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HomeMy WebLinkAbout1994.02.00 - Campbell PUD Stormwater Management Plan and Design Narrativen F ; FENGINEERING LAND SURVEYING DEVELOPMENT CONSULTING Prepared for CAMPBELL O{STruJcTIcn{ STCRIiIATER Iv1A'IIAGEMENT Pl-At{ and DESIq{ MRRATIVE P.0. Box 2199 . 1007 North Fifth Avenue Se' 0ft d-I;"(- *\t"-,,,* \*Je*{-"v,- )" g,\ ,q*t 4.,/----------------* -".e-"'.- {**-*o.- i.- r*-.4 \."{..}..,. {"*\\l P-,'A JACfiMAN STREgf DffENSICT'I h I ExPsEs g-25-q February' 1994 z -L2-q9 cr rrENrs STORIVITATER MANrcEMENT PLAAI PROJECT OVERVIEIU I . @ALS OF EROS lC['l @['ITROL PL$'l II. CENERAL PROVISICNS Protection of ExPosed Soil t. Minimize Disturbance of Vegetation . 2. Minimize the Length of Time the Soil 3. Ensure Prcrpt Revegetation of Distur prading Limits. Frotection of Adiacent Properties A. B. c. is Unprotected bed Areas I 2 3 4 Crassy Swales lnterceptor Swales Interceptor DitchesSiltFencing ... Phasing of Construction . . Steepness of SloPes . . I 2 2 2 3 T 3 3 4 4 4 4 5 5 5 5 6 6 6 7 8 8 8 9 0 0 ll Release of Offsite Flows . . Stabilization of Erosion Control and Stornnrater Channels . Storm Drain Inlet Protection . Underground Utility C-onstruction . . Construction Access Routes . - Renrcval of Tenporary Erosion Control Purpins/Decatering of Trenches Control of Toxic Substances Petroleun Spills Maintenance I I I. SPECIAL PROVISICI.IS D E F G H J K L M N o P Terporary Facilities JactsrBn Street Phasin8/Timing Offsite SanitarY Sewer Main Detention Pond IV. PERMANENT WATER qIALIfi ACNTRON- FACILITIES V. PERMANENT WATER qIAAITITY @VIRON- DESICN MRRATIVE S@PE STREET SAIIITARY SEIuER WATER STCRM SEIUERS STCRMTATER DETENTIO'I EROSICN CCNTROL A B c I I . ll I I I 2 2 3 3 STORIITATER IIAI.IACEMENT PI.AI.J for JACKMAN STREET DfiENSIg\ TROJF.CT OVERV IHV This project consists of the construction of a one btock extensiorr of Ja<:lourt Street in the City of Port Townsend. This erosion control plan was prepared to address construction activ.ities necessary to ccrplete this work. This plan also includes elernents intended to cover the developnent of hqnes on the lots fronting on the newly constructed section of Jaclsran Street. If this plan is followed during the developnent of those lots, no additional erosion control plan(s) should be necessary. If it should be necessary to terminate the protective measures provided for in this Plan, snall Parcel erosion control plans will be necessary for develogrnnt of the hcnesites. I. COALS OF EROSIO.I GIVTRON. PLqN This plan,was prepared with the goal of preventing any degradation of the quality of the receiving waters as a result of the activities enccnPassed in the construction plans. For this project, the receiving waters are located to the south and east of the Jefferson County Fairgrounds. Vater quality controls are necessary to prevent three distinctly different types of inpacts. The first consists of darage done by soils being taken uP by running water. This type of darage typically consists of rillinS' rutting and loss of topsoil. The next type of darage is the degradation of urater quality as " the soils are transported by the water. Ttte last type of darage is done by the deposition of the soils, usually in an area uttere uater velocities are reduced. The enphasis of erosion control for this proiect will be on the prevention of soil uptake by running water. Successful prevention of soil uptake will also prevent darage caused by detradation of water quality and by soil deposition. While the rneasures described below should theoretically prevent the uptake of soils, corrrrpn sense dictates that additional nnasures be irplenrented. For this project, additional rneasures will be taken to allow deposition of transported soils under controlled conditions before flows are allowed to enter receiving waters. This will be acccnplished prinarily by the use of grassy swales' with siltation catctrnent areas being required only where grassy swales are not feasible. I I. CENERAL PROVISICNS The General Provisions of this plan are general to the overall project site and apply to all portions of the site, including offsite erosion control activities. A. Protection of Exposed Soil This provision is the single npst inportant elenrent of this erosion controlplan. If exposed soils are protected such that soil particles are not picked up by running water, erosion will not occur. Protection of exposed soil consists of three areas of effort. Page 2 l. Minimize Disturbance of Vegt':tation' The existing vegetation on the si te corprises ttre best overall Protection against etoiion. To protect this resource and to keep the risk of erosion to a mininr,m, clearing and grading activities outside of the areas necessary to construct the inprovenents shown on the construction plans shall be kept to an absolute minimun. All reasonable effort shall be nade to ensure the survival of newly planted vegetation, especially grasses. Since this grass is a very- effective n*inoa of preventing erosion of disturbed areas, extrene care shall be taken to minimize its disturbance. 2. -Urrrrtr". the Length of Time the Soil is Unprotected Where grading is necessary for construction activities, the grading shall be delayed ai long as reasonable to minimize the length of tinre that the soil is exposed to the elsrnnts. Where exposure of bare soil is necessary to acccrplish certain portions of the work, such portions of the work shall be carpleted prcnptly in order to reduce the chance of an erosive rainfall event catching the soil unprotected. I 3. Ensure Prcrpt Revegetation of Disturbed Areas Every effort shall be nade to ensure a healthy stand of protective vegetation is established as soon as possible. If the season or construction scheduling will not allow pronpt revegetation of an area where construction activities have been csrpleted, the area shall be covered with visqueen sheeting, straw, mulch or other covering chosen to natch the situation and with due regard for the length of tinre that the area is expected to renain uncovered. The appropriate season for pronpt revegetation is assured to be March I to Mat 15 and August 15 to October I where sprinkling'is not Practicable and March I to october I where sprinkling is practicable. Where hydroseeding is required, the mix of seed, fertilizer, and rulch, and the application rate, shall be determined by the hydroseeding subcontraclor based on the season, soil, npisture and his experience and professional judgrnent. B. Crading Limi ts Clearing limits, property lines, easerK:nt I ines, wetlands, critical areas and their buffers within or adjacent to the project limits shall be narked in the field prior to beginning construction and care shall be taken that the narks are not disturbed during construction. ['ag<.1 3 C. Protection of Adjacent Properties Care mlst be taken that adjacent properties do not exPeridnce any degradation of water quality as a result of activities perfornred on the project site. This plan provides for the use of native vegetation, grassy swales, interceptor swales and ditches, silt fencing and other inprovsnents to collect and treat runoff that would otherwise tend to flow across proPerty boundaries. To-this end, flows that are even potentially contaninated with soil fines shall be prevented fran leaving the construction zone until they are treated as described. Following treatnent, the runoff can be released as sheet flows where they will leave the construction zone. l. Grassy Scales Grassy swales are shallow, grassy and gently sloping ditches where flows can be dispersed into sheet flows with extrenely low velocities. These low velocities will allow nearly ccrplete deposition of transported soils. It should be noted that grassy swales are not intended to renpve oil or toxic substances frcrn runoff on this Proiect. 2. lnterceptor Swales Interceptor swales are shallow trenches constructed in a single pass by a relatively large dozer equipped with one to three ripper teeth. The preferred configuration of ripper teeth for construction of interceptor swalesr is two teeth positioned on the outside of the ripper assenbly. This type of swale construction will tear through the existing sod without rernving it. Leaving the sod in place will protect against erosion of the swale bottcnr on steeper sloPes. Swales thus constructed are intended to intercept sheet flows and infiltrate thsn into the soil. When flows are Sreater than can be infiltrated, the swales will provide a path for runoff of excess flows. Such excess flows will run along the swale until they are infiltrated or they enter grassy swales. In order to be effective, the surface of the ground mlst not be,regraded during the life of the swale. Grading or blading of the surface of these swales will defeat their purpose. Construction of interceptor swales causes only mininal disruption of the ground contours. For this reason the swales need not be renpved at the end of their usefulness. P:rge: Ir i. lnterceptor Di tches In.tercep.tor di tches are di tches used to intercept and redirect runof f . They haie a npre significant inpact on existing vegetation.since it is necessary to renrcve the sod or other ground cover for their construction. They are constructed according to details shown in the construction plans 4. Silt Fencing Silt Fencing shall be provided where shown on the plans. Silt fencing details are included in the construction plans' post supported silt fencing is generally used for long runs of fence. Hay baleSupported fencing is generally used for check dars and similar short runs of fence. D. Phasing of Construction Inprovennnts specified in this plan shall be constructed prior to performing any srlaing or excavation on the project site. After cqrpletion of the specified inpro*rgnents, work may proceed strictly within the limits described above. E. Steepness of SloPes No new slopes steeper than 2:l (horizontal:vertical) shall be created except as provided innrediately below. Sides of trenches are not considered to be slopes. Exceptions: Slopes less than five feet in height. Slopes which are covered with clear visqueen or mulch within seven days after ccrpletion of creation of the slope' Slopes created during the construction of the inprovements required bY this Plan. I I Where shown on the plans, interceptor top of slopes to prevent concentrated tches shall be constructed across the ows frqn descending the slope. difl Page 5 F. Release of Offsite Flows For this project, release of runoff shalt occur only at the outlet of the detention pond. The only exception is the snall anpunt of runoff which will be generatla Oy the east land of Jaclsran Street between the access to the Faiigrounds and 45th Street. Runoff frqn that area wilt be allowed to sheet flow onto the Fairgrounds, being biofiltered through the Srass as it is at the present tirne. G. Stabilization of Erosion Control and Tenporary Stormwater Channels Ctrannels, slopes, ernbant<nnnts, trenches and similar areas of disturbed soil which are required for the inplgnentation of this erosion control plan shall shall be subiect to the sane erosion control requirernents as other portigns of the proiect. In addition to the general protective requirsrlents, sPecific arnprirl8 nrethods are included in the appropriate details. H. Storm Drain Inlet Protection All catch basins shall be covered or plugged to prevent flows frqn entering thenr _ until the contributing basin has been protected as Provided for in this Plan.t Exceptions to this requirenrent will be spelled out either on the construction plans or in the special Provisions below. J. Underground Utility Construction It is expected that the najor source of potentially contaminated flows on this project nay be frcn punping of trenches and boring pits. For this reason' flows discharged frcn purping shall be closely rmnitored and except where there is no visible turbidity, treated as described below. The installation of underground utilities shall be perfornnd in cqnfornance with the following restrictions: Where feasible, no rrcre than 500 feet of trench shall be oPened at one tinre. Where consistent with safety and space considerations, stockpiles of excavated soils shall be placed on the uphill side of the trench. Trenches shall be backfilled and revegetated as soon as reasonably possible following placanent of utilities. Page 6 Discharge fran punps use<l in dewatering trenchcs shatI be treated as described below. where the upstrearn end of a pipe is subject to inundation, it shall be tenporarily capped or PluSSed at the end of each day's work to prevent soil frsn being washed into the piPe. K. Construction Access Routes During periods of dry weather (where the soil is too dry to adhere to the tires of construction vehicles) construction vehicles rlay access paved streets directly frqn the project site with rncnitoring and occasional sweeping of the paved sireet as necessary to prevent accurulations of soil. During p"iioa" of wet weather (where soil readily adheres to the tires ol vehiclel) the vehicles may access graveled roads directly frqn the project site as necessary, but shall not access paved roads without first having been routed over areas where existing trass renrains or routed down a minimun of 150 feet of graveled road. Access routes over grass shall be changed occasionally to ensure ihat *heel ruts are not allowed to develop and that the grass is not unduly worn down. " If l5O feet of grass or gravel road is not available, large crushed rock nay be placed at the point of egress frqn the property to provide a place for soil deposition under controlled conditions. , lf the above procedures are not effective, as evidenced by a buildup of soil on the paved ioad, wtreel washing stations shall be installed in accordance with thl standard drawings in the Stonrnrater Managenrent Manual for the Puget Sound Basin (NE Technical lUanual). L. Rermval of Tenporary Erosion Control Facilities Tenporary Erosion Control Facilities shall be prcrptly rennved once their prelence- is no longer required. Drring their renpvalr aDI entrapPed silt shall Le disposed of in suitable locations. Such silt shall in no case be left in a channel or where it would be washed into receiving waters by the next storm. The role of the Erosion Control Facilities is to prevent silt frqn entering waters, not to merely delay it until after construction is ccrpleted. M. PtrrpingAewatering of Trenches Discharges frqn pLrrps used in dewatering trenches shall be dispersed by one of the following nrethods: Directing flows onto existing heavily vegetated areas. Flows shall be . directed against objects such as old tires or sturps, capable of disrupting concentrated flows. P;rge 7 C)irecting flows orrto a pad constructed of ctean, pit run gravel. The pad shall be a mininrrn of 30 feet square and flows shall be directed into a circle of 5 - 8 inch dianreter stones to assist in dispersing flows into sheet flows. Directing flows into interceptor swales or ditches constructed per the requirsnents of this plan. Directing flows directly into a grassy swale constructed per this plan. ln no case shall flows discharged frqn a purp be allowed to rennin as a concentrated flow. Every effort shall be nade to break the flows into sheet flows. In all ca-5es, flows containing visible turbidity shall be treated by flowing through grassy swales prior to being released. N. Control of Toxic Substances No toxic or noxious substances shall be used, stored or disposed of on or off the project site in conjunction with this project except in full ccnplidnce withall applicable federal, state and local laws and regulations and the-' recqrnendations of the supplier of the substance. The product label or instructions for use and the Material Safety Data Sheets (ltlSDS) for such products shall be kept on the site until the product has been used up or renpved frqn the site and properly disposed ot. llhile not ccnnpnly thought of as hazardous naterials, ccnrnn fertilizer can be very daraging if allowed to enter receiving uraters. Fertilizers shall only be used in accordance with the recannendations of the supplier and any concentrations such as dribbles or leaks shall be cleaned up. In the event of a spill or other unusual event involving toxic or hazardous naterials, work in the vicinity shall be innrediately stopped and the following agencies notified: Port Townsend Public Works Departnent, (206) 385-7212 Washington State Department of Ecology, (206) 459-6000 during nornal business hours or (206) 753-2353 after hours If the incident presents an innrediate threat to life, health, or property, The Port Townsend Fire and Police Departnents shall be notified by dialins 9ll. Page 8 O. Petrolcun SPi lls The following requirernents are included to ensure conpliance with Part &0 of CFR I 12 in cases where SPCC Plans are required. Storage of fuel for construction vehicles and fueling of construction vehicles shall be performed in accordance with the following requirsnents: Driver Training - All erployees assigned to operate fuel trucks will be Properly trained. in appropriate regulations and safety procedures. .Training shall include proper inspection and use of tanks, hatches, valves' PunPs, hoses and fuel deliverY equiFrnent. Fueling of Vehicles - Fuel nozzles shall be locked wtren not attended and hoses shaf,l be rewound or otherwise properly stored when not in use. Unqttended fueling which relies on the proper operation of autqratic shutoff nozzles shall not be permitted. Parking of Fuel Tankers - Parking areas for fuel trucks shall be selected such that spills wilt not leave the area. Fuel trucks shall not be parked closer than 25 feet to an interceptor or Srassy swale. When fuel trucks must be taken to other portions of the project to fuel equiFnentr they rnrst be continuously attended or returned to the staging area. Fuel trucks shall be locked with the wheels chocked when unattended and not in use. Contairment of Spills - Spills shall be innrediately diked and every effort nrade.. to stop spillage. Each fuel truck shall carry a long handled shovel for usd in containing spills. In the event of a spill' the U. S. Envirornpntal Protection Agency, Seattle, Washington (206) 442-1253 shall be notified as soon as possible. If the nragnitude of the spill is such that it presents a threat to life or property, it shalt be irrrndiately reported by dialine 9ll frcrn the nearest phone. P. Maintenance It is critical that the various inprovenents required by this plan be naintained in their intended condition. The project forenan shall inspect the various parts of the systern at least once daily. Any danaged or nbn-functioning ccrponents of the systern shall be repaired the sane day or before noon of the next working day. In addition, the forenan shall perform additional inspections during or innrediately after significant rainfall. Fornation of rills' deposits of silt and similar indications of erosion shall.be reported irmediately to the project engineer. I I I. SPECIAL PROVISIO.IS The following itenrs are necessary to provide a reasonable level of protection against silts and other debris being washed onto neighboring parcels or into receiving waters. These itenrs shall be constructed, naintained and rsrpved in accordance with the general provisions above, the details shoum on the construction plans, and these sPecial provisions. Pagt: 9 A. Jaclsnan Street Phasing/Timing The following sequence of construction is provided as the best arrangernent for preventing eiosion and degradation of water quality, particularly if tonstruction occurs during a rainy period. The sequence may be nrcdified if the work can be acccrptished during dry weather with little likelihood of ra[n. tvlodification is particularly encouraged if it will allow the entire s'tormwater nanagenent systenr to be installed in a few days of dry weather. Innrediately after clearing and before any ground cover is distur.bed' a silt fence shall be constructJ adjacent to the existing fence on the east side of Jaclsran Street. After construction of the silt fence, work within the right of way n6y proceed. The storm sewer systan and detention pond shall be constructed as-a firlt priority. LJpon ccnpletion of the storm sewer, the Srassy swale shown on the eagt side of Jactsran Street on sheet 2 of the constrution plans shall be constructed. A check dan of hay bale supportd silt fencing shall be constructed around catch basins 2 ard 3. These check dars shall be constructed to filter water prior to allowing it to enter the catch basins. Care shall be taken that the check dam do not divert flows around and past the catch basins. Additional check dars shall be constructed at 100 foot intervals along the east swale. The east swale shall be hydroseeded as soon as reasonably practical after it'' is constructed. After the east swale is constructed and check dars are in place, other work within the right of way nay then proceed. underground utilities shall be installed and the street brought to subgrade with no delays. Check dars shall be constructed in the west scale at 100 foot intervals inmediately after construction of the west swale. Within one week of the street having been brought to subgrade, all exposed cut, fill and swale slopes shall be hydroseeded. If all underground utilities can be instalted ard the street brought to subgrade in a short period of tinre after cqrpletion of the east swale, hydroseeding of the east swale nay be delayed untit the entire right of uay is ready for hydroseeding. The silt fence adjacent to the fairgrounds shall be renrcved once the east swale has been constructed and is capable of intercePtin8 all flbws prior to their reaching the right of way line and the storm sewer is capable of transporting flows out of the right of way. If the storm sewer systan and the east swale can be constructed in a few days and in dry weather, the silt fence on the east side of the right of way nay be qnitted. Page l0 'Ihe check dans located in the east swale and around catch basin ntmber 2 shalt be renrcvecl af ter the street is paved and a healthy stand of Srass covers al I disturbed soils east of the street centerline- The check dans in the west swale(s) and around catch basin nunber 3 nay be renpved when the street is paved and a healthy stand of grass exists on all disturbed soil on the west side of'the centerline of the street. If it is desired that the west grassy swale provide erosion protection during the develoFrnent of parcels above Jacknan Street, the check dans should be left in place until such developnent is ccrpleted and the lots are fully revegetated. B. Offsite Sanitary Sewer Main Construction of the sanitary sewer nain downstrean of nanhole nrmber 4 shall proceed ii accordance with the general provisions above. Once begun, the work shall be ccnpleted in a timely manner with no unnecessary delays. Inrnediately after the work is ccnpleted and the trench backfilled' erosion control measures shall be taken as described below. If delays cannot be avoided during construction, the erosion control rneasures described below shall be inplennnted for those portions of the system which have been ccrpleted. After ccrpletion of construction, an interceptor swale shall be constructed- down the north line of the easenent as described above. Care shall be taken that no property corner narkers are disturbed. Check dars nade out of hay bale supported silt fencing shall be bonstructed entirely across the easernent at intervals of no nDre than 200 feet. After ccrpletion of the check dans, all disturbed soils shall be hydroseeded. The check dars shall be rsrpved when all disturbed areas have been successfully revegetated. C. Detention Pond All disturbed areas within and near the detention pond shall be hydroseeded. A series of three check dans, each a minimrrn of 20 feet long shall be placed across the watercourse leading Jrqn the detention pond outlet pipe. One half cubic yard of quarry spalls shall be placed about the'outlet of the PiPe. Planting of obligate wetland species in the sediment catctment area of the detention pond is encouraged. The check dans below the detention pond shall rgnain in place unti l the interior of the pond is fully revegetated. Page,. I I IV. PERMANENT WATER qJALITY CCI\TROL FACII.ITIES Pernanent water quality control wilt be provided by a series of three types of treatnrents. The first level of treatnrent will be provided by the series of grassy swales along both sides of the street. The swales will be a minimrrn of one foot wide on the bottqn and will have naximrrn longitudinal slopes of just under 1.50s. The next level of treatnrent will be sedinrent deposition rvithin the detention pond. This level of treatnrent will serve as a backup to that provided by the Lt"""y swales. If the grassy swales function as intended, there will be no sedinrent to be deposited in the pond. The final level of treatnent wilf be provided by sheet flows across the existing grassy pasture to the east of the detention pond. This will provide prirrrary Ireatnent (rennval of suspended silts) in the (unlikely) event that neither the grassy swales non the detention pond settlgment is effective. The expected rrcde of ttri" final level of treatment is polishin8 of flows prior to discharge frcrn the proiect site. v. PERMANEIT WATER qIFNTITY CCNIRON- -nPerrr.n"nt cater quantity control will be provided by the detention pond. Gqrplete calcula{ions of the operation of the pond are included in the docrrnent "mitt.tAcE cAl-cugrtcNs FcR JAcxtlAN STREET D(TENsIcN." { I ; DESIO.I MRRATIVE for JACXMAN STREgf DffENSICN DES ICN MRRATIVE for JACTOdAN STREET PffENSICN S@PE This report was prepard to supplernnt the construction plans and specificationsfor the extension of one block of Jaclcrnn Street in the City of-'Port Townsend.It provides explanatory naterial and docunents the design calculations and assunptions for portions of the work. It uas prepared as an aid during the plan review process and is not intended to be a part of the construction docrrnents. STREET Jaclsran Street will be constructed between 45th Street and the theoretical location of 43rd Street. The existing pavernnt between 45th Street and the access to the @unty Fairgrounds will be utilized to sane extent, with new shoulders (and pavenent as necessary) being added to bring this section into ccrpliance with the Standard Street Section shown on Detail I of Sheet I of ther construction plans. The adequacy of the structural section of the existing paverent is dgrpnstrated by its nany years of satisfactory service. The Standard Section will provide parking on both sides of the street while allowing a full 20 feet for traffic. The structural section is the minimun for the City of Port Townsend without a special design. The length of this project does not urarrant the special tests necessary to perform a custon design. Other design options such as delaying placsnent of the final lift of asphalt nay provide both cost savings and a better surface but the cost savings would be minor for the short lengthof street. The proposed structural section has been shown to be quite conservative, especially for a residential street, in nany years of use on the North Olynpic Peninsula. SAIIITARY SEIYER This project provides for the construction of a sanitary sewer nain serving the five lots fronting on the new section of street. The nain will run southerly to the end of the new street section and then easterly, across an easement over the south end of the fairgrounds. lt will terminate at an existing sewer line as shown on sheet 2 of the plans. Pagc 2 ln grder to avoirl a jurisdictional we.tland i t is necessary to route the sanitary sewer nain further to the north than would otherwise be the c:rse. An existing rnlhole very near the proposed connection to the existing rmnhole cannot be econqnically used due to its proximity to the wetland. To enter the existing nain at the existing ranhole would require two newnanholes and rechannelization to pr<lvide an adequate entrance. The plans provide for the construction of a new "saddle" nanhole to be constructed over and around the existing sewer nain. The new pipe will enter the new nanhole high enough to allow fof future extension of the new pipe to a new sanitary sewer nain contenplated to be installed to the east of the existing sanitary sewer nain. WATER Water service witl be provided by constructing an 8 inch extension of an existing 6 inch water nain which presently runs down the east side of Jaclsran Street to a point approxinately 100 feet south of 45th Street. New hydrants will be installed at 45th and 43rd Streets. All service taps fran the nain will be a minimln of I inch to accqnrpdate the' growing trend toward residential sprinkler systenrs. No such systens are proposea at present, but upsizing of the taps frsn 3/4 inch to I inch is reasonably inexpensive if perfornred before the street is paved.i: srcRtil sEurERs The overall stornnrater ranagernent systern consists of the collection systent (storm sewers), the water quality treatrnnt systens (prirmrily trassy swales) and the detention systern. An existing street one block west of Holconb Street routes runoff frqn the hillsides above this project to the north' limiting runon to this project to the two blocks innrediately west of the project. Flows frqn the block to the west of Holcsr$ Street cross under Holcqnb Street via culvert and are routed by topography to Jaclcran Street at approxinate station 4+00 where they will enter the proposed stom sewei via catch basin nunber l. Runoff fran the west side of the new section of Jaclsran Street will also enter the proposed storm sewer at the sarn point. Runoff frqn the east side of the new section of Jaclsran Street will enter the storrn sewer systern at catch basin nrrr$er 2, to be located inmediately across the street frqn catch basin nrrrber l. A snall anpunt of runoff frqn the east side of Jaclaran Street between 45th Street and the access to the fairgrounds will continue to flow to the east without interruption. The storm sewer is sized to pass a 25 year storm event. Carplete calculations of both the design storm and the hydraulic caPacity of the storm sewer systen are contained in the docunent titled "ffiAINACE CAIIULATICNS FCR JACKMAN STREET EffENSICN., Page 3 ST(X|vIIATFR DETENT IO.l Storrnrrater quantity will be controlled by a typical detention pond to be located south east of the proposed south end of the project, as shown on sheet 3 of the construction plans. Cqrplete hydraulic and hydrologic calculations for the stormwater detention pond are included in "mAINACE CALo'JI-ATICI{S F€R JACKIMN STREET D(TENSICN. '' EROS Icn.I An erosion control plan is included as a separate docunent.