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BLD2020-0894+SWPPP+8.25.2020_10.01.23_AM7ESTERN WE 9740 Evergreen Way Everett, WA 98204 SURVEYORS P: (425) 356-2700 F: (425) 356-2708 W: WESI.CO SURVEYORS • ENGINEERS • LAND USE CONSULTANTS Harris Duplex PFN 20- SW V4, SW '/a, SEC 20, T 27N, R 04E W.M. Storm Water Pollution Prevention Plan PROJECT LOCATION: 21022 74111 Avenue W Edmonds, WA 98026 Issue Date: April 2nd, 2020 Revision Date: PREPARED BY. - Nathan A. Thompson, E.T. REVIE TVED BY: Jesse A. Jarrell, P.E. Owner: David Harris Enterprises 19702 20"' Avenue NW Shoreline, WA 98177 Office: (206) 795-2009 Cell: (206) 546-5392 20-1866-A/SWPPP.doc En:;ineer• Western Engineers & Surveyors, Inc. 9740 Evergreen Way Everett, WA 98204 425-356-2700 WESTERN ENGINEERS © 2020 Harris Duplex TABLE OF CONTENTS Page CONSTRUCTION STORMWATER POLLUTION PREVENTIONELEMENTS.......................................................................2 PROJECTDESCRIPTION..............................................................................................3 EXISTINGCONDITIONS...............................................................................................3 ADJACENTAREAS.........................................................................................................4 SITE FEATURES AND SENSITIVE AREAS...............................................................4 SOILS..................................................................................................................................4 EROSIONPROBLEMS AREAS.....................................................................................4 CONSTRUCTIONPHASING..........................................................................................5 CONSTRUCTIONSCHEDULE......................................................................................5 FINANCIAL/OWNERSHIP AND RESPONSIBILITIES........................................................................................................6 ENGINEERING CALCULATIONS...............................................................................6 APPENDIXA - T.E.S.C. & Grading Plan......................................................................7 APPENDIXB - Soil Information.....................................................................................9 JOB NO: 20-1868-A Harris Duplex 1. CONSTRUCTION STORM WATER POLLUTION PREVENTION ELEMENTS Element #1: Mark Clearing Limits Clearing limits have been shown on the Temporary Erosion and Sedimentation Control Plans. Element #2: Establish Construction Entrance A temporary construction entrance shall be established in the southeast location of the site. All vehicles shall be free of debris prior to leaving the site. Element # 3: Control Flow Rates Flow rates during construction are to be contained through the installation of silt fencing along the southern and western clearing limits. Element # 4: Install Sediment Controls Sediment controls mainly consist of installing silt fencing along the southern and western clearing limits. Element # 5: Stabilize Soils All soils disturbed during site grading will be stabilized by use of the most appropriate BMP method available. These consist of short-term and long-term solutions. Short-term methods consist of compaction of the soils by vibratory roller or bulldozer. Long-term methods consist of straw covering over the soils (this is in the case of the project becoming dormant for greater than 1 month). At this time no wintertime grading or construction activities will occur. During construction periods longer than 1 working week (7 days) where the soils are exposed and un-worked will use the proscribed methods in the Storm Water Management Manual for Western Washington to reduce sedimentation transported offsite. If winter grading is conducted, all exposed soils shall be covered within 2 days. Element # 6: Protect Slopes There are no steep slopes on or near the site. Element 6 does not apply. Element # 7: Protect Drain Inlets Downstream inlets will be protected with catch basin inserts or equivalent. Element # 8: Stabilize Channels and Outlets The need for channel stabilization is not expected but, existing channels or drainage outlets located within 500-feet of the property of the property should be routinely inspected for debris that may dam and/or aid erosion. Element # 9: Control Pollutants All pollutants from construction vehicles will be contained and disposed of in the approved manner consistent with state environmental policies. Any vehicle maintenance will be performed by authorized mechanics using drip pans and waste containment vessels. All pollutants will be disposed offsite at approved facilities. JOB NO: 20-1868-A Harris Duplex Element # 10: Control De -Watering De -watering of the site is not expected. If dewatering of the site is needed, all groundwater removed shall be retained and recharged into the ground after de - watering has been finalized. Element # 11: Maintain BMPs All Temporary Erosion and Sedimentation Control (TESC) devices and equipment will be inspected and maintained on a weekly basis if not sooner, based on storm events contributing to runoff. When construction is complete and the site is stabilized, any existing sediment will be removed and stabilized onsite. Element # 12: Manage the Project A general construction manager will manage the project for or by the owners. The construction manager shall maintain all of the above items in order to minimize sediment transport and turbid water leaving the site. His job will entail continual observation of the grading operations to ensure minimal effects to adjacent properties and offsite waterways. Element # 13: Protect On -Site Stormwater Management BMPs Stormwater management mainly consists of infiltration and soil amendment BMPs. Soil amendment areas will be protected from siltation and compaction when feasible. 2. PROJECT DESCRIPTION The proposed project consists entirely of clearing/grading for the construction of a new Duplex, and an associated driveway and drainage improvements. Drainage management for new roof areas is to consist primarily of BMP T5.10A a 9'xl5' Gravel Filled Infiltration Trench. Drainage management for new driveway, walk, and patio areas will consist of a 36 sf rain garden per BMP T5.14A. Total new impervious area proposed for the project total 3,443 sf. located within the boundary lines of the site. The project is to be designed to the DOE 2019 Stormwater Management Manual for Western Washington along with city of Edmonds 2017 Stormwater Manual. 3. EXISTING CONDITIONS The property is a one tax parcel and currently contains a single-family residence with its respective concrete driveway. Vegetation on -site consists of residential lawn areas, and partial tree covering. Slopes on -site are moderate, ranging from 2% to 8%, and sloping southeasterly toward adjacent properties to the south. From a Snohomish County Soil Survey done by USDA the soils on -site consist of Alderwood Urban Land Complex type soils. According to a site investigation by JOB NO: 20-1868-A Harris Duplex Cobalt Geosciences, LLC on March 301h, 2020, on -site soils resemble medium gray sand with gravel type soils. Refer to Appendix B for soil information. 4. ADJACENT AREAS Surrounding parcels are developed with existing SFRs and driveways. Vegetation in the surrounding area is comprised primarily of residential lawn and second/third growth forest. 5. SITE FEATURES AND SENSITIVE AREAS Vegetation on -site consists of residential lawn areas, and partial tree covering. Slopes on -site are moderate, ranging from 2% to 8%, and sloping southeasterly toward adjacent properties to the south. From a Snohomish County Soil Survey done by USDA the soils on -site consist of Alderwood Urban Land Complex type soils. According to a site investigation by Cobalt Geosciences, LLC on March 301h, 2020, on -site soils resemble medium gray sand with gravel type soils. Refer to Appendix B for soil information. POTENTIAL SOURCES OF POLLUTION Potential temporary sources of pollution include possible fuel spillage during construction. All major fuel spillage during construction are to be cleaned up immediately. No long-term potential sources of pollution are expected from the development. 6. SOILS From Soil Survey of Snohomish County Area Washington as sited in the Full Drainage Report, the soils on -site consist of Alderwood Urban Land Complex type soils. According to a site investigation by Cobalt Geosciences, LLC on March 30th, 2020, on -site soils resemble medium gray sand with gravel type soils. Refer to Appendix II for soil information. 7. EROSION PROBLEM AREAS No major erosion problem areas have been discovered for the site. JOB NO: 20-1868-A Harris Duplex 8. CONSTRUCTION PHASING Construction Sequence 1. Pre -construction meeting. 2. Flag or fence clearing limits. 3. Install perimeter protection (silt fence, brush barrier, etc.). 4. Construct surface water controls (interceptor dikes, pipe slope drains, etc.) simultaneously with clearing and grading for project development. 5. Maintain erosion control measures in accordance with Snohomish county standards and manufacturer's recommendations. 6. Cover all areas that will be unworked for more than seven days during the dry season or two days during the wet season with straw, wood fiber mulch, compost, plastic sheeting or equivalent. 7. Stabilize all areas that reach final grade within seven days. 8. Seed or sod any areas to remain unworked for more than 30 days. 9. Upon completion of the project, all disturbed areas must be stabilized and best management practices removed if appropriate. 10. All temporary erosion and sediment control measures shall be removed within 30 days after final site stabilization is achieved or after the temporary BMP's are no longer needed. Trapped sediment shall be removed or stabilized on site. Disturbed soil areas resulting from removal shall be permanently stabilized. PHASE CONSTRUCTION ACTIVITY No planned phased construction is expected. 9. CONSTRUCTION SCHEDULE BMP implementation schedule listed below is keyed to proposed phases of the construction project, and reflects differences in BMP installations and inspections that relate to wet and dry season construction. As such, the dry season is considered to be from May 1 to September 30 and the wet season is considered to be from October 1 to April 30. ■ Estimate of Construction start date: 07 / 01 / 2020 ■ Estimate of Construction finish date: 09 / 30 / 2020 ■ Mobilize equipment on site: 07 / 01 / 2020 ■ Clear Vegetation From Site and begin driveway placement 07 / 03 / 2020 ■ Re -grade site and begin foundation placement 07 / 05 / 2020 ■ Complete construction 09 / 10 / 2020 ■ Complete Hydroseeding and Soil Stabilization 09 / 30 / 2020 JOB NO: 20-1868-A Harris Duplex 10. FINANCIAL/OWNERSHIP AND RESPONSIBILITIES Current Owner(s): Dave Harris 19702 20th Avenue NW Shoreline, WA 98177 Bonds and Financial Responsibility Prior to issuance of the grading, the owner/developer is required to establish the necessary erosion control and drainage bonding with Snohomish County. Along with that, the permits will require establishing general liability insurance from the proposed contractor. 11. ENGINEERING CALCULATIONS Sediment Pond/Trap N/A Diversions No diversions are needed for this project Waterways Construction on site will not have any effect on adjacent waterways. JOB NO: 20-1868-A Harris Duplex APPENDIX A SWPPP & GRADING PLAN JOB NO: 20-1868-A SW 114, SW 114, SEC.20, T.27N, R.04E, W.M. CITY OF EDMONDS, WASHINGTON NEW 1'-3' BLOCK WALL TOP-410.0 TOE=407.0 BACK OF WALL SHALL BE SET I BACK A MIN. OF 3' FROM EX. BLOCK WALLS FACE OF ADJ. WALL 2' TALL N89'21'50"E EX. BLOCK WALL 36.01, N01'59'30"w (-2 TALL) E 4.00 3'WDF *21'507E 6'WDF 410 N%'50 i7.82' °a gX. CONC.c TEMP. a STOCKPILE ° °, SFR( IN 9 apB ® FF= iQ.5 6'WOF TAXJ60566900400106 SFRI 21014 I 72 2.00' APARTMENT a°.el_ \ ° COMPLEX- 121026 a—� M MINIMIZE COMPACTION OF FUTURE INFILTRATION ° AREA A5 FEASIBLE 120. 5'WDF SOIL RETENTION AND AMENDMENT SYMBOLS. ALL EXISTING TOPSOIL, SHALL BE STRIPED AND: TAXfJ00566900400203 STOCKPILED TO BE REAPPLIED' WITH COMPOST AMENOMENIS.: TEMPORARY SILT FENCE TO SEE NOTES, THIS SHEET ALONG' MITIGATE CONSTRUCTION RUNOFF. WITH INFO SUPPLIED IN INSTALL ALONG SOUTH EDGE OF APPENDIX III OF THE FULL C CONSTRUCTION LIMITS. STORMWATER DRAINAGE REPORT SOLI, LOGS TEST PIT 1 (7P0 0"-8": TOPSOIVVEGETATION LOOSE TO MEDIUM DENSE SILTY -FINE TO MEDIUM GRAINED SAND WITH GRAVEL, YELLOWISH BROWN, MOIST. (WEATHERED ADVANCE OUTWASH) 48"-120' MEDIUM DENSE TO DENSE, FINE TO MEDIUM GRAINED SAND WITH GRAVEL, GRAYISH BROWN, MOIST. (ADVANCE OUTWASH) NO GROUNDWATER WAS ENCOUNTERED GRADING QUANTITIES CUT.• 120 CUBIC YARDS FILL 120 CUBIC YARDS SCALE: 1" = 20' 0 20 40 Western Engineers & T Surveyors SURVEYORS o PLANNERS o ENGINEERS EX. CONC. WALL TALL) 410 / N1126.40-W / 30.01, -- - 9'30'IV PROPOSED PORTION OF i FOOTPRINT OF ROCKERY F RESIDENCE F 3 DWY INSTALLI 40a a TEMPORARY CONSTRUCTIO zo ENTRANCE o y TP11 N • D TBR) h0� J °EX. CONC., ° d/U 406 ° SS FX AF a 30.01' APPROX. LO ION 0 a04 EX. SEWER STUB PER I APR OX. LOCATION OWNER DESCRIP ION OF EX. 8" D.I. WATER EX. DRIVEWAY ON PROPERTY I MAIN PER CITY " SHALL NOT BE REZVED WITHOUT MAPPING PROPERTY OWNER PERM❑IS,SJ �� o EX CB � RIPd=403.61' � I DRARW ELD NOTE SWPPP L GEND ACCORDING TO SNOHOMISH COUNTY ^^^^^� CLEARING LIMITS HEALTH DISTRICT RECORDS THERE ARE NO SF SILT FENCE KNOWN EXISTING DRAINFIELDS WfTHIN 100 PL PLASTIC COVERING FEET OF THE SITE. MU MULCH OR STRAW MATTING CONTOUR&FEAMWSNOTE VEG RETAIN NATIVE VEGETATION CONTOURS AND EXISTING STRUCTURES EXISTING FLOW DIRECTION SHOWN BASED ON SNOHOMISH COUNTY SL1� SOIL LOG 1 PDS. SURVEYNOTE. BOUNDARY AND TOPOGRAPHY SHOWN BASED ON A PRELIMINARY SURVEY CREATED BY WESTERN ENGINEERS h SURVEYORS INC. ON 0412016. 0 (425) 356-2700 LAND USE CONSULTANTS CIVIL ENGINEERS o LAND SURVEYORS *** 9740 EVERGREEN WAY * EVERETT * WA * 98204 *** SOIL. AMENDMENT LEGEND R UNDISTURBED SOIL A AMENDED SOIL APPROXIMATELY 21 CUBIC YARDS OF COMPOST FOR AMENDMENT OF 3,836 SF. OF DISTURBED VEGETATED AREA. REFER TO APPENDIX OF STORMWATER DRAINAGE REPORT FOR FULL DETAILS OF AMENDMENT REQUIREMENTS AND/OR OPTIONS FOR OTHER AMENDMENT PROCEDURES. CALL 811 TWO (2) BUSINESS DAYS BEFORE YO U DIG i66900400201 21022 74TH AVENUE W PROJECT# EDMONDS, WA 98026 SWPPP & GRAD17VG PLAN FOR: HARRIS DUPLEX SW 114, SW 114, SEC.20, T.277V, R.04E, W.M. CITY OF EDMONDS, WASMNGTON %WN BY DATE REV. BY DATE PROJECT MANAGER SCALE NAT 06/04/20 XX XXX XX/XX/XX T. SARKELA 1"=20' %WING FILE NAME CHECKED BY F.B. NO, JOB NUMBER SHEET NO. 201868ABASEDWG ras — 20-1868-A 20F4 Harris Duplex APPENDIX B SOIL INFORMATION JOB NO: 20-1868-A Harris Duplex SOIL LOG INFO Soil log investigation was provided by Nathan Thompson, E.T. of WESI on June 10, 2020. Weather: Mostly cloudy with a temperature around 60°F. Soil Log Info: Test Pit 1 (TP 1) 0"-855: TopsoilNegetation 8"-4819: Loose to Medium Dense, Silty -Fine to Medium Grained Sand with Gravel, Yellowish Brown, Moist. (Weathered Advance Outwash) 48"-10': Medium Dense to Dense, Fine to Medium Grained Sand with Gravel, Grayish Brown, Moist. (Advance Outwash) No groundwater was encountered. JOB NO: 20-1868-A 10 Snohomish County Ama, Washington (WA661) Snohomish County Area. Washington (WA661) Map Ales Percent Unit Map Unit Name in of AOI Symbol AOI �5 Alderwood-Urban 0.2 100.0% land complex, 2 to 8 percent slopes Totals for Area of 0.2 100.0% Interest Harris Duplex Snohomish County Area, Washington 5—Alderwood-Urban land complex, 2 to 8 percent slopes Map Unit Setting • National map unit symbol: 2hz9 • Elevation: 50 to 800 feet • Mean annual precipitation: 25 to 60 inches • Mean annual air temperature: 48 to 52 degrees F • Frost -free period: 180 to 220 days • Farmland classification: Not prime farmland Map Unit Composition • Alderwood and similar soils: 60 percent • Urban land: 25 percent • Minor components: 15 percent • Estimates are based on observations, descriptions, and transects of the mapunit. Description of Alderwood Setting • Landform: Till plains • Parent material: Basal till Typical profile • H1 - 0 to 7 inches: gravelly ashy sandy loam • H2 - 7 to 35 inches: very gravelly ashy sandy loam • H3 - 35 to 60 inches: gravelly sandy loam Properties and qualities • Slope: 2 to 8 percent • Depth to restrictive feature: 20 to 40 inches to densic material • Natural drainage class: Moderately well drained • Capacity of the most limiting layer to transmit water (Ksat): Very low to moderately low (0.00 to 0.06 in/hr) • Depth to water table: About 18 to 36 inches • Frequency of flooding: None • Frequency of ponding: None • Available water storage in profile: Low (about 3.0 inches) Interpretive groups • Land capability classification (irrigated): None specified • Land capability classification (nonirrigated): 4s • Hydrologic Soil Group: B • Forage suitability group: Limited Depth Soils (G002XN302WA) • Hydric soil rating: No Minor Components Mckenna • Percent of map unit: 5 percent • Landform: Depressions • Hydric soil rating: Yes Norma, undrained • Percent of map unit: 5 percent JOB NO: 20-1868-A 12 Harris Duplex Landform: Depressions Hydric soil rating: Yes Terric medisaprists, undrained Percent of map unit: 5 percent Landform: Depressions Hydric soil rating: Yes JOB NO: 20-1868-A 13