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19-020 18828 Sound View SFR Drainage Report 2020-02-2018828 Sound View Place Single Family Residence Edmonds, WA 98020 Stormwater Site Plan Report Prepared for: Select Homes Date: February 20, 2020 36508 w GISTEg�'9 2/20/2020 Prepared by: Rob Long, PE RAM Engineering, Inc. 16531 13t" Ave W, Suite A108, Lynnwood WA 98037 (425) 678-6960 RAMengineeringinc.com Job No. 19-020 18828 Sound View Place Single Family Residence Introduction: This summary report provides site design information for a single family residential lot development by Select Homes. This report includes storm drainage analysis to support permit review and approval. The property is located at 18828 Sound View Place, in the southeast 1/4 of Section 13, T 27 N, R 3 E, W.M. Site Address: 18828 Sound View Place Applicant: Select Homes Edmonds, WA 98020 16513 13th Ave W, Suite A108, Lynnwood WA 98037 Tax Parcel Number: 004984 000 002 00 Contact: Kayla Clark Nichols (425) 742-6044 TABLE OF CONTENTS SECTION PAGES A. Project Overview.............................................................................................................................. 4 B. Existing Conditions Summary........................................................................................................... 1 C. Developed Site Hydrology.............................................................................................................. 15 D. Soils Report..................................................................................................................................... 15 E. Construction SWPPPP Requirements................................................................................................ 2 F. Operation and Maintenance Guidelines.......................................................................................... 10 RAMEngineering, Inc. 18828 Sound View Place RAM No. 19-020 Stormwater Site Plan Report A. PROJECT OVERVIEW. This report provides engineering information for the proposed construction of a single-family residence on an 13,274 sf (0.305 ac) lot; the project is located at 18828 Sound View Place in the City of Edmonds. The applicant, Select Homes proposes to remove an existing house and all existing hard surface to construct one single family residence on the project site. This report provides the evaluation for the proposed single family residence development. Summary of Minimum Requirements for Category 2 Project: Minimum Requirement#1—Preparation of StormwaterSite Plan. The proposed site development consists of disturbing about 0.32 acres of land and creating/replacing about 6,095 sf of hard surface area. Thus, the project is classified as a Category 2 project per the City's classification system. Per ECDC 18.30, Category 2 projects must comply with Minimum Requirements No. 1 through No. 9. The civil site development plans and this report have been prepared to address the projects impacts. Minimum Requirement #2 — Construction Stormwater Pollution Prevention (SWPPP). A construction Stormwater Pollution Prevention Plan (SWPPP) has be incorporated into the site development plans. A summary of the site's erosion control measures that evaluates the typical 13 elements of a SWPPP are included in section E. The total site disturbance area of the project is less than one acre, thus a formal Notice of Intent application for NPDES coverage will not be made to the Department of Ecology. Minimum Requirement #3 —Source Control of Pollution. Specific source controls are not required for single family residential sites. General requirements for these sites include preventing the discharge of pollutants to the City's storm drainage system per Edmonds City Code Chapter 7.200 (Illicit Discharges). This includes common household items such as pesticides, herbicides, fertilizers, detergents and fluids from vehicle maintenance. Single family residences shall incorporate DOE's S411 BMPs for landscape and lawn vegetation management. Lawn and vegetation management can include control of objectionable weeds, insects, mold, bacteria, and other pests with pesticides. Examples include weed control on golf course lawns, access roads, and utility corridors and during landscaping; sap stain and insect control on lumber and logs; rooftop moss removal; killing nuisance rodents; fungicide application to patio decks, and residential lawn/plant care. It is possible to release toxic pesticides such as pentachlorophenol, carbamates, and organometallics to the environment by leaching and dripping from treated parts, container leaks, product misuse, and outside storage of pesticide contaminated materials and equipment. Poor management of the vegetation and poor application of pesticides or fertilizers can cause appreciable stormwater contamination. Minimum Requirement #4 — Preservation of Natural Drainage Systems and Outfalls. The site generally slopes in a west/northwesterly. There are no concentrated flows or existing defined conveyance systems located onsite, any site runoff leaves the site as sheet -flow. Per the geotechnical report the underlying soils consists of silty sand transitional bed deposits; thus, it is assumed a majority of the local stormwater RAMEngineering, Inc. RAM No. 19-020 18828 Sound View Place Stormwater Site Plan Report Page A-1 infiltrates and dissipates into the ground. The site is located within the upper reach of the Puget Sound watershed basin per the City of Edmonds maps (see section C). Onsite stormwater BMPs (infiltration trench and Post -Construction Soil Quality and Depth) will be implemented with the site development; these stormwater BMPs will mimic the natural infiltration and dissipation of stormwater into the underlying soils. Minimum Requirement #5—OnsiteStormwaterManagement. Asite-specificgeotechnical evaluation (see section D) of the site demonstrates that an infiltration trench for hard surfaces; and Post -Construction Soil Quality and Depth (BMP T5.13) for pervious surfaces are considered feasible stormwater BMPs for the site development. See civil site development plans and Section Cfor additional stormwater BMP evaluation and construction details. Minimum Requirement#6—Runoff Treatment. The project does not propose to create/replace more than 5,000 sf of pollution -generation impervious surface onsite. The project will create about 1,780 sf pollution generation hard surfaces (driveways); most the site's hard surface is rooftop and walkway/patio areas (non - pollution generation surfaces). Thus, no basic or enhanced water quality treatment system is required. The site's stormwater infiltration system will be proceeded by a catch basin with a sump and a floatable tee that will provide some water quality and oil/water separation of the collected runoff. Minimum Requirement #7— Flow Control. An onsite infiltration trench will provide flow control of the site development's stormwater runoff. The infiltration trench system is designed to fully mitigate the increased hard surfaces and be in full compliance with the LID Standard and full flow control (match flow durations between 8 percent of the 2-year flow through the full 50-year flow). Flow control (storm water infiltration) designs and sizing calculations are provided in Section E of this report. Minimum Requirement #8 — Wetland Protection. No wetlands are known to exist on or adjacent to the site. Minimum Requirement #9 — Operation and Maintenance. An operation and maintenance summary is provided in section H. RAMEngineering, Inc. RAM No. 19-020 18828 Sound View Place Stormwater Site Plan Report Page A-2 Parcel (Vicinity) Map: QUARTER SECtION TOWNSHIP N.W.&L. RFNBE E.W.M. 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RAM No. 19-020 18828 Sound View Place Stormwater Site Plan Report Page A-3 Site Plan: RAMEngineering, Inc. RAM No. 19-020 18828 Sound View Place Stormwater Site Plan Report Page A-4 B. EXISTING CONDITIONS SUMMARY Existing Conditions. The total site consists of about 13,274 sf (0.305 acres) and is currently occupied by an existing single-family residence. The existing house and driveway are surrounded by grass lawn and landscape areas. Access to the site is via Lindsay Place that abuts the southwesterly boundary of the subject site. The site is surrounded by single family residences to the northwest and northeast; and Sound View Place to the southeast (see attached aerial photo). The site is generally slopes in the easterly direction in a range between 2% and 10%. No define drainage courses are found on -site and stormwater runoff would sheet flow in a northwesterly direction the Puget Sound. No stream or wetlands were discovered on or immediately adjacent to the site. Additional discussion of the local drainage basin and downstream path is discussed in Section C of this report. Soils: In accordance with the project's site -specific geotechnical engineering study by Earth Solutions NW, LLC the on -site soils consist of silty sand and sandy silt (USCS: SM and ML) transitional bed deposits. Mapping shows that the subject site is underlain by Olympia gravel (Qog). Full soils description is included in the project's site specific geotechnical engineering study by Earth Solutions NW, LLC. Aerial Photo (City of Edmonds GIS, 2017 photo; includes pre-existing house onsite): a RAMEngineering, Inc. RAM No. 19-020 E Jlr� Lr a ` . � i • � : airrFi ems- i 4 t R Se� 18828 Sound View Place Stormwater Site Plan Report Page B-1 C. DEVELOPED SITE HYDROLOTY. Developed Conditions. The proposed project includes the construction of a single residence and associated driveway and utilities. All existing structures and impervious surface onsite will be removed/replaced with the site development; landscaping and grass lawn around the new residence will stabilize the site upon building construction. The project proposes to create and/or replace 6,095 sf of hard surface with the complete site development, all existing hard surface will be removed with the project site development. The following is a summary of the proposed site areas and the new/replaced hard surface areas: Project Area Summary: Lot Area = Right-of-way Redevelopment Area (driveway aprons) = 13,274 sf 562 sf Total Site Development Area = 13,836 sf (0.318 Ac.) Total Hard Surface Proposed = 6,095 sf (0.140 ac) Building Rooftop = 3,995 sf (0.092 ac) Uncovered Patio and Walk = 320 sf (0.007 ac) Uncovered Driveway = 1,780 sf (0.041 ac) The project proposes to implement full (100%) downspout and hard surface infiltration onsite. The infiltration trench will be sized using the DOE 2012 Western Washington Hydrology Model (WWHM2012) continuous runoff model. The infiltration trench will be in the northwesterly side of the project site. The infiltration trench will be designed for the total development area; the total hard surface created will be 6,095 sf (0.140 ac). The infiltration trench shall be a minimum 12 feet wide, 44 feet long and 3.0 feet deep; filled with 1-%" to 3" washed drain rock (35% voids). A site specific geotechnical evaluation was made to assess the use of infiltration onsite. The evaluation determined infiltration is feasible onsite and recommends a long-term infiltration design rate of 1.2 in/hr. The developed runoff rates and storage calculations were performed using the DOE 2012 Western Washington Hydrology Model (WWHM2012) continuous runoff model. The below calculations demonstrate that the trenches will fully mitigate (100% infiltration) the increased hard surfaces, see WWHM2012 input/printout on the following pages. RAMEngineering, Inc. RAM No. 19-020 18828 Sound View Place Stormwater Site Plan Report Page C-1 WWHM2012 PROJECT REPORT Project Name: 19-020 Trench Site Name: 18828 Soundview Site Address: #19-020 City Report Date: 2/19/2020 MGS Regoin Puget East Data Start 1901/10/1 Data End : 2058/09/30 DOT Data Number: 02 Version Date: 2018/10/10 Version : 4.2.16 Low Flow Threshold for POC 1 : 50 Percent of the 2 Year High Flow Threshold for POC 1: 50 year PREDEVELOPED LAND USE Name : Basin 1 Bypass: No Groundwater: No Pervious Land Use acre A B, Forest, Flat .318 Pervious Total 0.318 Impervious Land Use acre Impervious Total 0 Basin Total 0.318 Element Flows To: Surface Interflow MITIGATED LAND USE Name : Basin 1 Bypass: No Groundwater: No Pervious Land Use acre A B, Pasture, Flat .178 Pervious Total 0.178 Impervious Land Use acre ROOF TOPS FLAT 0.092 DRIVEWAYS FLAT 0.041 SIDEWALKS FLAT 0.007 Impervious Total 0.14 Basin Total 0.318 Groundwater Element Flows To: Surface Interflow Groundwater Gravel Trench Bed 1 Gravel Trench Bed 1 RAM Engineering, Inc. 18828 Sound View Place RAM No. 19-020 Stormwater Site Plan Report Page C-2 Name : Gravel Trench Bed 1 Bottom Length: 44.00 ft. Bottom Width: 12.00 ft. Trench bottom slope 1: 1 To 1 Trench Left side slope 0: 1 To 1 Trench right side slope 2: 1 To 1 Material thickness of first layer: 3 Pour Space of material for first layer: 0.35 Material thickness of second layer: 0 Pour Space of material for second layer: 0 Material thickness of third layer: 0 Pour Space of material for third layer: 0 Infiltration On Infiltration rate: 1.2 Infiltration safety factor: 1 Total Volume Infiltrated (ac-ft.): 52.984 Total Volume Through Riser (ac-ft.): 0 Total Volume Through Facility (ac-ft.): 52.984 Percent Infiltrated: 100 Total Precip Applied to Facility: 0 Total Evap From Facility: 0 Discharge Structure Riser Height: 0 ft. Riser Diameter: 0 in. Element Flows To: Outlet 1 Outlet 2 ;91J fl f Wed i 1:42a -19-020 Trench - Firs Pred RAM Engineering, Inc. RAM No. 19-020 a • Gravel Trench Bed t Mitigated Facility Name Downstream Connection Facility Type r PwcO atica Ap*d to FacW r lEvapotalion Applied to FaaQ Grind Trench Bed 1 Outlet T Outlet 2 Outlet 3 [q�0� �G ravel TremWBed OuickTrench 1 Facility Dimension Diaoram Facility Dimensions Trench Length (RJ Trench Mlom Wrdl)(k) i2 ElNcJ" ToW Depth (k) 0� Top and b ottan slope VSM Lek Side Slope (HM Riled Side 5k nw (HM 0 Material Layers for Trench/8ed L%w 1 Thckrms (a) 0 Lay-1 Pa y (¢7) 0.35 Layer 2 Thiickness (£I) 0 Layer 2 porosity 13-1) Lave 3 Thickness (k) Layer 3 paroslly (0.11 U In,iltration Fe—s --H Oullet Structure Data I Rise H6W (It] Riser Dianxter (n) [0—' fl Riser Type I+ Notch Type Orifice Diameter Height Number (in) (to 1 2 3 FT Trench Volu r al Rim Head (ac-ft) -016 Measued Infihation Rate (i Av) 1.2 Ration Facto lirdi"actor] rl—,a.' Show Trench gpei Table Use Welted Solace Area (sideweAs) Nf] — rood Slage (fl) q Totai Vakme 140pated (ac•fl) 52.984 Tdal Vokme Through Far x52 984 T otel VoMme T hrorrgh R iser(ac111 0 PercerrtlrMiated 1W 18828 Sound View Place Stormwater Site Plan Report Page C-3 Gravel Trench Bed Hydraulic Table Stage(feet) Area(ac.) Volume(ac-ft.) Discharge(cfs) Infilt(cfs) 0.0000 0.012 0.000 0.000 0.000 0.0333 0.012 0.000 0.000 0.014 0.0667 0.012 0.000 0.000 0.014 0.1000 0.012 0.000 0.000 0.014 0.1333 0.012 0.000 0.000 0.014 0.1667 0.012 0.000 0.000 0.014 0.2000 0.012 0.000 0.000 0.014 0.2333 0.012 0.001 0.000 0.014 0.2667 0.012 0.001 0.000 0.014 0.3000 0.012 0.001 0.000 0.014 0.3333 0.013 0.001 0.000 0.014 0.3667 0.013 0.001 0.000 0.014 0.4000 0.013 0.001 0.000 0.014 0.4333 0.013 0.001 0.000 0.014 0.4667 0.013 0.002 0.000 0.014 0.5000 0.013 0.002 0.000 0.014 0.5333 0.013 0.002 0.000 0.014 0.5667 0.013 0.002 0.000 0.014 0.6000 0.013 0.002 0.000 0.014 0.6333 0.013 0.002 0.000 0.014 0.6667 0.013 0.003 0.000 0.014 0.7000 0.014 0.003 0.000 0.014 0.7333 0.014 0.003 0.000 0.014 0.7667 0.014 0.003 0.000 0.014 0.8000 0.014 0.003 0.000 0.014 0.8333 0.014 0.003 0.000 0.014 0.8667 0.014 0.004 0.000 0.014 0.9000 0.014 0.004 0.000 0.014 0.9333 0.014 0.004 0.000 0.014 0.9667 0.014 0.004 0.000 0.014 1.0000 0.014 0.004 0.000 0.014 1.0333 0.014 0.004 0.000 0.014 1.0667 0.015 0.005 0.000 0.014 1.1000 0.015 0.005 0.000 0.014 1.1333 0.015 0.005 0.000 0.014 1.1667 0.015 0.005 0.000 0.014 1.2000 0.015 0.005 0.000 0.014 1.2333 0.015 0.005 0.000 0.014 1.2667 0.015 0.006 0.000 0.014 1.3000 0.015 0.006 0.000 0.014 1.3333 0.015 0.006 0.000 0.014 1.3667 0.015 0.006 0.000 0.014 1.4000 0.015 0.006 0.000 0.014 1.4333 0.016 0.007 0.000 0.014 1.4667 0.016 0.007 0.000 0.014 1.5000 0.016 0.007 0.000 0.014 1.5333 0.016 0.007 0.000 0.014 1.5667 0.016 0.007 0.000 0.014 1.6000 0.016 0.008 0.000 0.014 1.6333 0.016 0.008 0.000 0.014 1.6667 0.016 0.008 0.000 0.014 1.7000 0.016 0.008 0.000 0.014 1.7333 0.016 0.008 0.000 0.014 1.7667 0.017 0.009 0.000 0.014 1.8000 0.017 0.009 0.000 0.014 1.8333 0.017 0.009 0.000 0.014 1.8667 0.017 0.009 0.000 0.014 1.9000 0.017 0.009 0.000 0.014 1.9333 0.017 0.010 0.000 0.014 1.9667 0.017 0.010 0.000 0.014 2.0000 0.017 0.010 0.000 0.014 2.0333 0.017 0.010 0.000 0.014 2.0667 0.017 0.010 0.000 0.014 2.1000 0.017 0.011 0.000 0.014 RAM Engineering, Inc. RAM No. 19-020 18828 Sound View Place Stormwater Site Plan Report Page C-4 2.1333 0.018 0.011 0.000 0.014 2.1667 0.018 0.011 0.000 0.014 2.2000 0.018 0.011 0.000 0.014 2.2333 0.018 0.011 0.000 0.014 2.2667 0.018 0.012 0.000 0.014 2.3000 0.018 0.012 0.000 0.014 2.3333 0.018 0.012 0.000 0.014 2.3667 0.018 0.012 0.000 0.014 2.4000 0.018 0.012 0.000 0.014 2.4333 0.018 0.013 0.000 0.014 2.4667 0.019 0.013 0.000 0.014 2.5000 0.019 0.013 0.000 0.014 2.5333 0.019 0.013 0.000 0.014 2.5667 0.019 0.014 0.000 0.014 2.6000 0.019 0.014 0.000 0.014 2.6333 0.019 0.014 0.000 0.014 2.6667 0.019 0.014 0.000 0.014 2.7000 0.019 0.014 0.000 0.014 2.7333 0.019 0.015 0.000 0.014 2.7667 0.019 0.015 0.000 0.014 2.8000 0.020 0.015 0.000 0.014 2.8333 0.020 0.015 0.000 0.014 2.8667 0.020 0.016 0.000 0.014 2.9000 0.020 0.016 0.000 0.014 2.9333 0.020 0.016 0.000 0.014 2.9667 0.020 0.016 0.000 0.014 3.0000 0.020 0.017 0.000 0.014 ANALYSIS RESULTS Stream Protection Duration Predeveloped Landuse Totals for POC #1 Total Pervious Area:0.318 Total Impervious Area:O Mitigated Landuse Totals for POC #1 Total Pervious Area:0.178 Total Impervious Area:0.14 Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.000159 5 year 0.000211 10 year 0.000241 25 year 0.000252 50 year 0.000253 100 year 0.000255 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0 5 year 0 10 year 0 25 year 0 50 year 0 100 year 0 RAM Engineering, Inc. RAM No. 19-020 18828 Sound View Place Stormwater Site Plan Report Page C-5 N to CumuMve Probability to 9.01 �y Q � O.00t 0.000 t OMEME MEMO 0.5 1 2 5 10 20 30 W 70 90 W 95 98 9999.51 Shorn Protection Dureior. LID Dua6m Flow Frequency I Wale. Rudty I H aphaph Welland lrput Vd.w* I LID Report Reckfarge Dualiare Recha.pe N kveloped I Recharg. Mbgated AnabTe cWasets Compact WDM 1 Delete Seeded j r Man" FF f '1 :f •f - 1000 Gavel Trench Bed 1 ALL OUTLETS M69aferl 1001 Gavel TrffKh Bed 1 OUTLET 1 Mboed 1092 Gavel Trend. Bed 1 OUTLET 2 Migated AU Dalasets Flow Stage P-1p Evap PoC ] Hood Frepxncy M e8wd r' Log Pea.son Type III 17B r Weid r C+sMf" C. Gw9wen Stream Protection Duration Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1902 0.000 0.000 1903 0.000 0.000 1904 0.000 0.000 1905 0.000 0.000 1906 0.000 0.000 1907 0.000 0.000 1908 0.000 0.000 1909 0.000 0.000 1910 0.000 0.000 1911 0.000 0.000 1912 0.000 0.000 1913 0.000 0.000 1914 0.000 0.000 1915 0.000 0.000 1916 0.000 0.000 1917 0.000 0.000 1918 0.000 0.000 1919 0.000 0.000 1920 0.000 0.000 1921 0.000 0.000 1922 0.000 0.000 1923 0.000 0.000 1924 0.000 0.000 1925 0.000 0.000 1926 0.000 0.000 1927 0.000 0.000 1928 0.000 0.000 1929 0.000 0.000 RAM Engineering, Inc. RAM No. 19-020 Flow Frequency n Flow Icfs] 0501 15m 0701 157 0601 15m 2 Year - 0.0002 0.0410 0.0000 5 Year - 0.0002 0.0565 0.0000 10 Year - 0.0002 0.0665 0.0000 25 Year - 0.0003 0.0834 0.0000 50 Year ME 0.0003 0.1001 0.0000 100 Year - 0.0003 0.1226 0.0000 Annnal Peaks 1902 0.0001 0.0495 0.0000 1903 0.0001 0.0540 0.0000 1904 0.0002 0.0592 D.0000 1905 0.0002 0.0294 0.0000 1906 0.0001 0.0309 0.0000 1907 0.0002 0.0386 0.0000 1908 0.00132 0.0353 0.0000 1909 0.0002 0.0453 0.0000 1910 0.0002 0.0386 0.0000 1911 0.0002 0.0467 0.0000 1912 C.0002 0.0769 0.0000 1913 0.0001 0.0303 0.0000 2914 0.0002 0.1229 0.0000 1915 0.0001 0.0276 0.0000 1916 0.0002 0.0528 0.0000 1917 0.0001 0.0257 0.0000 2918 0.0002 0.0419 0.0000 1919 0.0001 0.0251 0.0000 1920 0.0002 0.0335 0.0000 1921 0.0001 0.0274 D.000O 2922 0.0002 0.0402 0.0000 1923 0.0003 0.0330 0.0000 1924 0.0001 0.0584 0.0000 1925 0.0001 0.0261 0.0000 1926 0.0002 0.0534 0.0000 1927 O.00D3 0.0395 0.0000 1928 0.0001 0.0324 0.0000 1929 0.0002 0.0566 0.0000 „ 18828 Sound View Place Stormwater Site Plan Report Page C-6 1930 0.000 0.000 1931 0.000 0.000 1932 0.000 0.000 1933 0.000 0.000 1934 0.000 0.000 1935 0.000 0.000 1936 0.000 0.000 1937 0.000 0.000 1938 0.000 0.000 1939 0.000 0.000 1940 0.000 0.000 1941 0.000 0.000 1942 0.000 0.000 1943 0.000 0.000 1944 0.000 0.000 1945 0.000 0.000 1946 0.000 0.000 1947 0.000 0.000 1948 0.000 0.000 1949 0.000 0.000 1950 0.000 0.000 1951 0.000 0.000 1952 0.000 0.000 1953 0.000 0.000 1954 0.000 0.000 1955 0.000 0.000 1956 0.000 0.000 1957 0.000 0.000 1958 0.000 0.000 1959 0.000 0.000 1960 0.000 0.000 1961 0.000 0.000 1962 0.000 0.000 1963 0.000 0.000 1964 0.000 0.000 1965 0.000 0.000 1966 0.000 0.000 1967 0.000 0.000 1968 0.000 0.000 1969 0.000 0.000 1970 0.000 0.000 1971 0.000 0.000 1972 0.000 0.000 1973 0.000 0.000 1974 0.000 0.000 1975 0.000 0.000 1976 0.000 0.000 1977 0.000 0.000 1978 0.000 0.000 1979 0.000 0.000 1980 0.000 0.000 1981 0.000 0.000 1982 0.000 0.000 1983 0.000 0.000 1984 0.000 0.000 1985 0.000 0.000 1986 0.000 0.000 1987 0.000 0.000 1988 0.000 0.000 1989 0.000 0.000 1990 0.000 0.000 1991 0.000 0.000 1992 0.000 0.000 1993 0.000 0.000 1994 0.000 0.000 1995 0.000 0.000 1996 0.000 0.000 RAMEngineering, Inc. RAM No. 19-020 18828 Sound View Place Stormwater Site Plan Report Page C-7 1997 0.000 0.000 1998 0.000 0.000 1999 0.000 0.000 2000 0.000 0.000 2001 0.000 0.000 2002 0.000 0.000 2003 0.000 0.000 2004 0.000 0.000 2005 0.000 0.000 2006 0.000 0.000 2007 0.000 0.000 2008 0.000 0.000 2009 0.000 0.000 2010 0.000 0.000 2011 0.000 0.000 2012 0.000 0.000 2013 0.000 0.000 2014 0.000 0.000 2015 0.000 0.000 2016 0.000 0.000 2017 0.000 0.000 2018 0.000 0.000 2019 0.000 0.000 2020 0.000 0.000 2021 0.000 0.000 2022 0.000 0.000 2023 0.000 0.000 2024 0.000 0.000 2025 0.000 0.000 2026 0.000 0.000 2027 0.000 0.000 2028 0.000 0.000 2029 0.000 0.000 2030 0.000 0.000 2031 0.000 0.000 2032 0.000 0.000 2033 0.000 0.000 2034 0.000 0.000 2035 0.000 0.000 2036 0.000 0.000 2037 0.000 0.000 2038 0.000 0.000 2039 0.000 0.000 2040 0.000 0.000 2041 0.000 0.000 2042 0.000 0.000 2043 0.000 0.000 2044 0.000 0.000 2045 0.000 0.000 2046 0.000 0.000 2047 0.000 0.000 2048 0.000 0.000 2049 0.000 0.000 2050 0.000 0.000 2051 0.000 0.000 2052 0.000 0.000 2053 0.000 0.000 2054 0.000 0.000 2055 0.000 0.000 2056 0.000 0.000 2057 0.000 0.000 2058 0.000 0.000 Stream Protection Duration Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated RAM Engineering, Inc. RAM No. 19-020 18828 Sound View Place Stormwater Site Plan Report Page C-8 1 0.0003 0.0000 2 0.0003 0.0000 3 0.0003 0.0000 4 0.0003 0.0000 5 0.0003 0.0000 6 0.0003 0.0000 7 0.0003 0.0000 8 0.0003 0.0000 9 0.0003 0.0000 10 0.0003 0.0000 11 0.0002 0.0000 12 0.0002 0.0000 13 0.0002 0.0000 14 0.0002 0.0000 15 0.0002 0.0000 16 0.0002 0.0000 17 0.0002 0.0000 18 0.0002 0.0000 19 0.0002 0.0000 20 0.0002 0.0000 21 0.0002 0.0000 22 0.0002 0.0000 23 0.0002 0.0000 24 0.0002 0.0000 25 0.0002 0.0000 26 0.0002 0.0000 27 0.0002 0.0000 28 0.0002 0.0000 29 0.0002 0.0000 30 0.0002 0.0000 31 0.0002 0.0000 32 0.0002 0.0000 33 0.0002 0.0000 34 0.0002 0.0000 35 0.0002 0.0000 36 0.0002 0.0000 37 0.0002 0.0000 38 0.0002 0.0000 39 0.0002 0.0000 40 0.0002 0.0000 41 0.0002 0.0000 42 0.0002 0.0000 43 0.0002 0.0000 44 0.0002 0.0000 45 0.0002 0.0000 46 0.0002 0.0000 47 0.0002 0.0000 48 0.0002 0.0000 49 0.0002 0.0000 50 0.0002 0.0000 51 0.0002 0.0000 52 0.0002 0.0000 53 0.0002 0.0000 54 0.0002 0.0000 55 0.0002 0.0000 56 0.0002 0.0000 57 0.0002 0.0000 58 0.0002 0.0000 59 0.0002 0.0000 60 0.0002 0.0000 61 0.0002 0.0000 62 0.0002 0.0000 63 0.0002 0.0000 64 0.0002 0.0000 65 0.0002 0.0000 66 0.0002 0.0000 67 0.0002 0.0000 RAMEngineering, Inc. RAM No. 19-020 18828 Sound View Place Stormwater Site Plan Report Page C-9 68 0.0002 0.0000 69 0.0002 0.0000 70 0.0002 0.0000 71 0.0002 0.0000 72 0.0002 0.0000 73 0.0002 0.0000 74 0.0002 0.0000 75 0.0002 0.0000 76 0.0002 0.0000 77 0.0002 0.0000 78 0.0002 0.0000 79 0.0002 0.0000 80 0.0002 0.0000 81 0.0002 0.0000 82 0.0002 0.0000 83 0.0002 0.0000 84 0.0002 0.0000 85 0.0002 0.0000 86 0.0002 0.0000 87 0.0002 0.0000 88 0.0002 0.0000 89 0.0002 0.0000 90 0.0001 0.0000 91 0.0001 0.0000 92 0.0001 0.0000 93 0.0001 0.0000 94 0.0001 0.0000 95 0.0001 0.0000 96 0.0001 0.0000 97 0.0001 0.0000 98 0.0001 0.0000 99 0.0001 0.0000 100 0.0001 0.0000 101 0.0001 0.0000 102 0.0001 0.0000 103 0.0001 0.0000 104 0.0001 0.0000 105 0.0001 0.0000 106 0.0001 0.0000 107 0.0001 0.0000 108 0.0001 0.0000 109 0.0001 0.0000 110 0.0001 0.0000 111 0.0001 0.0000 112 0.0001 0.0000 113 0.0001 0.0000 114 0.0001 0.0000 115 0.0001 0.0000 116 0.0001 0.0000 117 0.0001 0.0000 118 0.0001 0.0000 119 0.0001 0.0000 120 0.0001 0.0000 121 0.0001 0.0000 122 0.0001 0.0000 123 0.0001 0.0000 124 0.0001 0.0000 125 0.0001 0.0000 126 0.0001 0.0000 127 0.0001 0.0000 128 0.0001 0.0000 129 0.0001 0.0000 130 0.0001 0.0000 131 0.0001 0.0000 132 0.0001 0.0000 133 0.0001 0.0000 134 0.0001 0.0000 RAMEngineering, Inc. RAM No. 19-020 18828 Sound View Place Stormwater Site Plan Report Page C-10 135 0.0001 0.0000 136 0.0001 0.0000 137 0.0001 0.0000 138 0.0001 0.0000 139 0.0001 0.0000 140 0.0001 0.0000 141 0.0001 0.0000 142 0.0001 0.0000 143 0.0001 0.0000 144 0.0001 0.0000 145 0.0001 0.0000 146 0.0001 0.0000 147 0.0001 0.0000 148 0.0001 0.0000 149 0.0001 0.0000 150 0.0001 0.0000 151 0.0001 0.0000 152 0.0001 0.0000 153 0.0001 0.0000 154 0.0001 0.0000 155 0.0001 0.0000 156 0.0000 0.0000 157 0.0000 0.0000 Stream Protection Duration POC #1 The Facility PASSED U J - ar r rug, r nwevvrrrpw 80i POC 1 Mrtgeted flow W 10E-4 1 CE-3 10E -2 10E-1 1 10 100 PsrcQnt Timms Exc¢�din y� Stream Protection D-ati6n I LJD Dua6- I Fhw Frequency J Water Analyze datasets E F_ Mw" FF ompacr WDM f Deleie Selected r •r :r •r Al1099.9 Datasets I Flow j Stage I I mcip I Evap POC 1 F od Frequency N1e+hod r Lag Pearson Type III 178 r Webd r ownane r: Grigaten RAM Engineering, Inc. RAM No. 19-020 Facility PASSED Plow[cia] Predev Hit Percentage Pass/Fail 1.0001 4595 0 0 Pass D.0001 4407 0 0 Pass 0.0001 4226 0 0 Pass D.0001 4125 0 0 Pass 0.0001 3972 0 0 Pass D.0001 3820 0 0 Pass D.0001 3950 0 0 Pass D.0001 3568 0 0 Pass D.0001 3403 0 0 Pass 0.0001 3272 0 0 Pass D.0001 3108 0 ❑ Pass D.0001 3023 0 ❑ Pass D.0001 2917 0 0 Pass D.0001 2793 0 0 Paaa D.0001 2E97 0 0 Pass D.0001 2951 0 0 Pass D.0001 2551 0 ❑ Pass D.0001 2460 ❑ 0 Pass D.0001 2364 0 0 Pa.a D.0001 2305 0 0 Pass D.0001 2227 0 ❑ Pass D.0001 2119 0 0 Pass D.0001 2039 0 0 Pass D.0001 1992 0 0 Pass D.0001 1901 0 ❑ Pass D.0001 1810 0 0 Pass D.0001 1734 0 0 Pass D.0001 IC90 0 0 Pass D.0001 1599 0 ❑ Pass D.0001 1509 0 0 Paas D.0001 1106 0 0 Pas: D.0001 1362 ❑ 0 Pa as D.0001 1307 0 0 Pass 0.0001 1232 0 0 Pass 18828 Sound View Place Stormwater Site Plan Report Page C-11 O v cD Z m N O �77 CD a O W 00 N co co O C (D ZE v m 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 o n] 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 o S N N O W O� O N U1 J Ol N W l0 � W Ol J W r` O r` J r` O� O� � W VI O Ol Ol F-` l0 J F� l0 O Ol O Ol W W O 61 O O l0 l0 W F' O lD W F' N O Ol Ol U1 (I1 l0 l0 r' N O J O 61 U1 N J N N O lD (D l0 F' N N N N J N 61 lD lD O �P O F' N l0 l0 J Ut �p O F' F' J W J W W N W W O O N N 6l J N Q. C r rt ro m rt m p rt a w ro ro ro ro ro ro ro ro ro ro ro ro ro ro ro ro Id Id Id Id Id Id ro ro ro ro ro ro ro ro ro ro ro ro ro ro ro ro ro ro ro ro ro ro ro ro ro ro ro ro ro ro ro ro ro ro ro ro b b b b b b b ro ro ro ro ro ro ro ro m a a a a w w w w w w a w w w w a a a a a a a a a a a a a w w w w w w w w w w w w w a a a a a a a a a a a a w w w w w w a a a a a a a a a a a a a a a ro Ul Ul Ul Ul Ui (11 N N N N V1 � � � U1 V1 N N N N N N N Ul Ul Ul Ul Ul Ui U1 U1 U1 U1 U1 U1 V1 V1 V1 U� U1 V1 f/1 f/1 f/1 f/1 f/1 U1 Ul Ul Ul Ul Ul Ul Ui Ui U1 U1 U1 U1 V1 V1 V1 V1 V1 V1 V1 f/1 f/1 f/1 f/1 f/1 U1 Ul Ul w N N N N Ul Ul Vl Vl Vl Vl [0 N N N N N N N N N N N N N N N N N Ul Vl Vl Vl Vl Vl Vl [0 N N N N N N N N N N N N N N N N N Ul Ul Vl Vl Vl Vl [0 N N N N N N N N N N N N N N N Ul a F' 0.0002 214 0 0 Pass 0.0002 211 0 0 Pass 0.0002 189 0 0 Pass 0.0002 187 0 0 Pass 0.0002 183 0 0 Pass 0.0002 174 0 0 Pass 0.0002 163 0 0 Pass 0.0002 154 0 0 Pass 0.0002 128 0 0 Pass 0.0002 127 0 0 Pass 0.0002 122 0 0 Pass 0.0002 116 0 0 Pass 0.0002 106 0 0 Pass 0.0002 99 0 0 Pass 0.0002 95 0 0 Pass 0.0002 86 0 0 Pass 0.0002 76 0 0 Pass 0.0002 72 0 0 Pass 0.0002 57 0 0 Pass 0.0002 53 0 0 Pass 0.0002 98 0 0 Pass 0.0002 96 0 0 Pass 0.0002 31 0 0 Pass 0.0002 26 0 0 Pass 0.0003 17 0 0 Pass 0.0003 9 0 0 Pass Water Quality BMP Flow and Volume for POC #1 On-line facility volume: 0 acre-feet On-line facility target flow: 0 cfs. Adjusted for 15 min: 0 cfs. Off-line facility target flow: 0 cfs. Adjusted for 15 min: 0 cfs. LID Report MOW ... LID Techruque Used for Total Volume Volume Infiltration Cumulative Percent Water Quality Percent Comment Treatment I Needs Through Volume VQlume Volume Water Quality Treatment Facility (ac-R) Infiltration infiltrated Treated (ac-fE) (ac-tt) Credit Gravel Trench Bed 1 POC 0 48.22 Q 100.00 Total Volume Infiltrated 48.22 0.00 000 100.00 0.00 0% No Treat. Credit Compliance with LID Duration Analysis Standard 8% of 2-yr to 50% of Result = 2 yr I Passed Perind and Impind Changes No changes have been made. This program and accompanying documentation is provided 'as -is' without warranty of any kind. The entire risk regarding the performance and results of this program is assumed by the user. Clear Creek Solutions, Inc. disclaims all warranties, either expressed or implied, including but not limited to implied warranties of program and accompanying documentation. In no event shall Clear Creek Solutions, Inc. be liable for any damages whatsoever (including without limitation to damages for loss of business profits, loss of business information, business interruption, and the like) arising out of the use of, or inability to use this program even if Clear Creek Solutions, Inc. has been advised of the possibility of such damages. RAM Engineering, Inc. RAM No. 19-020 18828 Sound View Place Stormwater Site Plan Report Page C-13 Offsite Analysis. The site is located within the City of Edmonds' "Puget Sound" watershed basin. The Puget Sound basin consists of properties that discharge directly to the Puget Sound and not to a creek system. Runoff flows typically sheet flow in a westerly direction towards the Puget Sound (see attached watershed map). Runoff from the site sheet -flows in a northwest/westerly direction towards the Puget Sound. The subject property is only one parcel off the shoreline of the Puget Sound. It appears a majority of the stormwater infiltrates into the existing soils. An infiltration trench system is proposed to be installed with the site development; an infiltration trench system would mimic the existing natural infiltration of any stormwater surface runoff. See the below downstream drainage facility map and watershed map for the local downstream path. Downstream Drainage Facility Map (City of Edmonds GIS) 1IC980 +SS SITE o .18816 76, 4 no^�� 18824 r�110y 18902 �Q r 189 4 !r: 8 g fi 7190 � 18912 18910 o 7883r 1 q°~ " 18922 18922Ln ~ - 189.1i'^- a a rn 9630 CO CO 18929 B 1KE PL RAMEngineering, Inc. RAM No. 19-020 18828 Sound View Place Stormwater Site Plan Report Page C-14 Watershed Basin Map CI6-1 cETY OF EDnnolvDs WATERSHEDS Deer Creek _ Pprnrwle Edmonds Math - PY" Sound Edmonds Way - PLWK S—d fhped .' FftdbWe - Shd Geek Gaol Hope pond - ShWharRer HMk Leek - Sofit e l Ed—ds A - HYMey [reek Smat- l Fcmonds F Lake Faro nyer sukha Leek lur,d'a GA ©'] bboa PwkA M-6-MA le A TAbN Park 6 MeadowdaltF Tema Creak Nonhsueam wovAm Pofd OurfaF Edeek WAkwCfaA o kDw 2-= A= firm Um l a. 1" ft I�nL- 118828 Soundview Pf} A \`44s Sound Plfakd ti N A Rt } ,1 —I hfrado.vda 5r A-•� i +�Iowdalo 0 - y i Uu! �u Cn�SCliisoufe GeQ� ierracv [.evk � vrkx. fal6�s Pxk S � 'ih'� \-kidale I-ce' -I hsiream NrndJGy ��: -•JY� Good Hope Ports rr�r fel iL EdreWndi Ml�yi j '°�'�'• •" yhei! Crnek •ilinx iw Shfl..oa.acr- 5 �. ,. - il4 s _•W-taxe Pam walk [reek I, b ~ Wdlgv cleel, L i t s i usausw � ``-1 f It .-,--_ II r- -� Edmonds Way II:�� SIs hwesr Ed mond s8 �• .._• RAM Engineering, Inc. RAM No. 19-020 18828 Sound View Place Stormwater Site Plan Report Page C-15 D. SOILS REPORT. Geotechnical Evaluation Letter Prepared by: Earth Solutions NW, LLC Date: October 9, 2019 Pages: 14 RAM =ngineering, Inc. RAM No. 19-020 18828 Sound View Place Stormwater Site Plan Report Page D-1 October 9, 2019 ES-6934 Select Homes, Inc. 16531 — 13th Avenue West, A107 Lynnwood, Washington 98037 Attention: Ms. Kayla Nichols Subject: Geotechnical Evaluation Proposed Single -Family Residence 18828 Soundview Place Edmonds, Washington Earth t Solutions NW«C Earth Solutions NW LLC Geotechnical Engineering, Construction Observation/Testing and Environmental Services Reference: Department of Ecology Stormwater Management Manual for Western Washington Amended December 2014 James P. Minard Geologic Map of the Edmonds East and Washington, 1983 Part of the Edmonds West Quadrangles Edmonds City Code Chapter 23.80 (Geologically Hazard Areas) Dear Ms. Nichols: As requested, Earth Solutions NW, LLC (ESNW) has prepared this geotechnical evaluation report for the proposed single-family residence. As part of our scope of services, we completed a subsurface exploration, laboratory and engineering analyses, in -situ infiltration testing, and prepared this written report with our findings and recommendations for the proposed project. Based on our evaluation, the proposed project is feasible from a geotechnical standpoint. Project Description The subject site is located at 18828 Soundview Place in Edmonds, Washington, as illustrated on the Vicinity Map (Plate 1). The site consists of one residential tax parcel (Snohomish County parcel number 00498400000200) totaling approximately 0.30 acres of land. The property is currently developed with a single-family residence and associated improvements. The subject site descends towards the west with total elevation change on the order of 15 feet or less. The subject site is bordered to the north and west by single-family residences, to the south by Lindsay Place, and to the east by Soundview Place. 15365 N.E. 90th Street, Suite 100 0 Redmond, WA 98052 • (425) 449-4704 • FAX (425) 449-4711 Select Homes, Inc. ES-6934 October 9, 2019 Page 2 We understand the existing single-family residential structure and associated improvements will be demolished and a new single-family residential structure will be constructed. We anticipate grading activities will include cuts and fills of about two to four feet to establish the planned building alignment. However, grading plans were not available at the time this report was prepared. We understand infiltration and low impact development methods are being evaluated for stormwater management. Site improvements will also include underground utility installations. At the time this report was prepared, specific building load values were not available. However, we anticipate the proposed residential structures will consist of relatively lightly loaded wood framing supported on conventional foundations. Based on our experience with similar developments, we estimate wall loads on the order of one to two kips per linear foot and slab -on - grade loading of 150 pounds per square foot (psf). If the above design assumptions are incorrect or change, ESNW should be contacted to review the recommendations in this report. ESNW should review the final design to verify the geotechnical recommendations provided in this report have been incorporated into the plans. Subsurface Conditions As part of this geotechnical evaluation, an ESNW representative observed, logged, and sampled three test pits on September 6, 2019, excavated at accessible locations within the proposed development area, using a mini-trackhoe and operator provided by the client. The approximate locations of the test pits are depicted on the Test Pit Location Plan (Plate 2). Please refer to the test pit logs provided as an attachment to this report for a more detailed description of subsurface conditions. Representative soil samples collected at the test pit locations were analyzed in general accordance with the Unified Soil Classification System (USCS) and United States Department of Agriculture (USDA) methods and procedures. Topsoil and Fill Native topsoil was observed extending to depths of approximately four to eight inches below existing ground surface (bgs). The topsoil was characterized by dark brown color and fine organic material. Fill deposits were not encountered at the test pit locations during our fieldwork. Fill may be present, however, within proximity to existing structural improvements. Where fill is encountered during construction, ESNW should be consulted to evaluate the suitability for support of the proposed structures and/or reuse as structural fill. Native Soil Underlying the topsoil, soil conditions near -surface at the test pit locations were observed to primarily consist of silty sand and sandy silt (USCS: SM and ML) transitional bed deposits. Underlying a relatively thin transitional bed "cap", the native soils transitioned to poorly graded sand with silt (USCS: SP-SM) Olympia gravel deposits. The native soil deposits were generally observed to be in a medium dense condition beginning at depths of approximately two to three feet bgs. Overall soil relative density increased with depth, extending to the maximum exploration depth of about eight feet bgs. Earth Solutions NW, LLC Select Homes, Inc. October 9, 2019 Geologic Setting ES-6934 Page 3 The referenced geologic map resource identifies the site is underlain by Olympia gravel (Qog) with Whidbey formation and transitional beds (Qw and Qtb, respectively) mapped immediately adjacent to the subject site. The Olympia gravel consists of stratified fluvial sands and gravels. The Whidbey Formation deposits typically consists of cross bedded sand, very compact, medium - to coarse -grained, and commonly oxidized. Transitional beds are largely clay, silt, and very fine to fine sand, which were deposited in still or slowly moving water. Additionally, the referenced WSS resource identifies Everett very gravelly sandy loam (Map Unit Symbols: 18) within the proposed development area. The Everett series was formed in moraines, kames, and eskers. The gravelly sand soils are generally associated with Olympia gravels underlying a transitional bed "cap". Groundwater Groundwater seepage was not observed at the test pit locations during the fieldwork (September 2019). However, seepage should be expected in deeper excavations at this site, particularly during the winter, spring, and early summer months. Groundwater seepage rates and elevations fluctuate depending on many factors, including precipitation duration and intensity, the time of year, and soil conditions. Geologically Hazardous Areas Assessment As part of this geotechnical evaluation, the referenced chapter of the Edmonds City Code was reviewed. Based on our investigation and review, there are no geologically hazardous areas present on or adjacent to the site. Foundations The proposed single-family structure can be supported on conventional spread and continuous footings bearing on undisturbed, competent native soil, compacted native soil, or new structural fill. Competent native soils, suitable for support of the foundation, should be encountered beginning at depths of approximately two to three feet bgs. Where loose or unsuitable soil conditions are encountered at foundation subgrade elevations during site preparation activities, compaction of the soils to the specifications of structural fill, or overexcavation and replacement with granular structural fill will be necessary. Structural fill should consist of suitable granular soils compacted to 95 percent of Modified Proctor (ASTM D1557). Compaction of the soil to the levels necessary for use as structural fill will be difficult during wet weather conditions. Organic material exposed at foundation subgrade elevations must be removed and grades restored with structural fill. Earth Solutions NW, LLC Select Homes, Inc. ES-6934 October 9, 2019 Page 4 Provided the structure will be supported as described above, the following parameters can be used for design of the new foundations: a Allowable soil bearing capacity 2,500 psf • Passive earth pressure 300 pcf (equivalent fluid) ID Coefficient of friction 0.40 The passive earth pressure and coefficient of friction values included a safety factor of 1.5. A one-third increase in the allowable soil bearing capacity can be assumed for short-term wind and seismic loading conditions. With structural loading as expected, total settlement in the range of one inch is anticipated, with differential settlement of about one-half inch. The majority of the settlements should occur during construction, as dead loads are applied. Seismic Considerations The 2015 IBC recognizes ASCE for seismic site class definitions. In accordance with Table 20.3- 1 of ASCE, Minimum Design Loads for Buildings and Other Structures, Site Class D, should be used for design. In our opinion, the site susceptibility to liquefaction is low. The native soil relative density and the absence of an established, shallow groundwater table are the primary bases for this opinion. Drainage Temporary measures to control surface water runoff during construction would likely involve passive elements such as interceptor trenches and sumps. ESNW should be consulted during preliminary grading activities to evaluate seepage areas and provide recommendations to reduce the potential for seepage -related instability. Finish grades should be designed to direct surface water away from structures and slopes. Grades adjacent to buildings should be sloped away at a gradient of either at least 2 percent for a horizontal distance of up to 10 feet or the maximum allowed by adjacent structures. In our opinion, foundation drains should be installed along building perimeter footings. Infiltration Evaluation As indicated in the Subsurface Conditions section, native soils encountered during our fieldwork were characterized primarily as silty sand and sandy silt underlain by poorly graded sand with silt. Based on the results of USDA textural analyses, the native sand soils were classified primarily as gravelly sand with fines contents of about 6 to 12 percent. Earth Solutions NW, LLC Select Homes, Inc. October 9, 2019 In -situ testing was completed in accordance with the procedure, as outlined in Volume III, Chapter 3, Page was completed at a depth of approximately four feet a ES-6934 Page 5 t Because the infiltration rate obtained from in -situ testing is considered to be a short-term rate, correction factors must be applied in order to determine a long-term design rate. The correction factors outlined below were used in accordance with Table III-3.3.1 of the 2014 SMMWW outlined in Volume III, Chapter 3, Page 529. The correction factors, along with the measured infiltration rate, were incorporated into the following equation: Ksar design = Ksar initial x CFv x CFr x CFn,. • Measured (Ksat initial) 3.0 inches per hour • Site variability CFv = 0.9 • Test method CFt = 0.5 • Degree of influent control CFm = 0.9 ■ Long-term design infiltration rate (Ksat design) 1.2 inches per hour The design infiltration rate is applicable to facilities located in proximity to the infiltration test location and at a depth that may infiltrate into the native sand soil at depth. ESNW should be retained to observe the construction of infiltration facilities on the subject site in order to confirm soil conditions are as anticipated and perform confirmation infiltration testing at the infiltration design depth and location. Overexcavation of low permeability lenses may be required. Supplementary geotechnical recommendations may be provided at the time of construction, where necessary. On -site Stormwater Mana ement Pursuant to City of Edmonds stormwater management requirements, implementation of on -site storrnwater BMPs are required for proposed developments in accordance with specified thresholds, standards, and lists. The intent of BMP implementation is to infiltrate, disperse, and retain stormwater runoff on site to the extent feasible. The table below summarizes our evaluation of low impact development methods, as outlined in the referenced stormwater manual, from a geotechnical standpoint. It is instructed in the referenced stormwater manual that BMPs are to be considered in the order listed (from top to bottom) for each surface type, and the first BMP that is determined to be viable should be used. For completeness, however, we have evaluated each listed BMP for the proposed surface types. Earth Solutions NW, LLC Select Homes, Inc. October 9, 2019 BMP I i Viable? Limitations r Infeasibility Onterria Lawns and Landscaped Areas T5.13: Post -construction soil quality and depth (Volume V, Yes None. Chapter 5) Roofs T5.30: Full dispersion (Volume Maybe* V, Chapter 5) T5.10A: Downspout full infiltration systems (Volume III, Yes Chapter 3) Bioretention (Volume V, Chapter Yes 7) T5.10B: Downspout dispersion systems (Volume III, Chapter 3) T5.10C: Perforated stub -out connections (Volume III, Chapter T5.30: Full dispersion (Volume V, Chapter 5) T5.15: Permeable pavement (Volume V, Chapter 5) Bioretention (Volume V, Chapter 7) T5.12: Sheet flow dispersion T5.11: Concentrated flow dispersion (Volume V, Chapter 5) ES-6934 Page 6 T5.30: Adequate vegetative flow paths will likely not be available. T5.10A: Infiltration should be targeted within the native sand at depth. Infiltration should be targeted within the native sand at depth. Maybe* ' Adequate vegetative flow paths are likely not available. Yes I None. Maybe* I Adequate vegetative flow paths are likely not available. Yes IInfiltration should be targeted within the native sand at depth. Yes IInfiltration should be targeted within the native sand at depth. Maybe* Adequate vegetative flow paths are likely not available. * Viability to be determined by storm designer. 1 imitatinnc The recommendations and conclusions provided in this geotechnical evaluation report are professional opinions consistent with the level of care and skill that is typical of other members in the profession currently practicing under similar conditions in this area. A warranty is not expressed or implied. Variations in the soil and groundwater conditions observed at the test pit locations may exist and may not become evident until construction. ESNW should reevaluate the conclusions in this geotechnical evaluation report if variations are encountered. Earth Solutions NW, LLC Select Homes, Inc. October 9, 2019 ES-6934 Page 7 Should you require additional information, or have questions, please call. Sincerely, EARTH SOLUTIONS NW, LLC Adam Z. Shier, L.G. Senior Staff Geologist Attachments: Plate 1 — Vicinity Map Plate 2 — Test Pit Location Plan Test Pit Logs Grain Size Distribution Henry T. Wright, P.E. Senior Project Manager cc: RAM Engineering, Inc. Attention: Mr. Rob Long, P.E. (Email only) Earth Solutions NW, LLC Reference: NORTH Snohomish County, Washington Map 454 By The Thomas Guide Rand McNally 32nd Edition 40 NOTE: This plate may contain areas of color. ESNW cannot be responsible for any subsequent misinterpretation of the information resulting from black & white reproductions of this plate. Drwn. CAM Date 10/02/2019 Proj. No. 6934 Checked AZS Date Oct. 2019 Plate 1 I I 1 I TP-1 ` 50 i O / -so /House / TP-2`� ' TP-3 0 \� O LEGEND NORTH TP-1 Approximate Location of — ■ — ESNW Test Pit, Proj. No. ES-6934, Sept. 2019 Subject Site Existing Building 0-0-- Existing Rockery NOTE: The graphics shown on this plate are not intended for design purposes or precise scale measurements, but only to illustrate the approximate test locations relative to the approximate locations of existing and / or proposed site features. The information illustrated is largely based on data provided by the client at the time of our study. ESNW cannot be responsible for subsequent design changes or interpretation of the data by others. 20 40 80 1 "=40' � Scale in Feet Test Pit Location Plan Soundview Place SFR Edmonds, Washington NOTE: This plate may contain areas of color. ESNW cannot be Drwn. CAM Date 10/02/2019 Proj. No. 6934 responsible for any subsequent misinterpretation of the information resulting from black & white reproductions of this plate. Checked AZS Date Oct. 2019 Plate 2 Earth Solutions NWLLC SOIL CLASSIFICATION CHART MAJOR DIVISIONS SYMBOLS TYPICAL DESCRIPTIONS GRAPH LETTER GRAVEL AND CLEAN GRAVELS ' �' ' `� • * .0 ■� GW WELL -GRADED GRAVELS, GRAVEL - SAND MIXTURES, LITTLE OR NO FINES -o paQ Q Q np GP GRAVEL- SAND MIXTURES, LITTLE OR NO FINES GRAVELLY COARSE GRAINED SOILS MORE THAN 50% OF COARSE GRAVELS WITH FINES ' Q ° �° ° D a GM SILTY GRAVELS, GRAVEL -SAND - SILT MIXTURES FRACTION GC CLAYEY GRAVELS, GRAVEL - SAND - CLAY MIXTURES RETAINED ON NO. 4 SIEVE (APPRECIABLE AMOUNT OF FINES) SAND AND CLEAN SANDS SW WELL -GRADED SANDS, GRAVELLY SANDS, LITTLE OR NO FINES MORE THAN 50% OF MATERIAL IS SP POORLY -GRADED SANDS, GRAVELLY SAND, LITTLE OR NO FINES LARGER THAN NO. 200 SIEVE SIZE SANDY SOILS (LITTLE OR NO FINES) SANDS WITH FINES SM SILTY SANDS, SAND - SILT MIXTURES MORE THAN 50% OF COARSE FRACTION S`+ CLAYEY SANDS, SAND - CLAY MIXTURES PASSING ON NO. 4 SIEVE (APPRECIABLE AMOUNT OF FINES) INORGANIC SILTS AND VERY FINE ML SANDS, ROCK FLOUR, SILTY OR CLAYEY FINE SANDS OR CLAYEY SILTS WITH SLIGHT PLASTICITY FINE GRAINED SOILS SILTS LIQUID LIMIT AND LESS THAN 50 CLAYS CL INORGANIC CLAYS OF LOW TO MEDIUM PLASTICITY, GRAVELLY CLAYS, SANDY CLAYS, SILTY CLAYS, LEAN CLAYS -u OL ORGANIC SILTS AND ORGANIC SILTY CLAYS OF LOW PLASTICITY MORE THAN 50% OF MATERIAL IS MH INORGANIC SILTS, MICACEOUS OR DIATOMACEOUS FINE SAND OR SMALLER THAN NO.200 SIEVE SILTY SOILS SIZE SILTS LIQUID LIMIT AND CLAYS GREATER THAN 50 CH INORGANIC CLAYS OF HIGH PLASTICITY OH ORGANIC CLAYS OF MEDIUM TO HIGH PLASTICITY. ORGANIC SILTS HIGHLY ORGANIC SOILS T' ' ' ' ' ' PT PEAT, HUMUS, SWAMP SOILS WITH HIGH ORGANIC CONTENTS DUAL SYMBOLS are used to indicate borderline soil classifications. The discussion in the text of this report is necessary for a proper understanding of the nature of the material presented in the attached logs. Earth Solutions NW TEST PIT NUMBER TP-1 15365 N.E. 90th Street, Suite 100 Redmond, Washington 98052 PAGE 1 OF 1 Telephone: 425-449-4704 Fax: 425-449-4711 PROJECT NUMBER ES-6934 PROJECT NAME Soundview Place SFR DATE STARTED 9/5/19 COMPLETED 9/5/19 GROUND ELEVATION TEST PIT SIZE EXCAVATION CONTRACTOR Client -Provided GROUND WATER LEVELS: EXCAVATION METHOD AT TIME OF EXCAVATION --- LOGGED BY AZS CHECKED BY HTW AT END OF EXCAVATION --- NOTES Depth of Topsoil & Sod 8": grass AFTER EXCAVATION - - w _ �w _ wCO 0_O MATERIAL DESCRIPTION 0 n Q Z (� 0 TPSL= r. Dark brown TOPSOIL -roots Brown poorly graded SAND with silt and gravel, loose to medium dense, moist SP- SM MC = 3.40% Fines = 7.70% -infiltration test at 4', becomes gray [USDA Classification: gravelly SAND] 5 MC = 25.40% 6.0 Gray sandy SILT, dense, moist to wet Fines = 60.50% [USDA Classification: slightly gravelly LOAM] MC = 12.00% ML -iron oxide staining 7.5 MC = 21.80% SP- : 8,0 Gray poorly graded SAND with silt, medium dense, wet Fines = 5.70% ` SM [USDA Classification, slightly gravelly SAND] r Test pit terminated at 8.0 feet below existing grade. No groundwater encountered during excavation. No caving observed. Bottom of test pit at 8.0 feet. Earth Solutions NW TEST PIT NUMBER TP-2 15365 N.E. 90th Street, Suite 100 Redmond, Washington 98052 PAGE 1 OF 1 Telephone: 425-449-4704 Fax: 425-449-4711 PROJECT NUMBER E"934 PROJECT NAME Soundview Place SFR DATE STARTED 9/5/19 COMPLETED 9/5/19 GROUND ELEVATION TEST PIT SIZE EXCAVATION CONTRACTOR Client -Provided GROUND WATER LEVELS: EXCAVATION METHOD AT TIME OF EXCAVATION - - LOGGED BY AZS CHECKED BY HTW AT END OF EXCAVATION NOTES _Depth of Topsoil &Sod 6": grass AFTER EXCAVATION --- w _ a Hof W � U a W CO M TESTS U fn a 0 MATERIAL DESCRIPTION Q" a= Q Z �J (7 'TPSL • .'..' 0 5 Dark brown TOPSOIL Gray silty SAND with gravel, dense, moist MC = 3.30% SM :'• -moderately cemented 2.5 Brown silty SAND, medium dense, moist MC = 7.10% SM - a.0 Gray poorly graded SAND with silt, medium dense, moist 5 MC = 5.90% S P- SM MC = 9.30% Test pit terminated at 7.0 feet below existing grade. No groundwater encountered during excavation. No caving observed. Bottom of test pit at 7.0 feet. Earth Solutions NW TEST PIT NUMBER TP-3 15365 N.E. 90th Street, Suite 100 Redmond, Washington 98052Wo �n PAGE 1 OF 1 Telephone: 425-449-4704 Fax: 425-449-4711 PROJECT NUMBER ES-6934 PROJECT NAME Soundview Place SFR DATE STARTED _ 9/5/19 COMPLETED 9/5/19 GROUND ELEVATION _ TEST PIT SIZE EXCAVATION CONTRACTOR Client -Provided GROUND WATER LEVELS: EXCAVATION METHOD AT TIME OF EXCAVATION --- LOGGED BY AZS CHECKED BY HTW AT END OF EXCAVATION --- NOTES Depth of Topsoil & Sod 4": grass AFTER EXCAVATION --- w a- }W U � J g TESTS 2 O MATERIAL DESCRIPTION w � �z � 0 TPSL.` .: `. 10.4 Dark brown TOPSOIL Gray silty SAND with gravel, dense, moist MC = 4.10% SM ;'• -weakly cemented 3.0 Brown sandy SILT, medium dense, moist to wet MC = 21.00% ML 5 5.5 Gray poorly graded SAND with silt, medium dense, moist MC = 9.60% Fines = 11.70% Sp - [USDA Classification: slightly gravelly SAND] SM MC = 7.50% 7 .5 Test pit terminated at 7.5 feet below existing grade. No groundwater encountered during excavation. No caving observed. Bottom of test pit at 7.5 feet. Dui 1 v UIIUIIJ INVV 1805 - 136th Place N.E., Suite 201 woMrs Bellevue, Washington 98005 Telephone: 425-44 9-4704 Fax: 425-449-4711 GRAIN SIZE DISTRIBUTION 1 PROJECT NUMBER ES-6934 PROJECT NAME Soundview Place SFR U.S. SIEVE OPENING IN INCHES I ll S C�F�iF nII 1nnc�oc H 2 9 Lu } co X w Z i Z L Y u L s1 ' UL U 1 0.001 GRAIN SIZE IN MILLIMETERS + COBBLES GRAVEL SAND coarse fine coarse medium fine SILT OR CLAY Specimen Identification • TP-01 4.00ft. Classification USDA: Brown Gravelly Sand. USCS: SP-SM with Gravel. Cc Cu m TP-01 6.00ft. • USDA: Gray Slightly Gravelly Loam. USCS: Sandy ML. 1.44 4. 98 TP-01 8.00ft. USDA: Gray Slightly Gravelly Sand. USCS: Sp-SM. USDA: Gray Slightly Gravelly Sand. USCS: SP-SM. 1.39 5.13 Specimen Identification D100 D60 D30 D10 0 TP-01 4.0ft. 37.5 LL PL PI /°Silt 0.508 0.274 0.102 ° °/OClay 2 TP-01 6.Oft. 4.75 7.7 TP-01 8.Oft. 9.5 0.36 0209.0.105 60.5 TP-03 6.Oft. 9.5 0.344 0.18 5.7 11.7 E. CONSTRUCTION SWPPP REQUIREMENTS: The project will require grading to construct the proposed building and utilities (including the stormwater infiltration system). Standard erosion control measures are proposed to be used during construction. The primary erosion and sediment control BMP during construction will be proper soil stabilization methods. Exposed soils shall be stabilized by application of effective BMPs that protect the soil from the erosive forces of raindrops, flowing water, and wind. Applicable practices include, but not limited to, temporary and permanent seeding, sodding, mulching, plastic covering, erosion control fabrics, matting, the early application of gravel base on areas to be paved, and dust control. The contractor shall select a soil stabilization method best suited for the particular situation. Stock piles must be stabilized and protected with sediment trapping measures. In addition, site containment of exposed soils shall be sustained by using silt fence barriers along the down -slope boundaries of the site's disturbance areas. See the site development plan for details. Construction Stormwater Pollution Prevention Plan (SWPPP): The following is a summary of the site's erosion control measures that evaluates the typical DOE 13 elements of a SWPPP: Element 1: Mark Clearing Limits: Clearing limits have been delineated on the engineering site development plans. Element 2: Establish Construction Access: A construction access has been delineated on the engineering site development plans. Element 3: Control Flow Rates: During construction silt fencing will provide attenuation of site runoff and upon project completion and stabilization (established lawns and landscape of exposed soils), the infiltration storm system will provide flow control. Element 4: Install Sediment Controls: Filter fabric fence has been delineated and detailed on the engineering site development plans. At a minimum, silt fence will be installed along the down gradient perimeter of the disturbed area that will receive sediment -laden runoff. Element 5: Stabilize Soils: Soils will be stabilized per the TESC notes listed on the engineering site development plans. Element 6: Protect Slopes: Exposed slopes shall be stabilized per the TESC notes listed on the engineering site development plans. Element 7: Protect Drain Inlets: Drain inlet protection will be installed on all catch basins that will receive sediment -laden runoff. See the engineering site development plans for locations and detail. Element 8: Stabilize Channels and Outlets: This element is not applicable since there are no temporary channels or outlets proposed. RAMEngineering, Inc. RAM No. 19-020 18828 Sound View Place Stormwater Site Plan Report Page E-1 Element 9: Control Pollutants: Pollutants shall be managed as described in the TESC notes listed on the engineering site development plans. Element 10: Control De -Watering: Highly turbid or contaminated de -watering water shall be handled separately from stormwater. The water from all de -watering systems for trenches and foundations shall be treated or disposed prior to discharging from the site. Element 11: Maintain BMPs: BMPs shall be maintained and removed at the end of the project as follows: i. All temporary and permanent erosion and sediment control BMPs shall be inspected, maintained and repaired in accordance with the Drainage Manual or as approved or required by the City to assure continued performance of their intended function in accordance with BMP specifications. ii. The applicant may remove temporary BMPs when they are no longer needed. iii. All temporary erosion and sediment control BMPs shall be removed within 30 days after construction is completed and the City has determined that the site is stabilized. Element 12: Manage the Project: The owner of the site is responsible for managing the installation and maintenance of the site BMPs. Element 13. Protect Low Impact Development BMPs: During construction the proposed infiltration trench area shall be protected from sediment accumulation, sediment -laden runoff and soils, and compaction from construction equipment. Soils restoration and/or replacement may be needed if soils are compacted or contaminated with sediment. RAMEngineering, Inc. RAM No. 19-020 18828 Sound View Place Stormwater Site Plan Report Page E-2 F. OPERATION AND MAINTENANCE GUIDELINES: These guidelines are intended to provide operation and maintenance instructions for the project's storm drainage control facilities. The owner is responsible for maintenance of storm drainage facilities within the property (private property owner system); the owner is not responsible for maintenance within the public right-of-way (City system). Private Property Owners: Private property owners are responsible for properly maintaining the stormwater infrastructure on their property to ensure it operates as designed. The City has developed an inspection program to ensure private property owners are properly maintaining their stormwater systems. City System: City crews perform maintenance activities on the entire storm drainage system, including inspection and cleaning of catch basins, street sweeping, emergency flooding response, creek maintenance, inspection and monitoring of private stormwater detention systems. Operation and Maintenance Requirements for private property owner system: This manual is not comprehensive; although it explains the intended operation of the various components of the drainage system, and suggests a routine of inspection and maintenance, it cannot anticipate every problem. Once a historical record of maintenance is established, it may be prudent to alter the routine. It is recommended that maintenance records be kept, and that the records be reviewed periodically. Concept of Operation: The drainage design is shown and described in the site development engineering plans and report. The approved site development plans and report should be retained by the owner and used as a reference to identify drainage facilities outlined in this manual. Conveyance Systems. The design objective in pipe sizing was to convey the large storm events without the water surface exceeding the ground elevation. Frequent overtopping of the pipe system in a particular area might indicate a downstream blockage. Overtopping of the drain systems at the catch -basins is an indication that maintenance is required. Stormwater Infiltration Trench System. The private onsite infiltration trench systems consist of excavated trench filled with drain rock. The infiltration trench system has been designed to infiltrate most storm event; if an extraordinary event was to occur or multiple back to back large storm events occurred the upstream catch -basins may overtop and overflow into the street system. If regular overtopping of the catch basin is experienced the system shall be thoroughly cleaned and inspected. Over a period of time siltation of the infiltration bed can occur (especially if the system and upstream catch basin are not inspected and cleaned regularly) and replacement of the rock in the infiltration system may be required. The following pages outline standard general maintenance criteria for the project's drainage facilities. For additional and updated maintenance information visit the Washington State Department of Ecology's web -site at: http://www.ecy.wa.gov/programs/wq/wghome.htmI PZAM Engineering, Inc. RAM No. 19-020 18828 Sound View Place Stormwater Site Plan Report Page F-1 MAINTENANCE REQUIREMENTS ECDC Section 18.30.090 requires privately -owned stormwater management facilities, such as LID BMPs be properly maintained. The owner of the property is the responsible party for such maintenance. The system must be kept in good working order. The entire system should be inspected once per year. An improperly maintained BMP may cause private property or street flooding. Contact the City Engineering Division for maintenance information. The City may make periodic inspections of BMPs to ensure they are operating properly. ECDC Section 18.30.100 contains the enforcement provisions the City can use to ensure the system is properly maintained. General infiltration Maintenance Criteria Provision should be made for regular and perpetual maintenance of the infiltration basin/trench, including replacement and/or reconstruction of the any media that are relied upon for treatment purposes. Maintenance should be conducted when water remains in the basin or trench for more than 24 hours after the end of a rainfall event, or when overflows occur more frequently than planned. For example, off-line infiltration facilities should not have any overflows. Infiltration facilities designed to completely infiltrate all flows to meet flow control standards should not overflow. Removal of accumulated debris/sediment in the basin/trench should be conducted every 6 months or as needed to prevent clogging, or when water remains in the pond for greater than 24 hours after the end of a rainfall event. RAM -ngineering, Inc. RAM No. 19-020 18828 Sound View Place Stormwater Site Plan Report Page F-2 Appendix V-A: BMP Maintenance Tables Ecology intends the facility -specific maintenance standards contained in this section to be conditions for determining if maintenance actions are required as identified through inspection. Recognizing that Permittees have limited maintenance funds and time, Ecology does not require that a Permittee perform all these maintenance activities on all their stormwater BMPs. We leave the determination of importance of each maintenance activity and its priority within the stormwater program to the Permittee. We do expect, however, that sufficient maintenance will occur to ensure that the BMPs continue to operate as designed to protect ground and surface waters. Ecology doesn't intend that these measures identify the facility's required condition at all times between inspections. In other words, exceedance of these conditions at any time between inspections and/or maintenance does not automatically constitute a violation of these standards. However, based upon inspection observations, the Permittee shall adjust inspection and maintenance schedules to minimize the length of time that a facility is in a condition that requires a maintenance action. Table V-A.1: Maintenance Standards - Detention Ponds Maintenance Component Defect Conditions When Maintenance Is Needed Results Expected When Maintenance Is Performed Any trash and debris which exceed 1 cubic feet per 1,000 square feet. In general, there should be no visual evidence of Trash &Debris dumping. Trash and debris cleared from site If less than threshold all trash and debris will be removed as part of next scheduled maintenance. General Any poisonous or nuisance vegetation which may constitute No danger of poisonous a hazard to maintenance vegetation where maintenance personnel or the public. personnel or the public might normally be. (Coordinate with Poisonous Any evidence of noxious weeds local health department) Vegetation and as defined by State or local noxious weeds regulations. Complete eradication of noxious weeds may not be possible. (Apply requirements of adopted Compliance with State or local IPM policies for the use of eradication policies required herbicides). RAMEngineering, Inc. RAM No. 19-020 18828 Sound View Place Stormwater Site Plan Report Page F-3 Table V-A.1: Maintenance Standards - Detention Ponds Maintenance Defect Conditions When Results Expected When Component Maintenance Is Needed Maintenance Is Performed Any evidence of oil, gasoline, contaminants or other pollutants Contaminants and No contaminants or pollutants Pollution (Coordinate removal/cleanup present. with local water quality response agency). Any evidence of rodent holes if Rodents destroyed and dam or facility is acting as a dam or berm repaired. (Coordinate with Rodent Holes berm, or any evidence of water local health department; piping through dam or berm via coordinate with Ecology Dam rodent holes. Safety Office if pond exceeds 10 acre-feet.) Facility is returned to design function. Beaver Dams Dam results in change or function of the facility. (Coordinate trapping of beavers and removal of dams with appropriate permitting agencies) Insects destroyed or removed When insects such as wasps from site. Insects and hornets interfere with maintenance activities. Apply insecticides in compliance with adopted IPM policies Tree growth does not allow maintenance and inspection access or interferes with maintenance activity (i.e., slope mowing, silt removal, vactoring, Trees do not hinder or equipment movements). If maintenance activities. trees are not interfering with Harvested trees should be Tree Growth and access or maintenance, do not recycled into mulch or other Hazard Trees remove beneficial uses (e.g., alders for firewood). If dead, diseased, or dying trees are identified Remove hazard Trees (Use a certified Arborist to determine health of tree or removal requirements) R.4MEngineering, Inc. 18828 Sound View Place RAM No. 19-020 Stormwater Site Plan Report Page F-4 Table V-A.1: Maintenance Standards - Detention Ponds Maintenance Defect Conditions When Results Expected When Component Maintenance Is Needed Maintenance Is Performed Slopes should be stabilized using appropriate erosion Eroded damage over 2 inches control measure(s); e.g.,rock deep where cause of damage is reinforcement, planting of grass, still present or where there is compaction. Side Slopes of Pond Erosion potential for continued erosion. If erosion is occurring on Any erosion observed on a compacted berms a licensed compacted berm embankment. engineer in the state of Washington should be consulted to resolve source of erosion. Accumulated sediment that exceeds 10% of the designed Sediment cleaned out to Sediment pond depth unless otherwise designed pond shape and specified or affects inletting or depth; pond reseeded if Storage Area outletting condition of the necessary to control erosion. facility. Liner (if Applicable) Liner is visible and has more Liner repaired or replaced. Liner than three 1/4-inch holes in it. is fully covered. Any part of berm which has settled 4 inches lower than the design elevation If settlement is apparent, measure berm to determine amount of settlement Dike is built back to the design Settlements elevation. Settling can be an indication of more severe problems with the Ponds Berms berm or outlet works. A licensed (Dikes) engineer in the state of Washington should be consulted to determine the source of the settlement. Discernable water flow through pond berm. Ongoing erosion with potential for erosion to Piping eliminated. Erosion Piping continue. potential resolved. (Recommend a Goethechnical engineer be called in to inspect PZAM Engineering, Inc. RAM No. 19-020 18828 Sound View Place Stormwater Site Plan Report Page F-5 Table V-A.1: Maintenance Standards - Detention Ponds Maintenance Defect Conditions When Results Expected When Component Maintenance Is Needed Maintenance Is Performed and evaluate condition and recommend repair of condition. Tree growth on emergency Trees should be removed. If root spillways creates blockage system is small (base less than problems and may cause failure 4 inches) the root system may of the berm due to uncontrolled be left in place. Otherwise the Tree Growth overtopping. roots should be removed and the berm restored. A licensed Tree growth on berms over 4 engineer in the state of feet in height may lead to piping Washington should be consulted Emergency through the berm which could for proper berm/spillway Overflow/ Spillway lead to failure of the berm. restoration. and Berms over 4 feet in height Discernable water flow through pond berm. Ongoing erosion with potential for erosion to continue. Piping Piping eliminated. Erosion potential resolved. (Recommend a Geotechnical engineer be called in to inspect and evaluate condition and recommend repair of condition. Only one layer of rock exists above native soil in area five square feet or larger, or any Emergency Emergency exposure of native soil at the Rocks and pad depth are Overflow/Spillway Overflow/Spillway top of out flow path of spillway. restored to design standards. (Rip -rap on inside slopes need not be replaced.) Erosion See "Side Slopes of Pond" Table V-A.2: Maintenance Standards - Infiltration Maintenance Defect Conditions When Maintenance Is Component I Needed General Trash & Debris See Table V-A.1: Maintenance Standards - Detention Ponds R.4MEngineering, Inc. RAM No. 19-020 Results Expected When Maintenance Is Performed See Table V-A.1: Maintenance 18828 Sound View Place Stormwater Site Plan Report Page F-6 Table V-A.2: Maintenance Standards - Infiltration Maintenance Conditions When Maintenance Is Results Expected Component Defect Needed When Maintenance Is Performed Standards - Detention Ponds See Table V-A.1: Poisonous/Noxious See Table V-A.1: Maintenance Maintenance Vegetation Standards - Detention Ponds Standards - Detention Ponds See Table V-A.1: Contaminants and See Table V-A.1: Maintenance Maintenance Pollution Standards - Detention Ponds Standards - Detention Ponds See Table V-A.1: Rodent Holes See Table V-A.1: Maintenance Maintenance Standards - Detention Ponds Standards - Detention Ponds Water ponding in infiltration pond after rainfall ceases and appropriate time allowed for infiltration. Treatment basins should infiltrate Water Quality Design Storm Volume within 48 hours, and Sediment is removed empty within 24 hours after cessation of and/or facility is Storage Area Sediment most rain events. cleaned so that infiltration system works according to (A percolation test pit or test of facility design. indicates facility is only working at 90% of its designed capabilities. Test every 2 to 5 years. If two inches or more sediment is present, remove). Filter Bags (if Filled with Sediment Sediment and debris fill bag more than Filter bag is replaced applicable) and Debris 1/2 full. or system is redesigned. By visual inspection, little or no water Gravel in rock filter is Rock Filters Sediment and Debris flows through filter during heavy rain replaced. storms. See Table V-A.1: Side Slopes of Erosion See Table V-A.1: Maintenance Maintenance Pond Standards - Detention Ponds Standards - Detention Ponds PZAM Engineering, Inc. RAM No. 19-020 18828 Sound View Place Stormwater Site Plan Report Page F-7 Table V-A.2: Maintenance Standards - Infiltration Maintenance Conditions When Maintenance Is Results Expected Component Defect Needed When Maintenance Is Performed See Table V-A.1: Tree Growth See Table V-A.1: Maintenance Maintenance Standards - Detention Ponds Standards - Detention Ponds Emergency Overflow Spillway and Berms over 4 feet in height. See Table V-A.1: Piping See Table V-A.1: Maintenance Maintenance Standards - Detention Ponds Standards - Detention Ponds See Table V-A.1: Rock Missing See Table V-A.1: Maintenance Maintenance Standards - Detention Ponds Standards - Detention Ponds Emergency Overflow Spillway See Table V-A.1: Erosion See Table V-A.1: Maintenance Maintenance Standards - Detention Ponds Standards - Detention Ponds Pre -settling Ponds Facility or sump filled 6" or designed sediment trap depth of and Vaults with Sediment and/or sediment. Sediment is removed. debris Table V-A.S: Maintenance Standards - Catch Basins Maintenance Component Defect Conditions When Maintenance is Needed Results Expected When Maintenance is performed Trash or debris which is located immediately in front of the catch basin opening or is blocking No Trash or debris inletting capacity of the basin by more than located immediately in General 10%. front of catch basin or Trash & Debris on grate opening. Trash or debris (in the basin) that exceeds 60 percent of the sump depth as measured from No trash or debris in the bottom of basin to invert of the lowest pipe the catch basin. into or out of the basin, but in no case less than R.4MEngineering, Inc. RAM No. 19-020 18828 Sound View Place Stormwater Site Plan Report Page F-8 Table V-A.5: Maintenance Standards - Catch Basins Maintenance Results Expected Component Defect Conditions When Maintenance is Needed When Maintenance is performed a minimum of six inches clearance from the debris surface to the invert of the lowest pipe. Inlet and outlet pipes free of trash or debris. Trash or debris in any inlet or outlet pipe blocking more than 1/3 of its height. No dead animals or vegetation present within the catch basin. Dead animals or vegetation that could generate odors that could cause complaints or dangerous gases (e.g., methane). Sediment (in the basin) that exceeds 60 percent of the sump depth as measured from the bottom of basin to invert of the lowest pipe into or out of the basin, but in no case less than No sediment in the Sediment a minimum of 6 inches clearance from the catch basin sediment surface to the invert of the lowest pipe. Top slab has holes larger than 2 square inches Top slab is free of or cracks wider than 1/4 inch. (Intent is to make holes and cracks. Structure Damage sure no material is running into basin). to Frame and/or Frame is sitting flush Top Slab Frame not sitting flush on top slab, i.e., on the riser rings or top separation of more than 3/4 inch of the frame slab and firmly from the top slab. Frame not securely attached attached. Maintenance person judges that structure is Basin replaced or unsound. repaired to design Fractures or standards. Cracks in Basin Grout fillet has separated or cracked wider than Walls/ Bottom 1/2 inch and longer than 1 foot at the joint of Pipe is and any inlet/outlet pipe or any evidence of soil a t basinn wall. secure at basin particles entering catch basin through cracks. Settlement/ If failure of basin has created a safety, function, Basin replaced or repaired to design Misalignment or design problem. standards. Vegetation Vegetation growing across and blocking more No vegetation blocking than 10 /o of the basin opening. opening to basin. R.4MEngineering, Inc. RAM No. 19-020 18828 Sound View Place Stormwater Site Plan Report Page F-9 Table V-A.S: Maintenance Standards - Catch Basins Maintenance Results Expected Component Defect Conditions When Maintenance is Needed When Maintenance is performed Vegetation growing in inlet/outlet pipe joints No vegetation or root that is more than six inches tall and less than growth present. six inches apart. Contamination See Table V-A.1: Maintenance Standards - No pollution present. Detention Ponds and Pollution Cover/grate is in place, Cover Not in Cover is missing or only partially in place. Any meets design Place open catch basin requires maintenance. standards, and is secured Locking Mechanism cannot be opened by one Mechanism opens with Catch Basin Mechanism Not maintenance person with proper tools. Bolts proper tools. Cover Working into frame have less than 1/2 inch of thread. One maintenance person cannot remove lid after applying normal lifting pressure. Cover can be removed Cover Difficult to by one maintenance Remove (Intent is keep cover from sealing off access to person. maintenance.) Ladder is unsafe due to missing rungs, not Ladder meets design Ladder Ladder Rungs securely attached to basin wall, misalignment, standards and allows Unsafe rust, cracks, or sharp edges. maintenance person safe access. Grate opening Grate with opening wider than 7/8 inch. Grate opening meets Unsafe design standards. Trash and Debris Trash and debris that is blocking more than Grate free of trash and Metal Grates 20% of grate surface inletting capacity. debris. (If Applicable) Grate is in place, meets Damaged or Grate missing or broken member(s) of the the design standards, Missing. grate. and is installed and aligned with the flow path. PZAM Engineering, Inc. RAM No. 19-020 18828 Sound View Place Stormwater Site Plan Report Page F-10 FIALIVI ENGINEERING, INC. Civil Engineering 1 Land Planning