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APPROVED STM RESUB3 BLD2023-0692+CSWPP+9.26.2024_8.59.14_AM+4524862BLD2023-0692 RESUB Sep 30 2024 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT BK Chen Townhouse 7103 210th ST SW, Edmonds WA 98026 Construction Stormwater Pollution Prevention (CSWPP) Report �F WA C") 1 3A 52183 ® ISTEg� 09/25/24 Prepared by: he Sheng, PE, LEED Green Associate SH Fine Consulting November 15, 2020 Revised May 30, 2024 Revised Sept 25, 2024 COMPLIES WITH APPLICABLE CITY STORMWATER CODE 1 12/13/2024 1 Tables of Contents 1. Introduction 2. Existing Conditions 3. Proposed Construction Activities 4. Erosion and Sediment Control Measures Element #1: Preserve Vegetation/ Mark Clearing Limits Element #2: Establish Construction Access Element #3: Control Flow Rates Element #4: Install Sediment Controls Element #5: Stabilize Soils Element #6: Protect Slopes Element #7: Protect Drain Inlets Element #8: Stabilize Channels and Outlets Element #9: Control Pollutants Element #10: Dewatering Element #11: Maintain BMPs Element #12: Manage the Project Element #13: Protect Low Impact Development BMPs 5. Construction Sequence Appendix A: Site Plan Appendix B: Temporary Erosion and Sediment Control Plan Appendix C: SWPPP BMPs 1 1 1 2 2 2 2 2 2 2 2 2 3 3 3 3 3 3 4 5 6 1. Introduction This Construction Stormwater Pollution Prevention (CSWPP) report has been prepared for the City of Edmonds townhouse project. The project site consists of a single, rectangular parcel located at 7103 210th ST SW, Edmonds, WA, 98026. The parcel is approximately 11,326 square feet in size, and bounded by access roads to the east and west, private residence to the north and 210th ST SW to the south. There is an existing single -story dwelling unit and carport that will be demolished. The proposed development consists of a 6-unit townhome development. The purpose of this CSWPP report is to describe the construction activities and all temporary and permanent erosion and sediment control (ESC) measures, and stormwater pollution prevention and spill (SWPPS) measures. This report has been prepared in compliance with the 2019 Stormwater Management Manual for Western Washington (2019 SWMMWW) and the City of Edmonds 2019 Stormwater Code and Reference Documents. Each of the 13 CSWPPP elements per 2014 SWMMWW Section 1.2.5.2 are considered in this report. 2. Existing Conditions The site is generally flat with gentle slopes from north to south with grades of approximately 5%. There is an existing single -story dwelling unit and carport that will be demolished and removed. Current storm water runoff from the roofs are discharged to the surrounding lawn surface via downspouts and sheet flow from the carport roof. Runoff follows the existing grade of the site towards 210th St SW and into the curb and gutter drainage system along 210th ST SW. Existing driveway runoff sheet flows into the curb and gutter drainage system along 210th ST SW. There is no evidence of downstream flooding and no drainage complaints related to this parcel. There are no known critical areas onsite or adjacent to the site. No evidence of site instability or ground movement was found by the Geotechnical Engineer at this site. Refer to Geotechnical Report attached in Appendix E. The site is not within a known Landslide Hazard Area, Erosion Hazard Area, Coal Mine Hazard Area, or Seismic Hazard Area. 3. Proposed Construction Activities The proposed development includes the demolition of the existing structures, and the construction of a new, 6 unit townhome development, and associated walkways and driveways. Refer to Appendix A for the proposed Site Plan. Construction activities will include site preparation, ESC installation, excavation for building foundation, foundation and building construction, and parking lot and driveway paving. Construction will be phased. Exact schedule will be determined at a later date. Construction sequence is outlined below. Excavation activities will be limited to the dry season. 4. Erosion and Sediment Control Measures The 13 CSWPPP elements listed in the 2012 Stormwater Management Manual for Western Washington with December 2014 Amendments are considered below. Applicable BMPs and City of Edmonds Addendum Checklists are listed in Appendix C. Element #1: Preserve Vegetation/ Mark Clearing Limits Prior to any site clearing or grading, undisturbed areas shall be delineated using either plastic or metal fencing per BMP C 103. Existing vegetation is preserved to the maximum extent feasible per BMP C 101. Clearing limits are shown on the TESC Plan. Refer to Appendix B. Element #2: Establish Construction Access Construction access shall be limited to one route. The existing driveway shall be used as the entrance and exit, and shall be used as the stabilized construction entrance per BMP C 105. Refer to Appendix B. If stabilized construction entrance is not sufficient in reducing sediments tracked onto road, wheel washes per BMP C106 shall be installed. Element #3: Control Flow Rates Flow rates leaving the site are not anticipated to increase for this site during construction. Permanent flow control facilities (infiltration trench) shall be installed as early as feasible, and clearly identified with flagging to protect from siltation during the construction phase. Check dams (BMP C207) and wattles (BMP C235) shall be used on sloped areas. Element #4: Install Sediment Controls Silt fences shall be installed downslope of all disturbed areas per BMP C233. Silt fences shall be installed prior to upslope grading. Refer to Appendix B for location of silt fences. Element #5: Stabilize Soils All disturbed areas shall be protected using temporary covers measures such as mulching (BMP C121), erosion control nets, blankets (BMP C122) or plastic covering (BMP C123), or temporary seeding (BMP C 120). Temporary cover shall be installed if an area is to remain unworked for more than seven days during the dry season (May 1 to September 30) or for more than two consecutive working days during the wet season (October 1 to April 30). Cover details are shown on the TESC Detail Plan. Refer to Appendix B. Element #6: Protect Slopes Excavation methods used have been designed to minimize erosion and reduce slope steepness. Surface roughening, mulching (BMP C121), erosion control nets, blankets (BMP C122) or plastic covering (BMP C123) shall also be used to protect slopes with disturbed soils. Excavated material shall be placed upslope of trenches, and check dams may be used where necessary for temporary soil stockpile protection. Element #7: Protect Drain Inlets Inlet protection per BMP C220 shall be installed in all stormwater inlets immediately downstream of the project site to prevent sediment ladened water from entering the stormwater system. Refer to Appendix B for locations. Inlet protection shall be cleaned or replaced when sediment has filled one-third of the available storage. Inlet protection shall also be installed for catch basins constructed during the project. Element #8: Stabilize Channels and Outlets This project is not anticipated to impact adjacent channels and outlets. There are no onsite conveyance channels. Element #9: Control Pollutants All pollutants, including waste material and demolition debris shall be handled and disposed of off -site in a legal manner that does not cause the contamination of storm water. There are no onsite fueling tanks or sources of chemical pollutants anticipated for this project. Washing of concrete trucks and maintenance of heavy equipment and vehicles shall not occur onsite. Contaminated surfaces shall immediately be cleaned following any spill incidents. Element #10: Dewatering Dewatering is not anticipated to be necessary for this project. Element #11: Maintain BMPs All BMPs shall be maintained as needed to ensure continued performance of their intended function in accordance with BMP specifications. All temporary erosion and sediment control BMPs shall be removed within 30 days after achieving final site stabilization, or after BMPs are no longer needed. Element #12: Manage the Project The SWPPP shall be maintained, updated and implemented as outlined in this report and in accordance with the 2012 Stormwater Management Manual for Western Washington with December 2014 Amendments. Project will use phase development to the maximum extent feasible and consider seasonal limitations. Element #13: Protect Low Impact Development BMPs The infiltration trench shall be clearly identified with flagging or high visibility fencing. Vehicular and foot traffic over the area will be limited. 5. Construction Sequence 1. Hold an onsite pre -construction meeting. 2. Flag or fence clearing limits. 3. Install catch basin protection. 4. Grade and install construction entrance. 5. Install perimeter protection (silt fence). 6. Construct sediment pond(s) and/or trap(s) if necessary. 7. Construct surface water controls where necessary, simultaneously with clearing and grading for project development. 8. Maintain TESC measures in accordance with City standards and manufacturer's recommendations. 9. Relocate surface water controls or TESC measures, or install new measures so that as site conditions change, the TESC is always in accordance with the City of Medina Temporary Erosion and Sedimentation Control Requirements. 10. Cover all areas that will be un-worked for more than two days during the wet season (Oct 1 - April 30) or seven days during the dry season (May 1 - Sept 30) with straw, wood fiber mulch, compost, plastic sheeting or equivalent. 11. Stabilize all areas within seven days of reaching final grade. 12. Seed or sod any ares to remain un-worked for more than 30 days. 13. Upon completion of the project, stabilize all disturbed areas and remove TESC measures if appropriate. 3 Appendix A: Site Plan unnea jates -- ss ss �� HOUSE #7113 10^ i�Z F Postal Service �214°- B2 ` - - - - - - 20e1h St sw \ �' _ 2a"=cga$_ -----ss�rs�o�74.1C 5T,� ji P.CORNER P.CONER > B4 ' _ _ Q_. __ - 4"-C o Q - . i� 10'-0" �e n� 0"-F\ „ 1 - w a w o w � N TOP 4 - - - S-7W _ y Park 210 Q Edmonds, WA 98026 � coNc ALL 409 408.60 II FF=409.10' I I 3 one,ew o,"s TOP 4 4.0 408.40 5 -FT CONIC N R T�NG WALL,I 1ST FLR: 38.5'X21' (808.5SF) CO •� I ' a f SITE s E va. -2ND FLR ' 9.5XSF� '+BUMP -OUT FL�Q I4..•,• I s ®KuzmasF,shMa,ket J I II ( ) �6I .',: virginiamasonEdmonds -3RD FLR •39.5'X21'+BUMP-OUT I I I s Family Medicine Enter{ y I 4m.34-ROOFLII 7 I '' 1 nkay F Banner Bank© Q I I 3 Clearwater Ca, Wash ,sw azm$w 212 stmssw 21 401.14 I f Me9:cTo � �CONC WALL J 407.14 II 3 otaY TOP 1z.o I II%I FF=407.84' Pa,k 2129 �� CONC WALL I III 1ST FLR: 38.5'X21' (808.5SF) " """I �" ca,MaxQ I I �3� TOP 0.0 I -2ND FLR :39.5'X21'+BUMP-OUT ( I y y (8' SF) I 3 SEAWEED Cannabis 4 -3RD FLR :39.5X21'+BUMP-01JT I . 407.2 (' I VICINITY MAP N.T.S. 1 S. TBACK I I-ROOFLINE I 3 I C � I N N laa7.z 4c7.o I lI II FF=407.84' I 3 11/ 1ST FLR:38.5'X21' (808.5SF) I GENERAL INFO: I -2ND FLR :39.5'X21'+BUMP-OUT / Z I I III I (837 SF) I GAR AGE/RECYCL, 0 o SITE ADDRESS: 7103 210TH ST. SW, EDMONDS, WA 98026 N I �-3RD FLR - 39.5 X21'+BUMP-OUT I TYR. Br I I (837 S I OWNER: HARR CHEN PROPERTIES, LLC a 4°zz 10'-0„ TEL: 206 331 5725 P N FI I I-ROOFLINE S. SETBACK SITE DATA: I 7 LOT AREA: 11,201 SF 4a .z 4o7.b j 1 II FF=407.18' ZONING: EAT PU P, 3-FT PARCEL #: 00566900100601 I 22'_0" II , 1ST FLR:38.5'X21' (808.5SF) a R LESS3IN HEIGHT 0 7/ ASPH LT P VEM 7 I 2ND FLR :39.5'X21'+BUMP-OUT 4 - LEGAL DESCRIPTION: (537 SF) ri� SEATTLE HEIGHTS DIV 4 BLK 001 D-01 - BEG SW COR LOT 6 TH ;. N / I aosle ae I j�-3RD FLR (839,37 �>'+BUMP-OUT I 3 E AUG S LN 30.01FTTO POB TH NWLY TAP 3OFT E OF W LN SD / I� I LOT151.14FT NLY FIRM S LN SO LT TH E 74.10FTM/L TO E LN SD N a°ROOFLINE I - i I LT TH S ALG E LN SD T M/L TO E LN SD LOT TH S AEG E LN I j I ,. SDLOT TO SE COR TH W AEG S LN SD LOT TO POB EXISTING 4oss� 11I FF-406.81' I �' EXISTING BUILDING TO BE DEMOLISHED: y n GRADE� o\ I 1 YEAR BUILT: 1947 �N cb I I I 1ST FLR:38.5'X21' (808.5SF) I o? 3 I II 1I -2ND FLR '(837XSF)+BUMP-OUT 1ST FLOOR: 768 SF I I F. BASEMENT: 732 SF I I 1 11l -3RD FLR • 39.5'X21'+BUMP-OUT 1 CARPORT: 572 SF 1 1 (837 SF) 3 PROPOSED CONSTRUCTION: UTILITY EASEMENo Q I 406.11 I I I -ROOFLINE i 1 -F I 4' CONC. WALKWAY 6 ATTACHED 3-STORY TOWNHOUSES W/ EACH UNIT FLOOR AREAS AF 8105070180 N I I II I 1ST FLOOR: 334 SF, 2-CAR GARAGE:447 SF 406.31 II 3 2ND FLOOR: 837 SF 40s1131 I/ FF=406.5' TRYPFNE a"-F I 3RD FLOOR: 837 SF 1ST FLR:38.5'X21' 808.5SF I I 4' CO C. WALKWAY 0� I22,�Q'li -2ND FLR :3937XS21'+BUMP)OUT i I 1 ,.TREE PROTECTION LOT COVERAGE CALCULATIONS: -3RD FLR :39.5X21'+8UMP-0U7 (45% max.) TREE TO E DRIVE AY 837 � ° -F I W BUILDING FOOTPRINT 6X837SF =5022 SF R01g1FI W BIKE RACK,SEE REM VED, T P. _ 23 - C�406 T3lJICDIG HEIGHT UBR-1/CV4.2 7� h:F( `( 212„_F 3 Q / i LOT COVERAGE 5022.0 SF 11201 SF=44.8% OK 1 CALCULATION BOX FOR DETAILS 1� I � N A L 1 " 2 40s.8 BUILDING HEIGHT CALCULATIONS: O1 I I 3 8.5' 0 0 MF ... 0 y y F2 - - - - - CON 18PAe1 WALKWAY POINT A B C D �N " F3 -IALL PEDESTAL I ELEVATION 406 413.60 41258 406.91 �P.CORNER 619.5' F41 k « AVERAGE 1639.09/4=409.77 Ff FF EXI F.H. TO RETAINED IF T IS CO FIRMED WITHH THE FIRE MA SHAL rn MAX HEIGHT 409.77+25=434.77 CB N z 4\c C. WALKWAY MAX ROOF HEIGHT 409.77+25+5=439.77 w - Iwl w ao 4 ri, `• %': o ', l l aN 4/L3 R ORNER RIM 405.34 f� w `mow. ;�/' ETPIL �i ew AMP DI ClSEESPROJECT E: E (12 N) 402.09 -SD-SD SD S0'L6NE-MADILBO SD .. .. .. 'W' W W IE (12"S) 400.40°- sD_ SD- sD 1 - w E (12"E/W) 400.39�Rz c� SD- SDI S SD- ) I CIVILS FOR FULL CONSTRUCTION PLANS / SDI SDI SD�� SD / irrigation aPrinklin9 CB TYPE1(SOLID LID) I ce 01.40 TYPE'/ �b snap be obtained RIM 408.59 RIM TYPE'405.40 6-N +1-EXI T((TO BE UPGR{��DED)) from Public Works Cross 12"GONG E IE 402.73 / ALL �w WITH 1.5$' PEX PIPE W/TRACER �• Connection 12"GONG W IF 403.30 12"CONC W IE 402.67 / WIRES, 6 UNITS W/ WATER & / Control Specialist - Jeff 12 GONG N IF 403.24 y-- SPRINKLING, AND 1 IRRIGATION METER. Koblyk. Rhona: n I N(PROJECT REFERENCE DATUM)- _ / 4z5-771-0235 or e-1 - 2�tH ST SW eff.koblyk �edmondswa.gov.� ECTO REFER WA-100/SHEET CU6.2 y (E) 6"PVC SEWER1PIPEOW /� \ N (TO BE VERIFIED 8 SUcTBJECT TO INSPECTION) J E D LA V \\\ I 1 101 0 6• 301 20• \ s o \ SS- Ss- SS_ SS_ Sg Ss- SS- SS- ss-I 11 \\ ss- ss- ss-�- SS- sce1.B: 1' 111 lo• \ .•., _. ,_.�. _.... f 1 SS- SS- SS- SS- SS- SS- SS- SS- SSA - THE BUILDING HEIGHT RECTANGLE REVISED, NO AFFECT ❑N ELEVATIONS OTHER REVISIONS IN RESPONSE TO ENGINEERING REVIEW COMMENTS HOME TECH 13608 SE 51ST PL BELLEVUE, WA 206 778 2431 hometechwa@gmaii.com �ewoe easyl�� 32229 �R�/S7'CQ� IWVAL N O CID Z G 0 N W W W 3.1 CO Z :) N Z Z Z p a LJJH M V o REVISIONS DATE �l JAN 25, 2024 MAY 12, 2024 DESIGN: Y. S. DRAWING: H. H. CHECKI Y. S. DATE: JAN 25, 2024 SCALEI AS SHOWN SHEETI 1 SITE 1 Appendix B: Temporary Erosion and Sediment Control Plan REQUIRED TREE PROTECTION MEASURES -Protect trees by complying with guidelines outlined in ECDC 20.10 - Tree protection fencing shall be installed as close as possible to the proposed foundation lines while still providing access for the building construction. - Said fencing shall be 3' tall and signage shall be placed on the fencing as per ECDC 23.10.070. -NO disturbance in the TPZ with noted exceptions. - NO root cutting in the TPZ. -If stumps near retained trees are to be excavated, care must be given to potential encounters with the roots of trees scheduled for retention. It would be better to leave the stumps in place or have them ground below the surrounding grade. -Pruning for building clearance must be performed by an experienced professional and should be limited to less than 15% of live growth and done as per best management practices. - Any bare soils inside the tree protection fencing should be covered with a maximum of 3" of mulch material. - Maintenance of trees throughout the construction period by watering. - Retained trees shall be reassessed after project completion or within two years from the date of this report (June 10, 2024) for changing health, condition, or structure by completing a basic visual assessment GRADING CUT (NET); 310 CYD GRADING FILL (NET): 160 CYD - Pest control inspection and measures shall be provided prior to onsite demolition or construction activities. - If underground storage tank(s) are encountered it must be decommissioned in accordance with local fire department regulations. In the event that soil or groundwater contamination is encountered during removal, cleanup must be in accordance with ecology regulations (WAC 173-340). END OF WALL 3.4' S X 0.4' E ► 8" PVC SW IE-414.86 /e 18" PVC N IE=414.86 I 4" PVC E IE=415.39 z LOT A SHORT PLAT AFN 200511035008 J I SD- SD- O IV O I \As SS 7 P P %LLII - _. 6' y POD 2 X L./IV z«x xr�x -__ 0 I1 1 I y - - I - L Y - - S{- - „ I N `�\ - � '� � 408.60 ON LINE I9 IFI �IN LINE0 TO BE US D I I CONSTR TION 407.34 & TBR AT T END I I9 IOq THE CONSTR N TION I I� y I v I x I A DRWAY BUILDING FOUNDATION 1 Sa\ N i - LIMIT 7 AREA I SDMH W/GATE VAVVE RIM=410.43 6" CMP NW IE=402.96 12" CMP S IE=403.13 I I rn zh�0�m WORK WITH CV3.2 PLAN FOR NOTES & DETAILS I II I GRADING/TESC PLAN 10' 0 6' 10' 20' SCALE: 1" = 10, I I I UTILITY EASEMENT I AF 8105070180 III APPROVED FOR CONSTRUCTION CITY OF EDMONDS DATE: BY: CITY ENGINEERING DIVISION ADDRESS SIGN MULTIPLE HOUSES (NEIGHBOR'S) CB TYPE 1 RIM=404.86 6" PVC N IE=403.14 6" PVC S IE=403.06 CB TYPE 1 RIM=405.34 12" CONC N IE=402.09 -w 12" CONC S IE=400.40_SD 12" CONC E, W IE-400.39 I 1 40a.o I I I- ox x 407.34 I C) Ic�T � //�' ' , S 407.5 TS NG SEIN SEW R LIN I ►��I1�% �_ . I F_(`F_NIF) ® FOUND MONUMENT AS NOTED SET 24" X 1/2" REBAR WITH CAP STAMPED "LS 32441" 0 FOUND MAC AND WASHER AS NOTED O FOUND IRON PIPE OR REBAR AND CAP (RBC) AS NOTED M WATER METER _ 2.4' E WATER VALVE 1 X'X:f- FIRE HYDRANT 3 O_) UTILITY POLE /0\--O UTILITY POLE WITH LIGHT E-- GUY ANCHOR ® MAILBOX 20 SIGN 3 � a GATE POST D D m I I Z 0TYPE I CATCH BASIN (.000 Z Z I3 0 o 0 O STORM DRAIN MANHOLE O z np ❑® STORM DRAIN CLEAN OUT � 3 I Can C .ZC7 I U, SANITARY SEWER MANHOLE 3 Fel SANITARY SEWER CLEANOUT -X-X- FENCE (TYPE NOTED) OR i GAS j SDSD- STORM DRAIN Ix 3 -W-W- WATER x -P P- OVERHEAD UTILITIES 3 I -sS ss- SANITARY SEWER "I 3 LOCUST (L) E CEDAR (-C) 1 "-L 3 1 >>T � FIR (F) TESC LEGEND: 3 PINE cPc ii /3, 2 T 44 ASPHALT TREE 5� A 1 " F PR TECTION 4 INLET PROTE TION WILL BE i N CONCRETE PROVIDED ON W 2.5W - 3 / CONSTRUCTED CA BASINS D 2 i\�r-I FF SILT FENCE, ER-900 CE CONS. ACCESS, ER-901 TS COVER, E1.15 cPc COVER, E1,20 STORM DRAIN INSERT, ER-902 MU MATTING/ROLLED EROSION M U) CONTROL PRODUCTS E1,15 -F. SI E SEWER CONNE TION R �J 3 SEE CV3,2 FOR DETAILS 406 V, P R CITY OF EDMO S I rl 406 ---'ORANGE FENCING FOR 2� I 3 CB TYPE 1 (SOLID LID) INFILTRA IO A A RIM=408.59 Q.,?'-' E 18 EXISTI G " W.M. TO REUSE, 2" CONC W IE=403.30 26' F x DISCONNECT EXISTING 2" CONC IN IE=403.24 f WATE LINLL E & INSTAA TBR 3. W - "HOSE BIB WITH AN A' AT KISTING REMAIN w - x V x w w w x D- SDI SD- SD 10 MAIL OX S TYPE 1 =405.40 " CONC E IE=44.73 NC W IE�/402.67 <THE ETER m 0 FENCE £ j Ed3 \ x�x-x ww w-ww w w w w ww SD- SD- SD SD- SD- SD S KEEP FENCE IN PLACE W 1 DURING GRADING, 0 EXCAVATION AND BACKFILLCA O 1 N 1 - / nASHFD YELLOW I STRIPE 342.72' HOME TECH 13608 SE 51ST PL BELLEVUE, WA 206 778 2431 32229 'PA0/S'1'Cg ZONAL N 0 CIO Z Z � W Q J a LU :) Z N Q F- vp N H M C0 V o LLI 2 � REVISIONS DATE DESIGN: Y. S. DRAWING: H. H. CHECKI Y. S. DATE: SEPT 19, 2024 SCALE1 AS SHOWN SHEET; CV3o 1 2" x 2" FILTER FABRIC SECURED TO 2" X 2" 14 GA WIRE FABRIC EQUAL NATIVE BACKFILL FILTER FABRIC MATERIAL IN CONTNOUS ROLLS USE STAPLES OR WIRE RINGS TO ATTACH FABRIC TO WIRE 2" x 2" WOOD/STEEL POM5 BURY GO OM OF FILTER MATERIAL 8' TO 12" NOTES: SYMBOL: e G) e EF 1. CONTRACTOR/OEVELOPER SHALL MAINTAIN AND ENSURE PROPER EROSION CONTROL THROUGHOUT PROJECT. CITY INSPECTION REQUIRED ON 2. SILT FENCE TO BE PLACED DOWNSLOPE OF CONSTRUCTION ALL EROSION CONTROL METHODS ACTIVITY. BEFORE OTHER WORK CAN BEGIN FILTER FABRIC FENCE REVISION DATE JANUARY 2018 CITY OF EDMONDS FILTRATION SYSTEMS PUBLIC WORKS 0 STANDARD DEPARTMENT DETAIL APPROVED BY: R. ENGLISH ER-900 TESC GENERAL NOTES: 3 MIN RADIUS QUARRY SPALLS 2-4' MIN DIA 12' MIN DEPTH 15' MIN PROVIDE FULL WIDTH OF INGRESS/EGRESS SYMBOL: DETAIL NOTES: I GE O THE MINIMUM LENGTH SHALL BE EXTENDED AS NECESSARY TO ENSURE MATERIAL IS NOT TRACKED OFF SITE AND/OR INTO THE PUBLIC RIGHT-OF-WAY. 2O ATB DRIVEWAY RAMP AND/OR SITE ACCESS ROAD 15' WIDE MIN. SEE TABLE BELOW FOR REQUIRED LENGTH, NOTES: 1. SURFACE WATER - ALL SURFACE WATER ROWING OR DIVERTED TOWARD CONSTRUCTION ENTRANCES SHALL BE PIPED ACROSS THE ENTRANCE, IF PIPING IS IMPRACTICAL, A MOUNTABLE BERM WITH 5:1 SLOPES WILL BE PERMITTED. 2. MAINTENANCE - THE ENTRANCE SHALL BE MAINTAINED IN A CONDITION WHICH WILL PREVENT TRACKING OR FLOWING OF SEDIMENT OFF SITE AND/OR ONTO PUBUC RIGHT-OF-WAY. THIS MAY REQUIRE PERIODIC TOP DRESSING WITH ADDITIONAL QUARRY SPALLS AS CONDITIONS DEMAND AND REPAIR AND/OR CLFANOUT OF ANY MEASURES USED TO TRAP SEDIMENT. ALL SEDIMENT SPILLED, DROPPED, WASHED OR TRACKED OFF SITE AND/OR ONTO PUBUC RIGHT-OF-WAY MUST BE REMOVED IMMEDIATELY. 3. WHEELS SHALL BE CLEANED TO REMOVE SEDIMENT PRIOR TO LEAVING THE SITE. WHEN WASHING IS USED, IT SHALL BE DONE ON AN AREA STABILIZED WITH QUARRY SPALLS AND WHICH DRAINS INTO AN APPROVED SEDIMENT TRAPPING DEVICE. 4. INSPECTION AND NEEDED MAINTENANCE SHAM BE PROVIDED AFTER EACH RAIN. PROJECT SRE MIN LENGTH OF (FEET) QUARRY SPALLSF < 1/4 ACRE 30 < 1 ACRE 50 < 3 ACRE 100 > 3 ACRE 100 •PROVIDE ATB Oft ASPHALT TRANSITION WHERE FRONTAGE ROAD IS AN AN RIAL LENGTH TO BE DETERMINED BY CITY INSPECTOR. CITY INSPECTION REQUIRED ON ALL EROSION CONTROL METHODS BEFORE OTHER WORK CAN BEGIN REVISION DATE ffi CITY OF EDMONDS STABILIZED CONSTRUCTION JaNuaRY 20I8 ENTRANCE PUBLIC WORKS STANDARD DEPARTMENT DETAIL 11,,1g90 APPROVED BY: R. ENGMSH ER-901 1. From October 1 to April 30, no soil shall remain unstabilized for more than 2 days. From May 1 to September 30, no soils shall remain unstabilized for more than 7 days. Stabilize all soils, including stockpiles that are temporarily exposed. Use one of the following to temporarily stabilize soils, including stockpiles: E1.10 Temporary Seeding & Mulching, E1.15 Matting/Rolled Erosion Control Products, E1.20 Plastic Covering. 2. After construction but before project is considered completed, permanently stabilize all exposed soils that have been disturbed during construction. 3. Use ER-900 Filter fence to prevent the transport of sediment from the site. 4. Prevent sediment from entering all storm drains, including ditches that receive runoff from the disturbed area, by installing storm drain inlet inserts, using sandbags and vacuuming sediment from impervious surfaces. 5. Provide periodic street cleaning by sweeping or shoveling any sediment that may have been tracked out. Place sediment in a suitable disposal area where it will not erode again. ER-901 Construction Access. 6. Inspect and maintain required erosion controls to ensure continued performance of their intended function. 7. The contractor shall employ emergency measures to remove sediment from paved surfaces, as needed. Street sweeping shall be considered an emergency measure and not a basic component of the TESC system. No washing of streets under any conditions. 8. All disturbed areas to be compost amended per 2019 SWMMWW BMP T.5.13. 9. In future pervious pavement areas, if construction traffic can not feasibly avoid the area, over -excavate and obtain geotechnical approval of the sub -grade prior to placing rock for the pervious pavement section. 10. Install and maintain all TESC measures according to approved plans, City of Edmonds standard details, and all other measures that may be required during construction. SYMBOL: I / -CATCH BASIN � ` \ GRATE FILER SOCK WITH OVER FLOW HOLES (TYR) CATCH 61511 NOTES: 1. CONTRACTOR/DEVELOPER SHALL MAINTAIN TNIS APPLICATION AT ALL TIMES DURING CONSTRUCTION PERIOD. 2. ANY SEDIMENT IN CATCH BASIN INSERT SHALL BE REMOVED WHEN INSERT IS ONE-TNIRD FULL 3. CITY INSPECTION REWIRED ON ALL EROSION CONTROL METHODS BEFORE OTHER WORK CAN BEGIN, f TEMPORARY OF EDMONDS SEDIMENT TRAP PUBLIC WORKS FOR CATCH BASINS DEPARTMENT APPROVED B7: R. ENCASH REVISION DATE JANUARY 2018 STANDARD DETAIL ER-902 UNDISTURBED PLANTS UNDISTURBED TURF (LAWN) (SEE NOTE 1) AREAS (SEE NOTE 1) UNDISTURBED UNDISTURBED NATIVE VEGETATION 0" TURF/LAWN/LANDSCAPE UNDISTURBED NATIVE SOIL UNDISTURBED NATIVE SOIL STEEP SLOPE NOTE AMENDED SOILS SHOULD NOT BE OPTION 1 - NO DISTURBANCE INSTALLED ON FINISHED SLOPES EXCEEDING 33%. AREAS EXCEEDING 33% SHALL BE STABILIZED PER THE PLANTING BEDS TURF (LAWN) AREAS ENGINEER/GEOTECH OF RECORD. 2" ORGANIC MULCH 0" GRASS: SEED OR SOD F II -I I -I II - IILJ= I I I 1 3' OF COMPOST ➢II -I 1.75" OF COMPOST INCORPORATED INCORPORATED INTO 5" OF I �- SITE SOIL (TOTAL AMENDED m I INTO 6.25' OF SITE SOIL (TOTAL AMENDED DEPTH OF 9.5% FOR A DEPTH OF 9.5". FOR A SETTLED DEPTH OF B") SETTLED DEPTH OF 8") F] SUBSOIL SCARIFIED 4' BELOW 1' �_ _ SUBSOIL SCARIFIED 4' BELOW COMPOST AMENDED LAYER _ 1y�. ,: COMPOST AMENDED LAYER (12' BELOW SOIL SURFACE) _ I _^ at ' (12" BELOW SOIL SURFACE) 12" OPTION 2 - AMEND IN PLACE OR STOCKPILE AND AMEND GENERAL NOTES: PLANTING BEDS TURF (LAWN) AREAS 1. AREAS OF NO DISTURBANCE 2° ORGANIC �j��j%� SHALL BE FENCED AND EXISTING MULCH ��/��/��/� 0" _ SEED OR SOD S OIL SHALL BE PROTECTED FROM CONSTRUCTION -1 IMPACTS. 6" IMPORTED ICI - 6' IMPORTED 2. TO MEASURE SETTLED DEPTH, WATER SOIL SUFFICIENTLY TO TOPSOIL MIX (COMPACTED _ TOPSOIL MIX (COMPACTED FULLY SATURATE WITHOUT CAUSING EROSION. DEPTH) 6" - _ DEPTH) 3. COMPOST SHALL MEET SPEC. SUBSOIL IS -1. 31 41 SUBSOIL IS REQUIREMENTS IN THE 2017 ADDDEDENDUM (CNDU STORMWATER AHECKLIST 7), SCARIFIED 6" U- 1' L - ' SCARIFIED G" BELOW IMPORTED ,I ;p.... _ _ _ - - BELOW IMPORTED 4, COMPACTEN OF TOPSOIL (WHERE TOPSOIL MIX a ._ 12^ _ _. TOPSOIL MIX REQUIRED) TO BE TO 65% (MAX) OF THE MAXIMUM DRY DENSITY OPTION 3 - IMPORT TOPSOIL PER MODIFIED PROCTOR TEST POST CONSTRUCTION SOIL REVPRION2021E CITY OF EDMONDS QUALITY AND DEPTH STANDARD PUBLIC WORKS DEPARTMENT DETAIL ,OS SD-642 APPROVED BY: R. ENGLISH TEMPORARY SEEDING AND MULCHING E1.10 SEEDING MAY BE USED ONLY BETWEEN APRIL 1 AND JUNE 30, AND SEPTEMBER 1 AND OCTOBER 30. TRBEEis:i.�Ef§PAES?#ij%313J2•'sr?........:...........:::::::::::?::?::?:::::::::::::::::?::?::?:::::::::::::::?::?::?:::::::: ...................................................................................................................................................................... NAME PROPOR110NS BY WEIGHT % PURITY % GERMINATION REDTOP (AGROSTIS ALBA) 10% 92 90 ANNUAL RYE (LOLIUM MULTIFLORUM) 40% 98 90 CHENNGS FESCUE (FETUCA RUBRA COMMUTATA) 40% 97 80 WHITE DUTCH CLOVER (TRIFOLIUM PEPENS) 40% 96 90 REASON: TO PROVIDE TEMPORARY SOIL REMAIN BARE FOR MORE THAN S7ADAYS WHERE YPE PLANTNG MANENTGCOVER SIS NOT NECESSARY OR APPR AND LEGUMES TO AREAS THAT PRIATE.LDI SYMBOL: +__(Ts ► SO PLASTIC COVERING STOCKPILES E1.20 ANCHOR WEIGHTS WITH STAKES TRAW WATTLE / 10' MAX. IL BERM \\ TRAW BALES ONVEY RUNOFF TO APPROVED LOCATION. BURY SHEETING IN 4 IN. X 6 IN. TRENCH A MINIMUM OF 8 FT. SETBACK FROM TOP OF SLOPE. BACKFILL W)TH WASHED ROCK. PROVIDE ENERGY DISSIPATION AT TOE WHEN TOE IN SHEETING IN 4 IN. X 6 IN. TRENCH A MINIMUM OF 3 FT. SETBACK FROM BOTTOM OF SLOPE. BACKFILL WITH WASHED ROCK. CONVEY RUNOFF TO APPROVED LOCATION: CUT SLOPES ANCHOR WEIGHTS WITH STAKES CONVEY RUNOFF TO APPROVED LOCATION. 110' MAX. 3' MIN. REASON: DOPROM ISTU BEDEAR ASDIATE THAT CANNOTRBEEROSION COV RED BY MULCCHINGO &LOPES AND MATTING COVER SYMBOL: GPG MATTING/ROLLED EROSION CONTROL PRODUCTS El .15 BERM WHERE THERE IS A BERM AT THE TOP OF THE SLOPE, BRING THE NETTING OVER THE BERM AND ANCHOR IT BEHIND THE BERM REASON: TOHORTOVIDE IMMEDIIAT pELE ROTECPON TO EXPOSED SOILS DURING THE PERIOD OF SAYS SYMBOL: MD APPROVED FOR CONSTRUCTION CITY OF EDMONDS DATE: BY: CITY ENGINEERING DIVISION HOME TECH 13608 SE 51ST PL BELLEVUE, WA 206 778 2431 1�1G Sk /zs�?D2y F 32229 ,nq,�R,AQ/S'TCtit ZONAL W N CD CIO V/ 0 Z �O Q c r W W W N r Q O VT/ Z _ = F_ Z o A Vu� r N V � c� V o `W F- = REVISIONS DATE DESIGN: Y. S. DRAWING: H. H. CHECK: Y. S. DATE: JAN 25, 2024 SCALE: AS SHOWN SHEET: CVG2 Appendix C: SWPPP BMPs BMP C101: Preserving Natural Vegetation Purpose The purpose of preserving natural vegetation is to reduce erosion wherever practicable. Limiting site disturbance is the single most effective method for reducing erosion. For example, conifers can hold up to about 50 percent of all rain that falls during a storm. Up to 20-30 percent of this rain may never reach the ground but is taken up by the tree or evaporates. Another benefit is that the rain held in the tree can be released slowly to the ground after the storm. Conditions of Use Natural vegetation should be preserved on steep slopes, near perennial and intermittent watercourses or swales, and on building sites in wooded areas. . As required by local governments. . Phase construction to preserve natural vegetation on the project site for as long as possible during the construction period. Design and Installation Specifications Natural vegetation can be preserved in natural clumps or as individual trees, shrubs and vines. The preservation of individual plants is more difficult because heavy equipment is gen- erally used to remove unwanted vegetation. The points to remember when attempting to save individual plants are: Is the plant worth saving? Consider the location, species, size, age, vigor, and the work involved. Local governments may also have ordinances to save natural veget- ation and trees. Fence or clearly mark areas around trees that are to be saved. It is preferable to keep ground disturbance away from the trees at least as far out as the dripline. Plants need protection from three kinds of injuries: Construction Equipment- This injury can be above or below the ground level. Damage results from scarring, cutting of roots, and compaction of the soil. Placing a fenced buffer zone around plants to be saved prior to construction can prevent construction equipment injuries. Grade Changes - Changing the natural ground level will alter grades, which affects the plant's ability to obtain the necessary air, water, and minerals. Minor fills usu- ally do not cause problems although sensitivity between species does vary and should be checked. Trees can typically tolerate fill of 6 inches or less. For shrubs 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter 4 - Page 266 and other plants, the fill should be less. When there are major changes in grade, it may become necessary to supply air to the roots of plants. This can be done by placing a layer of gravel and a tile system over the roots before the fill is made. A tile system protects a tree from a raised grade. The tile system should be laid out on the original grade leading from a dry well around the tree trunk. The system should then be covered with small stones to allow air to circulate over the root area. Lowering the natural ground level can seriously damage trees and shrubs. The highest percentage of the plant roots are in the upper 12 inches of the soil and cuts of only 2-3 inches can cause serious injury. To protect the roots it may be neces- sary to terrace the immediate area around the plants to be saved. If roots are exposed, construction of retaining walls may be needed to keep the soil in place. Plants can also be preserved by leaving them on an undisturbed, gently sloping mound. To increase the chances for survival, it is best to limit grade changes and other soil disturbances to areas outside the dripline of the plant. Excavations - Protect trees and other plants when excavating for drainfields, power, water, and sewer lines. Where possible, the trenches should be routed around trees and large shrubs. When this is not possible, it is best to tunnel under them. This can be done with hand tools or with power augers. If it is not possible to route the trench around plants to be saved, then the following should be observed: Cut as few roots as possible. When you have to cut, cut clean. Paint cut root ends with a wood dressing like asphalt base paint if roots will be exposed for more than 24-hours. Backfill the trench as soon as possible. Tunnel beneath root systems as close to the center of the main trunk to pre- serve most of the important feeder roots. Some problems that can be encountered with a few specific trees are: . Maple, Dogwood, Red alder, Western hemlock, Western red cedar, and Douglas fir do not readily adjust to changes in environment and special care should be taken to protect these trees. . The windthrow hazard of Pacific silver fir and madrona is high, while that of Western hemlock is moderate. The danger of windthrow increases where dense stands have been thinned. Other species (unless they are on shallow, wet soils less than 20 inches deep) have a low windthrow hazard. Cottonwoods, maples, and willows have water -seeking roots. These can cause trouble in sewer lines and infiltration fields. On the other hand, they thrive in high moisture conditions that other trees would not. . Thinning operations in pure or mixed stands of Grand fir, Pacific silver fir, Noble fir, 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter 4 - Page 267 Sitka spruce, Western red cedar, Western hemlock, Pacific dogwood, and Red alder can cause serious disease problems. Disease can become established through damaged limbs, trunks, roots, and freshly cut stumps. Diseased and weakened trees are also susceptible to insect attack. Maintenance Standards Inspect flagged and/or fenced areas regularly to make sure flagging or fencing has not been removed or damaged. If the flagging or fencing has been damaged or visibility reduced, it shall be repaired or replaced immediately and visibility restored. . If tree roots have been exposed or injured, "prune" cleanly with an appropriate prun- ing saw or Toppers directly above the damaged roots and recover with native soils. Treatment of sap flowing trees (fir, hemlock, pine, soft maples) is not advised as sap forms a natural healing barrier. BMP C102: Buffer Zones Purpose Creation of an undisturbed area or strip of natural vegetation or an established suitable planting that will provide a living filter to reduce soil erosion and runoff veIocities. Conditions of Use Natural buffer zones are used along streams, wetlands and other bodies of water that need protection from erosion and sedimentation. Vegetative buffer zones can be used to protect natural swales and can be incorporated into the natural landscaping of an area. Critical -areas buffer zones should not be used as sediment treatment areas. These areas shall remain completely undisturbed. The local permitting authority may expand the buffer widths temporarily to allow the use of the expanded area for removal of sed- iment. Design and Installation Specifications • Preserving natural vegetation or plantings in clumps, blocks, or strips is generally the easiest and most successful method. • Leave all unstable steep slopes in natural vegetation. • Mark clearing limits and keep all equipment and construction debris out of the nat- ural areas and buffer zones. Steel construction fencing is the most effective method in protecting sensitive areas and buffers. Alternatively, wire -backed silt fence on steel posts is marginally effective. Flagging alone is typically not effective. . Keep all excavations outside the dripline of trees and shrubs. . Do not push debris or extra soil into the buffer zone area because it will cause 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter 4 - Page 268 Metal fences shall be designed and installed according to the manufacturer's spe- cifications. Metal fences shall be at least 3 feet high and must be highly visible. Fences shall not be wired or stapled to trees. Maintenance Standards If the fence has been damaged or visibility reduced, it shall be repaired or replaced immediately and visibility restored. BMP C105: Stabilized Construction Entrance / Exit Purpose Stabilized Construction entrances are established to reduce the amount of sediment transported onto paved roads by vehicles or equipment. This is done by constructing a stabilized pad of quarry spalls at entrances and exits for construction sites. Conditions of Use Construction entrances shall be stabilized wherever traffic will be entering or leaving a construction site if paved roads or other paved areas are within 1,000 feet of the site. For residential construction provide stabilized construction entrances for each residence, rather than only at the main subdivision entrance. Stabilized surfaces shall be of suf- ficient length/width to provide vehicle access/parking, based on lot size/configuration. On large commercial, highway, and road projects, the designer should include enough extra materials in the contract to allow for additional stabilized entrances not shown in the initial Construction SWPPP. It is difficult to determine exactly where access to these projects will take place; additional materials will enable the contractor to install them where needed. Design and Installation Specifications See Figure II-4.1.1 Stabilized Construction Entrance (p.273) for details. Note: the 100' minimum length of the entrance shall be reduced to the maximum practicable size when the size or configuration of the site does not allow the full length (100'). Construct stabilized construction entrances with a 12-inch thick pad of 4-inch to 8-inch quarry spalls, a 4-inch course of asphalt treated base (ATB), or use existing pavement. Do not use crushed concrete, cement, or calcium chloride for construction entrance sta- bilization because these products raise pH levels in stormwater and concrete discharge to surface waters of the State is prohibited. 2014 Stormwater Management Manual for Western Washington Volume 11- Chapter 4 - Page 270 A separation geotextile shall be placed under the spalls to prevent fine sediment from pumping up into the rock pad. The geotextile shall meet the following standards: Grab Tensile Strength (ASTM D4751) 200 psi min. Grab Tensile Elongation (ASTM D4632) 30% max. Mullen Burst Strength (ASTM D3786-80a)400 psi min. AOS (ASTM D4751) 20-45 (U.S. standard sieve size) Consider early installation of the first lift of asphalt in areas that will paved; this can be used as a stabilized entrance. Also consider the installation of excess concrete as a stabilized entrance. During large concrete pours, excess concrete is often available for this purpose. Fencing (see BMP C103: High Visibility Fence (p.269)) shall be installed as neces- sary to restrict traffic to the construction entrance. . Whenever possible, the entrance shall be constructed on a firm, compacted sub - grade. This can substantially increase the effectiveness of the pad and reduce the need for maintenance. . Construction entrances should avoid crossing existing sidewalks and back of walk drains if at all possible. If a construction entrance must cross a sidewalk or back of walk drain, the full length of the sidewalk and back of walk drain must be covered and protected from sediment leaving the site. Maintenance Standards Quarry spalls shall be added if the pad is no longer in accordance with the spe- cifications. If the entrance is not preventing sediment from being tracked onto pavement, then alternative measures to keep the streets free of sediment shall be used. This may include replacement/cleaning of the existing quarry spalls, street sweeping, an increase in the dimensions of the entrance, or the installation of a wheel wash. Any sediment that is tracked onto pavement shall be removed by shoveling or street sweeping. The sediment collected by sweeping shall be removed or sta- bilized on site. The pavement shall not be cleaned by washing down the street, except when high efficiency sweeping is ineffective and there is a threat to public safety. If it is necessary to wash the streets, the construction of a small sump to con- tain the wash water shall be considered. The sediment would then be washed into the sump where it can be controlled. Perform street sweeping by hand orwith a high efficiency sweeper. Do not use a non -high efficiency mechanical sweeper because this creates dust and throws soils into storm systems or conveyance ditches. 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter 4 - Page 271 Any quarry spalls that are loosened from the pad, which end up on the roadway shall be removed immediately. If vehicles are entering or exiting the site at points other than the construction entrance(s), fencing (see BMP C103) shall be installed to control traffic. Upon project completion and site stabilization, all construction accesses intended as permanent access for maintenance shall be permanently stabilized. 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter 4 - Page 272 cu roadsi Notes 1. 2. Figure II-4.1.1 Stabilized Construction Entrance the requirements of the permitting agency. It is recommended that the entrance be crowned so that runoff drains off the pad. ahft� DEPARTMENT OF ECOLOGY State of Washington NOT TO SCALE n. Provide full width of ingress/egress area Figure II-4.1.1 Stabilized Construction Entrance Revised June 2015 Please see http.//www.ecy.wa.gov/copyright.html for copyright notice including permissions, limitation of liability, and disclaimer. 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter 4 - Page 273 Approved as Equivalent Ecology has approved products as able to meet the requirements of BMP C105: Stab- ilized Construction Entrance / Exit. The products did not pass through the Technology Assessment Protocol — Ecology (TAPE) process. Local jurisdictions may choose not to accept this product approved as equivalent, or may require additional testing prior to con- sideration for local use. The products are available for review on Ecology's website at http://www.ecy.wa.gov/programs/wq/stormwater/newtech/equivalent.html BMP C106: Wheel Wash Purpose Wheel washes reduce the amount of sediment transported onto paved roads by motor vehicles. Conditions of Use When a stabilized construction entrance (see BMP C105: Stabilized Construction Entrance / Exit (p.270)) is not preventing sediment from being tracked onto pavement. . Wheel washing is generally an effective BMP when installed with careful attention to topography. For example, a wheel wash can be detrimental if installed at the top of a slope abutting a right-of-way where the water from the dripping truck can run unimpeded into the street. • Pressure washing combined with an adequately sized and surfaced pad with dir- ect drainage to a large 10-foot x 10-foot sump can be very effective. • Discharge wheel wash or tire bath wastewater to a separate on -site treatment sys- tem that prevents discharge to surface water, such as closed -loop recirculation or upland land application, or to the sanitary sewer with local sewer district approval. . Wheel wash or tire bath wastewater should not include wastewater from concrete washout areas. Design and Installation Specifications Suggested details are shown in Figure II-4.1.2 Wheel Wash (p.276). The Local Per- mitting Authority may allow other designs. A minimum of 6 inches of asphalt treated base (ATB) over crushed base material or 8 inches over a good subgrade is recommended to pave the wheel wash. Use a low clearance truck to test the wheel wash before paving. Either a belly dump or lowboy will work well to test clearance. Keep the water level from 12 to 14 inches deep to avoid damage to truck hubs and filling the truck tongues with water. 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter 4 - Page 274 Storm drain inlets shall be protected to prevent sediment -laden water entering the storm drain system (see BMP C220: Storm Drain Inlet Protection (p.357)). Maintenance Standards Inspect stabilized areas regularly, especially after large storm events. Crushed rock, gravel base, etc., shall be added as required to maintain a stable driving surface and to stabilize any areas that have eroded. Following construction, these areas shall be restored to pre -construction condition or bet- ter to prevent future erosion. Perform street cleaning at the end of each day or more often if necessary. BMP C120: Temporary and Permanent Seeding Purpose Seeding reduces erosion by stabilizing exposed soils. A well -established vegetative cover is one of the most effective methods of reducing erosion. Conditions of Use Use seeding throughout the project on disturbed areas that have reached final grade or that will remain unworked for more than 30 days. The optimum seeding windows for western Washington are April 1 through June 30 and September 1 through October 1. Between July 1 and August 30 seeding requires irrigation until 75 percent grass cover is established. Between October 1 and March 30 seeding requires a cover of mulch with straw or an erosion control blanket until 75 percent grass cover is established. Review all disturbed areas in late August to early September and complete all seeding by the end of September. Otherwise, vegetation will not establish itself enough to provide more than average protection. . Mulch is required at all times for seeding because it protects seeds from heat, mois- ture loss, and transport due to runoff. Mulch can be applied on top of the seed or simultaneously by hydroseeding. See BMP C121: Mulching (p.284) for spe- cifications. . Seed and mulch, all disturbed areas not otherwise vegetated at final site sta- bilization. Final stabilization means the completion of all soil disturbing activities at the site and the establishment of a permanent vegetative cover, or equivalent per- 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter 4 - Page 278 manent stabilization measures (such as pavement, riprap, gabions, or geotextiles) which will prevent erosion. Design and Installation Specifications Seed retention/detention ponds as required. Install channels intended for vegetation before starting major earthwork and hydroseed with a Bonded Fiber Matrix. For vegetated channels that will have high flows, install erosion control blankets over hydroseed. Before allowing water to flow in vegetated channels, establish 75 percent vegetation cover. If vegetated channels cannot be estab- lished by seed before water flow; install sod in the channel bottom —over hydromulch and erosion control blankets. . Confirm the installation of all required surface water control measures to prevent seed from washing away. . Hydroseed applications shall include a minimum of 1,500 pounds per acre of mulch with 3 percent tackifier. See BMP C121: Mulching .284 for specifications. . Areas that will have seeding only and not landscaping may need compost or meal - based mulch included in the hydroseed in order to establish vegetation. Re -install native topsoil on the disturbed soil surface before application. . When installing seed via hydroseeding operations, only about 1/3 of the seed actu- ally ends up in contact with the soil surface. This reduces the ability to establish a good stand of grass quickly. To overcome this, consider increasing seed quantities by up to 50 percent. . Enhance vegetation establishment by dividing the hydromulch operation into two phases: 1. Phase 1- Install all seed and fertilizer with 25-30 percent mulch and tackifier onto soil in the first lift. 2. Phase 2- Install the rest of the mulch and tackifier over the first lift. Or, enhance vegetation by: 1. Installing the mulch, seed, fertilizer, and tackifier in one lift. 2. Spread or blow straw over the top of the hydromulch at a rate of 800-1000 pounds per acre. 3. Hold straw in place with a standard tackifier. Both of these approaches will increase cost moderately but will greatly improve and enhance vegetative establishment. The increased cost may be offset by the reduced need for: 2014 Stormwater Management Manual for Western Washington Volume ll - Chapter 4 - Page 279 . Irrigation. . Reapplication of mulch. . Repair of failed slope surfaces. This technique works with standard hydromulch (1,500 pounds per acre minimum) and BFM/MBFMs (3,000 pounds per acre minimum). Seed may be installed by hand if: . Temporary and covered by straw, mulch, or topsoil. Permanent in small areas (usually less than 1 acre) and covered with mulch, topsoil, or erosion blankets. . The seed mixes listed in the tables below include recommended mixes for both temporary and permanent seeding. . Apply these mixes, with the exception of the wetland mix, at a rate of 120 pounds per acre. This rate can be reduced if soil amendments or slow - release fertilizers are used. Consult the local suppliers or the local conservation district for their recom- mendations because the appropriate mix depends on a variety of factors, including location, exposure, soil type, slope, and expected foot traffic. Altern- ative seed mixes approved by the local authority may be used. Other mixes may be appropriate, depending on the soil type and hydrology of the area. . Table II-4.1.2 Temporary Erosion Control Seed Mix (p.280) lists the standard mix for areas requiring a temporary vegetative cover. Table II-4.1.2 Temporary Erosion Control Seed Mix % Weight % Purity % Germination Chewings or annual blue grass 40 98 90 Festuca rubra var. commutate or Poa anna Perennial rye 50 98 90 Lolium perenne Redtop or colonial bentgrass 5 92 85 Agrostis alba or Agrostis tenuis White dutch clover 5 98 90 Trifolium repens . Table II-4.1.3 Landscaping Seed Mix (p.281) lists a recommended mix for land- scaping seed. 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter 4 - Page 280 Table II-4.1.3 Landscaping Seed Mix % Weight % Purity % Germination Perennial rye blend 70 98 90 Lolium perenne Chewings and red fescue blend 30 98 90 Festuca rubra var. commutate or Festuca rubra Table II-4.1.4 Low -Growing Turf Seed Mix (p.281) lists a turf seed mix for dry situ- ations where there is no need for watering. This mix requires very little main- tenance. Table II-4.1.4 Low -Growing Turf Seed Mix % Weight % Purity % Germination Dwarf tall fescue (several varieties) 45 98 90 Festuca arundinacea var. Dwarf perennial rye (Barclay) 30 98 90 Lolium perenne var. barclay Red fescue 20 98 90 Festuca rubra Colonial bentgrass 5 98 90 Agrostis tenuis . Table II-4.1.5 Bioswale Seed Mix* (p.281) lists a mix for bioswales and other inter- mittently wet areas. Table II-4.1.5 Bioswale Seed Mix* % Weight % Purity % Germination Tall or meadow fescue Festuca arundinacea or Festuca ela- 75-80 98 90 tior Seaside/Creeping bentgrass 10-15 92 85 Agrostis palustris Redtop bentgrass 5-10 90 80 Agrostis alba or Agrostis gigantea * Modified Briargreen, Inc. Hydroseeding Guide Wetlands Seed Mix . Table II-4.1.6 Wet Area Seed Mix* (p.282) lists a low -growing, relatively non-invas- ive seed mix appropriate for very wet areas that are not regulated wetlands. Apply 2014 Stormwater Management Manual for Western Washington Volume II - Chapter 4 - Page 281 this mixture at a rate of 60 pounds per acre. Consult Hydraulic Permit Authority (HPA) for seed mixes if applicable. Table II-4.1.6 Wet Area Seed Mix* % Weight % Purity % Germination Tall or meadow fescue Festuca arundinacea or Festuca ela- 60-70 98 90 tior Seaside/Creeping bentgrass 10-15 98 85 Agrostis palustris Meadow foxtaiI 10-15 90 80 Alepocurus prateneis Alsike clover 1-6 98 90 Trifolium hybridum Redtop bentgrass 1-6 92 85 Agrostis alba * Modified Briargreen, Inc. Hydroseeding Guide Wetlands Seed Mix Table II-4.1.7 Meadow Seed Mix (p.282) lists a recommended meadow seed mix for infrequently maintained areas or non -maintained areas where colonization by native plants is desirable. Likely applications include rural road and utility right-of- way. Seeding should take place in September or very early October in order to obtain adequate establishment prior to the winter months. Consider the appro- priateness of clover, a fairly invasive species, in the mix. Amending the soil can reduce the need for clover. Table II-4.1.7 Meadow Seed Mix % Weight % Purity % Germination Redtop or Oregon bentgrass 20 92 85 Agrostis alba or Agrostis oregonensis Red fescue 70 98 90 Festuca rubra White dutch clover 10 98 90 Trifolium repens . Roughening and Rototilling: The seedbed should be firm and rough. Roughen all soil no matter what the slope. Track walk slopes before seeding if engineering purposes require 2014 Stormwater Management Manual for Western Washington Volume II - Chapter 4 - Page 282 compaction. Backblading or smoothing of slopes greater than 4H:1 V is not allowed if they are to be seeded. . Restoration -based landscape practices require deeper incorporation than that provided by a simple single -pass rototilling treatment. Wherever prac- tical, initially rip the subgrade to improve long-term permeability, infiltration, and water inflow qualities. At a minimum, permanent areas shall use soil amendments to achieve organic matter and permeability performance defined in engineered soil/landscape systems. For systems that are deeper than 8 inches complete the rototilling process in multiple lifts, or prepare the engineered soil system per specifications and place to achieve the specified depth. . Fertilizers: . Conducting soil tests to determine the exact type and quantity of fertilizer is recommended. This will prevent the over -application of fertilizer. . Organic matter is the most appropriate form of fertilizer because it provides nutrients (including nitrogen, phosphorus, and potassium) in the least water- soluble form. . In general, use 10-4-6 N-P-K (nitrogen -phosphorus -potassium) fertilizer at a rate of 90 pounds per acre. Always use slow -release fertilizers because they are more efficient and have fewer environmental impacts. Do not add fer- tilizer to the hydromulch machine, or agitate, more than 20 minutes before use. Too much agitation destroys the slow -release coating. . There are numerous products available that take the place of chemical fer- tilizers. These include several with seaweed extracts that are beneficial to soil microbes and organisms. If 100 percent cottonseed meal is used as the mulch in hydroseed, chemical fertilizer may not be necessary. Cottonseed meal provides a good source of long-term, slow -release, available nitrogen. . Bonded Fiber Matrix and Mechanically Bonded Fiber Matrix: On steep slopes use Bonded Fiber Matrix (BFM) or Mechanically Bonded Fiber Matrix (MBFM) products. Apply BFM/MBFM products at a minimum rate of 3,000 pounds per acre of mulch with approximately 10 percent tackifier. Achieve a minimum of 95 percent soil coverage during application. Numer- ous products are available commercially. Installed products per man- ufacturer's instructions. Most products require 24-36 hours to cure before rainfall and cannot be installed on wet or saturated soils. Generally, products come in 40-50 pound bags and include all necessary ingredients except for seed and fertilizer. 2014 Stormwater Management Manual for Western Washington Volume ll - Chapter 4 - Page 283 BFMs and MBFMs provide good alternatives to blankets in most areas requir- ing vegetation establishment. Advantages over blankets include: • BFM and MBFMs do not require surface preparation. . Helicopters can assist in installing BFM and MBFMs in remote areas. . On slopes steeper than 2.5H:1 V, blanket installers may require ropes and harnesses for safety. . Installing BFM and MBFMs can save at least $1,000 per acre com- pared to blankets. Maintenance Standards Reseed any seeded areas that fail to establish at least 80 percent cover (100 percent cover for areas that receive sheet or concentrated flows). If reseeding is ineffective, use an alternate method such as sodding, mulching, or nets/blankets. If winter weather pre- vents adequate grass growth, this time limit may be relaxed at the discretion of the local authority when sensitive areas would otherwise be protected. • Reseed and protect by mulch any areas that experience erosion after achieving adequate cover. Reseed and protect by mulch any eroded area. . Supply seeded areas with adequate moisture, but do not water to the extent that it causes runoff. Approved as Equivalent Ecology has approved products as able to meet the requirements of BMP C120: Tem- op rary and Permanent Seeding. The products did not pass through the Technology Assessment Protocol — Ecology (TAPE) process. Local jurisdictions may choose not to accept this product approved as equivalent, or may require additional testing prior to con- sideration for local use. The products are available for review on Ecology's website at http://www.ecy.wa.gov/programs/wq/stormwater/newtech/equivalent.html. BMP C121: Mulching Purpose Mulching soils provides immediate temporary protection from erosion. Mulch also enhances plant establishment by conserving moisture, holding fertilizer, seed, and top- soil in place, and moderating soil temperatures. There is an enormous variety of mulches that can be used. This section discusses only the most common types of mulch. Conditions of Use As a temporary cover measure, mulch should be used: 2014 Stormwater Management Manual for Western Washington Volume ll - Chapter 4 - Page 284 . For less than 30 days on disturbed areas that require cover. . At all times for seeded areas, especially during the wet season and during the hot summer months. . During the wet season on slopes steeper than 3H:1 V with more than 10 feet of ver- tical relief. Mulch may be applied at any time of the year and must be refreshed periodically. For seeded areas mulch may be made up of 100 percent: cottonseed meal; fibers made of wood, recycled cellulose, hemp, kenaf; compost; or blends of these. Tack- ifier shall be plant -based, such as guar or alpha plantago, or chemical -based such as polyacrylamide or polymers. Any mulch or tackifier product used shall be installed per manufacturer's instructions. Generally, mulches come in 40-50 pound bags. Seed and fertilizer are added at time of application. Design and Installation Specifications For mulch materials, application rates, and specifications, see Table II-4.1.8 Mulch Standards and Guidelines (p.286). Always use a 2-inch minimum mulch thickness; increase the thickness until the ground is 95% covered (i.e. not visible under the mulch layer). Note: Thickness may be increased for disturbed areas in or near sensitive areas or other areas highly susceptible to erosion. Where the option of "Compost" is selected, it should be a coarse compost that meets the following size gradations when tested in accordance with the U.S. Composting Council "Test Methods for the Examination of Compost and Composting" (TMECC) Test Method 02.02-B. Coarse Compost Minimum Percent passing 3" sieve openings 100% Minimum Percent passing 1"sieve openings 90% Minimum Percent passing 1/4" sieve openings 70% Minimum Percent passing'/4" sieve openings 40% Mulch used within the ordinary high-water mark of surface waters should be selected to minimize potential flotation of organic matter. Composted organic materials have higher specific gravities (densities) than straw, wood, or chipped material. Consult Hydraulic Permit Authority (HPA) for mulch mixes if applicable. Maintenance Standards . The thickness of the cover must be maintained. . Any areas that experience erosion shall be remulched and/or protected with a net 2014 Stormwater Management Manual for Western Washington Volume 11- Chapter 4 - Page 285 or blanket. If the erosion problem is drainage related, then the problem shall be fixed and the eroded area remulched. Table 11-4.1.8 Mulch Standards and Guidelines Mulch Quality Application Remarks Material Standards Rates Cost-effective protection when applied with adequate thickness. Hand -application generally requires greater thickness than blown straw. The thickness of straw may be reduced by half when used in conjunction with seeding. In windy areas Air-dried; 2„ 3„ thick; straw must be held in place by crimping, using a free from 5 bales per tackifier, or covering with netting. Blown straw Straw undesirable sf orns 1-3 always has to be held in place with a tackifier as seed and toper to even light winds will blow it away. Straw, how - coarse ever, has several deficiencies that should be con - material. acre acre sidered when selecting mulch materials. It often introduces and/or encourages the propagation of weed species and it has no significant long-term benefits It should also not be used within the ordinary high-water elevation of surface waters (due to flotation). Approx. 25- Shall be applied with hydromulcher. Shall not be No growth 30 Ibs per used without seed and tackifier unless the applic- Hydromulch inhibiting 1,000 sf or 1,500 - ation rate is at least doubled. Fibers longer than factors. 2,000 Ibs about 3/4 - 1 inch clog hydromulch equipment. Fibers should be kept to less than 3/4 inch. per acre No visible water or More effective control can be obtained by increas- dust during ing thickness to 3". Excellent mulch for protecting handling. 2" thick final grades until landscaping because it can be Must be pro min.; directly seeded or tilled into soil as an amend- duced per approx. 100 ment. Compost used for mulch has a coarser size Compost WAC 173- tons per gradation than compost used for BMP C125: Top- 350, Solid acre soiling / Composting (p.297) or BMP T5.13: Post - Waste (approx. Construction Soil Quality and Depth (p.911). It is more stable and practical to use in wet areas and Handling 800 Ibs per Standards, yard) during rainy weather conditions. Do not use near but may wetlands or near phosphorous impaired water have up to bodies. 35% 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter 4 - Page 286 Table II-4.1.8 Mulch Standards and Guidelines (continued) Mulch Quality Application Remarks Material Standards Rates biosolids. Average size shall This is a cost-effective way to dispose of debris be several from clearing and grubbing, and it eliminates the inches. problems associated with burning. Generally, it Chipped Gradations should not be used on slopes above approx. 10% Site Veget- from fines 2" thick because of its tendency to be transported by run- ation to 6 inches min.; off. It is not recommended within 200 feet of sur- in length for face waters. If seeding is expected shortly after texture, vari mulch, the decomposition of the chipped veget- ation, and ation may tie up nutrients important to grass estab interlocking lishment. properties. No visible water or dust during handling. This material is often called "hog or hogged fuel". Must be pur 2" thick The use of mulch ultimately improves the organic Wood- chased min.; matter in the soil. Special caution is advised based from a sup- approx. 100 regarding the source and composition of wood - Mulch or plierwith a tons per based mulches. Its preparation typically does not Wood SoliWasdte acre provide any weed seed control, so evidence of Straw (ap x. residual vegetation in its composition or known Handling lbs. per inclusion of weed plants or seeds should be mon- Permit or cubic yard) itored and prevented (or minimized). one exempt from solid waste reg- ulations. A blend of Cost-effective protection when applied with loose, long, adequate thickness. A minimum of 95-percent of thin wood the wood strand shall have lengths between 2 Wood pieces and 10-inches, with a width and thickness Strand derived 2" thick min. between 1/16 and 3/8-inches. The mulch shall not Mulch from native contain resin, tannin, or other compounds in conifer or quantities that would be detrimental to plant life. deciduous Sawdust or wood shavings shall not be used as trees with mulch. (WSDOT specification (9-14.4(4)) 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter 4 - Page 287 Table II-4.1.8 Mulch Standards and Guidelines (continued) Mulch Quality Application Remarks Material Standards Rates high length - to -width ratio. BMP C122: Nets and Blankets Purpose Erosion control nets and blankets are intended to prevent erosion and hold seed and mulch in place on steep slopes and in channels so that vegetation can become well established. In addition, some nets and blankets can be used to permanently reinforce turf to protect drainage ways during high flows. Nets (commonly called matting) are strands of material woven into an open, but high -tensile strength net (for example, coconut fiber matting). Blankets are strands of material that are not tightly woven, but instead form a layer of interlocking fibers, typically held together by a biodegradable or photodegradable netting (for example, excelsior or straw blankets). They generally have lower tensile strength than nets, but cover the ground more completely. Coir (coconut fiber) fabric comes as both nets and blankets. Conditions of Use Erosion control nets and blankets should be used: . To aid permanent vegetated stabilization of slopes 2H:1 V or greater and with more than 10 feet of vertical relief. For drainage ditches and swales (highly recommended). The application of appro- priate netting or blanket to drainage ditches and swales can protect bare soil from channelized runoff while vegetation is established. Nets and blankets also can cap- ture a great deal of sediment due to their open, porous structure. Nets and blankets can be used to permanently stabilize channels and may provide a cost-effective, environmentally preferable alternative to riprap. 100 percent synthetic blankets manufactured for use in ditches may be easily reused as temporary ditch liners. Disadvantages of blankets include- - Surface preparation required. . On slopes steeper than 2.5H:1 V, blanket installers may need to be roped and har- nessed for safety. . They cost at least $4,000-6,000 per acre installed. Advantages of blankets include: 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter 4 - Page 288 . Installation without mobilizing special equipment. . Installation by anyone with minimal training . Installation in stages or phases as the project progresses. . Installers can hand place seed and fertilizer as they progress down the slope. . Installation in any weather. . There are numerous types of blankets that can be designed with various para- meters in mind. Those parameters include: fiber blend, mesh strength, longevity, biodegradability, cost, and availability. Design and Installation Specifications See Figure II-4.1.3 Channel Installation (p.292) and Figure II-4.1.4 Slope Install- ation (p.293) for typical orientation and installation of blankets used in channels and as slope protection. Note: these are typical only; all blankets must be installed per manufacturer's installation instructions. Installation is critical to the effectiveness of these products. If good ground contact is not achieved, runoff can concentrate under the product, resulting in significant erosion. . Installation of Blankets on Slopes: 1. Complete final grade and track walk up and down the slope. 2. Install hydromulch with seed and fertilizer. 3. Dig a small trench, approximately 12 inches wide by 6 inches deep along the top of the slope. 4. Install the leading edge of the blanket into the small trench and staple approx- imately every 18 inches. NOTE: Staples are metal, "U"-shaped, and a min- imum of 6 inches long. Longer staples are used in sandy soils. Biodegradable stakes are also available. 5. Roll the blanket slowly down the slope as installer walks backwards. NOTE: The blanket rests against the installer's legs. Staples are installed as the blanket is unrolled. It is critical that the proper staple pattern is used for the blanket being installed. The blanket is not to be allowed to roll down the slope on its own as this stretches the blanket making it impossible to main- tain soil contact. In addition, no one is allowed to walk on the blanket after it is in place. 6. If the blanket is not long enough to cover the entire slope length, the trailing edge of the upper blanket should overlap the leading edge of the lower 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter 4 - Page 289 blanket and be stapled. On steeper slopes, this overlap should be installed in a small trench, stapled, and covered with soil. With the variety of products available, it is impossible to cover all the details of appropriate use and installation. Therefore, it is critical that the design engineer consult the manufacturer's information and that a site visit takes place in order to ensure that the product specified is appropriate. Information is also available at the following web sites: 1. WSDOT (Section 3.2.4): ://www.wsdot.wa.aov/NR/rdonlvres/3B41 E087-FA86-4717-932D- D7A8556CCD57/0/ErosionTraininaManual.Ddf 2. Texas Transportation Institute: http://www.txdot.gov/business/doing_business/product_evaluation/erosion_ control.htm • Use jute matting in conjunction with mulch (BMP C121: Mulching (p.284)). Excel- sior, woven straw blankets and coir (coconut fiber) blankets may be installed without mulch. There are many other types of erosion control nets and blankets on the market that may be appropriate in certain circumstances. . In general, most nets (e.g., jute matting) require mulch in order to prevent erosion because they have a fairly open structure. Blankets typically do not require mulch because they usually provide complete protection of the surface. . Extremely steep, unstable, wet, or rocky slopes are often appropriate candidates for use of synthetic blankets, as are riverbanks, beaches and other high-energy environments. If synthetic blankets are used, the soil should be hydromulched first. . 100-percent biodegradable blankets are available for use in sensitive areas. These organic blankets are usually held together with a paper or fiber mesh and stitching which may last up to a year. . Most netting used with blankets is photodegradable, meaning they break down under sunlight (not UV stabilized). However, this process can take months or years even under bright sun. Once vegetation is established, sunlight does not reach the mesh. It is not uncommon to find non -degraded netting still in place several years after installation. This can be a problem if maintenance requires the use of mowers or ditch cleaning equipment. In addition, birds and small animals can become trapped in the netting. Maintenance Standards . Maintain good contact with the ground. Erosion must not occur beneath the net or blanket. 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter 4 - Page 290 . Repair and staple any areas of the net or blanket that are damaged or not inclose contact with the ground. . Fix and protect eroded areas if erosion occurs due to poorly controlled drainage. 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter 4 - Page 291 5/29/24, 6:38 AM BMP C207: Check Dams You are here: 2019 SWMMWW > Volume 11 - Construction Stormwater Pollution Prevention > 11-3 Construction Stormwater BMPs > BMP C207: Check Dams BMP C207: Check Dams Purpose Construction of check dams across a swale or ditch reduces the velocity of concentrated flow and dissipates energy at the check dam. Conditions of Use Use check dams where temporary or permanent channels are not yet vegetated, channel lining is infeasible, and/or velocity checks are required. • Check dams may not be placed in streams unless approved by the State Department of Fish and Wildlife. • Check dams may not be placed in wetlands without approval from a permitting agency. • Do not place check dams below the expected backwater from any salmonid bearing water between October 1 and May 31 to ensure that there is no loss of high flow refuge habitat for overwintering juvenile salmonids and emergent salmonid fry. Design and Installation Specifications • Construct rock check dams from appropriately sized rock. The rock used must be large enough to stay in place given the expected design flow through the channel. The rock must be placed by hand or by mechanical means (do not dump the rock to form the dam) to achieve complete coverage of the ditch or swale and to ensure that the center of the dam is lower than the edges. • Check dams may also be constructed of either rock or pea -gravel filled bags. Numerous new products are also available for this purpose. They tend to be re -usable, quick and easy to install, effective, and cost efficient. • Place check dams perpendicular to the flow of water. • The check dam should form a triangle when viewed from the side. This prevents undercutting as water flows over the face of the check dam rather than falling directly onto the ditch bottom. • Before installing check dams, impound and bypass upstream water flow away from the work area. Options for bypassing include pumps, siphons, or temporary channels. • Check dams combined with sumps work more effectively at slowing flow and retaining sediment than a check dam alone. A deep sump should be provided immediately upstream of the check dam. https://fortress.wa.gov/ecy/ershare/wq/Permits/Flare/2019SW M M W W/2019SWMM WW. htm#Topics/Volumel I/ConstructionStormwaterBMPs/Construct... 1 /3 5/29/24, 6:38 AM BMP C207: Check Dams • In some cases, if carefully located and designed, check dams can remain as permanent installations with very minor regrading. They may be left as either spillways, in which case accumulated sediment would be graded and seeded, or as check dams to prevent further sediment from leaving the site. • The maximum spacing between check dams shall be such that the downstream toe of the upstream dam is at the same elevation as the top of the downstream dam. • Keep the maximum height at 2 feet at the center of the check dam. • Keep the center of the check dam at least 12 inches lower than the outer edges at natural ground elevation. • Keep the side slopes of the check dam at 2H:1 V or flatter. • Key the stone into the ditch banks and extend it beyond the abutments a minimum of 18 inches to avoid washouts from overflow around the dam. • Use filter fabric foundation under a rock or sand bag check dam. If a blanket ditch liner is used, filter fabric is not necessary. A piece of organic or synthetic blanket cut to fit will also work for this purpose. • In the case of grass -lined ditches and swales, all check dams and accumulated sediment shall be removed when the grass has matured sufficiently to protect the ditch or swale - unless the slope of the swale is greater than 4 percent. The area beneath the check dams shall be seeded and mulched immediately after dam removal. • Ensure that channel appurtenances, such as culvert entrances below check dams, are not subject to damage or blockage from displaced stones. • See Figure II-3.16: Rock Check Dam. Maintenance Standards Check dams shall be monitored for performance and sediment accumulation during and after each rainfall that produces runoff. Sediment shall be removed when it reaches one half the sump depth. • Anticipate submergence and deposition above the check dam and erosion from high flows around the edges of the dam. • If significant erosion occurs between dams, install a protective riprap liner in that portion of the channel. See BMP C202: Rip Channel Lining. Approved as Functionally Equivalent Ecology has approved products as able to meet the requirements of this BMP. The products did not pass through the Technology Assessment Protocol — Ecology (TAPE) process. Local jurisdictions may choose not to accept these products, or may require additional testing prior to consideration for local use. Products that Ecology has approved as functionally equivalent are available for review on Ecology's website at: https://fortress.wa.gov/ecy/ershare/wq/Permits/Flare/2019SW M M W W/2019SWMM WW. htm#Topics/Volumel I/ConstructionStormwaterBMPs/Construct... 2/3 5/29/24, 6:38 AM BMP C207: Check Dams httpa //ecology.wa.gov/Regulations-Permits/Guidance-technical-assistance/Stormwater-pgrmittee-guidance- resources/Emerging-stormwater-treatment-technologies pdf download Figure II-3.16: Rock Check Dam Washington State Department of Ecology 2019 Stormwater Management Manual for Western Washington (2019 SWMMWW) Publication No.19-10-021 https:Hfortress.wa.gov/ecy/ershare/wq/Permits/Flare/2019SW M M W W/2019S W M M W W. htm#Topics/Vol umel I/ConstructionStormwaterBM Ps/Construct... 3/3 View Looking Upstream A 18" 12" (0.5m) (150mm) " (0.6m) Note: o� o w6 �.0 Key stone into channel banks and extend it beyond the abutments a minimum of 18" (0.5m) to prevent flow around dam. Section A -A j SDacina Between Check Dams 111111111111ft q%WWA DEPARTMENT OF ECOLOGY 'L' = the distance such that points Wand 'B' are of equal elevation. Rock Check Dam NOT TO SCALE Revised June 2016 Please see http://www.ecy.wa.gov/copyright.html for copyright notice including permissions, limitation of liability, and disclaimer. State of Washington 5/29/24, 6:39 AM BMP C235: Wattles • Construct trenches at intervals of 10- to 25-feet depending on the steepness of the slope, soil type, and rainfall. The steeper the slope the closer together the trenches. • Install the wattles snugly into the trenches and overlap the ends of adjacent wattles 12 inches behind one another. • Install stakes at each end of the wattle, and at 4-foot centers along entire length of wattle. • If required, install pilot holes for the stakes using a straight bar to drive holes through the wattle and into the soil. • Wooden stakes should be approximately 0.75 x 0.75 x 24 inches min. Willow cuttings or 3/8-inch rebar can also be used for stakes. • Stakes should be driven through the middle of the wattle, leaving 2 to 3 inches of the stake protruding above the wattle. Figure 11-3.24: Wattles pdf download Maintenance Standards • Wattles may require maintenance to ensure they are in contact with soil and thoroughly entrenched, especially after significant rainfall on steep sandy soils. • Inspect the slope after significant storms and repair any areas where wattles are not tightly abutted or water has scoured beneath the wattles. Approved as Functionally Equivalent Ecology has approved products as able to meet the requirements of this BMP. The products did not pass through the Technology Assessment Protocol — Ecology (TAPE) process. Local jurisdictions may choose not to accept these products, or may require additional testing prior to consideration for local use. Products that Ecology has approved as functionally equivalent are available for review on Ecology's website at: httpa //ecology.wa.gov/Regulations-Permits/Guidance-technical-assistance/Stormwater-pgrmittee-guidance- resources/Emerging-stormwater-treatment-technologies Washington State Department of Ecology 2019 Stormwater Management Manual for Western Washington (2019 SWMMWW) Publication No.19-10-021 https://fortress.wa.gov/ecy/ershare/wq/Permits/Flare/2019SW M M W W/2019SWMM WW. htm#Topics/Volumel I/ConstructionStormwaterBMPs/Construct... 2/2 3'- 4' 'JJ (1.2m) Overlap adjacent rolls 12" behind Straw rolls must be �� one another placed along slope contours X /1-11", 10' - 25' (3-8m) Spacing depends on soil type and slope steepness vhlhi�� qvwia DEPARTMENT OF ECOLOGY State of Washington Sediment, organic matter, and native seeds are captured behind the rolls. 3" - 5" (75-125mm) 8" - 10" Dia. (200-250mm) 1" x 1" Stake (25 x 25mm) NOTE: 1. Straw roll installation requires the placement and secure staking of the roll in a trench, 3" - 5" (75-125mm) deep, dug on contour. Runoff must not be allowed to run under or around roll. Wattles Revised December 2016 Please see http://www.ecy.wa.gov/copyright.html for copyright notice including permissions, limitation of liability, and disclaimer. Figure II-4.1.3 Channel Installation NOT Tn SCAT F LONGITUDINAL ANCHOR TRENCH TERMINAL SLOPE AND CHANNEL ANCHOR TRENCH STAKE AT 3'--5' P INTERVALS. INITIAL CHANNEL ANCHOR TRENCH CHECK SLOT AT 25' INTEI?WS INTERMITTENT CHECK SLOT Source: Clackamas County 2009 Notes: Erosion Prevention Planning and 1. Check slots to be constructed per manufacturers specifications. Design Manual 2. Staking or stapling layout per manufacturers specifications. � Figure II-4.1.3 Channel Installation DEPARTMENT OF Revised June2015 ECOLOGYPlease see http://www.ecy.wa.gov/copyright.html for copyright notice including permissions, State of Washington limitation of liability, and disclaimer. 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter 4 - Page 292 Figure II-4.1.4 Slope Installation Notes: 1. Slope surface shall be smooth before placement for proper soil contact. 2. Stapling pattern as per manufacturer's recommendations. 3. Do not stretch blankets/mattings tight - allow the rolls to mold to any irregularities. 4. For slopes less than 3H:1 V, rolls may be placed in horizontal strips. 5. If there is a berm at the top of the slope, anchor upslope of the berm. 6. Lime, fertilize, and seed before installation. Planting of shrubs, trees, etc. should occur after installation. aaw� DEPARTMENT OF ECOLOGY State of Washington area, turn the end under 4" and staple at 12" intervals Figure II-4.1.4 Slope Installation NOT TO SCALE Revised June 2015 Please see http.//www.ecy.wa.gov/copyright.html for copyright notice including permissions, limitation of liability, and disclaimer. 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter 4 - Page 293 BMP C123: Plastic Covering Purpose Plastic covering provides immediate, short-term erosion protection to slopes and dis- turbed areas. Conditions of Use Plastic covering may be used on disturbed areas that require cover measures for less than 30 days, except as stated below. • Plastic is particularly useful for protecting cut and fill slopes and stockpiles. Note: The relatively rapid breakdown of most polyethylene sheeting makes it unsuitable for long-term (greater than six months) applications. • Due to rapid runoff caused by plastic covering, do not use this method upslope of areas that might be adversely impacted by concentrated runoff. Such areas include steep and/or unstable slopes. . Plastic sheeting may result in increased runoff volumes and velocities, requiring additional on -site measures to counteract the increases. Creating a trough with wattles or other material can convey clean water away from these areas. . To prevent undercutting, trench and backfill rolled plastic covering products. . While plastic is inexpensive to purchase, the added cost of installation, main- tenance, removal, and disposal make this an expensive material, up to $1.50-2.00 per square yard. . Whenever plastic is used to protect slopes install water collection measures at the base of the slope. These measures include plastic -covered berms, channels, and pipes used to covey clean rainwater away from bare soil and disturbed areas. Do not mix clean runoff from a plastic covered slope with dirty runoff from a project. . Other uses for plastic include: 1. Temporary ditch liner. 2. Pond liner in temporary sediment pond. 3. Liner for bermed temporary fuel storage area if plastic is not reactive to the type of fuel being stored. 4. Emergency slope protection during heavy rains. 5. Temporary drainpipe ("elephant trunk") used to direct water. 2014 Stormwater Management Manual for Western Washington Volume II - Chapter 4 - Page 294 Design and Installation Specifications Plastic slope cover must be installed as follows: 1. Run plastic up and down slope, not across slope. 2. Plastic may be installed perpendicular to a slope if the slope length is less than 10 feet. 3. Minimum of 8-inch overlap at seams. 4. On long or wide slopes, or slopes subject to wind, tape all seams. 5. Place plastic into a small (12-inch wide by 6-inch deep) slot trench at the top of the slope and backfill with soil to keep water from flowing underneath. 6. Place sand filled burlap or geotextile bags every 3 to 6 feet along seams and tie them together with twine to hold them in place. 7. Inspect plastic for rips, tears, and open seams regularly and repair imme- diately. This prevents high velocity runoff from contacting bare soil which causes extreme erosion. 8. Sandbags may be lowered into place tied to ropes. However, all sandbags must be staked in place. • Plastic sheeting shall have a minimum thickness of 0.06 millimeters. . If erosion at the toe of a slope is likely, a gravel berm, riprap, or other suitable pro- tection shall be installed at the toe of the slope in order to reduce the velocity of run- off. Maintenance Standards . Torn sheets must be replaced and open seams repaired. . Completely remove and replace the plastic if it begins to deteriorate due to ultra- violet radiation. . Completely remove plastic when no longer needed. • Dispose of old tires used to weight down plastic sheeting appropriately. Approved as Equivalent Ecology has approved products as able to meet the requirements of BMP C123: Plastic Covering. The products did not pass through the Technology Assessment Protocol — Ecology (TAPE) process. Local jurisdictions may choose not to accept this product approved as equivalent, or may require additional testing prior to consideration for local use. The products are available for review on Ecology's website at http://www.ecy.wa.gov/programs/wq/stormwater/newtech/equivalent.html 2014 Stormwater Management Manual for Western Washington Volume 11- Chapter 4 - Page 295 BMP C124: Sodding Purpose The purpose of sodding is to establish permanent turf for immediate erosion protection and to stabilize drainage ways where concentrated overland flow will occur. Conditions of Use Sodding may be used in the following areas: . Disturbed areas that require short-term or long-term cover. . Disturbed areas that require immediate vegetative cover. . All waterways that require vegetative lining. Waterways may also be seeded rather than sodded, and protected with a net or blanket. Design and Installation Specifications Sod shall be free of weeds, of uniform thickness (approximately 1-inch thick), and shall have a dense root mat for mechanical strength. The following steps are recommended for sod installation: . Shape and smooth the surface to final grade in accordance with the approved grad- ing plan. The swale needs to be overexcavated 4 to 6 inches below design elev- ation to allow room for placing soil amendment and sod. . Amend 4 inches (minimum) of compost into the top 8 inches of the soil if the organic content of the soil is less than ten percent or the permeability is less than 0.6 inches per hour. See http://www.ecy.wa.gov/programs/swfa/organics/soil.html for further information. . Fertilize according to the supplier's recommendations. . Work lime and fertilizer 1 to 2 inches into the soil, and smooth the surface. . Lay strips of sod beginning at the lowest area to be sodded and perpendicular to the direction of water flow. Wedge strips securely into place. Square the ends of each strip to provide fora close, tightfit. Staggerjoints at least 12 inches. Staple on slopes steeper than 3HI V. Staple the upstream edge of each sod strip. . Roll the sodded area and irrigate. . When sodding is carried out in alternating strips or other patterns, seed the areas between the sod immediately after sodding. 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter 4 - Page 296 Maintenance Standards If the grass is unhealthy, the cause shall be determined and appropriate action taken to reestablish a healthy groundcover. If it is impossible to establish a healthy groundcover due to frequent saturation, instability, or some other cause, the sod shall be removed, the area seeded with an appropriate mix, and protected with a net or blanket. BMP C125: Topsoiling / Composting Purpose Topsoiling and composting provide a suitable growth medium for final site stabilization with vegetation. While not a permanent cover practice in itself, topsoiling and com- posting are an integral component of providing permanent cover in those areas where there is an unsuitable soil surface for plant growth. Use this BMP in conjunction with other BMPs such as seeding, mulching, or sodding. Note that this BMP is functionally the same as BMP T5.13: Post -Construction Soil Quality and Depth (p.911) which is required for all disturbed areas that will be developed as lawn or landscaped areas at the completed project site. Native soils and disturbed soils that have been organically amended not only retain much more stormwater, but they also serve as effective biofilters for urban pollutants and, by supporting more vigorous plant growth, reduce the water, fertilizer and pesticides needed to support installed landscapes. Topsoil does not include any subsoils but only the material from the top several inches including organic debris. Conditions of Use Permanent landscaped areas shall contain healthy topsoil that reduces the need forfertilizers, improves overall topsoil quality, provides for better vegetal health and vitality, improves hydrologic characteristics, and reduces the need for irrigation. Leave native soils and the duff layer undisturbed to the maximum extent prac- ticable. Stripping of existing, properly functioning soil system and vegetation for the purpose of topsoiling during construction is not acceptable. Preserve existing soil systems in undisturbed and uncompacted conditions if functioning properly. . Areas that already have good topsoil, such as undisturbed areas, do not require soil amendments. . Restore, to the maximum extent practical, native soils disturbed during clearing and grading to a condition equal to or better than the original site condition's mois- ture -holding capacity. Use on -site native topsoil, incorporate amendments into on - site soil, or import blended topsoil to meet this requirement. . Topsoiling is a required procedure when establishing vegetation on shallow soils, and soils of critically low pH (high acid) levels. 2014 Stormwater Management Manual for Western Washington Volume 11- Chapter 4 - Page 297 Beware of where the topsoil comes from, and what vegetation was on site before disturbance, invasive plant seeds may be included and could cause problems for establishing native plants, landscaped areas, or grasses. Topsoil from the site will contain mycorrhizal bacteria that are necessary for healthy root growth and nutrient transfer. These native mycorrhiza are acclimated to the site and will provide optimum conditions for establishing grasses. Use com- mercially available mycorrhiza products when using off -site topsoil. Design and Installation Specifications Meet the following requirements for disturbed areas that will be developed as lawn or landscaped areas at the completed project site: . Maximize the depth of the topsoil wherever possible to provide the maximum pos- sible infiltration capacity and beneficial growth medium. Topsoil shall have: A minimum depth of 8-inches. Scarify subsoils below the topsoil layer at least 4-inches with some incorporation of the upper material to avoid stratified lay- ers, where feasible. Ripping or re -structuring the subgrade may also provide additional benefits regarding the overall infiltration and interflow dynamics of the soil system. A minimum organic content of 10% dry weight in planting beds, and 5% organic matter content in turf areas. Incorporate organic amendments to a minimum 8-inch depth except where tree roots or other natural features limit the depth of incorporation. A pH between 6.0 and 8.0 or matching the pH of the undisturbed soil. O If blended topsoil is imported, then fines should be limited to 25 percent passing through a 200 sieve. Mulch planting beds with 2 inches of organic material Accomplish the required organic content, depth, and pH by returning native topsoil to the site, importing topsoil of sufficient organic content, and/or incorporating organic amendments. When using the option of incorporating amendments to meet the organic content requirement, use compost that meets the compost specification for Bioretention (See BMP T7.30: Bioretention Cells, Swales, and Planter Boxes 959 ), with the exception that the compost may have up to 35% biosolids or manure. . Sections three through seven of the document entitled, Guidelines and Resources for Implementing Soil Quality and Depth BMP T5.13 in WDOE Stormwater Man- agement Manual for Western Washington, provides useful guidance for imple- menting whichever option is chosen. It includes guidance for pre -approved default strategies and guidance for custom strategies. Check with your local jurisdiction 2014 Stormwater Management Manual for Western Washington Volume II - Chapter 4 - Page 298 concerning its acceptance of this guidance. It is available through the organization, Soils for Salmon. As of this printing the document may be found at: http://www.soils- forsalmon.org/pdf/Soil BMP Manual.pdf. . The final composition and construction of the soil system will result in a natural selection or favoring of certain plant species over time. For example, incorporation of topsoil may favor grasses, while layering with mildly acidic, high -carbon amend- ments may favor more woody vegetation. . Allow sufficient time in scheduling for topsoil spreading prior to seeding, sodding, or planting. . Take care when applying top soil to subsoils with contrasting textures. Sandy top- soil over clayey subsoil is a particularly poor combination, as water creeps along the junction between the soil layers and causes the topsoil to slough. If topsoil and subsoil are not properly bonded, water will not infiltrate the soil profile evenly and it will be difficult to establish vegetation. The best method to prevent a lack of bond- ing is to actually work the topsoil into the layer below for a depth of at least 6 inches. . Field exploration of the site shall be made to determine if there is surface soil of suf- ficient quantity and quality to justify stripping. Topsoil shall be friable and loamy (loam, sandy loam, silt loam, sandy clay loam, and clay loam). Avoid areas of nat- ural ground water recharge. . Stripping shall be confined to the immediate construction area. A 4-inch to 6-inch stripping depth is common, but depth may vary depending on the particular soil. All surface runoff control structures shall be in place prior to stripping. . Do not place topsoil while in a frozen or muddy condition, when the subgrade is excessively wet, or when conditions exist that may otherwise be detrimental to proper grading or proposed sodding or seeding. . In any areas requiring grading remove and stockpile the duff layer and topsoil on site in a designated, controlled area, not adjacent to public resources and critical areas. Stockpiled topsoil is to be reapplied to other portions of the site where feas- ible. . Locate the topsoil stockpile so that it meets specifications and does not interfere with work on the site. It may be possible to locate more than one pile in proximity to areas where topsoil will be used. Stockpiling of topsoil shall occur in the following manner: • Side slopes of the stockpile shall not exceed 2H:1 V. • Between October 1 and April 30: 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter 4 - Page 299 . An interceptor dike with gravel outlet and silt fence shall surround all topsoil. . Within 2 days complete erosion control seeding, or covering stockpiles with clear plastic, or other mulching materials. . Between May 1 and September 30: . An interceptor dike with gravel outlet and silt fence shall surround all topsoil if the stockpile will remain in place for a longer period of time than active construction grading. . Within 7 days complete erosion control seeding, or covering stockpiles with clear plastic, or other mulching materials. . When native topsoil is to be stockpiled and reused the following should apply to ensure that the mycorrhizal bacterial, earthworms, and other beneficial organisms will not be destroyed: 1. Re -install topsoil within 4 to 6 weeks. 2. Do not allow the saturation of topsoil with water. 3. Do not use plastic covering. Maintenance Standards . Inspect stockpiles regularly, especially after large storm events. Stabilize any areas that have eroded. • Establish soil quality and depth toward the end of construction and once estab- lished, protect from compaction, such as from large machinery use, and from erosion. . Plant and mulch soil after installation. • Leave plant debris or its equivalent on the soil surface to replenish organic matter. . Reduce and adjust, where possible, the use of irrigation, fertilizers, herbicides and pesticides, rather than continuing to implement formerly established practices. BMP C126: Polyacrylamide (PAM) for Soil Erosion Protection Purpose Polyacrylamide (PAM) is used on construction sites to prevent soil erosion. Applying PAM to bare soil in advance of a rain event significantly reduces erosion and controls sediment in two ways. First, PAM increases the soil's available pore volume, 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter 4 - Page 300 1. If the discharge velocity at the outlet is less than 5 fps (pipe slope less than 1 percent), use 2-inch to 8-inch riprap. Minimum thickness is 1-foot. 2. For 5 to 10 fps discharge velocity at the outlet (pipe slope less than 3 per- cent), use 24-inch to 48-inch riprap. Minimum thickness is 2 feet. 3. For outlets at the base of steep slope pipes (pipe slope greater than 10 per- cent), an engineered energy dissipater shall be used. . Filter fabric or erosion control blankets should always be used under riprap to pre- vent scour and channel erosion. New pipe outfalls can provide an opportunity for low-cost fish habitat improve- ments. For example, an alcove of low -velocity water can be created by con- structing the pipe outfall and associated energy dissipater back from the stream edge and digging a channel, over -widened to the upstream side, from the outfall. Overwintering juvenile and migrating adult salmonids may use the alcove as shel- ter during high flows. Bank stabilization, bioengineering, and habitat features may be required for disturbed areas. This work may require a HPA. See Volume V 765 for more information on outfall system design. Maintenance Standards . Inspect and repair as needed. . Add rock as needed to maintain the intended function. . Clean energy dissipater if sediment builds up. BMP C22O: Storm Drain Inlet Protection Purpose Storm drain inlet protection prevents coarse sediment from entering drainage systems prior to permanent stabilization of the disturbed area. Conditions of Use Use storm drain inlet protection at inlets that are operational before permanent sta- bilization of the disturbed drainage area. Provide protection for all storm drain inlets downslope and within 500 feet of a disturbed or construction area, unless conveying run- off entering catch basins to a sediment pond or trap. Also consider inlet protection for lawn and yard drains on new home construction. These small and numerous drains coupled with lack of gutters in new home construction can add significant amounts of sediment into the roof drain system. If possible delay installing lawn and yard drains until just before landscaping or cap these drains to pre- 2014 Stormwater Management Manual for Western Washington Volume 11- Chapter 4 - Page 357 vent sediment from entering the system until completion of landscaping. Provide 18- inches of sod around each finished lawn and yard drain. Table II-4.2.2 Storm Drain Inlet Protection .358 lists several options for inlet protection. All of the methods for storm drain inlet protection tend to plug and require a high fre- quency of maintenance. Limit drainage areas to one acre or less. Possibly provide emer- gency overflows with additional end -of -pipe treatment where stormwater ponding would cause a hazard. Table II-4.2.2 Storm Drain Inlet Protection Type of Inlet Emergency Applicable for Protection Overflow Paved/ Earthen Conditions of Use Surfaces Drop Inlet Protection Excavated drop Yes, tem- Applicable for heavy flows. Easy protection inleting porary flood- Earthen to maintain. Large area Require- will occur ment: 30'x30'/acre Block and Applicable for heavy concentrated gravel drop inlet Yes Paved or Earthen flows. Will not pond. protection Gravel and wire Applicable for heavy concentrated drop inlet pro- No flows. Will pond. Can withstand tection traffic. Catch basin fil- Yes Paved or Earthen Frequent Maintenance required. to rs Curb Inlet Protection Curb inlet pro- Small capacity Used for sturdy, more compact tection with overflow Paved installation. wooden weir Block and gravel curb inlet Yes Paved Sturdy, but limited filtration. protection Culvert Inlet Protection Culvert inlet Sed 18 month expected life. iment trap Design and Installation Specifications Excavated Drop Inlet Protection - An excavated impoundment around the storm drain. Sediment settles out of the stormwater prior to entering the storm drain. 2014 Stormwater Management Manual for Western Washington Volume 11- Chapter 4 - Page 358 . Provide a depth of 1-2 ft as measured from the crest of the inlet structure. . Slope sides of excavation no steeper than 2H:1V. . Minimum volume of excavation 35 cubic yards. . Shape basin to fit site with longest dimension oriented toward the longest inflow area. . Install provisions for draining to prevent standing water problems. . Clear the area of all debris. • Grade the approach to the inlet uniformly. • Drill weep holes into the side of the inlet. . Protect weep holes with screen wire and washed aggregate. • Seal weep holes when removing structure and stabilizing area. . Build a temporary dike, if necessary, to the down slope side of the structure to pre- vent bypass flow. Block and Gravel Filter- A barrier formed around the storm drain inlet with standard con- crete blocks and gravel. See Figure II-4.2.8 Block and Gravel Filter (p.360). . Provide a height of 1 to 2 feet above inlet. . Recess the first row 2-inches into the ground for stability. • Support subsequent courses by placing a 2x4 through the block opening. • Do not use mortar. . Lay some blocks in the bottom row on their side for dewatering the pool. • Place hardware cloth or comparable wire mesh with'/2-inch openings overall block openings. • Place gravel just below the top of blocks on slopes of2H:1V orflatter. . An alternative design is a gravel donut. . Provide an inlet slope of 3H:1 V. • Provide an outlet slope of 2H:1 V. . Provide al-footwide level stone area between the structure and the inlet. . Use inlet slope stones 3 inches in diameter or larger. • Use gravel '/2- to 3/4-inch at a minimum thickness of 1-foot for the outlet slope. 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter 4 - Page 359 Figure II-4.2.8 Block and Gravel Filter Drain grate A I91"F IXT , crete block Gravel backfill Concrete block Wire screen or filter fabric Gravel backfillOverflow water OX Ponding height Drop inlet Section A -A Notes: 1. Drop inlet sediment barriers are to be used for small, nearly level drainage areas. (less than 5%) 2. Excavate a basin of sufficient size adjacent to the drop inlet. 3. The top of the structure (ponding height) must be well below the ground elevation downslope to prevent runoff from bypassing the inlet. A temporary dike may be necessary on the downslope side of the structure. aaft� DEPARTMENT OF ECOLOGY State of Washington Figure II-4.2.8 Block and Gravel Filter NOT TO SCALE Revised August 2015 Please see http.//www.ecy.wa.gov/copyright.html for copyright notice including permissions, limitation of liability, and disclaimer. 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter 4 - Page 360 Gravel and Wire Mesh Filter - A gravel barrier placed over the top of the inlet. This struc- ture does not provide an overflow. • Use a hardware cloth or comparable wire mesh with'/2-inch openings. . Use coarse aggregate. • Provide a height 1-foot or more, 18-inches wider than inlet on all sides. • Place wire mesh over the drop inlet so that the wire extends a minimum of 1-foot beyond each side of the inlet structure. • Overlap the strips if more than one strip of mesh is necessary. . Place coarse aggregate over the wire mesh. • Provide at least a 12-inch depth of gravel over the entire inlet opening and extend at least 18-inches on all sides. Catchbasin Filters — Use inserts designed by manufacturers for construction sites. The limited sediment storage capacity increases the amount of inspection and maintenance required, which may be daily for heavy sediment loads. To reduce maintenance require- ments combine a catchbasin filter with another type of inlet protection. This type of inlet protection provides flow bypass without overflow and therefore may be a better method for inlets located along active rights -of -way. . Provides 5 cubic feet of storage. . Requires dewatering provisions. • Provides a high -flow bypass that will not clog under normal use at a construction site. . Insert the catchbasin filter in the catchbasin just below the grating. Curb Inlet Protection with Wooden Weir— Barrier formed around a curb inlet with a wooden frame and gravel. . Use wire mesh with'/2-inch openings. • Use extra strength filter cloth. • Construct a frame. . Attach the wire and filter fabric to the frame. . Pile coarse washed aggregate against wire/fabric. • Place weight on frame anchors. Block and Gravel Curb Inlet Protection — Barrier formed around a curb inlet with concrete blocks and gravel. See Figure II-4.2.9 Block and Gravel Curb Inlet Protection (p.363). 2014 Stormwater Management Manual for Western Washington Volume II - Chapter 4 - Page 361 • Use wire mesh with'/2-inch openings. . Place two concrete blocks on their sides abutting the curb at either side of the inlet opening. These are spacer blocks. . Place a 2x4 stud through the outer holes of each spacer block to align the front blocks. • Place blocks on their sides across the front of the inlet and abutting the spacer blocks. • Place wire mesh over the outside vertical face. . Pile coarse aggregate against the wire to the top of the barrier. Curb and Gutter Sediment Barrier— Sandbag or rock berm (riprap and aggregate) 3 feet high and 3 feet wide in a horseshoe shape. See Figure II-4.2.10 Curb and Gutter Barrier 364 . . Construct a horseshoe shaped berm, faced with coarse aggregate if using riprap, 3 feet high and 3 feet wide, at least 2 feet from the inlet. Construct a horseshoe shaped sedimentation trap on the outside of the berm sized to sediment trap standards for protecting a culvert inlet. Maintenance Standards . Inspect catch basin filters frequently, especially after storm events. Clean and replace clogged inserts. For systems with clogged stone filters: pull away the stones from the inlet and clean or replace. An alternative approach would be to use the clogged stone as fill and put fresh stone around the inlet. Do not wash sediment into storm drains while cleaning. Spread all excavated material evenly over the surrounding land area or stockpile and stabilize as appro- priate. Approved as Equivalent Ecology has approved products as able to meet the requirements of BMP C220: Storm Drain Inlet Protection. The products did not pass through the Technology Assessment Protocol — Ecology (TAPE) process. Local jurisdictions may choose not to accept this product approved as equivalent, or may require additional testing prior to consideration for local use. The products are available for review on Ecology's website at http://www.ecy.wa.gov/programs/wq/stormwater/newtech/equivalent.html 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter 4 - Page 362 Figure II-4.2.9 Block and Gravel Curb Inlet Protection A Catch basin Back of sidewalk //2/x4 Wood stud Back of curb Curb inlet — r \\CCD Concrete block a S Wire screen or ° filter fabric %4 inch (20 mm) A Concrete block Drain gravel Plan View Ponding height Y4 inch (20 mm) Drain gravel Overflow Curb inlet Wire screen or filter fabric 2x4 Wood stud (100x50 Timber stud) \� Catch basin \ j Concrete block Section A -A Notes: 1. Use block and gravel type sediment barrier when curb inlet is located in gently sloping street segment, where water can pond and allow sediment to separate from runoff. 2. Barrier shall allow for overflow from severe storm event. 3. Inspect barriers and remove sediment after each storm event. Sediment and gravel must be removed from the traveled way immediately. NOT TO SCALE aaft� Figure II-4.2.9 Block and Gravel Curb Inlet Protection DEPARTMENT OF Revised August 2015 ECOLOGYPlease see http.//www.ecy.wa.gov/copyright.html for copyright notice including permissions, State of Washington limitation of liability, and disclaimer. 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter 4 - Page 363 Figure II-4.2.10 Curb and Gutter Barrier Back of sidewalk Burlap sacks to overlap onto curb Back of curb Runoff Runoff _ / Spillway Plan View Gravel filled sandbags stacked tightly Curb inlet Catch basin Notes: 1. Place curb type sediment barriers on gently sloping street segments, where water can pond and allow sediment to separate from runoff. 2. Sandbags of either burlap or woven 'geotextile' fabric, are filled with gravel, layered and packed tightly. 3. Leave a one sandbag gap in the top row to provide a spillway for overflow. 4. Inspect barriers and remove sediment after each storm event. Sediment and gravel must be removed from the traveled way immediately. NOT TO SCALE aaft� Figure II-4.2.10 Curb and Gutter Barrier DEPARTMENT OF Revised September 2015 ECOLOGYPlease see http.//www.ecy.wa.gov/copyright.html for copyright notice including permissions, State of Washington limitation of liability, and disclaimer. 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter 4 - Page 364