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Home My WebLink About938100435 Stormwater Mgmt STORMWA TER SITE PLAN for Parcel 938-100-435 I ...... ,! . i RECEIVED . Prepared for: WAYNE & CAROLYN HAWKS APPROVED. . STQRMW A TER PLAN EXPIRES 8-25-07 I . . .' . '. .f i NTI Engineering & Surveying 717 S. PeabodY' ':~<port,ngQCt.\fj::_, !~O-452- ~49~ :1' \/ STORMWATER SITE PLAN . .. i ! Prepared for Wayne & Carolyn Hawks August 2005 For the Property Described as Parcel Number 938-100-435 Located in Section 13, Township 30 North, Range 2 West, Jefferson County Prepared by: N.TI ENGINEERING & SURVEYING 717 S. Peabody Street Port Angeles, Washington 98362 360-452-8491 i i CAPE GEORGE VICINITY MAP 5 HASTINGS '",,- 27 I 1/2 ~ 1/4 0 SCALE IN MILES ~ NTI NTI ENGINEERING & SURVEYING Engineers - Land Surveyors - Geologists Construction Inspection - Materials Testing 717 SOUTH PEABODY, PORT ANGELES, WASHINGTON 98362, (360) 452-8491 Map 1 i i i STORMWATER SITE PLAN for Parcel 938-100-435 ~~ ~~--;': Map 2 iv STORMWATERSITE PLAN for Parcel 938-100-435 Hawks Neighborhood Map OUTFALL A T BEACH CURTAIN DRAIN STORM SEWERS AND CATCH BASINS STORM SEWERS AND CATCH BASINS DRAINAGE DITCHES AND CULVERTS (TYP) Map3 v STORMWATER SITE PLAN for Parcel 938-100-435 HAWKS SITE MAP ._~_.~.../ /' .,// // //ON SITE BASjN/1s THE ./ /// ENTIRE .HAwkS PARCEL ///~ / .- ...../../.// ____.--r//'/' .../'/ / ~. .... /# /# ../.../"~//~ / ~ EXIsf7NG /-.//./ ---::]/GHTLINE /~ ~ ....- --~;7 #' \ // ~./.\,"~ /\/ / \ SE~pJ)~l!it/~ \ /' \ ~fff !~,~ /' \;/< \ ~-'" -~ /",/ -/....-,../\ / .~/~ _/- .----/ \ ----- 'z) ~ I 30 20 10 0 30 SCALE IN FEET MINOR AMOUNTS OF EXISnNG RUN-OFF THAT LEAVE THE HAWKS PARCEL ON THE SOUTH SIDE ARE NEGLECTED IN THE CALCUu.nONS BUT WILL BE COLLECTED VIA A DIVERSION SWALE AND DIRECTED TO THE TIGHT- UNE PIPE. r --:J/- -- ~ , ------- ----_/ "" //.----///'/ ~///// r ..--/ / //-/;;;;DAnON/'/////' \_~?f!Tj!BlNr/ 06' OFF SITE ~ CONTRIBUTING BASIN r::;::; ._....-.-.-......- ---- ROOF LINE ~_/ .;/~"Io/ -- ---- /_~---_/-~-- //- _ _ 00////_ - /7 PALMERo/DRIVE (PAVEDj / I _ _ _ _ /_ _ _ _ -L - " EXISTING CURTAIN DRAIN, INTERCEPTS RUN-ON FROM ABOVE EXISnNG CURTAIN DRAIN SUMP I " --1-- Map4 vi HAWKS - STORMWATER CONVEYANCE PLAN 6" DIA, 160 PSI, PVC STORM SEWER PIPE INSTALLED WITH 2' MIN COVER PER MANUFACTURER'S RECOMMENDATIONS ADJUST GRADES OF CATCH BASINS TO MATCH INVERT OF EXISnNG TIGHTLlNE PIPE, EXISTING GROUND ELEVATIONS AND TO PROVIDE A MINIMUM SLOPE OF 1% ON THE 6" STORM SEWER PIPE BETWEEN THEM. POSlnON RIMS OF CATCH BASINS 1" BELOW INVERT OF INTERCEPTOR SWALES ENTERING THE CATCH BASINS. INTERCEPTOR SW~ TYPICAL ON ALL FOUR SIDES OF PARCEL, PER DETAIL TYPE 2 CATCH BASIN OR FUNCnONAL EQUNALENT, TYPICAL 2 PLACES <: ......J/ ",,/'r'~ COVER INTERCEPTOR SWALES AND ADJOINING SPOILS WITH FILTER FABRIC BETWEEN OCTOBER 1 AND APRIL 30 UNLESS EXPOSED SOILS HAVE BEEN SUCCESSFULLY REVEGETATED 18" MIN BASE WIDTH 6" MIJ DEPTH INTERCEPTOR SWALE CROSS SECTION POSITION INTERCEPTOR SWALE TO CATCH SHEET FLOWS FROM PALMER DRIVE BEFORE THEY ENTER THE CURTAIN DRAIN " EXISTING CURTAIN DRAIN, INTERCEPTS RUN-ON FROM ABOVE 12" CULV PER'/ ARCHITECTUf?AL PLANS / I --1-- ...... /' PALMcf'DRIVE (PAVED} I I _ _ /~ _ ..L o NTI - 'Z~ ~ 30 20 10 0 SCALE IN FEET NTI ENGINEERING & SURVEYING Engineers - Land Surveyors - Geologists Construction Inspection - Materials Testing 717 SOUTH PEABODY, PORT ANGElES, WASHINGTON 983621 (360) 452-8491 Detail Drawing 1 vii I 30 EXPIRES HAWKS - EROSION CONTROL MAP ~': PROVIDE INLET PROTECnON AT BOTH CATCH BASINS PER DETAIL '" INSTALL EROSION CONTROL WAmES WHERE INDICATED. AND PER DETAIL " EXISTING CURTAIN DRAIN, INTERCEPTS RUN-ON FROM ABOVE // 11"/ 12" CULV P5R/ ARCHITECTUfAL PLANS _/ _ _ PALMER"/DRNE (PAVED)/ / ! / _....L-- ft NTI - -,Z~ ~ 30 20 10 0 SCALE IN FEET NTI ENGINEERING & SURVEYING I 30 EXPIRES Engineers - Land Surveyors - Geologists Construction Inspection - Materials Testing 717 SOUTH PEABODY, PORT ANGELES, WASHINGTON 98362, (360)452-8491 Detail Drawing 2 viii HAWKS - WATTLES DETAIL WAffiE CASING IS A BIODEGRADABLE TUBULAR PLASnC OR SIMILAR ENCASING MATERIAL ~ PLACE WATTLE IN .J" - 5" DEEP TRENCH 1" SQUARE STAKES DRIVEN THROUGH / WAmE EVERY 3' - 4' 8" - 10" STRAW FILLED WAmE // / ...----/1 / --=--- , I I I / I ~/// . -/ / 1- -II / If, I I I - .---11 I ---- / I _.__ _ / ___._ 111- - /"=:-///-/1/ 1-/ /-/1/ 11/ 111/ STRAW WATTLE - STANDARD STAKING NO SCALE FOR SHORT DURAnON PROJECTS WHERE THE CONTRACTOR DESIRES TO REUSE THE WAmES WITHOUT DAMAGING THE CASING THE ALTERNATE A-FRAME STAKING METHOD SHOWN HERE MAY BE USED. STRAW WATTLE - ALTERNATE STAKING NO SCALE (ft NTI NTI ENGINEERING & SURVEYING Engineers - Land Surveyors - Geologists Construction Inspection - Materials Testing 717 SOUTH PEABODY, PORT ANGELES, WASHINGTON 98362, (360) 452-8491 Detail Drawing 3 ix (ft NTI HAWKS - INLET PROTECTION DETAIL DROP INLET WITH GRATE WHERE CATCH BASIN UES IN ROUTE OF ACCESS USE SIL T SACK MANUFACTURED BY ACF, INC. OR EQUAL. CLEAN AFTER EACH RUN-OFF EVENT. FIL TER FABRIC FENCE INLET FIL TER DETAIL NOT TO SCALE NTI ENGINEERING & SURVEYING Engineers - Land Surveyors - Geologists Construction Inspection - Materials Testing 717 SOUTH PEABODY, PORT ANGELES, WASHINGTON 98362, (360) 452-8491 Detail Drawing 4 x HAWKS - BASEMENT BACKFILL DETAIL 1 CONSTRucnON SEQUENCE: . 1) INSTALL B/TUMASnC WATERPROOFING AGAINST FULL HEIGHT OF WALL PER MANUFACTURER'S RECOMMENDAnONS. 2) PLACE IMPERVIOUS FABRIC (10 MIL THICKNESS MIN) AGAINST WALL AND OVER FOOTING AND BOTTOM OF EXCAVATION AS SHOWN. 3) INSTALL FOOnNG DRAIN WRAPPED IN FILTER FABRIC OVER TOP OF IMPERVIOUS FABRIC. 4) PLACE FILTER FABRIC AGAINST FACE OF EXCAVATION. 5) BACKFILL ENTIRE EXcAVATION WITH CLEAN WASHED DRAIN ROCK OR PEA GRAVEL. 6) COVER TOP OF DRAIN ROCK WITH FILTER FABRIC. BACKFILL ENTIRE AREA BEHIND WALL WITH CLEAN WASHED DRAIN ROCK OF PEA GRAVEL IMPERVIOUS FABRIC AND BITUMASTIC WATERPROOFING PLACED AGAINST CONCRETE WALL PER THIS DETAIL AND DETAIL 2 . '.' ... " . ~ / I /= -II/- I /I'~/!/- ,/ -, / EXTEND -I / /~ IMPERVIOUS FABRIC BEYOND EDGE OF DRAIN AS INDICATED 4 .. . '. .. ..-4 , ~ . ~. :... ........, .. '. ~ . .., :. 'A; . '. , 'i . ~~ ." ,': ' '; ,', d, .. . ~ " CLEAN WASHED DRAIN ROCK OR PEA GRA VEL "/'/ -I/! ............._-/// ...--.... ~ ~.__._-_.- .-.----. ..... I/!~ /1 /.::= I; -/11- ( FOOTING (THICKENED EDGE OR SPREAD FOOTING) ROUTE FOOTING DRAIN TO CATCH BASIN AT SOUTHWEST CORNER OF PARCEL IN PIPE SEPARATE FROM STORMWATER PIPES. 4 11 PERFORA TED PE OR PVC PIPE ROUTED TO STORM SEWER, DRYWELL, OR DA YL/GHT EXPIRES FOOTING DRAIN DETAIL NO SCALE (ft NTI NTI ENGINEERING & SURVEYING Engineers - Land Surveyors - Geologists Construction Inspection - Materials Testing 717 SOUTH PEABODY, PORT ANGELES, WASHINGTON 98362, (360) 452-8491 Detail Drawing 5 xi . ! STORMWATER SITE PLAN for Parcel 938-100-435 . ,-\ ! JEFFERSON COUNTY STANDARD STORMWATER SITE PLAN NOTES i ~~~ . All erosion and sediment control Best Management Practices shall be selected, constructed, and maintained in accordance with the Washington Department of Ecology Stormwater Manaoement Manual for Western Washinoton (current ed ition). . ~~1 11 . The construction and maintenance of erosion and sediment control measures shall be the responsibility of the. contractor. The contractor shall not deviate from the approved plans without prior approval from the Jefferson County Public Works Department. The contractor shall have a set of approved plans on the site whenever construction is in progress. . The erosion and sediment control measures depicted on this plan are minimum requirements to meet anticipated site conditions. As conditions dictate during construction, the contractor shall implement additional measures as necessary to ensure erosion and sediment control. . Construction vehicle access shall be limited to one route, whenever possible. Quarry spalls or crushed rock shall be applied to the access in order to prevent sediment from being transported onto roads. If this should occur, roads shall be cleaned thoroughly by shoveling or sweeping. . Clearing shall be phased so that only areas that are being worked are exposed. All exposed and unworked soils shall be stabilized by appropriate Best Management Practices. From October 1 through April 30, unworked soils shall not be left exposed for more than 2 days. From May 1 through September 30, unworked soils shall not be left exposed for more than 7 days. . All erosion and sediment control measures shall be maintained in a satisfactory condition until such time as land disturbing activities are completed and the potential for onsite erosion has passed. . The contractor shall request inspection of temporary erosion and sediment control measures by the Jefferson County Public Works Department [(360) 385-9160] as soon as practicable after installation. xii STORMWATER SITE PLAN for Parcel 938-100-435 Abstract This project consists of the construction of a single family residence and related work on a single parcel in the Cape George Colony with an area of 0.31 acres. This Stormwater Site Plan (SSP or Plan) was prepared to examine and recommend Best Management Practices (BMPs) to mitigate stormwater related impacts of the construction of this project as required by Jefferson County. Existing curtain drains, tightline pipes, and storm sewers collect all of the stormwater from this parcel and convey it to marine waters so detention/infiltration is not required. The existing conveyance system is adequately sized to convey flows from this project. Detail drawings showing new area inlets and connections to the existing tightline pipes are included with this report. Construction phase erosion and sediment control measures are proposed to prevent soil from leaving the site during construction of the improvements. Detail drawings showing the proposed BMPs and their location are included with this report. This Plan includes the Construction Stormwater Pollution Prevention Plan (CSPPP) in its entirety. As a minimum, the CSPPP recommends sediment control wattles, a stabilized construction entrance, protection of inlets, and special attention to the existing curtain drain on the top of the parcel. Additional BMPs are included for use in the event that unforeseen circumstances require additional measures. xiii STORMWATER SITE PLAN for Parcel 938-100-435 Contents I. OVE RVI EW ..................................................... ............ ........... ................. ... ..1 A. Pre-Developed Condition .... ........... ... ... ............ ..... ...... ... .......... ....... ...2 1. P re-Conta ct Cond ition. . . . . . . . . . . .. . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .2 2. Existing Condition............................................................................2 B. Developed Cond ition ..... .......................... ...... ..... ............................. ...3 C. Proposed Improvements ..... ........ ... ... ... ... ....... ........... ......... ..... ...........3 D. Stormwater Runoff............... ........... .................. ... ... .................... ........4 1. Pre-Developed Stormwater Runoff ..................................................4 2. Post-Developed Stormwater Runoff ................................................5 E. Controlling and Challenging Site Parameters ..................................5 F. Natural Drainage System ..... ........ ... ...... ... ....... .... ........ ... ... ..... ... ...... ....6 G. Drainage To and From Adjacent Properties .....................................6 1 . Bypass Flows................................................................................... 6 H. Vicin ity Maps. ...... ............................................... .................................7 I. Site Map ...................................'............................................................ 7 J. Soi Is Map. ......... ... ... ........ ... ... ...... ........ ... ..... ... ... ...... ........ ... ... ...... ..... ....7 II. EXISTI N G CON DITION S .................. .................................... ..... ................ ..8 A. Natural Receiving Waters .... ... ....... .... ... ... ..... ... ........... ... ... ........ ...... ....9 B. Area-Specific Req uirements ....... ... ... ... ... ....... ......... ... ......... ... ..... ... ....9 1. Local Plans ....................................................................................10 2 . 0 rd in a n ce s .................................................................................... 1 0 3. Water Cleanup Plans .....................................................................1 0 III. OFF-SITE ANALYSIS ................................................................................10 IV. PERMANENT STORMWATER CONTROL PLAN.....................................10 A. Existing Site Hydrology.... ... ... ..... ... ... ... ... ... ........ ... ... ... ... ..... ...... ... ....10 B. Developed Site Hydrology ................................................................11 1. Methodology........................... ...... ............ .................................... .12 2. Ra i nfa II. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 3 3. Time of Concentration....................................................................13 4. Calculation of Peak Flow ...............................................................13 C. Performance Standards and Goals .................................................14 l.: 1. Minimum Requirement #1: Stormwater Site Plan ..........................15 2. Minimum Requirement #2: ConstructionStormwater Pollution Prevention Plan............................................................. ..16 xiv 3. Minimum Requirement #3: Source Control of Pollution .................16 (i) Lan d s ca pin g ............................................................................. 1 6 (ii) Vegetation Management......................................................... .17 ( i i i ) I rri gat ion ........................................ '. . . . . . . . . . . . . . . . . . . ... . . . . . . . . . . . . . . . . . . . . .. 1 8 (iv) Fertilizer Management............................................................ ..18 4. Minimum Requirement #4: Preservation of Natural Drainage Systems and Outfalls ................................................... ..19 5. Minimum Requirement #5: On-site Stormwater Management................................................................................. .20 D. Flow Control System .. ... ... ... ........ ...... ... ... ......... ..... ... ........... ...... .......20 E. Water Quality System .... ...... ... ... ..... ...... ... ......... ..... ... ...... ..... ... ...... ....20 F. Conveyance System Analysis and Design .....................................20 1. Interceptor Swale Design ...............................................................20 2. Tightline Pipe Hydraulic Capacity ..................................................21 V. CONSTRUCTION STORMWATER POLLUTION PREVENTION PLAN .......................................................................................................... 2 3 A. C I e a ri n g L i m its .................................................................................. 2 3 B. Construction Access.................................. ............................ ......... .24 C. Flow Rate Controls ..... ... ...... ... ..... ... ... ..... ... ....... ......... ... ..... ... ... .........24 D. Sedi ment Controls.................. ... ...................................................... .24 E. So i I S ta b i I i za t ion ..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25 F. Slope Protection ..... ..... ... ...... ... ........ ....... ... ........ ...... ... ... ..... ... ... ... ... ...25 G. Drain I n let 'Protection.................................. ..................................... .25 H. Channel and Outlet Stabilization .....................................................25 I. Control of Pollutants... ... ... ... ... ........ ... ... ... ... ..... ......... ........... ...... ... ... .25 1. Control of Toxic Substances........................................................ ..25 2 . Petro leu m S p i lis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . 26 (i) D ri ve r T ra i n i n g ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26 (ii) Fueling of Vehicles ...................................................................26 (iii) Parking of Fuel Tankers.......................................................... .26 (iv) Containment of Spills............................................................. ...27 J. Control of De-Watering ..... ... ... ..... ... ... ... ...... ... ..... ... ... ... ... ........ ... ... ... .27 K. Maintenance of BM Ps . ... ......... ..... ...... ... ..... ............. ... ... ... ..... ... ... ... ...28 L. Project Management...... ...... ... ..... ... ... ... ...... ... ... ........... ........ ... ...... ... .28 1. Phasing of Construction................................................................ .28 2 . Sea son a I Work L i m ita t ion s ............................................................ 29 3. Coordination with Utilities and Other Contractors ..........................29 4. I nspection and Monitoring............................................................ ..29 5. Maintaining an Updated Construction SWPPP ..............................29 VI. SPECIAL REPORTS AND STUDIES..........................................~..............29 VII. OTH ER PERMITS ... ... ...... ..... ......... ........ ... ...... ..... ...... ... ........ ... ... ... ... ... ..... .30 VIII. OPERATION AND MAINTENANCE MANUAL..........................................30 xv STORMWATER SITE PLAN for Parcel 938-100-435 ..,-A Figures Fig u re 1 ...................................................................................................................... 4 Fig u re 2 .................................................................................................................... 11 Fig u re 3 .................................................................................................................... 13 Maps Map 1 ........................................................................................................................ iii Map 2 ........................................................................................................................ iv Map 3 ......................................................................................................................... v Map 4 ........................................................................................................................ vi Map 5 ......................................................................................................................... 7 Photos Photo 1 ....................................................................................................................... 1 Photo 2....................................................................................................................... 2 Photo 3....................................................................................................................... 3 Photo 4....................................................................................................................... 6 Photo 5....................................................................................................................... 8 Photo 6....................................................................................................................... 9 Photo 7 ................................... ........... ........ ............ ........ ........................................... 19 Tables Table 1 ..................................................................................................................... 12 Table 2 ..................................................................................................................... 14 Tab Ie 3 ............................................. '. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1 5 Table 4 ..................................................................................................................... 21 Table 5 ..................................................................................................................... 22 Detail Drawings De ta i I D ra wi n g 1 ....................................................................................................... vi i Detail Drawing 2....................................................................................................... viii Deta i I D ra wi n g 3........................................................................................................ ix Detail Drawing 4 ......................................................................................................... x Detail Drawing 5........................................................................................................ xi xvi STORMWATER SITE PLAN for Parcel 938-100-435 Photo 1 I. OVERVIEW This plan was prepared to provide a reasonable level of protection, as required by Jefferson County ordinance, against damage being caused to properties within or without the projec(t during construction or as a result of increased stormwater runoff after development of the project. It follows the guidelines contained in the 2005 Edition of the Stormwater Manaoement Manual for Western Washinoton (2005 Manual), published by the Washington State Department of Ecology (DOE). This project consists of the construction of a single family residence for Wayne and Carolyn Hawks on the 0.31 acre parcel highlighted in red in Photo 1 above. 1 A. Pre-Developed Condition 1. Pre-Contact Condition Air photos taken in the 1940s show this area as forested with large irregular gaps in the forest cover that may be indicative of an area of emerging and/or dwindling prairie systems. The droughty soils and very low annual rainfall in the area would certainly have supported such a wildfire driven prairie environment. The patchy areas in the immediate vicinity of this parcel are much too small to support a conclusion that any prairies (or meadows) were permanent. This Plan assumes that the pre-contact condition was old growth evergreen forest. 2. ExistinQ Condition The site is an undeveloped lot in the Cape George Colony subdivision. It is densely vegetated with weeds and some native species as shown in Photo 2. ~~~" 4' '" '.' ..;7' .,..'.".. '....,... ......."........,..,....,..."...,.:..,.... . . -' ~, - - -. ".. r,' '..... .;'l.. ~,. ." - '-, ...... '..!-' ; ,. . .' .'. ",;' . :',\";.~:~.;~~:~~ Photo 2 The adjacent lots on the north and south are similarly undeveloped. On the east (uphill) is Palmer Drive, a paved road as shown in Photo 3. 2 Photo 3 To the west (downhill) are developed lots with homes and landscaping as shown in the photo on the cover of this report. There are no buildings on the site. Power, phone and water services are located at the top of the parcel as shown on the far right in Photo 3. The septic system has not been installed. A storm sewer connection (tightline pipe) is available along the south property line as shown in Map 3 and Map 4 on pages v and vi respectively. A portion of the west property line is fenced. B. Developed Condition It is proposed to construct a single family residence with attached garage, concrete approach slab, concrete walkway, septic system, lawn, and landscaping. Map 4 on page vi shows the locations of the proposed improvements. C. Proposed Improvements A total of 4320 square feet (0.0992 acres) of impervious surface is proposed. The roof of the house will consist of 3150 square .feet of non-pollution generating impervious surface. The concrete walkway in front (east of) the home will consist of 145 square feet of non-pollution generating impervious surface. The concrete approach slab will consist of 1025 square feet of pollution generating impervious surface. The remainder of the parcel is 3 modeled as 9184 square feet (0.2108 acres) of pollution generating pervious surfaces (lawn and landscaping). -I ] D. Stormwater Runoff Runoff onto and from the Hawks parcel is presently controlled by an existing storm drainage system which will be preserved. 1. Pre-Develooed Stormwater Runoff In its existing condition the site is generally protected from most of the effects of run-on flows from lands above. Stormwater from Palmer Drive flows onto the parcel as sheet flow and enters the curtain drain just inside the property boundary on the east. This curtain drain is deep and controls the flow of both surface and subsurface water from Palmer Drive. Figure 1 is a detail of the curtain drain taken from the original plans for its construction. IN 01 E CS : *' BOTTOM OF TF\ENCH TO MA1NTA.IN t'1IN.. \0/0 SLOPt. -* T I G HI L I t-.J EST 0 8 ~ L OCA i E 0 P-., LOv.! POI N I 5 IN 1 p, f ('..I G H ~ EASEM€.Nl'S WILL BE P,EOU!RECJ FOR ALL TRE:NCHS ~ND T\GHTLINE5 * T R ENe H S ,. 0 6 E G II I ~j T 0 I tv, PER MEA 6 L E LA .1 E: R 0 RAM A- X 1 M U iV1 OF IS FT. DEEP. * THE CONTRf\GTOR. \5 R~SPONS lBL( FOR CSAFETY MEA'::>URES A/",j[ ~F\OPER GONSTRuCiTION PROCEDURES FOR OEEPTRENGH5 ~ILE SPOIL ON DOWNHLL SlOE OF TRENCH \~ "/ GAAVEL AFrlA. 73-2.03A CIASS A 6~,s PERF PIPE G":'" . N ,NtO i Mf'ER!.J1EABL e: L~~ER. Figure 1 The curtain drain empties into a tightline pipe which flows down along the south property line. This tightline is believed to be a 6" diameter HOPE, non-perforated flex pipe. Similar pipe has been observed exiting the 4 ground at the bottom of other drains installed as part of the same project on adjacent parcels. . : There is an off-site basin on the north that contributes to run-on as sheet flow. This basin, depicted on Map 4 on page vi, is also protected by the curtain drain from sheet flows coming off Palmer Drive. Flows from this off-site basin enter the project parcel as sheet flow from the north. ~'.d 2. Post-Developed Stormwater Runoff The curtain drain along the top (east) side of the Hawks parcel and the adjacent parcel on the north intercepts both surface and subsurface flows from Palmer Drive, isolating the site hydrologically. Because of its importance in controlling stormwater flows, it will be carefully preserved during construction. ta: W Flows from the adjacent parcel to the north will be intercepted with a gentle interception swale located just inside the Hawks parcel. This swale will carry these flows downhill (westerly) to the bottom (west side of) the Hawks parcel. The swale will then turn to the south and intercept sheet flows from the backyard of the Hawk's parcel. The swale will empty into a yard drain located at the southwest corner of the Hawks parcel. The drain will discharge to the existing tightline pipe. Another interception swale will run down the south side of the Hawks parcel, just inside of the property line. This will collect the small amount of sheet flows that currently cross the south property line and carry them to the yard drain located at the southwest corner of the Hawks parcel. E. Controlling and Challenging Site Parameters There were two challenging aspects to preparing a stormwater plan for this site. The lower portion of the site has impermeable soils which have been described as being a clay dam. The "dam" acts to force groundwater to the surface near the top of the parcel where the clay layer is deeper. Dealing with this groundwater was the first challenge. The second challenge was to find a method of disposing of runoff from the site. After much research and three field visits, the existing storm drainage system was successfully mapped and it was confirmed that the system is continuous from the Hawks parcel to marine waters. This system acts. to control the groundwater flow and provides a conveyance directly to the receiving waters without the need for detention or infiltration. 5 F. Natural Drainage System A determination of the pre-contact, "natural" drainage regime of the site must be part investigation and part speculation. Field investigations and research indicated that large quantities of groundwater surface in the area. The soils map (Map 5 on page 7) shows a spring to the north of the Hawks parcel. From this information and a review of topographic maps, it appears that the "natural" drainage regime consisted of sheet flows from lands above mixing with groundwater surfacing as springs. As these combined flows moved further downslope, they formed shallow concentrated flows, eventually discharging into Discovery Bay. Photo 4 Photo 4 shows the discharge of such a small spring-fed concentrated flow at the beach downslope of the Hawks parcel. G. Drainage To and From Adjacent Properties As discussed in section I.D Stormwater Runoff, on page 4, there are only minor flows to and from adjacent lands and these are easily controlled by the existing subsurface drainage system. 1. BVDass Flows There will be no by-pass flows except minor amounts of sheet flows as discussed in section 1.0 Stormwater Runoff, on page 4. 6 H. Vicinity Maps A vicinity map is included as Map 1 on page iii. The Area Map included as Map 2 on page iv and the Neighborhood Map included as Map 3 on page v also contain useful information about the surrounding areas. I. Site Map A site map is included as Map 4 on page vi. Other maps are included in the same area at the beginning of this report. J. Soils Map The site may be found on map number 41 of the Soil Survey of Jefferson County Area (the Soil Survey) published by the U. S. Soil Conservation Service, a portion of which is reproduced here as Map 5. MapS 7 Map 5 can be compared with the other maps at the beginning of this report for additional orientation. The scale of the original Soil Survey map varies widely across the map, making it difficult to precisely locate a project. The location of the Hawks parcel on Map 5 should be considered approximate. Map number 41 predicts that the soils on the lower portion of this site are type StB, Swantown gravelly sandy loam, with type CmC, Clallam gravelly sandy loam on the upper portion. Swantown and Clallam soils have a similar gradation but Clallam soils are more permeable and have a deeper depth to an impervious layer. Swantown soils are poorly drained. This is consistent with the results of field investigations and research of other sources which indicated that saturated soils in the upper portion of the site discharge groundwater seepage which flowed over the top of the impervious soils on the lower portion of the site. With regard to the parameters for use in automated hydrologic calculations, these soils should be considered to function as glacial tills. II. EXISTING CONDITIONS The site is an undeveloped lot in the Cape George Colony subdivision. It is densely vegetated with weeds and some native species as shown in Photo 2 on page 2. ~ ~/ ~.........-- /'" Photo 5 8 ,1 , Photo 5 shows the upper portion of the parcel with Palmer Drive in the foreground. A. Natural Receiving Waters The natural receiving water for this project is Discovery Bay, a marine water connected to the Strait of Juan de Fuca. Flows from this project site are conveyed to the natural receiving waters by underground tightline pipes and storm sewers. The entire route of the conveyances from the Hawks parcel to marine waters is shown on Map 3 on page v. The tightline from the Hawks parcel to the storm sewer on Sunset Boulevard is 6" diameter HOPE flex pipe. The storm sewer along the east side of Sunset Boulevard is 12" diameter. !j Photo 6 Photo 6 shows the discharge of the Sunset Boulevard storm sewer at the beach of Discovery Bay. B. Area-Specific Requirements Jefferson County has a list of specific requirements which it requests be included in each drainage plan. This list is included on page xii near the beginning of this report. 9 1. Local Plans There are no local plans which affect this project beyond the general requirements relating to stormwater. 2. Ordinances There are no special local ordinances which affect this project beyond the general requirements relating to stormwater. 3. Water Cleanup Plans This site is not subject to a cleanup plan. III. OFF-SITE ANALYSIS An off-site analysis is not required by Jefferson County IV. PERMANENT STORMWATER CONTROL PLAN This Permanent Stormwater Control Plan governs permanent BMPs relating to the quality and quantity of stormwater for this project. A. Existing Site Hydrology Because of its small size and the existing curtain drain that isolates it from flows above, the hydrology of this site is fairly simple. Stormwater from Palmer Drive flows onto the parcel as sheet flow and enters the curtain drain just inside the property boundary on the east. This curtain drain is deep and controls the flow of both surface and subsurface water from Palmer Drive. The curtain drain empties into a tightline pipe which flows down along the south property line. There is an off-site basin on the north that contributes to run-on as sheet flow. This basin, depicted on Map 4 on page vi, is also protected by the curtain drain from sheet flows coming off Palmer Drive. Flows from this off-site basin enter the project parcel as sheet flow from the north. Because runoff from this site is conveyed to marine waters by a storm sewer system, stormwater quantity controls are not required. This being the case, there is no reason to calculate the existing hydrology of the site. Capacity analysis of the conveyances is best done using developed site parameters. 10 B. Developed Site Hydrology Calculation of the hydrology of the site in the developed condition is necessary to analyze the capacity of the conveyances from the site to the receiving waters. While the flows from the neighboring parcel to the north, shown in Map 4 on page vi will eventually be handled by the stormwater management system from that parcel, the flows will continue to cross over onto the Hawks parcel for some time after the Hawks parcel is developed. For this reason the Hawks conveyances should be sized to handle these flows. Runoff from Palmer Drive will enter the curtain drain and will share the conveyance in the tightline pipe below the Hawks parcel. For this reason these flows are included in the hydrologic calculations for the Hawks parcel. Data for the contributing basins for flows in the tightline pipe at the southwest corner of the Hawks parcel are shown on Figure 2. CD DEVELOPED CONDITION HYDROLOGY, BASINS ~~j ~ 30 20 10 0 SCALE IN FEET I 30 DEVELOPED ONDmON BASIN PARA FRS CD ON SITE, 10620 , LAWN/LANDSCAPING @ ROOF, 3270 SF, 1M OUS (j) CONCRETE SLAB, 1180 , IMPERVIOUS @) PALMER DRIVE, 3630 SF 'ERVlOUS @ OFF SITE, 8970 SF, MEAD PASTURE @ @ @ @) Figure 2 ;, I 11 Because of the relatively small areas involved and the steep grades for conveyances, a single runoff volume is calculated for a 25 year storm event and this volume is used to size all of the conveyances. This will not result in any pipes being oversized since all of the pipes are already installed. This is merely a verification of their capacities. Areas of the various surfaces and their characteristics for determining thresholds are listed in Section I.C Proposed Improvements, on page 3. These areas are slightly different from the areas used for hydrologic calculations since the hydrologic basins include small areas above of the Hawks parcel which will contribute to flows at the southwest corner of the parcel but are not included in threshold areas since they are not located on the project site. 1. Methodoloav Because the only need for hydrological calculations is to determine the peak instantaneous flow to verify the capacity of the conveyances, a continuous hydraulics analysis is unnecessary. This report used the Santa Barbara Urban Hydrograph Method to determine the peak runoff. Calculations of the Weighted Runoff Curve Number for the overall site are included in Table 1. POST-DEVELOPMENT WEIGHTED RUNOFF CURVE NUMBER CALCULATIONS Runoff Area Curve No. Land Use (acres) (Cn) (A x Cn) On site lawn, landscaping 0.24380 90.00 21.94 Roof 0.07510 98.00 7.36 Concrete 0.02710 98.00 2.66 Palmer Drive 0.08330 98.00 8.16 Off site meadow, pasture 0.20590 89.00 18.33 Subtotal Pervious Area = Remainder Area = 0.63520 0.00000 98.00 Total Pervious Area = Total Impervious Area = 0.63520 0.00000 58.446 0.635 Total Area = 0.63520 92.012 Weighted Ave. Runoff Curve Nunilier (rounded) 92.0 Table 1 12 2. Rainfall The total amount of precipitation falling over a 24 hour period during a storm having a mean recurrence interval of 25 years, will be 2.3 inches. This information was taken from a 25 year, 24 hour Isopluvial Map published by the U.S. Soil Conservation Service, a portion of which is reproduced here as Figure 3. The project location is marked on the map. 31N -.;.""i 0 tv ;?9IV L)8/\/ i 27/V 2~ \) F 9/tV 8t,V TVV 6W 5W 4W ,~~JV ?IAl . . '-"' L_ vv 7 W I LS OF 25-YEAR 24-HOUR PRE (; f P' T,AT I () t1J lt~'lJ T E hrT H S ()FAt\J It'4 C H Figure 3 3. Time of Concentration Because of the small size of the parcel a value of 6 minutes is assumed for the time of concentration. This is the smallest recommended value for use with the Santa Barbara Urban Hydrograph Method. 4. Calculation of Peak Flow A summary of the results of the calculations of 25 year peak flows is included in Table 2. This data indicates that the design flow for the conveyance system at the southwest corner of the parcel is 0.~6 cfs. Even though this value is representative of the combined flows from all conveyances on the parcel, it is used as the design value for each individual swale and tightline pipe included in this stormwater plan. 13 HWYDRNOl.WB2 Date: August 23, 2007 PROJECT: Hawks 13(30-2) drainage BASIN DATA Postdevelopment Basin Data Undetained Detained Area: 0.6352 (Ac) + 0.0000 (Ac) Cn: 92.0 100.0 Tc: 6 (min) 6 (min) Total 0.6352 (Ac) RAINFALL 25 yr storm: 2.30 (in) Peak Basin Rainfall ------(Qr)------- 0.4773 (cfs) 24 hr rainfall depth POSTDEVELOPMENT RUNOFF Peak Runoff From Entire Basin ------------------ -----(Qpos)------ 25 yr storm: 0.2558 (cfs) Table 2 c. Performance Standards and Goals The various thresholds of the DOE Manual are used to determine the required Minimum Requirements for this project. Table 3 is a flow chart taken from the DOE Manual to determine the minimum requirements for this project. The path for this project is indicated in red. 14 Start IIere Does the site have 35% or more of existing impervious coverage? Yes See Redevelopment Minimum Requirements and Flow Chart (Figure 2.3) Does the project add 5,000 square feet or more of new impervious surfaces? No Does the project convert 31t acres or more of native vegetation to lawn or landscaped areas, or convert 2.5 acres or more of native vegetation to pasture? No Yes Yes No ~~~ Does the project have 2,000 square feet or more of new, replaced, or new plus replaced impervious surfaces? All Minimwn Requirements apply to the new impervious surfaces and converted pervious surfaces. Tes No Minimum Requirements # 1 through #5 apply to the new and replaced impelVious surfaces and the land disturbed. Does the project have land-disturbing activities of 7,000 Yes square feet or more? No , See Minimum Requirement #2, Construction Stormwater Pollution Prevention Figure 2.2 - Flow Chart for Determining Requirements for New Development Table 3 Table 3 indicates that this project must meet Minimum Requirements #1 through #5. 1. Minimum Requirement #1 : Stormwater Site Plan This report is the Stormwater Site Plan for the Hawks project. 15 2. Minimum ReQuirement #2: Construction Stormwater Pollution Prevention Plan A complete Construction Stormwater Pollution Prevention Plan is included with this report, beginning on page 23. 3. Minimum ReQuirement #3: Source Control of Pollution This is a residential project and not subject to the requirements for Source Control BMPs. Nevertheless, the following source control BMPs are recommended for the management of lawn and landscaping areas. Common sources of pollution from lawns and landscaped areas are fertilizers, pesticides and other substances used to control weeds, insects, mold, bacteria, and other pests. (i) Landscaping Applicable Operational BMPs for Landscaping: . Install engineered soil/landscape systems to improve the infiltration and regulation of stormwater in landscaped areas. . Do not dispose of collected vegetation into waterways or storm drainage systems. Recommended Additional Operational BMPs for Landscaping: . Conduct mulch-mowing whenever possible . Dispose of grass clippings, leaves, sticks, or other collected vegetation, by composting, if feasible. . Use mulch or other erosion control measures when soils are exposed for more than one week during the dry season or two days during the rainy season. . If oil of other chemicals are handled, store and maintain appropriate oil and chemical spill cleanup materials in readily accessible locations. Ensure that employees are familiar with proper spill cleanup procedures. . Till fertilizers into the soil rather that dumping or broadcasting onto the surface. Determine the proper fertilizer application for the types of soil and vegetation encountered. . Till a topsoil mix or composted organic material into the soil to create a well-mixed transition layer that encourages deeper root systems and drought-resistant plants. . Use manual and/or mechanical methods of vegetation removal rather than applying herbicides, where practical. 16 (ii) Vegetation Management Applicable Operational BMPs for Landscaping: . Use at least an eight-inch "topsoil" layer with at least 8 percent organic matter to provide a sufficient vegetation-growing medium. Amending existing landscapes and turf systems by increasing the percent organic matter and depth of topsoil can substantially improve the permeability of the soil, the disease and drought resistance of the vegetation, and reduce fertilized demand. This reduces the demand for fertilizers, herbicides, and pesticides. Organic matter is the least water-soluble form of nutrients that can be added to the soil. Composted organic matter generally releases only between 2 and 10 percent of its total nitrogen annually, and this release corresponds closely to the plan growth cycle. If natural plant debris and mulch are returned to the soil, this system can continue recycling nutrients indefinitely. . Select the appropriate turf grass mixture for your climate and soil type. Certain tall fescues and rye grasses resist insect attack because the symbiotic entophytic fungi found naturally in their tissues repel or kill common leaf and stem-eating lawn insects. They do not, however, repel ro~t-feeding lawn pests such as Crane Fly larvae, and ar..e toxic to ruminants such as cattle and sheep. The fungus causes no known adverse effects to the host plants or to humans. . Use the following seeding and planti'ng BMPs, or equivalent BMPs to obtain information on grass mixtures, temporary and permanent seeding procedures, maintenance of a recently planted area, and fertilizer application rates: Temporary Seeding, Mulching and Matting, Clear Plastic Covering, Permanent Seeding and Planting, and Sodding as described in Volume II of the DOE Manual. . Selection of desired plant species can be made by adjusting the soil properties of the subject site. For example, a constructed wetland can be designed to resist the invasion of reed canary grass by layering specific strata of organic matters (e.g., compost forest product residuals) and creating a mildly acidic pH and carbon-rich soil medium. Consult a soil restoration specialist for site-specific conditions. . Aerate lawns regularly in areas of heavy use wher~ the soil tends to become compacted. Aeration should be conducted while the grasses in the lawn are growing most vigorously. Remove layers of thatch greater than 3/4 inch deep. . Mowing is a stress-creating activity for turf grass. When grass is mowed too short its productivity is decreased and there is less growth of roots and rhizomes. The turf becomes less tolerant of 17 environmental stresses, more disease prone and more reliant on outside means such as pesticides, fertilizers and irrigation to remain healthy. Set mowing height at the highest acceptable level and mow at times and intervals designed to minimize stress on the turf. Generally mowing only 1/3 of the grass blade height will prevent stressing the turf. Mowing is stressful to the subject species and if evidence of mental trauma to turf grasses occurs, consult a qualified vegetation psychologist such as a member of the American Society of Propeller-Heads-Who-Talk- to-Plants and arrange regular therapy sessions for your lawn. (iii) Irrigation BMPs for Landscaping: . The depth from which a plant normally extracts water depends on the rooting depth of the plant. Appropriately irrigated lawn grasses normally root in the top 6 to 12 inches of soil; lawns irrigated on a daily basis often root only in the top 1 inch of soil. improper irrigation can encourage pest proplems, leach nutrients, and make a lawn completely dependent on artificial watering. The amount of water applied depends on the normal rooting depth of the turf grass species used, the available water holding capacity of the soil, and the efficiency of the irrigation system. Consult with the local water utility, Conservation District, or Cooperative Extension office to help determine optimum irrigation practices. (iv) Fertilizer Management BMPs for Fertilizing: . Turf grass is most responsive to nitrogen fertilizer, followed by p'otassium and phosphorus. Fertilization needs vary by site depending on plant, soil and climatic conditions. Evaluation of soil nutrient levels through regular testing ensures the best possible efficiency and economy of fertilization. For details on soils testing, contact the local Conservation District or Cooperative Extension Service. . Fertilizers should be applied in amounts appropriate for the target vegetation and at the time of year that minimizes losses to surface and ground waters. Do not fertilize during a drought or when the soil is dry. Alternatively, do not apply fertilizers within three days prior to predicted rainfall. The longer the period between fertilizer application and either rainfall or irrigation, the less fertilizer runoff occurs. 18 . Use slow release fertilizers such as methylene urea, IDBU, or resin coated fertilizers when appropriate, generally in the spring. Use of slow release fertilizers is especially important in areas with sandy or gravelly soils. . Time the fertilizer application to periods of maximum plant uptake. Generally fall and spring applications are recommended, although WSU turf specialists recommend four fertilizer applications per year. . Properly trained persons should apply all fertilizers. At commercial and industrial facilities fertilizers should not be applied to grass swales, filter strips, or buffer areas that drain to sensitive water bodies unless approved by the local jurisdiction. 4. Minimum Requirement #4: Preservation of Natural DrainaQe Systems and Outfalls The natural hydrology of this site is discussed in Section IV.A Existing Site Hydrology on page 10. Both the natural hydrology and natural outfall are on a very small scale. This natural discharge is shown in Photo 7. Photo 7 The storm sewer system discharges to marine waters in a location approximately 50 feet north of the natural point of discharge for flows which remain in the natural shallow concentrated flow channel. This results in negligible change in the natural flow regime. 19 5. Minimum ReQuirement #5: On-site Stormwater Management The impacts to down-gradient properties from the surfacing groundwater from the Hawks parcel prior to installation of the curtain drain and tightline pipes is well documented. These parcels were considered to be unbuildable in that prior condition and the conveyance system was constructed to alleviate these conditions. Infiltration of stormwater runoff would have to occur on the lower portion of the site, below the septic system. Impermeable soils in this area would render any infiltration system nonfunctional. Similarly dispersion systems would severely impact down-gradient properties. For these reasons, the employment of on-site stormwater management BMPs is infeasible without causing unacceptable flooding or erosion impacts. D. Flow Control System Existing curtain drains, tightline pipes, and storm sewers collect all of the stormwater from this parcel and convey it to marine waters so stormwater flow control is not required. E. Water Quality System Because this project is a residential land use, water quality systems are not required. Operational BMPs are suggested in Section IV.C.3 Minimum Requirement #3: Source Control of Pollution, beginning on page 16 for the management of Landscaping, Vegetation, Irrigation, and Fertilizer. F. Conveyance System Analysis and Design As discussed in Section IV.A. Existing Site Hydrology on page 10, a single peak flow value of 0.26 cfs is used for the sizing of all conveyances. Stormwater collection and conveyance BMPs are shown on Detail Drawing 1 on page vii. 1. Interceptor Swale DesiQn Conveyances on this site are interception swales around the parcel perimeter as shown on MAP X on page Y and the existing tightline pipes shown on Map 4 on page vi. The swales are hydraulically modeled as trapezoidal channels. All will be of the same dimension and all will have the same design flow. The 20 gentlest slope on the site is from north to south across the bottom (west side) of the parcel where the slope of the swale will be 4.5%. This is used as the design value for all of the swales. Table 4 shows calculations of the capacity of the interceptor swales. The calculations indicate that the swales should be constructed with an 18" wide base and 3 : 1 (horizontal : vertical) side slopes and with a minimum longitudinal slope of 4.50/0. This is consistent with the design detail drawings. OPEN CHANNEL FLOW THROUGH A TRAPEZOIDAL CHANNEL - MANNINGS EQUATION v = 1.486/n Q = VA X R2/3 X sl/2 where: S = Sf (for uniform flow) (ft/ft) R = A/P = Hydraulic Radius (ft) A = (b + zO) x D = Area of Flow (sq ft) P = b + 2D~(1 + Z2) = Wetted Perimeter (ft) GIVEN: n = 0.18 (Manning's n value) b = 1.5 (width of channel bottom in feet) Z = 3 (channel sideslope, ie., for a 2:1 sideslope, Z=2) Sf = 0.045 (slope of channel in ft/ft - uniform flow only) D = <varies> (depth of flow in feet as tabulated below) CALC: Approx. depth of flow for various events Design Flow = 0.26 cfs ===> D (ft) Q (cfs) V (fps) 0.10 0.061 0.3367 0.13 0.090 0.3828 0.15 0.124 0.4245 0.18 0.164 0.4627 0.20 0.209 0.4983 0.23 0.260 0.5317 0.25 0.317 0.5633 Table 4 2. TiQhtline Pipe Hvdraulic Capacity The capacity of the tightline pipe system was checked using the Hazen/Wiliams formula for friction losses and inlet controlled conditions for the minimum necessary depth of the inlet. Tabulated results are contained in Table 5. These calculations indicate that the tightline has ample capacity to carry the design flow and inlet conditions at inlets and catch basins will not be a controlling factor. 21 STORM SEWER PIPE - BARREL CAPACITY & INLET CAPACITY Assumptions: HazenlWilliams C value = 80 Min barrel slope is based on pipe flowing full and is the slope necessary to just overcome friction losses in the pipe barrel Min depth of inlet is based on a square edge circular inlet (inlet coefficient = 0.62) and is that head necessary to get the water started flowing down the pipe. Pipe Dia. ==> 4 in. 6 in. Sin. ------------------------- -------...-.-......-------------- ----------------------- Min Min Min Depth Depth Depth to Min to Min to Min Flow Pipe IE Barrel Pipe IE Barrel Pipe IE Barrel (cfs) (ft) Slope (ft) Slope (ft) Slope ------------- ------------- ---.....------ --.----------- ------------- ------------- -------------- 0.10 0.22 0.42% 0.26 0.060/0 0.34 '.0.01% 0.11 0.23 0.500/0 0.26 0.070/0 0.34 0.020/0 0.12 0.24 0.59% 0.27 0.080/0 0.34 0.02% 0.13 0.26 0.68% 0.27 0.090/0 0.34 0.02% 0.14 0.27 0.78% 0.27 0.110/0 0.34 0.030/0 0.15 0.29 0.89% 0.27 0.120/0 0.34 0.030/0 0.16 0.30 1.00% 0.28 0.140/0 0.34 0.03% 0.17 0.32 1.120/0 0.28 0.160/0 0.34 0.04Ok 0.18 0.34 1.240/0 0.28 0.170/0 0.34 0.04% 0.19 0.36 1.370/0 0.29 0.190/0 0.35 0.050/0 0.20 0.38 1.51% 0.29 0.210/0 0.35 0.05% 0.21 0.40 1.650/0 0.30 0.230/0 0.35 0.060/0 0.22 0.42 1.80% 0.30 0.250/0 0.35 0.06% 0.23 0.45 1.950/0 0.31 0.270/0 0.35 0.07% 0.24 0.47 2.11 % 0.31 0.290/0 0.35 0.07Ok 0.25 0.50 2.280/0 0.32 0.320/0 0.35 0.08% 0.26 0.53 2.450/0 0.32 0.340/0 0.36 0.080/0 0.27 0.55 2.630/0 0.33 0.370/0 0.36 0.090/0 0.28 0.58 2.81% 0.33 0.390/0 0.36 0.10% 0.29 0.61 3.000/0 0.34 0.420/0 0.36 0.100k 0.30 0.64 3.20010 0.34 0.440/0 0.36 0.11Ok Table 5 22 -; V. CONSTRUCTION STORMWATER POLLUTION PREVENTION PLAN This portion of the plan was prepared with the goal of preventing damage to adjoining or downstream properties due to erosion and sediment deposition and preventing the degradation of the quality of the receiving waters during the construction phase of this project. This Construction Stormwater Pollution Prevention Plan (SPPP) is to be used in conjunction with the remainder of the overall Stormwater Site Plan, which contains much of the descriptive material upon which this Construction SPPP is based. To ensure that the provisions of this Erosion and Sediment Control Plan are followed during construction, the complete text of this Erosion and Sediment Control Plan should be included in the construction plans for this project. Where formal construction plans will not be prepared for all or portions of the work, a copy of this document should be made available to the contractor and appropriate subcontractors. Subcontractors that will not be receiving copies should be made aware of the plan's existence and advised where copies can be obtained. Water quality controls, commonly referred to as Best Management Practices, or BMPs, are necessary to prevent three distinct types of impacts. The first consists of damage done as the result of soils being taken up by running water. This type of damage typically consists of rilling, rutting and loss of topsoil. The second type of damage is the degradation of water quality that occurs as the water transports the smaller soil particles. The third type of damage occurs when the running water reduces its velocity and drops the suspended soils. The Erosion arid Sediment Control features (BMPs) of this plan are designed to address all three types of damage with the emphasis on preventing the initial soil uptake. Successful prevention of soil uptake will also prevent damage caused by degradation of water quality and by soil deposition. While the measures described below for preventing soil uptake should theoretic~lIy prevent any removal of soil, common sense advises that additional measures will be necessary and indeed, the DOE Manual requires additional measures. These additional measures will allow deposition of transported soils under controlled conditions before flows leave the project site or enter the receiving waters. Detail drawings for construction stormwater pollution prevention are included at the beginning of this report. Specific drawings are referenced as they are dis'cussed in the narrative below. A. Clearing Limits Appropriate clearing limits, property lines, easement lines, and similar boundaries shall be determined prior to starting construction. Clearing, 23 grubbing, grading and similar operations shall not begin until the appropriate limits are staked in the field. Once these stakes are set, care shall be taken that the stakes are not disturbed. B. Construction Access In addition to the following general requirements, the specific requirement regarding construction access contained in the Jefferson County Standard Stormwater Site Plan Notes on page xii shall be followed. It is expected that minor amounts of soil will be tracked onto paved roads, especially when unexpected circumstances such as rains and delays occur. To prevent this from becoming a nuisance or source of sedimentation, the roads shall be cleaned thoroughly at the end of each day if there is evidence of any significant accumulation of soil. Sediment shall be removed from roads by shoveling or sweeping and be transported to a controlled sediment disposal area. Washing of the street shall be allowed only after sediment is removed in this manner. Wherever construction, delivery, and similar vehicles enter paved roads from this project, the following provisions shall be followed to minimize the transport of soil onto the paved road. During periods of dry weather (where the soil is too dry to adhere to the tires of construction vehicles) construction vehicles may access paved streets directly from the project site with monitoring and occasional sweeping of the paved street as necessary to prevent accumulations of soil. During periods of wet weather (where soil readily adheres to the tires of vehicles) the vehicles may access graveled roads directly from the project site as necessary, but shall not access paved roads without first having been routed over areas where existing grass or other vegetation remains or routed down a minimum of 150 feet of graveled road. Access routes over grass or other vegetation shall be changed occasionally to ensure that wheel ruts are not allowed to develop and that the vegetation is not unduly worn down. C. Flow Rate Controls Flow controls are not required on this project due to the existence of tightline conveyances directly to marine receiving waters. D. Sediment Controls Three sediment controls shall initially be utilized on this site. Additional controls shall be installed if conditions dictate that additional protection is necessary. The first control is stabilization of the interceptor swales. The swales and any adjacent spoils shall be covered with filter fabric as shown on Detail Drawing 2 on page viii. 24 The second control is the wattles to be placed below the limits of disturbed soils as shown on Detail Drawing 3 on page ix. The third control is the inlet protection for the catch basins as shown on Detail Drawing 4 on page x. E. Soil Stabilization From October 1 through April 30, no soils shall remain exposed and unworked for more that 2 days. From May 1 to September 30, no soils shall remain exposed and unworked for more than 7 days. This condition applies to all soils on site, whether at final grade or not. Soils shall be stabilized at the end of the shift before a holiday or weekend if needed based on the weather forecast. The actual type of soil stabilization used is to be determined by the contractor based on the requirements of the DOE Manual to match his construction procedures. Sediment controls as described in Section V.D. Sediment Controls above are required in additional to the requirement for soil stabilization. F. Slope Protection Any slopes such as at the ends of retaining walls or the sides of stockpiles shall be stabilized as required in Section O. Soil Stabilization above. G. Drain Inlet Protection Both of the catch basins located at the bottom of the parcel shall be protected as shown in Detail Drawing 4 on page x. H. Channel and Outlet Stabilization The swales and any adjacent spoils shall be covered with filter fabric as shown on Detail Drawing 2 on page viii. I. Control of Pollutants All potential pollutants other than sediments that may occur on the site during the construction process shall be handled and disposed of in a manner that does not cause contamination of stormwater. 25 1. 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 the project except in full compliance with all applicable federal, state and local laws and regulations and the recommendations of the supplier of the substance. The product label or instructions for use and the Material Safety Data Sheets (MSDS) for such products shall be kept on the site until the product has been used up or removed from the site and properly disposed of. While not commonly thought of as a hazardous material, common fertilizer can be very damaging if allowed to enter receiving waters. Fertilizers shall only be used in accordance with the recommendations 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 materials, work in the vicinity shall be immediately stopped and the following agency notified: Washington State Department of Ecology, (206) 459-6000 during normal business hours or (206) 753-2353 after hours. If the incident presents a threat to life, health, or property, the Fire and Police Departments shall be notified by dialing 911. 2. Petroleum Spills The following requirements are included to ensure compliance with Part 40 of CFR 112 in cases where SPCC Plans are required. They shall be followed on all projects. Storage of fuel for construction vehicles and fueling of construction vehicles shall be performed in accordance with the following requirements: (i) Driver Training All employees 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, pumps, hoses and fuel delivery equipment. (ii) Fueling of Vehicles Fuel nozzles shall be locked when not attended and hoses shall be rewound or otherwise properly stored when not in use. Unattended fueling which relies on the proper operation of automatic shutoff nozzles shall not be permitted. 26 :tl i (iii) Parking of Fuel Tankers Parking areas for fuel trucks shall be selected such that spills will not leave the area. Fuel trucks shall not be parked closer than 25 feet to a conveyance BMP such as a grassy swale or interceptor swale. When fuel trucks must be taken to other portions of the project to fuel equipment, they must be continuously attended or returned to the staging/storage area. Fuel trucks shall be locked with the wheels chocked when unattended and not in use. (iv) Containment of Spills Spills shall be immediately diked and every effort made to stop spillage. Each fuel truck shall carry a long handled shovel for use in containing spills. In the event of a spill, the U. S. Environmental Protection Agency, Seattle, Washington (206) 442-1263, shall be notified as soon as possible. If the magnitude of the spill is such that it presents an immediate threat to life, health, or property, it shall be promptly reported by dialing 911. J. Control of De-Watering Underground utility construction shall proceed subject to the following criteria: A major source of potentially contaminated flows is from pumping or otherwise dewatering trenches. For this reason, flows discharged from pumping or other method of trench dewatering shall be closely monitored and, except where there is no visible turbidity, treated as described below in the Section titled "Dewatering Construction Sites." Where feasible, no more than 500 feet of trench shall be opened at one ti me. Where consistent with safety and space considerations, stockpiles of excavated soils shall be placed on the uphill side of the trench. Any such stockpiles shall be protected from erosion as provided for in this plan. Trenches shall be backfilled and revegetated as soon as reasonably possible following placement of utilities. Wherever trenches run more or less straight up and down a slope, either the backfill shall be mounded over the trench or waterbars or similar BMPs shall be utilized as necessary to prevent the backfilled trench from becoming a water course. Simply covering the exposed soil may not prevent the trench from conveying waters. Where the upstream end of a pipe is subject to inundation, it shall be temporarily capped or plugged at the end of each day's work to prevent soil from being washed into the pipe. 27 The underground utility locate service, 1-800-424-5555, shall be called a minimum of 48 hours (2 working days) prior to beginning any excavation and arrangements made to have all buried utilities marked. K. Maintenance of BMPs This section constitutes the Operation and Maintenance Manual for the erosion and sediment control BMPs used during the construction phase of this project. Most of the various BMPs required to maintain water quality during the construction phase of this project are of a temporary nature. They are neither intended nor expected to remain in service for months at a time. The typical BMP often has a life expectancy of only 6 - 12 weeks unless time and effort are expended to bring it back to its original condition. Foul weather, rough use, overloading and similar conditions will reduce the life of these items. It is critical that all of the erosion and sediment control BMPs be maintained in their intended condition until they have served their purpose and are ready to be removed. The project foreman shall inspect the various parts of the system at least once daily during rainy weather. In addition, the foreman shall perform additional inspections during or immediately after significant rainfall. Any damaged or non-functioning components of the system shall be repaired before noon of the next day. In addition to verifying that the various BMPs are functioning as intended, the foreman shall check for formation of rills, deposits of silt and similar indications that the system is not functioning properly. If it is found that the system is not performing its role in preventing erosion and sedimentation, additional BMPs shall be provided as necessary. Specific maintenance instructions for the various erosion and sediment control BMPs are contained in the DOE Manual. L. Project Management The following guidelines are not intended to be a substitute for common sense and good judgment. They must be tightened when necessary to accomplish the objective of preventing erosion and siltation. They may be relaxed after consulting with the local authority when the situation will allow a lesser level of protection. 28 1. Phasing of Construction The lower portion of the site, including the septic system, interceptor swales, and catch basins, should be installed first if at all practicable. As this area is revegetated or is covered with grass, it will act as a filter medium for minor sheet flows leaving the area of home construction. 2. Seasonal Work Limitations From October 1 through April 30, clearing, grading, and other soil disturbing activities shall only be in consultation with the local authority and upon a consideration of the following: 1. Site conditions including existing vegetation coverage, slope, soil type, and proximity to receiving waters; and 2. Limitations on activities and the extent of disturbed area; and 3. Proposed erosion and sediment control measures. 3. Coordination with Utilities and Other Contractors The contractor shall coordinate his work with other entities to the extent necessary to avoid the need for additional excavation and soil disturbing a ctiviti es. 4. Inspection and Monitorina The project foreman shall inspect the various parts of the system at least once daily during rainy weather. In addition, the foreman shall perform additional inspections during or immediately after significant rainfall. Any damaged or non-functioning components of the system shall be repaired before noon of the next day. In addition to verifying that the various BMPs are functioning as intended, the foreman shall check for formation of rills, deposits of silt and similar indications that the system is not functioning properly. If it is found that the system is not performing its role in preventing erosion and sedimentation, additional BMPs shall be provided as necessary. 5. Maintainina an Updated Construction SWPPP To ensure that the provisions of this Erosion and Sediment Control Plan are followed during construction, the complete text of this Erosion ~nd Sediment Control Plan should be included in the construction plans for this project. Where formal construction plans will not be prepared for all or portions of the work, a copy of this document should be made available to the contractor and appropriate subcontractors. Subcontractors that will not be receiving copies should be made aware of the plan's existence and advised where copies can be obtained. 29 VI. SPECIAL REPORTS AN.D STUDIES There are no special studies applicable to this project. VII. OTHER PERMITS This project will need a building permit and a septic permit. VIII. OPERATION AND MAINTENANCE MANUAL Due to the limited size and scope of this project, Operation and Maintenance issues are discussed for each BMP as they are introduced in this SSP. I i . i , ! 30