HomeMy WebLinkAboutAL Pettygrove Block 18 Lots 5 & 6 - Geology Hazard Assessment - 2006.03.17STRATIJM GROUP
1451 Grant Street, Bellingham, WA 98225
Phone (360) 714-9409
March 17,2006
Len and Joanne Tyler
P.O. Box 155
Port Townsend, WA 98368 er:iJ * 1\_l l_. I I
Re Geology Hazard Assessment
1500 Jackson Street
Tax Parcel 984601806
Port Townsend, Washington
Dear Mr. and Ms Tyler:
It is our understanding that you plan to remodel a portion of the residence at 1500 Jackson Street
and that this remodel will include an addition to the back portion of the home. We visited the
property in February 2006 and March 2006 to evaluate the slope stability of subject property as
well as investigate the soil conditions for foundation bearing capacity. Our site inspection
included evaluating the criteria set forth in City of Port Townsend's Environmentally Sensitive
Areas (ESA) Ordinance, PTMC 19.05. Based on our inspection of the property and vicinity, the
current residence is not at risk from being impacted by slope failures or erosion.
The addition proposed to be constructed on the back of the home will not be at risk from
landslides, slope failures or erosion. The remodel as proposed will not create instability or harm
to other properties or public resoruces as long as the recommendations made in this report are
followed.
GENERAL GEOLOGY
Northwestern Washington has been occupied by continental glaciers at least four times during
the Pleistocene Epoch (1.6 million to 10,000 years ago). During these glacial and accompanying
iirterglacial periods, the underlying bedrock was deeply eroded. The Surficial Geoloeic Map of
the Port Townsend 30- b)' 60-Minute Ouadrangle. Puget Sound Reeion" Washington (Pessl,
Dethier, Booth and Minard, 1989) indicates that the subject property is underlain by glacial till.
Site observations on the subject property and in the vicinity are consistent with the above-
described mapping. However, the lower slopes of the shoreline bluff located approximately 250
feet to the northeast of the subject property are underlain by preglacial deposits. The till
underlying the subject property consists of a poorly sorted mixture of rock fragments deposited
directlyby glacial ice during the last ice age. The pebbles, cobbles and boulders are firmly
embedded in a matrix of finer material consisting of a variable mixture of clay, silt and sand.
Overall, the till at the site is very hard and compact. The till soils at the site consist of silty sand
with gravel.
March 17, 2006
1500 Jackson Street, Port Townsend, WA
Geology Evaluation
The preglacial deposits on the lower half of the shoreline bluff 250 feet northeast of the subject
property consist of clay, silt, and sand with sand being the predominant unit. These deposits
appear to be advance outwash deposits deposited by meltwater from the advancing glacial ice
just prior to the last glacial period approximately 20,000 years ago.
SPECIFIC SITE OBSERVATIONS
A site plan sketch of the subject property is attached to this report, which shows pertinent
information regarding the site.
The subject property is located north of the intersection of Jackson Street and McKinley Street.
The property generally slopes to the northeast towards a steep shoreline bluff located
approximately 250 feet northeast of the property. The existing home on the property is a single
story residence with a full daylight basement. The upper, front yard along Jackson Street slopes
gently towards Jackson Street with the northern comer of the yard sloping towards McKinley
Street. A paved driveway from McKinley Street is located on the southeast side of the property.
The lower back yard consists of a nearly level lawn area and then a slope down to the property
northeast of the subject property. The slope down to the northeast is approximately 12 feet high
and slopes down at an angle of approximately 25 degrees. The width of the level lawn area
between the home and the slope is 2I feet. No indications of slope movement are present on the
slope or elsewhere on the property or in the vicinity.
No areas of water seeps or vegetation indicating seasonal water seeps were observed anywhere
on the property or on slopes in the vicinity of the property.
A total of 4 test its were excavated at the site and soils encountered were classified in accordance
with the Unified Soils Classification System (USCS). Edited tabulated test pit logs are attached
to this report together with a USCS chart explaining soil descriptions. Soils on the property
consist of silty sand with gravel in a very compact condition. The soil is a fairly coarse grained
glacial till.
Storm water runoff from the southwest side of the roof is discharged onto the ground within the
lawn area on the southwest side of the home. A heavy rainfall had taken place the day before our
initial site visit in early February 2006 and the previous month and a half had been very wet. We
excavated hand dug test pits at both down spout discharge points. No saturated soils were
encountered and there was no evidence of surface water flow across the lawn area or anywhere
on the property. It appears that storm water readily infiltrates into the ground at the site.
2
Stratum Group File: 1.6.06
March 17,2006
1500 Jackson Street, Port Townsend, WA
Geology Evaluation
Another gutter down spout discharges storm water onto the gound surface immediately adjacent
to the driveway. No evidence of surface water flow is present at that location either. Storm water
from the driveway sheet flows to McKinley Street. The roof down spouts on the northeast side of
the house discharge via a pipe along the curb of McKinley Street. Storm water from McKinley
Street flows down into a catch basin at the intersection of McKinley Street and Clallam Street.
The storm water eventually flows to a discharge along the shoreline southeast of the subject
property.
Port Townsend Geologically Hazardous Areas Evaluation
As per Port Townsend's Code 19.05.100 B 1 through 6 the following classification criteria were
evaluated to determine if the subject property is located in a geologically hazardous area. Based
on this evaluation and the conditions described in the above sections, the slope along a portion of
the northeast side of the lot is considered a geologic hazard area under 19.05.100 B 5.
19.05.10081: Any area containing soil or soil complexes described or mapped within the United
States Department of Agriculture/Soil Conservation Service Soil Surveyfor Jefferson County as
having a severe to very severe erosion hazard potential.
Soils underlying the upper part of the bluff site consist of very compact, silty sand with gravel
based on test pits and site observations. These soils are not prone to severe erosion potential.
19.05.10082: Any area with slopes greater than I5 percent with impermeable soils (typically silt
and clay) frequently interbedded with granular soils (predominantly sand and gravel); and
springs or ground water seepagefrom perched water tables or potentially unstable slopes.
The overall slope on the site is greater 15 percent. However, there are flat areas and areas that are
steeper. Soils on the site and on the slopes are uniformly silty sand with minor gravel and no
areas of springs or water seepage is present on the slope of the subject property or other nearby
slopes. We performed slope stability analyses of the slope to demonstrate that the slope is stable
under both static and dynamic earthquake loading conditions. The results of the slope stability
analyses are attached to this report.
3
SFatum Group File: 1.6.06
March 17,2006
1500 Jackson Street, Port Townsend, WA
Geology Evaluation
19.05.10083: Any area potentially subject to mass movement due to a combination of geologic,
topographic, hydrologicfactors, but not limited to those areas mapped or described by the Soil
Conservation Service, Washington State Department of Ecology, Department of Natural
Resources or U.S. Geologic Service. The classification may be based on performance standards
ratlter than mapping.
No indications of shallow rapid mass wasting are apparent anylvhere on the subject.property or
on any other areas in the near vicinity of the subject property (see attached slope stability
analyses). Mass soil movement is present on the shoreline bluff slope located approximately 250
feet northeast ofthe subject property.
19.05.10084: Any area potentially unstable as a result of rapid stream incision, stream bank
erosion or undercutting by wave action.
No areas on the subject property are subject to rapid stream incision or stream bank erosion.
Undercutting by wave action is taking place along the base of the shoreline bluff slope. The top
of the shoreline bluff slope is located approximately 250 feet northeast of the subject property.
19.05.10085: Any slope of 40 percent or steeper.
Portions of the slope along the northeast side of the property are slightly greater than 40%. This
steep slope is approximately 12 feet high over a horizontal distance of approximately 25 feet. The
slope is approximately 25 degrees or 460/o. The height, distance and slope were measured in the
field using a tape measure and clinometer. The attached slope stability results show that the
slope is stable with respect to the proposed setback.
Port Townsend Municipal Code 19.05.020 defines steep slope as"means any area with a
combination of slopes greater than I5 percent with impermeable soils, ground water seepage, or
potentially unstable slopes; also, critical slopes over 40 percent. Critical slope is determined by
measuring the vertical rise over any 40-foot horizontal runfor a specific area tltat results in a
percentage of 40 or more. The critical slope hazard area includes the area of land that extends
for l0feetfrom the top and toe of the slope."
Based on the 19.05.100B5 the 40 percent slope area on the property is a geologically hazardous
area. However, it is not considered a critical slope, as the height of the slope is approximately 12
feet over a horizontal distance ofapproximately 25 feet (see attached slope stability results).
4,
Sffatum Group File: 1.6.06
)
March 17,2006
1500 Jackson Street, Port Townsend, WA
Geology Evaluation
No indications of slope movement are present on the slope or adjacent to the slope along the
northeast side of the property.
19.05.10086: Areas subject to severe risk of damage as a result of earthquakes, slopefailure,
settlement, soil liquefaction orfaulting. These areas are identified by the presence of poorly
drained soils (greater than 50 percent silt and less than 35 percent coarse material) loose sand
or gravel, peat, artificialfill and landslide materials or soils with a high organic content.
The site is not underlain by potentially liquefiable soils and compact glacial till is not typically
susceptible to earthquake induced mass movement. We performed slope stability analyses under
earthquake loading (30% of gravity) and the slope is stable.
CONCLUSION AND RECOMMENDATIONS
As noted above a portion of the property does have a steep slope. This steep slope is
approximat ely 12 feet high over a horizontal distance of approxim ately 25 feet. The slope is
approximately 25 degrees or 460/o. Port Townsend Critical Areas Ordinance considers any slope
40Yo a geologically hazardous area. The proposed addition to the house will not be located on the
steep slope and our slope stability analyses indicate that the addition will be stable under both
static and dynamic loading conditions.
The proposed addition will be located 12 feet from the top of the steep slope. No development is
proposed within the geologicallyhazardous area. It is our opinion that the steep slope on the
northeast side of the property is stable and as such poses no risk to the existing home or to the
addition to the home as long as our recommendations are followed. The silty sand with gravel
glacial till underlying the property is very compact and stable and is capable of maintaining
vertical slopes for long periods of time as evidenced on nearby steep upper slopes of the
shoreline bluff northeast of the subject property.
Port Townsend Municipal Code 19.05.100D outlines performance standards for development
associated with geologically hazardous areas. As no development will be taking place on the
steep slope, the applicable section is 19.05.100D.f.iii which states "All proposed development
occurring within 50 feet of the top of an inland bank of greater tltan 40 percent that exceeds a
vertical height ofat least I0feet shall require a geotechnical report. This area shall hereinafter
be referred to as the 'inland bank management zone.' " This report fulfills this requirement.
5
Stratum Group File: 1.6.06
)
March 17,2006
1500 Jackson Street, Port Townsend, WA
Geology Evaluation
Port Townsend Municipal Code 19.05.100E establishes buffers and setbacks. This section states
that the minimum buffer for inland banks as 25 feet. For existing lots a steep slope buffer less
than 25 feet may be permitted provided that the geotechnical report concludes that doing so
would not result in an increased risk to people or property or impacts to the environmental
processes.
Recommendations
Setback
As noted above the subject property contains a potentially geologically hazardous steep slope.
The proposed remodel will avoid this slope. A minimum of aZ:I slope from the base of the
foundation to the slope should be provided in order to prevent differential settlement. The proposed
remodel foundation will be setback 12 feet from the top of the steep slope. This distance is more
than adequate from a slope stability perspective.
Storm water
Development of the site can be accomplished with typical foundation work. Roof gutters and the
down spout system on the northeast side of the home should either direct water into an approved
storm water system or should be infiltrated into the ground using a level spreader placed in such
a manner as to avoid concentrating surface water discharge.
Soils underlying the site are permeable despite their very compact condition. This is evident from
the lack of surface water flow and saturation of soils at the existing down spout discharge points
on the southwest side of the home. At present storm water on the northeast side of the existing
home is directed via tightline to McKinley Street where it ultimately enters a City of Port
Townsend storm water system. The increase in volume to flow from the small addition to the
house will have minimal impact on the current discharge rate to the system from the home site.
The addition will only cover a small area of lawn and the existing paved driveway that sends
storm water onto McKinley Street. If this volume increase is acceptable to the City, we
recommend continuing sending storm water from the northeast side of the home into the storm
water system.
6
Stratum Group File: 1.6.06
March 17,2006
1500 Jackson Street, Port Townsend, WA
Geology Evaluation
Other Recommendations
No grading or filling should take place on the steep slope. No debris or yard waste should be
placed on the steep slope. Yard waste eventually builds up and can form a wet unstable mass that
will slide down the slope damaging the slope and increasing the rate of slope failures.
F o u n d atio n R e co m m en datiort s
We conclude that the site is suitable for development of the type proposed, provided our
recommendations are followed. Conventional, shallow column (spread) and continuous footings
will provide adequate support for the proposed addition. The test pit explorations revealed adequate
foundation support to the depth of the explorations. Our conclusions and recommendations assume
a relatively light structure that will not be particularly settlement sensitive.
We recommend that the buildings be supported on isolated column (spread) and continuous
footings founded on undisturbed native silt soils or a minimum of 6-inches of compacted structural
fiIl. If founded on structuralfill, the fill should extend beyond the edges of the footings a distance
equal the thickness of the structural fill. Bearing soil should be firm and non-yielding and free of
standing water prior to pouring concrete. Bearing soil that is disturbed during foundation
excavation should be removed. All continuous and isolated column footings should have minimum
widths of 16 and 24 inches, respectively, and should be founded a minimum of 18 inches below the
lowest adjacent final grade to provide adequate frost protection. Each structure should be placed
entirely on native till soils or entirely on structural fill to minimize differential settlement.
All shallow footings supported on properly prepared subgrade may be proportioned using a net
allowable bearing pressure of 2,000 psf. The term net allowable bearing pressure refers to the
pressure that can be imposed on the soil at foundation level due to the total of all dead plus live
loads exclusive of the weight of the footing or anybackfill placed above the footing. These values
maybe increased by one-third for transient wind or seismic loads.
We recommend that a geotechnical engineer or engineering geologist from our office inspect all
excavations and the compaction of structural fill prior to construction of footing forms.
7
Stratum Group File: 1.6.06
March 17,2006
1500 Jackson Street, Port Townsend, WA
Geology Evaluation
Settlement of foundations depends on foundation size, depth, and bearing pressure, as well as the
strength and compressibility characteristics of the underlying soil. Assuming construction is
accomplished as recommended above and for the loads anticipated, we estimate the total settlement
of foundations should be small (less than about one inch). Our estimate assumes a maximum sized
footing utilizing a maximum allowable contact pressure and also assumes a typical consolidation
coefficient for the foundation soils. This settlement estimate assumes relatively light loads with
continuous footing widths not to exceed 2 feet and column footings not exceeding 3-foot by 3-foot.
Our test pit exploration revealed that the native silt and clay soils are overconsolidated and, as such,
much of the settlement should take place relatively rapidly, as the loads are applied.
Stratum Group appreciates the opportunity to be of service to you. Should you have any
questions regarding our assessment please contact our office at (360) 714-9409.
Sincerely yours,
Group
h.
Dan McShane,L.G., M.Sc.
Licensed Engineering Geologist
Western Geotechnical Itants,Inc.
, P.E.
Geotechnical Engineer
Attachments: USCS Chart of Soil Descriptions
Log of Test Pits
Slope Stability Analyses Results
6
8
rrim,l Mc*9hene
6
Stratum Croup File: 1.6.06
aIrnWhorii1.---&?ETO23't ttl'6er.---,lAV;-,f't{3t 6lllt1d,!-+-,^(t)pSUBJECT PROFERTYBt'l 34II!ftIn{LAl,, .rlInouF.6-,t2 -.Point" *utLb,ld.a-6,:a.(FFtgur€ i-. Site viciflily lvldFiL22"4E'00" wL??o45'00" w1?2046'00" w122"00" wil -5 -- 1 vlil:F-----:=:-....-...1:--:.-".€:...-il itljfl itll 'J i{;{J --________-_-_ lt}i fiJtrlflS-:#i--- _- i-ffi:r--i:q--r::r_::-Map cnated with ToFol@ 02003 I'letionni Geographic (www.rniionalgeographic.conr/topo)wG-qE4 l2?"44'00" wz.OObOoE+:oOLUOrn+l aaoif lffl'tll liJl_44 T/ +U122a47'00" \n/=(fiOoffi.f,i.m:OOioom+:tO{fDcorHf /MNIrrr""WGS84 1Z?O00" w
YJeadr \
:
-'-/l
,/'^1 5hr.
i)riu"Leuel
Law4 -4
flout5c
d**sy'*i-+--*)
Leve I
ti,i*
f a
a'#i^t
T
.E llO,!
Eroo Bt ul
d,ft
tt4
q
f
5t#u
A)5+ -f
\I l*t\^l
t^
kCr
9"^lu aqol lata*i*r dlty'/Dx r,-.ot'*
Strat
2{'
Figu re 2
Site Sketch PlonGroup
Attachments
Log of Test Pits
USCS Chart
Slope Stability Analyses
Attachments
Log of Test Pits &
Log of Test Pits File: 06 47 2
Test
Pit
No.
Depth
Interval
(feet)
USCS
Class.
Soil Description Sample
No./
Depth
(feet)
Water
Content
(%)
Pocket Pen.
(Kg/sq. cm)
TP-1 0.0-0.7 OLlSM Dark Brown sandy
organic SILT to silty
SAND with occasional
.gravel and frequent
roots (wet, soft)
(topsoil)
0.7-r.2 SM Brown gray mottled
silty SAND with some
gravel (moist, very
compact) (glacial till)
0'1 llr 10.9%4.s+@1.0'
Test Pit terminated on 612106 at 1.2 feet.
No groundwater encountered.
No instrumentation installed.
Test pit backfilled upon completion.
o Test Pit terminated on 612106 at 1.0 foot.o No groundwater encountered.o No instrumentation installed.o Test pit backfilled upon completion.
Log of Test Pits File:06 47 2
Test
Pit
No.
Depth
Interval
(feet)
USCS
Class.
Soil Description Sample
No./
Depth
(feet)
Water
Conte
nt (%)
Pocket Pen.
(Kg/sq.
cm)
TP-2 0.0-0.8 OL/SM Dark Brown sandy organic
SILT to silty SAND with
occasional gravel and
frequent roots (wet, soft)
(topsoil)
0.8-1.0 SM Brown gray mottled silty
SAND with some gravel
(moist, very compact)
(glacial till)
2-Ut.0 t2.r%45+@1.0,
Log of Test Pits File:06 47 2
Test
Pit
No.
Depth
Interval
(feet)
USCS
Class.
Soil Description Sample
No./
Depth
(feet)
Water
Content
(%)
Pocket
Pen.
(Kg/sq
cm)
TP-3 0.0-0.7 OL/SM Dark Brown sandy organic
SILT to silty SAND with
occasional gravel and
frequent roots (wet, soft)
(topsoil)
0.7-l.s SM Brown silty SAND with
some gravel (moist,
relatively compact)
(weathered till)
1.5 SM Brown gray mottled
silty SAND with some
gravel (moist, very
compact) (glacial till)
(refusal at 1.2 ft.)
4.s+@r.0'
Notes:o Test Pit terminated on 612106 at 1.5 feet.
o No groundwater encountered.o No instrumentation installed.
o Test pit backfilled upon completion.
l
Log of Test Pits File:06 47 2
Test
Pit
No.
Depth
Interval
(feet)
USCS
Class.
Soil Description Sample
No./
Depth
(feet)
Water
Content
(%)
Pocket
Pen.
(Kg/sq,
cm)
TP-4 0.0-0.9 OL/SM Dark Brown sandy organic
SILT to silty SAND with
occasional gravel and
frequent roots (wet, soft)
(topsoil)
0.9-1.1 SM Brown gray mottled silty
SAND with some gravel
(moist, very compact)
(elacial till)
4-Ut.l 133%45+@r.0'
Notes
o Test Pit terminated on 612106 at 1.1 feet.
o No groundwater encountered.
e No instrumentation installed.o Test pit backfilled upon completion.
Key.3o Test PIC Logs Uetng lhoUnlfled Solt Classlflca0lon Sys0emiIt!rlTTACAL DEgCflFIrcS{glfttl,-GflDt0 CrFAltUL GiAYIt-S/t tDuftnas. ullta on rlo 'lt3P@N-Gnro$ ciA\ctt ctefr-q^'o urMt3. utnl or mnf,t3l{lv ct^Ytls. ce^rel-$ro-sr,ru$uttcu$l Gi^\,tta GtAvtt-sro-cuYtallt ic3tttt-ofl^Dto sso3. ci^vtrlY3ros.urumEtw3tooitr-Gi^oto slros. otAvt[rsrxot ullte oi x, tutstl rtr gnoa $r.D-cuY urtlntsmrc^xrc tt t3 rr{, vt r nrfsrxtls, nocr trogn. sr.n mcuYar fH[ s^t03 m cutEtslll m]B svor q^srrciDwncllc cull ot totr to lldwPt 3tc[Y, cf,^-t'E(Y C|,A|Sffi q^rs. ntn crals. rt8oml,lE sttt aat oictttc SrtYct^Ys of rot Pl..stlotrrloncr{c 3us. IE^ctqrs otu^lou^ctqrs t$t ss 'dsrtt sor3uoecl'lc ct^Ys l,' ]IoxP! imtw. t^t cl YsoFcrArc cutt ol l|tuux to l*ltn.r$rcfi. oroa.c st$iP€Al. tilfl1,l, Silnp s(nstror ORGAr Goiltems*il'lLETTEN8YM80t-qwGPqMGCswSPSMscMLCLOLMHCHOHPTGRAFIIgnlBON-r....;:.., ..i. -.-:- rlfrhrQR DMSlOl.lSCLEAN GRAVETS(un]E or romt€s,<5:GRAVELSWIIH FINES(^rPrtcilq.t Alollll6 tr[3l< l2tCLEAN SAI.IOS(unu of, tlofDesl<5tsAl.tDswlITI F]NES(rrPr(cu[t aouiltof rrt3)<t2tsttTsANDcIAYStolrp trllItlt rxrr 50SILISANDCTAYSrouo tlt!8[Al[E rlura !aHTGHLY ORGAI{|C SOTLSGRAV€LANOCRAVELTYsortsIoat tlufi soi ofo0 tst tr^cttoxlllltrto otr(,. a stfvtSANDANDSANDYsorLsCOA,RSEGRXNEOsortsFINEGRAINEDsorrslstUNIFIED SOIL CLAS$IFICATION CHART (USCS)GRADATION CHART. U.S. S!r,NOARO o Ct tlR SOlr Rt OpCxtNCS5-r2Z FTNES (SILI & CtAy) OUAL clissPLASTICITY CHARTUOU|0 LrMrT50fuuEIEF--- ol0 20 Jo ao00 904t8SaltsprlngsDrlveaFerndgle,wA 98248380-2507PARTICL€ SIZELIMIIsrflrf sltf,.o,ro,ll/1' tJolfrUPPTult urtreco..22.(xtt.t0t9tt6?J0..t9la.astwf sltf,z@,.b,lo11 ,tlf oflfrlfi.Lll,rEltRs.or.o.a22.Ooa.16l9t,c.2JO{.6ilATERUL SIZESANOrINEMEDIUM-COARSEGRAVELFINECOARSECOEBLESEouLDeRS,/9OHotMH,yu4IdctlrLotOLL/'zcH-ML,Phona380-2507aFax\_)A:TESI PITS
Slope Stability Analyses
We performed stability analyses of the most critical natural slope section based on
measurements taken at the time of our site investigation. Both static and seismic loading
conditions were analyzed and the seismic analyses utilized a maximum pseudo-static
earthquake load of 0.3 g.
For the analyses we assumed the following engineering properties.
Silt with Trace Gravel
Unit Weight
Cohesive Strength
Angle of Internal Friction
.... 130 pcf
.... 250psf
.... 34 degrees
To facilitate our analyses, we used the computer program GSLOPE. The program uses
Bishop's Modified Method of slices and a limiting equilibrium approach to determine the
minimum factor of safety against failure. The program determines the critical failure
surface and the resultant factor of safety for the slope configuration, soil unit weights and
strengths, ground water location, and seismic loading. The results of the analyses are
summarized below.
As the results show, the slope is stable under both static and dynamic loading conditions
The graphical results of the analyses are attached.
File:06 47 2
Loading Conditions Computed Safety Factor Target Safety Factor
Static 2.48 1.5
Dynamic t.4s 1.1
Phideg34PiezoSurf.0Ru0Western Geotechnical - Ferndale WA .-Jefferson CountyHouse Setback - Static Stability-20-10-0Glacial Till10-_lf-rIJF!z,/l\-jF =2.484L__l12feeI20-)0-I0Gamma Cpcf psf130 2504t1120O67:56:17 AM C:\DOCUME-1\TED\DESKTOF\0A'71.GSL Westem ceotechni{:at - Femdale WA F =2.48450100
Gamma Cpcf psf130 250Ru0Phideg34PiezoSurf.0Westem Geotechnical - Ferndale WA' Jefferson CountyHouse Setback - Dynamic Stability-20- .10)GlacialTillSeismic coefficient = 0.3020-10-_lt--T-I-Jl-rlzx-lF = 1.M7L12feel)0--0I04/112006 7:56:56 AM C:\DOCUME-1\TED\DESKTOF\06471 -GSL Wedem certechnicd - Femdate WA F = 1.44750100
Tyler Stormwater
Jan H
Plans
opfenbeck
Examiner/Permit Coordinator
Subject: Tyler Stormwater
From: "Jan Hopfenbeck" <jhopfenbeck@cityofpt.us>
Date: Tue, 25 Jul2006 16:58:22 -0700
To: "Rick" <rharch@premierl.net>
CC: "Alex Angud" <aangud@cityofpt.us>
Rick,
As Alex Angud was in the field, I spoke to Leonard Yarberry, DSD Director, about your stormwater
question on the Tyler residence. I explained that we had received the geology report in May and that you
had done due diligence in asking questions about stormwater management and discharge. I recounted
your conversation with Alex and then the follow-up with me at a later date to verify that the stormwater
could be handled as recommended in the report i.e., directing the increased flows into McKinley and
ultimately to the catch basin at Clallam. I informed him that Alex at that time had approved of the McKinley
Street discharge both directly to you and then to me when I verified with him (Alex).
Mr. Yarberry stated that the City would honor the City's previous approval of the geologist's
recommendation for discharge to McKinley Street as the increased flows appeared to be minimal in
comparison to that of a new development. I subsequently had a chance to speak with Alex when he
returned from the field and he also indicated that the design could still direct the flows to MicKinley. As
such, strict compliance with the 2005 DOE Stormwater Manual provisions to retain all stormwater on site
would not be applicable for your project.
Joanne Tyler was in this afternoon also asking about the stormwater design. As I do not have an e-mail
address for the Tylers, would you please pass this information along to her?
Please call if you have additional questions.
Regards,
Jan
City of Port Townsend
Developmenf Seryices Department
250 Madison Sfreef Sutfe 3
Port Townsend, WA 98368
Phone: (360) 379-5080
Fax: (360) 344-4619
j h o pf e n b e c k@ci tyof pt. u s
Di-lr * i
I
itl u,t dt;-n tf o'b
'+o be d q i.* l,'* cl
+ d-o"^ui'/o ( A(t)
f'tclz,,hq C re" At.0
1o catch ettto: ro:07 AM
ba'rln tV C ["ll*t- S /.
lofl