Moderate Year 4 and
Moderate
6.2.12 4.2.5 Prepare alternative
analysis for protecting
potential future
impacts on CDCs and
KDs from future
development
Threats to the CDCs and KDs
from accumulated future
drainage increase were
defined in Table 4.8. A plan
to address alternatives is
needed
Plan for
protection and or
avoidance before
flooding or
impacts occur.
High Year 4 and
Moderate
6.2.13 4.2.5 Inspect CDCs and KDs
for observable
impacts
Threats calculated are
theoretical. Actual threats
could be observed and may
need earlier protection. A
hierarchy to define the
drainage network to provide
for protecting, controlling,
or improving a segment
Avoiding severe
impacts will be
more cost-
effective than
repairing them
Low Early and
Moderate
Stormwater Management Plan
City of Port Townsend
Table 6-4. Summary of Drainage System Review and Upgrades (continued)
6-8 January 2019│ 553-2836-004
Item No.
Plan
Section
No. Action What it is Benefit
Effort and
Cost
Timeline
Priority
6.2.14 4.2.6 Prepare alternative
analysis for protecting
potential future
impacts on wetlands
defined in Table 4-9
Threats to some receiving
water wetlands from
accumulated future
drainage were defined in
Table 4.9. A plan to address
alternatives is needed
Plan for
protection and or
avoidance before
flooding or
impacts occur.
High Year 4 and
Moderate
6.2.15 4.3 Implement guidelines,
permits, inventory,
prioritization, and
funding measures for
Level 4 drainage
Level 4 drainage provides
the built system drainage via
the road network
Connectivity will
be maintained,
drainage
provided for all
development, a
system for
upgrades is
provided
High Year 1 and
Moderate
6.2.4 Other Drainage System Protection Measures
The future impacts analysis evaluated the potential stormwater runoff changes due to the full potential
buildout of all private developable lands and unopened right-of-way. The timeline for full-build-out was
not considered; consequently, applying a timeline or priority for new or upgraded infrastructure is not
included. Priorities will be made by City staff based on ongoing observations and the capacity is provided
by the identified scope of needs outlined in the plan.
The calculations for future runoff provided in Section 4 do not consider the benefits of stormwater
measures required by the Ecology Manual, thus the results are conservative and more protective than
the standard. Development and buildout of individual lots are generally under the stormwater control
requirement thresholds in the manual, although City code will require infiltration and control to the
maximum extent practicable, therefore these results are also conservative.
Reductions in allowable land use changes or changed thresholds for required stormwater controls are
other measures the City can take to control future stormwater impact potential. The greatest potential
for change in stormwater runoff due to new, uncontrolled development is show in Table 3-6. These data
could provide a basis for where allowable land use or additional controls could be focused.
Potential stormwater runoff increase due solely to climate change were not evaluated. While increased
storm size and annual precipitation is expected (see Section 2.4), the impacts of this change on the
systems will vary. In general, the level of service may be reduced. However, the drainage system pipe
and ditch sizes are not sensitive to small changes in peak runoff, therefore the need to increase drainage
system sizes should be made on a project by project basis, using the tools provided in Section 4.2.
Drainage structure impacts due to rising sea level were outside the scope of this study and no other
existing drainage infrastructure analyses were completed.
Stormwater Management Plan
City of Port Townsend
January 2019│ 553-2836-004 6-9
Table 6-5. Summary of Other Drainage System Protection Measures
Item No. Plan
Section
No. Action What it is Benefit
Effort and
Cost
Timeline
Priority
6.2.16 Review areas
with large
expected runoff
changes using
Table 3-6.
Investigate if future
allowable land use
with large potential
runoff changes are
compatible with the
existing drainage
system or natural
system capacity.
Control impacts by
reducing land use or
providing additional
controls when
needed to protect
infrastructure or
natural resources
Moderate Year 5 and
Moderate
6.2.17 Model the
catchment peak
flows and
drainage
conveyance
capacity (Tables
4-4 through 4-8)
using future
rainfall
projections
considering
climate change
Future peak flows
from future
development may
be higher due to
climate change and
may require added
capacity.
Plan for upgrades
before flooding
occurs now or in
the future
High Year 5 and
Moderate
6.2.18 Review drainage
infrastructure
(built and
natural) that
could be
impacted by
higher sea levels
CDCs and KDs, storm
drainage systems
near the ocean, and
low elevation
wetlands could be
impacted and cause
flooding
Plan for protection
and or avoidance
before flooding or
impacts occur.
High Year 5 and
High
Stormwater Management Plan
City of Port Townsend
6-10 January 2019│ 553-2836-004
6.3 Funding and Resources
6.3.1 Capital Projects
Table 6-7 includes the cost distribution plan for the initial implementation years. Additional Information
and years is provided in Appendix I. Table 6-8 provides a summary of when staff resources are needed
for implementation.
Table 6-7. Summary Cost Plan – Capital (2019-2024)
Item
No. Title Total Cost 2019 2020 2021 2022 2023 2024
6.1.6 Rainier Street
Regional
Stormwater
Project
$ 808,000.00
$ 808,000.00
6.1.7 Logan Street
Stormwater
Pond Overflow
$ 50,000.00
$10,000.00
$ 50,000.00
6.1.1 16th Street –
Sheridan Street
to Landes Street
$210,000.00
$ 60,000.00
$ 150,000.00
6.1.2 12th Street
ROW, Logan
Street, and 14th
Street
$ 550,000.00
6.1.8 Future system
upgrades in
Level 4a -
Implement
$ 600,000.00
$300,000.00
6.1.9 Future system
upgrades in
Level 4b -
Implement
$ 200,000.00
$100,000.00
6.1.4 Hancock Street
and 32nd Street
$ 180,000.00
6.1.3 Center Street –
San Juan Avenue
to Olympic
Avenue
$ 400,000.00
6.1.5 Lawrence Street
at intersections
of Polk Street,
Taylor Street,
and Tyler Street
$ 850,000.00
Stormwater Management Plan
City of Port Townsend
6-11 January 2019│ 553-2836-004
Table 6-8. Summary Cost Plan - Resources
Item No. Title
Total
Effort 2019 2020 2021 2022 2023
2024
6.2.1 Prepare Basin Plans X
6.2.3 Adopt guidance for individual lot
stormwater controls
X
6.2.4 Adopt drainage level
designations as defined in the
SWMP
X
6.2.8 Adopt drainage capacity analysis
and design tools
X
6.2.5 Review and implement
protection measures for Level 2b
receiving waters
X
6.1.9 Future system upgrades in Level
4b – Plan
X
6.1.10 Future system upgrades in Level
1-2 - Plan
X
6.1.11 Long-path road drainage upgrade
analysis
X
6.1.13 CDC and KD impact mitigation
analysis
X
6.2.15 Implement guidelines, permits,
inventory, prioritization, and
funding measures for Level 4
drainage
X
6.2.13 Inspect CDCs and KDs for
observable impacts
X
6.2.6 Implement identification,
protection measures, and
prioritization for Level 3 drainage
X
6.2.10 Review capacity analysis in
Tables 4-5 and 4-6 for existing
system deficiencies
X
6.1.15 Closed Wetland System impact X
6.2.11 Review capacity analysis in Table
4-7 for drainage nodes with the
greatest potential for increase
and future impacts
X
6.2.12 Prepare alternative analysis for
protecting potential future
impacts on CDCs and KDs from
future development
X
Stormwater Management Plan
City of Port Townsend
Table 6-8. Summary Cost Plan – Resources (continued)
6-12 January 2019│ 553-2836-004
Item No. Title
Total
Effort 2019 2020 2021 2022 2023
2024
6.2.14 Prepare alternative analysis for
protecting potential future
impacts on wetlands defined in
Table 4-9
X
6.2.16 Review areas with large expected
runoff changes using Table 3-6
X
6.2.17 Review areas with large expected
runoff changes using Table 3-6
X
6.2.18 Review drainage infrastructure
(built and natural) that could be
impacted by higher sea levels
X
6.4 Summary Implementation Plan
The Basin Plan Program elements have been summarized in an implementation schedule in order of
anticipated priority and timeline in Table 6-9. This is recommended for planning purposes to determine
the relative costs and effort levels that may need to be applied. It is anticipated that some elements may
be moved up the list because of changing needs or opportunities that arise and may need to be delayed
over a longer time frame due to lack of available resources. Table 6-10 shows the 2019-2029 Capital
Program if a $6.00 surcharge and development fee are applied.
Table 6-9. Summary Implementation Schedule
Time
Item
Number Action Effort Timeline Priority
First
Actions
6.2.1 Adopt Basin Plan Moderate High
6.2.3 Adopt guidance for individual lot stormwater
controls
Low High
6.2.4 Adopt drainage level designations as defined in
the SWMP
Moderate High
6.2.9 Adopt drainage capacity analysis and design tools Low High
6.2.5 Update Codes for Level 2b Key Drainageways Moderate Moderate
Year 0-1
(2019)
6.1.6 Implement Rainier Street Regional Stormwater
Project
High High
6.2.6 Review and implement protection measures for
Level 3 Drainage
Moderate Moderate
6.1.8 Future system upgrades in Level 4a - Plan Moderate Moderate
6.1.9 Future system upgrades in Level 4b – Plan Moderate Moderate
6.1.10 Future system upgrades in Level 1-2 - Plan Low Low
6.1.11 Long-path road drainage upgrade analysis Moderate Low
6.1.13 CDC and KD impact mitigation analysis Moderate Low
Stormwater Management Plan
City of Port Townsend
Table 6-9. Summary Implementation Schedule (continued)
January 2019│ 553-2836-004 6-13
Time
Item
Number Action Effort Timeline Priority
6.2.15 Implement guidelines, permits, inventory,
prioritization, and funding measures for Level 4
drainage
High Moderate
6.2.13 Inspect CDCs and KDs for observable impacts Low Moderate
6.2.7 Implement identification, protection measures,
and guidelines for Level 4 drainage
High Moderate
Year 2
(2020)
6.1.8 Future system upgrades in Level 4a - Implement Moderate Moderate
6.1.7 Logan Street Stormwater Pond Overflow High High
6.1.9 Future system upgrades in Level 4b - Implement Moderate Moderate
6.1.10 Future system upgrades in Level 1 - Implement Low Low
Year 3
(2021)
6.1.1 16th Street – Sheridan Street to Landes Street High High
6.1.8 Future system upgrades in Level 4a - Implement Moderate Moderate
6.2.10 Review capacity analysis in Tables 4-5 and 4-6 for
existing system deficiencies
Moderate Moderate
6.1.9 Future system upgrades in Level 4b - Implement Moderate Moderate
6.1.10 Future system upgrades in Level 1 - Implement Low Low
Year 4
(2022)
6.1.1 16th Street – Sheridan Street to Landes Street
(cont.)
High High
6.1.14 CDC and KD impact mitigation – Implement study
results
High Low
6.1.15 Closed Wetland System impact Moderate Moderate
6.1.8 Future system upgrades in Level 4a - Implement Moderate Moderate
6.1.9 Future system upgrades in Level 4b - Implement Moderate Moderate
6.1.10 Future system upgrades in Level 1 - Implement Low Low
6.2.11 Review capacity analysis in Table 4-7 for drainage
nodes with the greatest potential for increase
and future impacts
Moderate High
6.2.12 Prepare alternative analysis for protecting
potential future impacts on CDCs and KDs from
future development
Moderate Moderate
6.2.14 Prepare alternative analysis for protecting
potential future impacts on wetlands defined in
Table 4-9
High Moderate
Year 5
(2023)
6.1.3 Center Street – San Juan Avenue to Olympic
Avenue
High High
6.1.5 Lawrence Street at intersections of Polk Street,
Taylor Street, and Tyler Street
High High
6.1.12 Long-path road drainage upgrades High Moderate
6.1.8 Future system upgrades in Level 4a - Implement Moderate Moderate
6.1.9 Future system upgrades in Level 4b - Implement Moderate Moderate
Stormwater Management Plan
City of Port Townsend
Table 6-9. Summary Implementation Schedule (continued)
6-14 January 2019│ 553-2836-004
Time
Item
Number Action Effort Timeline Priority
6.1.10 Future system upgrades in Level 1 - Implement Low Low
6.1.16 Closed Wetland System impact mitigation High Low
6.2.16 Review areas with large expected runoff changes
using Table 3-6.
Moderate High
6.2.17 Review areas with large expected runoff changes
using Table 3-6.
High Moderate
6.2.18 Review drainage infrastructure (built and natural)
that could be impacted by higher sea levels
High High
Year 6 Plus 6.1.2 12th Street ROW, Logan Street, and 14th Street High High
6.1.4 Hancock Street and 32nd Street High High
Stormwater Management Plan
City of Port Townsend
January 2019│ 553-2836-004 6-15
Table 6-10. Updated CIP with $6 Surcharge and Development Fee
Project Title Total Project Cost 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029‐2039
Stormwater General Projects
Stormwater General Repairs/Upgrades $ 120,000.00 $ 50,000.00 $ 50,000.00 $ 50,000.00 $ 50,000.00 $ 50,000.00 $ 50,000.00 $ 0,000.00 5 50,000.00 $ 0,000.00 5$ 50,000.00$
Capital Projects
16th Street ‐ Sheridan Street and Landes Street $ ‐ 210,000.00 $ ‐$ ‐$$ 60,000.00 $ ‐ 150,000.00 $ ‐$ ‐$ ‐$ ‐$ ‐$
Hancock Street and 32nd Street $ ‐ 180,000.00 $ ‐$ ‐$ ‐$ ‐$ ‐$ ‐$ ‐$ ‐$ ‐$ 180,000.00$
Center Street ‐ San Juan Avenue to Olympic Avenue $ ‐ 400,000.00 $ ‐$ ‐$ ‐$ ‐$ ‐$ 125,000.00$ 275,000.00$ ‐$ ‐$ ‐$
12th Street Right‐of‐way, Logan Street and 14th Street ‐$ ‐$ ‐$ ‐$ ‐$ ‐$ ‐$ ‐$ ‐$ ‐$
Inflow/Infiltration Removal ‐ Lawrence Street at the intersections of Polk Street, Taylor
Street and Tyler Street $ ‐ 850,000.00 $ ‐$ ‐$ ‐$ ‐$ ‐$ ‐$ ‐$ ‐$ 550,000.00$ 300,000.00 $
Rainier Street Regional Stormwater Project $ 808,000.00 808,000.00 $ ‐$ ‐$ ‐$ ‐$ ‐$ ‐$ ‐$ ‐$ ‐$ ‐$
Logan Street Stormwater Pond Overflow $ 10,000.00 60,000.00 $ 50,000.00$ ‐$ ‐$ ‐$ ‐$ ‐$ ‐$ ‐$ ‐$ ‐$
Basin 8 ‐ Wetland Overflow (Hastings Pond)$ ‐ 250,000.00 $ ‐$ ‐$ ‐$ ‐$ ‐$ ‐$ ‐$ ‐$ ‐$ 250,000.00$
Basin 7 ‐ Wetland Overflow (Glasbell Property)$ ‐ 300,000.00 $ ‐$ ‐$ ‐$ ‐$ ‐$ ‐$ ‐$ ‐$ ‐$ 300,000.00$
Basin 5 ‐ Wetland Overflow (Behind Blue Heron Middle School) ‐$ ‐$ ‐$ ‐$ ‐$ ‐$ ‐$ ‐$ ‐$ ‐$ ‐$ ‐$
Basin Planning
Basin Planning Studies $ ‐ 250,000.00 $ ‐$ ‐$$ ‐ 50,000.00 $ ‐$ ‐$$ ‐ 50,000.00 $ ‐$ 150,000.00$
Existing Street Stormwater Improvements
Major Collectors and Minor Arterials $ ‐ 600,000.00 $ ‐$ 300,000.00$ ‐$ ‐$ ‐$ ‐$ ‐$300,000.00$ ‐$ ‐$
Local Access Streets $ ‐ 200,000.00 $ ‐$ ‐$$ ‐ 100,000.00 $ ‐$ ‐$ ‐$ ‐$$ 100,000.00 ‐$
Stormwater Management Plan Updates
Stormwater Management Plan $130,000.00 ‐$30,000.00 $ ‐$ ‐$ ‐$$ ‐ 100,000.00 $ ‐$ ‐$ ‐$ ‐$
Total Per Year $ 968,000.00 $ 100,000.00 $ 350,000.00 $ 260,000.00 $ 200,000.00 $ 150,000.00 $ 175,000.00 $ 375,000.00 $ 350,000.00 $ 450,000.00 $ 1,480,000.00
Stormwater Management Plan
City of Port Townsend
January 2019│ 553-2836-004 7-1
7. REFERENCES
Ecology (Washington State Department of Ecology). 1981. Geology and Ground-Water Resources of
Eastern Jefferson County, Washington. Olympia, WA. April 1981.
Mauger, G.S., J.H. Casola, H.A. Morgan, R.L. Strauch, B. Jones, B. Curry, T.M. Busch Isaksen, L. Whitely
Binder, M.B. Krosby, and A.K. Snover. 2015. State of Knowledge: Climate Change in Puget Sound.
Report prepared for the Puget Sound Partnership and the National Oceanic and Atmospheric
Administration. Climate Impacts Group, University of Washington, Seattle. doi:10.7915/CIG93777D.
Miller, I.M., H. Morgan, G. Mauger, T. Newton, R. Weldon, D. Schmidt, M. Welch, E. Grossman. 2018.
Projected Sea Level Rise for Washington State – A 2018 Assessment. A collaboration of Washington
Sea Grant, University of Washington Climate Impacts Group, Oregon State University, University of
Washington, and US Geological Survey. Prepared for the Washington Coastal Resilience Project.
Pessl, F., D.P. Dethier, D.B. Booth, J.P. Minard. 1989. Surficial Geology of the Port Townsend 1:100,000
Quadrangle, Washington. U.S. Geological Survey Miscellaneous Investigations Map I-1198F.
USDA (U.S. Department of Agriculture). 2007. Threshold Channel Design. Stream Restoration Design
National Engineering Handbook, 8.1-8.43.
Appendix A
Kickoff Meetings
Port Townsend 2017 Stormwater Management Plan (SWMP)
Project Kick-off Meeting
June 20, 2017 9:30 AM – 4:30 PM
9:30 – 9:45 Introductions and roles; meeting purpose Group
9:45– 10:00 Project summary Samantha and Paul
10:00-10:30 Scope, Schedule, and Communications Paul
10:30-11:30 Project needs and information brainstorming Paul leads Group
11:30-12:30 Working lunch Group
12:00 -12:30 Project Vision and Mission (part of working lunch) Group
12:30 -1:00 Project risk review Group
1:00 – 2:00 Operations, maintenance, information, and systems City staff
2:00 – 2:45 Problem area and priority project review City staff
2:45 – 4:30 Field review of problem areas and key features City staff
4:30 Adjourn
SURFACE WATER PROGRAM VISION AND MISSION STATEMENTS
Vision
A fully functional, achievable, and sustainable stormwater system that is integrated into the
landscape, supports envisioned growth, protects residents, and nurtures the environment.
Mission
• Safeguard public safety and minimize property damage
• Improve quality of stormwater runoff
• Prepare, implement and update a comprehensive plan to evaluate, measure, protect, design, and
construct a system for current and future needs
• Use appropriate, technologically sound, and cost-effective stormwater control solutions
• Define and protect the natural and built drainage systems
• Consider, accommodate, and direct future development
• Protect and improve existing water quality
• Correct existing drainage and stormwater management problems
• Protect, upgrade, and optimize the existing stormwater infrastructure
• Define appropriate measures to manage, optimize, and protect the roadway drainage and
stormwater system
• Operate, inspect, maintain, and repair the City’s existing stormwater infrastructure to continue
effective operation
• Protect wetlands, marine waters, and habitat
• Proactively address the City’s surface water needs for all existing and future customers and
accommodate system growth and expansion.
• Control temporary impacts from construction
• Consider and account for future changes in sea level and climate change
• Develop strategies to resolve existing flooding problems
• Determine the City staff and funding needed to accomplish the program mission
• Create an outreach plan that informs and engages residents to participate and stokes the willingness
to work together
MEETING NOTES
City of Port Townsend
Stormwater Management Plan
Things that you do well
• Coordinated and cooperative
• Do well with what you have
• Stormwater is not noticed and cared about
• WSU and Mater Gardeners coordinate and provide funding support
• Community interest in caring for stormwater facilities
• Low rain, no streams
• Attractive community
• Good GIS
MEETING NOTES
City of Port Townsend
Stormwater Management Plan
Notes
• Higher intensity and stormwater compatibility
• What does stormwater need to serve?
• What are stormwater utility expectations for delivery?
• Design facilities for climate change
• Design selection for lifecycle/maintenance
• Good CIP list
• Streets/stormwater undermaintained
• Setting thresholds for redevelopment
• Retrofitting to maximum extent practical (redevelopment)
• Opportunistic stormwater management/retrofitting
• Develop regulations – policy decisions
• Public property use – use natural drainage systems
• Integrated stormwater facilities – integrated into landscape
• What is a “critical drainage corridor” (CDC)?
• Should standards be changed?
• Utility crossings of CDC
• CDC should be better defined – different policy and standards
• Infill development – what should the stormwater standards be? Thresholds?
• What should single lot standards be?
• NPDES?
• Follow up/follow through on stormwater construction and implementation
• Inflow and infiltration into sanitary sewer
• Storm discharges to sanitary sewer
• Community and City maintenance of LID/GSI
• Skills/equipment/funding for stormwater maintenance
• Should LID maintenance selection match funding for stormwater maintenance?
• Existing stormwater BMPs in special FHA
• Plan review and system capacity
• Critical areas – stormwater facilities are regional
• Skills (engineers, contractors) to implement
• Demand for LID/GSI in the wrong locations
• Picking LID/GSI – how?
• Learning and experience on past LID/GSI – next project
• 2005 stormwater manual
• No stream
• Stormwater fee $25/month (last increased 4-5 years ago, 3,000 ft ERU, no discount, port not
included)
• Pet waste – some EDU
• No IDDE
RISK REGISTER
City of Port Townsend Stormwater Management Plan
Potential Risks Identified (at kickoff meeting) Likelihood Impact Mitigation
Samantha moves away H H Keep other City staff
members engaged (and
plan is too good to
miss)
Staff priorities change H H Provide timelines and
critical path for timely
input.
Stormwater/land use incompatible H H This is a key plan
element for
consideration
Inadequate data – delays, incomplete H H Identify potential data
gaps in early project
phase – during map
and data review (by
July 14)
Allocation of problems (existing pushed to new) H H This is a key plan
element for
consideration
Geologic uncertainty H H Develop plan
contingencies
Citizen challenges H M Stakeholder review
group
Projects (CIP) are not implementable (pre-plats, cost,
land, geology)
M H
Development constraints are large M H
Plan too complex or unimplementable, daunting M H
Samantha/staff time M M
Inconsistencies created M M
Adoption/review process M M
BAS issues (schedule) M M
Climate change M M
Site design standards incompatible with stormwater
needs due to cost
M M
GMA goals not met L H
Stormwater utility fee controversy L M
Changes in leadership L M
Land constraints on waterfront L M
MEETING NOTES
City of Port Townsend
Stormwater Management Plan
Stakeholders
•Hospital
•WSU Extension
•Beach Watchers
•Marine resource community
•Olympic Environmental Council
•Puget Sound Partnership
o Local integrating organization (Strait and Hood Canal)
•Contractors and landscapers
•Wetlands/critical areas consultants
•Realtors
•Friends of Kah-Tai
•Developers
•Jefferson County Land Trust
•Climate Action Committee
•Master Builder Association
•City Departments
o Engineering/Capital Projects
o Planning
o Operations
o Parks
o Finance
o Administration
o Attorney
•Jefferson County Health Department (sampling)
•Washington State Department of Ecology
•Design engineers/geotechs
Appendix B
Public Input Process
City of Port Townsend Stormwater Management Plan Communication Plan
8/14/2017 1
City of Port Townsend’s Stormwater Management Plan Communication
Plan
The Mission Statement for the Stormwater Management Plan is to develop a fully functional,
achievable, and sustainable stormwater system that is integrated into the landscape, supports
envisioned growth, protects residents, and nurtures the environment. To achieve this, good
communication throughout the Stormwater Management Plan adoption process is important.
This project communication plan identifies who needs what information, when they need the
information and how that information is provided.
The Stormwater Management Plan is a functional plan which addresses existing stormwater
system conditions; the operation and maintenance of existing conditions and capacity for
adding new facilities; identifying capital project needs; and how to finance capital and
operational costs. Stormwater management is about drainage and flooding, as well as water
quality. The City has a range of soil types from hard pan to sandy soils which impact
stormwater solutions. The City intends to plan for surface water management as a whole –
integrating a preservation of water resources through natural systems approach where possible
while protecting environmental values and public health. The process will include comparison
on 2005 and 2012 DOE Stormwater Manual and recommended concurrent amendments to the
City’s development regulations/Engineering Design Standards to ensure public and private
projects achieve the City’s adopted level of service standard (e.g., A level of conveyance,
detention, and treatment that meets the Department of Ecology (DOE) Stormwater Manual
adopted by the City or as defined in the City’s Stormwater Master Plan).
The adoption schedule is to have a draft Stormwater Management Plan before City Council by
December 2017. In order to achieve this schedule, there will be a series of task force meetings;
a public open house and a Comprehensive Plan concurrency meeting with the Planning
Commission in addition to internal City staff meetings with our stormwater consultant team.
After the task force meetings and the public open house a draft plan will be created which will
incorporate the input and comments from both internal and external meetings.
GOALS
The overarching goals of the Communications Program (Program) are to:
· Review external and internal communications needs for the Stormwater Management
Plan; including required step approvals of the plan prior to City Council first reading.
Create and outline the communication steps with internal staff and consultants.
City of Port Townsend Stormwater Management Plan Communication Plan
8/14/2017 2
· Describe how decisions are made (Operating Guidelines) and how those decisions are
communicated internally and externally.
· Document how project information (i.e. schedule, budget, risk, change) is
communicated with the task force, the public, City Council, internal staff, and
consultants.
· Describe the frequency of updates and method of communication (email, phone, web,
etc.).
Communication Needs
This communications plan identifies needs for “external” communications (i.e., communication
with the task force and the public) and “internal” communications (i.e., communications
between city staff and the consultant team).
External Communications
· The City will form an administrative technical advisory task force (task force) group. The
interest groups which will be targeted to be on the task force are below.
o Architect/Designer
o WSU Extension
o Beach Watchers
o Marine Resource Committee
o Olympic Environmental Council
o Puget Sound Partnership
o Local integrating organization (Strait and Hood Canal)
o Contractors and landscapers
o Wetlands/critical areas consultants
o Friends of Kah-Tai
o Developers
o Jefferson County Land Trust
o Climate Action Committee
o Master Builder Association
o City Departments
o Engineering/Capital Projects
o Planning
o Operations
o Parks
o Finance
o Administration
o Attorney
o Jefferson County Health Department (sampling)
o Washington State Department of Ecology
o Local 2020
o Admiralty Audubon Society
City of Port Townsend Stormwater Management Plan Communication Plan
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o Port of Port Townsend
o Environmental Health
o Design engineers/geotechs
External Communication Methods
PUBLIC COMMUNICATIONS TOOLS AND TASKS
· The table below provides the outline for the public process for the Stormwater
Management Plan.
· Potential communication tools for messaging the Stormwater Management Plan
o Utility Newsletter – Monthly newsletter with message from the Mayor and
updates from City departments – mailed in utility bills and available on line and
o Capital Projects and Public Works Projects Webpage; also captured on the City
website
o Specialized print collateral such as brochures, maps
o City Websites – Includes Official City Website “CityofPT.us,” City Library website
“PTPublicLibrary.org.”
o City website calendar of City meetings
o Public Access Television Station – PTTV
o KPTZ – local community radio station (for news & emergency communication)
o Press Releases and media advertisements – display ads. (PT Leader, Peninsula
Daily News, KPTZ)
o Town meetings including both city-wide education and special neighborhood
meetings for Capital Projects
o Live streamed and archived City Council and Planning Commission posted
meetings and agenda materials
o Posted agendas for City Advisory Boards
o Speak Up PT – Civic Engagement site for Surveys, Forums, Citizen Ideas,
Discussions and eComment on meetings
City of Port Townsend Stormwater Management Plan Communication Plan
8/14/2017 4
Who; identify
agencies,
stakeholders,
businesses,
the public,
etc.
What event? What information
will be provided?
How will
information be
provided?
When will the
information be
provided?
With
what
frequency
?
Responsible
Party
Task Force Task Force #1
Open Public
Meeting (i.e.
public can
attend but
not
comment)
Existing
stormwater
conditions,
comparison on
2005 and 2012
DOE Stormwater
Manual
Packets will be
mailed and/ or
emailed to the
task force
group
Late-August
2017
Twice Samantha,
Paul and Julie
PUBLIC
COMMENT
N/A Public to comment
on the scoping of
the project
City website Late-August Once – for
2-week
long
comment
period
Samantha
Task Force Task Force #2
Open Public
Meeting (i.e.
public can
attend but
not
comment)
Re-cap of task
force meeting #1
and public open
house, Capital
project review and
financing
Packets will be
mailed and/ or
emailed to the
task force
group
Early October
2017
One time Samantha,
Paul and Julie
Public Open House
Presentation
/Open
House
combination
?
Maps of existing
stormwater
priorities to be
ranked by the
public, gather
public input on
stormwater
issues
Boards and
comment
sheets will be
provided at
the meeting
September
2017
One
time
Samantha,
Paul and
Julie
PUBLIC
COMMENT
Public Comment
on the draft
Stromwater Plan
City website Late-October One – for
a 2-week
long
comment
period
Samantha
SEPA
Submission
Submit SEPA
to DSD
Department
SEPA Checklist,
back-up, mailing
list and money
Hard copy to
front desk of
DSD
Late-
October/early
November 2017
Once Samantha
Planning
Commission
Planning
Commission
Public
Hearing
Draft Stormwater
Management Plan
for a Consistency
Review to the
Comprehensive
Plan
Packets will be
given to the
Clerk’s Office to
distribute to
the Planning
Commission
November 2017 One time Samantha
City of Port Townsend Stormwater Management Plan Communication Plan
8/14/2017 5
Who; identify
agencies,
stakeholders,
businesses,
the public,
etc.
What event? What information
will be provided?
How will
information be
provided?
When will the
information be
provided?
With
what
frequency
?
Responsible
Party
City Council City Council
Workshop
Draft Stormwater
Management Plan;
summary of
comments from
Stakeholder
meetings 1 and 2
and public open
house; public
comment letters
Packets will be
given to the
Clerk’s Office to
distribute to
the City Council
November 2017 One time Samantha,
Paul and Julie
City Council City Council
Business
Meeting –
Public
Hearing
Draft Stormwater
Management Plan
with comments
from the CC
Workshop
Packets will be
given to the
Clerk’s Office to
distribute to
the City Council
December 2017 One time Samantha
City Council City Council
Business
Meeting
Final Stormwater
Management Plan
Packets will be
given to the
Clerk’s Office to
distribute to
the City Council
January or
February 2018
One time Samantha
Dept. of
Commerce
Preliminary
Review and
60-day review
Send Stormwater
Plan after submit
SEPA and a Final
after adopted by
City Council
Email Late
October/Early
November and
January/Februa
ry 2018
Twice Samantha
Internal Communication Methods
OPERATING GUIDELINES
· For project team meetings Parametrix will set the agenda and take and distribute notes.
· For stakeholder groups and open houses City will provide the agenda and do notes (no
minutes will be taken at the stakeholder meetings. Parametrix will provide information
as outlined in the table below.
TEAM PROTOCOL
· Identify key decision makers and authority levels by position.
· Parametrix will provide deliverables as outlined in their Scope of Work.
· Identify a document management (including email) protocol for sharing, storing and
archiving project documents. For example; project documents will be stored in a
common project folder on the office “public works” drive. Identify a responsible party.
City of Port Townsend Stormwater Management Plan Communication Plan
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· City Clerk’s office will take minutes at the Planning Commission and Council Meetings.
City staff with technical assistance from Parametrix will prepare the planning
commission and city council packets. City staff will prepare the agenda bill(s) and
ordinance(s) for the City Council meetings.
REPORTING
The following example identifies the deliverables and internal communication needs of the
project manager and the consultant.
What, identify
the
deliverable.
How will the
information be
provided?
When will the
information
be provided?
With what
frequency?
Party
responsible
for delivery.
Party
responsible
for accepting
Progress
Reports
pdf via email Beginning of
the Month?
Monthly Paul,
Parametrix
Samantha,
City
Public
Engagement
Pdfs via email 3
maps,
questionnaire
and handouts
Prior to the
Stakeholder
Meetings
and/or Public
Open House
3 Times Paul,
Parametrix
Samantha,
City
Project
Schedule
pdf Project status
meetings
Monthly Paul,
Parametrix
Samantha,
City
Working Draft
for SWMP for
City Staff to
review
MS Word November
2017
Once Paul,
Parametrix
City Staff
through
Samantha
Council Draft
for SWMP
MS Word or
pdf?
December
2017
Once Paul,
Parametrix
City Staff and
Council
Implementation Process
After the Stormwater Management Plan is adopted then an implementation process will start. The
implementation process may include the following, this is not intended to be an all-inclusive list.
· Development Services Department and Public Works Department Staff training on the contents
of the Stormwtaer Management Plan
· Development Review Staff training on how the regulations have changed with the newly
adopted Stormwater Management Plan
· Review, sign-off and “go-live” of stormwater development handouts created during the
Stromwater Management Plan process from the LEAN group and sponsors.
· Feedback from the public on stormwater regulation changes and how they are being
implemented through development review.
STORMWATER MANGEMENT PLAN TASK FORCE GROUP
Task Force Participant Contact Information Name Atlernative
Architect/Designer Simon Little Richard Berg
WSU Extension Bob Simmons
Beach Watchers Cheryl Lowe
Marine Resource Committee Cheryl Lowe
Olympic Environmental Council Darlene S. Nan Evans?
Puget Sound Partnership John Cambalik
Local integrating organization (Strait and Hood Canal)
Contractors Tim Johnson
Landscapers Matt Berberich
Wetlands/critical areas consultants Fred Weinmann
Friends of Kah-Tai General Account
Developers Fred Kimball Suzanne Tyler
Jefferson County Land Trust Richard Tucker
Climate Action Committee Cindy Jayne
Master Builder Association Brent Davis
City Engineering/Capital Projects Samantha Harper
City Engineering/Capital Projects Dave Peterson
City Engineering - Development Review Brandon Maxwell Scott Studeman
City Planning Department Judy Surber
City Planning Department John McDonagh
City Public Works Operations Dave Zellar
City Public Works Operations Larry Grewell
City Parks Alex Wiseniewski
City Finance Nora Mitchell Sheila Danielson
Jefferson County Health Department (sampling)Michael Dawson
Washington State Department of Ecology Rick Marz
Local 2020 Cindy Jayne
Admiralty Audubon Society Debbie Janke Bill Vogt
Port of Port Townsend Sam Gibboney
Environmental Health Susan Porto
Design engineers/geotechs Harold Andersen
AGENDA
Stormwater Management Plan - Advisory Task Force
Workshop 1 | August 30, 2017 | Cotton Building, 607 Water Street, Port Townsend
1:00 – 1:15 Welcome and Agenda
1:15 – 1:30 Introductions
1:30 – 1:45 Meeting Purpose and Goal
1:45 – 2:45 Brainstorming and Input
2:45 – 3:00 Break
3:00 – 4:00 Project Scope, Framework, and Schedule
4:00 – 4:15 Stormwater Manual Review
4:15 – 4:30 Communications and Outreach
4:30 – 5:00 Meeting Summary
5:00 Adjourn
SURFACE WATER PROGRAM VISION AND MISSION STATEMENTS
Vision
A fully functional, achievable, and sustainable stormwater system that is integrated into the
landscape, supports envisioned growth, protects residents, and nurtures the environment.
Mission
• Safeguard public safety and minimize property damage
• Improve quality of stormwater runoff
• Prepare, implement and update a comprehensive plan to evaluate, measure, protect, design, and
construct a system for current and future needs
• Use appropriate, technologically sound, and cost-effective stormwater control solutions
• Define and protect the natural and built drainage systems
• Consider, accommodate, and direct future development
• Protect and improve existing water quality
• Correct existing drainage and stormwater management problems
• Protect, upgrade, and optimize the existing stormwater infrastructure
• Define appropriate measures to manage, optimize, and protect the roadway drainage and
stormwater system
• Operate, inspect, maintain, and repair the City’s existing stormwater infrastructure to continue
effective operation
• Protect wetlands, marine waters, and habitat
• Proactively address the City’s surface water needs for all existing and future customers and
accommodate system growth and expansion.
• Control temporary impacts from construction
• Consider and account for future changes in sea level and climate change
• Develop strategies to resolve existing flooding problems
• Determine the City staff and funding needed to accomplish the program mission
• Create an outreach plan that informs and engages residents to participate and stokes the willingness
to work together
Location Approximate Page
Numbers
Change Tied
to Permit
Language
Change Reasoning or Comments
General
Inside cover page ES-i and ES-ii Added an Executive Summary Summarized the reasons for the update, the uses of the manual and
provided information on the public involvement process.
All Volumes Renumbered Tables and Figures
Renumbered all tables and figures in all Volumes. The new numbers
coordinate tables and figures to the section of the Volume where they
are located. (Eg. Figure 2.4.2 is the second figure in Section 2.4, Table
4.1.3 is the third table in Section 4.1).
Chapter 1 - Introduction 1-1 through 1-26 Update incorrect or outdated code
references.
Revised incorrect or outdated code references, such as the RCW and
WAC.
Chapter 1 - Introduction 1-1 through 1-26 Minor language changes.Revised for clarity and removed outdate language in Sections 1.2, 1.4,
1.5.1, 1.6.10.
Section 1.5.4 Flow Control BMPs 1-5 Minor language changes.Revised language for changes made in Appendix I-D Guidelines for
Wetlands when Managing Stormwater.
Section 1.5.5 On-site Stormwater Management
BMPs 1-6 Additional guidance provided.Language added to categorize On-site Stormwater Management BMPs,
including LID BMPs.
Section 1.6.4 The Puget Sound Action Agenda 1-11 through 1-13
Significant revisions to remove outdated
guidance and to add new guidance. Section
renamed.
Removed references and guidance related to the Puget Sound Water
Quality Management Plan and replaced with guidance on the Puget
Sound Action Agenda.
Section 1.6.5 Phase I - NPDES and State Waste
Discharge Stormwater Permits for Municipalities 1-13 through 1-14 Yes Additional guidance provided and outdated
guidance removed.
Added guidance referring Phase I Municipal Stormwater Permittees to
Appendix 1 of the permit for more information on the requirements for
their stormwater program requirements.
Section 1.6.6 Phase II - NPDES and State Waste
Discharge Stormwater Permits for Municipalities 1-14 Yes Additional guidance provided and outdated
guidance removed.
Added guidance referring Phase II Municipal Stormwater Permittees to
Appendix 1 of the permit for more information on the requirements for
their stormwater program requirements.
Section 1.6.7 Municipalities Not Subject to the
NPDES Stormwater Municipal Permits 1-14 Guidance removed.Removed outdated references to the Puget Sound Water Quality
Management Plan. Section renamed.
Section 1.6.8 Industrial Stormwater General Permit 1-14 through 1-15 Yes Revised to coordinate with the current
Industrial Stormwater General Permit
Revised to provide an overview of the requirements of the current
Industrial Stormwater General Permit and their relationship to the BMPs
in the manual.
Section 1.6.9 Construction Stormwater General
Permit 1-15 through 1-16 Yes Revised to coordinate with the current
Construction Stormwater General Permit
Revised to provide an overview of the requirements of the current
Construction Stormwater General Permit and their relationship to the
BMPs in the manual.
Section 1.6.15 Underground Injection Control
Authorizations 1-18 through 1-19 Significant revisions to add guidance.Added language to refer to Ecology's website and to define UIC well.
Chapter 2 - Minimum Requirements for New
Development and Redevelopment 2-1 through 2-46 Minor language changes.Revised for clarity and removed outdated language in the introduction
and in Sections 2.1, 2.2, 2.5.3, and 2.5.10.
Chapter 2 - Minimum Requirements for New
Development and Redevelopment 2-1 through 2-46 Yes Revised language.
Revised definitions, requirements, supplemental guidance, etc. to
correspond to the changes in the Municipal Stormwater Permits and for
new LID requirements.
Volume I Minimum Technical Requirements and Site Planning
Chapter 1 - Introduction
Chapter 2 - Minimum Requirements for New Development and Redevelopment
Location Approximate Page
Numbers
Change Tied
to Permit
Language
Change Reasoning or Comments
Section 2.1 Relationship to the Puget Sound Action
Agenda 2-2 Added guidance. Section renamed.
Removed outdated references to the Puget Sound Water Quality
Management Plan. Section renamed and focuses on relationship of the
manual to the municipal stormwater permits.
Section 2.3 Definitions Related to Minimum
Requirements 2-5 through 2-9 Yes Added and revised definitions.
Added definitions for a few terms used previously but not previously
defined. Other terms have a revised definition or a new definition (hard
surfaces, LID, converted vegetation) because of the new low impact
development (LID) guidance and requirements in the Municipal
Stormwater Permits.
Section 2.4 Applicability of the Minimum
Requirements 2-9 through 2-16 Yes
Revised the thresholds for determining
which minimum requirements apply to new
development and redevelopment. Revised
supplemental guidelines.
Changes include: the replacement of “impervious” surfaces with “hard”
surfaces, the application of minimum requirements #6 - #9 to replaced
hard surfaces at new development sites, the deletion of the word
"native" from the land conversion threshold.
Section 2.5.1 Minimum Requirement #1:
Preparation of Stormwater Site Plans 2-16 Yes Revised requirements and objective.
Added a new statement for the site plan to use site-appropriate
development principles to retain native vegetation and minimize
impervious surfaces to the extent feasible.
Section 2.5.2 Minimum Requirement #2:
Construction Stormwater Pollution Prevention
(SWPP)
2-17 through 2-26 Yes
Reorganized and revisions to: thresholds,
general requirements, construction SWPPP
elements, objective, and supplemental
guidelines.
Changes include: revisions to the construction SWPPP elements to
correspond with the Construction Stormwater General Permit, the
addition of element #13 that requires the protection of LID Best
Management Practices, and revision of element #12 to include
responsibilities for an inspector or CESCL depending on the size of the
project.
Section 2.5.4 Minimum Requirement #4:
Preservation of Natural Drainage Systems and
Outfalls
2-27 through 2-28 Yes Minor additions.Added clarification for peak discharges using 15 minute time steps.
Section 2.5.5 Minimum Requirement #5: On-site
Stormwater Management 2-28 through 2-32 Yes Multiple revisions for new low impact
development (LID) requirements.
Changes include: the new LID performance standard and list options
based on project size and location. The lists are divided into three land
use types: lawn and landscaped areas; roofs, and other hard surfaces.
Projects implementing the list option must select the first feasible BMP
for each land use type. Some of the BMPs included in the lists are: rain
gardens, permeable pavements, bioretention, soil quality and depth, full
and partial dispersion methods, full downspout infiltration and
perforated stub-outs.
Section 2.5.6 Minimum Requirement #6: Runoff
Treatment 2-33 through 2-35 Yes
Revisions to the thresholds, Water Quality
Design Flow Rate, and supplemental
guidelines.
Revisions made to acknowledge the use of permeable pavements and
the related new definitions. The intent is to continue to capture the
same size and types of projects as previously. More accurate definitions
for water quality design storm volume and flow rate.
Section 2.5.7 Minimum Requirement #7: Runoff
Flow Control 2-35 through 2-40 Yes Revisions to the thresholds and
supplemental guidelines.
Revisions to acknowledge the use of permeable pavements and the
related new definitions. Clarifications about the surfaces that the
requirement applies to, and the use of the 0.10 /0.15 cfs threshold. The
intent is to capture the same size and types of projects as previously.
Section 2.5.8 Minimum Requirement #8: Wetlands
Protection 2-40 through 2-41 Yes
Revisions to the applicability, thresholds,
standard requirement, additional
requirements, and supplemental guidelines.
Revisions correspond to the significantly revised Appendix I-D Guidelines
for Wetlands when Managing Stormwater .
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Section 2.8 Exceptions/Variances 2-45 through 2-46 Yes Additional guidance provided.Changed and added language to be consistent with the requirements in
Appendix 1 of the 2007 municipal stormwater permits.
Chapter 3 - Preparation of Stormwater Site Plans 3-1 through 3-17 Yes
Significant changes to incorporate
procedures necessary for LID
implementation.
Revised for clarity and removed outdate language in the introduction
and in section 3.1.7.
Section 3.1.1 Step 1 - Collect and Analyze
Information on Existing Conditions 3-2 through 3-7 Yes Additional guidance provided and outdated
guidance removed.
Additional guidance details the information necessary for site analysis,
and in particular for LID site design. Split into subsections based on
whether Min. Requirements 1 - 5 apply, or Min. Requirements 1 - 9
apply.
Sections 3.1.2 to 3.1.4 3-7 through 3-8 Yes Guidance added.References to on-site BMPs added and preliminary determination of
applicable minimum requirements.
Section 3.1.5 Step 5 - Prepare a Permanent
Stormwater Control Plan 3-8 through 3-12 Yes
Revisions to all subsections of Developed
Site Hydrology of the Permanent
Stormwater Control Plan.
Significant changes to describe how to prepare the Permanent
Stormwater Control Plan that incorporates LID features. Separate
guidance for projects subject to Min. Requirements 1 - 5 and projects
subject to Min. Requirements 1 - 9.
Section 3.1.6 Step 6 - Prepare a Construction
Stormwater Pollution Prevention Plan 3-13 through 3-14 Yes Minor language changes.Changes for clarification and to remove repetitive language.
Section 3.1.7 Step 7 - Complete Stormwater Site
Plan 3-14 through 3-16 Yes
Reference to needed soils report and
addition of Declaration of Covenants and
Grants of Easement.
Soils reports are necessary part of LID decisions. Declarations of
Covenants and Grants of Easement are necessary mechanisms to identify
LID features, establish maintenance requirements and government
access for inspections of privately maintained stormwater BMPs and
facilities.
Section 3.2.2 Final Corrected Plan Submittal 3-17 Guidance added.Added several LID BMPs that require the submission of as-builts.
Section 4.2 BMP and Facility Selection Process 4-1 through 4-4
Revised language, proposed replacing the
language in Step V: Select Treatment
Facilities with a reference to Chapter 2 of
Volume V.
Revisions and new language especially in Step III for guidance on
modeling threshold discharge areas. Minor revisions to correspond with
the changes in the Municipal Stormwater Permits and for new LID
requirements. Ecology replaced the language in Step V: Select
Treatment Facilities with a reference to Chapter 2 of Volume V.
Appendix I-A Guidance for Altering the Minimum
Requirements Through Basin Planning A-1 through A-3 Additional guidance provided.Added language for clarity on use of Basin Planning for addressing
retrofit needs and for developing an alternative flow control strategy.
Appendix I-B Rainfall Amounts and Statistics B-1 through B-5
Removed introductory language and
background information on the Water
Quality Design Storm and Water Quality
Design Flow Rate.
Removed background and outdated information for brevity. Renamed
the appendix and retained the rainfall tables.
Chapter 3 - Preparation of Stormwater Site Plans
Chapter 4 - BMP and Facility Selection Process for Permanent Stormwater Control Plans
Appendix I-A Guidance for Altering the Minimum Requirements Through Basin Planning
Appendix I-B Rainfall Amounts and Statistics
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Appendix I-D Guidelines for Wetlands when
Managing Stormwater D-1 through D-18 Yes
Multiple revisions for the use and/or the
protection of Wetlands when managing
stormwater.
Rewritten to remove outdated information, clarify concepts, and
approach the protection and use of wetlands through controlling
discharges to wetlands. Total discharges to wetlands must not deviate by
more than 20% on a single event basis, and must not deviate by more
than 15% on a monthly basis.
Appendix I-E Flow Control-Exempt Surface Waters E-1 through E-4 Yes Added and deleted Exempt Surface Waters.List edited to add additional waters based on specific requests and
analyses, and to remove reference to a creek in Eastern WA.
Appendix I-F Basins with 40% or more total
impervious area since 1985 F-1 Yes Added Map
Map shows basins which potentially qualify for use of existing land cover
as the pre-developed land cover for flow control purposes. See reference
in Min. Requirement #7.
Glossary and Notations Glossary-1 through
Glossary-47 Added and revised definitions.
There are a few terms, used previously but not defined, for which a
definition has been added. A handful of other terms have a revised
definition, and there are new terms, because of the new low impact
development (LID) guidance and requirements in the Municipal
Stormwater Permits.
Appendix I-D Guidelines for Wetlands when Managing Stormwater
Appendix I-E Flow Control-Exempt Surface Waters
Appendix I-F Feasibility Criteria for Selected Low Impact Development Best Management Practices
Glossary and Notations
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Chapter 1 - Introduction Construction Stormwater
Pollution Prevention 1-1 through 1-9 Multiple revisions for plain language, clarity,
and brevity.Revised this chapter to use simpler and clearer language.
Section 1.3 How to Use This Volume N/A
This section was removed. The information
in this section is now included in Sections
1.2.
Removed this section by combining it with Section 1.2 to eliminate
duplicate language.
Section 1.3 Thirteen Elements of Construction
Stormwater Pollution Prevention 1-3 Yes Renamed.Revised to incorporate a new element, Protect Low Impact Development
BMPs.
Figure 1.5.1 1-6 Replaced.Replaced older figure with an updated one.
Chapter 2 - Regulatory Requirements 2-1 through 2-6 Multiple revisions for plain language, clarity,
and brevity.
Revised this chapter to use simpler and clearer language. Information
covered in Volume I, Section 1.6 Relationship of the Manual to Federal,
State, and Local Regulatory Requirements was removed.
Chapter 2 - Regulatory Requirements 2-1 through 2-6 Yes
Multiple revisions to coordinate the manual
to the Washington State General
Stormwater Permits.
Revised this chapter to update this information for revisions to the
Stormwater General Permits (including the Municipal, Construction, and
Industrial Permits).
Section 2.1 and Section 2.2 2-2 through 2-4 Yes
Section 2.1 The Construction Stormwater
General Permit and Section 2.2 Construction
Stormwater Pollution Prevention Plans now
replace the previous Sections 2.1 and 2.2.
Replaced these sections to remove invalid information or duplicate
information. Sections 2.1 and 2.2 now go into detail about the
relationship of Volume II to the Construction Stormwater General Permit
and the requirements for a Stormwater Site Pollution Prevention Plan.
Chapter 3 - Planning 3-1 through 3-32 Multiple revisions for plain language, clarity,
and brevity.
Revised this chapter to use simpler and clearer language. Information
covered in Volume I, Section 1.6 Relationship of the Manual to Federal,
State, and Local Regulatory Requirements was removed.
Section 3.2 and Section 3.3 3-4 through 3-32 Previous Sections 3.2 and 3.3 have been
reversed.
Moved The Construction SWPPP Requirements, previously in Section 3.3
to Section 3.2 for clarity. The Step-By-Step Procedure now follows in
Section 3.3. Please note that the Construction Stormwater Pollution
Prevention Plan Checklist is still located in Section 3.3.
Section 3.3.3 (Previously Section 3.2.3) Step 3 -
Construction SWPPP Development and
Implementation
3-8 through 3-32 Yes Multiple revisions to the Construction
SWPPP Elements.
Revised The Construction SWPPP Elements, described in Section 3.3.3 to
coordinate with the Construction Stormwater General Permit, Municipal
Stormwater Permits, and the Construction BMPs in Chapter 4. Each
element now contains an Additional Guidance section that has
information not required by the permits. Added Element #13 Protect
Low Impact Development BMPs.
Volume II Construction Stormwater Pollution Prevention
Chapter 1 - Introduction Construction Stormwater Pollution Prevention
Chapter 2 - Regulatory Requirements
Chapter 3 - Planning
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Chapter 4 - Best Management Practices Standards
and Specifications 4-1 through 4-128 Added approved equivalent BMPs Sections.Refers to Ecology's website for BMPs that have been approved as
equivalent.
Section 4.1 Source Control BMPs 4-1 through 4-2 Yes Added Table 4.1 Source Control BMPs by
SWPPP Element
Ecology added Table 4.1 Source Control BMPs by SWPPP Element to
show how the BMPs listed in Section 4.1 relate to the SWPPP Elements.
BMP C103: High Visibility Fence 4-6
This BMP now includes high visibility silt
fence. Multiple revisions for plain language,
clarity, and brevity.
Added high visibility silt fence because it meets the intent of BMP C103.
Ecology revised this chapter to use simpler and clearer language.
BMP C104: Stake and Wire Fence N/A This BMP was removed.Removed this BMP because BMP C103: High Visibility Fence meets the
intent of this BMP in a safer and more commonly used manner.
BMP C105: Stabilized Construction Entrance / Exit 4-7 through 4-9 Additional guidance provided and outdated
guidance removed.
Added and removed guidance for this BMP based on comments received
and field experience.
BMP C106: Wheel Wash 4-9 through 4-11 Additional guidance provided and outdated
guidance removed.
Added guidance to clarify that wheel wash wastewater shall not
discharge to surface or ground water.
Figure 4.1.2 - Wheel Wash 4-11 Figure was updated Updated figure to provide more details of a typical Wheel Wash.
BMP C120: Temporary and Permanent Seeding 4-13 through 4-19
Multiple revisions for plain language, clarity,
and brevity. Additional guidance provided
and removed.
Revised and reorganized this BMP to use simpler and clearer language.
Moved some guidance to BMP C121: Mulching or BMP C125: Top soiling.
Ecology added and removed additional guidance for this BMP based on
comments received and field experience.
BMP C121: Mulching 4-19 through 4-21 Additional guidance provided.
Added minimum mulch thickness based on field experience and
comments. Ecology added guidance previously found in BMP C120:
Temporary and Permanent Seeding to this BMP.
Table 4.1.8 4-21 Additional guidance provided.Added Wood Straw and Wood Straw Mulch to the table.
BMP C122: Nets and Blankets 4-22 through 4-25 Multiple revisions for plain language, clarity,
and brevity.Revised this BMP to use simpler and clearer language.
BMP C123: Plastic Covering 4-25 through 4-27 Additional guidance provided and outdated
guidance removed.
Removed the use of plastic sheeting over seeded areas because other
coverings (such as compost and straw) are preferable. Ecology added
and removed guidance for this BMP based on comments received and
field experience.
BMP C124: Sodding 4-27 through 4-28 Additional guidance provided and outdated
guidance removed.
Provided a link to composting guidance and removed old reference to
compost specification.
BMP C125: Top soiling / Composting 4-29 through 4-32 Additional guidance provided and outdated
guidance removed.
Added guidance previously found in BMP C120: Temporary and
Permanent Seeding to this BMP. Ecology added and removed guidance
for this BMP based on comments received and field experience.
BMP C150: Materials on Hand 4-42 through 4-43 Suggested measures and quantities
removed.
Removed measures and quantities because measures and quantities
should be based on the size of the construction site.
Chapter 4 - Best Management Practices Standards and Specifications
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BMP C151: Concrete Handling and BMP C152:
Sawcutting and Surface Pollution Prevention 4-43 through 4-45 Yes Additional guidance provided.
Added guidance to coordinate this BMP with the requirements of the
Construction Stormwater General Permit and to make it clear that
Concrete spillage or concrete discard to surface waters of the State is
prohibited.
BMP C154: Concrete Washout Area 4-48 through 4-53 Added this BMP.Added this BMP to provide additional guidance for concrete washout
areas.
BMP C160: Certified Erosion and Sediment Control
Lead 4-54 through 4-55 Additional guidance provided and outdated
guidance removed.
Minimum Requirements for ESC Training and Certification Courses has
been removed. Ecology plans on issuing separate, updated guidance in
the near future.
BMP C161: Payment of Erosion Control Work N/A This BMP was removed.Removed this BMP because it is not applicable to the full range of
projects needing to perform Erosion and Sediment Control Work.
BMP C180: Small Project Construction Stormwater
Pollution Prevention N/A Yes This BMP was removed.
Removed this BMP because of changes in threshold requirements in
both the Municipal Stormwater General Permits and Construction
Stormwater General Permit.
Section 4.2 Runoff Conveyance and Treatment
BMPs 4-57 Yes Added Table 4.2 Runoff Conveyance
Treatment BMPs by SWPPP Element
Added Table 4.2 Runoff Conveyance Treatment BMPs by SWPPP Element
to show how the BMPs listed in Section 4.2 relate to the SWPPP
Elements.
BMP C207: Check Dams 4-74 through 4-77 Additional guidance provided.Added guidance for this BMP based on comments received and field
experience.
BMP C220: Storm Drain Inlet Protection 4-78 through 4-79 Additional guidance provided.Added guidance for inlet protection of lawn and yard drains and based
on comment received and field experience.
BMP C230: Straw Bale Barrier N/A This BMP was removed.Removed this BMP because this BMP has been proven to be ineffective.
BMP C233: Silt Fence 4-90 through 4-95 Multiple revisions for plain language, clarity,
and brevity.Revised and reorganized this BMP to use simpler and clearer language.
BMP C235: Wattles 4-96 through 4-99 Renamed from Straw Wattles.Renamed this BMP to include wattles made from compost or other
materials.
BMP C236: Vegetated Spray Fields 4-100 through 4-102 Added this BMP.Added this new BMP for dewatering, Construction SWPPP Element #10.
BMP C250: Construction Stormwater Chemical
Treatment 4-112 through 4-120 Additional guidance provided.
Added guidance for this BMP, previously available online, to
coordinate with the Chemical Technology Assessment Protocol
(CTAPE) program.
BMP C251: Construction Stormwater Filtration 4-120 through 4-124 Additional guidance provided.Added sizing criteria for this BMP, previously available online.
BMP C252: High pH Neutralization Using CO2 4-125 through 4-127 Added this BMP.Added this BMP, previously available online, to provide guidance
on neutralizing high pH through the use of CO2.
BMP C253: pH Control for High pH Water 4-128 through 4-129 Added this BMP.Added this BMP, previously available online, to provide additional
guidance for neutralizing high pH.
Appendix II-B Background Information on Chemical
Treatment B-1 through B-3 Multiple revisions to coordinate with BMP
C252 and BMP C53.
Revised this appendix to coordinate with the new information provided
in BMP C252 and in BMP C253.
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Chapter 2 - Hydrologic Analysis
Chapter 2 - Hydrologic Analysis 2-1 through 2-17 Multiple revisions for plain language, clarity,
and brevity.
Revised this chapter to use simpler and clearer language. Outdated
guidance was replaced.
Section 2.2 Western Washington Hydrology Model 2-4 through 2-9 Section 2.2 split into multiple subsections.Section 2.2 split into multiple subsections for clarity and for referencing
purposes.
Section 2.2 Western Washington Hydrology Model 2-4 through 2-9 Additional guidance provided.Added guidance on upcoming Western Washington Hydrology Model
(WWHM) changes.
Section 2.2.2 Assumptions made in creating the
WWHM 2-5 through 2-8 Additional guidance provided.Added guidance on precipitation data and upcoming WWHM changes.
Section 2.2.3 Guidance for flow-related standards 2-8 through 2-9 Yes
Additional guidance provided and outdated
guidance removed for Minimum
Requirements (MR).
Added guidance for MR #5 which now includes an LID Performance
Standard. Revised the guidance for MR#8 to reflect the changes made in
Volume I, Appendix 1-D.
Chapter 3 - Flow Control Design 3-1 through 3-109 Multiple revisions for plain language, clarity,
and brevity.Revised this chapter to use simpler and clearer language.
Chapter 3 - Flow Control Design 3-1 Yes Update text for consistency with revised Min
Req'mt #5 and LID
Added references to Minimum Requirement #5, bioretention and
permeable pavements in introductory section.
Section 3.1 Roof Downspout Controls 3-1 through 3-18 Yes Update text & figure for consistency with
revised Min Req'mt #5 Text and figures updated to indicate priorities for handling roof runoff.
Section 3.1 Roof Downspout Controls 3-1 through 3-3 Yes Update text for consistency with revised Min
Req'mt #5
Updated references to revised roof downspout BMPs and Rain Gardens
in the introductory section.
Section 3.1.1 Roof Downspout Full Infiltration (BMP
T5.10A)3-4 through 3-10 Yes Update text for consistency with revised Min
Req'mt #5
Text changes for consistency with new priority lists in Min.Req'ment #5
and feasibility criteria. Needed better clarity in design guidance
Section 3.1.2 Downspout Dispersion Systems 3-11 through 3-16 Yes Update text for consistency with revised Min
Req'mt #5
Text changes for consistency with new priority lists in Min. Req'ment #5
and feasibility criteria. Improved clarify in design guidance and
computer modeling. Added guidance for design criteria for dispersion
trenches and splashblocks.
Section 3.1.3 Perforated Stub-out Connections 3-17 through 3-18 Yes Update text for consistency with revised Min
Req'mt #5
Text changes for consistency with new priority lists in Min. Req'ment #5
and feasibility criteria. Updated design guidance.
Section 3.2 Detention Facilities 3-19 through 3-64 Multiple revisions for plain language, clarity,
and brevity.Revised this chapter to use simpler and clearer language.
Section 3.2 Detention Facilities 3-35 Updated references.Updated Maintenance narrative to refer to Appendix IV-G Management
of Street Wastes in Volume IV.
Section 3.3 Infiltration Facilities for Flow Control
and Treatment 3-65 through 3-102 Section significantly rewritten.
Made significant changes to all sub-sections. Section pertains primarily to
design of centralized infiltration facilities. Certain sections also apply to
distributed bioretention facilities as indicated in text.
Section 3.3.1 Purpose 3-65 Yes Revised guidance and reference LID.
Expanded purpose statement and clarified in regard to the types of
facilities covered in Section 3.3. Added references to Bioretention and
Permeable Pavement sections.
Section 3.3.2 Description 3-65 Yes Additional guidance provided including Min
Req'mt #5.
Made clarifications and added language for complying with MR#5. Added
guidance for oil control and pre-treatment facilities.
Section 3.3.3 Applications 3-66 Additional guidance provided.Minor text change
Section 3.3.4 Steps for Design of Infiltration
Facilities 3-68 through 3-71 Yes
Revised several steps for new infiltration
rate guidance and the new LID performance
standard.
Revised Step 2 to include guidance for meeting MR#5. Significantly
revised Step 5 for the new guidance provided in section 3.3.6. Revised
Step 6 for clarity and for meeting MR#5. Revised Step 7 for clarity.
Volume III Hydrologic Analysis and Flow Control Design / BMPs
Chapter 3 - Flow Control Design
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Section 3.3.5 Site Characterization Criteria 3-72 through 3-75
Revised guidance on subsurface
characterization, soil testing, and infiltration
receptor. Removed guidance for
hydrogeologic investigation and figure 3.27,
USDA Textural Triangle.
Multiple changes to subsurface characterization include added guidance
on groundwater monitoring wells and the use of grain size analysis
method for estimating infiltration rates. Deleted infiltration rate
determination sub-section due to redundancy with next section.
Section 3.3.6 Design Saturated Hydraulic
Conductivity - Guidelines and Criteria 3-75 through 3-83
Revisions for determining the saturated
hydraulic conductivity (infiltration rate).
Section renamed.
Replaced "Infiltration Rate" with "Saturated Hydraulic Conductivity"
throughout section. Updated the guidelines and criteria for determining
saturated hydraulic conductivity. Added guidance on pilot infiltration
testing (PIT), and soil grain size analysis. Revised correction factors for
PIT results and soil grain size method. Removed options based on USDA
Soil Texture Classification and D10 grain size.
Section 3.3.7 Site Suitability Criteria (SSC)3-83 through 3-86 Additional guidance provided and outdated
guidance removed.
Updated references, removed unneeded guidance, revised limits on
infiltration rates, added a minimum organic content for treatment,
amended drawdown guidance, and verification testing.
Section 3.3.8 Steps for Designing Infiltration
Facilities - Detailed Approach 3-86 through 3-90
Multiple revisions. Previous steps 1-4
removed. Multiple steps revised. Added
groundwater mounding analysis step.
Removed steps to select location, estimate volume of stormwater,
develop a trial infiltration facility geometry, conduct a geotechnical
investigation, and determine the saturated hydraulic conductivity;
instead refers to steps 1-5 in section 3.3.4. Revised Figure 3.27 for
updated guidance. Revised guidance for adjusting the preliminary design
infiltration rate. Added a step for groundwater mounding analysis.
Added guidance for conducting performance testing.
Section 3.3.9 General Design, Maintenance, and
Construction Criteria for Infiltration Facilities 3-90 through 3-94 Additional guidance provided and outdated
guidance removed.
Added guidance for sizing for flow control, pretreatment design criteria,
and maintenance. Made wording clarifications to guidance.
Section 3.4 Site Procedures for Bioretention and
Permeable Pavement Use 3-103 through 3-109 Yes Added this section for bioretention and
permeable pavement.
Added guidance re field tests, computer modeling, and implementation
for bioretention / rain gardens and permeable pavement.
Appendix III-A Isopluvial Maps for Design Storms A-1 Added link to website.Added a link to a website where isopluvial maps are available.
Appendix III-B Western Washington Hydrology
Model - Information, Assumptions, and
Computation Steps
B-1 through B-13 Yes Additional guidance provided and outdated
guidance removed.
Added guidance on current and upcoming versions of WWHM. Added
guidance for the modeling on LID elements and wetlands. Removed
outdated computation steps.
Appendix III-C Washington State Department of
Ecology Low Impact Development Flow Modeling
Guidance
C-1 through C-13 Yes Additional guidance provided and outdated
guidance removed.
Text in regard to design guidance removed. All design guidance moved
to Volume V. Two sets of modeling guidance provided. One for WWHM
3, and one for upcoming WWHM 2012.
Appendix III-D Procedure for Conducting a Pilot
Infiltration Test N/A Appendix removed.
Procedures for conducting the PIT have been included within the
proposed text on “Design Infiltration Rate Determination” in sections
3.3.6.
Appendix III-B Western Washington Hydrology Model - Information, Assumptions, and Computation Steps
Appendix III-C Washington State Department of Ecology Low Impact Development Design and Flow Modeling Guidance
Appendix III-D Procedure for Conducting a Pilot Infiltration Test
Appendix III-A Isopluvial Maps for Design Storms
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Chapter 1 - Introduction 1-1 through 1-5 Minor language changes.Revised for clarity and removed outdated language.
Section 1.3 How to Use this Volume 1-2 Additional guidance provided and outdated
guidance removed.
Added new guidance regarding the Industrial Stormwater General Permit
(ISWGP), Boatyard General Permit (BGP), and Sand and Gravel General
Permit (S&GP) and the inclusion of "applicable" BMPs from this volume
in Industrial Stormwater Pollution Prevention Plans (Industrial SWPPPs).
Section 1.5 Treatment BMPs for Specific Pollutant
Sources 1-3 Yes Additional guidance provided and outdated
guidance removed.
Added new guidance clarifying the requirements regarding treatment
BMPs for facilities covered under the ISWGP (or other General
Stormwater Permits).
Section 1.6.1 Applicable (Mandatory) BMPs 1-3 through 1-4 Additional guidance provided and outdated
guidance removed.
Added new guidance describing the use of applicable (mandatory) BMPs
in regards to the ISGP, BGP, and S&GP. Section renamed to make it
clearer that applicable BMPs are Mandatory for permittees under the
ISWGP and BGP.
Section 1.6.2 Recommended BMPs 1-4 Yes Additional guidance provided.Added guidance regarding facilities covered under the ISWGP that trigger
a corrective action.
Chapter 2 - Selection of Operational and Structural
Source Control BMPs 2-1 through 2-66 Numbered BMPs.Added numbers in the "S400" series to BMPs in Volume IV.
Chapter 2 - Selection of Operational and Structural
Source Control BMPs 2-1 through 2-66 Minor revisions for plain language, clarity,
and brevity.
Revised BMPs to use simpler and clearer language, and removed
outdated references.
Chapter 2 - Selection of Operational and Structural
Source Control BMPs 2-1 through 2-2 Additional guidance provided and outdated
guidance removed.
Added new guidance describing the use of applicable (mandatory) BMPs
in regards to the ISGP, BGP, and S&GP. Added guidance regarding
facilities covered under the ISWGP that trigger a Level 1 or 2 corrective
action.
Section 2.1 Applicable (Mandatory) Operational
Source Control BMPs 2-2 through 2-6 Additional guidance provided and outdated
guidance removed.
Revised wording to clarify where this Section applies. Revised several
BMPs for clarity and to coordinate with the ISWGP. Significant changes
include the addition of vacuum sweeping and pressure washing, spill
prevention and cleanup, visual inspections and record keeping.
Section 2.2 Pollutant Source Specific BMPs 2-7 through 2-66
Additional guidance provided and outdated
guidance removed. Minor formatting
revisions.
Revised wording to clarify where this Section applies. Added new text on
ISWGP requirements. Added guidance regarding facilities covered under
the ISWGP that trigger a Level 1 or 2 corrective action. Changed the title
format for the BMPs to match the other volumes and added a numbering
system to the BMPs.
S401 BMPs for the Building, Repair, and
Maintenance of Boats and Ships 2-7 through 2-9 Additional guidance provided and several
BMPs clarified.
Clarified guidance describing the requirements under the BGP and ISGP
regarding boatyard activities. Revised BMPs to use simpler and clearer
language.
S402 BMPs for Commercial Animal Handling Areas 2-10 Minor revisions for plain language, clarity,
and brevity.Revised BMPs to use simpler and clearer language.
S403 BMPs for Commercial Composting 2-10 through 2-12 Additional guidance provided and outdated
guidance removed.
Revised language because solid waste regulations prohibit discharge of
compost leachate. Revised BMPs to use simpler and clearer language,
and removed outdated references.
Volume IV Source Control BMPs
Chapter 1 - Introduction
Chapter 2 - Selection of Operational and Structural Source Control BMPs
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S405 BMPs for Deicing and Anti-Icing Operations -
Airports and Streets 2-13 through 2-14 Additional guidance provided and outdated
guidance removed.
Revised language to coordinate with the ISGP. Removed outdated
references.
S414 BMPs for Maintenance and Repair of Vehicles
and Equipment 2-32 through 2-34 Yes Revision for consistency with the ISGP Updated "applicable BMP" guidance for handling of liquids in scrap
vehicles to align with ISGP.
S416 BMPs for Maintenance of Roadside Ditches 2-35 through 2-37 Additional guidance provided and updated
references.Additional guidance provided for the handling of ditch cleanings.
S423 BMPs for Recyclers and Scrap Yards 2-45 through 2-46 Updated reference to guidance.Updated the reference to guidance for Vehicle Recyclers.
S424 BMPs for Roof/Building Drains at
Manufacturing and Commercial Buildings 2-46 through 2-47 Added reference to guidance.Added a references to Volume V and Ecology publications for BMPs.
S426 BMPs for Spills of Oil and Hazardous
Substances 2-48 through 2-49 Additional guidance provided and outdated
guidance removed.Revised several BMPs for clarity and to coordinate with the ISWGP.
S430 BMPs for Urban Streets 2-58 through 2-59 Additional guidance provided.Clarified that facilities not under the ISWGP may consider some water
use in street cleaning.
S431 BMPs for Washing and Steam Cleaning
Vehicles / Equipment / Building Structures 2-60 through 2-62 Yes Additional guidance provided and outdated
guidance removed.
Added guidance to clarify that the ISWGP prohibits the discharge of
process wastewater to ground water or surface water. Removed
outdated guidance.
Figure 2.15 - Uncovered Wash Area N/A Figure Deleted Figure was unclear and the existing text provided a better description of
the required controls.
S432 BMPs for Wood Treatment Areas 2-63 through 2-64 Additional guidance provided and several
BMPs clarified.
Clarified guidance describing which NPDES permit(s) regulate wood
treatment areas. Revised BMPs to use simpler and clearer language.
S433 BMPs for Pools, Spas, Hot Tubs and Fountains 2-64 through 2-66 Additional guidance provided.Added this BMP to provide further guidance consistent with BMPs within
this volume.
Appendix IV-A Urban Land Uses and Pollutant
Generating Sources A-1 through A-24 Minor language changes.Edits for clarity and to replace and revise guidance documents and WAC
references.
Commercial Composting - SIC 2875 A-14 Additional guidance provided Added "Potential Pollutant Generating Sources"
Appendix IV-B Stormwater Pollutants and Their
Adverse Impact B-1 through B-2 Minor language changes. Removed Table.Minor language changes for clarity. Removed the outdated Table in
Appendix IV-B.
Appendix IV-C Recycling/Disposal of Vehicle
Fluids/Other Wastes C-1 Minor language changes.Minor language changes for clarity.
Appendix IV-D Regulatory Requirements That
Impact Stormwater Programs D-1 through D-9 Minor language changes.Edits for clarity and to replace and revise guidance documents and WAC
references.
Appendix IV-E NPDES Stormwater Discharge
Permits E-1 through E-7 Yes Additional guidance provided and outdated
guidance removed.
Edits to make guidance consistent with the most recent industrial and
municipal stormwater permits.
Appendix IV-G Recommendations for Management
of Street Wastes G-1 through G-15
Multiple revisions for plain language, clarity,
and brevity. Additional guidance provided
and outdated guidance removed.
Removed outdated guidance and added new guidance in the
contamination in Street Waste Solids subsection. Reorganized the
disposal of street waste liquids subsection, no major content changes.
Minor revisions to the Site Evaluation subsection.
Appendix IV-C Recycling/Disposal of Vehicle Fluids/Other Wastes
Appendix IV-D Regulatory Requirements That Impact Stormwater Programs
Appendix IV-E NPDES Stormwater Discharge Permits
Appendix IV-G Recommendations for Management of Street Wastes
Appendix IV-A Urban Land Uses and Pollutant Generating Sources
Appendix IV-B Stormwater Pollutants and Their Adverse Impact
Location Approximate Page
Numbers
Change Tied
to Permit
Language
Change Reasoning or Comments
Chapter 1 - Introduction 1-1 through 1-4 Minor revisions for plain language, clarity,
and brevity.
Revised BMPs to use simpler and clearer language, and removed
outdated references.
Section 1.4.3 Treatment Methods 1-2 through 1-4 Additional guidance provided and outdated
guidance removed.
Revised guidance for oil/water separation, pretreatment, infiltration,
filtration, emerging technologies, and on-line systems. Added
Bioretention as a treatment method.
Chapter 2 - Treatment Facility Selection Process 2-1 Additional guidance provided.Added paragraph on emerging technology options.
Section 2.1 Step-by-Step Selection Process for
Treatment Facilities 2-1 through 2-9
Minor revisions to the steps. Revised
description of surface waters triggering
enhanced treatment.
Revised selection process steps for clarity and to remove outdated
information. Revised the Treatment Facility Selection Flow Chart for
revised guidance throughout Volume V. Revised description of surface
waters triggering enhanced treatment for accuracy.
Figure 2.1.1 2-3 Revised list of options.
Some treatment BMP options removed, emerging technologies added,
one BMP renamed. Added a note for Phosphorous facilities that require
Enhanced Treatment.
Section 2.2 Other Treatment Facility Selection
Factors 2-9 through 2-11
Removed the subsection on Pollutants of
Concern, the Suggested Treatment Options
Table, and Ability of Treatment Facilities
Table.
Removed the Suggested Treatment Options Table and Ability of
Treatment Facilities Table because they provided limited usefulness and
removed the associated subsection, Pollutants of Concern.
Chapter Introduction Paragraph 3-1 Additional guidance provided.Added paragraph on emerging technology options.
Section 3.2 Oil Control Menu 3-2 through 3-3 Revised list of options.
Removed catch basin inserts and added emerging stormwater treatment
technologies. To date, no catch basin inserts have been approved though
the TAPE process but Ecology has approved one emerging technology.
Deleted the "Where Applied" section since it was duplicated from
Chapter 2.
Section 3.3 Phosphorous Treatment Menu 3-3 through 3-4 Revised list of options.
Removed amended sand filter (no design criteria have been developed
for this treatment), and media filter, added emerging stormwater
treatment technologies. Deleted the "Where Applied" section since it
was duplicated from Chapter 2.
Section 3.4 Enhanced Treatment Menu 3-5 through 3-7
Multiple revisions to remove outdated
guidance and to provide new guidance.
Revised list of options. Revised waters
triggering enhanced treatment consistent
with Chapter 2.
Revised the performance goal for dissolved metals. Removed Amended
Sand Filter. Added "vegetated" to "Compost Amended "Vegetated" Filter
Strip. Removed "rain garden" for consistency with proposal to distinguish
between "bioretention" and "rain gardens." Replaced "Ecology
Embankment" with "Media Filter Drain." Added emerging technologies.
Deleted the "Where Applied" section since it was duplicated from
Chapter 2.
Section 3.5 Basic Treatment Menu 3-7 through 3-9 Minor language changes for clarity. Revised
list of options.
Removed "rain garden" for consistency with proposal to distinguish
between "bioretention" and "rain gardens." Replaced "Ecology
Embankment" with "Media Filter Drain". Added Compost-amended
Vegetated Filter Strip. Removed Bio-infiltration Swale. Added emerging
technologies. Deleted the "Where Applied" section since it was
duplicated from Chapter 2.
Section 4.1.1 Water Quality Design Storm Volume 4-1 Yes Inserted updated modeling guidance.New guidance more accurately describes how volume is determined by
computer models.
Chapter 1 - Introduction
Chapter 2 - Treatment Facility Selection Process
Chapter 3 - Treatment Facility Menus
Chapter 4 - General Requirements for Stormwater Facilities
Volume V Runoff Treatment BMPs
Location Approximate Page
Numbers
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Section 4.1.2 Water Quality Design Flow Rate 4-1 through 4-2 Minor language changes for clarity.Revised language for clarity.
Section 4.1.3 flows Requiring Treatment 4-2 through 4-4 Minor language changes for clarity. Changes
to incorporate new terms.
Replaced "impervious" surfaces with "hard" surfaces in coordination with
general changes in terminology. Added guidance regarding pollution-
generating hard surfaces, pollution-generating impervious surfaces, and
pollution-generating pervious surfaces.
Section 4.6 Maintenance Standards for Drainage
Facilities 4-31 through 4-53 Yes Added new tables within overall set of
operation and maintenance standards
Changed "StormFilter" to "Manufactured Media Filters", added
information from WSDOT on Media Filter Drains and Compost Amended
Vegetated Filter Strips. Minor additions to the recommended
maintenance tables added. Added placeholders for Bioretention and
permeable pavement pending completion of the development of LID
maintenance standards grant.
Section 5.1 Purpose 5-1 Additional guidance provided.
Add reference to expanded BMP options and LID Manual to acknowledge
the expansion of Chapter 5 and source of additional design details (LID
Manual).
Section 5.2 Application 5-1 Yes Additional guidance provided.Revised application to refer specifically to Minimum Requirements #5,
#6, and #7.
Section 5.3 Best Management Practices for On-Site
Stormwater Management 5-1 through 5-2 Additional clarifying guidance provided. Full
list of BMPs provided.
Expanded the list of BMPs in sections 5.3.1 and 5.3.2. Revised language
and references for clarity.
Section 5.3.1 On-site Stormwater Management
BMPs 5-3 to 5-39 Yes Amend existing BMP's add new BMP's
Downspout infiltration moved to Volume III. Revised BMP T5.11
Concentrated Flow Dispersion and BMP T5.12 Sheet Flow Dispersion.
Updated figures. Added BMP T5.14A Rain Gardens and BMP T5.14B
Bioretention but details are in Volume V of Chapter 7. Added BMP T5.15
Permeable Pavements, BMP T5.16 Tree Retention and Tree Planting,
BMP T5.16 Vegetated Roofs, BMP T5.18 Reverse Slope Sidewalks, BMP
T5.19 Minimal Excavation Foundations, BMP T5.20 Rainwater Harvesting.
Revised BMP T5.30 Full Dispersion by incorporating details from previous
Appendix III-C.
Section 5.3.2 Site Design BMPs 5-39 through 5-42 Deleted Full Dispersion and section 5.3.3
Other Practices
Moved Full Dispersion into Section 5.3.1 because the Municipal
Stormwater Permits make it a necessary option in MR #5. Clarifying
statement added in BMP T5.40.
Section 6.1 Purpose 6-1 Minor language changes.Removed "and media filtration" in first bullet for clarity.
Section 6.2 Application 6-1 Additional guidance provided.Added discussion that there are emerging technologies approved for
pretreatment.
Section 6.3 Best Management Practices (BMPs) for
Pretreatment 6-1 Additional guidance provided.Added reference to Chapter 12.
Section 7.1 Purpose 7-1 Changed bioinfilltration to bioretention.Updated listed BMPs and made minor revisions to text.
Sections 7.2 General Considerations 7-1 Additional guidance provided.Renamed this Section and added information regarding Bioretention and
Rain Gardens.
Sections 7.3 Applications 7-1 through 7-2 Additional guidance provided.Renamed this Section and added information for the BMPs discussed in
this chapter.
Chapter 6 - Pretreatment
Chapter 7 - Infiltration and Bioretention Treatment Facilities
Chapter 5 - On-Site Stormwater Management
Location Approximate Page
Numbers
Change Tied
to Permit
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Change Reasoning or Comments
Section 7.4 and BMPs 7.10 & 7.20 7-2 Updated references to Volume III Design details for these BMPs remain in Volume III.
BMP T 7.30 Bioretention Cells, Swales, and Planter
Boxes 7-3 through 7-25
Replaced Bio-infiltration Swale with
Bioretention Cells, Swales, and Planter
Boxes.
Added detailed guidance, design criteria, infeasibilty criteria and figures
for Bioretention Cells, Swales, and Planter Boxes.
BMP T7.40 Compost-amended Vegetated Filter
Strips (CAVFS)7-25 through 7-29 Transferred this BMP from Chapter 9.Added guidance and design criteria for Compost-Amended Vegetated
Filter Strips. Treatment via infiltration through amended soils.
Chapter 8 - Filtration Treatment Facilities 8-1 through 8-39 Changed title and introduced minor
language changes for clarity.Revised name from Sand Filtration to just Filtration.
8.1 Purpose 8-1 Revised guidance.Revised the purpose to apply to both sand and media filtration facilities.
8.2 Description 8-1 Additional guidance provided.Added reference to Media Filter Drain to description.
Section 8.3 Performance Objectives 8-2 Included new technologies Added Media Filter Drain to list of approved technologies. Clarified
objective for sand filters.
Section 8.4 Applications and Limitations 8-2 Revised guidance.Revised to include media filter drains.
Section 8.5 Best Management Practices (BMPs) for
Sand Filtration / BMP T8.10 Sand Filter Basin 8-2 to 8-15 Renamed and reorganized section.
Additional guidance provided.
Added design criteria for sand filter basins. reorganized section so that
previous sections 8.5, 8.6, 8.7, & 8.8 become subsections under BMP
T8.10.
BMP T8.11 Large Sand Filter Basin 8-16 through 8-17 Separated out BMP previously reference
within BMP T8.10
BMP T8.11 Large Sand Filter Basin was described in the prior manual
under BMP T8.10 Sand Filter Basin. The Large Sand Filter was given a
separate BMP for clarity.
BMP T8.20 Sand Filter Vault 8-17 through 8-23 Additional guidance provided.Added design criteria, construction criteria, and maintenance criteria for
sand filter vault.
BMP T8.40 Media Filter Drain 8-24 through 8-38 Added this BMP.
Added design criteria for new Media Filter Drain (MFD) option
(previously referred to as Ecology Embankment). Text matches WSDOT
Highway Runoff Manual.
Chapter 9 - Biofiltration Treatment Facilities 9-1 through 9-26 Minor language changes for clarity.Minor language changes for clarity throughout the chapter.
Section 9.4 Best Management Practices 9-1 through 9-26 Additional guidance provided and outdated
guidance removed.Revised list of BMPs. Revised Sizing Criteria table for clarity.
BMP T9.50 Narrow Area Filter Strip N/A Removed this BMP.No design criteria exists for this BMP to validate basic treatment.
Designers should refer to Basic Filter Strip.
BMP T10.10 Wet Pond 10-1 through 10-17 Minor language changes for clarity.
First cell must be lined to be consistent with liner requirements in
Chapter 4. Added cell requirements for consistency with design criteria
for 2-cell ponds. Definition of WQ Design Storm Volume amended.
BMP T11.10 API (Baffle type) Separator Bay 11-8 through 11-9 Corrected formula.Corrected Stokes Law equation for rise rate.
BMP T11.11 Coalescing Plate (CP) Separator Bay 11-10 through 11-11 Corrected formula.Corrected the equation to calculated the projected (horizontal) surface
area of plates.
Chapter 12 - Emerging Technologies 12-1 through 12-6 Replaced sections 12.1 through 12.5 with
new guidance.
Replaced sections 12.1 through 12.5 to provide new guidance on the
Technology Assessment Protocol (TAPE) review and approval process.
Chapter 11 - Oil and Water Separators
Chapter 12 - Emerging Technologies
Chapter 8 - Sand Filtration Treatment Facilities
Chapter 9 - Biofiltration Treatment Facilities
Chapter 10- Wetpool Facilities
Location Approximate Page
Numbers
Change Tied
to Permit
Language
Change Reasoning or Comments
Section 12.6 Examples of Emerging Technologies
for Stormwater Treatment and Control N/A Removed examples of emerging
technologies.
Removed examples of emerging technologies. Added some examples
previously listed throughout this volume.
Appendix V-B Recommended Modifications to
ASTM D 2434 When Measuring Hydraulic
Conductivity for Bioretention Soil Mixes.
B-1 through B-2 Additional guidance provided.
Added Recommended Modifications to ASTM D 2434. The results of this
test for saturated hydraulic conductivity can be influenced by how the
general procedures in the ASTM method are implemented. This
appendix lays out more specific procedures to help with consistency in
evaluating soils used for bioretention.
Appendix V-C Geotextile Specifications C-1 through C-3 Revised Guidance.Corrected several test procedures and geotextile property requirements.
Appendix V-E Recommended Newly Planted Tree
Species E-1 through E-5 New appendix pertinent to BMP T5.16 Lists of species from City of Seattle guidance.
Appendix V-C Geotextile Specifications
Appendix V-B Recommended Procedures for ASTM D 2434
Appendix V-E Recommended Bioretention Plant Species
VARIES TIER 1 NATURAL DRAINAGE AND WATER BODIES
•Admiralty Inlet
•Port Townsend
•Kah Tai Lagoon
•Chinese Gardens
•Floodplains
•Wetlands
GREEN TIER 2 CRITICAL DRAINAGE AREAS
•Natural Topography and Land Forms
PINK TIER 3 CREATED DRAINAGE CONNECTIONS
•Controlled Connections between Tier 4 and 1 or 2
PURPLE TIER 4 ROAD DRAINAGE
A. Main Roads
B. Other Public Roads
•Public Street Drainage
Date: Tuesday, September 26, 2017
Location: Cotton Building, 607 Water Street, Port Townsend
Be part of the Stormwater Management Plan public process. Come and
give your input on the City’s proposed Stormwater Capital Improvement
projects, the Stormwater Utilities Vision Statement and more.
Stormwater Management Plan
Public Open House
For more information on and about the Stormwater Management Plan please visit the City’s Stormwater
Management Plan website https://stormwatermanagementplan.wordpress.com/ While you are viewing
the website provide your email at the bottom of the main page and follow the process.
Tell us what is important to you when creating the Stormwater Management Plan
The City is in the process of preparing a Stormwater
Management Plan.
The scope of the Plan includes going over existing
conditions of the City’s Stormwater infrastructure,
identifying Stormwater capital projects, outlining
changes to the Engineering Design Standards (EDS)
Chapter 4 Stormwater and the Municipal Code Title 13
Article IV, and financing for the Stormwater utility
including capital projects. The review of the EDS and
the municipal code will include reviewing the
development guidelines and regulations.
Are there topics you are wondering if the City will cover? Please let us know. Send your comments and
suggestions to sharper@cityofpt.us by Wednesday September 27, 2017. Also sign-up on the City’s
Stormwater Management Plan website to receive updates on the project. The website is
https://stormwatermanagementplan.wordpress.com/ There will also be more opportunities to
comment throughout the Stormwater Management Plan process.
AGENDA
Stormwater Management Plan - Advisory Task Force
Workshop 2 | November 2, 2017 | Cotton Building, 607 Water Street, Port Townsend
2:00 – 2:15 Welcome and Agenda
2:15 – 2:30 Introductions
2:30 – 2:45 Meeting Purpose and Goal
2:45 – 3:15 Recap from Task Force Meeting #1
3:15 – 3:30 Go over public comment to date
3:30 – 3:45 Brief overview of the proposed Stormwater Capital
Improvement Program (CIP)
3:45 – 4:15 Financing
4:15 – 4:30 Development Standards
4:30 – 5:00 Meeting Summary
5:00 Adjourn
2016 SWMP Update Comments
Comment
method
Date Comment Response
Written 9/26/2017 #1 I have a concern about putting this wet weather stream underground. It has value for everything from insects to
larger wildlife and now support 100+ year old Douglas Firs. I expect a project where large equipment works thru the
now semi wild ravine will meet with resistance from residents whose property adjoin the ravine (locally known as
Kah Tai Creek).
Written 9/26/2017 Pettygrove 43rd Street to 47th Street Area floods, pipe connection to storm pipe going to Chinese gardens #2 on CIP
Map
Written 9/26/2017 Generally, I favor diverting more fresh water runoff into the Kah Tai Lagoon Nature Park. That is provided it is filtered
through sufficient bio swales to remove oil and other containments. There seems to be a protentional site for
expanded inflow at the east southeastern end where a small wetland already exist.
Written 9/26/2017 The corner of 47th & Jackman is still flooding and Jackman road surface is showing the impact. We still get water run
off. My crawl space is finally dry, but I pump the water down hill. There is still a storm water fee we pay every month
and receive no benefit.
Written 9/26/2017 Please see Comment Map #5: I would like the City to consider & discuss the potential negative impact of adopting
the 2014 Storm water Regs (Vs. 2005) on the cost of housing. The 2014 Stormwater Manual was written for very
high Density truly Urban areas such as Seattle/ Tacoma. Cities of the scale of Port Townsend are not required to
adopt these regs because they are not written for this Cities small size & Relative Low Density.
Written 9/26/2017 I live at the Kearney St. Apts. And have observed the tremendous amount of storm water that flows down through
the neighborhood carving out new channels in dirt roads (1) which is the one that accesses the Police Station from
Gaines St (2) the one that is situated behind Crossroads Music Store (& ends at Kearney) and the (3) one between
the apartments complex on Walker & Lawrence - and three houses to the NW.
The water that flows down the "Police Station Road" carries so much dirt and it flows through the shrubs on the bank
above the Kearney St Parking Lot. * *It takes out the stones in the stone wall on Kearney!
Point is - All of that water, which carries a lot of grease, and oil from parking lots and streets, ends up... Where? in
Kah Tai? In the Bay?
I believe I was told on one occasion when I asked about this, that there is a "holding area" - under the sidewalk on
Kearney to the East of Sims Way, but it can overflow and empty through that pipe which empties (more & more
often) into the Bay. I would really like to understand how this storm water system works in our neighborhood.
In connection with this -- we need to understand the "hydraulics" of Kah Tai Lagoon- Should the pipe that allows it,
the tide, to moderate the level and water type in the lagoon is repaired more fresh or more salty? I think we have
been ignoring that issue, yet it will greatly affect the ability of the lagoon to handle runoff in the future.
2016 SWMP Update Comments
Comment
method
Date Comment Response
E-mail 9/27/2017 Hi Samantha,
Please note that i am concerned that new and more restrictive Storm Water Management requirements will
exacerbate the Affordable Housing Crisis in Port Townsend...
Please send me the Draft SW Plan Narrative and Drawings that was shown at your workshop Yesterday...
I was unable to attend... also, please add me to the Email list that will keep me informed Of the timeline of the
process..
I was unable to access the website referenced in the newspaper....
Thank you
Vern Garrison
360-301-2009
Hello Vern,
Here is the link that I
promised to send following
our discussion this morning.
https://stormwatermanagem
entplan.wordpress.com/
Let me know if you have
difficulty accessing from this
link.
Joanna Sanders, MMC | City
Clerk
E-mail 9/28/2017 I have just recently learned of plans to contain Kai Tai Creek in a pipe. I cannot remotely understand why the city
would want to spend needed funds on a project that will totally disrupt the neighborhood ruin a very natural area,
and to most of us in the area, serve absolutely no purpose. The city must have
a secret fund salted away that it doesn't know what to do with. Please reconsider this.
Thank you, Mark Henthorn, 1805 Wilson, Port Townsend
E-mail 9/27/2017 This is to inform you that I am against putting Kah Tai Creek in a pipe.
I've lived at 928 14th St since 2004 & greatly cherish the trees on Castle Hill. Many would have to fall to pipe that
creek. It also would be a terrific mess and annoyance for those who live along the creek. In addition, there have been
no visible problems with the creek since work was done a few years ago on the lower portion. Finally, it's a natural
drainage that starts near my house & flows down the unused right of way for 16th St. Why not wait till the street is
actually put in to do any drainage changes? The money would be much better spent on fixing the many, many
potholes in this city, rather than tearing up natural vegetation that soaks up lots of pollutants before they hit the
lagoon & its wildlife. I could go on - - -
To my mind there are many arguments against this proposed project & I've seen nothing supporting it nor any need
for it. Will there be a hearing on this?
Your response will be appreciated.
Mike Morrissey
928 14th St
E-mail 9/27/2017 Dear city of P.T.
I just heard about the city plan to place kai tai creek into a pipe instead of letting it be what it is....a really nice in
town riparian corridor. I think rather then spend millions( no doubt) to channel the creek the city should save money
by the simple expediency of making that drainage into a wildlife corridor. It strikes me as a vase of needless
infrastructure. Got extra money? Spend it on maintance rather then development.
Aron uchitelle 1435 gise
2016 SWMP Update Comments
Comment
method
Date Comment Response
E-mail 9/27/2017 Hello Samantha.....please add my name to the list of people who want to participate in the review of the storm
water regulations of the City of Port Townsend.
The new regulations of the 2014 SWMMWW DOE Manual to not provide sufficient alternatives to areas like the City
of PT which have no rivers or natural streams. And most of the wetlands are no more than periodic wet basins that
very quickly dissipate into the upper soils of the area.
Please put me on the notice list.
Thanks for your help.
Michael J. Anderson
PE & PLS
E-mail 9/27/2017 I just heard from neighbors that the city is planning to put Kah Tai Creek in a pipe so it isn't free-flowing anymore.
I want to go on record that I am vehemently opposed to this plan.
Thank you,
Todd Jensen
1735 Wilson St. PT
E-mail 9/27/2017 Samantha,
My name is Nathan Land and I live at 1524 Sheridan Street.
In response to the staff update to the storm water management plan discussed in the Port Townsend Planning
Commission regular session on September 14, I would like to suggest that Kai Tai creek not be put into a drainage
pipe between Gise Street and Hill Street. Instead, the city should not modify the flow of the creek, allowing it to
remain a free-flowing creek.
In PTMC 19.05.100, there is a proposed amendment to the code that would require surface drainage to be directed
away from landslide and erosion areas when the surface drainage meets a set of drainage and geomorpohological
criteria consistent with SMP DR6.8.2. I claim that this amendment is unethical, because it is placing the property
value of a small number of homes above the very rare existing natural surface aquifers in the area.
Further, I claim that the area between Gise and Hill street should be protected by the very same part of the
municipal code, 19.05.100.E.2.C, which states that existing vegetation in surface drainage areas should remain
undisturbed. If this is a case where the vegetation has been disturbed or is insufficient, then I claim it is a reasonable
argument to state that instead of installing a drainage pipe, revegation with native species would be more
appropriate.
There are very few natural creeks on the quimper peninsula, and putting this creek into pipe will effectively kill the
creek permanently. I understand that from a stormwater management engineering perspective, a pipe is an effective
way to drain overflow water. However, from a biological perspective, the creek has more inherent value as a diffuse
drainage method and provides enumerable benefits to wildlife and soil quality.
We are stewards of this land, and we have a responsibility to ensure that we do not destroy natural processes in an
attempt to anticipate a possible risk to property value of a small number of homes as a result of stormwater
flooding. Please do not approve amendment 19.05.100.E.2.B.v to the PTMC.
Thanks very much,
Nathan Land.
2016 SWMP Update Comments
Comment
method
Date Comment Response
E-mail 9/27/2017 hi there city of port townsend, in regards to the pipe from gise to kah tai. i live on gise and 14th. i understand
progress. i also know that the precious green belts in this town have incredible value to wild life and to making this
town special. i would like more information on what swath of destruction is proposed and more about the issue as
an impacted tax paying citizen. thanks, zo wohlhaupter
E-mail 9/27/2017 Please reconsider the idea of piping the creek from Gise down. The development along that area has already
minimized the wildlife corridor and this will definitely limit even further the movement of the deer in particular.
There will be even more deer getting into people's gardens causing even more demand on the city government to
do something about the problem. Limiting the availability of open water will probably result on more work for you
guys in the end. Thanks for considering this concern. Laurette Gilbert
E-mail 9/27/2017 To: The City of Port Townsend
From: Heida Diefenderfer, 1524 Sheridan St, PT
Date: 26 Sept 2017
The Quimper Peninsula has very few natural surface water sources. One of those is in our neighborhood: Kai Tai
Creek. It should be protected, not put in a pipe. The source itself is degraded and would benefit from the
establishment of native plants in the area.
We are against the draft plan to put Kai Tai Creek into a pipe in the vicinity of Gise to Hill Streets in Port Townsend.
I would appreciate receiving confirmation that my comment has been received in a timely manner. Please add me to
the list for updates to the plan and let me know when the next version is due.
Thank you very much.
Heida
E-mail 9/27/2017 Mr Sharper,
I currently live on hill st and I'm on the receiving end of much of the downhill storm water from Gise. Even with that,
I oppose the cities plan to pipe the water from Gise to Hill. For one thing, once you've paid for the installation ( big
bucks) then you have to maintain ( big bucks) forever. Look at the 16th, Hill St drain. That is a quagmire of problems.
The city has spent a fortune on this project over time. I know because I see your trucks there a lot, clearing out dirt in
drains. It's also a huge liability. An alternative, how about having a series of rain gardens that would be cheaper to
install; imagine, beauty and minimal maintenance costs. It would also keep a free flow of runoff that could be
managed or changed if needed. I also think that the city could have done a better job in communicating with
affected neighborhoods. I didn't get any info on this project for comment, or know about the deadline for comment.
Do not put in pipe,please! Thanks,
Dave Sterritt
1636 Hill St
360 821-8790
E-mail 9/27/2017 Please keep the creek free! I live near this creek. My son and neighborhood kids have grown up around it playing in
it. I personally have lived in this neighborhood for twenty years and in the last couple years have watched every
available lot be purchased and slated for development. I see no reason to bury this creek any more than out already
is other than so land can be developed right up to it. As our town is transforming let's make choices that keep this
not only a livable community but one that retains it's physical beauty of natural spaces. For is that not why so many
people want to move here? SAVE KAH TAI CREEK!!
2016 SWMP Update Comments
Comment
method
Date Comment Response
E-mail 9/27/2017 I would request that the city of PT keep the stormwater from gise st. to hill st free flowing and NOT pipe it.
Patrick Hinton
1805 Gise st.
E-mail 9/26/2017 I am opposed to the unwise suggestion that Kah Tai Creek be run into a pipe underground from Gise to Hill streets.
Ecologically the presence of the free flowing water maintains a wild natural space around it which acts as a green
belt for wildlife and a sediment trap for runoff water. Aesthetically, it brings the sound and sight of flowing water to
the surrounding area. It is a beauty and grace for the neighborhood.
I suspect the city is being influenced by developers who see the building lots that would be created by destroying the
creek. Resist this influence. Port Townsend is not that desperate for building lots.
Thank you for your attention to this.
Sincerely
Kristin Smith
360 301 5128
1715 and 1708 Gise Street
E-mail 9/26/2017 Dear Sir, I live on Gise and 18 th St and have lived here for 25 years. My children were raised here and played in that
creek when they were young. I cant understand why you want to put the creek in a pipe. If you do leave it alone and
let the plants and animals use it as it was intended to be used then some day down the road, some other small
children will grow up knowing what a creek sounds like and the joy they can find in nature. For the sake of those
children leave the creek alone it has been here far longer than you have!
Thank you ,
Jay Pine
1723 Gise St.
E-mail 9/26/2017 Hi, I live at 1607 Gise and just heard the city is planning on piping Kai tai creek. I'm really opposed to that, given the
bird life especially that the flowing water supports, even storm water. Is there a way not to make that choice that
would still work for city storm water management? So many cities are daylighting streams that it seems a shame and
shortsighted for PT to go backwards. I hope the city will reconsider.
Sincerely, Julie Van Pelt
E-mail 9/26/2017 We live only one block from this intermitant creek,but we enjoy it when it flows and see no need to put it in a pipe,
save our tax dollars for some other project! Jerry Gilbert, 935 18th Street, PT, ps we have owned our house here for
over 40 years always at this same address.
2016 SWMP Update Comments
Comment
method
Date Comment Response
E-mail 9/26/2017 Samantha:
The City's Shoreline Management Program (SMP) is incorporated into the Comprehensive Plan. Both clearly require
use of the Department of Ecology's Stormwater Management Manual for Western Washington (SWMMW). I think
the pending functional plan, EDS, flood code, and Critical Areas Ordinance should do so as well, at least until DOE
certifies the local plan as equivalent.
As for specific stormwater projects, I would like the city to end all untreated stormwater discharges into those
shoreline areas already identified in the SMP.
Good luck with your important project.
Nancy Dorgan
E-mail 9/26/2017 My husband attended the public open house for the City of Port Townsend Stormwater Management Plan and came
home with some very distressing news. He was told one of the top priorities is to put Kah Tai Creek in a pipe from
Gise Street to Hill Street. Please don't do that. It is a wildlife corridor and has 100 year old trees growing. I do not
know of any neighbors that have been flooded by Kah Tai Creek in recent history. We live at 1709 Gise Street, one
block from Kah Tai Creek and often cross over Kah Tai Creek on Holcomb Street. Please don't destroy our
neighborhood creek.
Sincerely,
Rosemary Sikes
1709 Gise Street
360-385-0307
E-mail 9/26/2017 Hi Joanna,
I didn't find the scoping notice posted with in the 2017 folder on-line. Would you email me a copy?
Thanks.
Nancy
Hello Nancy,
I am not aware of any scoping
notice at this point. Samantha
Harper is the City engineer
responsible for this project
and might be able to answer
specific questions and I am
copying her on this message.
There is information at the
Stormwater Management
Plan project page.
https://stormwatermanagem
entplan.wordpress.com/
If you do not believe this
satisfies your request, please
let me know.
Joanna Sanders, MMC | City
Clerk
2018 - 2023 Stormwater CIP List
ACQUISITIONS
4-8 Winona Wetland Property Acquisition - Purchased in 1995 On-going
9-2 Hastings to 25th Thomas to Hancock - wetland and critical drainage protection property
9-2 Hancock/25th/Sheridan, Pasture - combine with # 4 under Acquisitions
STORMWATER PROJECTS
Localized Flooding
9-20 16th Street - Sheridan to Landes X H
4-21 Drainage Cooridor between 49th St. and 50th St. and Jackman St. to Gise St.
11-3 12th St right-of-way from McPherson to Logan and Logan Street from 10th to 12th Sts.X M
8-6 Golf Course Pond - Needs flow control on the upper elevation
-Center St San Juan to Olympic Ave. - Flooding/drainage problem C X M
-Hancock Street and 32nd Street - Flooding Issues - 31st Street storm water tied into the sewer X M
Improve Conveyance
11-4 McPherson/9th, Stormwater to SSMH tie-in is north of 9th Street
-14th Street McPherson Street to Rosecrans Street X M
-Logan Street Stormwater Pond overflow - cross street is 3rd Street X in the 2018 budget
-Pacific Street - Tremont Street to Milo Street - need storm pipe to Froggy Bottoms
Stormwater Tie Into the Sewer System
-Storm tied in to sewer on Lawrence Street at Polk Street, Tyler Street and Taylor Street X
Improve Treatment through Retrofit
-Garfield Street Bioswales - Could be part of the removing storm to sewer tie-in on Lawrence Street D
Regional Stormwater Systems
-Regional Stormwater Facility for Rainier Street Commercial Corridor X in progress
Existing system improvements
-Major Collector and Minor Arterials (Purple Roads) Stormwater Improvements On-going
-Local Access Street (Brown Roads) Stormwater Improvements On-going
2017 Site
Visit Map
2017 CIP?
(Select 10)
Importance
(High/Med/Low)Description1999
Project No.
Stormwater Management
Plan Briefing
City Council Meeting
December 11, 2017
Purpose for tonight
1.Stormwater Plan Implementation Process and What is next
2.Briefing on key concepts and technical issues and unique
Stormwater features
Project Initiation
Stormwater Utility Vision Statement
A fully functional, achievable, and sustainable stormwater system
that is integrated into the landscape, supports envisioned growth,
protects residents, and nurtures the environment.
Data Collection and Review
Unique Stormwater, Drainage Conditions and
Considerations in PT
•No “streams”
•Low Rainfall
•Historic Platting
Stormwater Management Needs
•Last plan adopted in 1980s
•Drainage system assessment
•Updated instructions for developers and builders
•Capital Projects
•Road drainage improvements
Tiering Map Legend
•Tier 1 –B LUE –Water Bodies and Receiving Waters
•Tier 2 –GREEN –Critical Drainage Corridors
•Tier 3 – PINK –Created Drainage Connections
•Tier 4 –PURPLE –Roadways
Updated Instructions for Developers
•New materials will be provided to direct applicants
•Propose to keep the same Ecology Manual in use
•2005 Department of Ecology’s Stormwater Management Manual for Western
Washington (ECY SWMM) and the 2012 ECY SWMM comparison
Capital Improvement Projects and Funding
Assessment of Stormwater System
Discovery Road –Road side Swale F Street –Curb and Gutter
Assessment of Stormwater System
Deficiencies and Needs
Landes Street Hastings Avenue
Assessment of Stormwater System
Deficiencies and Needs
Sheridan Street 14th Street
Assessment of Stormwater System
Deficiencies and Needs
P Street 3rd Street & Rosecrans Street
Assessment of Stormwater System
Deficiencies and Needs
Sheridan Street Hancock Street & 31st Street
Assessment of Stormwater System
Deficiencies and Needs
Haines Street49thStreet & Landes Street
Next Steps
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PORT TOWNSEND COUNCIL AD HOC COMMITTEE ON&NBSP; THE STORMWATER
MANAGEMENT PLAN AGENDA CITY HALL COUNCIL CHAMBERS, 540 WATER STREET
Business Meeting 01:18 p.m.January 10, 2018
I. Call to Order
II.Election of Chair
III.Overview of the City’s Current Stormwater System
Critical drainage corridor language and codes
Parametrix Memo 120717
Stormwater Manual Comparison 2005-2012
Stormwater Manual Comparison 2012-2014
Protected Drainage Infrastructure
Stormwater Acronyms Flipchart
V.Overview of the Proposed Tiering Map Concept
Tiering 2018-01-09
Catchment Areas
Shaded-Relief 2018-01-09
Storm Utility San Juan and F 2018-01-09
Stormwater CIP & Problem Areas
Tiering Flipchart Map
Tiering Explanation Flipchart
Regional Conveyance and Treatment Projects
VII. Public Comment (agenda items only)
VI.Proposed Stormwater Policies
PTMC 19.05 Critical Areas
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IV.Proposed Capital Projects
1999 SWMP Acquisitions and Stormwater Projects
2018-2023 Stormwater CIP List
VIII.Set agenda for next meeting
IX. Adjourn
Americans with Disabilities Act In compliance with the Americans with Disabilities Act, those requiring accommodation for this meeting should
notify the City Clerks Office at least 24 hours prior to the meeting at (360) 379-5083.
Hearing Assistance
Available
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CITY OF PORT TOWNSEND
MINUTES OF THE COUNCIL AD HOC COMMITTEE ON THE STORMWATER
MANAGEMENT PLAN OF JANUARY 10, 2018
CALL TO ORDER
The Council Ad Hoc Committee for the Stormwater Management Plan met in regular session
on Wednesday, January 10, 2018 at 1:32 p.m. in City Hall Council Chambers. The meeting
was called to order by the City Clerk Joanna Sanders. Members present at roll call were Ariel
Speser, Pamela Adams and Robert Gray.
Staff members present were: Assistant City Engineer Samantha Harper, City Engineer David
Peterson, Paul Fendt of Parametrix, Senior Planner/Planning Manager Judy Surber, City Clerk
Joanna Sanders.
ELECTION OF CHAIR
Ariel Speser was nominated and appointed Chair by unanimous vote.
OVERVIEW OF THE CITY'S CURRENT STORMWATER SYSTEM
Paul Fendt of Parametrix pointed out uniqueness of Port Townsend reviewing the Shaded-
Relief map for runoff consistent with topography. He explained geology and topography of
Port Townsend and the lack of streams. Samantha Harper reviewed catchment area map
showing stormwater discharge to wetlands as a result of topography. Staff reviewed the Storm
Utility Map of F Street and San Juan showing critical drainage corridors. Some discussion
ensued with staff explaining the current stormwater catch basins and pipes. Paul Fendt then
drew a map showing a cross-section of the road to explain water flow. He pointed out the
focus should be on the network of water flows. When asked about pervious and impervious
surfaces, Mr. Fendt provided an explanation of surface water, ground water and deep
groundwater.
OVERVIEW OF THE PROPOSED TIERING MAP CONCEPT
Showing the Stormwater CIP and Problem Areas map and tiering map, Mr. Fendt explained
the tiering system: Tier 1 Public Waters (Blue), Tier 2 Critical Drainage Corridors (Green), Tier
3 Connection BTW Built and Natural Protected Drainage Infrastructure (Pinks), and through
Tier 4 Public Roadways (Purple). There was additional discussion about areas that do and do
not drain well and where additional drainage systems might be needed.
Referring to the earlier draft of the draft tiering map, Mr. Fendt reviewed critical drainage areas
to be addressed in the plan. He noted that the map would be changing to improve what is
reflected.
PUBLIC COMMENT (AGENDA ITEMS ONLY)
PROPOSED STORMWATER POLICIES
Ms. Surber reviewed Chapter 19.05 of the Port Townsend Municipal Code and how the City
addresses development in critical drainage corridors. Staff also responded to questions about
development scenarios in critical areas. Mr. Fendt reviewed the proposed policy language
provided. Staff is ultimately looking for policy direction to recommend to Council before a
proposal is presented.
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At 3:05 p.m., the meeting recessed for the purposes of a break.
At 3:10 p.m., the meeting resumed.
PROPOSED CAPITAL PROJECTS
Mr. Fendt and Ms. Harper reviewed the list of capital projects in order to receive guidance on
priorities. The Committee was asked to review the list of capital projects and plan to provide
input at the next meeting. In reviewing the purple areas on the tiering map, Mr. Fendt
explained different approaches to funding these capital needs for improving drainage. When
asked what the City's responsibility is for these improvements, Mr. Fendt said it is a policy
direction with the question being how far to go to address water quality coming from the
roadways. Committee guidance would help staff and the consultant develop a specific
stormwater management program. If development involves a new road, then the City is
mandated to address storm water under the State's Stormwater Manual. If retrofitting an
existing roadway, the City is not mandated to address stormwater runoff. Staff was also asked
how this planning process would fit with the rate study. Staff explained that cost of
improvements would be part of the stormwater management plan, while how to fund those
improvements and the options would be a separate discussion.
SET AGENDA FOR NEXT MEETING
The date of the next meeting was set for January 24 at 1:30 p.m. No agenda was discussed.
ADJOURN
There being no further business, the meeting adjourned at 3:35.
Attest:
Joanna Sanders, MMC
City Clerk
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PORT TOWNSEND CITY COUNCIL AD HOC COMMITTEE ON THE STORMWATER
MANAGEMENT PLAN AGENDA CITY HALL COUNCIL CHAMBERS, 540 WATER STREET
Business Meeting 10:00 a.m.February 14, 2018
I. Call to Order
II.Approval of Minutes – January 24, 2018
012418
III.Stormwater Management Plan Policies
a. Stormwater Funding and System Needs
Tier 4 Edge Inventory 2018-02-08
Stormwater Funding 2018
Road Inventory 012318
180214 CC Adhoc Meeting Presentation
2017 Operating Stormwater Budget
IV.Public Comment (agenda items only)
V.Set agenda for next meeting (Tentative dates: Feb. 21 or 28)
VI. Adjourn
Americans with Disabilities Act In compliance with the Americans with Disabilities Act, those requiring accommodation for this meeting should
notify the City Clerks Office at least 24 hours prior to the meeting at (360) 379-5083.
Hearing Assistance
Available
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CITY OF PORT TOWNSEND
MINUTES OF THE COUNCIL AD HOC COMMITTEE ON THE STORMWATER
MANAGEMENT PLAN OF JANUARY 24, 2018
CALL TO ORDER
The Council Ad Hoc Committee for the Stormwater Management Plan met in regular session
on Wednesday, January 24, 2018 at 1:32 p.m. in City Hall Council Chambers. Chair Ariel
Speser called the meeting to order at 1:32 p.m. The other member present was Robert
Gray. Pamela Adams was excused.
Staff members present were: Assistant City Engineer Samantha Harper, City Engineer David
Peterson, Paul Fendt of Parametrix, Senior Planner/Planning Manager Judy Surber, and City
Clerk Joanna Sanders.
APPROVAL OF MINUTES - JANUARY 10, 2018
There was unanimous approval of the January 10 minutes as written.
STORMWATER MANAGEMENT PLAN POLICIES
Critical Drainage Corridors
Paul Fendt explained the Critical Drainage Corridor Map as provided. A goal of the plan is to
update the critical drainage areas. He noted the map was updated by him and edited by City
staff. On the map, areas in green reflect critical drainage areas; blue receiving water, which
includes wetlands and storm ponds; and yellow indicates the critical drainage corridors as
they exist today. There was some discussion about how staff uses these yellow areas. Staff
explained that the mapping is a trigger to the applicant and requires further evaluation.
Mr. Fendt explained the City is defining these critical drainage corridors and their
significance as part of the drainage system/network. If a critical drainage corridor
determination is made, then those areas would be identified, protected, and require closer
review when a development is proposed. He explained how those functions and values are
reviewed. Part of the planning process includes drafting language for how these areas
would be protected. He stressed that this means identifying areas so all staff and
landowners are aware and then putting standards in place to protect the areas.
There was some discussion of critical drainage corridors. Mr. Fendt referred to the tiering
map to further clarify. Staff reiterated that the current mapping is only an indicator and a field
investigation would be conducted to determine if a critical drainage corridor is present. The
amount of buffering is largely dependent on the proposed level of development.
Potential Water Quality Retrofit Projects
Mr. Fendt explained Ecology regulations. Phase II regulations are for populations above
10,000 and they issue Mitigated Permit Determination of Significance (MPDS) permits. The
City does not yet meet that threshold and at this point, the City can decide whether it wants
to begin a proactive program to prioritize areas in need of drainage improvements
and create a reserve fund for retrofitting roads, etc. It can decide whether there are
certain areas of intensive development where it wants to manage stormwater and add rain
gardens as an example. Creating a priority project list might help City apply for grant funds.
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Mr. Fendt then referred to the Road Inventory handout and explained the color coding and
cost estimates summarized on page 4. When thinking about areas needing retrofitting, he
showed examples of roadway treatment alternatives. The sewer rate study could address
funding priorities and a fund created for drainage repair on purple roads (referring to color
tiering map). These color segments will eventually get applied to the map and could then
depict priority projects on which to focus as funding becomes available.
Plan for the “Brown†RoadÂ
Mr. Fendt referred to drawings to explain funding alternatives for capital projects, arterial
collectors (purple roads), and side streets and neighborhood streets (brown roads). There
was discussion of existing requirements for stormwater.
Additional Unlisted Capital Improvement Projects
Referring to the Capital Improvement projects list, Staff inquired if the committee had
other additions. Some discussion ensued about 31st Street, which staff indicated would be
one project listed in brown. Mr. Fendt urged distinguishing between public and private
drainage problems. Staff also pointed out that new development guidelines are currently
available.
2005 and 2012 Department of Ecology Stormwater Management Manual for Western
Washington
Ms. Speser summarized her understanding of these manuals and Staff's recommendation
to use the 2005 manual. Staff concurred and noted that by using the 2005 manual, the City
can still implement elements of the 2012 manual such as low impact design. Working with a
consultant can help the City consider local geography and soils along with best available
science for the specific conditions that exist.
Public Process
Ms. Harper reviewed public comment received to date. Public comment would be
summarized at the public hearing before City Council. Responding to public comment about
the Kah Tai drainage corridor, staff said they do not believe there would be any plan to put
pipe in the intermittent and free flowing ravines or disturb them.
PUBLIC COMMENT (AGENDA ITEMS ONLY)
Ron Sikes spoke about Kah Tai Creek as a critical drainage corridor.
Debbie Jahnke spoke about citizen comments provided so far. She asked to review all
functions not just stormwater functions and urged creating policy related to vegetation and
habitat.
Julie Jaman spoke about public landscaping to help with functioning stormwater systems.
SET AGENDA FOR NEXT MEETING
Next meeting topics: Additional committee feedback and discussion, including criteria for
drainage. Begin to work on code language and more discussion of Tier 3 areas. The tentative
date for the next meeting was February 14 from 10-12 or 1:30 as an alternative.
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ADJOURN
There being no further business, the meeting adjourned at 3:31 p.m.
Attest:
Joanna Sanders, MMC
City Clerk
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PORT TOWNSEND COUNCIL AD HOC COMMITTEE ON&NBSP; THE STORMWATER
MANAGEMENT PLAN AGENDA CITY HALL COUNCIL CHAMBERS, 540 WATER STREET
Business Meeting 01:33 p.m.January 24, 2018
I. Call to Order
II.Approval of Minutes - January 10, 2018
011018
III.Stormwater Management Plan Policies
A.Critical Drainage Corridors
Site Drainage
Draft-Critical-Drainage-Areas-2018-1-24-Workshop
Additional Handout - Stormwater System Cross Section Enlarged
Additional Handout - Stormwater System Cross Section
Additional Handout - Copy of Road Inventory 012318
B.Potential Water Quality Retrofit Projects
C.Plan for the “Brown†RoadÂ
D.Additional Unlisted Capital Improvement Projects
Draft CIP List
E.2005 and 2012 Department of Ecology Stormwater Management Manual for Western
Washington
Parametrix Stormwater Manual Comparison Memo
2005-2012 Stormwater Manual Comparison
2012-2014 Stormwater Manual Comparison
F.Public Process
IV.Public Comment (agenda items only)
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V. Set agenda for next meeting
VI. Adjourn
Americans with Disabilities Act In compliance with the Americans with Disabilities Act, those requiring accommodation for this meeting should
notify the City Clerks Office at least 24 hours prior to the meeting at (360) 379-5083.
Hearing Assistance
Available
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CITY OF PORT TOWNSEND
MINUTES OF THE COUNCIL AD HOC COMMITTEE ON THE STORMWATER
MANAGEMENT PLAN OF JANUARY 24, 2018
CALL TO ORDER
The Council Ad Hoc Committee for the Stormwater Management Plan met in regular session
on Wednesday, January 24, 2018 at 1:32 p.m. in City Hall Council Chambers. Chair Ariel
Speser called the meeting to order at 1:32 p.m. The other member present was Robert
Gray. Pamela Adams was excused.
Staff members present were: Assistant City Engineer Samantha Harper, City Engineer David
Peterson, Paul Fendt of Parametrix, Senior Planner/Planning Manager Judy Surber, and City
Clerk Joanna Sanders.
APPROVAL OF MINUTES - JANUARY 10, 2018
There was unanimous approval of the January 10 minutes as written.
STORMWATER MANAGEMENT PLAN POLICIES
Critical Drainage Corridors
Paul Fendt explained the Critical Drainage Corridor Map as provided. A goal of the plan is to
update the critical drainage areas. He noted the map was updated by him and edited by City
staff. On the map, areas in green reflect critical drainage areas; blue receiving water, which
includes wetlands and storm ponds; and yellow indicates the critical drainage corridors as
they exist today. There was some discussion about how staff uses these yellow areas. Staff
explained that the mapping is a trigger to the applicant and requires further evaluation.
Mr. Fendt explained the City is defining these critical drainage corridors and their
significance as part of the drainage system/network. If a critical drainage corridor
determination is made, then those areas would be identified, protected, and require closer
review when a development is proposed. He explained how those functions and values are
reviewed. Part of the planning process includes drafting language for how these areas
would be protected. He stressed that this means identifying areas so all staff and
landowners are aware and then putting standards in place to protect the areas.
There was some discussion of critical drainage corridors. Mr. Fendt referred to the tiering
map to further clarify. Staff reiterated that the current mapping is only an indicator and a field
investigation would be conducted to determine if a critical drainage corridor is present. The
amount of buffering is largely dependent on the proposed level of development.
Potential Water Quality Retrofit Projects
Mr. Fendt explained Ecology regulations. Phase II regulations are for populations above
10,000 and they issue Mitigated Permit Determination of Significance (MPDS) permits. The
City does not yet meet that threshold and at this point, the City can decide whether it wants
to begin a proactive program to prioritize areas in need of drainage improvements
and create a reserve fund for retrofitting roads, etc. It can decide whether there are
certain areas of intensive development where it wants to manage stormwater and add rain
gardens as an example. Creating a priority project list might help City apply for grant funds.
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Mr. Fendt then referred to the Road Inventory handout and explained the color coding and
cost estimates summarized on page 4. When thinking about areas needing retrofitting, he
showed examples of roadway treatment alternatives. The sewer rate study could address
funding priorities and a fund created for drainage repair on purple roads (referring to color
tiering map). These color segments will eventually get applied to the map and could then
depict priority projects on which to focus as funding becomes available.
Plan for the “Brown†RoadÂ
Mr. Fendt referred to drawings to explain funding alternatives for capital projects, arterial
collectors (purple roads), and side streets and neighborhood streets (brown roads). There
was discussion of existing requirements for stormwater.
Additional Unlisted Capital Improvement Projects
Referring to the Capital Improvement projects list, Staff inquired if the committee had
other additions. Some discussion ensued about 31st Street, which staff indicated would be
one project listed in brown. Mr. Fendt urged distinguishing between public and private
drainage problems. Staff also pointed out that new development guidelines are currently
available.
2005 and 2012 Department of Ecology Stormwater Management Manual for Western
Washington
Ms. Speser summarized her understanding of these manuals and Staff's recommendation
to use the 2005 manual. Staff concurred and noted that by using the 2005 manual, the City
can still implement elements of the 2012 manual such as low impact design. Working with a
consultant can help the City consider local geography and soils along with best available
science for the specific conditions that exist.
Public Process
Ms. Harper reviewed public comment received to date. Public comment would be
summarized at the public hearing before City Council. Responding to public comment about
the Kah Tai drainage corridor, staff said they do not believe there would be any plan to put
pipe in the intermittent and free flowing ravines or disturb them.
PUBLIC COMMENT (AGENDA ITEMS ONLY)
Ron Sikes spoke about Kah Tai Creek as a critical drainage corridor.
Debbie Jahnke spoke about citizen comments provided so far. She asked to review all
functions not just stormwater functions and urged creating policy related to vegetation and
habitat.
Julie Jaman spoke about public landscaping to help with functioning stormwater systems.
SET AGENDA FOR NEXT MEETING
Next meeting topics: Additional committee feedback and discussion, including criteria for
drainage. Begin to work on code language and more discussion of Tier 3 areas. The tentative
date for the next meeting was February 14 from 10-12 or 1:30 as an alternative.
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ADJOURN
There being no further business, the meeting adjourned at 3:31 p.m.
Attest:
Joanna Sanders, MMC
City Clerk
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PORT TOWNSEND COUNCIL AD HOC COMMITTEE ON&NBSP; THE STORMWATER
MANAGEMENT PLAN AGENDA CITY HALL COUNCIL CHAMBERS, 540 WATER STREET
Business Meeting 01:32 p.m.February 28, 2018
I.Call to Order
II.Approval of Minutes – February 14, 2018
021418 Draft Minutes
III.Stormwater Management Plan Policies
A.Stormwater Development Regulations
Critical drainage corridor language and codes DRAFT
Guide Site Drainage DRAFT
Tier 4 Edge Inventory 2018-02-08
B.Critical Drainage Corridors
IV. Public Comment (agenda items only)
V. Set agenda for next meeting
VI. Adjourn
Americans with Disabilities Act In compliance with the Americans with Disabilities Act, those requiring accommodation for this meeting should
notify the City Clerks Office at least 24 hours prior to the meeting at (360) 379-5083.
Hearing Assistance
Available
Stormwater Management Plan
March 22, 2018
Page | 1
Memo
TO: Planning Commission
FROM: Samantha Harper, Assistant City Engineer
DATE: March 16, 2018 MEETING DATE: March 22, 2018
RE: Stormwater Management Plan & Critical Drainage Corridors
Background: The City is drafting a Stormwater Management Plan - a functional plan which addresses
existing stormwater system conditions; the operation and maintenance of existing facilities and capacity
for adding new facilities; identifying capital project needs; and potential funding methods for financing
of capital and operational costs. Stormwater management is about drainage and flooding, as well as
water quality. The City has a range of soil types from hard pan to sandy soils which impact stormwater
solutions. The City intends to plan for surface water management as a whole – integrating a
preservation of water resources through natural systems approach where possible while protecting
environmental values and public health. The process will include comparison of 2005 and 2012 DOE
Stormwater Manual and recommended concurrent amendments to the City’s development
regulations/Engineering Design Standards to ensure public and private projects achieve the City’s
adopted level of service standard.
In addition to the functional plan, staff is assessing the need for updates to PTMC Chapter 13.32
Stormwater Management Requirements.
On November 9, 2017, Planning Commission received a briefing including a proposed tiered map
identifying key areas of the City's stormwater system. Commissioners discussed issues related to
the Plan including addressing climate change and development costs and fees. Packets are
available via the City website at: http://cityofpt.us/video.html
In January and February of 2018, staff worked with the Council Sub-Committee.
A draft plan is anticipated in April 2018.
Relationship to Other Plans: The City is in the process of updating the Critical Areas Ordinance.
Planning Commission has expressed concern that the Stormwater Management Plan may compromise
existing protections to Critical Drainage Corridor (CDC) standards and stormwater regulations/design
standards. On February 22, 2018 Development Services staff provided a Draft Outline of March 22
Stormwater Consistency discussion (Attachment D to the 2/22/18 packet) as a framework for review of
existing vs. proposed stormwater implementation. The outline includes Comprehensive Plan Goals and
Stormwater Management Plan
March 22, 2018
Page | 2
Policies related to stormwater management and critical drainage corridors. Commissioners provided
the following feedback:
1) Add Land Use Policies 7.1 - 7.4 to Attachment D.
2) Provide the following additional information for the March 22 packet:
A. Draft of the Stormwater Management Plan – whole document if possible, key
chapters at a minimum
B. Map: Critical Drainage Corridors
C. Map: Stormwater tiering
D. Consultant’s memo assessing 2005 SWMM vs. 2014 version
E. Draft regulatory language for the CDC - and where will this be codified?
F. If codified in Chapter 13 – will it come to the PC for review and recommendation?
March 22: The March 22 meeting will focus on items A-D above and the completed Outline of March
22 Stormwater Consistency discussion (Attachment *). Draft regulatory language for CDCs is still
pending, however, staff has provided a Summary of the Proposed Changes (Attachment *) for
discussion. Draft chapters from the Stormwater Management Plan are not being provide, however,
staff has provided a matrix of how the Stormwater Management Plan will be consistent with the
Comprehensive Plan.
Recommendation: No action is required of the Planning Commission at this time. Staff seeks questions
and feedback in preparation of the upcoming public hearings.
Next Steps:
** Special Meeting – CDC Draft Language?
April 12, 2018 Critical Areas Update – Public Hearing
May 10, 2018 Stormwater Management Plan Concurrency review - Public Hearing
Attachments
Attachment A – Open Space, Critical Areas and Stormwater Tiering Map
Attachment B - Open Space, Critical Areas without Potential Drainage Ways and Stormwater Tiering
Map
Attachment C – PTMC 19.05.090 Summary of Amendments for Critical Area 3 – Frequently Flooded
Areas and Critical Drainage Corridors
Attachment D – Summary of Consistency Review between the Stormwater Management Plan and the
Comprehensive Plan
Attachment E – Department of Ecology Stormwater Management Manual Technical Memo Comparison
Attachment F – Department of Ecology’s Summary Table of what changed from the 2005 to the 2012
Stormwater Management manual
Attachment G- Department of Ecology’s Summary Table of what changed from the 2012 to the 2014
update of the Stormwater Management manual
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21st St.
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22nd St.
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30th St.
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6th St.
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40th St.
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Tier 2 - Critical Drainage Areas
Tier 3 - Created Drainage Connections
Main Roads
Other Roads
Tier 4 - Road Drainage
DRAFT
POS (A): Potential Park or Open Space
Quimper Wildlife Corridor
FEMA Preliminary Flood Insurance (AE)
March 15, 2018
Slopes > 40%
Potential Drainage Ways
Wilson
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24th St.
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35th St.
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22nd St.
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.
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H St.
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J St.
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a
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S
t
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32nd St.
PearyAve.
Sh
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a
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S
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Elm
S
t
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58th St.
B St.
Morton St.
Be
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S
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35th St.
Sh
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m
a
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S
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Florence St.
Carrol St.
Jefferso
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S
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Umatilla Ave.
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S
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3rd St.
15th St.
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a
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13th St.
12th St.
25th St.
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45th St.
Ro
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r
a
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S
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Ha
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32nd St.
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51st St.
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30th St.
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23rd St.
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6
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53rd St.
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S
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3rd St.
Th
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S
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Sh
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S
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Denison St.
7th St.
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15th St.
K St.
Hig h l andL
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Rooseve
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S
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Taft St.
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Lp.
J
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28th St.
O St.
Gi
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S
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35th St.
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i
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S
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Will
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S
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Cli
f
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S
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E St.
G St.
Ed
d
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S
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T St.
Will
o
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Be
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S
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Rainshadow Rd.
29th St.
Cl
i
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S
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38th St.
37th St.
21st St.
La
k
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S
t
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37th St.
32nd St.
15th St.
Sp
r
i
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S
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31st St.
Hi
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S
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38th St.
36th St.
Ho
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35th St.
Th
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S
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9th St.
Ja
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S
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E.
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6th St.
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.
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Reynolds Rd.
5th St.
Gib
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Cl
i
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.
33rd St.
FortWorden
W
ay
8th St.
Milo St.
Tremont St.
Cedar St.
Cl
e
v
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l
a
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d
S
t
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27th St.
Pershing Ave.
V St.
Center St.
H
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s
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S
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Er
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S
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Q
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Alexander's Lp.
R St.
Ro
s
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S
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Reed St
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Seton Rd.
Ed
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S
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20th St.
T St.
Foster S
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.
M
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M St.
L St.
Cl
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Mc
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S
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44th St.
Coro
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A
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45th St.
Fl
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go
Rd.
Iv
y
S
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Th
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S
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22nd St.
He
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S
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N St.
36th St.
Q
u
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S
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V St.
As
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S
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Ot
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S
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Lincoln
S
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Garfield
S
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Lincoln
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S
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Winona St.
Cosgrov
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CherrySt.
Wa
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S
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11th St.
27thSt.
Mc
C
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On
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o
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S
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Towne Po i nt Ave.
Ra
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S
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57th St.
Ed
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S
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Holcomb
St.
M
a
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s
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S
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.
Mo
s
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S
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Market St.
34th St.
Root St.
P St.
Linden St.
Ja
c
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s
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S
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G
a
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S
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3rd St.
49thSt.
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Sp
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7th St.
K
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a
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S
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.
21st St.
Seaview Dr
.
Jensen St.
22nd St.
W
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S
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Ku
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S
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Ro
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S
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32nd St.
31st St.31st St.
25th St.
Ho
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Al
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23rd St.
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S
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Pi
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S
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Wil
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9th St.
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8
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1st St.
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Spring St.
42nd St.
Ku
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S
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Thomas
St.
30th St.
WoodlandAve.
25th St.
6th St.
Hastings Ave.
H
a
r
r
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s
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S
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.
C
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30th St.
Hi
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El
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52nd St.
Ot
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Lenore St.
Victoria
A
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.
M
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S
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40th St.
49th St.
56th St.
50th St.
55th St.
51st St.
54th St.
Ma
s
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S
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.
Q
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S
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San
Juan
Ave.
T
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S
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.
33rd St.
41st St.
43rd St.
T
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S
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.
Alwood St.
W St.
13th St.
Gi
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S
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.
Gr
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.
La
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U St.
18th St.
Cook
A
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.
Hi
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S
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19th St.
29th St.
Cl
e
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S
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.
10th St.
Fir
S
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.
S St.
F St.
UmatillaAve.
N.
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a
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.
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16th St.
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Fredericks St.
Jefferso
n
S
t
.
20th St.
S.
Jacob
Miller
Rd
.
Sa
n
Juan
Av
e.
Water St
.
HarborDefenseWay
Clay St.
Sh
e
r
i
d
a
n
S
t
.
14th St.
Ho
wa
rd
St.
Lawrenc
e
S
t
.
Franklin
S
t
.
Washing
t
o
n
S
t
.
39th St.
S i m s W a y
Storm Pond
Possible Wetland
Tier 1 - Natural Drainage and Water Bodies
Wetland
100 Year Flood
Critical Drainage Area
Tier 2 - Critical Drainage Areas
Tier 3 - Created Drainage Connections
Main Roads
Other Roads
Tier 4 - Road Drainage
DRAFT
POS (A): Potential Park or Open Space
Quimper Wildlife Corridor
FEMA Preliminary Flood Insurance (AE)
March 15, 2018
Slopes > 40%
Summary of Proposed Amendments to PTMC Title 19.05.090 Critical Areas 3- Frequently Flooded Areas and Critical Drainage Corridors
1 | P a g e
SUMMARY OF PROPOSED AMENDMENTS TO PTMC TITLE 19.05.090 CRITICAL AREA 3 – FREQUENTLY FLOODED AREAS AND CRITICAL
DRAINAGE CORRIDORS
Amended Sections Summary of Revision Notes
19.05.020 Definitions. “Critical drainage corridors” or “area”
Remove characteristic 3 in its entirety:
“Watercourses which exhibit the above
characteristics and have been
channelized or piped;”
This characteristic is redundant.
19.05.090 Critical Area 3 – Frequently
Flooded Areas and Critical Drainage
Corridors.
A. Purpose Staff Recommends: Separate the
purpose for frequently flooded areas and
critical drainage corridors as they are
regulated differently, frequently flooded
areas are regulated by federal and state
law and critical drainage corridors are
regulated by local regulations.
B.2. Classification.
Remove “from local knowledge about
regular flooding occurrence in certain
areas or the potential for flooding if
existing drainage is modified.”
Staff Recommends: Existing language is
vague. Classification should be limited to
available flood data (i.e., FEMA maps and
the Polaris study for Drainage Basin 4). ,
Flood occurrences related to drainage will
be addressed in the Stormwater
Management Plan.
C.2. Regulated Development.
Add the required distance from the
centerline of the CDC.
Staff Recommends: It is confusing to
have the width of the CDC under E.
Buffers and Setbacks. The width of the
CDC should be specified in the Regulated
Development Section.
D. Performance Standards for
Development.
Add a performance standard to allow for
drainage corridors to be crossed
Staff Recommends: There are cases
where there is a need to cross a critical
drainage corridor with roads, trails, and
utilities. This would still meet the
Summary of Proposed Amendments to PTMC Title 19.05.090 Critical Areas 3- Frequently Flooded Areas and Critical Drainage Corridors
2 | P a g e
requirement of not filling in the CDC, but
allows a little flexibility if there is
development around a CDC.
E. Buffers and Setbacks.
Remove language in its entirety and
replace with the following. There are no
buffers or setback from CDCs.
Staff Recommends: Refer to Staff
Recommends comments in C.2.
Regulated Development.
G. Special Reports.
Add a sentence about who should design
the utility crossing if one is proposed?
Specify type of backfill?
Under review: Staff would like to
continue to review criteria if a CDC is
crossed.
G Special Reports.
Clarify content of report.
Under review: Would that be done by an
engineer? Does that need hydraulic
modeling? It that just looking at the
upstream and downstream effects?
Summary of Stormwater Management Plan Consistency with the 2016 Comprehensive Plan Update 3/22/2018
1 | P a g e
This table addresses the City’s 2016 updated Comprehensive Plan Land Use Element and Utility Element Goals and Policies and
compares them to the proposed Stormwater Management Plan (Functional Plan).
Land Use Element Goal/Policy Existing Proposed Assessment1
Policy 7.1: Manage stormwater quantity in a way
that approximates the natural hydrologic
characteristics of the area while ensuring that all
stormwater receives adequate treatment before
discharge or infiltration. The quality of stormwater
discharged from stormwater treatment facilities,
such as ponds, drainage corridors, wetlands, salt
water, etc. should be as close to the water quality
present before human encroachments as possible.
· 2005 Ecology
Stormwater Manual for
Western Washington.
· Development proposals
must meet applicable
requirements of PTMC
13.32 and EDS Chapter 4
Stormwater.
· 2005 Ecology Stormwater
Manual for Western
Washington and related
guidance for stormwater
quality management.
· No change.
· New guidance materials
are being developed in
conjunction with the
stormwater management
plan (SWMP) to assist
home builders with site
stormwater design.
Improves consistency
The 2005 Manual uses and
allows all current stormwater
practices typically applied in the
region for municipal stormwater
control.
Policy 7.2: Ensure that public and private
development projects are reviewed and
conditioned in a manner consistent with the City's
Stormwater Management Plan and the
Department of Ecology’s Stormwater
Management Manual for Western Washington.
· 2005 Ecology
Stormwater Manual for
Western Washington.
· Development proposals
must meet applicable
requirements of PTMC
· 2005 Ecology Stormwater
Manual for Western
Washington and related
guidance for stormwater
quality management.
· No Change.
Improves consistency
The 2005 Manual uses and
allows for all current stormwater
practices typically applied in the
region for municipal stormwater
control.
1 Inconsistent, No change, Improves Consistency
Summary of Stormwater Management Plan Consistency with the 2016 Comprehensive Plan Update 3/22/2018
2 | P a g e
Land Use Element Goal/Policy Existing Proposed Assessment1
7.2.1: Continue to implement the
Department of Ecology’s Stormwater
Management Manual for Western
Washington as a guide for reviewing
developments and requiring the use of best
management practices for land clearing,
runoff affecting water quality, erosion, and
sedimentation.
13.32 and EDS Chapter 4
Stormwater
· New guidance materials are
being developed in
conjunction with the
stormwater management
plan (SWMP) to assist home
builders with site
stormwater design.
Policy 7.3: Pursue strategies intended to reduce
stormwater runoff to levels not likely to cause
flooding, significant erosion to natural drainage
ways, or significant degradation of water quality.
2005 Ecology Stormwater
Manual for Western
Washington.
2005 Ecology Stormwater
Manual for Western
Washington and related
guidance for stormwater
quality management.
Improves Consistency
The Manual uses and allows for
all current stormwater practices
typically applied in the region for
municipal stormwater control.
Policy 7.4: Encourage the use of a natural
drainage systems approach to control stormwater
from new developments. Where feasible, new
developments should capitalize on natural drainage
features to hold and treat stormwater and
pollutants before they are carried down slope or
before they enter wetlands or other bodies of
water.
· 2005 Ecology
Stormwater Manual for
Western Washington.
· PTMC 19.05 currently
calls for the protection
of critical drainage
corridors (CDC), which
are natural drainage
paths in the landscape.
· 2005 Ecology Stormwater
Manual for Western
Washington and related
guidance for stormwater
quality management.
· CDCs are proposed to be
recategorized and updated
in conjunction with the
SWMP.
Improves consistency
The Manual uses and allows for
all current stormwater practices
typically applied in the region for
municipal stormwater control,
which include low impact
development (LID) techniques.
Summary of Stormwater Management Plan Consistency with the 2016 Comprehensive Plan Update 3/22/2018
3 | P a g e
Land Use Element Goal/Policy Existing Proposed Assessment1
Goal 14: Protect and manage stormwater quality
through the use of current design practices and
standards to minimize the impacts of land use
development and stormwater runoff on natural
systems, fish and wildlife habitat, and public
health.
2005 Ecology Stormwater
Manual for Western
Washington.
2005 Ecology Stormwater
Manual for Western
Washington and related
guidance for stormwater
quality management.
Improves Consistency
The 2005 Manual uses and
allows for all current stormwater
practices typically applied in the
region for municipal stormwater
control.
Policy 14.1: Review each public and private
development project to ensure conformance with
the standards of the City's Stormwater
Management Plan, Engineering Design Standards,
and the Department of Ecology's Stormwater
Management Manual for Western Washington to
ensure that discharges of stormwater into ponds,
drainage corridors, wetlands, groundwater, salt
water, and other water bodies, do not result in a
degradation of water quality.
· The City has adopted the
2005 Ecology
Stormwater Manual for
Western Washington.
· The City provides for
stormwater review of
applicable design
proposals through Port
Townsend Municipal
code (PTMC) 13.32
Stormwater
Management
Requirements and
Engineering Design
Standards (EDS) Chapter
4 Stormwater
· 2005 Ecology Stormwater
Manual for Western
Washington and related
guidance for stormwater
quality management.
· No Change.
· New guidance materials
are being developed in
conjunction with the
stormwater management
plan (SWMP) to assist
home builders with site
stormwater design.
Improves consistency
The City has adopted the 2005
Ecology Stormwater Manual for
Western Washington. The
Manual uses and allows for all
current stormwater practices
typically applied in the region for
municipal stormwater control.
Policy 14.2: Regularly update the Engineering
Design Standards and the Stormwater
Management Plan to maintain up-to-date practices
and standards and to promote low impact
development (LID) techniques that combine
· 2005 Ecology
Stormwater Manual for
Western Washington.
· 2005 Ecology Stormwater
Manual for Western
Washington and related
guidance for stormwater
quality management.
Improves consistency
Summary of Stormwater Management Plan Consistency with the 2016 Comprehensive Plan Update 3/22/2018
4 | P a g e
Land Use Element Goal/Policy Existing Proposed Assessment1
engineering with the preservation of natural
systems.
· PTMC 19.05 currently
calls for the protection
of critical drainage
corridors (CDC), which
are natural drainage
paths in the landscape.
· CDCs are proposed to be
revised and updated in the
SWMP and they will
continue to be protected by
ordinance for stormwater
and conveyance functions,
including water quality,
flood control, and drainage.
Goal 15: Manage stormwater quantity in a way that
mimics nature (i.e., "natural drainage systems"
approach).
Policy 15.1: Preserve natural surface and
subsurface drainage systems to the maximum
extent possible.
· 2005 Ecology
Stormwater Manual for
Western Washington.
· 2005 Ecology Stormwater
Manual for Western
Washington and related
guidance for stormwater
quality management.
· New guidance materials are
being developed in
conjunction with the SWMP
to assist home builders with
site stormwater design.
Improves consistency
(Note: The Manual uses and
allows for all current stormwater
practices typically applied in the
region for municipal stormwater
control.) The City will continue
to encourage site development
design to minimize project
footprints and reserve natural
areas of the sites while
addressing the objective to meet
infill and redevelopment
objectives.
Policy 15.2: Pursue strategies intended to reduce
stormwater runoff to levels not likely to cause
flooding, significant erosion to natural drainage
ways, or significant degradation of water quality.
· 2005 Ecology
Stormwater Manual for
Western Washington.
· 2005 Ecology Stormwater
Manual for Western
Washington and related
guidance for stormwater
quality management.
Improves consistency
(Note: The Manual uses and
allows for all current stormwater
practices typically applied in the
region for municipal stormwater
control). The City will continue
Summary of Stormwater Management Plan Consistency with the 2016 Comprehensive Plan Update 3/22/2018
5 | P a g e
Land Use Element Goal/Policy Existing Proposed Assessment1
· New guidance materials
are being developed in
conjunction with the
SWMP to assist home
builders with reducing site
runoff to the maximum
extent practicable.
to encourage site development
design to minimize project
footprints and reserve natural
areas of the sites. Commercial
and subdivision sites will
continue to be required to
control stormwater to pre-
settlement levels.
Policy 15.3: Ensure that stormwater quantity from
new development does not exceed natural historic
flows, unless regional facilities are in place that can
accommodate the increased flows without
detrimental impacts to other properties.
· 2005 Ecology
Stormwater Manual for
Western Washington.
The Manual uses and
allows for all current
stormwater practices
typically applied in the
region for municipal
stormwater control,
including flow control to
natural historic flow
rates. Regional facilities
have been designed and
constructed in selected
locations and are
available for use.
· 2005 Ecology Stormwater
Manual for Western
Washington and related
guidance for stormwater
quality management.
· New guidance materials are
being developed in
conjunction with the SWMP
to assist home builders with
reducing site runoff to the
maximum extent
practicable.
Improves Consistency
Commercial and subdivision sites
will continue to be required to
control stormwater to natural
historic levels.
Policy 15.4: Protect wetlands and other
environmentally sensitive areas from flooding and
increased runoff from new development and land
clearing activities.
· 2005 Ecology
Stormwater Manual for
Western Washington.
The Manual uses and
allows for all current
stormwater practices
typically applied in the
region for municipal
stormwater control.
· 2005 Ecology Stormwater
Manual for Western
Washington and related
guidance for stormwater
quality management.
· In addition, CDCs are
proposed to be
recategorized and updated
Improves consistency
Summary of Stormwater Management Plan Consistency with the 2016 Comprehensive Plan Update 3/22/2018
6 | P a g e
Land Use Element Goal/Policy Existing Proposed Assessment1
Specifically, Minimum
Requirements #8 and #6
of the Ecology Manual
are required to protect
wetlands.
in conjunction with the
SWMP.
Goal 16: Maintain stormwater facilities to ensure
their proper and intended function.
Policy 16.1: Inspect and maintain stormwater
facilities in accordance with the Best Management
Practices of the Department of Ecology Stormwater
Management Manual.
City-owned facilities are
reviewed regularly by staff
and routine maintenance is
performed.
No change. No change - The City is not
required by permit to conduct
these inspections as it is not a
Phase 2 National Pollutant
Discharge Elimination System
(NPDES) community
Policy 16.2: Ensure that private property owners
maintain stormwater facilities in accordance with
Best Management Practices.
The City does not review
private facilities.
No change. No change - The City is not
required by permit to conduct
these inspections as it is not a
Phase 2 National Pollutant
Discharge Elimination System
(NPDES) community
Policy 16.3: Allocate adequate resources to
maintain stormwater facilities and natural drainage
systems.
The City’s Stormwater Utility
Fund funds routine
maintenance of its facilities.
The City includes funds in its
stormwater program to provide
routine maintenance of its
facilities.
No change
Summary of Stormwater Management Plan Consistency with the 2016 Comprehensive Plan Update 3/22/2018
7 | P a g e
Land Use Element Goal/Policy Existing Proposed Assessment1
Goal 17: Provide financial resources to
appropriately operate the Stormwater Utility and
construct capital improvements.
Policy 17.1: Maintain stormwater utility rates at a
level appropriate to conduct necessary operations
and maintenance activities and capital
improvement projects.
The City’s Stormwater Fund
is funded through a monthly
base rate and capital
surcharge, these revenues
fund both operations and
capital projects.
The City is intending to review
and assess its rates in 2018.
Improves consistency
Policy 17.2: Establish fees and charges to recover
utility costs related to development and, where
feasible, allocate costs to user classes to reflect the
true cost to the utility.
Currently, the City does not
have a fee or user charge
system in place for new
development.
The City is intending to review
and assess its rates in 2018.
The SWMP is contemplating
connection approaches and
potential funding methods.
Improves consistency
Policy 17.3: Pursue a wide variety of funding
options, including low interest loans and state
grants.
The City has and will
continue to pursue
stormwater grants and
loans. Recently, the City is
applying to be listed on the
Puget Sound Near Term
Action list for stormwater
retrofitting of our existing
major roadways.
Completion of the SWMP can
improve the City’s position for
obtaining grants and loans.
Improves consistency
719 2ND AVENUE, SUITE 200 | SEATTLE, WA 98104 | P 206.394.3700
TECHNICAL MEMORANDUM
DATE: December 7, 2017
TO: Samantha Harper, P.E.
FROM: Julie Brandt, P.E.
SUBJECT: Stormwater Manual Comparison
CC: Paul Fendt, P.E.
PROJECT NUMBER: 553-2836-004 (01/04)
PROJECT NAME: Stormwater Management Plan
1. INTRODUCTION
Port Townsend is developing a comprehensive stormwater management plan to improve the operation of the
city’s existing system and anticipate future needs. Part of the stormwater management plan development
includes review and evaluation of the City’s current stormwater standards and manuals. This technical
memorandum compares the City’s current adopted stormwater guidance manual against subsequent revisions
implemented by the Washington State Department of Ecology (Ecology).
2. CURRENT CITY GUIDANCE MANUAL
The City adopted Ecology’s 2005 Stormwater Management Manual for Western Washington (2005 SWMMWW)
under Section 13.32.010.A of the Port Townsend Municipal Code (Stormwater Code). The Stormwater Code
directs developers to use the 2005 SWMMWW for all clearing and grading activities, for erosion control during
construction, and for permanent drainage system improvements; except that developments must comply with
the following City requirements, which supersede the 2005 SWMMWW:
1. Section 2.6 – Optional guidance relating to financial liability and off-site analysis and mitigation
2. Engineering Design Standards
3. Stormwater Master Plan, and
4. Adopted drainage basin plans
The major elements included in the 2005 SWMMWW (and year the change was made) are:
1. Flow Control and Water Quality Treatment (2001):
The thresholds for selection of Best Management Practices (BMPs) were expanded to require nearly all
projects to apply appropriate flow control and runoff treatment BMPs, including on-site stormwater
management techniques.
TECHNICAL MEMORANDUM (CONTINUED)
City of Port Townsend 553-2836-004 (01/04)
Stormwater Manual Comparison 2 December 7, 2017
2. Duration Standard and Continuous Modeling (2001):
The flow control requirements were increased to address both peak flows and duration of high flows, and
calling for the use of continuous runoff models when available.
3. Enhanced Treatment (2001):
Requirements were increased to result in higher levels of water quality treatment (enhanced treatment)
for discharges from most industrial, commercial, and multifamily sites and arterials and highways.
4. Western Washington (2005):
The geographic scope of the SWMMWW was expanded to apply previous requirements to all of Western
Washington rather than Puget Sound only.
3. ECOLOGY REVISIONS
Subsequent to the City adoption of the 2005 SWMMWW, Ecology has published updates to the manual in 2012
and 2104. The major elements included in those updates (and year the change was made) are listed below in
order of their relevance to Port Townsend. Summary tables published by Ecology that discuss all of the
SWMMWW changes from 2012 and 2014 are included in Attachment 1.
1. Minimum Requirement 8 – Wetland Protection (2012):
Most of Appendix I-D was rewritten to remove outdated information, clarify concepts, and update the
requirements for protecting wetlands through controlling stormwater runoff discharges. Requirements
were added dictating that total discharges to wetlands must not deviate by more than 20 percent on a
single event basis and must not deviate by more than 15 percent on a monthly basis.
2. Puget Sound Action Agenda Terminology (2012):
Outdated references and guidance related to the Puget Sound Water Quality Management Plan were
removed and replaced with guidance on the Puget Sound Action Agenda.
3. Additional Basin Planning Guidance
Appendix I-A was updated to clarify the guidance for altering the minimum requirements through basin
planning, and language was added to address retrofit needs and alternative flow control strategies.
4. LID Requirements:
· LID Performance Standard for Stream Protection (2012) – The new LID performance standard and
BMP list options were added. The LID standard is based on project size, location, and BMP feasibility
for projects that discharge to fresh waterbodies.
Direct discharges to marine waterbodies through man-made conveyance systems are exempt from the
LID standard as long as erosion and flooding are prevented.
· LID Definition Consistency (2012) – Definitions were revised for terms relevant to the new low impact
development (LID) guidance (hard surfaces, LID, converted vegetation) and requirements in the
Municipal Stormwater Permits.
· Hard Surface Threshold Changes (2012) – Thresholds and terminology were updated to determine
which minimum requirements apply to new development and redevelopment, such as the
replacement of “impervious” surfaces with “hard” surfaces, the application of minimum
requirements #6 -#9 to replaced hard surfaces at new development sites, the deletion of the word
"native" from the land conversion threshold.
TECHNICAL MEMORANDUM (CONTINUED)
City of Port Townsend 553-2836-004 (01/04)
Stormwater Manual Comparison 3 December 7, 2017
· Updated Stormwater Site Plan Contents (2012) - Additional guidance was added regarding LID site
design.
· Construction Stormwater Pollution Prevention (2012) – Construction stormwater management
requirements were updated to protect LID BMPs
· Universal LID Language Clarification (2014) – Typos, spelling corrections, and terminology
inconsistencies that resulted from the incorporation of the LID standard were address throughout the
manual.
· Updated WWHM Software Guidance (2014) – Wording was revised to reflect recent upgrades to the
Western Washington Hydrology Model (WWHM2012) to include LID simulation capabilities.
5. Historical Development Map (2012):
To show which basins potentially qualify for use of existing land cover as the target for flow control
purposes, a map was added depicting basins that have had 40 percent or more total impervious area
since 1985. These basins are mainly comprised of areas between Everett and Tacoma east of Puget Sound
and in the vicinity of Bremerton and Bainbridge Island.
6. NPDES Permit References (2012):
· Guidance was added to refer Phase I and Phase II Municipal Stormwater Permittees to Appendix 1 of
their respective general permits for more information on the requirements for their stormwater
program requirements.
· An overview was added regarding the requirements of the Industrial Stormwater General Permit and
their relationship to the BMPs in the manual.
· An overview was added regarding the requirements of the Construction Stormwater General Permit
and their relationship to the BMPs in the manual.
4. RECOMMENDATION
The Ecology Manual was written to be reasonably applicable to a majority of landscapes and development
scenarios found in western Washington. With the exception of the new wetland protection standard, the key
recent SWMMWW revisions published by Ecology are not well-applied to Port Townsend development types,
landscape, receiving water bodies, and precipitation regimes. The City is not now precluded from using the LID
techniques described in the 2012 Manual and it could be expected that they would be used when applicable and
feasible because they are often a preferred choice for circumstances where they would function in the landscape
(e.g. good soils that infiltrate at high rates). Therefore, it is recommended that the City consider adoption of the
updated wetland protection standard through the Municipal Code and continue use of the 2005 SWMMWW.
Location Approximate Page
Numbers
Change Tied
to Permit
Language
Change Reasoning or Comments
General
Inside cover page ES-i and ES-ii Added an Executive Summary Summarized the reasons for the update, the uses of the manual and
provided information on the public involvement process.
All Volumes Renumbered Tables and Figures
Renumbered all tables and figures in all Volumes. The new numbers
coordinate tables and figures to the section of the Volume where they
are located. (Eg. Figure 2.4.2 is the second figure in Section 2.4, Table
4.1.3 is the third table in Section 4.1).
Chapter 1 - Introduction 1-1 through 1-26 Update incorrect or outdated code
references.
Revised incorrect or outdated code references, such as the RCW and
WAC.
Chapter 1 - Introduction 1-1 through 1-26 Minor language changes.Revised for clarity and removed outdate language in Sections 1.2, 1.4,
1.5.1, 1.6.10.
Section 1.5.4 Flow Control BMPs 1-5 Minor language changes.Revised language for changes made in Appendix I-D Guidelines for
Wetlands when Managing Stormwater.
Section 1.5.5 On-site Stormwater Management
BMPs 1-6 Additional guidance provided.Language added to categorize On-site Stormwater Management BMPs,
including LID BMPs.
Section 1.6.4 The Puget Sound Action Agenda 1-11 through 1-13
Significant revisions to remove outdated
guidance and to add new guidance. Section
renamed.
Removed references and guidance related to the Puget Sound Water
Quality Management Plan and replaced with guidance on the Puget
Sound Action Agenda.
Section 1.6.5 Phase I - NPDES and State Waste
Discharge Stormwater Permits for Municipalities 1-13 through 1-14 Yes Additional guidance provided and outdated
guidance removed.
Added guidance referring Phase I Municipal Stormwater Permittees to
Appendix 1 of the permit for more information on the requirements for
their stormwater program requirements.
Section 1.6.6 Phase II - NPDES and State Waste
Discharge Stormwater Permits for Municipalities 1-14 Yes Additional guidance provided and outdated
guidance removed.
Added guidance referring Phase II Municipal Stormwater Permittees to
Appendix 1 of the permit for more information on the requirements for
their stormwater program requirements.
Section 1.6.7 Municipalities Not Subject to the
NPDES Stormwater Municipal Permits 1-14 Guidance removed.Removed outdated references to the Puget Sound Water Quality
Management Plan. Section renamed.
Section 1.6.8 Industrial Stormwater General Permit 1-14 through 1-15 Yes Revised to coordinate with the current
Industrial Stormwater General Permit
Revised to provide an overview of the requirements of the current
Industrial Stormwater General Permit and their relationship to the BMPs
in the manual.
Section 1.6.9 Construction Stormwater General
Permit 1-15 through 1-16 Yes Revised to coordinate with the current
Construction Stormwater General Permit
Revised to provide an overview of the requirements of the current
Construction Stormwater General Permit and their relationship to the
BMPs in the manual.
Section 1.6.15 Underground Injection Control
Authorizations 1-18 through 1-19 Significant revisions to add guidance.Added language to refer to Ecology's website and to define UIC well.
Chapter 2 - Minimum Requirements for New
Development and Redevelopment 2-1 through 2-46 Minor language changes.Revised for clarity and removed outdated language in the introduction
and in Sections 2.1, 2.2, 2.5.3, and 2.5.10.
Chapter 2 - Minimum Requirements for New
Development and Redevelopment 2-1 through 2-46 Yes Revised language.
Revised definitions, requirements, supplemental guidance, etc. to
correspond to the changes in the Municipal Stormwater Permits and for
new LID requirements.
Volume I Minimum Technical Requirements and Site Planning
Chapter 1 - Introduction
Chapter 2 - Minimum Requirements for New Development and Redevelopment
Location Approximate Page
Numbers
Change Tied
to Permit
Language
Change Reasoning or Comments
Section 2.1 Relationship to the Puget Sound Action
Agenda 2-2 Added guidance. Section renamed.
Removed outdated references to the Puget Sound Water Quality
Management Plan. Section renamed and focuses on relationship of the
manual to the municipal stormwater permits.
Section 2.3 Definitions Related to Minimum
Requirements 2-5 through 2-9 Yes Added and revised definitions.
Added definitions for a few terms used previously but not previously
defined. Other terms have a revised definition or a new definition (hard
surfaces, LID, converted vegetation) because of the new low impact
development (LID) guidance and requirements in the Municipal
Stormwater Permits.
Section 2.4 Applicability of the Minimum
Requirements 2-9 through 2-16 Yes
Revised the thresholds for determining
which minimum requirements apply to new
development and redevelopment. Revised
supplemental guidelines.
Changes include: the replacement of “impervious” surfaces with “hard”
surfaces, the application of minimum requirements #6 - #9 to replaced
hard surfaces at new development sites, the deletion of the word
"native" from the land conversion threshold.
Section 2.5.1 Minimum Requirement #1:
Preparation of Stormwater Site Plans 2-16 Yes Revised requirements and objective.
Added a new statement for the site plan to use site-appropriate
development principles to retain native vegetation and minimize
impervious surfaces to the extent feasible.
Section 2.5.2 Minimum Requirement #2:
Construction Stormwater Pollution Prevention
(SWPP)
2-17 through 2-26 Yes
Reorganized and revisions to: thresholds,
general requirements, construction SWPPP
elements, objective, and supplemental
guidelines.
Changes include: revisions to the construction SWPPP elements to
correspond with the Construction Stormwater General Permit, the
addition of element #13 that requires the protection of LID Best
Management Practices, and revision of element #12 to include
responsibilities for an inspector or CESCL depending on the size of the
project.
Section 2.5.4 Minimum Requirement #4:
Preservation of Natural Drainage Systems and
Outfalls
2-27 through 2-28 Yes Minor additions.Added clarification for peak discharges using 15 minute time steps.
Section 2.5.5 Minimum Requirement #5: On-site
Stormwater Management 2-28 through 2-32 Yes Multiple revisions for new low impact
development (LID) requirements.
Changes include: the new LID performance standard and list options
based on project size and location. The lists are divided into three land
use types: lawn and landscaped areas; roofs, and other hard surfaces.
Projects implementing the list option must select the first feasible BMP
for each land use type. Some of the BMPs included in the lists are: rain
gardens, permeable pavements, bioretention, soil quality and depth, full
and partial dispersion methods, full downspout infiltration and
perforated stub-outs.
Section 2.5.6 Minimum Requirement #6: Runoff
Treatment 2-33 through 2-35 Yes
Revisions to the thresholds, Water Quality
Design Flow Rate, and supplemental
guidelines.
Revisions made to acknowledge the use of permeable pavements and
the related new definitions. The intent is to continue to capture the
same size and types of projects as previously. More accurate definitions
for water quality design storm volume and flow rate.
Section 2.5.7 Minimum Requirement #7: Runoff
Flow Control 2-35 through 2-40 Yes Revisions to the thresholds and
supplemental guidelines.
Revisions to acknowledge the use of permeable pavements and the
related new definitions. Clarifications about the surfaces that the
requirement applies to, and the use of the 0.10 /0.15 cfs threshold. The
intent is to capture the same size and types of projects as previously.
Section 2.5.8 Minimum Requirement #8: Wetlands
Protection 2-40 through 2-41 Yes
Revisions to the applicability, thresholds,
standard requirement, additional
requirements, and supplemental guidelines.
Revisions correspond to the significantly revised Appendix I-D Guidelines
for Wetlands when Managing Stormwater .
Location Approximate Page
Numbers
Change Tied
to Permit
Language
Change Reasoning or Comments
Section 2.8 Exceptions/Variances 2-45 through 2-46 Yes Additional guidance provided.Changed and added language to be consistent with the requirements in
Appendix 1 of the 2007 municipal stormwater permits.
Chapter 3 - Preparation of Stormwater Site Plans 3-1 through 3-17 Yes
Significant changes to incorporate
procedures necessary for LID
implementation.
Revised for clarity and removed outdate language in the introduction
and in section 3.1.7.
Section 3.1.1 Step 1 - Collect and Analyze
Information on Existing Conditions 3-2 through 3-7 Yes Additional guidance provided and outdated
guidance removed.
Additional guidance details the information necessary for site analysis,
and in particular for LID site design. Split into subsections based on
whether Min. Requirements 1 - 5 apply, or Min. Requirements 1 - 9
apply.
Sections 3.1.2 to 3.1.4 3-7 through 3-8 Yes Guidance added.References to on-site BMPs added and preliminary determination of
applicable minimum requirements.
Section 3.1.5 Step 5 - Prepare a Permanent
Stormwater Control Plan 3-8 through 3-12 Yes
Revisions to all subsections of Developed
Site Hydrology of the Permanent
Stormwater Control Plan.
Significant changes to describe how to prepare the Permanent
Stormwater Control Plan that incorporates LID features. Separate
guidance for projects subject to Min. Requirements 1 - 5 and projects
subject to Min. Requirements 1 - 9.
Section 3.1.6 Step 6 - Prepare a Construction
Stormwater Pollution Prevention Plan 3-13 through 3-14 Yes Minor language changes.Changes for clarification and to remove repetitive language.
Section 3.1.7 Step 7 - Complete Stormwater Site
Plan 3-14 through 3-16 Yes
Reference to needed soils report and
addition of Declaration of Covenants and
Grants of Easement.
Soils reports are necessary part of LID decisions. Declarations of
Covenants and Grants of Easement are necessary mechanisms to identify
LID features, establish maintenance requirements and government
access for inspections of privately maintained stormwater BMPs and
facilities.
Section 3.2.2 Final Corrected Plan Submittal 3-17 Guidance added.Added several LID BMPs that require the submission of as-builts.
Section 4.2 BMP and Facility Selection Process 4-1 through 4-4
Revised language, proposed replacing the
language in Step V: Select Treatment
Facilities with a reference to Chapter 2 of
Volume V.
Revisions and new language especially in Step III for guidance on
modeling threshold discharge areas. Minor revisions to correspond with
the changes in the Municipal Stormwater Permits and for new LID
requirements. Ecology replaced the language in Step V: Select
Treatment Facilities with a reference to Chapter 2 of Volume V.
Appendix I-A Guidance for Altering the Minimum
Requirements Through Basin Planning A-1 through A-3 Additional guidance provided.Added language for clarity on use of Basin Planning for addressing
retrofit needs and for developing an alternative flow control strategy.
Appendix I-B Rainfall Amounts and Statistics B-1 through B-5
Removed introductory language and
background information on the Water
Quality Design Storm and Water Quality
Design Flow Rate.
Removed background and outdated information for brevity. Renamed
the appendix and retained the rainfall tables.
Chapter 3 - Preparation of Stormwater Site Plans
Chapter 4 - BMP and Facility Selection Process for Permanent Stormwater Control Plans
Appendix I-A Guidance for Altering the Minimum Requirements Through Basin Planning
Appendix I-B Rainfall Amounts and Statistics
Location Approximate Page
Numbers
Change Tied
to Permit
Language
Change Reasoning or Comments
Appendix I-D Guidelines for Wetlands when
Managing Stormwater D-1 through D-18 Yes
Multiple revisions for the use and/or the
protection of Wetlands when managing
stormwater.
Rewritten to remove outdated information, clarify concepts, and
approach the protection and use of wetlands through controlling
discharges to wetlands. Total discharges to wetlands must not deviate by
more than 20% on a single event basis, and must not deviate by more
than 15% on a monthly basis.
Appendix I-E Flow Control-Exempt Surface Waters E-1 through E-4 Yes Added and deleted Exempt Surface Waters.List edited to add additional waters based on specific requests and
analyses, and to remove reference to a creek in Eastern WA.
Appendix I-F Basins with 40% or more total
impervious area since 1985 F-1 Yes Added Map
Map shows basins which potentially qualify for use of existing land cover
as the pre-developed land cover for flow control purposes. See reference
in Min. Requirement #7.
Glossary and Notations Glossary-1 through
Glossary-47 Added and revised definitions.
There are a few terms, used previously but not defined, for which a
definition has been added. A handful of other terms have a revised
definition, and there are new terms, because of the new low impact
development (LID) guidance and requirements in the Municipal
Stormwater Permits.
Appendix I-D Guidelines for Wetlands when Managing Stormwater
Appendix I-E Flow Control-Exempt Surface Waters
Appendix I-F Feasibility Criteria for Selected Low Impact Development Best Management Practices
Glossary and Notations
Location Approximate Page
Numbers
Change Tied
to Permit
Language
Change Reasoning or Comments
Chapter 1 - Introduction Construction Stormwater
Pollution Prevention 1-1 through 1-9 Multiple revisions for plain language, clarity,
and brevity.Revised this chapter to use simpler and clearer language.
Section 1.3 How to Use This Volume N/A
This section was removed. The information
in this section is now included in Sections
1.2.
Removed this section by combining it with Section 1.2 to eliminate
duplicate language.
Section 1.3 Thirteen Elements of Construction
Stormwater Pollution Prevention 1-3 Yes Renamed.Revised to incorporate a new element, Protect Low Impact Development
BMPs.
Figure 1.5.1 1-6 Replaced.Replaced older figure with an updated one.
Chapter 2 - Regulatory Requirements 2-1 through 2-6 Multiple revisions for plain language, clarity,
and brevity.
Revised this chapter to use simpler and clearer language. Information
covered in Volume I, Section 1.6 Relationship of the Manual to Federal,
State, and Local Regulatory Requirements was removed.
Chapter 2 - Regulatory Requirements 2-1 through 2-6 Yes
Multiple revisions to coordinate the manual
to the Washington State General
Stormwater Permits.
Revised this chapter to update this information for revisions to the
Stormwater General Permits (including the Municipal, Construction, and
Industrial Permits).
Section 2.1 and Section 2.2 2-2 through 2-4 Yes
Section 2.1 The Construction Stormwater
General Permit and Section 2.2 Construction
Stormwater Pollution Prevention Plans now
replace the previous Sections 2.1 and 2.2.
Replaced these sections to remove invalid information or duplicate
information. Sections 2.1 and 2.2 now go into detail about the
relationship of Volume II to the Construction Stormwater General Permit
and the requirements for a Stormwater Site Pollution Prevention Plan.
Chapter 3 - Planning 3-1 through 3-32 Multiple revisions for plain language, clarity,
and brevity.
Revised this chapter to use simpler and clearer language. Information
covered in Volume I, Section 1.6 Relationship of the Manual to Federal,
State, and Local Regulatory Requirements was removed.
Section 3.2 and Section 3.3 3-4 through 3-32 Previous Sections 3.2 and 3.3 have been
reversed.
Moved The Construction SWPPP Requirements, previously in Section 3.3
to Section 3.2 for clarity. The Step-By-Step Procedure now follows in
Section 3.3. Please note that the Construction Stormwater Pollution
Prevention Plan Checklist is still located in Section 3.3.
Section 3.3.3 (Previously Section 3.2.3) Step 3 -
Construction SWPPP Development and
Implementation
3-8 through 3-32 Yes Multiple revisions to the Construction
SWPPP Elements.
Revised The Construction SWPPP Elements, described in Section 3.3.3 to
coordinate with the Construction Stormwater General Permit, Municipal
Stormwater Permits, and the Construction BMPs in Chapter 4. Each
element now contains an Additional Guidance section that has
information not required by the permits. Added Element #13 Protect
Low Impact Development BMPs.
Volume II Construction Stormwater Pollution Prevention
Chapter 1 - Introduction Construction Stormwater Pollution Prevention
Chapter 2 - Regulatory Requirements
Chapter 3 - Planning
Location Approximate Page
Numbers
Change Tied
to Permit
Language
Change Reasoning or Comments
Chapter 4 - Best Management Practices Standards
and Specifications 4-1 through 4-128 Added approved equivalent BMPs Sections.Refers to Ecology's website for BMPs that have been approved as
equivalent.
Section 4.1 Source Control BMPs 4-1 through 4-2 Yes Added Table 4.1 Source Control BMPs by
SWPPP Element
Ecology added Table 4.1 Source Control BMPs by SWPPP Element to
show how the BMPs listed in Section 4.1 relate to the SWPPP Elements.
BMP C103: High Visibility Fence 4-6
This BMP now includes high visibility silt
fence. Multiple revisions for plain language,
clarity, and brevity.
Added high visibility silt fence because it meets the intent of BMP C103.
Ecology revised this chapter to use simpler and clearer language.
BMP C104: Stake and Wire Fence N/A This BMP was removed.Removed this BMP because BMP C103: High Visibility Fence meets the
intent of this BMP in a safer and more commonly used manner.
BMP C105: Stabilized Construction Entrance / Exit 4-7 through 4-9 Additional guidance provided and outdated
guidance removed.
Added and removed guidance for this BMP based on comments received
and field experience.
BMP C106: Wheel Wash 4-9 through 4-11 Additional guidance provided and outdated
guidance removed.
Added guidance to clarify that wheel wash wastewater shall not
discharge to surface or ground water.
Figure 4.1.2 - Wheel Wash 4-11 Figure was updated Updated figure to provide more details of a typical Wheel Wash.
BMP C120: Temporary and Permanent Seeding 4-13 through 4-19
Multiple revisions for plain language, clarity,
and brevity. Additional guidance provided
and removed.
Revised and reorganized this BMP to use simpler and clearer language.
Moved some guidance to BMP C121: Mulching or BMP C125: Top soiling.
Ecology added and removed additional guidance for this BMP based on
comments received and field experience.
BMP C121: Mulching 4-19 through 4-21 Additional guidance provided.
Added minimum mulch thickness based on field experience and
comments. Ecology added guidance previously found in BMP C120:
Temporary and Permanent Seeding to this BMP.
Table 4.1.8 4-21 Additional guidance provided.Added Wood Straw and Wood Straw Mulch to the table.
BMP C122: Nets and Blankets 4-22 through 4-25 Multiple revisions for plain language, clarity,
and brevity.Revised this BMP to use simpler and clearer language.
BMP C123: Plastic Covering 4-25 through 4-27 Additional guidance provided and outdated
guidance removed.
Removed the use of plastic sheeting over seeded areas because other
coverings (such as compost and straw) are preferable. Ecology added
and removed guidance for this BMP based on comments received and
field experience.
BMP C124: Sodding 4-27 through 4-28 Additional guidance provided and outdated
guidance removed.
Provided a link to composting guidance and removed old reference to
compost specification.
BMP C125: Top soiling / Composting 4-29 through 4-32 Additional guidance provided and outdated
guidance removed.
Added guidance previously found in BMP C120: Temporary and
Permanent Seeding to this BMP. Ecology added and removed guidance
for this BMP based on comments received and field experience.
BMP C150: Materials on Hand 4-42 through 4-43 Suggested measures and quantities
removed.
Removed measures and quantities because measures and quantities
should be based on the size of the construction site.
Chapter 4 - Best Management Practices Standards and Specifications
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BMP C151: Concrete Handling and BMP C152:
Sawcutting and Surface Pollution Prevention 4-43 through 4-45 Yes Additional guidance provided.
Added guidance to coordinate this BMP with the requirements of the
Construction Stormwater General Permit and to make it clear that
Concrete spillage or concrete discard to surface waters of the State is
prohibited.
BMP C154: Concrete Washout Area 4-48 through 4-53 Added this BMP.Added this BMP to provide additional guidance for concrete washout
areas.
BMP C160: Certified Erosion and Sediment Control
Lead 4-54 through 4-55 Additional guidance provided and outdated
guidance removed.
Minimum Requirements for ESC Training and Certification Courses has
been removed. Ecology plans on issuing separate, updated guidance in
the near future.
BMP C161: Payment of Erosion Control Work N/A This BMP was removed.Removed this BMP because it is not applicable to the full range of
projects needing to perform Erosion and Sediment Control Work.
BMP C180: Small Project Construction Stormwater
Pollution Prevention N/A Yes This BMP was removed.
Removed this BMP because of changes in threshold requirements in
both the Municipal Stormwater General Permits and Construction
Stormwater General Permit.
Section 4.2 Runoff Conveyance and Treatment
BMPs 4-57 Yes Added Table 4.2 Runoff Conveyance
Treatment BMPs by SWPPP Element
Added Table 4.2 Runoff Conveyance Treatment BMPs by SWPPP Element
to show how the BMPs listed in Section 4.2 relate to the SWPPP
Elements.
BMP C207: Check Dams 4-74 through 4-77 Additional guidance provided.Added guidance for this BMP based on comments received and field
experience.
BMP C220: Storm Drain Inlet Protection 4-78 through 4-79 Additional guidance provided.Added guidance for inlet protection of lawn and yard drains and based
on comment received and field experience.
BMP C230: Straw Bale Barrier N/A This BMP was removed.Removed this BMP because this BMP has been proven to be ineffective.
BMP C233: Silt Fence 4-90 through 4-95 Multiple revisions for plain language, clarity,
and brevity.Revised and reorganized this BMP to use simpler and clearer language.
BMP C235: Wattles 4-96 through 4-99 Renamed from Straw Wattles.Renamed this BMP to include wattles made from compost or other
materials.
BMP C236: Vegetated Spray Fields 4-100 through 4-102 Added this BMP.Added this new BMP for dewatering, Construction SWPPP Element #10.
BMP C250: Construction Stormwater Chemical
Treatment 4-112 through 4-120 Additional guidance provided.
Added guidance for this BMP, previously available online, to
coordinate with the Chemical Technology Assessment Protocol
(CTAPE) program.
BMP C251: Construction Stormwater Filtration 4-120 through 4-124 Additional guidance provided.Added sizing criteria for this BMP, previously available online.
BMP C252: High pH Neutralization Using CO2 4-125 through 4-127 Added this BMP.Added this BMP, previously available online, to provide guidance
on neutralizing high pH through the use of CO2.
BMP C253: pH Control for High pH Water 4-128 through 4-129 Added this BMP.Added this BMP, previously available online, to provide additional
guidance for neutralizing high pH.
Appendix II-B Background Information on Chemical
Treatment B-1 through B-3 Multiple revisions to coordinate with BMP
C252 and BMP C53.
Revised this appendix to coordinate with the new information provided
in BMP C252 and in BMP C253.
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Chapter 2 - Hydrologic Analysis
Chapter 2 - Hydrologic Analysis 2-1 through 2-17 Multiple revisions for plain language, clarity,
and brevity.
Revised this chapter to use simpler and clearer language. Outdated
guidance was replaced.
Section 2.2 Western Washington Hydrology Model 2-4 through 2-9 Section 2.2 split into multiple subsections.Section 2.2 split into multiple subsections for clarity and for referencing
purposes.
Section 2.2 Western Washington Hydrology Model 2-4 through 2-9 Additional guidance provided.Added guidance on upcoming Western Washington Hydrology Model
(WWHM) changes.
Section 2.2.2 Assumptions made in creating the
WWHM 2-5 through 2-8 Additional guidance provided.Added guidance on precipitation data and upcoming WWHM changes.
Section 2.2.3 Guidance for flow-related standards 2-8 through 2-9 Yes
Additional guidance provided and outdated
guidance removed for Minimum
Requirements (MR).
Added guidance for MR #5 which now includes an LID Performance
Standard. Revised the guidance for MR#8 to reflect the changes made in
Volume I, Appendix 1-D.
Chapter 3 - Flow Control Design 3-1 through 3-109 Multiple revisions for plain language, clarity,
and brevity.Revised this chapter to use simpler and clearer language.
Chapter 3 - Flow Control Design 3-1 Yes Update text for consistency with revised Min
Req'mt #5 and LID
Added references to Minimum Requirement #5, bioretention and
permeable pavements in introductory section.
Section 3.1 Roof Downspout Controls 3-1 through 3-18 Yes Update text & figure for consistency with
revised Min Req'mt #5 Text and figures updated to indicate priorities for handling roof runoff.
Section 3.1 Roof Downspout Controls 3-1 through 3-3 Yes Update text for consistency with revised Min
Req'mt #5
Updated references to revised roof downspout BMPs and Rain Gardens
in the introductory section.
Section 3.1.1 Roof Downspout Full Infiltration (BMP
T5.10A)3-4 through 3-10 Yes Update text for consistency with revised Min
Req'mt #5
Text changes for consistency with new priority lists in Min.Req'ment #5
and feasibility criteria. Needed better clarity in design guidance
Section 3.1.2 Downspout Dispersion Systems 3-11 through 3-16 Yes Update text for consistency with revised Min
Req'mt #5
Text changes for consistency with new priority lists in Min. Req'ment #5
and feasibility criteria. Improved clarify in design guidance and
computer modeling. Added guidance for design criteria for dispersion
trenches and splashblocks.
Section 3.1.3 Perforated Stub-out Connections 3-17 through 3-18 Yes Update text for consistency with revised Min
Req'mt #5
Text changes for consistency with new priority lists in Min. Req'ment #5
and feasibility criteria. Updated design guidance.
Section 3.2 Detention Facilities 3-19 through 3-64 Multiple revisions for plain language, clarity,
and brevity.Revised this chapter to use simpler and clearer language.
Section 3.2 Detention Facilities 3-35 Updated references.Updated Maintenance narrative to refer to Appendix IV-G Management
of Street Wastes in Volume IV.
Section 3.3 Infiltration Facilities for Flow Control
and Treatment 3-65 through 3-102 Section significantly rewritten.
Made significant changes to all sub-sections. Section pertains primarily to
design of centralized infiltration facilities. Certain sections also apply to
distributed bioretention facilities as indicated in text.
Section 3.3.1 Purpose 3-65 Yes Revised guidance and reference LID.
Expanded purpose statement and clarified in regard to the types of
facilities covered in Section 3.3. Added references to Bioretention and
Permeable Pavement sections.
Section 3.3.2 Description 3-65 Yes Additional guidance provided including Min
Req'mt #5.
Made clarifications and added language for complying with MR#5. Added
guidance for oil control and pre-treatment facilities.
Section 3.3.3 Applications 3-66 Additional guidance provided.Minor text change
Section 3.3.4 Steps for Design of Infiltration
Facilities 3-68 through 3-71 Yes
Revised several steps for new infiltration
rate guidance and the new LID performance
standard.
Revised Step 2 to include guidance for meeting MR#5. Significantly
revised Step 5 for the new guidance provided in section 3.3.6. Revised
Step 6 for clarity and for meeting MR#5. Revised Step 7 for clarity.
Volume III Hydrologic Analysis and Flow Control Design / BMPs
Chapter 3 - Flow Control Design
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Section 3.3.5 Site Characterization Criteria 3-72 through 3-75
Revised guidance on subsurface
characterization, soil testing, and infiltration
receptor. Removed guidance for
hydrogeologic investigation and figure 3.27,
USDA Textural Triangle.
Multiple changes to subsurface characterization include added guidance
on groundwater monitoring wells and the use of grain size analysis
method for estimating infiltration rates. Deleted infiltration rate
determination sub-section due to redundancy with next section.
Section 3.3.6 Design Saturated Hydraulic
Conductivity - Guidelines and Criteria 3-75 through 3-83
Revisions for determining the saturated
hydraulic conductivity (infiltration rate).
Section renamed.
Replaced "Infiltration Rate" with "Saturated Hydraulic Conductivity"
throughout section. Updated the guidelines and criteria for determining
saturated hydraulic conductivity. Added guidance on pilot infiltration
testing (PIT), and soil grain size analysis. Revised correction factors for
PIT results and soil grain size method. Removed options based on USDA
Soil Texture Classification and D10 grain size.
Section 3.3.7 Site Suitability Criteria (SSC)3-83 through 3-86 Additional guidance provided and outdated
guidance removed.
Updated references, removed unneeded guidance, revised limits on
infiltration rates, added a minimum organic content for treatment,
amended drawdown guidance, and verification testing.
Section 3.3.8 Steps for Designing Infiltration
Facilities - Detailed Approach 3-86 through 3-90
Multiple revisions. Previous steps 1-4
removed. Multiple steps revised. Added
groundwater mounding analysis step.
Removed steps to select location, estimate volume of stormwater,
develop a trial infiltration facility geometry, conduct a geotechnical
investigation, and determine the saturated hydraulic conductivity;
instead refers to steps 1-5 in section 3.3.4. Revised Figure 3.27 for
updated guidance. Revised guidance for adjusting the preliminary design
infiltration rate. Added a step for groundwater mounding analysis.
Added guidance for conducting performance testing.
Section 3.3.9 General Design, Maintenance, and
Construction Criteria for Infiltration Facilities 3-90 through 3-94 Additional guidance provided and outdated
guidance removed.
Added guidance for sizing for flow control, pretreatment design criteria,
and maintenance. Made wording clarifications to guidance.
Section 3.4 Site Procedures for Bioretention and
Permeable Pavement Use 3-103 through 3-109 Yes Added this section for bioretention and
permeable pavement.
Added guidance re field tests, computer modeling, and implementation
for bioretention / rain gardens and permeable pavement.
Appendix III-A Isopluvial Maps for Design Storms A-1 Added link to website.Added a link to a website where isopluvial maps are available.
Appendix III-B Western Washington Hydrology
Model - Information, Assumptions, and
Computation Steps
B-1 through B-13 Yes Additional guidance provided and outdated
guidance removed.
Added guidance on current and upcoming versions of WWHM. Added
guidance for the modeling on LID elements and wetlands. Removed
outdated computation steps.
Appendix III-C Washington State Department of
Ecology Low Impact Development Flow Modeling
Guidance
C-1 through C-13 Yes Additional guidance provided and outdated
guidance removed.
Text in regard to design guidance removed. All design guidance moved
to Volume V. Two sets of modeling guidance provided. One for WWHM
3, and one for upcoming WWHM 2012.
Appendix III-D Procedure for Conducting a Pilot
Infiltration Test N/A Appendix removed.
Procedures for conducting the PIT have been included within the
proposed text on “Design Infiltration Rate Determination” in sections
3.3.6.
Appendix III-B Western Washington Hydrology Model - Information, Assumptions, and Computation Steps
Appendix III-C Washington State Department of Ecology Low Impact Development Design and Flow Modeling Guidance
Appendix III-D Procedure for Conducting a Pilot Infiltration Test
Appendix III-A Isopluvial Maps for Design Storms
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Chapter 1 - Introduction 1-1 through 1-5 Minor language changes.Revised for clarity and removed outdated language.
Section 1.3 How to Use this Volume 1-2 Additional guidance provided and outdated
guidance removed.
Added new guidance regarding the Industrial Stormwater General Permit
(ISWGP), Boatyard General Permit (BGP), and Sand and Gravel General
Permit (S&GP) and the inclusion of "applicable" BMPs from this volume
in Industrial Stormwater Pollution Prevention Plans (Industrial SWPPPs).
Section 1.5 Treatment BMPs for Specific Pollutant
Sources 1-3 Yes Additional guidance provided and outdated
guidance removed.
Added new guidance clarifying the requirements regarding treatment
BMPs for facilities covered under the ISWGP (or other General
Stormwater Permits).
Section 1.6.1 Applicable (Mandatory) BMPs 1-3 through 1-4 Additional guidance provided and outdated
guidance removed.
Added new guidance describing the use of applicable (mandatory) BMPs
in regards to the ISGP, BGP, and S&GP. Section renamed to make it
clearer that applicable BMPs are Mandatory for permittees under the
ISWGP and BGP.
Section 1.6.2 Recommended BMPs 1-4 Yes Additional guidance provided.Added guidance regarding facilities covered under the ISWGP that trigger
a corrective action.
Chapter 2 - Selection of Operational and Structural
Source Control BMPs 2-1 through 2-66 Numbered BMPs.Added numbers in the "S400" series to BMPs in Volume IV.
Chapter 2 - Selection of Operational and Structural
Source Control BMPs 2-1 through 2-66 Minor revisions for plain language, clarity,
and brevity.
Revised BMPs to use simpler and clearer language, and removed
outdated references.
Chapter 2 - Selection of Operational and Structural
Source Control BMPs 2-1 through 2-2 Additional guidance provided and outdated
guidance removed.
Added new guidance describing the use of applicable (mandatory) BMPs
in regards to the ISGP, BGP, and S&GP. Added guidance regarding
facilities covered under the ISWGP that trigger a Level 1 or 2 corrective
action.
Section 2.1 Applicable (Mandatory) Operational
Source Control BMPs 2-2 through 2-6 Additional guidance provided and outdated
guidance removed.
Revised wording to clarify where this Section applies. Revised several
BMPs for clarity and to coordinate with the ISWGP. Significant changes
include the addition of vacuum sweeping and pressure washing, spill
prevention and cleanup, visual inspections and record keeping.
Section 2.2 Pollutant Source Specific BMPs 2-7 through 2-66
Additional guidance provided and outdated
guidance removed. Minor formatting
revisions.
Revised wording to clarify where this Section applies. Added new text on
ISWGP requirements. Added guidance regarding facilities covered under
the ISWGP that trigger a Level 1 or 2 corrective action. Changed the title
format for the BMPs to match the other volumes and added a numbering
system to the BMPs.
S401 BMPs for the Building, Repair, and
Maintenance of Boats and Ships 2-7 through 2-9 Additional guidance provided and several
BMPs clarified.
Clarified guidance describing the requirements under the BGP and ISGP
regarding boatyard activities. Revised BMPs to use simpler and clearer
language.
S402 BMPs for Commercial Animal Handling Areas 2-10 Minor revisions for plain language, clarity,
and brevity.Revised BMPs to use simpler and clearer language.
S403 BMPs for Commercial Composting 2-10 through 2-12 Additional guidance provided and outdated
guidance removed.
Revised language because solid waste regulations prohibit discharge of
compost leachate. Revised BMPs to use simpler and clearer language,
and removed outdated references.
Volume IV Source Control BMPs
Chapter 1 - Introduction
Chapter 2 - Selection of Operational and Structural Source Control BMPs
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S405 BMPs for Deicing and Anti-Icing Operations -
Airports and Streets 2-13 through 2-14 Additional guidance provided and outdated
guidance removed.
Revised language to coordinate with the ISGP. Removed outdated
references.
S414 BMPs for Maintenance and Repair of Vehicles
and Equipment 2-32 through 2-34 Yes Revision for consistency with the ISGP Updated "applicable BMP" guidance for handling of liquids in scrap
vehicles to align with ISGP.
S416 BMPs for Maintenance of Roadside Ditches 2-35 through 2-37 Additional guidance provided and updated
references.Additional guidance provided for the handling of ditch cleanings.
S423 BMPs for Recyclers and Scrap Yards 2-45 through 2-46 Updated reference to guidance.Updated the reference to guidance for Vehicle Recyclers.
S424 BMPs for Roof/Building Drains at
Manufacturing and Commercial Buildings 2-46 through 2-47 Added reference to guidance.Added a references to Volume V and Ecology publications for BMPs.
S426 BMPs for Spills of Oil and Hazardous
Substances 2-48 through 2-49 Additional guidance provided and outdated
guidance removed.Revised several BMPs for clarity and to coordinate with the ISWGP.
S430 BMPs for Urban Streets 2-58 through 2-59 Additional guidance provided.Clarified that facilities not under the ISWGP may consider some water
use in street cleaning.
S431 BMPs for Washing and Steam Cleaning
Vehicles / Equipment / Building Structures 2-60 through 2-62 Yes Additional guidance provided and outdated
guidance removed.
Added guidance to clarify that the ISWGP prohibits the discharge of
process wastewater to ground water or surface water. Removed
outdated guidance.
Figure 2.15 - Uncovered Wash Area N/A Figure Deleted Figure was unclear and the existing text provided a better description of
the required controls.
S432 BMPs for Wood Treatment Areas 2-63 through 2-64 Additional guidance provided and several
BMPs clarified.
Clarified guidance describing which NPDES permit(s) regulate wood
treatment areas. Revised BMPs to use simpler and clearer language.
S433 BMPs for Pools, Spas, Hot Tubs and Fountains 2-64 through 2-66 Additional guidance provided.Added this BMP to provide further guidance consistent with BMPs within
this volume.
Appendix IV-A Urban Land Uses and Pollutant
Generating Sources A-1 through A-24 Minor language changes.Edits for clarity and to replace and revise guidance documents and WAC
references.
Commercial Composting - SIC 2875 A-14 Additional guidance provided Added "Potential Pollutant Generating Sources"
Appendix IV-B Stormwater Pollutants and Their
Adverse Impact B-1 through B-2 Minor language changes. Removed Table.Minor language changes for clarity. Removed the outdated Table in
Appendix IV-B.
Appendix IV-C Recycling/Disposal of Vehicle
Fluids/Other Wastes C-1 Minor language changes.Minor language changes for clarity.
Appendix IV-D Regulatory Requirements That
Impact Stormwater Programs D-1 through D-9 Minor language changes.Edits for clarity and to replace and revise guidance documents and WAC
references.
Appendix IV-E NPDES Stormwater Discharge
Permits E-1 through E-7 Yes Additional guidance provided and outdated
guidance removed.
Edits to make guidance consistent with the most recent industrial and
municipal stormwater permits.
Appendix IV-G Recommendations for Management
of Street Wastes G-1 through G-15
Multiple revisions for plain language, clarity,
and brevity. Additional guidance provided
and outdated guidance removed.
Removed outdated guidance and added new guidance in the
contamination in Street Waste Solids subsection. Reorganized the
disposal of street waste liquids subsection, no major content changes.
Minor revisions to the Site Evaluation subsection.
Appendix IV-C Recycling/Disposal of Vehicle Fluids/Other Wastes
Appendix IV-D Regulatory Requirements That Impact Stormwater Programs
Appendix IV-E NPDES Stormwater Discharge Permits
Appendix IV-G Recommendations for Management of Street Wastes
Appendix IV-A Urban Land Uses and Pollutant Generating Sources
Appendix IV-B Stormwater Pollutants and Their Adverse Impact
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Chapter 1 - Introduction 1-1 through 1-4 Minor revisions for plain language, clarity,
and brevity.
Revised BMPs to use simpler and clearer language, and removed
outdated references.
Section 1.4.3 Treatment Methods 1-2 through 1-4 Additional guidance provided and outdated
guidance removed.
Revised guidance for oil/water separation, pretreatment, infiltration,
filtration, emerging technologies, and on-line systems. Added
Bioretention as a treatment method.
Chapter 2 - Treatment Facility Selection Process 2-1 Additional guidance provided.Added paragraph on emerging technology options.
Section 2.1 Step-by-Step Selection Process for
Treatment Facilities 2-1 through 2-9
Minor revisions to the steps. Revised
description of surface waters triggering
enhanced treatment.
Revised selection process steps for clarity and to remove outdated
information. Revised the Treatment Facility Selection Flow Chart for
revised guidance throughout Volume V. Revised description of surface
waters triggering enhanced treatment for accuracy.
Figure 2.1.1 2-3 Revised list of options.
Some treatment BMP options removed, emerging technologies added,
one BMP renamed. Added a note for Phosphorous facilities that require
Enhanced Treatment.
Section 2.2 Other Treatment Facility Selection
Factors 2-9 through 2-11
Removed the subsection on Pollutants of
Concern, the Suggested Treatment Options
Table, and Ability of Treatment Facilities
Table.
Removed the Suggested Treatment Options Table and Ability of
Treatment Facilities Table because they provided limited usefulness and
removed the associated subsection, Pollutants of Concern.
Chapter Introduction Paragraph 3-1 Additional guidance provided.Added paragraph on emerging technology options.
Section 3.2 Oil Control Menu 3-2 through 3-3 Revised list of options.
Removed catch basin inserts and added emerging stormwater treatment
technologies. To date, no catch basin inserts have been approved though
the TAPE process but Ecology has approved one emerging technology.
Deleted the "Where Applied" section since it was duplicated from
Chapter 2.
Section 3.3 Phosphorous Treatment Menu 3-3 through 3-4 Revised list of options.
Removed amended sand filter (no design criteria have been developed
for this treatment), and media filter, added emerging stormwater
treatment technologies. Deleted the "Where Applied" section since it
was duplicated from Chapter 2.
Section 3.4 Enhanced Treatment Menu 3-5 through 3-7
Multiple revisions to remove outdated
guidance and to provide new guidance.
Revised list of options. Revised waters
triggering enhanced treatment consistent
with Chapter 2.
Revised the performance goal for dissolved metals. Removed Amended
Sand Filter. Added "vegetated" to "Compost Amended "Vegetated" Filter
Strip. Removed "rain garden" for consistency with proposal to distinguish
between "bioretention" and "rain gardens." Replaced "Ecology
Embankment" with "Media Filter Drain." Added emerging technologies.
Deleted the "Where Applied" section since it was duplicated from
Chapter 2.
Section 3.5 Basic Treatment Menu 3-7 through 3-9 Minor language changes for clarity. Revised
list of options.
Removed "rain garden" for consistency with proposal to distinguish
between "bioretention" and "rain gardens." Replaced "Ecology
Embankment" with "Media Filter Drain". Added Compost-amended
Vegetated Filter Strip. Removed Bio-infiltration Swale. Added emerging
technologies. Deleted the "Where Applied" section since it was
duplicated from Chapter 2.
Section 4.1.1 Water Quality Design Storm Volume 4-1 Yes Inserted updated modeling guidance.New guidance more accurately describes how volume is determined by
computer models.
Chapter 1 - Introduction
Chapter 2 - Treatment Facility Selection Process
Chapter 3 - Treatment Facility Menus
Chapter 4 - General Requirements for Stormwater Facilities
Volume V Runoff Treatment BMPs
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Section 4.1.2 Water Quality Design Flow Rate 4-1 through 4-2 Minor language changes for clarity.Revised language for clarity.
Section 4.1.3 flows Requiring Treatment 4-2 through 4-4 Minor language changes for clarity. Changes
to incorporate new terms.
Replaced "impervious" surfaces with "hard" surfaces in coordination with
general changes in terminology. Added guidance regarding pollution-
generating hard surfaces, pollution-generating impervious surfaces, and
pollution-generating pervious surfaces.
Section 4.6 Maintenance Standards for Drainage
Facilities 4-31 through 4-53 Yes Added new tables within overall set of
operation and maintenance standards
Changed "StormFilter" to "Manufactured Media Filters", added
information from WSDOT on Media Filter Drains and Compost Amended
Vegetated Filter Strips. Minor additions to the recommended
maintenance tables added. Added placeholders for Bioretention and
permeable pavement pending completion of the development of LID
maintenance standards grant.
Section 5.1 Purpose 5-1 Additional guidance provided.
Add reference to expanded BMP options and LID Manual to acknowledge
the expansion of Chapter 5 and source of additional design details (LID
Manual).
Section 5.2 Application 5-1 Yes Additional guidance provided.Revised application to refer specifically to Minimum Requirements #5,
#6, and #7.
Section 5.3 Best Management Practices for On-Site
Stormwater Management 5-1 through 5-2 Additional clarifying guidance provided. Full
list of BMPs provided.
Expanded the list of BMPs in sections 5.3.1 and 5.3.2. Revised language
and references for clarity.
Section 5.3.1 On-site Stormwater Management
BMPs 5-3 to 5-39 Yes Amend existing BMP's add new BMP's
Downspout infiltration moved to Volume III. Revised BMP T5.11
Concentrated Flow Dispersion and BMP T5.12 Sheet Flow Dispersion.
Updated figures. Added BMP T5.14A Rain Gardens and BMP T5.14B
Bioretention but details are in Volume V of Chapter 7. Added BMP T5.15
Permeable Pavements, BMP T5.16 Tree Retention and Tree Planting,
BMP T5.16 Vegetated Roofs, BMP T5.18 Reverse Slope Sidewalks, BMP
T5.19 Minimal Excavation Foundations, BMP T5.20 Rainwater Harvesting.
Revised BMP T5.30 Full Dispersion by incorporating details from previous
Appendix III-C.
Section 5.3.2 Site Design BMPs 5-39 through 5-42 Deleted Full Dispersion and section 5.3.3
Other Practices
Moved Full Dispersion into Section 5.3.1 because the Municipal
Stormwater Permits make it a necessary option in MR #5. Clarifying
statement added in BMP T5.40.
Section 6.1 Purpose 6-1 Minor language changes.Removed "and media filtration" in first bullet for clarity.
Section 6.2 Application 6-1 Additional guidance provided.Added discussion that there are emerging technologies approved for
pretreatment.
Section 6.3 Best Management Practices (BMPs) for
Pretreatment 6-1 Additional guidance provided.Added reference to Chapter 12.
Section 7.1 Purpose 7-1 Changed bioinfilltration to bioretention.Updated listed BMPs and made minor revisions to text.
Sections 7.2 General Considerations 7-1 Additional guidance provided.Renamed this Section and added information regarding Bioretention and
Rain Gardens.
Sections 7.3 Applications 7-1 through 7-2 Additional guidance provided.Renamed this Section and added information for the BMPs discussed in
this chapter.
Chapter 6 - Pretreatment
Chapter 7 - Infiltration and Bioretention Treatment Facilities
Chapter 5 - On-Site Stormwater Management
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BMP T 7.30 Bioretention Cells, Swales, and Planter
Boxes 7-3 through 7-25
Replaced Bio-infiltration Swale with
Bioretention Cells, Swales, and Planter
Boxes.
Added detailed guidance, design criteria, infeasibilty criteria and figures
for Bioretention Cells, Swales, and Planter Boxes.
BMP T7.40 Compost-amended Vegetated Filter
Strips (CAVFS)7-25 through 7-29 Transferred this BMP from Chapter 9.Added guidance and design criteria for Compost-Amended Vegetated
Filter Strips. Treatment via infiltration through amended soils.
Chapter 8 - Filtration Treatment Facilities 8-1 through 8-39 Changed title and introduced minor
language changes for clarity.Revised name from Sand Filtration to just Filtration.
8.1 Purpose 8-1 Revised guidance.Revised the purpose to apply to both sand and media filtration facilities.
8.2 Description 8-1 Additional guidance provided.Added reference to Media Filter Drain to description.
Section 8.3 Performance Objectives 8-2 Included new technologies Added Media Filter Drain to list of approved technologies. Clarified
objective for sand filters.
Section 8.4 Applications and Limitations 8-2 Revised guidance.Revised to include media filter drains.
Section 8.5 Best Management Practices (BMPs) for
Sand Filtration / BMP T8.10 Sand Filter Basin 8-2 to 8-15 Renamed and reorganized section.
Additional guidance provided.
Added design criteria for sand filter basins. reorganized section so that
previous sections 8.5, 8.6, 8.7, & 8.8 become subsections under BMP
T8.10.
BMP T8.11 Large Sand Filter Basin 8-16 through 8-17 Separated out BMP previously reference
within BMP T8.10
BMP T8.11 Large Sand Filter Basin was described in the prior manual
under BMP T8.10 Sand Filter Basin. The Large Sand Filter was given a
separate BMP for clarity.
BMP T8.20 Sand Filter Vault 8-17 through 8-23 Additional guidance provided.Added design criteria, construction criteria, and maintenance criteria for
sand filter vault.
BMP T8.40 Media Filter Drain 8-24 through 8-38 Added this BMP.
Added design criteria for new Media Filter Drain (MFD) option
(previously referred to as Ecology Embankment). Text matches WSDOT
Highway Runoff Manual.
Chapter 9 - Biofiltration Treatment Facilities 9-1 through 9-26 Minor language changes for clarity.Minor language changes for clarity throughout the chapter.
Section 9.4 Best Management Practices 9-1 through 9-26 Additional guidance provided and outdated
guidance removed.Revised list of BMPs. Revised Sizing Criteria table for clarity.
BMP T9.50 Narrow Area Filter Strip N/A Removed this BMP.No design criteria exists for this BMP to validate basic treatment.
Designers should refer to Basic Filter Strip.
BMP T10.10 Wet Pond 10-1 through 10-17 Minor language changes for clarity.
First cell must be lined to be consistent with liner requirements in
Chapter 4. Added cell requirements for consistency with design criteria
for 2-cell ponds. Definition of WQ Design Storm Volume amended.
BMP T11.10 API (Baffle type) Separator Bay 11-8 through 11-9 Corrected formula.Corrected Stokes Law equation for rise rate.
BMP T11.11 Coalescing Plate (CP) Separator Bay 11-10 through 11-11 Corrected formula.Corrected the equation to calculated the projected (horizontal) surface
area of plates.
Chapter 12 - Emerging Technologies 12-1 through 12-6 Replaced sections 12.1 through 12.5 with
new guidance.
Replaced sections 12.1 through 12.5 to provide new guidance on the
Technology Assessment Protocol (TAPE) review and approval process.
Chapter 11 - Oil and Water Separators
Chapter 12 - Emerging Technologies
Chapter 8 - Sand Filtration Treatment Facilities
Chapter 9 - Biofiltration Treatment Facilities
Chapter 10- Wetpool Facilities
Location Approximate Page
Numbers
Change Tied
to Permit
Language
Change Reasoning or Comments
Section 12.6 Examples of Emerging Technologies
for Stormwater Treatment and Control N/A Removed examples of emerging
technologies.
Removed examples of emerging technologies. Added some examples
previously listed throughout this volume.
Appendix V-B Recommended Modifications to
ASTM D 2434 When Measuring Hydraulic
Conductivity for Bioretention Soil Mixes.
B-1 through B-2 Additional guidance provided.
Added Recommended Modifications to ASTM D 2434. The results of this
test for saturated hydraulic conductivity can be influenced by how the
general procedures in the ASTM method are implemented. This
appendix lays out more specific procedures to help with consistency in
evaluating soils used for bioretention.
Appendix V-C Geotextile Specifications C-1 through C-3 Revised Guidance.Corrected several test procedures and geotextile property requirements.
Appendix V-E Recommended Newly Planted Tree
Species E-1 through E-5 New appendix pertinent to BMP T5.16 Lists of species from City of Seattle guidance.
Appendix V-C Geotextile Specifications
Appendix V-B Recommended Procedures for ASTM D 2434
Appendix V-E Recommended Bioretention Plant Species
Location Change Reasoning or Comments
Updated date in footer Date updated to reflect the manual's revision date
Updated page numbers and Figure numbers as
appropriate Page and Figure numbers may have changed due to content insertion or deletion
Updated Table of Contents as appropriate Some page numbers may have changed due to content insertion or deletion
Minor spelling corrections examples include: groundwater changed to ground water; under‐drain changed to underdrain
Minor text clarifications examples include: changing "the Department of Ecology" to "the Washington State Department of
Ecology"; inserting and/or clarifying acronyms where appropriate
Minor typographical errors examples include changing "text" to test" and "lopers" to "loppers"
Updates per previous errata Updates per previously published errata to the 2012 SWMMWW have been incorporated
Volume I Acknowledgements Minor language changes Inserted text indicating the shorthand for "The Washington State Department of Ecology" is "Ecology",
added Craig Doberstein to the acknowledgement list, reformated the acknowledgement list
Section 1.1 ‐ Objective corrected "Ground Waters" to "Groundwaters"Although the rest of the manual uses the spelling "ground water" (two separate words), the spelling
here was updated to be consistent with the WAC title referenced
Section 1.6.4 ‐ The Puget Sound Action Agenda Revised this section Revision of this section reflects changes from the Puget Sound Partnership's 2008 Action Agenda to the
Puget Sound Partnership's 2014/2015 Action Agenda
Deleted sentence: "They are considered
redevelopment."
These practices are not restricted to redevelopment projects. The bullets that follow this sentence
properly indicate that how the surfaces are considered within new or redevelopment projects.
Restored formatting for second bullet
See the 2012 to 2014 SWMMWW Redlines for full change details.
2012‐2014 SWMMWW Chart of Changes
Volume I ‐ Minimum Technical Requirements and Site Planning
Chapter 1 ‐ Introduction
Chapter 2 ‐ Minimum Requirements for New Development and Redevelopment
All Volumes
Section 2.2 ‐ Exemptions
Restored formatting for second bullet
regarding extending the pavement edge.Formatting error correction
Section 2.3 ‐ Definitions definitions have been moved from seciton 2.3
to the Glossary definitions have been moved in an effort to consolidate and organize the SWMMWW
revised wording to read "volumetric flow rate
calculated using a 10‐minute time step"edit made to accurately describe the design criterion
revised "with outfall to" to "that discharges to" revision made per settlement agreement PCHB No. 12‐097c
Section 2.5.5 ‐ Minimum Requirement #5: On‐Site
Stormwater Management Added Figure 2.5.1: MR5 Flow Chart A flow chart to help determine MR5 requirements
Added text: "Testing should occur between
December 1 and April 1."Clarification
Under Projects required to meet MR 1‐9: 2.c.,
revised cited clearances Revised to be consistent throughout the manual
Section 3.1.2 ‐ Step 2 ‐ Prepare Preliminary
Development Layout
Added text referring to LID manual for
additional information clarification
Added a definition for "Biosolids"Clarification
Deleted the definition for "Commercial
Agriculture"The entry deleted was a duplicate entry and out of aphabetical orderGlossary
Chapter 3 ‐ Preparation of Stormwater Site Plans
Appendix I‐G ‐ Glossary and Notations
Section 2.5.2 ‐ Minimum Requirement #2:
Construction Stormwater Pollution Prevention
(SWPP)
Section 3.1.1 ‐ Step 1 ‐ Site Analysis: Collect and
Analyze Information on Existing Conditions
2012‐2014 SWMMWW Chart of Changes 1 Revised April 2015
Location Change Reasoning or Comments
Deleted the definition for "Converted
Vegetation (areas)"The entry deleted was a duplicate entry and out of aphabetical order
Commercial Agriculture definition ‐ replaced
the word "wholesale" with "commercial" within
the definition
Clarification
Amended definition for compost. Deleted
composted mulch and composting.Updated to correct WAC reference.
Added a definition for "Discharge Point"Added for consistency with proposed permit modification as part of a settlement under PCHB No. 12‐
093c and ‐ 097c
Updated freeboard definition Reworded for clarification
revised "Low Permeable Liner" definition revised to be consistent with other text within the manual
Added a definition for "Mulch"Clarification
Added definition for "outfall"Added for consistency with proposed permit modification as part of a settlement under PCHB No. 12‐
093c and ‐ 097c
Deleted reference to Rain Garden Handbook in
"Rain Garden" definition. Ecology prefers users to first refer to the guidance within the SWMMWW
Updated "receiving waters" definition Revised for consistency with proosed permit modification as part of a settlement under PCHB No. 12‐
093c and ‐ 097c
revised wording to read "volumetric flow rate
calculated using a 10‐minute time step"edit made to accurately describe the design criterion
revised "sites larger than 1 acre" to "applies
only to sites that have coverage under the
Construction Stormwater General Permit"
revised to clarify the intent of the original wording
Glossary
Volume II ‐ Construction Stormwater Pollution Prevention
Chapter 3 ‐ Planning
Section 3.3.3 ‐ Step 3 ‐ Construction SWPPP
Development and Implementation
added wording to clarify that the LID Technical
Guidance Manual is for additional informational
purposes only
Clarification that the SWMMWW guidance overrules the LID Technical Guidance Manual if discrepancies
are found
Section 4.1 ‐ Source Control BMPs
Table 4.1.1 updated to match Errata, and
reformatted as a word table for ease in future
revisions
See 10/14/2013 Errata
BMP C121: Mulching
Added a specification for coarse compost for
use when the option of Composted Material is
selected
Clarification
BMP C121, Table 4.1.8
Replaced the terms "composted mulch and
compost" with terms consistent with WAC 173‐
350
Clarification
BMP C125: Topsoiling/Composting Updated for consistency with BMP T5.13 Clarification
BMP C151: Concrete Handling Updated sentence to clarify that concrete
washout cannot be discharged to ground Clarification
Updated sentence to clarify that concrete
washout cannot be discharged to ground Correction
Removed wording telling volume of wash water
typically used Clarification
Chapter 4 ‐ Best Management Practices Standards and Specifications
BMP C154: Concrete Washout Area
2012‐2014 SWMMWW Chart of Changes 2 Revised April 2015
Location Change Reasoning or Comments
Section 4.2 ‐ Runoff Conveyance and Treatment
BMPs
Table 4.2.1 updated to match Errata, and
reformatted as a word table for ease in future
revisions
Clarification
BMP C200: Interceptor Dike and Swale revised wording to read "volumetric flow rate
calculated using a 10‐minute time step"edit made to accurately describe the design criterion
BMP C201: Grass‐Lined Channels revised wording to read "volumetric flow rate
calculated using a 10‐minute time step"edit made to accurately describe the design criterion
BMP C204: Pipe Slope Drains revised wording to read "volumetric flow rate
calculated using a 10‐minute time step"edit made to accurately describe the design criterion
Section 2.2 ‐ Western Washington Hydrology Model
updated sentence to state that low impact
development modeling capabilities have been
added to WWHM2012
wording was revised to reflect updates to WWHM since the last publishing of the SWMMWW
Section 2.2.1 ‐ Limitation to the WWHM
Clarified that routing limitations in the earlier
versions of WWHM (WWHM1 and WWHM2)
have changed considerably. WWHM3 and
WWHM2012 have much greater routing
capability that allow them to model multiple
facilities and wetlands
wording was revised to reflect updates to WWHM since the last publishing of the SWMMWW
Clarified that WWHM2012 now uses over 50
years of precipitation time series from more
than 17 stations. Precipitation time series are
in 15‐minute time steps
wording was revised to reflect updates to WWHM since the last publishing of the SWMMWW
Chapter 2 ‐ Hydrologic Analysis
Volume III ‐ Hydrologic Analysis and Flow Control BMPs
in 15 minute time steps.
Clarified that WWHM2012 now uses 15‐minute
precipitation time series in its computations to
generate hydrographs and to calculate water
quality design flows
wording was revised to reflect updates to WWHM since the last publishing of the SWMMWW
Clarified that the advanced user may change
coefficient Precipitation multiplication factor
where justified and approved by reviewing
jurisdiction
Clarification
Clarified that the advanced user may change
coefficient Pan evaporation coefficient
justified and approved by reviewing jurisdiction
Clarification
Section 2.2.3 ‐ Guidance for Flow‐Related Standards
Noted the updated capability to model flows to
wetlands and analyze the daily and monthly
flow deviations per MR 8 in WWHM2012
wording was revised to reflect updates to WWHM since the last publishing of the SWMMWW
Section 2.3.2 ‐ Runoff Parameters
Added footnote to Table 2.3.1 allowing
modeling soils with a measured infiltration rate
of less than 0.3 in/hr as Class C
Clarification
Section 2.2.2 ‐ Assumptions Made in Creating the
WWHM
2012‐2014 SWMMWW Chart of Changes 3 Revised April 2015
Location Change Reasoning or Comments
Section 3.1 ‐ Roof Downspout Controls
Updated wording that directs user to BMP
design guidance within the SWMMWW instead
of the Rain Garden handbook
Clarification
Revised subsection title from "Flow Credit for
Roof Downspout Full Infiltration" to "Runoff
Modeling for Roof Downspout Full Infiltration"
Clarification
revised sentence to clarify that clearance is
measured to the seasonal high ground water
table
Clarification
Revised subsection title from "Flow Credit for
Roof Downspout Dispersion" to "Runoff
Modeling for Roof Downspout Dispersion"
Clarification
Added modeling guidance where a dispersion
trench is used with a vegetated flowpath of 25
to 50 feet.
Clarification
removed footnote defining "Vegetative Flow
Path"
Added text to Emergency Overflow Spillway
section to ensure a min 1 foot of freeboard in
detention pond design
Clarification
Updated Landscaping section to refer to BMP
T5.13.Clarification
Added a reference to the Maintenance Tables
in Volume V, removed the Maintenance Tables
from this section
tables have been moved in an effort to consolidate and organize the SWMMWW
Chapter 3 ‐ Flow Control Design
Section 3.1.1 ‐ Downspout Full Infiltration Systems
(BMP T5.10A)
Section 3.1.2 ‐ Downspout Dispersion Systems (BMP
T5.10B)
Section 3.2.1 ‐ Detention Ponds
revised wording to read "volumetric flow rate
calculated using a 10‐minute time step"edit made to accurately describe the design criterion
Section 3.2.2 ‐ Detention Tanks
Added a reference to the Maintenance Tables
in Volume V, removed the Maintenance Tables
from this section
tables have been moved in an effort to consolidate and organize the SWMMWW
Section 3.2.4 ‐ Control Structures
Added a reference to the Maintenance Tables
in Volume V, removed the Maintenance Tables
from this section
tables have been moved in an effort to consolidate and organize the SWMMWW
Section 3.3.4 ‐ Steps for the Design of Infiltration
Facilities ‐ Simplified Approach
Sentence added "Testing should occur between
December 1 and April 1"Clarification
Updated SSC‐2 Ground Water Protection Areas
per Errata See 10/14/2013 Errata
Corrected reference cited in SSC‐6 Correction
Removed reference to the LID Technical
Guidance Manual for Puget Sound Ecology wants users to first consider the design guidance within the SWMMWW.
Revised wording to state design criteria "per
BMP T5.14A" instead of the Rain Garden
Handbook
Ecology wants users to first consider the design guidance within the SWMMWW.
Section 3.4.2 ‐ Description
Section 3.3.7 ‐ Site Suitability Criteria (SSC)
2012‐2014 SWMMWW Chart of Changes 4 Revised April 2015
Location Change Reasoning or Comments
Section 3.4.2 ‐ Description
Added statement allowing infiltration through
the side slopes to be modeled for facilities with
side slopes 3H:1V or flatter
Clarification
WWHM Information and Assumptions ‐ Precipitation
Data
Revised text to state that WWHM2012 uses 15‐
minutes precipitation time series Clarification
Added statement that soils tested at less than
0.3 in/hr may be modeled as Class C soil.Clarification
Clarified that type D soil is generally modeled
as till and saturated soil category in WWHM is
to be used for wetlands
Clarification
Updated text that conflicted with information
elsewhere in the manual Clarification
Updated text that the Appendix C guidance was
developed before WWHM2012 became
available. WWHM2012 can model permeable
pavements directly.
Clarification
Added statements concerning adjustment of
LSUR, SLSUR, and NSUR by the model user Clarification
Added a paragraph explaining WWHM2012and
WWHM3 provides 2 additional land slopes, flat
and steep, to the existing moderate land slope
for modeling purposes
Clarification
WWHM Information and Assumptions ‐
Development Land Use Data
WWHM Information and Assumptions ‐ PERLND and
IMPLND Parameter Values
Appendix III‐B ‐ Western Washington Hydrology Model ‐ Information, Assumptions, and Computation Steps
WWHM Information and Assumptions ‐ Soil Data
for modeling purposes
Appendix III‐C
Added a "Note" that the guidance in Appendix
C was developed for use with WWHM3 before
WWHM2012 became available.
Clarification
Part 1 C.2.3 ‐ Partial Dispersion on Residential Lots
and Commercial Buildings
Clarified guidance for consistency with text
regarding modeling of partial dispersion
options.
Clarification
Part 1 C.10.1 ‐ Runoff Model Representation Added guidance regarding modeling
bioretention that has an underdrain Clarification
Part 1 C.11.1 ‐ Instructions for Roads on Zero to 2%
Grade
Added guidance regarding modeling permeable
pavement that has underdrains at the bottom
of base course
Clarification
Part 1 C.11.2 ‐ Instructions for Roads on Grades
above 2%
Added guidance regarding modeling permeable
pavement that has underdrains at the bottom
of base course
Clarification
Part 2 Downspout Dispersion ‐ BMP T5.10B Inserted guidance for downspout dispersion
modeling Clarification
Part 2 Bioretention ‐ BMP T7.30 Added modeling guidance on Bioretention with
underlying perforated drain pipes Clarification
Appendix III‐C ‐ Washington State Department of Ecology Low Impact Development Flow Modeling Guidance
2012‐2014 SWMMWW Chart of Changes 5 Revised April 2015
Location Change Reasoning or Comments
S403 BMPs for Commercial Composting revised text to reflect updated regulations and
guidance Clarification
S411 BMPs for Landscaping and Lawn/Vegetation
Management
Revised S411 BMP bullet point to clarify use of
pesticides in Landscaping Clarification
S430 BMPs for Urban Streets deleted reference to Vol. V, Ch. 12 which no
longer has information on sweepers Clarification
S431 BMPs for Washing and Steam Cleaning
Vehicles/Equipment/Building Structures Revised text to reference updated guidance Clarification
Total Copper added to Table G.4 Copper overlooked in previous editions
Added note that the Interim Compost
Guidelines are no longer effective. Retained for
background info.
Clarification
Section 2.1 ‐ Step‐by‐Step Selection Process for
Treatment Facilities
Step 5: revised "urban growth management
area" to "urban growth area"Clarification
Revised "urban growth management area" to
"urban growth area"Clarification
Bioretention: removed text directing reader to
LID Manual for bioretention guidance. Text
now directs reader to Chapter 7 only. (Text
within Chapter 7 refers to the LID manual for
Clarification
Contamination in Street Waste Solids
Section 3.4 ‐ Enhanced Treatment Menu
Chapter 3 ‐ Treatment Facility Menus
Volume IV ‐ Source Control BMPs
Chapter 2 ‐ Selection of Operational and Structural Source Control BMPs
Appendix IV‐G ‐ Recommendations for Management of Street Wastes
Volume V ‐ Runoff Treatment BMPs
Chapter 2 ‐ Treatment Facility Selection Process
p
additional guidance)
Deleted: “The goal also applies on an average
annual basis to the entire annual discharge
volume (treated plus bypassed).”
Clarification ‐ See 10/14/2013 Errata
Bioretention: removed text directing reader to
LID Manual for bioretention guidance. Text
now directs reader to Chapter 7 only. (Text
within Chapter 7 refers to the LID manual for
additional guidance)
Clarification
Section 4.1.2 ‐ Water Quality Design Flow Rate (last sentence of section) Deleted reference to
an average annual performance goal Indefinite determination.
Section 4.1.4 ‐ Minimum Treatment Facility Size New section re minimum treatment facility size Additional guidance provided on the minimum treatment facility size.
Section 3.5 ‐ Basic Treatment Menu
Chapter 4 ‐ General Requirements for Stormwater Facilities
2012‐2014 SWMMWW Chart of Changes 6 Revised April 2015
Location Change Reasoning or Comments
Section 4.6 ‐ Maintenance Standards for Drainage
Facilities
Updated Tables 21&22 with information from
LID O&M Guidance document, with note that
inspection and routine maintenance
frequencies are recommended only.
Guidance added per PCHB No. 12‐093c and ‐ 097c
Section 5.1 ‐ Purpose Added text clarifying that LID manual is for
additional guidance only.Clarification
Section 5.3.1 ‐ On‐Site Stormwater Management
BMPs
Added bullet under Competing Needs on local
codes Clarification
BMP T5.11: Concentrated Flow Dispersion Added modeling guidance for use of dispersion
trench with flowpath of 25‐50 feet Additional guidance for runoff modeling
BMP T5.12: Sheet Flow Dispersion Added modeling guidance for use of dispersion
trench with flowpath of 25‐50 feet Additional guidance for runoff modeling
BMP T5.13: Post‐Construction Soil Quality and Depth
Updated the compost specification
requirement to be consistent with the
Bioretention compost specification but allowing
use of biosolids
Corrected WAC reference, made clarifications
Revised Rain Garden Handbook reference to
specify 2013 version Clarification per PCHB No. 12‐093c and ‐ 097c
Added a design guideline concerning use of
composts Additional Guidance for rain gardens
Provided guidance for sizing rain gardens
serving lawn/landscape areas in addition to
impervious surfaces
Additional Guidance for rain gardens
Provided guidance for underdrains in rain Additional Guidance for rain gardens
BMP T5.14A: Rain Gardens
Chapter 5 ‐ On‐Site Stormwater Management
gardens Additional Guidance for rain gardens
updated the maintenance section to refer to
both the Rain Garden Handbook and the
Western Washington LID O&M Guidance
Document
Additional Guidance for rain gardens
BMP T5.14B: Bioretention
Provided guidance for sizing bioretention
facilities serving lawn/landscape areas in
addition to impervious surfaces
Additional Guidance for bioretention facilities
Revised guideline regarding the amount of
impervious area draining to a pervious area Clarification
Revised infeasibility criterion for permeable
pavement and roads re PCHB decision Revised to implement PCHB No. 12‐093c and ‐097c
Deleted the second sentence of the infeasibility
criterion addressing road sanding for snow and
ice, Per PCHB ruling
Deleted per PCHB No. 12‐093c and ‐ 097c
New text in regard to municipalities designating
areas as infeasible and the data required Clarification and additional guidance as directed by PCHB No. 12‐093c and ‐ 097c
BMP T5.15: Permeable Pavements
2012‐2014 SWMMWW Chart of Changes 7 Revised April 2015
Location Change Reasoning or Comments
Revised 1st paragraph of "Design Guidelines"
section to clarify that LID Manual is for
additional guidance only, and that alternatives
adopted by municipalities must not conflict
with Ecology design criteria.
Clarification
Removed reference to the LID manual in the
"Base Material" section. The LID manual is
already referenced as additional guidance in
the opening paragraph.
Clarification
"Wearing layer": updated infiltration rate in
first sentence from 10 in/hr to 20 in/hr. The 10
in/hr rate was a typo and conflicted with
information given later in this section.
Clarification
Removed reference to the LID manual in the
"Wearing Layer", "Pervious Concrete", and
"Permeable Interlocking Concrete Pavement
and Aggregate Pavers" sections. The LID
manual is already referenced as additional
guidance in the opening paragraph.
Clarification
"Underdrains": Added a section regarding
underdrains affecting the status of permeable
pavements as LID BMPs
Additional Guidance for permeable pavements
added a reference to Table 22 within Table
452in Chapter 4 for maintenance guidance Additional Guidance for permeable pavements
BMP T5.15: Permeable Pavements
4.5.2 in Chapter 4 for maintenance guidance
BMP T5.17: Vegetated Roofs Added text clarifying that LID manual is for
additional guidance only.Clarification
Corrected section sub header name Clarification, the guidance is not only for residential projects
Corrected design requirements for residential
projects text for clarity Clarification
Revised "urban growth management area" to
"urban growth area"Clarification
Replaced Figure 7.4.1 Clarification
Added Figure 7.4.1b Clarification
Added Figure 7.4.1c Clarification
New text in regard to municipalities designating
areas as infeasible and the data required
Additional guidance to be consistent with directive of PCHB No. 12‐093c and ‐ 097c for permeable
pavement
Determining Bioretention soil mix infiltration
rate: Updated Ksat Safety Factor language for
consistency with WWHM.
Clarification
BMP T7.30: Bioretention Cells, Swales, and Planter
Boxes
BMP T5.30: Full Dispersion
Chapter 7 ‐ Infiltration and Bioretention Treatment Facilities
2012‐2014 SWMMWW Chart of Changes 8 Revised April 2015
Location Change Reasoning or Comments
Design criteria for bioretention ‐ updated text
to clarify that LID manual is additional guidance
only; under "curb cuts for roadside, driveway,
and parking lot areas" ‐ removed reference to
LID manual because it is already referenced in
the design criteria opening paragraph.
Clarification
Added text to "ponding area" section
describing surface areas when designing for
MR5
For consistency w/Min. Requirement #5 and recommendation for size increase if draining pervious area
Default Bioretention Soil Media: Multiple
changes to the compost specification; and to
incorporate a specification for fine compost
Changes needed to be consistent with updated WAC 173‐350‐220; Incorporated fine compost spec. to
delete reference to LID Manual
Design Criteria for Custom Bio Soil Mixes:
Added text clarifing that custom mix does not
need to meet gradation specification
Clarification
Soil Depth: Removed guidance for 24" BSM
depth Additional Guidance for bioretention facilities. Local monitoring indicates phosphorus loss from media.
Underdrain (optional): Added guidance for
modeling bioretention with underdrains Additional Guidance
Added text to clarify that LID manual is
additional guidance only.Clarification
Added statement that compost shall not
include biosolids or manures Clarification
Soil Design Criteria: Emphasized exclusion of
biosolids and manure from compost used for ClarificationBMP T7.40: Compost‐Amended Vegetated Filter
BMP T7.30: Bioretention Cells, Swales, and Planter
Boxes
CAVFS
Maintenance: deleted bullets per Errata Clarification ‐ See 10/14/2013 Errata
BMP T8.30: Linear Sand Filter Additional Design Criteria for Linear Sand
Filters: corrected text Correction
BMP T8.40: Media Filter Drain Grass Strip: restricted compost to that used for
Bioretention soil media Clarification
revised wording to read "volumetric flow rate
calculated using a 10‐minute time step"edit made to accurately describe the design criterion
Soil Criteria: SC‐15: Restricted compost to that
used for Bioretention soil media Clarification
BMP T9.40: Basic Filter Strip Corrected error in figure 9.4.9 Correction
Section 11.6 ‐ Design Criteria ‐ General
Considerations Corrected Schueler citation from 1990 to 1992 Correction
BMP T11.11: Coalescing Plate (CP) Separator Bay Clarification in design flowrate variable Clarification
Strips
BMP T9.10: Basic Biofiltration Swale
Chapter 9 ‐ Biofiltration Treatment Facilities
Chapter 11 ‐ Oil and Water Separators
2012‐2014 SWMMWW Chart of Changes 9 Revised April 2015
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PORT TOWNSEND PLANNING COMMISSION REGULAR SESSION AGENDA
CITY HALL COUNCIL CHAMBERS, 540 WATER STREET
Business Meeting 06:30 p.m.March 22, 2018
I. Call to Order
II.Roll Call
III.Acceptance of Agenda
IV.Approval of Minutes – March 8, 2018
030818 Draft Minutes
V.General Public Comment - None
VI. Old Business
A.Stormwater Management Plan
Action: None. Discussion only.
032218 Staff Memo
Attachment A - Open Space and Critical Areas
Attachment B - Open Space and Critical Areas Without Potential Drainage Ways
Attachment C - PTMC 19.05.090 CDC Amendments
Attachment D - Stormwater Consistency
Attachment E - SWManualCompareTM_20171207
Attachment F - SWManualCompare_Atch1a_2012-2005
Attachment G - SWManualCompare_Atch1b_2012-2014
PTMC 19.05
B. Critical Drainage Corridors and Frequently Flood Areas
Action: None. Discussion only.
VII. New Business - None
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VIII.Other Business - None
IX.Upcoming Meetings
Schedule
X.Communications
XI. Adjournment
Americans with Disabilities Act In compliance with the Americans with Disabilities Act, those requiring accommodation for this meeting should
notify the City Clerks Office at least 24 hours prior to the meeting at (360) 379-5083.
Hearing Assistance
Available
Capital Projects & Engineering
250 Madison, Suite 2R
Port Townsend, WA 98368
360-379-5096 Fax 360-385-7675
MEMORANDUM
TO: City Council
FROM: Samantha Harper, P.E., Assistant City Engineer
CC: Stormwater Management Plan File
RE: Summary of Stormwater Management Briefing at City Council Workshop on April 9,
2018
DATE: April 4, 2018
City staff and the stormwater consultant last presented the Stormwater Management Plan
(SWMP) to City Council on December 11, 2017. The presentation was a very broad overview of
the Stormwater Utility, which included:
Proposed Stormwater Utility Vision Statement;
Public Process to Date;
Existing System Assessment;
Stormwater Uniqueness of Port Townsend;
Proposed Tiering Map; and
SWMP Next Steps.
City staff plans to provide City Council with a progress update including a summary of the City
Council Ad-Hoc Committee for the SWMP meetings, Planning Commission and Parks,
Recreation and Tree Advisory Advisory Committee briefings.
City staff will present a formal presentation at the City Council workshop on Monday, April 9,
2018.
Stormwater Management
Plan Update
City Council Workshop
April 9, 2018
Goal of Tonight
•Provide update on status of the Stormwater Management Plan
•Increase familiarity with Stormwater Plan concepts
•Review current information
•Summarize meetings of Ad-hoc Committee on Stormwater
Management Plan
•Summarize Planning Commission Briefing
•Next Steps
Stormwater and Drainage Conditions in Port
Townsend are Unique
•No “streams”
•Port Townsend has closed basins with wetlands and discharge to the Sound
•DOE Stormwater Manual hydraulic modeling is for discharge to streams
•Low Rainfall
•Hydraulic modeling does not always reflect actual conditions
•Hard pan soils in much of the City
•Infiltration of Stormwater is often not feasible
•Historic Platting
•Stormwater controls are often implemented one lot at a time
Stormwater Management Plan Goals
•Assess Existing Drainage system
•Identify deficiencies
•Identify existing flooding problems
•Develop approaches to protect and improve the drainage system
•Identify drainage basin and roadway drainage network connectivity
•Use as a framework for planning future stormwater improvements.
•Develop a Capital Projects Plan
•Update standards and guidance for developers and builders
•Site development information and review materials, including low impact
development (LID) measures, infill, redevelopment, new site development, and
water quality retrofits
•Address Water quality protection approaches
Goals for the Roadway Drainage Network
Discovery Road – Road side Swale F Street – Curb and Gutter
Improved Roadway Drainage
Landes Street Hastings Avenue
Assessment of Stormwater System
Deficiencies and Needs
Sheridan Street – Swales needed 14th Street – shoulder maintenance
Assessment of Stormwater System Deficiencies and Needs – Local
Flooding
Sheridan Street Hancock Street & 31st Street
January 2018
City Council Adhoc Committee for Stormwater Management formed in
order to:
•Gain an understanding of the City’s Stormwater Utility;
•How the policies in the plan will guide regulations; and
•Receive feedback and input on topics pertained within the Stormwater
Management Plan
City Council Ad-Hoc Meeting No. 1
•Reviewed Existing
Conditions
•Stormwater Drainage
Basins
•Closed basins
•Receiving points for SW
Example Stormwater Capital Improvement
Projects
Stormwater Tied into Sewer
•Lawrence Street at Polk Street, Tyler Street and Taylor Street
Regional Stormwater System
•Rainier Street Regional Stormwater Facility
Improve Conveyance
•Roadside Drainage along Major Roads
•14 Street McPherson Street to Rosecrans Street
Localized Flooding
•Center Street – San Juan Ave. to Olympic Ave.
•Hancock Street and 32nd Street - at 31
st Street stormwater tie into sewer
City Council Ad-Hoc Meeting No. 2
•Critical Drainage
Corridors
Purple Roadway Inventory
Road Description Unit in Linear Feet
Road with curb and gutter and sidewalks 31,394
Road with more than 25-ft wide road – no sidewalk or curb 38,986
Road width 40-ft or less – yes sidewalk no curb 6,580
Road width 50-ft or less – no curb 12,381
Total Purple Roads 89,341
City Council Ad-Hoc Meeting No. 3
Existing Stormwater System
Stormwater Features Quantity
Catch Basins 1,468
Maintenance Holes 114
Storm Filters 4
Solid Pipe 25 miles
Perforated Pipe 0.9 miles
Swales 4.1 miles
Concrete Gutters 1.6 miles
Replacement of Storm Filters
Shoulder Pulling Operation
City Council Ad-Hoc Meeting No. 4
Proposed Site Development Regulation
Language
•Requirements for single lots, short plats and subdivisions and how the
applicant ties into the proposed Tiering Stormwater System
•If fees are assessed on new development it was proposed to be a
reduction system.
•Example:
1. Development with 100 percent infiltration and no discharge the applicant
would receive a 50-percent discount from paying into a roadway drainage
fund.
2. Development with reduced or no infiltration the applicant would receive a
0-percent discount from paying into a roadway drainage fund.
•Critical Drainage
Corridors
Outcome of the City Council Ad-Hoc
Committee
•Overarching Outcomes:
•Understanding of the stormwater utility from existing inventory, operations and
maintenance, capital projects needs, systems needs and the future direction of the
utility.
•Recommendations:
•CDC placement in PTMC Title 19.05 or PTMC 13.32, staff to present to Planning
Commission for their recommendation to City Council.
•If new stormwater development fees are assessed, the reduction method approach
was agreeable to the sub-committee members because it seemed logical,
understandable and fair.
•Staff recommended to keep the City Council Ad-Hoc Committee for Stormwater
Management together for the upcoming stormwater rate analysis study
Planning Commission Meeting
Maps provided at meeting
Summary of Planning Commission
•Critical Area Ordinance could move on to Planning Commission
Hearing.
•Planning Commission Briefing on April 26, 2018 for consistency
review between the Comprehensive Plan and Stormwater
Management Plan.
•Consistency Review Hearing on May 10, 2018.
Parks, Recreation and Tree Advisory Board
Meeting
Maps provided at meeting
Summary of Parks, Recreation and Tree
Advisory Board
•Will go back to the Parks, Recreation and Tree Advisory Committee’s
April meeting for consistency review between the Parks Plan and
Stormwater Management Plan.
Recommendation:
•Put an Education component in the Stormwater Management Plan.
Next Steps
Stormwater Management Plan
June 14, 2018
Page | 1
Memo
TO: Planning Commission
FROM: Samantha Harper, Assistant City Engineer
DATE: June 7, 2018 MEETING DATE: June 14, 2018
RE: Stormwater Management Plan Draft Review
Background: The City is drafting a Stormwater Management Plan - a functional plan which addresses
existing stormwater system conditions; the operation and maintenance of existing facilities and capacity
for adding new facilities; identifying capital project needs; and potential funding methods for financing
of capital and operational costs. Stormwater management is about drainage and flooding, as well as
water quality. The City has a range of soil types from hard pan to sandy soils which impact stormwater
solutions. The City intends to plan for surface water management as a whole – integrating a
preservation of water resources through natural systems approach where possible while protecting
environmental values and public health. The process will include comparison of 2005 and 2012 DOE
Stormwater Manual and recommended concurrent amendments to the City’s development
regulations/Engineering Design Standards to ensure public and private projects achieve the City’s
adopted level of service standard.
In addition to the functional plan, staff will need to update PTMC Chapter 13.32 Stormwater
Management Requirements.
On November 9, 2017, Planning Commission received a briefing including a proposed tiered map
identifying key areas of the City's stormwater system. Commissioners discussed issues related to
the Plan including addressing climate change and development costs and fees. Packets are
available via the City website at: http://cityofpt.us/video.html
In January and February of 2018, staff worked with the Council Sub-Committee.
The March 22, 2018 Planning Commission briefing meeting, staff discussed the relationship between
Critical Drainage Corridors (CDCs) and Drainage Ways and The Plan process to date. CDCs will remain
within the Critical Area Ordinance and public works staffs is still working on the language for Drainage
Ways, which will be regulated in Port Townsend Municipal Code Title 13.32. Staff will bring the draft
language to the Planning Commission once complete.
Stormwater Management Plan
June 14, 2018
Page | 2
June 14: The meeting on June 14th will be to review the highlights of the Draft Stormwater
Management Plan Chapter 1 -4. Staff and the consultant are still working on formatting, Chapters 5 – 6,
figures and tables.
Recommendation: No action is required of the Planning Commission at this time. Staff seeks questions
and feedback in preparation of the upcoming public hearings.
Next Steps:
? Meeting – to go over remaining Chapters prior to Hearing and the Drainage Way draft
language or go over it at the Hearing
June 28, 2018 Stormwater Management Plan Concurrency review - Public Hearing
Attachments
Draft Stormwater Management Plan Chapters 1 -4 with Appendix A and B
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PORT TOWNSEND PLANNING COMMISSION REGULAR SESSION AGENDA
CITY HALL COUNCIL CHAMBERS, 540 WATER STREET
Business Meeting 06:29 p.m.June 14, 2018
I. Call to Order
II.Roll Call
III.Acceptance of Agenda
IV.Approval of Minutes - April 26, 2018
042618
V.General Public Comment - None
VI.Old Business
A.Stormwater Management Plan
Action: None. Discussion only.
Staff Memo on Stormwater Management Plan 061418
DRAFT Stormwater Management Plan Chapter 1-4 with Appendices A and B June 2018
Meeting Handout - Kah Tai Lagoon Nature Park Wetland Development
B.Draft Rainier Street and Upper Sims Way Subarea Plan
Action: None. Discussion only.
PortTownsend-Subarea Plan-Draft 060418
Presentation on Draft Subarea Plan
C.Planning Commission Work Plan
Action: None. Discussion only.
Recommendations from Ad Hoc Committee on Housing 021318
Recommendations from Ad Hoc Committee on Housing 032618
Recommendation for Future Work Plans Revised
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VII.New Business
A.Letter to City Council Regarding Rainier Street Roundabout Signage
Action: Approve letter and direct staff to forward to City Council.
Draft Letter to Council - Rainier Street Promotion
VIII.Other Business - None
IX.Upcoming Meetings
Planning Commission Meetings Schedule
X.Communications - None
XI.Adjournment
Americans with Disabilities Act In compliance with the Americans with Disabilities Act, those requiring accommodation for this meeting should
notify the City Clerks Office at least 24 hours prior to the meeting at (360) 379-5083.
Hearing Assistance
Available
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CITY OF PORT TOWNSEND
MINUTES OF THE PLANNING COMMISSION REGULAR SESSION OF JUNE 14, 2018
CALL TO ORDER
The Port Townsend Planning Commission met in regular session on June 14, 2018, in the City
Council Chambers at 540 Water Street. Chair Paul Rice called the meeting to order at 6:30
p.m.
ROLL CALL
Commissioners present at roll call were Bob Doyle, Rick Jahnke, James Lagergren, Monica
MickHager, Aislinn Palmer, Paul Rice, and Lois Stanford.
Staff members present were Development Services Director Lance Bailey, Assistant City
Engineer Samantha Harper, Special Projects Temporary Employee Belinda Graham, and
Legal Assistant/Deputy Clerk Amber Long.
ACCEPTANCE OF AGENDA
Motion: Rick Jahnke moved to accept the agenda. Bob Doyle seconded.
Vote: motion carried unanimously, 7-0 by voice vote.
APPROVAL OF MINUTES - APRIL 26, 2018
Motion: James Lagergren moved to approve the minutes of April 26, 2018. Lois Stanford
seconded.
Vote: motion carried unanimously, 7-0 by voice vote.
GENERAL PUBLIC COMMENT - NONE
OLD BUSINESS
Stormwater Management Plan
Assistant City Engineer Samantha Harper informed the Commission that staff will postpone
the public hearing on the Stormwater Management Plan and will return in September or
October with a full draft of the Plan for discussion. She gave an overview of the first four
chapters of the draft Plan and discussed the work that still needs to be done.
Public comment: Debbie Jahnke read a definition for "sensitivity analysis." She distributed
the Admiralty Audubon Society's proposed plan for wetland development at Kah Tai Lagoon
and requested that the Commission recommend including the wetland in the Stormwater
Management Plan.
Draft Rainier Street and Upper Sims Way Subarea Plan
Special Projects Temporary Employee Belinda Graham presented on the background,
vision, guiding principles, and next steps for the subarea plan. By agreement,
the Commissioners discussed the first half of the plan page by page, asking questions of
staff and providing suggested revisions to text and photographs. Staff plans to have the
Executive Summary available by the next meeting.
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Planning Commission Work Plan
Development Services Director Lance Bailey discussed the DSD/Planning Commission
work plan document from December 2016 and the housing-related items that have been
tasked to Planning Commission by City Council. After discussion, the Commission generally
agreed to start with a review of the following:
1. SEPA categorical exemptions;
2. ADU regulations; 3. Daylight plane requirements; and
4. Cottage housing.
NEW BUSINESS
Letter to City Council Regarding Rainier Street Roundabout Signage
Chair Rice noted that he will change "Rainier Street sub-area" in the letter to "Rainier Street
and Upper Sims Way sub-area" to match the name of the Plan.
Motion: Aislinn Palmer moved to approve sending the letter with the change noted. James
Lagergren seconded.
Vote: motion carried unanimously, 7-0 by voice vote.
OTHER BUSINESS - NONE
UPCOMING MEETINGS
The next meeting is scheduled for June 28th, when the Planning Commission will continue its
review of the Rainier Street and Upper Sims Way Subarea Plan.
COMMUNICATIONS - NONE
ADJOURNMENT
There being no further business, the meeting was adjourned at 9:40 p.m.
Attest:
Planning Commission Chair
City Clerk's Office
Appendix C
FEMA Flood Mapping
Appendix D
Modeling Analysis
APPENDIX D MODELING ANALYSIS
The detailed modeling analysis is available at the Port Townsend City offices for review upon request.
Appendix E
Roadway Inventory
Road From To Length
Roadway
Width
Sidewalk
Width
Gravel
Path
Gravel
Shoulder Total
ROW
Width
Curb
Length
Swale
Length
Left Right Left Right Left Right Left Right
Cook Ave. Elmira St.Peary Ave.3,074 21 21 80
Cook Ave. Peary Ave.Emerald St.550 21 21 80 X 225
Cook Ave. Emerald St.53rd St.1,236 21 21 80
53rd St. Cook Ave.49th St.1,265 24 24 60
49th St. 53rd St.Hendricks St.1,270 21 21 60
49th St. Hendricks St.Wilson St.1,115 21 21 30
49th St. Wilson St.Erin St.300 21 21 40
49th St. Erin St.Jackman St.480 22 22 60
49th St. Jackman St.Pettygrove St.1,000 28 28 60
49th St. Pettygrove St.San Juan Ave.800 23 23 50
San Juan Ave. 49th St.47th St.455 25 25 50 X 227
San Juan Ave. 47th St.St. Mary Cemetery North 1,106 30 6 36 60 X 553
San Juan Ave. St. Mary Cemetery North St. Mary Cemetery South 465 32 6 38 60 X 233
San Juan Ave. St. Mary Cemetery South Center St.700 44 10 54 85 X X 700
San Juan Ave. Center St.Cedar St.162 32 10 44 85 X 81 X 81
San Juan Ave. Cedar St.37th St.335 33 5 38 100 X X 335
San Juan Ave. 37th St.Tremont St.208 43 5 48 100 X 104 X 104
San Juan Ave. Tremont St.35th St.247 32 5 37 100 X X 247
San Juan Ave. 35th St.32nd St.520 33 10 43 60 X X 520
San Juan Ave. 32nd St.F St.720 33 5 38 80 X 360 X 360
San Juan Ave. F St.716' South of F St.716 32 6 38 X X 716
San Juan Ave. 716' South of F St. 24th St.890 32 6 38 X 445 X 445
San Juan Ave. 24th St.22nd St.533 32 6 38 X X 533
San Juan Ave. 22nd St.19th St.820 32 6 38 X 410 X 410
19th St. Sheridan St.Discovery Rd.440 50 6 56 66 X X 440
19th St. Discovery Rd.San Juan Ave.2,765 50 50 66 X X 2765
Blaine St. San Juan Ave.Walker St.1,535 52 6 58 73 X X 1535
Discovery Rd. City Limits Spring St.1,340 21 21 60
Discovery Rd. Spring St.6th St.675 21 21 80
Discovery Rd. 6th St.Howard St.2,006 22 5 26 60
Discovery Rd.Howard St.Rosecrans St.2,330 23 23 60
Discovery Rd. Rosecrans St.McClellan St.300 23 6 29 60
Discovery Rd. McClellan St.Grant St.1,157 23 6 29 80 X 579
Discovery Rd. Grant St.Sheridan St.265 28 11 39 66 X 133
Discovery Rd. 19th St.20th St.455 26 6 32 60 X 227
Discovery Rd. 20th St.166' SW of 22nd St.665 26 6 32 60
Discovery Rd. 166' SW of 22nd St. 24th St.838 26 6 32 60 X 419
Discovery Rd. 24th St.Hastings Ave.998 26 6 32 60 X X 998
Discovery Rd.Hastings Ave.San Juan Ave.1,160 31 6 37 60 X X 1160
F St.San Juan Ave.Blaine St.3,885 31 10 41 60 X X 3385
Walker St. Lawrence St.Garfield St.507 35 5 40 73 X X 507
Walker St. Garfield St.Blaine St.381 35 5 40 73 X 190 X 190
Cherry St. Blaine St.A St.794 26 8 34 73 X 397
Cherry St. A St.E St.1,031 25 25 60
Cherry St. E St.F St.268 29 6 35 60
Cherry St. F St.W St. / Redwood St.4,242 26 26 60
W St. Spruce St.Redwood St.775 22 22 60 X 388 X
Walnut St. W St.Jackson St.2,000 20 20 60
Jackson St. Bryan St.Reed St.332 22 22 60
Jackson St. Reed St.Root St.265 30 30 60 X 133 X 133
Jackson St. Root St.Foster St.253 30 30 60 X 126 X
Jackson St. Foster St.McKinley St.256 30 30 60 XX
Jackson St. McKinley St.Monroe St.941 30 30 60 X 470 X
Monroe St. Roosevelt St.Blaine St.395 31 31 73 X X 395
Monroe St. Blaine St.Lawrence St.881 36 5 41 73 X X 881
Monroe St. Lawrence St.Clay St.278 36 10 46 73 X X 278
Monroe St. Clay St.Jefferson St.596 36 5 41 73 X X 596
Monroe St.Jefferson St.Washington St.303 41 11 52 73 X X 303
Monroe St.Washington St.Water St.282 47 20 67 73 X X 282
Blaine St.Tyler St.Taylor St.284 29 6 35 73 X 142
Blaine St.Taylor St.Adams St.294 21 5 25 73 X X
Blaine St.Adams St.Monroe St.879 22 22 73 X X
Hastings Ave. City Limits Ivy St.685 21 21 60 X 343
Hastings Ave.Ivy St.Howard St.2,000 21 21 100
Hastings Ave.Howard St.Eddy St.255 22 22 108 X 128
Hastings Ave.Eddy St.Cliff St.261 21 7 28 108
Hastings Ave.Cliff St.Thomas St.800 21 5 26 108
Hastings Ave.Thomas St.Sheridan St.2,178 21 5 26 100 X 1089
Hastings Ave.Sheridan St.Discovery Rd.2,274 23 6 29 100 X 1137
Umatilla Ave.Sherman St.31st St.1,963 20 20 60
Umatilla Ave.31st St.Holcomb St 430 20 20 60 X 215
Umatilla Ave.Holcomb St.San Juan Ave.1,947 20 20 60
Rainier St.SR 20 Discovery Rd.1,960 41 19 60 60 X X 1960
McPherson St.SR 20 6th St.342 35 6 41 66 X 171
McPherson St.6th St.7th St.250 21 6 27 66
McPherson St.7th St.Discovery Rd.2,366 21 21 66
Sheridan St.SR 20 7th St.775 40 6 46 66 X 387
Sheridan St.7th St.8th St.265 42 12 54 66 X X 265
Sheridan St.8th St.10th St.536 49 12 61 66 X X 536
Sheridan St.10th St.136' North of 10th St. 136 48 6 54 66 X 68 X 68
Sheridan St.136' North of 10th St. 14th St.934 44 44 66 X 197
Sheridan St.14th St.15th St.262 46 46 66 X X 262
Sheridan St.15th St.19th St.1,064 47 12 59 66 X X 1064
Sheridan St.19th St.Hastings Ave.2,340 22 5 27 66 X X 265 X 1,520
Kearney St.Blaine St.Lawrence St.889 29 6 35 73 X X 889
Kearney St.Lawrence St.Franklin St.614 29 6 35 73 X 307 X 307
Kearney St.Franklin St.Jefferson St.253 48 12 60 73 X X 253
Kearney St.Jefferson St.SR 20 136 36 12 48 73 X 68 X 68
Lawrence St.Kearney St.Scott St.576 48 48 73 X X 576
Lawrence St.Scott St.Walker St.300 48 10 58 73 X X 300
Lawrence St.Walker St.Benton St.875 36 5 41 73 X
Lawrence St.Benton St.VanBuren St.581 42 10 52 73 X
Lawrence St.VanBuren St.Polk St.884 50 19 69 73 X X 884
Lawrence St.Polk St.Taylor St.585 55 18 73 73 X X 585
Lawrence St.Taylor St.Monroe St.1,176 48 10 58 73 X X 1176
14th Street McPherson Street 4,290 19 19 66
SR 20 City Limits Spring St.910 38 38 77
SR 20 Spring St.Winery Driveway 937 38 38 100 X X 937
SR 20 Winery Driveway Rainier St.536 48 6 54 100 X X 536
SR 20 Rainier St.Thomas St.1,512 44 12 56 100 X X 1512
SR 20 Thomas St.Logan St.250 39 12 51 100 X X 250
SR 20 Logan St.Ravine 493 38 38 100 X X 493
SR 20 Ravine Hancock St.336 50 50 100 X X 336
SR 20 Hancock St.Sherman St.281 50 50 100 X X 281
SR 20 Sherman St.Grant St.554 55 12 67 100 X X 554
SR 20 Grant St.Wilson St.776 50 50 100 X X 776
SR 20 Wilson St.10th St.1,942 42 42 100 X 971
SR 20 10th St.Safeway Entrance 280 45 45 100 X 140
SR 20 Safeway Entrance Haines Place 381 73 6 79 100 X 190
SR 20 Haines Place 12th St.704 62 62 100
SR 20 12th St.Thayer St.1,265 50 8 58 100
SR 20 Thayer St.Decatur St.321 42 14 56 100
SR 20 Decatur St.Kearney St.307 52 6 58 100 X 153
SR 20 Kearney St.Gaines St.319 62 5 67 100 X X 319
SR 20 Gaines St.Water/Walker 596 53 6 59 100 X X 593
SR 20 Water/Walker VanBuren St.1,362 39 6 45 73 X X 1362
SR 20 VanBuren St.Ferry Terminal 345 51 12 63 73 X X 345
SR 20 Ferry Terminal Polk St.655 55 18 73 73 X X 655
SR 20 Polk St.Monroe St.1,760 49 24 73 73 X X 1760
Fir St.B St.F St.1,040 31 5 36 60 X 520
109,062 38,780 13,132
TOTALS miles of road 20.656
feet of road with curbs on
both sides and sidewalks 31,457
percent of total 28.8%
bioretention or
swale and
conveyance
feet of road with <25' road
and >60'rw and no
sidewalks or curbs 38,986
35.7%
bioretention
about 40' or less of
pavement, at least 30 feet
of unpaved rw, can have
sidewalk, no curb 6,580
6.0%
some
treatment
possible
about 50' or less pavement,
at least 20 feet of unpaved
rw, no curb 12,381
11.4%
filter boxes
curb on both sides, at least
20 feet of extra rw 2277
2.09%
Curb Concrete DitchSwaleGrass
Appendix F
Small‐Site Stormwater
Management Guide
DRAFT
DRAFT
Development Services Department
250 Madison Street, Suite 3
Port Townsend WA 98368
Phone: 360-379-5095
Fax: 360-344-4619
www.cityofpt.us
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[DRAFT]Street & Utility Development Permit Application
MIP No.SDP No.BLD No.
Applicant:Phone:
Mailing Address:Fax:
City, State, Zip:E-mail:
Property Owner's Name(s):Phone:
Mailing Address:
City, State, Zip:E-mail:
Authorized Representative:Phone:
Address:E-mail:
Property Site Street (and address if assigned):
Zoning District:Parcel #:
Legal Description: Addition:Block:Lot(s):
Water/Sewer/Street Contractor
Mailing Address:
Phone:Fax:Cell Phone:
State License #:Expiration:City Business Lic.#:Expiration:
Estimated value of utility and/or street construction: $
Describe work to be conducted under this permit and purpose:
Describe earth work such as landscaping, clearing, grading:
How many acre(s) will be disturbed?Where will the overflow discharge?
Is Latecomer Proposed?For what Utility?
Will trees or vegetation be removed in the right-of-way?o Yes o No If yes, Describe & show on site plan.
What is the amount of impervious surface on the property? ___________sq. ft. & _______% of the property.
I hereby certify that the information provided is correct, that I am either the owner or authorized to act on behalf of the owner and that
all the activities associated with this permit will be in accordance with State Laws and the Port Townsend Municipal Code.
Signature of Owner or Authorized Representative Date
______________________________________________
Print Name:
DRAFT
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Street & Utility Development Permit Application
Infrastructure
The application is not complete without all the items on this checklist complete.
(If not applicable, mark “N/A”)
*All boxes filled in on the front of this application
*City of Port Townsend “Lot Coverage and Impervious Surfaces Worksheet for Applicants”
*Soil percolation test results, based on Port Townsend “Guide to Residential Rainwater
Management”
*Vicinity Map
*Two sets of 8 ½ X 11 drawings showing work proposed under this permit. All dimensions must be
shown - width, length, depth, etc. Include the following drawings:
*Site Plan:
*All lot lines, block number, and lot numbers
*Lot dimensions
*Slopes/Contours (existing and proposed)
*Area (acres or square feet) and volume (cubic yards) of cut and fill
*Outside dimensions of all buildings, including eaves
*Dimensions of impervious (hard) surfaces (existing and proposed 1)
*Edge of street travel way
*Driveway from edge of travel way (dimensions & type of surface material)
*Adjoining street names
*All trees/vegetation proposed for removal in the right-of-way
*Existing or proposed easements
*Existing or proposed water and sewer mains
*Proposed connections to existing utilities (sewer, water, power 2)
*Profile of lots
1 If creating new impervious surfaces, provide square footage of total impervious and percentage of the property using the City of
Port Townsend “Lot Coverage and Impervious Surfaces Worksheet for Applicants”
2 The Public Utility District #1 (PUD #1) provides Port Townsend electrical power; be sure to contact PUD #1 (385-5800) to develop
plans for the electrical service connections for your property. Provide a site plan that clearly shows the power route to your project.
DRAFT
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*Drainage Plan:
*Have any known wetlands or their buffers been identified on the property?
¨ No oYes (If yes, you may be required to include a wetland report)
*Are there any steep slopes (greater than 15%) on the property?
¨ No oYes (If yes, you may be required to include a geotechnical report)
*North Arrow
*Slopes/Contours (existing and proposed) and flow direction arrows
*Dimensions of impervious (hard) surfaces (existing and proposed1)
*Location(s) where rainwater flows off of the property (existing and proposed)
*Location(s) where rainwater discharges to the City street-side drainage system (catch
basin inlet, swale, ditch, culvert/pipe, etc.)
*Direction of flow of City street-side drainage system
*Dimensions of the on-site stormwater facility (rain garden, dry-well, curtain drain, etc.)
*Location where site flow will enter proposed on-site stormwater facility
*Location where water will overflow from on-site stormwater facility and flow to City street-
side drainage system in case of heavy rains
*Temporary Erosion and Sediment Control Plan:
*North Arrow
*Slopes/Contours (existing and proposed) and flow direction arrows
*Location(s) where rainwater flows off of the property (existing and proposed)
*Location(s) where rainwater discharges to the City street-side drainage system (catch
basin inlet, swale, ditch, culvert/pipe, etc.)
*Direction of flow of City street-side drainage system
*Location(s) of temporary erosion and sediment control management features, based on
the Port Townsend Engineering Design Standards Chapter 5.
*If extending water or sewer mains or constructing a new street, 3 sets of plans prepared by a
licensed civil engineer must be submitted with this application.
*Did the applicant complete the process of a Technical Conference in the prior 12 months? If yes,
a credit may be available for a portion of the SDP/MIP permit fee.
DRAFT
Development ServicesDepartment
250MadisonStreet, Suite3
PortTownsendWA98368
Phone: 360-379-5095
Fax: 360-344-4619
www.cityofpt.us
LotCoverageandImpervious Surfaces - WorksheetsforApplicants
LotCoverageandImperviousSurfaceCalculations aresimilar, butnotthesame. Thisworksheet is
designedtohelpyouclarifythedifferenceandhelpyoudeterminethecorrectnumberstouseonour
applications.
LOTCOVERAGE = STRUCTURAL FOOTPRINTS
Lotcoverageisdefinedas “thetotalground coverageofallbuildingsorstructuresonasitemeasured
fromtheoutsideofexteriorwallsorsupportingmembers, includingaccessorybuildingsorstructures,
notbut toincludeat-gradeoff-streetparkinglots, deckareas, terraces, swimming pools, pooldeck
areas, walkways, roadwaysordriveways” (PortTownsendMunicipalCode17.08.040).
Calculate theTotalLotCoverage oftheProposedStructures:
Allbuildingfootprints (insquarefeet) including:
Existing Proposed TOTAL
House
Garage
CoveredPorch
AccessoryDwellingUnit
Deckover30” AboveGround
Shed
ExteriorStairs
Other:
TOTALLotCoverageofstructures: squarefeet
Calculate theLotCoveragePercentage:
DividetheTotalLotCoverage (above) ___________squarefeet
bytheSquareFootageoftheProperty: squarefeet
Anddivideby100toequalthe
TOTALpercentageoflotcoverage: %.
DRAFT
MPERVIOUSSURFACES = STRUCTURALFOOTPRINTS PLUSIMPERVIOUS SURFACES. I
Calculate theTotalImperviousSurfaceoftheProposedProject:
HouseRoofarea: squarefeet
GarageRoofarea: squarefeet
CoveredPorch Roofarea: squarefeet
OtherStructureRoofarea: squarefeet
Decksandpatiosandotherstructuresover30” inHeightthatdonotallow
rainwater betweentheslats/surface squarefeet
Driveway, Sidewalk & gravel/compactedareas: squarefeet
TOTALImpervious SurfaceArea: squarefeet
CalculatetheImpervious SurfacePercentage:
DividetheTotalImperviousSurfaceArea (above) _________ squarefeet
BytheSquareFootageoftheProperty squarefeet
Anddivideby100toequalthe
TOTALpercentageofimpervious surface %.
Impervioussurfaces” meansareasorsurfaces thatcannotbeeasilypenetratedbyrainor
surfacewaterrunoff. Theseareasincludestructuresandroofprojections, imperviousdecks,
roads, driveways, andsurfaceswhichsubstantially reduceandalterthenaturalfiltration
characteristicsofthesoil.” PortTownsendMunicipalCode19.05.020)
Ifyourbuildingproposalincreasestheareaofimpervioussurfaces, itmayresultin
stormwaterimpacts. RefertotheCity’sEngineeringDesignStandards: www.cityofpt.usunder “City
Plans”.Stormwatermethods canincludeinfiltrationtrenches, drywells, andraingardens.
Downspoutsthatflowintosplashblockscanonlybeusedforpropertieswherethereisaminimumof
50feetofavegetatedpathbetweenthesplashblocksandtheedgeoftheproperty.
Iftheimpervioussurfaceisover40%, anengineeredstormwaterdrainageplanisrequired.
YouwillneedtoretainaCivilEngineertoprepareandstampdrawings tobesubmitted withthepublic
workspermit. Drawings mustincludespecifications ofon-sitestormwatermethods.
Iftheimpervioussurfaceisunder 40%, youmayconductyourownperctestandsubmitan
on-sitestormwater drainageplanwithyourapplication forreviewandapprovalbycitystaff.
Askstaffforthehandoutforguidanceonconducting aperctest, orgoonlinetowww.cityofpt.us tothe
City’sEngineering DesignStandards, Chapter4Section5DrainagePlan, ContentsandStandard
ProceduresforMediumImpact Projects.
DRAFT
DRAFT
o Topography (steep slopes, flow direction)o Soil (shovel test, hand texture, perc test)
o Vegetation (mature plants/trees, invasives)o Water (direction over hard surfaces, standing water, natural springs)
o Sensitive Areas (wetlands, setbacks, tree roots)o Off-site connections (flow to City street drain, neighbor's property)
50 FEET
Scale: 1 square = 5 ft x 5 ft
DRAINAGE SKETCH
DRAFT
DRAFT
DRAFT
13.32 STORMWATER MANAGEMENT REQUIREMENTS
13.32.010 Minimum requirements for drainage improvements.
A.All developments shall comply with the Department of Ecology’s February 2005 Stormwater
Management Manual for Western Washington (“2005 SWMM -WW”), except f or the following:
Section 2.6 – Optional guidance relating to financial liability and off-site analysis and mitigation, city
engineering design standards, city stormwater master plan, and adopted drainage basin plans for all
clearing and grading activities, for erosion control during construction , and for permanent drainage
system improvements.; except developments shall comply with the following City requirements,
which supersede the 2005 SWMMWW:
1.Section 2.6 – Optional guidance relating to financial liability and off-site analysis and mitigation
2.Engineering Design Standards
3.Stormwater Master Plan, and
1.4.Adopted drainage basin plans
A.B.Surface water entering the subject property shall be received at the naturally occurring locations
and surface water exiting the subject property shall be discharged at the natural locations with
adequate energy dissipaters within the subject property to minimize downstream damage and with
no diversion at any of these points.
B.C.All developments shall do the necessaryconduct analysis and install the necessary mitigations to
ensure that stormwater exiting their property is discharged at a safe location which will not impact
other property owners.
C.D.All structures shall be built such that finished floor elevations are in conformance with the
International Building Code as adopted or hereafter amended.
D.E.Building Drainage plans shall clearly show locations of drainage system and stormwater controls
within property limits and any off-site drainage improvements.
E.F.Considerations for the discharge of water off-site include but are not limited to the following:
1.Sufficient capacity of downstream facilities under design conditions;
2.Maintenance of the integrity of the receiving waters;
3.Possibility of adverse effects of retention/detention;
4.Utility of regional retention/detention facilities;
5.Capability of maintenance of the system; and 6. Structural integrity of abutting foundations and
structures.
F.G.All developers not providing permanent stormwater control facilities will be required to sign a no-
protest agreement for future participation in a stormwater-related LID. (Ord. 2915 § 1, 2006; Ord.
2867 § 2, 2004; Ord. 2579 § 1, 1997).
13.32.020 Drainage plan – Submission.
A.All developers applying for any of the following permits and/or approvals may be required to submit
for approval a drainage plan with their application and/or request:
1.Grading permit;
2.Street development permit;
3.Substantial development permit required under Chapter 90.58 RCW (Shoreline Management
Act);
4.Subdivision approval;
5.Short subdivision approval;
6.Commercial, industrial or multifamily site plan approval;
7.Rezones;
8.Conditional use permits;
9.Planned unit developments;
10.Building permits, where the permit either (a) authorizes or is for new construction totaling 40
percent or more of developmental coverage within the subject property; or (b) authorizes or is
for new construction which, together with pre-existing developmental coverage, would result in
40 percent or more developmental coverage within the property or (c) is for development in an
environmentally sensitive area or which has the potential to impact an environmentally
sensitive area;
11.Building permits, where the new development does not involve a change in impervious
coverage of a site but where one of the following conditions exist:
a.The stormwater from the existing development is connected to the sanitary sewer system.
b.The drainage system serving the existing development is inadequate to prevent impacts to
neighboring properties.
c.Water quality issues are a concern either from the existing development or from the
proposed development.
B.In addition, a drainage plan may be required for creation of impervious area, not covered by a
permit, which exceeds either:
1.Five thousand square feet; or
2.Forty percent developmental coverage within the subject property.
C. Construction work done under any of the above permits or applications shall not begin until such
time as final approval of the drainage plan is obtained in accordance with PTMC 13.32.050.
D.The same plan submitted during one permit/approval process may be subsequently submitted with
further required applications. The plan shall be supplemented with such additional information that
is requested by the public works department or required by the provisions of the engineering design
standards manual and/or DOE Stormwater Management Manual for the Puget Sound Basin.
E.Temporary erosion and sediment control measures may be required under Chapter 5 of the
engineering design standards at the discretion of the director for:
1.Site preparation and/or construction of any development; or
2.Creation of impervious area which exceeds either:
a.Five thousand square feet; or
b.Forty percent of the subject property. (Ord. 2687 § 1, 1999; Ord. 2579 § 1, 1997; Ord. 2126 §
1, 1988; Ord. 1957 § 3, 1983).
13.32.030 Drainage plan – Contents.
All persons applying for any of the permits and/or approvals contained in PTMC 13.32.020 shall provide
a drainage plan for surface and pertinent subsurface water flows entering, flowing within, and leaving
the subject property both during and after construction. The detailed form and contents of the drainage
plan shall be described in procedures established by the public works department, or in the engineering
design standards manual and/or DOE Stormwater Management Manual for the Puget Sound Basin. The
engineering design standards manual, and the DOE Manual, will set forth the manner of presenting the
required information which may include but is not limited to the following:
A.Background computations for sizing drainage facilities:
1.Depiction of the drainage area on a topographical map of approved scale and contour interval,
with acreage of the site, development, and developmental coverage indicated;
2.Indications of the peak discharge and volume of surface water currently entering and leaving the
subject property due to the design storm;
3.Indication of the peak discharge and volume of runoff which will be generated due to the design
storm within the subject property if the development or proposed activity is allowed to proceed;
and
4.Determination of the peak discharge and volume of water that will be generated by the design
storm at various points on the subject property;
B.Proposed measures for handling the computed runoff at the detail level specified in the engineering
design standards manual and/or DOE Stormwater Management Manual for the Puget Sound Basin:
1.The design storm peak discharge from the subject property may not be increased by the
proposed development; and
2.Retention/detention facilities must be provided in order to maintain surface water discharge
rates at or below the existing design storm peak discharge; and
C.Proposed Measures for Controlling Runoff During Construction. The requirements of this section
may be modified at the discretion of the city public works department in special cases requiring
more information. (Ord. 2579 § 1, 1997; Ord. 2444 § 2, 1995; Ord. 1957 § 4, 1983).
13.32.040 Development in environmentally sensitive areas or impacting ESAs.
Development in environmentally sensitive areas (ESAs) or development which has the potential to
impact ESAs must meet the requirements of Chapter 19.05 PTMC or other requirements as determined
necessary for the protection of the ESAs as determined by the public works director. (Ord. 2579 § 1,
1997; Ord. 1957 § 6, 1983).
13.32.050 Review and approval of the plan.
All storm drainage plans prepared in connection with any of the permits and/or approvals listed in PTMC
13.32.020 shall be submitted for review by and approval of the public works department in accordance
with the procedures established in the engineering design standards manual and/or DOE Stormwater
Management Manual for the Puget Sound Basin. (Ord. 2579 § 1, 1997; Ord. 2444 § 3, 1995; Ord. 1957 §
7, 1983).
13.32.060 Establishment of regional facilities.
In the event that public benefits would accrue due to modification of the drainage plan for the subject
property to better implement the recommendations of the comprehensive drainage plan, the public
works department may recommend that the city should assume responsibility for the further design,
construction, operation and maintenance of drainage facilities on the subject property. Such decision
shall be made concurrently with review and approval of the plan as specified in PTMC 13.32.050. In the
event that the city decides to assume responsibility for design, construction, operation, and
maintenance of the facilities, the developer will be required to contribute a pro rata share to the
construction cost of the facilities. The developer may be required to supply additional information at the
request of the public works department to aid in the determination by the city. Guidelines for
implementing this section will be defined in the engineering design standards manual and/or DOE
Stormwater Management Manual for the Puget Sound Basin. (Ord. 2579 § 1, 1997; Ord. 1957 § 8, 1983).
13.32.070 Applicability to government entities.
A.All municipal corporations and governmental entities shall be required to submit a drainage plan
and comply with the terms of this chapter when developing and/or improving land including, but
not limited to, road building and widening within the areas of the city.
B.It is recognized that many other city, county, state and federal permit conditions may apply to the
proposed action and that compliance with the provisions of this chapter does not constitute
compliance with such other requirements. (Ord. 2579 § 1, 1997; Ord. 1957 § 12, 1983).
13.32.080 Protection of public/private rights.
Implementation of any provision of this chapter shall not cause nor be construed as an infringement of
the rights of individuals, municipalities, or corporations other than the developer seeking a permit or
approval as described in PTMC 13.32.030. (Ord. 2579 § 1, 1997; Ord. 1957 § 14, 1983).
19.05 - CRITICAL AREAS
19.05.060 Performance standards for development – Mitigation, on-site and off-site, density,
minimum lot size, subdivisions, preferred construction practices, impervious surface standards,
stormwater plans, mitigation plans.
D.The performance standards below apply to any development and to all short plats, subdivisions and
lot line revisions proposed for sites wholly or partially within confirmed critical areas or their buffers
in Port Townsend. These standards are general development practices to minimize problems related
to water quality, stormwater and erosion control, and the placement and construction of
development in the city’s critical areas. In addition to the following general performance standards,
if a site contains a critical area or its buffer, such as a steep slope or a wetland, the applicable set(s)
of regulations outlined in the following sections of this chapter shall also apply.
5.Stormwater and Erosion Control.
a.Stormwater Management Plan.
All development subject to the provisions of this chapter shall comply with the 2005
Department of Ecology Stormwater Management Manual for Western Washington (SWMM-
WW (2005)), city engineering design standards manual, city stormwater master plan, and
adopted drainage basin plans.
i.Stormwater management plans shall be consistent with the standards contained in
the city’s EDS manual and the SWMM-WW (2005), and must be developed on a site-
specific basis and must contain a technical report that identifies existing or
predicted problems and sets forth solutions to each. Off-site measures may be
required to correct existing on-site problems or to prevent new problems from
occurring. Surface water discharge from the site shall not be greater than historic or
predevelopment rates.
ii.If the development does not meet water quality standards established by law or
administrative rules, the city may suspend further development work on the site
until such standards are met.
b.Erosion control practices must be detailed using best management practices for
situation/filtration devices to control surface runoff during construction, and the 2005
Department of Ecology Stormwater Management Manual for Western Washington (SWMM-
WW (2005)).
i.Applicants shall indicate erosion control measures on the site construction plan or
stormwater control management plan, as appropriate for the project.
ii.These requirements shall be in place following the preconstruction meeting outlined
in PTMC 19.05.040(D)(1)(i) and shall be reviewed and approved prior to clearing and
grading.
c.Applicants are also encouraged to consult the recommendations set forth in Chapter 5 of
the Low Impact Development Technical Guidance Manual for the Puget Sound (2004) for
guidance concerning the protection of native soils and vegetation, and retention of
hydrologic function, during clearing and grading for development proposals.
Appendix G
Capital Projects Worksheets
No. 2
No. 3
No. 4
No. 5
No. 7
No. 6
Option B
Option A
Regional Stormwater Facility will
provide stormwater detention for approximately
33 acres of commercial properties and public
rights-of- way along the Rainier Street corridor
from Discovery Road to the south side of Sims
Way (SR 20). The facility will be a constructed
pond, located just outside the city limits and ad-
jacent to Mill Road, that will be connected by
pipes from the overflow of an existing
stormwater pond on Rainier Street, south of SR
20.
$573,198.30
Overflow project is to pipe the ex-
isting overflow pipe to the bottom of the ravine
within the 3rd Street and Rosecrans Street
rights-of-way in order to stop the erosion of the
existing bank..
The budgeted amount in the
2019 budget is $30,000. This project currently
does not have a more detailed project estimate
at this time.
Port Townsend CIP Area Summary
Project No. Project Title Estimated Cost Description
No. 1 16th Street - Sheridan Street to Landes Street $292,600 Closed conveyance system
No. 2 12th Street ROW, Logan Street, and 14th street $840,700 Bioswales and closed conveyance system
No. 3 Center Street - San Juan Avenue to Olympic Avenue $513,800 Closed conveyance system
No. 4 Hancock Street and 32nd Street $234,360 Ditch and culvert
No. 5 Lawrence Street at Intersections of Polk Street, Taylor Street, and Tyler Street $1,409,940 Closed conveyance system
No. 6 Regional Stormwater Facility for Rainier Street Commercial Corridor $573,198 Regional Stormwater Facility
No. 7 Logan Street Pond Overflow -Closed conveyance system
Total Cost $3,864,598
Citywide
Project No. Project Title Estimated Cost
TOTAL CIP COST: $3,864,598
CITY OF PORT TOWNSEND
Port Townsend Stormwater Management Plan
Preliminary Opinion of Probable Cost
Capital Project No. 1
Project Name:16th Street - Sheridan Street to Landes Street
Prepared By:Tyler Nabours Checked By:C. Buitrago
Project Description:
Item No.
Estimated
Quantity Unit Description Unit Cost Amount
1 1 LS Mobilization $19,200 $19,200
2 1 LS Traffic Control $2,500 $2,500
3 1 LS Erosion/Sedimentation Control $2,500 $2,500
4 690 LF Storm Sewer Pipe - 12 Inch $160 $110,400
5 40 LF Pavement Repair $50 $2,000
6 1 EA Catch Basin Type I $3,960 $3,960
7 1 EA Catch Basin Type II, 48" Diam.$6,690 $6,690
8
9
10
Construction Subtotal (2018 Dollars) = $147,250
Inflation from 2018 to 2019 2.10% $3,092
Construction Subtotal (2018 Dollars) = $150,342
Contingency 30.0% $45,103
Sales Tax 9.0% $13,531
Planning Level Construction Cost = $209,000
Environmental Permitting and Documentation 5.0% $10,450
Administration 5.0% $10,450
Preliminary Engineering, PS&E Engineering and Construction Management 30.0% $62,700
2018 TOTAL = $292,600
ASSUMPTIONS:
Mobilization equals approximately 15-percent of Subtotal.
Traffic Control equals approximately 2-percent of Subtotal.
Erosion/Sedimentation Control equals approximately 2-percent of Subtotal ($1,000 min).
Pavement Restoration includes the cost of HMA (4-inch), CSTC (2-inch), and CSBC (6-inch).
Cost of pipe installation includes structure excavation and shoring.
Cost of catch basin installation includes structure excavation and shoring.
Between Gise Street and Landes Street, the 16th Street Right-of-way exists in an undeveloped condition. In existing conditions, stormwater from Sheridan
Street, 14th Street, and 16th Street is conveyed through a closed system to an outfall located at 16th Street and Gise Street, where severe erosion has
been created. Propose to continue conveyance of stormwater through storm sewer pipe east through the 16th Street ROW, and tie-into existing closed
system near 16th Street and Hill Street. Proposal includes a Type I catch basin upstream and replacement of a Type II - 48" catch basin on downstream
end.
CITY OF PORT TOWNSEND
Port Townsend Stormwater Management Plan
Preliminary Opinion of Probable Cost
Capital Project No. 2
Project Name:12th Street ROW, Logan Street, and 14th street
Prepared By:Tyler Nabours Checked By:C. Buitrago
Project Description:
Item No.
Estimated
Quantity Unit Description Unit Cost Amount
1 1 LS Mobilization $55,200 $55,200
2 1 LS Traffic Control $17,200 $17,200
3 1 LS Erosion/Sedimentation Control $6,900 $6,900
4 1067 LF Storm Sewer Pipe - 12 Inch $160 $170,720
5 1116 LF Bioswale Grading $90 $100,440
6 10 EA Catch Basin Type I $3,960 $39,600
7 661 LF Pavement Repair $50 $33,050
8
9
10
Construction Subtotal (2018 Dollars) = $423,110
Inflation from 2018 to 2019 2.10% $8,885
Construction Subtotal (2019 Dollars) = $431,995
Contingency 30.0% $129,599
Sales Tax 9.0% $38,880
Planning Level Construction Cost = $600,500
Environmental Permitting and Documentation 5.0% $30,025
Administration 5.0% $30,025
Preliminary Engineering, PS&E Engineering and Construction Management 30.0% $180,150
2018 TOTAL = $840,700
ASSUMPTIONS:
Mobilization equals approximately 15-percent of Subtotal.
Traffic Control equals approximately 5-percent of Subtotal.
Erosion/Sedimentation Control equals approximately 2-percent of Subtotal ($1,000 min).
Pavement Restoration includes the cost of HMA (4-inch), CSTC (2-inch), and CSBC (6-inch).
Cost of pipe installation includes structure excavation and shoring.
Cost of catch basin installation includes structure excavation and shoring.
Several flooding issues occur in the vicinity of the wetland located at McPherson St and the 12th St ROW. This project proposes to construct roadside
bioswales to convey drainage from between McPherson St and Logan St to a new storm sewer pipe that will convey stormwater south along Thomas St to
an existing wetland. Runoff on 14th St from Logan St to Rosecrans St will be conveyed through proposed bioswales directing runoff to an existing
conveyance system that discharges to a critical drainage area on 16th St and Gise St. Additionally, an existing swale from the 12th St ROW will be
connected to a proposed closed storm system that will convey stormwater south to an existing conveyance system before discharge to a critical drainage
corridor.
CITY OF PORT TOWNSEND
Port Townsend Stormwater Management Plan
Preliminary Opinion of Probable Cost
Capital Project No. 3
Project Name:Center Street - San Juan Avenue to Olympic Avenue
Prepared By:Tyler Nabours Checked By:C. Buitrago
Project Description:
Item No.
Estimated
Quantity Unit Description Unit Cost Amount
1 1 LS Mobilization $33,700 $33,700
2 1 LS Traffic Control $11,500 $11,500
3 1 LS Erosion/Sedimentation Control $3,300 $3,300
4 283 LF Storm Sewer Pipe - 12 Inch $160 $45,280
5 350 LF Storm Sewer Pipe - 18 Inch $190 $53,770
6 1740 LF Ditch Grading $50 $87,000
7 1 EA Catch Basin Type I $3,960 $3,960
8 3 EA Catch Basin Type II $6,690 $20,070
9
10
Construction Subtotal (2018 Dollars) = $258,580
Inflation from 2018 to 2019 2.10% $5,430
Construction Subtotal (2019 Dollars) = $264,010
Contingency 30.0% $79,203
Sales Tax 9.0% $23,761
Planning Level Construction Cost = $367,000
Environmental Permitting and Documentation 5.0% $18,350
Administration 5.0% $18,350
Preliminary Engineering, PS&E Engineering and Construction Management 30.0% $110,100
2018 TOTAL = $513,800
ASSUMPTIONS:
Mobilization equals approximately 15-percent of Subtotal.
Traffic Control equals approximately 7-percent of Subtotal.
Erosion/Sedimentation Control equals approximately 2-percent of Subtotal ($1,000 min).
Pavement Restoration includes the cost of HMA (4-inch), CSTC (2-inch), and CSBC (6-inch).
Cost of pipe installation includes structure excavation and shoring.
Cost of catch basin installation includes structure excavation and shoring.
There exists a low point (sump) condition along Center St between San Juan Ave and Spruce St, along with a lack of well developed roadside drainage
infrastructure. This project proposes construction of roadside drainage ditches and culverts per the standard roadway section. There are two proposed
options of layout for closed conveyance of discharge from Center St to a wetland located south of Cedar St. Option A is to construct a closed conveyance
system (210 LF of 18" SSP) with purchase of easement through Parcel 943200036. Option B is to construct a closed system south along the east side of
San Juan Ave (350LF of 18" SSP). The existing catch basin located on the northeast quadrant of San Juan Ave and Cedar St and conveyance to the
wetlant may require removal based on required sizing of the proposed system. Cost estimate below reflects the construction of Option B due to
uncertainity in acquiring easement.
CITY OF PORT TOWNSEND
Port Townsend Stormwater Management Plan
Preliminary Opinion of Probable Cost
Capital Project No. 4
Project Name:Hancock Street and 32nd Street
Prepared By:Tyler Nabours Checked By:C. Buitrago
Project Description:
Item No.
Estimated
Quantity Unit Description Unit Cost Amount
1 1 LS Mobilization $15,400 $15,400
2 1 LS Traffic Control $4,800 $4,800
3 1 LS Erosion/Sedimentation Control $1,900 $1,900
4 560 LF Bioswale Grading $90 $50,400
5 200 LF Storm Sewer Pipe - 12 Inch $160 $32,000
6 190 LF Pavement Repair $50 $9,500
7 1 EA Catch Basin Type 1 $3,960 $3,960
8
9
10
Construction Subtotal (2018 Dollars) = $117,960
Inflation from 2018 to 2019 2.10% $2,477
Construction Subtotal (2019 Dollars) = $120,437
Contingency 30.0% $36,131
Sales Tax 9.0% $10,839
Planning Level Construction Cost = $167,400
Environmental Permitting and Documentation 5.0% $8,370
Administration 5.0% $8,370
Preliminary Engineering, PS&E Engineering and Construction Management 30.0% $50,220
2018 TOTAL = $234,360
ASSUMPTIONS:
Mobilization equals approximately 15-percent of Subtotal.
Traffic Control equals approximately 5-percent of Subtotal.
Erosion/Sedimentation Control equals approximately 2-percent of Subtotal ($1,000 min).
Pavement Restoration includes the cost of HMA (4-inch), CSTC (2-inch), and CSBC (6-inch).
Cost of pipe installation includes structure excavation and shoring.
Cost of catch basin installation includes structure excavation and shoring.
Poor drainage exists along Hancock St and in the intersection of Hancock St and 32nd St. Proposed solution includes the construction of bioswales per
Port Townsend standard proposed in this watershed plan. Bioswales are designed with 2 foot bottom widths and depth of 1.33 feet minimum with 3 to 1
side slopes to provide water quality treatment to roadway drainage. A proposed culvert beneath 32nd Street will convey flows north and west to a critical
drainage area. Stormwater currently captured by an existing catch basin tied to existing sanitary system at 31st Street and Hancock Street is proposed to
be conveyed west down 31st Street through culverts and bioswales to a critical drainage area to the west.
CITY OF PORT TOWNSEND
Port Townsend Stormwater Management Plan
Preliminary Opinion of Probable Cost
Capital Project No. 5
Project Name:Lawrence Street at Intersections of Polk Street, Taylor Street, and Tyler Street
Prepared By:Tyler Nabours Checked By:C. Buitrago
Project Description:
Item No.
Estimated
Quantity Unit Description Unit Cost Amount
1 1 LS Mobilization $92,600 $92,600
2 1 LS Traffic Control $39,600 $39,600
3 1 LS Erosion/Sedimentation Control $11,300 $11,300
4 2400 LF Storm Sewer Pipe - 12 Inch $160 $384,000
5 2400 LF Pavement Repair $50 $120,000
6 14 EA Catch Basin Type I $3,960 $55,440
7 1 EA Catch Basin Type II $6,690 $6,690
8
9
10
Construction Subtotal (2018 Dollars) = $709,630
Inflation from 2018 to 2019 2.10% $14,902
Construction Subtotal (2019 Dollars) = $724,532
Contingency 30.0% $217,360
Sales Tax 9.0% $65,208
Planning Level Construction Cost = $1,007,100
Environmental Permitting and Documentation 5.0% $50,355
Administration 5.0% $50,355
Preliminary Engineering, PS&E Engineering and Construction Management 30.0% $302,130
2018 TOTAL = $1,409,940
ASSUMPTIONS:
Mobilization equals approximately 15-percent of Subtotal.
Traffic Control equals approximately 7-percent of Subtotal.
Erosion/Sedimentation Control equals approximately 2-percent of Subtotal ($1,000 min).
Pavement Restoration includes the cost of HMA (4-inch), CSTC (2-inch), and CSBC (6-inch).
Cost of pipe installation includes structure excavation and shoring.
Cost of catch basin installation includes structure excavation and shoring.
Storm sewer catch basins located on Lawrence St at the intersections of Polk St, Taylor St, and Tyler St are currently directly connected the sanitary
sewer system. This project proposes the construction of new stormwater conveyance system with a 12" trunkline running north along Lawrence St with
lateral pipes and catch basins to collect stormwater on both sides of Lawrence St. This trunkline would connect to the existing 30" conveyance system
located along Monroe St, where capacity should be adequate to introduce this stormwater.
CITY OF PORT TOWNSEND
Port Townsend Stormwater Management Plan
Preliminary Opinion of Probable Cost
Capital Project No. 6
Project Name:Regional Stormwater Facility for Rainier Street Commercial Corridor
Prepared By:Tyler Nabours Checked By:C. Buitrago
Project Description:
Item No.
Estimated
Quantity Unit Description Unit Cost Amount
1 2 AC Clearing and Grubbing $11,000 $22,000
2 4500 CY Roadway Excavation Incl. Haul $15 $67,500
3 2000 CY Embankment Compaction $12 $24,000
4 1000 CY Common Borrow Incl. Haul $27 $27,000
5 2.5 AC Seeding, Fertilizing, and Mulching $3,250 $8,125
6 250 SY Stabilized Construction Entrance $15 $3,750
7 2000 LF Silt Fence $4 $8,000
8 1 LS Erosion Control and Watter Pollution Pl $15,000 $15,000
9 7 EA Inlet Protection $150 $1,050
10 50 DAY ESC Lead $150 $7,500
11 30 TON Quarry Spalls $40 $1,200
12 1450 LF Schedule a Storm Sewer Pipe 24 in. diam.$100 $145,000
13 6 EA Catch Basit Type 2 48 in. diam.$3,200 $19,200
14 1 EA Catch Basit Type 2 54 in. diam.$6,000 $6,000
15 1000 LF Chain Link Fence Type 3 $30 $30,000
16 1 EA Double 14 ft. Chain Link Gate $5,500 $5,500
17 50 TON Crushed Surfacing Top Course $40.00 $2,000
18 150 TON Crushed Surfacing Base Course $36.00 $5,400
19 1 LS Mobilization (@10%)$40,000.00 $40,000
Construction Subtotal (2018 Dollars) = $438,225
Inflation from 2018 to 2019 2.10% -
Construction Subtotal (2019 Dollars) = -
Contingency 20.0% $87,645
Sales Tax 9.0% $47,328
Planning Level Construction Cost = $573,198
Environmental Permitting and Documentation 5.0% -
Administration 5.0% -
Preliminary Engineering, PS&E Engineering and Construction Management 30.0% -
2018 TOTAL = $573,198
ASSUMPTIONS:
Cost provided by City of Port Townsend
The Regional Stormwater Facility will provide stormwater detention for approximately 33 acres of commercial properties and public rights-of-way along the
Rainier Street corridor from Discovery Road to the south side of Sims Way (SR 20). The facility will be a constructed pond, located just outside the city
limits and adjacent to Mill Road, that will be connected by pipes from the overflow of an existing stormwater pond on Rainier Street, south of SR 20.
CITY OF PORT TOWNSEND
Port Townsend Stormwater Management Plan
Preliminary Opinion of Probable Cost
Capital Project No. 7
Project Name:Logan Street Pond Overflow
Prepared By:Tyler Nabours Checked By:
Project Description:
Item No.
Estimated
Quantity Unit Description Unit Cost Amount
1
2
3
4
5
6
7
8
9
10
Construction Subtotal (2018 Dollars) =$0
Inflation from 2018 to 2019 2.10%$0
Construction Subtotal (2019 Dollars) =$0
Contingency 30.0%$0
Sales Tax 9.0%$0
Planning Level Construction Cost = $0
Environmental Permitting and Documentation 5.0%$0
Administration 5.0%$0
Preliminary Engineering, PS&E Engineering and Construction Management 30.0%$0
2018 TOTAL =$0
ASSUMPTIONS:
Mobilization equals approximately 15-percent of Subtotal.
Traffic Control equals approximately 2-percent of Subtotal.
Erosion/Sedimentation Control equals approximately 2-percent of Subtotal ($1,000 min).
Pavement Restoration includes the cost of HMA (4-inch), CSTC (2-inch), and CSBC (6-inch).
Cost of pipe installation includes structure excavation and shoring.
Cost of catch basin installation includes structure excavation and shoring.
The Logan Street Overflow project is to pipe the existing overflow pipe to the bottom of the ravine within the 3rd Street and Rosecrans Street rights-of-way
in order to stop the erosion of the existing bank. The budgeted amount in the 2019 budget is $30,000. This project currently does not have a more
detailed project estimate at this time.
Stormwater Management Plan
City of Port Townsend
ID Location Description
2-1 58th St. East of Gise St.Street Flooding
4c-1 Admiralty Ave. and Spruce St.Street Flooding
4e-1 Admiralty Ave. East of San Juan Ave.Stormwater Drains to Sewer Manhole Lid
4e-2 San Juan Ave. at 45th St., East Side Water Over Roadway
4f-1 Happy Valley Pond (43rd St.)Water Over Roadway
4f-2 Haines St.; 43rd St. to 45th St.No Conveyance
4f-3 McNeill St. North of 45th St.No Conveyance
4g-1 Landes St. & 49th St.; Northeast Corner Street Flooding
4h-1 53rd St. & 49th St.; Northwest Corner No Conveyance
4l-1 Howard St. Trail North of 35th St.Stormwater Eroding Trail
4l-2 Cook Ave. West of Seaview Dr.Stormwater Directed to Private Property
4m-1 Jackman St.; 47th St. to 49th St., West Side Local Flooding
6a-1 Center St.; San Juan Ave. to Spruce St.Water Ponding at Edge of Roadway
6a-2 Center St.; Spruce St. to P St.No Conveyance
6a-3 Pacific Ave. and Milo St. Intersection Water Over Roadway
6a-4 Tremont St. West of Pacific Ave.Infiltration System Insufficient
8b-1 Fir St. and Benton St.Lack of Conveyance
8c-1 Hancock St. & 32nd St. Intersection Ponding in Intersection
8c-2 1550 31st St.Lack of Conveyance, Property Damage
8c-3 Sherman St.; 31st St. to 32nd St.Catch Basin Tied to Sewer System
9c-1 16th St.; Gise St. to Hill St.Ravine Erosion
9d-1 Mountain View Police Road Lack of Conveyance
9f-1 Sheridan St. and 12th St.Lack of Conveyance
9f-2 Kearney St. and Franklin St.Flooding on Kearney Street
9f-3 14th St.; Cleveland St. to Landes St.Erosion at Edge of Roadway
9j-1 Thomas St. and Hastings Ave., SW Corner Flooding over Thomas Street
9j-2 Sherman St. & 27th St., NW Corner Inadequate Conveyance
9l-1 2010 Holcomb St.Street Runoff Flooding Driveway
10b-1 3rd St. and Grant St.Catch Basin Tied to Sewer System
11a-1 Discovery Rd. Northeast of Roundabout Flooding at Edge of Roadway
11b-1 McPherson St.; 9th St. to 11th St.Catch Basin Tied to Sewer System
11c-1 McPherson St. and 14th St.Water Ponding at Edge of Intersection
11e-1 3rd St. and Rosecrans St.Storm Pond Outfall Eroding Bluff
11f-1 3rd St. and Sherman St.Inadequate Conveyance
12a-1 1623 Jefferson St.Street Run-off Flooding Garage
12c-1 Water St.; Taylor St. to Adams St., (South)Ponding Over Sidewalk
12c-2 Fillmore St.; Jefferson St. to Washington St.Erosion at Edge of Roadway
12c-3 VanBuren St. and Franklin St.Catch Basin Has No Outlet
12d-1 Lawrence St. and Taylor St.Ponding on Southwest Corner
12f-1 Tyler St. and Oak St.Trail Erosion From Roadway Runoff
13a-1 Lincoln Beach Water Over Roadway
19-1 Hancock St. & 31st St.Catch Basin Tied to Sewer System
Drainage Problem Areas
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0 0.25 0.5 0.75 1
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Q:\Facilities\Storm\MasterPlan2017\Figures\xx-Stormwater-Problem-Areas.mxd 3/12/2019
Problem Areas
2019 Stormwater Management Plan Page G - 18
Drainage Basins
Potential Wetlands
Wetlands
Features
Critical Drainage Corridors
Key Drainageways
100 Year Flood Area
(19
City Limits
Appendix H
Stormwater Manual Comparison
719 2ND AVENUE, SUITE 200 | SEATTLE, WA 98104 | P 206.394.3700
TECHNICAL MEMORANDUM
DATE: December 7, 2017
TO: Samantha Harper, P.E.
FROM: Julie Brandt, P.E.
SUBJECT: Stormwater Manual Comparison
CC: Paul Fendt, P.E.
PROJECT NUMBER: 553-2836-004 (01/04)
PROJECT NAME: Stormwater Management Plan
1. INTRODUCTION
Port Townsend is developing a comprehensive stormwater management plan to improve the operation of the
city’s existing system and anticipate future needs. Part of the stormwater management plan development
includes review and evaluation of the City’s current stormwater standards and manuals. This technical
memorandum compares the City’s current adopted stormwater guidance manual against subsequent revisions
implemented by the Washington State Department of Ecology (Ecology).
2. CURRENT CITY GUIDANCE MANUAL
The City adopted Ecology’s 2005 Stormwater Management Manual for Western Washington (2005 SWMMWW)
under Section 13.32.010.A of the Port Townsend Municipal Code (Stormwater Code). The Stormwater Code
directs developers to use the 2005 SWMMWW for all clearing and grading activities, for erosion control during
construction, and for permanent drainage system improvements; except that developments must comply with
the following City requirements, which supersede the 2005 SWMMWW:
1. Section 2.6 – Optional guidance relating to financial liability and off-site analysis and mitigation
2. Engineering Design Standards
3. Stormwater Master Plan, and
4. Adopted drainage basin plans
The major elements included in the 2005 SWMMWW (and year the change was made) are:
1. Flow Control and Water Quality Treatment (2001):
The thresholds for selection of Best Management Practices (BMPs) were expanded to require nearly all
projects to apply appropriate flow control and runoff treatment BMPs, including on-site stormwater
management techniques.
TECHNICAL MEMORANDUM (CONTINUED)
City of Port Townsend 553-2836-004 (01/04)
Stormwater Manual Comparison 2 December 7, 2017
2. Duration Standard and Continuous Modeling (2001):
The flow control requirements were increased to address both peak flows and duration of high flows, and
calling for the use of continuous runoff models when available.
3. Enhanced Treatment (2001):
Requirements were increased to result in higher levels of water quality treatment (enhanced treatment)
for discharges from most industrial, commercial, and multifamily sites and arterials and highways.
4. Western Washington (2005):
The geographic scope of the SWMMWW was expanded to apply previous requirements to all of Western
Washington rather than Puget Sound only.
3. ECOLOGY REVISIONS
Subsequent to the City adoption of the 2005 SWMMWW, Ecology has published updates to the manual in 2012
and 2104. The major elements included in those updates (and year the change was made) are listed below in
order of their relevance to Port Townsend. Summary tables published by Ecology that discuss all of the
SWMMWW changes from 2012 and 2014 are included in Attachment 1.
1. Minimum Requirement 8 – Wetland Protection (2012):
Most of Appendix I-D was rewritten to remove outdated information, clarify concepts, and update the
requirements for protecting wetlands through controlling stormwater runoff discharges. Requirements
were added dictating that total discharges to wetlands must not deviate by more than 20 percent on a
single event basis and must not deviate by more than 15 percent on a monthly basis.
2. Puget Sound Action Agenda Terminology (2012):
Outdated references and guidance related to the Puget Sound Water Quality Management Plan were
removed and replaced with guidance on the Puget Sound Action Agenda.
3. Additional Basin Planning Guidance
Appendix I-A was updated to clarify the guidance for altering the minimum requirements through basin
planning, and language was added to address retrofit needs and alternative flow control strategies.
4. LID Requirements:
· LID Performance Standard for Stream Protection (2012) – The new LID performance standard and
BMP list options were added. The LID standard is based on project size, location, and BMP feasibility
for projects that discharge to fresh waterbodies.
Direct discharges to marine waterbodies through man-made conveyance systems are exempt from the
LID standard as long as erosion and flooding are prevented.
· LID Definition Consistency (2012) – Definitions were revised for terms relevant to the new low impact
development (LID) guidance (hard surfaces, LID, converted vegetation) and requirements in the
Municipal Stormwater Permits.
· Hard Surface Threshold Changes (2012) – Thresholds and terminology were updated to determine
which minimum requirements apply to new development and redevelopment, such as the
replacement of “impervious” surfaces with “hard” surfaces, the application of minimum
requirements #6 -#9 to replaced hard surfaces at new development sites, the deletion of the word
"native" from the land conversion threshold.
TECHNICAL MEMORANDUM (CONTINUED)
City of Port Townsend 553-2836-004 (01/04)
Stormwater Manual Comparison 3 December 7, 2017
· Updated Stormwater Site Plan Contents (2012) - Additional guidance was added regarding LID site
design.
· Construction Stormwater Pollution Prevention (2012) – Construction stormwater management
requirements were updated to protect LID BMPs
· Universal LID Language Clarification (2014) – Typos, spelling corrections, and terminology
inconsistencies that resulted from the incorporation of the LID standard were address throughout the
manual.
· Updated WWHM Software Guidance (2014) – Wording was revised to reflect recent upgrades to the
Western Washington Hydrology Model (WWHM2012) to include LID simulation capabilities.
5. Historical Development Map (2012):
To show which basins potentially qualify for use of existing land cover as the target for flow control
purposes, a map was added depicting basins that have had 40 percent or more total impervious area
since 1985. These basins are mainly comprised of areas between Everett and Tacoma east of Puget Sound
and in the vicinity of Bremerton and Bainbridge Island.
6. NPDES Permit References (2012):
· Guidance was added to refer Phase I and Phase II Municipal Stormwater Permittees to Appendix 1 of
their respective general permits for more information on the requirements for their stormwater
program requirements.
· An overview was added regarding the requirements of the Industrial Stormwater General Permit and
their relationship to the BMPs in the manual.
· An overview was added regarding the requirements of the Construction Stormwater General Permit
and their relationship to the BMPs in the manual.
4. RECOMMENDATION
The Ecology Manual was written to be reasonably applicable to a majority of landscapes and development
scenarios found in western Washington. With the exception of the new wetland protection standard, the key
recent SWMMWW revisions published by Ecology are not well-applied to Port Townsend development types,
landscape, receiving water bodies, and precipitation regimes. The City is not now precluded from using the LID
techniques described in the 2012 Manual and it could be expected that they would be used when applicable and
feasible because they are often a preferred choice for circumstances where they would function in the landscape
(e.g. good soils that infiltrate at high rates). Therefore, it is recommended that the City consider adoption of the
updated wetland protection standard through the Municipal Code and continue use of the 2005 SWMMWW.
Location Approximate Page
Numbers
Change Tied
to Permit
Language
Change Reasoning or Comments
General
Inside cover page ES-i and ES-ii Added an Executive Summary Summarized the reasons for the update, the uses of the manual and
provided information on the public involvement process.
All Volumes Renumbered Tables and Figures
Renumbered all tables and figures in all Volumes. The new numbers
coordinate tables and figures to the section of the Volume where they
are located. (Eg. Figure 2.4.2 is the second figure in Section 2.4, Table
4.1.3 is the third table in Section 4.1).
Chapter 1 - Introduction 1-1 through 1-26 Update incorrect or outdated code
references.
Revised incorrect or outdated code references, such as the RCW and
WAC.
Chapter 1 - Introduction 1-1 through 1-26 Minor language changes.Revised for clarity and removed outdate language in Sections 1.2, 1.4,
1.5.1, 1.6.10.
Section 1.5.4 Flow Control BMPs 1-5 Minor language changes.Revised language for changes made in Appendix I-D Guidelines for
Wetlands when Managing Stormwater.
Section 1.5.5 On-site Stormwater Management
BMPs 1-6 Additional guidance provided.Language added to categorize On-site Stormwater Management BMPs,
including LID BMPs.
Section 1.6.4 The Puget Sound Action Agenda 1-11 through 1-13
Significant revisions to remove outdated
guidance and to add new guidance. Section
renamed.
Removed references and guidance related to the Puget Sound Water
Quality Management Plan and replaced with guidance on the Puget
Sound Action Agenda.
Section 1.6.5 Phase I - NPDES and State Waste
Discharge Stormwater Permits for Municipalities 1-13 through 1-14 Yes Additional guidance provided and outdated
guidance removed.
Added guidance referring Phase I Municipal Stormwater Permittees to
Appendix 1 of the permit for more information on the requirements for
their stormwater program requirements.
Section 1.6.6 Phase II - NPDES and State Waste
Discharge Stormwater Permits for Municipalities 1-14 Yes Additional guidance provided and outdated
guidance removed.
Added guidance referring Phase II Municipal Stormwater Permittees to
Appendix 1 of the permit for more information on the requirements for
their stormwater program requirements.
Section 1.6.7 Municipalities Not Subject to the
NPDES Stormwater Municipal Permits 1-14 Guidance removed.Removed outdated references to the Puget Sound Water Quality
Management Plan. Section renamed.
Section 1.6.8 Industrial Stormwater General Permit 1-14 through 1-15 Yes Revised to coordinate with the current
Industrial Stormwater General Permit
Revised to provide an overview of the requirements of the current
Industrial Stormwater General Permit and their relationship to the BMPs
in the manual.
Section 1.6.9 Construction Stormwater General
Permit 1-15 through 1-16 Yes Revised to coordinate with the current
Construction Stormwater General Permit
Revised to provide an overview of the requirements of the current
Construction Stormwater General Permit and their relationship to the
BMPs in the manual.
Section 1.6.15 Underground Injection Control
Authorizations 1-18 through 1-19 Significant revisions to add guidance.Added language to refer to Ecology's website and to define UIC well.
Chapter 2 - Minimum Requirements for New
Development and Redevelopment 2-1 through 2-46 Minor language changes.Revised for clarity and removed outdated language in the introduction
and in Sections 2.1, 2.2, 2.5.3, and 2.5.10.
Chapter 2 - Minimum Requirements for New
Development and Redevelopment 2-1 through 2-46 Yes Revised language.
Revised definitions, requirements, supplemental guidance, etc. to
correspond to the changes in the Municipal Stormwater Permits and for
new LID requirements.
Volume I Minimum Technical Requirements and Site Planning
Chapter 1 - Introduction
Chapter 2 - Minimum Requirements for New Development and Redevelopment
Attachment 1a
2012‐2005 SWMMWW Chart of Changes
Location Approximate Page
Numbers
Change Tied
to Permit
Language
Change Reasoning or Comments
Section 2.1 Relationship to the Puget Sound Action
Agenda 2-2 Added guidance. Section renamed.
Removed outdated references to the Puget Sound Water Quality
Management Plan. Section renamed and focuses on relationship of the
manual to the municipal stormwater permits.
Section 2.3 Definitions Related to Minimum
Requirements 2-5 through 2-9 Yes Added and revised definitions.
Added definitions for a few terms used previously but not previously
defined. Other terms have a revised definition or a new definition (hard
surfaces, LID, converted vegetation) because of the new low impact
development (LID) guidance and requirements in the Municipal
Stormwater Permits.
Section 2.4 Applicability of the Minimum
Requirements 2-9 through 2-16 Yes
Revised the thresholds for determining
which minimum requirements apply to new
development and redevelopment. Revised
supplemental guidelines.
Changes include: the replacement of “impervious” surfaces with “hard”
surfaces, the application of minimum requirements #6 - #9 to replaced
hard surfaces at new development sites, the deletion of the word
"native" from the land conversion threshold.
Section 2.5.1 Minimum Requirement #1:
Preparation of Stormwater Site Plans 2-16 Yes Revised requirements and objective.
Added a new statement for the site plan to use site-appropriate
development principles to retain native vegetation and minimize
impervious surfaces to the extent feasible.
Section 2.5.2 Minimum Requirement #2:
Construction Stormwater Pollution Prevention
(SWPP)
2-17 through 2-26 Yes
Reorganized and revisions to: thresholds,
general requirements, construction SWPPP
elements, objective, and supplemental
guidelines.
Changes include: revisions to the construction SWPPP elements to
correspond with the Construction Stormwater General Permit, the
addition of element #13 that requires the protection of LID Best
Management Practices, and revision of element #12 to include
responsibilities for an inspector or CESCL depending on the size of the
project.
Section 2.5.4 Minimum Requirement #4:
Preservation of Natural Drainage Systems and
Outfalls
2-27 through 2-28 Yes Minor additions.Added clarification for peak discharges using 15 minute time steps.
Section 2.5.5 Minimum Requirement #5: On-site
Stormwater Management 2-28 through 2-32 Yes Multiple revisions for new low impact
development (LID) requirements.
Changes include: the new LID performance standard and list options
based on project size and location. The lists are divided into three land
use types: lawn and landscaped areas; roofs, and other hard surfaces.
Projects implementing the list option must select the first feasible BMP
for each land use type. Some of the BMPs included in the lists are: rain
gardens, permeable pavements, bioretention, soil quality and depth, full
and partial dispersion methods, full downspout infiltration and
perforated stub-outs.
Section 2.5.6 Minimum Requirement #6: Runoff
Treatment 2-33 through 2-35 Yes
Revisions to the thresholds, Water Quality
Design Flow Rate, and supplemental
guidelines.
Revisions made to acknowledge the use of permeable pavements and
the related new definitions. The intent is to continue to capture the
same size and types of projects as previously. More accurate definitions
for water quality design storm volume and flow rate.
Section 2.5.7 Minimum Requirement #7: Runoff
Flow Control 2-35 through 2-40 Yes Revisions to the thresholds and
supplemental guidelines.
Revisions to acknowledge the use of permeable pavements and the
related new definitions. Clarifications about the surfaces that the
requirement applies to, and the use of the 0.10 /0.15 cfs threshold. The
intent is to capture the same size and types of projects as previously.
Section 2.5.8 Minimum Requirement #8: Wetlands
Protection 2-40 through 2-41 Yes
Revisions to the applicability, thresholds,
standard requirement, additional
requirements, and supplemental guidelines.
Revisions correspond to the significantly revised Appendix I-D Guidelines
for Wetlands when Managing Stormwater .
Location Approximate Page
Numbers
Change Tied
to Permit
Language
Change Reasoning or Comments
Section 2.8 Exceptions/Variances 2-45 through 2-46 Yes Additional guidance provided.Changed and added language to be consistent with the requirements in
Appendix 1 of the 2007 municipal stormwater permits.
Chapter 3 - Preparation of Stormwater Site Plans 3-1 through 3-17 Yes
Significant changes to incorporate
procedures necessary for LID
implementation.
Revised for clarity and removed outdate language in the introduction
and in section 3.1.7.
Section 3.1.1 Step 1 - Collect and Analyze
Information on Existing Conditions 3-2 through 3-7 Yes Additional guidance provided and outdated
guidance removed.
Additional guidance details the information necessary for site analysis,
and in particular for LID site design. Split into subsections based on
whether Min. Requirements 1 - 5 apply, or Min. Requirements 1 - 9
apply.
Sections 3.1.2 to 3.1.4 3-7 through 3-8 Yes Guidance added.References to on-site BMPs added and preliminary determination of
applicable minimum requirements.
Section 3.1.5 Step 5 - Prepare a Permanent
Stormwater Control Plan 3-8 through 3-12 Yes
Revisions to all subsections of Developed
Site Hydrology of the Permanent
Stormwater Control Plan.
Significant changes to describe how to prepare the Permanent
Stormwater Control Plan that incorporates LID features. Separate
guidance for projects subject to Min. Requirements 1 - 5 and projects
subject to Min. Requirements 1 - 9.
Section 3.1.6 Step 6 - Prepare a Construction
Stormwater Pollution Prevention Plan 3-13 through 3-14 Yes Minor language changes.Changes for clarification and to remove repetitive language.
Section 3.1.7 Step 7 - Complete Stormwater Site
Plan 3-14 through 3-16 Yes
Reference to needed soils report and
addition of Declaration of Covenants and
Grants of Easement.
Soils reports are necessary part of LID decisions. Declarations of
Covenants and Grants of Easement are necessary mechanisms to identify
LID features, establish maintenance requirements and government
access for inspections of privately maintained stormwater BMPs and
facilities.
Section 3.2.2 Final Corrected Plan Submittal 3-17 Guidance added.Added several LID BMPs that require the submission of as-builts.
Section 4.2 BMP and Facility Selection Process 4-1 through 4-4
Revised language, proposed replacing the
language in Step V: Select Treatment
Facilities with a reference to Chapter 2 of
Volume V.
Revisions and new language especially in Step III for guidance on
modeling threshold discharge areas. Minor revisions to correspond with
the changes in the Municipal Stormwater Permits and for new LID
requirements. Ecology replaced the language in Step V: Select
Treatment Facilities with a reference to Chapter 2 of Volume V.
Appendix I-A Guidance for Altering the Minimum
Requirements Through Basin Planning A-1 through A-3 Additional guidance provided.Added language for clarity on use of Basin Planning for addressing
retrofit needs and for developing an alternative flow control strategy.
Appendix I-B Rainfall Amounts and Statistics B-1 through B-5
Removed introductory language and
background information on the Water
Quality Design Storm and Water Quality
Design Flow Rate.
Removed background and outdated information for brevity. Renamed
the appendix and retained the rainfall tables.
Chapter 3 - Preparation of Stormwater Site Plans
Chapter 4 - BMP and Facility Selection Process for Permanent Stormwater Control Plans
Appendix I-A Guidance for Altering the Minimum Requirements Through Basin Planning
Appendix I-B Rainfall Amounts and Statistics
Location Approximate Page
Numbers
Change Tied
to Permit
Language
Change Reasoning or Comments
Appendix I-D Guidelines for Wetlands when
Managing Stormwater D-1 through D-18 Yes
Multiple revisions for the use and/or the
protection of Wetlands when managing
stormwater.
Rewritten to remove outdated information, clarify concepts, and
approach the protection and use of wetlands through controlling
discharges to wetlands. Total discharges to wetlands must not deviate by
more than 20% on a single event basis, and must not deviate by more
than 15% on a monthly basis.
Appendix I-E Flow Control-Exempt Surface Waters E-1 through E-4 Yes Added and deleted Exempt Surface Waters.List edited to add additional waters based on specific requests and
analyses, and to remove reference to a creek in Eastern WA.
Appendix I-F Basins with 40% or more total
impervious area since 1985 F-1 Yes Added Map
Map shows basins which potentially qualify for use of existing land cover
as the pre-developed land cover for flow control purposes. See reference
in Min. Requirement #7.
Glossary and Notations Glossary-1 through
Glossary-47 Added and revised definitions.
There are a few terms, used previously but not defined, for which a
definition has been added. A handful of other terms have a revised
definition, and there are new terms, because of the new low impact
development (LID) guidance and requirements in the Municipal
Stormwater Permits.
Appendix I-D Guidelines for Wetlands when Managing Stormwater
Appendix I-E Flow Control-Exempt Surface Waters
Appendix I-F Feasibility Criteria for Selected Low Impact Development Best Management Practices
Glossary and Notations
Location Approximate Page
Numbers
Change Tied
to Permit
Language
Change Reasoning or Comments
Chapter 1 - Introduction Construction Stormwater
Pollution Prevention 1-1 through 1-9 Multiple revisions for plain language, clarity,
and brevity.Revised this chapter to use simpler and clearer language.
Section 1.3 How to Use This Volume N/A
This section was removed. The information
in this section is now included in Sections
1.2.
Removed this section by combining it with Section 1.2 to eliminate
duplicate language.
Section 1.3 Thirteen Elements of Construction
Stormwater Pollution Prevention 1-3 Yes Renamed.Revised to incorporate a new element, Protect Low Impact Development
BMPs.
Figure 1.5.1 1-6 Replaced.Replaced older figure with an updated one.
Chapter 2 - Regulatory Requirements 2-1 through 2-6 Multiple revisions for plain language, clarity,
and brevity.
Revised this chapter to use simpler and clearer language. Information
covered in Volume I, Section 1.6 Relationship of the Manual to Federal,
State, and Local Regulatory Requirements was removed.
Chapter 2 - Regulatory Requirements 2-1 through 2-6 Yes
Multiple revisions to coordinate the manual
to the Washington State General
Stormwater Permits.
Revised this chapter to update this information for revisions to the
Stormwater General Permits (including the Municipal, Construction, and
Industrial Permits).
Section 2.1 and Section 2.2 2-2 through 2-4 Yes
Section 2.1 The Construction Stormwater
General Permit and Section 2.2 Construction
Stormwater Pollution Prevention Plans now
replace the previous Sections 2.1 and 2.2.
Replaced these sections to remove invalid information or duplicate
information. Sections 2.1 and 2.2 now go into detail about the
relationship of Volume II to the Construction Stormwater General Permit
and the requirements for a Stormwater Site Pollution Prevention Plan.
Chapter 3 - Planning 3-1 through 3-32 Multiple revisions for plain language, clarity,
and brevity.
Revised this chapter to use simpler and clearer language. Information
covered in Volume I, Section 1.6 Relationship of the Manual to Federal,
State, and Local Regulatory Requirements was removed.
Section 3.2 and Section 3.3 3-4 through 3-32 Previous Sections 3.2 and 3.3 have been
reversed.
Moved The Construction SWPPP Requirements, previously in Section 3.3
to Section 3.2 for clarity. The Step-By-Step Procedure now follows in
Section 3.3. Please note that the Construction Stormwater Pollution
Prevention Plan Checklist is still located in Section 3.3.
Section 3.3.3 (Previously Section 3.2.3) Step 3 -
Construction SWPPP Development and
Implementation
3-8 through 3-32 Yes Multiple revisions to the Construction
SWPPP Elements.
Revised The Construction SWPPP Elements, described in Section 3.3.3 to
coordinate with the Construction Stormwater General Permit, Municipal
Stormwater Permits, and the Construction BMPs in Chapter 4. Each
element now contains an Additional Guidance section that has
information not required by the permits. Added Element #13 Protect
Low Impact Development BMPs.
Volume II Construction Stormwater Pollution Prevention
Chapter 1 - Introduction Construction Stormwater Pollution Prevention
Chapter 2 - Regulatory Requirements
Chapter 3 - Planning
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Chapter 4 - Best Management Practices Standards
and Specifications 4-1 through 4-128 Added approved equivalent BMPs Sections.Refers to Ecology's website for BMPs that have been approved as
equivalent.
Section 4.1 Source Control BMPs 4-1 through 4-2 Yes Added Table 4.1 Source Control BMPs by
SWPPP Element
Ecology added Table 4.1 Source Control BMPs by SWPPP Element to
show how the BMPs listed in Section 4.1 relate to the SWPPP Elements.
BMP C103: High Visibility Fence 4-6
This BMP now includes high visibility silt
fence. Multiple revisions for plain language,
clarity, and brevity.
Added high visibility silt fence because it meets the intent of BMP C103.
Ecology revised this chapter to use simpler and clearer language.
BMP C104: Stake and Wire Fence N/A This BMP was removed.Removed this BMP because BMP C103: High Visibility Fence meets the
intent of this BMP in a safer and more commonly used manner.
BMP C105: Stabilized Construction Entrance / Exit 4-7 through 4-9 Additional guidance provided and outdated
guidance removed.
Added and removed guidance for this BMP based on comments received
and field experience.
BMP C106: Wheel Wash 4-9 through 4-11 Additional guidance provided and outdated
guidance removed.
Added guidance to clarify that wheel wash wastewater shall not
discharge to surface or ground water.
Figure 4.1.2 - Wheel Wash 4-11 Figure was updated Updated figure to provide more details of a typical Wheel Wash.
BMP C120: Temporary and Permanent Seeding 4-13 through 4-19
Multiple revisions for plain language, clarity,
and brevity. Additional guidance provided
and removed.
Revised and reorganized this BMP to use simpler and clearer language.
Moved some guidance to BMP C121: Mulching or BMP C125: Top soiling.
Ecology added and removed additional guidance for this BMP based on
comments received and field experience.
BMP C121: Mulching 4-19 through 4-21 Additional guidance provided.
Added minimum mulch thickness based on field experience and
comments. Ecology added guidance previously found in BMP C120:
Temporary and Permanent Seeding to this BMP.
Table 4.1.8 4-21 Additional guidance provided.Added Wood Straw and Wood Straw Mulch to the table.
BMP C122: Nets and Blankets 4-22 through 4-25 Multiple revisions for plain language, clarity,
and brevity.Revised this BMP to use simpler and clearer language.
BMP C123: Plastic Covering 4-25 through 4-27 Additional guidance provided and outdated
guidance removed.
Removed the use of plastic sheeting over seeded areas because other
coverings (such as compost and straw) are preferable. Ecology added
and removed guidance for this BMP based on comments received and
field experience.
BMP C124: Sodding 4-27 through 4-28 Additional guidance provided and outdated
guidance removed.
Provided a link to composting guidance and removed old reference to
compost specification.
BMP C125: Top soiling / Composting 4-29 through 4-32 Additional guidance provided and outdated
guidance removed.
Added guidance previously found in BMP C120: Temporary and
Permanent Seeding to this BMP. Ecology added and removed guidance
for this BMP based on comments received and field experience.
BMP C150: Materials on Hand 4-42 through 4-43 Suggested measures and quantities
removed.
Removed measures and quantities because measures and quantities
should be based on the size of the construction site.
Chapter 4 - Best Management Practices Standards and Specifications
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BMP C151: Concrete Handling and BMP C152:
Sawcutting and Surface Pollution Prevention 4-43 through 4-45 Yes Additional guidance provided.
Added guidance to coordinate this BMP with the requirements of the
Construction Stormwater General Permit and to make it clear that
Concrete spillage or concrete discard to surface waters of the State is
prohibited.
BMP C154: Concrete Washout Area 4-48 through 4-53 Added this BMP.Added this BMP to provide additional guidance for concrete washout
areas.
BMP C160: Certified Erosion and Sediment Control
Lead 4-54 through 4-55 Additional guidance provided and outdated
guidance removed.
Minimum Requirements for ESC Training and Certification Courses has
been removed. Ecology plans on issuing separate, updated guidance in
the near future.
BMP C161: Payment of Erosion Control Work N/A This BMP was removed.Removed this BMP because it is not applicable to the full range of
projects needing to perform Erosion and Sediment Control Work.
BMP C180: Small Project Construction Stormwater
Pollution Prevention N/A Yes This BMP was removed.
Removed this BMP because of changes in threshold requirements in
both the Municipal Stormwater General Permits and Construction
Stormwater General Permit.
Section 4.2 Runoff Conveyance and Treatment
BMPs 4-57 Yes Added Table 4.2 Runoff Conveyance
Treatment BMPs by SWPPP Element
Added Table 4.2 Runoff Conveyance Treatment BMPs by SWPPP Element
to show how the BMPs listed in Section 4.2 relate to the SWPPP
Elements.
BMP C207: Check Dams 4-74 through 4-77 Additional guidance provided.Added guidance for this BMP based on comments received and field
experience.
BMP C220: Storm Drain Inlet Protection 4-78 through 4-79 Additional guidance provided.Added guidance for inlet protection of lawn and yard drains and based
on comment received and field experience.
BMP C230: Straw Bale Barrier N/A This BMP was removed.Removed this BMP because this BMP has been proven to be ineffective.
BMP C233: Silt Fence 4-90 through 4-95 Multiple revisions for plain language, clarity,
and brevity.Revised and reorganized this BMP to use simpler and clearer language.
BMP C235: Wattles 4-96 through 4-99 Renamed from Straw Wattles.Renamed this BMP to include wattles made from compost or other
materials.
BMP C236: Vegetated Spray Fields 4-100 through 4-102 Added this BMP.Added this new BMP for dewatering, Construction SWPPP Element #10.
BMP C250: Construction Stormwater Chemical
Treatment 4-112 through 4-120 Additional guidance provided.
Added guidance for this BMP, previously available online, to
coordinate with the Chemical Technology Assessment Protocol
(CTAPE) program.
BMP C251: Construction Stormwater Filtration 4-120 through 4-124 Additional guidance provided.Added sizing criteria for this BMP, previously available online.
BMP C252: High pH Neutralization Using CO2 4-125 through 4-127 Added this BMP.Added this BMP, previously available online, to provide guidance
on neutralizing high pH through the use of CO2.
BMP C253: pH Control for High pH Water 4-128 through 4-129 Added this BMP.Added this BMP, previously available online, to provide additional
guidance for neutralizing high pH.
Appendix II-B Background Information on Chemical
Treatment B-1 through B-3 Multiple revisions to coordinate with BMP
C252 and BMP C53.
Revised this appendix to coordinate with the new information provided
in BMP C252 and in BMP C253.
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Chapter 2 - Hydrologic Analysis
Chapter 2 - Hydrologic Analysis 2-1 through 2-17 Multiple revisions for plain language, clarity,
and brevity.
Revised this chapter to use simpler and clearer language. Outdated
guidance was replaced.
Section 2.2 Western Washington Hydrology Model 2-4 through 2-9 Section 2.2 split into multiple subsections.Section 2.2 split into multiple subsections for clarity and for referencing
purposes.
Section 2.2 Western Washington Hydrology Model 2-4 through 2-9 Additional guidance provided.Added guidance on upcoming Western Washington Hydrology Model
(WWHM) changes.
Section 2.2.2 Assumptions made in creating the
WWHM 2-5 through 2-8 Additional guidance provided.Added guidance on precipitation data and upcoming WWHM changes.
Section 2.2.3 Guidance for flow-related standards 2-8 through 2-9 Yes
Additional guidance provided and outdated
guidance removed for Minimum
Requirements (MR).
Added guidance for MR #5 which now includes an LID Performance
Standard. Revised the guidance for MR#8 to reflect the changes made in
Volume I, Appendix 1-D.
Chapter 3 - Flow Control Design 3-1 through 3-109 Multiple revisions for plain language, clarity,
and brevity.Revised this chapter to use simpler and clearer language.
Chapter 3 - Flow Control Design 3-1 Yes Update text for consistency with revised Min
Req'mt #5 and LID
Added references to Minimum Requirement #5, bioretention and
permeable pavements in introductory section.
Section 3.1 Roof Downspout Controls 3-1 through 3-18 Yes Update text & figure for consistency with
revised Min Req'mt #5 Text and figures updated to indicate priorities for handling roof runoff.
Section 3.1 Roof Downspout Controls 3-1 through 3-3 Yes Update text for consistency with revised Min
Req'mt #5
Updated references to revised roof downspout BMPs and Rain Gardens
in the introductory section.
Section 3.1.1 Roof Downspout Full Infiltration (BMP
T5.10A)3-4 through 3-10 Yes Update text for consistency with revised Min
Req'mt #5
Text changes for consistency with new priority lists in Min.Req'ment #5
and feasibility criteria. Needed better clarity in design guidance
Section 3.1.2 Downspout Dispersion Systems 3-11 through 3-16 Yes Update text for consistency with revised Min
Req'mt #5
Text changes for consistency with new priority lists in Min. Req'ment #5
and feasibility criteria. Improved clarify in design guidance and
computer modeling. Added guidance for design criteria for dispersion
trenches and splashblocks.
Section 3.1.3 Perforated Stub-out Connections 3-17 through 3-18 Yes Update text for consistency with revised Min
Req'mt #5
Text changes for consistency with new priority lists in Min. Req'ment #5
and feasibility criteria. Updated design guidance.
Section 3.2 Detention Facilities 3-19 through 3-64 Multiple revisions for plain language, clarity,
and brevity.Revised this chapter to use simpler and clearer language.
Section 3.2 Detention Facilities 3-35 Updated references.Updated Maintenance narrative to refer to Appendix IV-G Management
of Street Wastes in Volume IV.
Section 3.3 Infiltration Facilities for Flow Control
and Treatment 3-65 through 3-102 Section significantly rewritten.
Made significant changes to all sub-sections. Section pertains primarily to
design of centralized infiltration facilities. Certain sections also apply to
distributed bioretention facilities as indicated in text.
Section 3.3.1 Purpose 3-65 Yes Revised guidance and reference LID.
Expanded purpose statement and clarified in regard to the types of
facilities covered in Section 3.3. Added references to Bioretention and
Permeable Pavement sections.
Section 3.3.2 Description 3-65 Yes Additional guidance provided including Min
Req'mt #5.
Made clarifications and added language for complying with MR#5. Added
guidance for oil control and pre-treatment facilities.
Section 3.3.3 Applications 3-66 Additional guidance provided.Minor text change
Section 3.3.4 Steps for Design of Infiltration
Facilities 3-68 through 3-71 Yes
Revised several steps for new infiltration
rate guidance and the new LID performance
standard.
Revised Step 2 to include guidance for meeting MR#5. Significantly
revised Step 5 for the new guidance provided in section 3.3.6. Revised
Step 6 for clarity and for meeting MR#5. Revised Step 7 for clarity.
Volume III Hydrologic Analysis and Flow Control Design / BMPs
Chapter 3 - Flow Control Design
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Section 3.3.5 Site Characterization Criteria 3-72 through 3-75
Revised guidance on subsurface
characterization, soil testing, and infiltration
receptor. Removed guidance for
hydrogeologic investigation and figure 3.27,
USDA Textural Triangle.
Multiple changes to subsurface characterization include added guidance
on groundwater monitoring wells and the use of grain size analysis
method for estimating infiltration rates. Deleted infiltration rate
determination sub-section due to redundancy with next section.
Section 3.3.6 Design Saturated Hydraulic
Conductivity - Guidelines and Criteria 3-75 through 3-83
Revisions for determining the saturated
hydraulic conductivity (infiltration rate).
Section renamed.
Replaced "Infiltration Rate" with "Saturated Hydraulic Conductivity"
throughout section. Updated the guidelines and criteria for determining
saturated hydraulic conductivity. Added guidance on pilot infiltration
testing (PIT), and soil grain size analysis. Revised correction factors for
PIT results and soil grain size method. Removed options based on USDA
Soil Texture Classification and D10 grain size.
Section 3.3.7 Site Suitability Criteria (SSC)3-83 through 3-86 Additional guidance provided and outdated
guidance removed.
Updated references, removed unneeded guidance, revised limits on
infiltration rates, added a minimum organic content for treatment,
amended drawdown guidance, and verification testing.
Section 3.3.8 Steps for Designing Infiltration
Facilities - Detailed Approach 3-86 through 3-90
Multiple revisions. Previous steps 1-4
removed. Multiple steps revised. Added
groundwater mounding analysis step.
Removed steps to select location, estimate volume of stormwater,
develop a trial infiltration facility geometry, conduct a geotechnical
investigation, and determine the saturated hydraulic conductivity;
instead refers to steps 1-5 in section 3.3.4. Revised Figure 3.27 for
updated guidance. Revised guidance for adjusting the preliminary design
infiltration rate. Added a step for groundwater mounding analysis.
Added guidance for conducting performance testing.
Section 3.3.9 General Design, Maintenance, and
Construction Criteria for Infiltration Facilities 3-90 through 3-94 Additional guidance provided and outdated
guidance removed.
Added guidance for sizing for flow control, pretreatment design criteria,
and maintenance. Made wording clarifications to guidance.
Section 3.4 Site Procedures for Bioretention and
Permeable Pavement Use 3-103 through 3-109 Yes Added this section for bioretention and
permeable pavement.
Added guidance re field tests, computer modeling, and implementation
for bioretention / rain gardens and permeable pavement.
Appendix III-A Isopluvial Maps for Design Storms A-1 Added link to website.Added a link to a website where isopluvial maps are available.
Appendix III-B Western Washington Hydrology
Model - Information, Assumptions, and
Computation Steps
B-1 through B-13 Yes Additional guidance provided and outdated
guidance removed.
Added guidance on current and upcoming versions of WWHM. Added
guidance for the modeling on LID elements and wetlands. Removed
outdated computation steps.
Appendix III-C Washington State Department of
Ecology Low Impact Development Flow Modeling
Guidance
C-1 through C-13 Yes Additional guidance provided and outdated
guidance removed.
Text in regard to design guidance removed. All design guidance moved
to Volume V. Two sets of modeling guidance provided. One for WWHM
3, and one for upcoming WWHM 2012.
Appendix III-D Procedure for Conducting a Pilot
Infiltration Test N/A Appendix removed.
Procedures for conducting the PIT have been included within the
proposed text on “Design Infiltration Rate Determination” in sections
3.3.6.
Appendix III-B Western Washington Hydrology Model - Information, Assumptions, and Computation Steps
Appendix III-C Washington State Department of Ecology Low Impact Development Design and Flow Modeling Guidance
Appendix III-D Procedure for Conducting a Pilot Infiltration Test
Appendix III-A Isopluvial Maps for Design Storms
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Chapter 1 - Introduction 1-1 through 1-5 Minor language changes.Revised for clarity and removed outdated language.
Section 1.3 How to Use this Volume 1-2 Additional guidance provided and outdated
guidance removed.
Added new guidance regarding the Industrial Stormwater General Permit
(ISWGP), Boatyard General Permit (BGP), and Sand and Gravel General
Permit (S&GP) and the inclusion of "applicable" BMPs from this volume
in Industrial Stormwater Pollution Prevention Plans (Industrial SWPPPs).
Section 1.5 Treatment BMPs for Specific Pollutant
Sources 1-3 Yes Additional guidance provided and outdated
guidance removed.
Added new guidance clarifying the requirements regarding treatment
BMPs for facilities covered under the ISWGP (or other General
Stormwater Permits).
Section 1.6.1 Applicable (Mandatory) BMPs 1-3 through 1-4 Additional guidance provided and outdated
guidance removed.
Added new guidance describing the use of applicable (mandatory) BMPs
in regards to the ISGP, BGP, and S&GP. Section renamed to make it
clearer that applicable BMPs are Mandatory for permittees under the
ISWGP and BGP.
Section 1.6.2 Recommended BMPs 1-4 Yes Additional guidance provided.Added guidance regarding facilities covered under the ISWGP that trigger
a corrective action.
Chapter 2 - Selection of Operational and Structural
Source Control BMPs 2-1 through 2-66 Numbered BMPs.Added numbers in the "S400" series to BMPs in Volume IV.
Chapter 2 - Selection of Operational and Structural
Source Control BMPs 2-1 through 2-66 Minor revisions for plain language, clarity,
and brevity.
Revised BMPs to use simpler and clearer language, and removed
outdated references.
Chapter 2 - Selection of Operational and Structural
Source Control BMPs 2-1 through 2-2 Additional guidance provided and outdated
guidance removed.
Added new guidance describing the use of applicable (mandatory) BMPs
in regards to the ISGP, BGP, and S&GP. Added guidance regarding
facilities covered under the ISWGP that trigger a Level 1 or 2 corrective
action.
Section 2.1 Applicable (Mandatory) Operational
Source Control BMPs 2-2 through 2-6 Additional guidance provided and outdated
guidance removed.
Revised wording to clarify where this Section applies. Revised several
BMPs for clarity and to coordinate with the ISWGP. Significant changes
include the addition of vacuum sweeping and pressure washing, spill
prevention and cleanup, visual inspections and record keeping.
Section 2.2 Pollutant Source Specific BMPs 2-7 through 2-66
Additional guidance provided and outdated
guidance removed. Minor formatting
revisions.
Revised wording to clarify where this Section applies. Added new text on
ISWGP requirements. Added guidance regarding facilities covered under
the ISWGP that trigger a Level 1 or 2 corrective action. Changed the title
format for the BMPs to match the other volumes and added a numbering
system to the BMPs.
S401 BMPs for the Building, Repair, and
Maintenance of Boats and Ships 2-7 through 2-9 Additional guidance provided and several
BMPs clarified.
Clarified guidance describing the requirements under the BGP and ISGP
regarding boatyard activities. Revised BMPs to use simpler and clearer
language.
S402 BMPs for Commercial Animal Handling Areas 2-10 Minor revisions for plain language, clarity,
and brevity.Revised BMPs to use simpler and clearer language.
S403 BMPs for Commercial Composting 2-10 through 2-12 Additional guidance provided and outdated
guidance removed.
Revised language because solid waste regulations prohibit discharge of
compost leachate. Revised BMPs to use simpler and clearer language,
and removed outdated references.
Volume IV Source Control BMPs
Chapter 1 - Introduction
Chapter 2 - Selection of Operational and Structural Source Control BMPs
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S405 BMPs for Deicing and Anti-Icing Operations -
Airports and Streets 2-13 through 2-14 Additional guidance provided and outdated
guidance removed.
Revised language to coordinate with the ISGP. Removed outdated
references.
S414 BMPs for Maintenance and Repair of Vehicles
and Equipment 2-32 through 2-34 Yes Revision for consistency with the ISGP Updated "applicable BMP" guidance for handling of liquids in scrap
vehicles to align with ISGP.
S416 BMPs for Maintenance of Roadside Ditches 2-35 through 2-37 Additional guidance provided and updated
references.Additional guidance provided for the handling of ditch cleanings.
S423 BMPs for Recyclers and Scrap Yards 2-45 through 2-46 Updated reference to guidance.Updated the reference to guidance for Vehicle Recyclers.
S424 BMPs for Roof/Building Drains at
Manufacturing and Commercial Buildings 2-46 through 2-47 Added reference to guidance.Added a references to Volume V and Ecology publications for BMPs.
S426 BMPs for Spills of Oil and Hazardous
Substances 2-48 through 2-49 Additional guidance provided and outdated
guidance removed.Revised several BMPs for clarity and to coordinate with the ISWGP.
S430 BMPs for Urban Streets 2-58 through 2-59 Additional guidance provided.Clarified that facilities not under the ISWGP may consider some water
use in street cleaning.
S431 BMPs for Washing and Steam Cleaning
Vehicles / Equipment / Building Structures 2-60 through 2-62 Yes Additional guidance provided and outdated
guidance removed.
Added guidance to clarify that the ISWGP prohibits the discharge of
process wastewater to ground water or surface water. Removed
outdated guidance.
Figure 2.15 - Uncovered Wash Area N/A Figure Deleted Figure was unclear and the existing text provided a better description of
the required controls.
S432 BMPs for Wood Treatment Areas 2-63 through 2-64 Additional guidance provided and several
BMPs clarified.
Clarified guidance describing which NPDES permit(s) regulate wood
treatment areas. Revised BMPs to use simpler and clearer language.
S433 BMPs for Pools, Spas, Hot Tubs and Fountains 2-64 through 2-66 Additional guidance provided.Added this BMP to provide further guidance consistent with BMPs within
this volume.
Appendix IV-A Urban Land Uses and Pollutant
Generating Sources A-1 through A-24 Minor language changes.Edits for clarity and to replace and revise guidance documents and WAC
references.
Commercial Composting - SIC 2875 A-14 Additional guidance provided Added "Potential Pollutant Generating Sources"
Appendix IV-B Stormwater Pollutants and Their
Adverse Impact B-1 through B-2 Minor language changes. Removed Table.Minor language changes for clarity. Removed the outdated Table in
Appendix IV-B.
Appendix IV-C Recycling/Disposal of Vehicle
Fluids/Other Wastes C-1 Minor language changes.Minor language changes for clarity.
Appendix IV-D Regulatory Requirements That
Impact Stormwater Programs D-1 through D-9 Minor language changes.Edits for clarity and to replace and revise guidance documents and WAC
references.
Appendix IV-E NPDES Stormwater Discharge
Permits E-1 through E-7 Yes Additional guidance provided and outdated
guidance removed.
Edits to make guidance consistent with the most recent industrial and
municipal stormwater permits.
Appendix IV-G Recommendations for Management
of Street Wastes G-1 through G-15
Multiple revisions for plain language, clarity,
and brevity. Additional guidance provided
and outdated guidance removed.
Removed outdated guidance and added new guidance in the
contamination in Street Waste Solids subsection. Reorganized the
disposal of street waste liquids subsection, no major content changes.
Minor revisions to the Site Evaluation subsection.
Appendix IV-C Recycling/Disposal of Vehicle Fluids/Other Wastes
Appendix IV-D Regulatory Requirements That Impact Stormwater Programs
Appendix IV-E NPDES Stormwater Discharge Permits
Appendix IV-G Recommendations for Management of Street Wastes
Appendix IV-A Urban Land Uses and Pollutant Generating Sources
Appendix IV-B Stormwater Pollutants and Their Adverse Impact
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Chapter 1 - Introduction 1-1 through 1-4 Minor revisions for plain language, clarity,
and brevity.
Revised BMPs to use simpler and clearer language, and removed
outdated references.
Section 1.4.3 Treatment Methods 1-2 through 1-4 Additional guidance provided and outdated
guidance removed.
Revised guidance for oil/water separation, pretreatment, infiltration,
filtration, emerging technologies, and on-line systems. Added
Bioretention as a treatment method.
Chapter 2 - Treatment Facility Selection Process 2-1 Additional guidance provided.Added paragraph on emerging technology options.
Section 2.1 Step-by-Step Selection Process for
Treatment Facilities 2-1 through 2-9
Minor revisions to the steps. Revised
description of surface waters triggering
enhanced treatment.
Revised selection process steps for clarity and to remove outdated
information. Revised the Treatment Facility Selection Flow Chart for
revised guidance throughout Volume V. Revised description of surface
waters triggering enhanced treatment for accuracy.
Figure 2.1.1 2-3 Revised list of options.
Some treatment BMP options removed, emerging technologies added,
one BMP renamed. Added a note for Phosphorous facilities that require
Enhanced Treatment.
Section 2.2 Other Treatment Facility Selection
Factors 2-9 through 2-11
Removed the subsection on Pollutants of
Concern, the Suggested Treatment Options
Table, and Ability of Treatment Facilities
Table.
Removed the Suggested Treatment Options Table and Ability of
Treatment Facilities Table because they provided limited usefulness and
removed the associated subsection, Pollutants of Concern.
Chapter Introduction Paragraph 3-1 Additional guidance provided.Added paragraph on emerging technology options.
Section 3.2 Oil Control Menu 3-2 through 3-3 Revised list of options.
Removed catch basin inserts and added emerging stormwater treatment
technologies. To date, no catch basin inserts have been approved though
the TAPE process but Ecology has approved one emerging technology.
Deleted the "Where Applied" section since it was duplicated from
Chapter 2.
Section 3.3 Phosphorous Treatment Menu 3-3 through 3-4 Revised list of options.
Removed amended sand filter (no design criteria have been developed
for this treatment), and media filter, added emerging stormwater
treatment technologies. Deleted the "Where Applied" section since it
was duplicated from Chapter 2.
Section 3.4 Enhanced Treatment Menu 3-5 through 3-7
Multiple revisions to remove outdated
guidance and to provide new guidance.
Revised list of options. Revised waters
triggering enhanced treatment consistent
with Chapter 2.
Revised the performance goal for dissolved metals. Removed Amended
Sand Filter. Added "vegetated" to "Compost Amended "Vegetated" Filter
Strip. Removed "rain garden" for consistency with proposal to distinguish
between "bioretention" and "rain gardens." Replaced "Ecology
Embankment" with "Media Filter Drain." Added emerging technologies.
Deleted the "Where Applied" section since it was duplicated from
Chapter 2.
Section 3.5 Basic Treatment Menu 3-7 through 3-9 Minor language changes for clarity. Revised
list of options.
Removed "rain garden" for consistency with proposal to distinguish
between "bioretention" and "rain gardens." Replaced "Ecology
Embankment" with "Media Filter Drain". Added Compost-amended
Vegetated Filter Strip. Removed Bio-infiltration Swale. Added emerging
technologies. Deleted the "Where Applied" section since it was
duplicated from Chapter 2.
Section 4.1.1 Water Quality Design Storm Volume 4-1 Yes Inserted updated modeling guidance.New guidance more accurately describes how volume is determined by
computer models.
Chapter 1 - Introduction
Chapter 2 - Treatment Facility Selection Process
Chapter 3 - Treatment Facility Menus
Chapter 4 - General Requirements for Stormwater Facilities
Volume V Runoff Treatment BMPs
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Section 4.1.2 Water Quality Design Flow Rate 4-1 through 4-2 Minor language changes for clarity.Revised language for clarity.
Section 4.1.3 flows Requiring Treatment 4-2 through 4-4 Minor language changes for clarity. Changes
to incorporate new terms.
Replaced "impervious" surfaces with "hard" surfaces in coordination with
general changes in terminology. Added guidance regarding pollution-
generating hard surfaces, pollution-generating impervious surfaces, and
pollution-generating pervious surfaces.
Section 4.6 Maintenance Standards for Drainage
Facilities 4-31 through 4-53 Yes Added new tables within overall set of
operation and maintenance standards
Changed "StormFilter" to "Manufactured Media Filters", added
information from WSDOT on Media Filter Drains and Compost Amended
Vegetated Filter Strips. Minor additions to the recommended
maintenance tables added. Added placeholders for Bioretention and
permeable pavement pending completion of the development of LID
maintenance standards grant.
Section 5.1 Purpose 5-1 Additional guidance provided.
Add reference to expanded BMP options and LID Manual to acknowledge
the expansion of Chapter 5 and source of additional design details (LID
Manual).
Section 5.2 Application 5-1 Yes Additional guidance provided.Revised application to refer specifically to Minimum Requirements #5,
#6, and #7.
Section 5.3 Best Management Practices for On-Site
Stormwater Management 5-1 through 5-2 Additional clarifying guidance provided. Full
list of BMPs provided.
Expanded the list of BMPs in sections 5.3.1 and 5.3.2. Revised language
and references for clarity.
Section 5.3.1 On-site Stormwater Management
BMPs 5-3 to 5-39 Yes Amend existing BMP's add new BMP's
Downspout infiltration moved to Volume III. Revised BMP T5.11
Concentrated Flow Dispersion and BMP T5.12 Sheet Flow Dispersion.
Updated figures. Added BMP T5.14A Rain Gardens and BMP T5.14B
Bioretention but details are in Volume V of Chapter 7. Added BMP T5.15
Permeable Pavements, BMP T5.16 Tree Retention and Tree Planting,
BMP T5.16 Vegetated Roofs, BMP T5.18 Reverse Slope Sidewalks, BMP
T5.19 Minimal Excavation Foundations, BMP T5.20 Rainwater Harvesting.
Revised BMP T5.30 Full Dispersion by incorporating details from previous
Appendix III-C.
Section 5.3.2 Site Design BMPs 5-39 through 5-42 Deleted Full Dispersion and section 5.3.3
Other Practices
Moved Full Dispersion into Section 5.3.1 because the Municipal
Stormwater Permits make it a necessary option in MR #5. Clarifying
statement added in BMP T5.40.
Section 6.1 Purpose 6-1 Minor language changes.Removed "and media filtration" in first bullet for clarity.
Section 6.2 Application 6-1 Additional guidance provided.Added discussion that there are emerging technologies approved for
pretreatment.
Section 6.3 Best Management Practices (BMPs) for
Pretreatment 6-1 Additional guidance provided.Added reference to Chapter 12.
Section 7.1 Purpose 7-1 Changed bioinfilltration to bioretention.Updated listed BMPs and made minor revisions to text.
Sections 7.2 General Considerations 7-1 Additional guidance provided.Renamed this Section and added information regarding Bioretention and
Rain Gardens.
Sections 7.3 Applications 7-1 through 7-2 Additional guidance provided.Renamed this Section and added information for the BMPs discussed in
this chapter.
Chapter 6 - Pretreatment
Chapter 7 - Infiltration and Bioretention Treatment Facilities
Chapter 5 - On-Site Stormwater Management
Location Approximate Page
Numbers
Change Tied
to Permit
Language
Change Reasoning or Comments
Section 7.4 and BMPs 7.10 & 7.20 7-2 Updated references to Volume III Design details for these BMPs remain in Volume III.
BMP T 7.30 Bioretention Cells, Swales, and Planter
Boxes 7-3 through 7-25
Replaced Bio-infiltration Swale with
Bioretention Cells, Swales, and Planter
Boxes.
Added detailed guidance, design criteria, infeasibilty criteria and figures
for Bioretention Cells, Swales, and Planter Boxes.
BMP T7.40 Compost-amended Vegetated Filter
Strips (CAVFS)7-25 through 7-29 Transferred this BMP from Chapter 9.Added guidance and design criteria for Compost-Amended Vegetated
Filter Strips. Treatment via infiltration through amended soils.
Chapter 8 - Filtration Treatment Facilities 8-1 through 8-39 Changed title and introduced minor
language changes for clarity.Revised name from Sand Filtration to just Filtration.
8.1 Purpose 8-1 Revised guidance.Revised the purpose to apply to both sand and media filtration facilities.
8.2 Description 8-1 Additional guidance provided.Added reference to Media Filter Drain to description.
Section 8.3 Performance Objectives 8-2 Included new technologies Added Media Filter Drain to list of approved technologies. Clarified
objective for sand filters.
Section 8.4 Applications and Limitations 8-2 Revised guidance.Revised to include media filter drains.
Section 8.5 Best Management Practices (BMPs) for
Sand Filtration / BMP T8.10 Sand Filter Basin 8-2 to 8-15 Renamed and reorganized section.
Additional guidance provided.
Added design criteria for sand filter basins. reorganized section so that
previous sections 8.5, 8.6, 8.7, & 8.8 become subsections under BMP
T8.10.
BMP T8.11 Large Sand Filter Basin 8-16 through 8-17 Separated out BMP previously reference
within BMP T8.10
BMP T8.11 Large Sand Filter Basin was described in the prior manual
under BMP T8.10 Sand Filter Basin. The Large Sand Filter was given a
separate BMP for clarity.
BMP T8.20 Sand Filter Vault 8-17 through 8-23 Additional guidance provided.Added design criteria, construction criteria, and maintenance criteria for
sand filter vault.
BMP T8.40 Media Filter Drain 8-24 through 8-38 Added this BMP.
Added design criteria for new Media Filter Drain (MFD) option
(previously referred to as Ecology Embankment). Text matches WSDOT
Highway Runoff Manual.
Chapter 9 - Biofiltration Treatment Facilities 9-1 through 9-26 Minor language changes for clarity.Minor language changes for clarity throughout the chapter.
Section 9.4 Best Management Practices 9-1 through 9-26 Additional guidance provided and outdated
guidance removed.Revised list of BMPs. Revised Sizing Criteria table for clarity.
BMP T9.50 Narrow Area Filter Strip N/A Removed this BMP.No design criteria exists for this BMP to validate basic treatment.
Designers should refer to Basic Filter Strip.
BMP T10.10 Wet Pond 10-1 through 10-17 Minor language changes for clarity.
First cell must be lined to be consistent with liner requirements in
Chapter 4. Added cell requirements for consistency with design criteria
for 2-cell ponds. Definition of WQ Design Storm Volume amended.
BMP T11.10 API (Baffle type) Separator Bay 11-8 through 11-9 Corrected formula.Corrected Stokes Law equation for rise rate.
BMP T11.11 Coalescing Plate (CP) Separator Bay 11-10 through 11-11 Corrected formula.Corrected the equation to calculated the projected (horizontal) surface
area of plates.
Chapter 12 - Emerging Technologies 12-1 through 12-6 Replaced sections 12.1 through 12.5 with
new guidance.
Replaced sections 12.1 through 12.5 to provide new guidance on the
Technology Assessment Protocol (TAPE) review and approval process.
Chapter 11 - Oil and Water Separators
Chapter 12 - Emerging Technologies
Chapter 8 - Sand Filtration Treatment Facilities
Chapter 9 - Biofiltration Treatment Facilities
Chapter 10- Wetpool Facilities
Location Approximate Page
Numbers
Change Tied
to Permit
Language
Change Reasoning or Comments
Section 12.6 Examples of Emerging Technologies
for Stormwater Treatment and Control N/A Removed examples of emerging
technologies.
Removed examples of emerging technologies. Added some examples
previously listed throughout this volume.
Appendix V-B Recommended Modifications to
ASTM D 2434 When Measuring Hydraulic
Conductivity for Bioretention Soil Mixes.
B-1 through B-2 Additional guidance provided.
Added Recommended Modifications to ASTM D 2434. The results of this
test for saturated hydraulic conductivity can be influenced by how the
general procedures in the ASTM method are implemented. This
appendix lays out more specific procedures to help with consistency in
evaluating soils used for bioretention.
Appendix V-C Geotextile Specifications C-1 through C-3 Revised Guidance.Corrected several test procedures and geotextile property requirements.
Appendix V-E Recommended Newly Planted Tree
Species E-1 through E-5 New appendix pertinent to BMP T5.16 Lists of species from City of Seattle guidance.
Appendix V-C Geotextile Specifications
Appendix V-B Recommended Procedures for ASTM D 2434
Appendix V-E Recommended Bioretention Plant Species
Location Change Reasoning or Comments
Updated date in footer Date updated to reflect the manual's revision date
Updated page numbers and Figure numbers as
appropriate Page and Figure numbers may have changed due to content insertion or deletion
Updated Table of Contents as appropriate Some page numbers may have changed due to content insertion or deletion
Minor spelling corrections examples include: groundwater changed to ground water; under‐drain changed to underdrain
Minor text clarifications examples include: changing "the Department of Ecology" to "the Washington State Department of
Ecology"; inserting and/or clarifying acronyms where appropriate
Minor typographical errors examples include changing "text" to test" and "lopers" to "loppers"
Updates per previous errata Updates per previously published errata to the 2012 SWMMWW have been incorporated
Volume I Acknowledgements Minor language changes Inserted text indicating the shorthand for "The Washington State Department of Ecology" is "Ecology",
added Craig Doberstein to the acknowledgement list, reformated the acknowledgement list
Section 1.1 ‐ Objective corrected "Ground Waters" to "Groundwaters"Although the rest of the manual uses the spelling "ground water" (two separate words), the spelling
here was updated to be consistent with the WAC title referenced
Section 1.6.4 ‐ The Puget Sound Action Agenda Revised this section Revision of this section reflects changes from the Puget Sound Partnership's 2008 Action Agenda to the
Puget Sound Partnership's 2014/2015 Action Agenda
Deleted sentence: "They are considered
redevelopment."
These practices are not restricted to redevelopment projects. The bullets that follow this sentence
properly indicate that how the surfaces are considered within new or redevelopment projects.
Restored formatting for second bullet
See the 2012 to 2014 SWMMWW Redlines for full change details.
Attachment 1b
2012‐2014 SWMMWW Chart of Changes
Volume I ‐ Minimum Technical Requirements and Site Planning
Chapter 1 ‐ Introduction
Chapter 2 ‐ Minimum Requirements for New Development and Redevelopment
All Volumes
Section 2.2 ‐ Exemptions
Restored formatting for second bullet
regarding extending the pavement edge.Formatting error correction
Section 2.3 ‐ Definitions definitions have been moved from seciton 2.3
to the Glossary definitions have been moved in an effort to consolidate and organize the SWMMWW
revised wording to read "volumetric flow rate
calculated using a 10‐minute time step"edit made to accurately describe the design criterion
revised "with outfall to" to "that discharges to"revision made per settlement agreement PCHB No. 12‐097c
Section 2.5.5 ‐ Minimum Requirement #5: On‐Site
Stormwater Management Added Figure 2.5.1: MR5 Flow Chart A flow chart to help determine MR5 requirements
Added text: "Testing should occur between
December 1 and April 1."Clarification
Under Projects required to meet MR 1‐9: 2.c.,
revised cited clearances Revised to be consistent throughout the manual
Section 3.1.2 ‐ Step 2 ‐ Prepare Preliminary
Development Layout
Added text referring to LID manual for
additional information clarification
Added a definition for "Biosolids"Clarification
Deleted the definition for "Commercial
Agriculture"The entry deleted was a duplicate entry and out of aphabetical orderGlossary
Chapter 3 ‐ Preparation of Stormwater Site Plans
Appendix I‐G ‐ Glossary and Notations
Section 2.5.2 ‐ Minimum Requirement #2:
Construction Stormwater Pollution Prevention
(SWPP)
Section 3.1.1 ‐ Step 1 ‐ Site Analysis: Collect and
Analyze Information on Existing Conditions
2012‐2014 SWMMWW Chart of Changes Revised April 2015
Location Change Reasoning or Comments
Deleted the definition for "Converted
Vegetation (areas)"The entry deleted was a duplicate entry and out of aphabetical order
Commercial Agriculture definition ‐ replaced
the word "wholesale" with "commercial" within
the definition
Clarification
Amended definition for compost. Deleted
composted mulch and composting.Updated to correct WAC reference.
Added a definition for "Discharge Point"Added for consistency with proposed permit modification as part of a settlement under PCHB No. 12‐
093c and ‐ 097c
Updated freeboard definition Reworded for clarification
revised "Low Permeable Liner" definition revised to be consistent with other text within the manual
Added a definition for "Mulch"Clarification
Added definition for "outfall"Added for consistency with proposed permit modification as part of a settlement under PCHB No. 12‐
093c and ‐ 097c
Deleted reference to Rain Garden Handbook in
"Rain Garden" definition. Ecology prefers users to first refer to the guidance within the SWMMWW
Updated "receiving waters" definition Revised for consistency with proosed permit modification as part of a settlement under PCHB No. 12‐
093c and ‐ 097c
revised wording to read "volumetric flow rate
calculated using a 10‐minute time step"edit made to accurately describe the design criterion
revised "sites larger than 1 acre" to "applies
only to sites that have coverage under the
Construction Stormwater General Permit"
revised to clarify the intent of the original wording
Glossary
Volume II ‐ Construction Stormwater Pollution Prevention
Chapter 3 ‐ Planning
Section 3.3.3 ‐ Step 3 ‐ Construction SWPPP
Development and Implementation
added wording to clarify that the LID Technical
Guidance Manual is for additional informational
purposes only
Clarification that the SWMMWW guidance overrules the LID Technical Guidance Manual if discrepancies
are found
Section 4.1 ‐ Source Control BMPs
Table 4.1.1 updated to match Errata, and
reformatted as a word table for ease in future
revisions
See 10/14/2013 Errata
BMP C121: Mulching
Added a specification for coarse compost for
use when the option of Composted Material is
selected
Clarification
BMP C121, Table 4.1.8
Replaced the terms "composted mulch and
compost" with terms consistent with WAC 173‐
350
Clarification
BMP C125: Topsoiling/Composting Updated for consistency with BMP T5.13 Clarification
BMP C151: Concrete Handling Updated sentence to clarify that concrete
washout cannot be discharged to ground Clarification
Updated sentence to clarify that concrete
washout cannot be discharged to ground Correction
Removed wording telling volume of wash water
typically used Clarification
Chapter 4 ‐ Best Management Practices Standards and Specifications
BMP C154: Concrete Washout Area
2012‐2014 SWMMWW Chart of Changes Revised April 2015
Location Change Reasoning or Comments
Section 4.2 ‐ Runoff Conveyance and Treatment
BMPs
Table 4.2.1 updated to match Errata, and
reformatted as a word table for ease in future
revisions
Clarification
BMP C200: Interceptor Dike and Swale revised wording to read "volumetric flow rate
calculated using a 10‐minute time step"edit made to accurately describe the design criterion
BMP C201: Grass‐Lined Channels revised wording to read "volumetric flow rate
calculated using a 10‐minute time step"edit made to accurately describe the design criterion
BMP C204: Pipe Slope Drains revised wording to read "volumetric flow rate
calculated using a 10‐minute time step"edit made to accurately describe the design criterion
Section 2.2 ‐ Western Washington Hydrology Model
updated sentence to state that low impact
development modeling capabilities have been
added to WWHM2012
wording was revised to reflect updates to WWHM since the last publishing of the SWMMWW
Section 2.2.1 ‐ Limitation to the WWHM
Clarified that routing limitations in the earlier
versions of WWHM (WWHM1 and WWHM2)
have changed considerably. WWHM3 and
WWHM2012 have much greater routing
capability that allow them to model multiple
facilities and wetlands
wording was revised to reflect updates to WWHM since the last publishing of the SWMMWW
Clarified that WWHM2012 now uses over 50
years of precipitation time series from more
than 17 stations. Precipitation time series are
in 15‐minute time steps
wording was revised to reflect updates to WWHM since the last publishing of the SWMMWW
Chapter 2 ‐ Hydrologic Analysis
Volume III ‐ Hydrologic Analysis and Flow Control BMPs
in 15 minute time steps.
Clarified that WWHM2012 now uses 15‐minute
precipitation time series in its computations to
generate hydrographs and to calculate water
quality design flows
wording was revised to reflect updates to WWHM since the last publishing of the SWMMWW
Clarified that the advanced user may change
coefficient Precipitation multiplication factor
where justified and approved by reviewing
jurisdiction
Clarification
Clarified that the advanced user may change
coefficient Pan evaporation coefficient
justified and approved by reviewing jurisdiction
Clarification
Section 2.2.3 ‐ Guidance for Flow‐Related Standards
Noted the updated capability to model flows to
wetlands and analyze the daily and monthly
flow deviations per MR 8 in WWHM2012
wording was revised to reflect updates to WWHM since the last publishing of the SWMMWW
Section 2.3.2 ‐ Runoff Parameters
Added footnote to Table 2.3.1 allowing
modeling soils with a measured infiltration rate
of less than 0.3 in/hr as Class C
Clarification
Section 2.2.2 ‐ Assumptions Made in Creating the
WWHM
2012‐2014 SWMMWW Chart of Changes Revised April 2015
Location Change Reasoning or Comments
Section 3.1 ‐ Roof Downspout Controls
Updated wording that directs user to BMP
design guidance within the SWMMWW instead
of the Rain Garden handbook
Clarification
Revised subsection title from "Flow Credit for
Roof Downspout Full Infiltration" to "Runoff
Modeling for Roof Downspout Full Infiltration"
Clarification
revised sentence to clarify that clearance is
measured to the seasonal high ground water
table
Clarification
Revised subsection title from "Flow Credit for
Roof Downspout Dispersion" to "Runoff
Modeling for Roof Downspout Dispersion"
Clarification
Added modeling guidance where a dispersion
trench is used with a vegetated flowpath of 25
to 50 feet.
Clarification
removed footnote defining "Vegetative Flow
Path"
Added text to Emergency Overflow Spillway
section to ensure a min 1 foot of freeboard in
detention pond design
Clarification
Updated Landscaping section to refer to BMP
T5.13.Clarification
Added a reference to the Maintenance Tables
in Volume V, removed the Maintenance Tables
from this section
tables have been moved in an effort to consolidate and organize the SWMMWW
Chapter 3 ‐ Flow Control Design
Section 3.1.1 ‐ Downspout Full Infiltration Systems
(BMP T5.10A)
Section 3.1.2 ‐ Downspout Dispersion Systems (BMP
T5.10B)
Section 3.2.1 ‐ Detention Ponds
revised wording to read "volumetric flow rate
calculated using a 10‐minute time step"edit made to accurately describe the design criterion
Section 3.2.2 ‐ Detention Tanks
Added a reference to the Maintenance Tables
in Volume V, removed the Maintenance Tables
from this section
tables have been moved in an effort to consolidate and organize the SWMMWW
Section 3.2.4 ‐ Control Structures
Added a reference to the Maintenance Tables
in Volume V, removed the Maintenance Tables
from this section
tables have been moved in an effort to consolidate and organize the SWMMWW
Section 3.3.4 ‐ Steps for the Design of Infiltration
Facilities ‐ Simplified Approach
Sentence added "Testing should occur between
December 1 and April 1"Clarification
Updated SSC‐2 Ground Water Protection Areas
per Errata See 10/14/2013 Errata
Corrected reference cited in SSC‐6 Correction
Removed reference to the LID Technical
Guidance Manual for Puget Sound Ecology wants users to first consider the design guidance within the SWMMWW.
Revised wording to state design criteria "per
BMP T5.14A" instead of the Rain Garden
Handbook
Ecology wants users to first consider the design guidance within the SWMMWW.
Section 3.4.2 ‐ Description
Section 3.3.7 ‐ Site Suitability Criteria (SSC)
2012‐2014 SWMMWW Chart of Changes Revised April 2015
Location Change Reasoning or Comments
Section 3.4.2 ‐ Description
Added statement allowing infiltration through
the side slopes to be modeled for facilities with
side slopes 3H:1V or flatter
Clarification
WWHM Information and Assumptions ‐ Precipitation
Data
Revised text to state that WWHM2012 uses 15‐
minutes precipitation time series Clarification
Added statement that soils tested at less than
0.3 in/hr may be modeled as Class C soil.Clarification
Clarified that type D soil is generally modeled
as till and saturated soil category in WWHM is
to be used for wetlands
Clarification
Updated text that conflicted with information
elsewhere in the manual Clarification
Updated text that the Appendix C guidance was
developed before WWHM2012 became
available. WWHM2012 can model permeable
pavements directly.
Clarification
Added statements concerning adjustment of
LSUR, SLSUR, and NSUR by the model user Clarification
Added a paragraph explaining WWHM2012and
WWHM3 provides 2 additional land slopes, flat
and steep, to the existing moderate land slope
for modeling purposes
Clarification
WWHM Information and Assumptions ‐
Development Land Use Data
WWHM Information and Assumptions ‐ PERLND and
IMPLND Parameter Values
Appendix III‐B ‐ Western Washington Hydrology Model ‐ Information, Assumptions, and Computation Steps
WWHM Information and Assumptions ‐ Soil Data
for modeling purposes
Appendix III‐C
Added a "Note" that the guidance in Appendix
C was developed for use with WWHM3 before
WWHM2012 became available.
Clarification
Part 1 C.2.3 ‐ Partial Dispersion on Residential Lots
and Commercial Buildings
Clarified guidance for consistency with text
regarding modeling of partial dispersion
options.
Clarification
Part 1 C.10.1 ‐ Runoff Model Representation Added guidance regarding modeling
bioretention that has an underdrain Clarification
Part 1 C.11.1 ‐ Instructions for Roads on Zero to 2%
Grade
Added guidance regarding modeling permeable
pavement that has underdrains at the bottom
of base course
Clarification
Part 1 C.11.2 ‐ Instructions for Roads on Grades
above 2%
Added guidance regarding modeling permeable
pavement that has underdrains at the bottom
of base course
Clarification
Part 2 Downspout Dispersion ‐ BMP T5.10B Inserted guidance for downspout dispersion
modeling Clarification
Part 2 Bioretention ‐ BMP T7.30 Added modeling guidance on Bioretention with
underlying perforated drain pipes Clarification
Appendix III‐C ‐ Washington State Department of Ecology Low Impact Development Flow Modeling Guidance
2012‐2014 SWMMWW Chart of Changes Revised April 2015
Location Change Reasoning or Comments
S403 BMPs for Commercial Composting revised text to reflect updated regulations and
guidance Clarification
S411 BMPs for Landscaping and Lawn/Vegetation
Management
Revised S411 BMP bullet point to clarify use of
pesticides in Landscaping Clarification
S430 BMPs for Urban Streets deleted reference to Vol. V, Ch. 12 which no
longer has information on sweepers Clarification
S431 BMPs for Washing and Steam Cleaning
Vehicles/Equipment/Building Structures Revised text to reference updated guidance Clarification
Total Copper added to Table G.4 Copper overlooked in previous editions
Added note that the Interim Compost
Guidelines are no longer effective. Retained for
background info.
Clarification
Section 2.1 ‐ Step‐by‐Step Selection Process for
Treatment Facilities
Step 5: revised "urban growth management
area" to "urban growth area"Clarification
Revised "urban growth management area" to
"urban growth area"Clarification
Bioretention: removed text directing reader to
LID Manual for bioretention guidance. Text
now directs reader to Chapter 7 only. (Text
within Chapter 7 refers to the LID manual for
Clarification
Contamination in Street Waste Solids
Section 3.4 ‐ Enhanced Treatment Menu
Chapter 3 ‐ Treatment Facility Menus
Volume IV ‐ Source Control BMPs
Chapter 2 ‐ Selection of Operational and Structural Source Control BMPs
Appendix IV‐G ‐ Recommendations for Management of Street Wastes
Volume V ‐ Runoff Treatment BMPs
Chapter 2 ‐ Treatment Facility Selection Process
p
additional guidance)
Deleted: “The goal also applies on an average
annual basis to the entire annual discharge
volume (treated plus bypassed).”
Clarification ‐ See 10/14/2013 Errata
Bioretention: removed text directing reader to
LID Manual for bioretention guidance. Text
now directs reader to Chapter 7 only. (Text
within Chapter 7 refers to the LID manual for
additional guidance)
Clarification
Section 4.1.2 ‐ Water Quality Design Flow Rate (last sentence of section) Deleted reference to
an average annual performance goal Indefinite determination.
Section 4.1.4 ‐ Minimum Treatment Facility Size New section re minimum treatment facility size Additional guidance provided on the minimum treatment facility size.
Section 3.5 ‐ Basic Treatment Menu
Chapter 4 ‐ General Requirements for Stormwater Facilities
2012‐2014 SWMMWW Chart of Changes Revised April 2015
Location Change Reasoning or Comments
Section 4.6 ‐ Maintenance Standards for Drainage
Facilities
Updated Tables 21&22 with information from
LID O&M Guidance document, with note that
inspection and routine maintenance
frequencies are recommended only.
Guidance added per PCHB No. 12‐093c and ‐ 097c
Section 5.1 ‐ Purpose Added text clarifying that LID manual is for
additional guidance only.Clarification
Section 5.3.1 ‐ On‐Site Stormwater Management
BMPs
Added bullet under Competing Needs on local
codes Clarification
BMP T5.11: Concentrated Flow Dispersion Added modeling guidance for use of dispersion
trench with flowpath of 25‐50 feet Additional guidance for runoff modeling
BMP T5.12: Sheet Flow Dispersion Added modeling guidance for use of dispersion
trench with flowpath of 25‐50 feet Additional guidance for runoff modeling
BMP T5.13: Post‐Construction Soil Quality and Depth
Updated the compost specification
requirement to be consistent with the
Bioretention compost specification but allowing
use of biosolids
Corrected WAC reference, made clarifications
Revised Rain Garden Handbook reference to
specify 2013 version Clarification per PCHB No. 12‐093c and ‐ 097c
Added a design guideline concerning use of
composts Additional Guidance for rain gardens
Provided guidance for sizing rain gardens
serving lawn/landscape areas in addition to
impervious surfaces
Additional Guidance for rain gardens
Provided guidance for underdrains in rain Additional Guidance for rain gardens
BMP T5.14A: Rain Gardens
Chapter 5 ‐ On‐Site Stormwater Management
gardens Additional Guidance for rain gardens
updated the maintenance section to refer to
both the Rain Garden Handbook and the
Western Washington LID O&M Guidance
Document
Additional Guidance for rain gardens
BMP T5.14B: Bioretention
Provided guidance for sizing bioretention
facilities serving lawn/landscape areas in
addition to impervious surfaces
Additional Guidance for bioretention facilities
Revised guideline regarding the amount of
impervious area draining to a pervious area Clarification
Revised infeasibility criterion for permeable
pavement and roads re PCHB decision Revised to implement PCHB No. 12‐093c and ‐097c
Deleted the second sentence of the infeasibility
criterion addressing road sanding for snow and
ice, Per PCHB ruling
Deleted per PCHB No. 12‐093c and ‐ 097c
New text in regard to municipalities designating
areas as infeasible and the data required Clarification and additional guidance as directed by PCHB No. 12‐093c and ‐ 097c
BMP T5.15: Permeable Pavements
2012‐2014 SWMMWW Chart of Changes Revised April 2015
Location Change Reasoning or Comments
Revised 1st paragraph of "Design Guidelines"
section to clarify that LID Manual is for
additional guidance only, and that alternatives
adopted by municipalities must not conflict
with Ecology design criteria.
Clarification
Removed reference to the LID manual in the
"Base Material" section. The LID manual is
already referenced as additional guidance in
the opening paragraph.
Clarification
"Wearing layer": updated infiltration rate in
first sentence from 10 in/hr to 20 in/hr. The 10
in/hr rate was a typo and conflicted with
information given later in this section.
Clarification
Removed reference to the LID manual in the
"Wearing Layer", "Pervious Concrete", and
"Permeable Interlocking Concrete Pavement
and Aggregate Pavers" sections. The LID
manual is already referenced as additional
guidance in the opening paragraph.
Clarification
"Underdrains": Added a section regarding
underdrains affecting the status of permeable
pavements as LID BMPs
Additional Guidance for permeable pavements
added a reference to Table 22 within Table
452in Chapter 4 for maintenance guidance Additional Guidance for permeable pavements
BMP T5.15: Permeable Pavements
4.5.2 in Chapter 4 for maintenance guidance
BMP T5.17: Vegetated Roofs Added text clarifying that LID manual is for
additional guidance only.Clarification
Corrected section sub header name Clarification, the guidance is not only for residential projects
Corrected design requirements for residential
projects text for clarity Clarification
Revised "urban growth management area" to
"urban growth area"Clarification
Replaced Figure 7.4.1 Clarification
Added Figure 7.4.1b Clarification
Added Figure 7.4.1c Clarification
New text in regard to municipalities designating
areas as infeasible and the data required
Additional guidance to be consistent with directive of PCHB No. 12‐093c and ‐ 097c for permeable
pavement
Determining Bioretention soil mix infiltration
rate: Updated Ksat Safety Factor language for
consistency with WWHM.
Clarification
BMP T7.30: Bioretention Cells, Swales, and Planter
Boxes
BMP T5.30: Full Dispersion
Chapter 7 ‐ Infiltration and Bioretention Treatment Facilities
2012‐2014 SWMMWW Chart of Changes Revised April 2015
Location Change Reasoning or Comments
Design criteria for bioretention ‐ updated text
to clarify that LID manual is additional guidance
only; under "curb cuts for roadside, driveway,
and parking lot areas" ‐ removed reference to
LID manual because it is already referenced in
the design criteria opening paragraph.
Clarification
Added text to "ponding area" section
describing surface areas when designing for
MR5
For consistency w/Min. Requirement #5 and recommendation for size increase if draining pervious area
Default Bioretention Soil Media: Multiple
changes to the compost specification; and to
incorporate a specification for fine compost
Changes needed to be consistent with updated WAC 173‐350‐220; Incorporated fine compost spec. to
delete reference to LID Manual
Design Criteria for Custom Bio Soil Mixes:
Added text clarifing that custom mix does not
need to meet gradation specification
Clarification
Soil Depth: Removed guidance for 24" BSM
depth Additional Guidance for bioretention facilities. Local monitoring indicates phosphorus loss from media.
Underdrain (optional): Added guidance for
modeling bioretention with underdrains Additional Guidance
Added text to clarify that LID manual is
additional guidance only.Clarification
Added statement that compost shall not
include biosolids or manures Clarification
Soil Design Criteria: Emphasized exclusion of
biosolids and manure from compost used for ClarificationBMP T7.40: Compost‐Amended Vegetated Filter
BMP T7.30: Bioretention Cells, Swales, and Planter
Boxes
CAVFS
Maintenance: deleted bullets per Errata Clarification ‐ See 10/14/2013 Errata
BMP T8.30: Linear Sand Filter Additional Design Criteria for Linear Sand
Filters: corrected text Correction
BMP T8.40: Media Filter Drain Grass Strip: restricted compost to that used for
Bioretention soil media Clarification
revised wording to read "volumetric flow rate
calculated using a 10‐minute time step"edit made to accurately describe the design criterion
Soil Criteria: SC‐15: Restricted compost to that
used for Bioretention soil media Clarification
BMP T9.40: Basic Filter Strip Corrected error in figure 9.4.9 Correction
Section 11.6 ‐ Design Criteria ‐ General
Considerations Corrected Schueler citation from 1990 to 1992 Correction
BMP T11.11: Coalescing Plate (CP) Separator Bay Clarification in design flowrate variable Clarification
Strips
BMP T9.10: Basic Biofiltration Swale
Chapter 9 ‐ Biofiltration Treatment Facilities
Chapter 11 ‐ Oil and Water Separators
2012‐2014 SWMMWW Chart of Changes Revised April 2015
Appendix I
Updated Capital Improvements Plan
Stormwater
Capital Improvement Program
2019-2028Updated CIP with $6 surcharge and development fee
Project Title Total Project Cost 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029-2039
Stormwater General Projects
Stormwater General Repairs/Upgrades 120,000.00$ 50,000.00$ 50,000.00$ 50,000.00$ 50,000.00$ 50,000.00$ 50,000.00$ 50,000.00$ 50,000.00$ 50,000.00$ 50,000.00$
Capital Projects
16th Street - Sheridan Street and Landes Street 210,000.00$ -$ -$ -$ 60,000.00$ 150,000.00$ -$ -$ -$ -$ -$ -$
Hancock Street and 32nd Street 180,000.00$ -$ -$ -$ -$ -$ -$ -$ -$ -$ -$ 180,000.00$
Center Street - San Juan Avenue to Olympic Avenue 400,000.00$ -$ -$ -$ -$ -$ -$ 125,000.00$ 275,000.00$ -$ -$ -$
12th Street Right-of-way, Logan Street and 14th Street -$ -$ -$ -$ -$ -$ -$ -$ -$ -$
Inflow/Infiltration Removal - Lawrence Street at the intersections of Polk Street, Taylor
Street and Tyler Street 850,000.00$ -$ -$ -$ -$ -$ -$ -$ -$ -$ 300,000.00$ 550,000.00$
Rainier Street Regional Stormwater Project 808,000.00$ 808,000.00$ -$ -$ -$ -$ -$ -$ -$ -$ -$ -$
Logan Street Stormwater Pond Overflow 60,000.00$ 10,000.00$ 50,000.00$ -$ -$ -$ -$ -$ -$ -$ -$ -$
Basin 8 - Wetland Overflow (Hastings Pond)250,000.00$ -$ -$ -$ -$ -$ -$ -$ -$ -$ -$ 250,000.00$
Basin 7 - Wetland Overflow (Glasbell Property)300,000.00$ -$ -$ -$ -$ -$ -$ -$ -$ -$ -$ 300,000.00$
Basin 5 - Wetland Overflow (Behind Blue Heron Middle School)-$ -$ -$ -$ -$ -$ -$ -$ -$ -$ -$ -$
Basin Planning
Basin Planning Studies 250,000.00$ -$ -$ -$ 50,000.00$ -$ -$ -$ 50,000.00$ -$ -$ 150,000.00$
Existing Street Stormwater Improvements
Major Collectors and Minor Arterials 600,000.00$ -$ -$ 300,000.00$ -$ -$ -$ -$ -$ 300,000.00$ -$ -$
Local Access Streets 200,000.00$ -$ -$ -$ 100,000.00$ -$ -$ -$ -$ -$ 100,000.00$ -$
Stormwater Management Plan Updates
Stormwater Management Plan $130,000.00 $30,000.00 -$ -$ -$ -$ 100,000.00$ -$ -$ -$ -$ -$
968,000.00$ 100,000.00$ 350,000.00$ 260,000.00$ 200,000.00$ 150,000.00$ 175,000.00$ 375,000.00$ 350,000.00$ 450,000.00$ 1,480,000.00$
Debt Service Payments
Total Per Year
Copy of REVISED 10-year Stormwater CIP 2019-2029.xlsx 1/18/201911:15 AM