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APPROVED STM RESUB1 BLD2021-0895+STORMWATER REPORT+10.31.2021_10.56.47_AM+2492741RESUB �-A J re] 10 Nov 01 2021 CITY OF EDMONDS ENGINEERING DEVELOPMENT SERVICES DEPARTMENT CIVIL SITE DESIGN PO Box 171 Edmonds, WA 98020 206.419.0973 BLD2021-0895 Project: STORMWATER SITE PLAN COMPLIES WITH APPLICABLE CITY STORMWATER CODE Eastman King Single Family Residence (SFR) 131 Skyline Dr Edmonds, WA 98020 Prepared For: Sue Eastman King and Gerald King 131 Skyline Dr Edmonds, WA 98020 Prepared By: Steve Hatzenbeler, PE Date: June 3, 2021 Revised October 18,2021 TABLE OF CONTENTS Section # Subiect Page # Section 1 Project Overview..........................................................................................1 Section z Existing Conditions Summary.....................................................................2 Section 3 Existing Site HydrologY...............................................................................3 Section 4 Minimum Requirement #4, Offsite Analysis..............................................3 Section 5 Developed Site Hydrology..........................................................................4 5.1 Summary Section........................................................................................4 5.2 Performance Standards and Goals.............................................................7 5.3 Low Impact Development Features...........................................................8 5.4 Flow Control, Water Quality Systems, and Conveyance ...........................8 Section 6 Special Reports and Studies.......................................................................8 Section 7 Construction SWPPP Report......................................................................9 Section 8 Operation and Maintenance Manual........................................................10 Section 9 Establishment of Maintenance Covenant................................................10 LIST OF FIGURES Figure1 Vicinity Map..................................................................................................1 Figure z Downstream Flow Path..............................................................................4 Figure 3 Impervious Surfaces....................................................................................7 LIST OF APPENDICES Appendix A Stormwater Calculations Appendix B Geotechnical Report Appendix C Construction SWPPP Appendix D Operation and Maintenance Manual Appendix E Maintenance Covenant Eastman King SFR Project #21013 Stormwater Site Plan Statiomo Engineering PLLC Section i — Pro]ect Overview The project is a development of a single family residence and associated site improvements such as driveways, retaining walls, and landscaping. The property Owner is applying for building permit to construct the home and related site improvements on an undeveloped parcel. The site is in the Emerald Hills neighborhood in Edmonds. Site Address: 131 Skyline Drive Parcel Number: 00423000005300 Parcel Size: 0.32 acres Zoning: RS-12 Legal Description (from Survey): LOT 53, OF EMERALD HILLS, ACCORDING TO THE PLAT THEREOF RECORDED IN VOLUME 31 OF PLATS, PAGES 46-49, RECORDS OF SNOHOMISH COUNTY WASHINGTON. SITUATE IN THE COUNTY OF SNOHOMISH, STATE OF WASHINGTON. See Figure i for a vicinity map of the project area. f 3 i � 1� � NSTSW 3f0 — 9122 238 1 I j4 274 O 913't 20620 O I L Dg � � 9132 20622 1201 A Z17 } +127 9129 20710 12t10 1126 % ZDM P1 W 9112 L - -- - Q 17 '8 I i1 114� �na�r _ I_ Project Site 0802 131 Skyline Drive 9 9, 16 Edmonds, WA 98020 9537 Figure i — Vicinity Map (from Edmonds GIS) 20820 P 70878 Eastman King SFR Project #21013 Stormwater Site Plan Page 1 Stationlo Engineering PLLC A new storm drainage system will be installed around the new home to control stormwater runoff in accordance with the Department of Ecology 2014 Stormwater Management Manual for Western Washington (DOE Manual) and the 2017 Edmonds Stormwater Addendum. Catch basins, area drains, and trench drains, and an underground conveyance system will be installed to route collected stormwater runoff to the new underground detention tank along the north edge of the property. The outfall from the detention tank will be a piped connection to the existing 12-inch storm drain main line in Skyline Drive along the north edge of the site. Stormwater detention is proposed throughout the site because the steep slopes and dense soil conditions make infiltration and dispersion infeasible at this site. The project will include approximately 5,825 SF of new/replaced impervious surfacing; that total includes approximately 1,413 SF of new/replaced pollution generating impervious surfacing. No water quality treatment is proposed. The project's disturbance area is approximately 13,58o SF. Section z — Existing Conditions Summary The existing topography on the site is variable. There is a level area on the eastern quarter of the parcel adjacent to the sidewalk on the east leg of Skyline Drive, and then there is a slope Of 40% or more down to the gravel path on the west, dropping roughly 30 ft. The area is identified in the Edmonds GIS mapping as a Severe Erosion Hazard and Landslide Hazard Critical Area. A soils investigation was completed in December 2020. Two test pits were excavated to depths of 9 ft below existing grade. The geotechnical engineer observed loose to medium dense fill over dense glacial till. Groundwater was not encountered. Based on the dense soil conditions and steep topography, the geotechnical engineer's opinion is that the subsurface conditions at the site are not conducive to infiltration or dispersion. Refer to the Cobalt Geosciences geotechnical report in Appendix B, as well as Section 6 below, for additional information on the location of the borings and the soil types encountered. Eastman King SFR Project #21013 Stormwater Site Plan Page z Statiomo Engineering PLLC Section 3 — Existing Site Hydrology Existing conditions in the project area primarily consist of natural grass surfacing. Along the west edge there is a gravel community walking path partially within the property boundary that will not be disturbed in this project. Along the east edge there is a public sidewalk that will be minimally disturbed for installation of a new driveway. There are no existing on -site pollution generating impervious surfaces. There is no existing stormwater runoff collection on site; stormwater runoff from the site appears to discharge as sheet flow runoff to the west and northwest. There does not appear to be any upstream off -site drainage flowing onto the property. There is a public drainage system consisting of catch basins and 12-inch conveyance pipes along the north edge of the site in Skyline Drive. See Section z above and the geotechnical report in Appendix B for details of the site soil conditions. Section 4 — Minimum Requirement #4, Offsite Analysis The site is in the Shell Creek drainage basin. The drainage system where the on -site stormwater system will connect is a iz-inch diameter concrete pipe in Skyline Drive, and continues as a iz-inch system from the site downstream through the Emerald Hills neighborhood via Skyline Dr, Highland Dr, and Emerald Hills Dr, to iioi Emerald Hills Dr, where the public drainage system crosses private property to reach Olympic Ave. The 12-inch system continues south along Olympic Ave, then turns west where it intersects Main St. The iz-inch system continues west to the point where Shell Creek crosses Main St at Yost Park in a 24-inch diameter concrete pipe. The 24-inch pipe crosses Main St to the north and discharges into an open channel at a distance of approximately 0.4 miles downstream of the site. A diagram of the downstream flow path is shown in Figure t below. There are no upstream areas tributary to the project site, as the neighboring parcel to the south is roughly level with the subject parcel, and the streets surrounding the site are isolated from the site with curb and gutter that prevents street runoff from entering the property. Most of the drainage system between the site and Shell Creek appears to be relatively steeply sloped, as there is a drop in elevation of approximately 170 vertical feet from the site to the Shell Creek discharge point, a distance of roughly z,zoo LF. There are no apparent capacity problems given the pipe size and slope. The downstream analysis was completed on May 31, 2021. Weather conditions were sunny and dry at the time the observations were made, so inferences were made based on the conditions at the time of the site visit. No obstructions were observed in the portions of the public drainage system that we could observe. Based on the observations made during the field inspection and the limited amount of new runoff being conveyed to the public storm drain because of the proposed on -site detention system, no negative impacts to the systems downstream are anticipated from the proposed project. Eastman King SFR Project #21013 Stormwater Site Plan Page 3 Statiomo Engineering PLLC f Approx discharge point from site to 12" public o, MONDSST drainage system 12" public a31 �- drainage L"` a - _ _ na t sysem z c GIs 11a a BELL ST °' lid Public drainage� system increases 7 T z� to 24" ? 1121 I11 S iL 'I 175 1I .' Poe_7nP-1 iJt qy •- �AIN ST - Project Site 12" public 131 Skyline Drive drainage Edmonds, WA 98020 system Discharge to Shell Creek from 24" public drainage system �n Figure 2 - Downstream Flow Path (from Edmonds GIS) Section 5 - Developed Site Hydrology Section 5.1 - Summary Section The project is a single family residence. The building roof area is 3,513 SF, and the total new/replaced impervious on the project, including on -site and right of way work, is 5,825 SF. Trench drains and area drains will collect surface runoff and convey it to an on -site detention tank along the north edge of the site. The project requires a Building Permit. We don't know of any other permits required. Table 1: Impervious and Pervious Surfacing within Disturbance Limits Impervious Surfaces Existing Proposed SF Acres SF Acres Roof Areas 0 0.O 3,513 o.o81 Patio/Sidewalk (non-PGIS) Areas 222 0.005 899 O.021 Driveways/Roadways (PGIS) 169 0.004 1,413 0.032 Total Impervious Area 391 0.009 5,$25 0•134 Pervious Surfaces Existing Proposed SF Acres SF Acres Lawn 13,189 0.303 0 0 Planting Areas 0 0 7,755 0.178 Converted Vegetation N/A N/A 0 0 Total Pervious Area 13,189 0.303 7,755 O.i78 Eastman King SFR Project #21013 Stormwater Site Plan Page 4 Stationlo Engineering PLLC The area is identified in the Edmonds GIS mapping as a Severe Erosion Hazard and Landslide Hazard Critical Area. There is an existing neighboring single family residence approximately to ft south of the south property line. The proposed building is set back to ft from the south property line, approximately 37 ft from the west property line, approximately 27 ft minimum from the north property line, and approximately 32 ft from the east property line. Minimum Req. #1 Preparation of Stormwater Site Plans: This document and the drawings comprise the Stormwater Site Plan. Minimum Req. #z Construction Stormwater Pollution Prevention: Refer to Appendix C. Minimum Req. #3 Source Control of Pollution: Stormwater is not expected to come into contact with any pollutants that require source controls. Minimum Req. #4 Preservation of Natural Drainage Systems and Outfalls: Natural drainage systems and outfalls will be maintained with the project. A drainage system will be installed to remove stormwater runoff from the site rather than relying on surface sheet flow runoff as is the case today. Minimum Req. #5 Onsite Stormwater Management: Onsite Stormwater Management (OSM) was evaluated per Section 5.5 of the Edmonds Stormwater Addendum. The project is a Category z project subject to Minimum Requirements #1-9, thus List #2 in ECDC 18.30.o6o.D.5 applies. The List #2 OSM options have been evaluated for each new/replaced impervious surface. List #2 for Lawn and Landscaped Areas: • Landscaped areas will have soils prepared in accordance with BMP T5.13 of the DOE Manual. List #2 for Roof Areas: • Full Dispersion: Infeasible due to the limited space available on site, and the lack of native vegetated surfaces. • Downspout Full Infiltration: Infeasible due to the Critical Areas, steep topography, and dense soil conditions. • Bioretention: Infeasible due to the Critical Areas, steep topography, and dense soil conditions. • Downspout Dispersion: Infeasible because a vegetated flow path at least 50 ft long and less than 15% slope is not available. • Perforated Stub -Out Connection: Infeasible due to the Critical Areas, steep topography, and dense soil conditions. • Detention Vault or Pipe: The project design includes a 3-ft detention tank in accordance with Edmonds Stormwater Addendum Section 6.3. Eastman King SFR Project #21013 Stormwater Site Plan Page 5 Statiomo Engineering PLLC List #2 for Other Hard Surfaces: • Full Dispersion: Infeasible due to the limited space available on site, and the lack of native vegetated surfaces. • Permeable Pavement: Infeasible due to the Critical Areas, steep topography, and dense soil conditions. • Bioretention: Infeasible due to the Critical Areas, steep topography, and dense soil conditions. • Sheet Flow Dispersion: Infeasible because a vegetated flow path at least 50 ft long and less than 15% slope is not available. • Detention Vault or Pipe: The project design includes a 3-ft detention tank in accordance with Edmonds Stormwater Addendum Section 6.3. Minimum Req. #6 Runoff Treatment: Because the project includes less than 5,000 SF of new/replaced Pollution Generating Impervious Surfacing (PGIS), water quality treatment is not required. Minimum Req. #7 Flow Control: As noted above in Table 1, the project proposes approximately 5,825 SF of new/replaced impervious. The new/replaced impervious surface area was analyzed in WWHM 2012 to compare the historic (forested) loo-year peak runoff rate to the developed conditions loo-year peak runoff rate. Results of the WWHM analysis (using the impervious and pervious areas noted above in Table 1) are summarized in the table below and detailed in the WWHM output in Appendix A. Table 2: New/Replaced Impervious Surface Peak Runoff Rates WWHM Model Conditions (15-min time steps) Peak Runoff Rate (CFS) Historic Conditions 0.0202 Developed Conditions 0.1552 Difference in loo-yr peak runoff rate 0.1350 The increase in the ioo-year peak runoff rate is less than 0.15 cfs using 15-minute time steps in the WWHM model. Therefore, in accordance with the thresholds defined in Minimum Requirement #7 in the Edmonds Stormwater Addendum and ECDC 18.30.o6o.D.7.b.iii, formal flow control is not required. Minimum Req. #8 Wetlands Protection: No wetland exist on or near the site. Therefore, MR #8 does not apply. Minimum Req. #g Operation and Maintenance: The Owner will be responsible for maintenance and operation of the proposed stormwater facilities. Operation and Maintenance guidelines are included in Appendix D. Eastman King SFR Project #21013 Stormwater Site Plan Page 6 Statiomo Engineering PLLC Section 5.2 — Performance Standards and Goals The project is exempt from water quality treatment (MR #6) and formal flow control (MR #7). A detention tank per the Edmonds Stormwater Addendum Section 6.3 is proposed to address MR #5. Details for the detention system are included in the design drawings, and the tank sizing calculation is provided in Appendix A. The detention tank will be 5o LF of 3-ft diameter polyethylene with a 6o-inch diameter flow control structure. The flow control riser will have a 0.5-inch orifice and a flat top level with the top of the tank. It is not feasible to collect all of the new/replaced hard surface runoff, primarily due to the steep site topography; some of the new/replaced hard surface runoff is curb, sidewalk, driveways, and street restoration that slope to drain to the public system in the street, and are not tributary to the on -site drainage system. The collected surface areas are shown in Figure 3 below and on drawing C2.1, and noted in the table below: Table ;: New/Replaced Impervious Surface Tributary to Detention Svstem New/Replaced Impervious Surfaces Total Area (SF) Collected Area (SF) Roof Areas 3,513 3,513 Patio/Sidewalk (non PGIS) Areas 899 850 Driveways/Roadways (PGIS) 1,413 726 Total New/Replaced Impervious Surface Area 5,$25 5,089 Figure 3 below shows the impervious areas and the collected impervious surface areas. I SAY/;fie Dom. Sllh Il Rk1p�Ch AREA f Y _i LLLL_I LLLLL_L �+J LLLLLI !L__LLLLLL-LL ' mi SURFACE 1: 8LDG ROOF AREA AREA: 3,513 SF SURFACE 2: NON ROOF AREA, NON—PGIS HARDSCAPE AREA: 899 SF SURFACE 3: NON —ROOF AREA, PGIS AREA: 1,413 SF IMPERVIOUS SURFACE AREA COLLECTED AND ROUTED TO DETENTION TANK: AREA: 5,089 SF NI TC'AL LOT AREA: 14,127 SF DISTU78ANCE AREA 13,580 SF AE'd7j4-PLACED IMPERVIOUS: 5,825 5F Figure 3 — Impervious Surfaces (also see Drawing C2.1) Eastman King SFR Project #21013 Stormwater Site Plan Page 7 Stationlo Engineering PLLC Section 5.3 — Low Impact Development Features Critical Areas, steep topography, and dense soil conditions make OSM BMPs infeasible (see MR #5 details above), with the exception of a detention tank. Section 5.4 — Flow Control, Water Quality Systems, and Conveyance Formal flow control (MR #7) and water quality treatment (MR #6) are not required for the project. A detention tank is proposed for MR #5, and the sizing calculations for the tank are included in Appendix A. Conveyance capacity in the proposed drainage system was estimated using the Rational Method for peak flow rates, and Manning's Equation for pipe capacity. There are some portions of the pipe system that consist of 4-inch pipes that convey runoff from limited impervious areas. Larger collected areas are conveyed in 6-inch pipes with a slope of at least 2%. Calculations for the peak flow rates and pipe capacity are included in Appendix A. The estimated ioo-year peak flow rate for the site is o.64 CFS, and the capacity of the 6-inch pipes is 0.74 CFS. See Appendix A calculations for additional information. Section 6 — Special Reports and Studies The project's geotechnical report is attached in Appendix B. See Figures z and 3 below for a graphic of the geotechnical test pit locations and observations. Figure 2 — Cobalt Geosciences Test Pit Locations Eastman King SFR Project #21013 Stormwater Site Plan Page 8 Statiomo Engineering PLLC Test Pit TP-1epth:9' Date: December 1, 2020 D Groundwater; None Contractor Jim Elevation: Logged By: PH Checked By: SC a, O 6 Moisture Content 1%11 Pbsic 1 Llyuitl LL a F S u— L Q. o i t 6 Material Description DCP Equivalent N-Value c o 0 10 20 30 40 SO �_�__ ____ __ TopsoilVe�c etation ______ ___ _ _____ ______ ______ • SM Loose to medium dense. silty -fine to medium grained sand with gravel dark yellowish brown to grayish brown. moist. 2 (Fill( 3 q SM Medium dense to dense, silty -fine to medium grained sand with gravel grayish brown, moist- 5 (Glacial Tilq 6 7 8 End of Test Pit 9' D Test Pit TP-2 Date: December 1, 2020 Depth:9' Groundwater: None Contractor: Jim Elevation: Logged By: PH Checked By: SC N g o y Moisture Content 1%) LL d 3 Plastic! 1 Quid Limn r Limn u a Material Description C 'o DCP Equivalent N-Value 0 2 ? C70 10 20 30 40 _---- _ ______ ___________ =. t SM Loose to medium dense, silty -fine to medium grained sand with grovel dark yellowsh brown to grayish brown, moist. 2 (Fill) 3 4 5 ------ y ----'. -- SM ----------------------------------------- Medium dense to dense. silty -fine to medium grained sand with gravel grayish brown. maid. (Glacial Till( e End 01 Test Pit 9' 10 Figure 3 - Existing Site Soil Conditions per Cobalt Geosciences Report Section 7 - Construction SWPPP Report The project's Construction Stormwater Pollution Prevention Plan (SWPPP) report is attached in Appendix C. Eastman King SFR Project #21013 Stormwater Site Plan Page 9 Statiomo Engineering PLLC Section 8 - Operation and Maintenance Manual The project's Operation and Maintenance Manual is attached in Appendix D. Section g - Establishment of Maintenance Covenant A draft Maintenance Covenant is attached in Appendix E. Eastman King SFR Project #21013 Stormwater Site Plan Page io Statiomo Engineering PLLC Appendix A Stormwater Calculations Eastman King SFR Project #21013 Stormwater Site Plan Statiomo Engineering PLLC WWHM Site Location Map: Snohomish2012 Map ControlsI Predeveloped Conditions: 00 SCENARIOS f 0 Predereluped ` 1 ❑ Mitigated u Run Sce D asic Elements ®®®® Pro Elements r®n Imo! Commercial Toolbox Move Elements 4? S x y Load x.v Sun H5a -100yr peaks - Finish Mitigated 1 �E�0 Site Information Site Name Address City Gage Everett Precip Factor a,grkQ 0 Use S-DOT data 0 Show DOT Zones DOT R egion: Puget E ast Isohyetal value 36 M Subbasin Name: Basin 1 Surface InterFlow Groundwater Flows To : II 0 II Area in Basin r Show Only Selected Available Pervious Acres Available Impervious Acres r- A/B, Forest, Flat 0 r- ROADS/FLAT 0 r- A/B, Forest, Mod 0 r ROADS/MDD 0 F- A/B, Forest, Sleep r ROADS/STEEP 0 rA/B, Pasture, Flat 0 i✓ ROOF TDPSlFL4T 0 F-A/B, Pasture, Mod 0 r DRIVEWAYS/FLAT 0 rA/B, Pasture, Steep 0 DRIVEWAYSlMOD 0 rA/B, Lawn, Flat 0 E- DRIVEWAYS/STEEP 0 rA/B, Lawn, Mod 0 rl-SIDEWALKS/FLAT 0 F Lawn, Steep 0 r SIDEWALKS/MDD 0 F- C, Forest, Flat 0 r' SIDEWALKSISTEEP 0 r C, Porest, Mod 0 r PARKING/FLAT 0 FJ C, Forest, Steep 31 r PARKINGIMOD 0 F C, Pasture, Flat 0 f- PARKINGISTEEP 0 F C, Pasture, Mod 0 f- POND 0 f- C, Pasture, Sleep 0 Porous Pavement 0 f- C, Lawn, Flal 0 r C, Lawn, Mod 0 f- C, Lawn, Steep 0 r SAT, Porest, Flat 0 r SAT, Forest, Mod 0�� f -tlF , Poresl, Steep I0 Pervious Total 0.31 Ares Impervious Total © Acres DasinTotal 0.31 Ares Precipilatiun Gage FSILVERLIEvered 71 Auto Assign Gages Deselect Zero SelectBy:j - co Eastman King SFR Stormwater Site Plan Statiomo Engineering PLLC Project #21013 Developed Conditions: SCENARIOS I � � . I]Predeveloped' • 0 Mitigated Run Scenario Basic El .... I. ®®® ®®■ ®®® O Pro Elements LID Iool6ox Commercial Toolbox Move EI menls- Save x,y Load x,y Mon4�48p-100yrpeaksRevl- Finish Mitigated �1: easir, 1 Mitig-d 1 Subbasin Na.._ Basin 1 Designate as Bypass for PDC. Surface Interflow Groundwater Flows To: 0 I 0 Area in Basin FShow Only Selected Available Pervious Acres Available Impervious Acres rWD,Fc-t,Flat 0 r RCADS/FL4T 0 rA/6, Forest, Mod 0 F-RDADS/MDD 0 F AIB, Farest,Steep 0 r ROAOGISTEEP 0 r AIB, Pasture, Flat © ROOF TDPS/FLAT -081 F AID, Paskure, Mod 0 r DRIVEWAYSlFL4T 0 rA/B, Paskure, Steep © r ORIVEWAYG/MOD -032 r A/6, Lawn, Flat 0 r DRIVEWAYS/STEEP 0 r AIB, Lawn, Mod 0 SIDEWALKSlFL4T .021 F-A/B, Lawn, Steep 0 r SIDEWALKS/MDD 0 F C, Forest, Flat 0 r SIDEWALKSlSTEEP 0 F- C, Forest, Mod 0 !- PARKING/FLAT 0 io C, Porest, Sleep 0 r PAR KINGlM00 0 (- C, Pasture, Flat ® !- PARKING/STEEP 0 C, Pasture, Mod 0 PDND 0 r C, Pasture, Steep 0 r Porous Pavement 0 r C, Lawn, Flat 0 r' C, Lawn, Mod 178 r C, Lawn, Sleep 0 r SAL PoresL Flak 0 SAT, Forest, Mod --Ir r SAT, Forest, Sleep �� Pervious Total 0.178 Acres Impervious Total 0.134 Acres Basin Total 0.312 Acres Precipitation Gage 2 - 361 Puget East 36 Precip_J Aulo Assign Gages Deselect Zero Select By:] GO goo -year WWHM Peak Flow Rate Comparison (i5-min Time Steps) ®I Cumulative Probabil ty I.e ax x x xxxxxx � +++++ + 01 LL 801 Q.401 + Q.401 05 1 2 5 10 20 BO 50 70 50 90 95 99 99'A 51 Steam Pmlection Duration LID Duration Flow Frequency I Water QualityHydegraph Wetland Input Volumes LID Report Recharged Recharge Predeveloped Recharge Mitigated 1 Analyze datasets Compact WDM Delete Selected F- Monthly FF So ill All Dalasets I Flow Stage Precip 7aap POC1 J Flood Frequency Method 6' Log Pearson Type III 17B t' Weibull r' Cunnane f Gringorlen n Flow Fregaency "Flow(efs) Predeveloped Mitigated 2 Year = 0.0086 0.0467 5 Year = 0.0130 0.0676 10 Year = 11 0153 0.0844 25 Y r = 0.0177 0.1094 50 Year - 0.0191 0.1309 100 Year = 0.0202 0.1552 A-f Peaks 1902 0.0117 0.0480 1903 0.0042 0.0544 1904 111 0.0783 1905 0.0047 0.03111 1906 0.0135 0.0321 1907 U. 0138 0. 11471 1900 0.0083 0.0384 1909 0.0093 0.114411 1910 0.0143 0.0494 1911 11 0080 0.046f1 1912 If.0220 0.1269 1913 0.0102 0.0314 1914 0.0031 0.1714 1915 0. 0043 0.0299 1916 0.0062 0.0520 1917 0.0038 0.0268 1918 111 0.0419 1919 0, 0052 0.0262 1920 0.0080 0.0407 1921 0.' 0 0.0317 1922 0. 0093 0.0497 1923 0.0062 0.0399 1924 0. 0041 0. LI5117 1925 It.0042 0.0270 1926 0.0073 0.0518 1927 0.0095 0.0406 1928 0.0065 0.0358 1929 0.0136 0.0640 Eastman King SFR Project #21013 Stormwater Site Plan Stationlo Engineering PLLC WWHM2012 PROJECT REPORT Project Name: 100yr peaksRevl Site Name: Site Address: City Report Date: 10/18/2021 MGS Regoin Puget East Data Start 1901/10/1 Data End : 2058/09/30 DOT Data Number: 03 Version Date: 2019/09/13 Version : 4.2.17 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 C, Forest, Steep .312 Pervious Total 0.312 Impervious Land Use acre Impervious Total 0 Basin Total 0.312 Element Flows To: Surface MITIGATED LAND USE Name : Basin 1 Bypass: No Groundwater: No Interflow Groundwater Eastman King SFR Project #21013 Stormwater Site Plan Stationlo Engineering PLLC Pervious Land Use C, Lawn, Mod acre .178 Pervious Total 0.178 Impervious Land Use acre ROOF TOPS FLAT 0.081 DRIVEWAYS MOD 0.032 SIDEWALKS FLAT 0.021 Impervious Total 0.134 Basin Total 0.312 Element Flows To: Surface Interflow Groundwater ANALYSIS RESULTS Stream Protection Duration Predeveloped Landuse Totals for POC #1 Total Pervious Area:0.312 Total Impervious Area:O Mitigated Landuse Totals for POC #1 Total Pervious Area:0.178 Total Impervious Area:0.134 Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.008564 5 year 0.012959 10 year 0.015303 25 year 0.017665 50 year 0.019058 100 year .020199 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.046698 5 year 0.067618 10 year 0.084415 25 year 0.109366 50 year 0.130916 100 year 55233 Eastman King SFR Project #21013 Stormwater Site Plan Stationlo Engineering PLLC Stream Protection Duration Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1902 0.012 0.048 1903 0.004 0.054 1904 0.009 0.078 1905 0.005 0.032 1906 0.003 0.032 1907 0.014 0.047 1908 0.008 0.038 1909 0.009 0.045 1910 0.014 0.049 1911 0.008 0.047 1912 0.022 0.127 1913 0.010 0.031 1914 0.003 0.171 1915 0.004 0.030 1916 0.006 0.052 1917 0.004 0.027 1918 0.007 0.042 1919 0.005 0.026 1920 0.008 0.041 1921 0.008 0.032 1922 0.009 0.050 1923 0.006 0.040 1924 0.004 0.059 1925 0.004 0.027 1926 0.007 0.052 1927 0.009 0.041 1928 0.007 0.036 1929 0.014 0.065 1930 0.008 0.071 1931 0.008 0.031 1932 0.007 0.038 1933 0.007 0.036 1934 0.017 0.074 1935 0.007 0.028 1936 0.011 0.045 1937 0.011 0.061 1938 0.009 0.030 1939 0.001 0.040 1940 0.008 0.072 1941 0.008 0.066 1942 0.011 0.060 1943 0.004 0.052 1944 0.013 0.081 1945 0.008 0.054 1946 0.007 0.044 1947 0.006 0.031 1948 0.017 0.044 1949 0.015 0.073 1950 0.007 0.031 1951 0.008 0.060 1952 0.025 0.106 1953 0.021 0.093 1954 0.008 0.042 1955 0.006 0.031 Eastman King SFR Project #21013 Stormwater Site Plan Statiomo Engineering PLLC 1956 0.004 0.028 1957 0.009 0.039 1958 0.020 0.057 1959 0.012 0.052 1960 0.005 0.033 1961 0.014 0.130 1962 0.008 0.042 1963 0.004 0.027 1964 0.010 0.133 1965 0.016 0.068 1966 0.004 0.036 1967 0.007 0.059 1968 0.008 0.037 1969 0.007 0.035 1970 0.010 0.053 1971 0.018 0.050 1972 0.021 0.241 1973 0.012 0.081 1974 0.008 0.062 1975 0.019 0.086 1976 0.008 0.075 1977 0.005 0.026 1978 0.017 0.054 1979 0.004 0.049 1980 0.008 0.057 1981 0.008 0.056 1982 0.006 0.038 1983 0.013 0.055 1984 0.005 0.050 1985 0.007 0.066 1986 0.007 0.029 1987 0.014 0.054 1988 0.010 0.031 1989 0.008 0.037 1990 0.009 0.038 1991 0.008 0.055 1992 0.012 0.049 1993 0.010 0.059 1994 0.017 0.041 1995 0.004 0.028 1996 0.015 0.047 1997 0.009 0.037 1998 0.008 0.047 1999 0.000 0.048 2000 0.006 0.048 2001 0.005 0.050 2002 0.012 0.093 2003 0.009 0.036 2004 0.010 0.056 2005 0.010 0.126 2006 0.006 0.041 2007 0.006 0.058 2008 0.008 0.044 2009 0.005 0.035 2010 0.005 0.046 2011 0.006 0.040 2012 0.012 0.044 Eastman King SFR Project #21013 Stormwater Site Plan Statiomo Engineering PLLC 2013 0.006 0.047 2014 0.004 0.034 2015 0.019 0.135 2016 0.003 0.036 2017 0.014 0.067 2018 0.020 0.057 2019 0.026 0.089 2020 0.008 0.063 2021 0.011 0.051 2022 0.004 0.068 2023 0.009 0.072 2024 0.019 0.137 2025 0.008 0.051 2026 0.012 0.056 2027 0.006 0.057 2028 0.003 0.022 2029 0.009 0.035 2030 0.018 0.077 2031 0.005 0.023 2032 0.005 0.036 2033 0.004 0.035 2034 0.006 0.032 2035 0.020 0.051 2036 0.010 0.039 2037 0.002 0.047 2038 0.011 0.052 2039 0.001 0.078 2040 0.005 0.039 2041 0.006 0.043 2042 0.022 0.058 2043 0.009 0.055 2044 0.012 0.044 2045 0.007 0.037 2046 0.008 0.034 2047 0.006 0.041 2048 0.009 0.035 2049 0.009 0.058 2050 0.006 0.035 2051 0.011 0.066 2052 0.005 0.041 2053 0.009 0.036 2054 0.012 0.105 2055 0.004 0.040 2056 0.003 0.057 2057 0.005 0.030 2058 0.006 0.052 Stream Protection Duration Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.0256 0.2405 2 0.0253 0.1714 3 0.0222 0.1368 4 0.0220 0.1349 5 0.0211 0.1326 6 0.0206 0.1304 Eastman King SFR Project #21013 Stormwater Site Plan Statiomo Engineering PLLC 7 0.0201 0.1269 8 0.0199 0.1256 9 0.0197 0.1063 10 0.0193 0.1048 11 0.0190 0.0932 12 0.0188 0.0931 13 0.0180 0.0890 14 0.0177 0.0856 15 0.0170 0.0813 16 0.0169 0.0805 17 0.0165 0.0783 18 0.0165 0.0779 19 0.0156 0.0767 20 0.0154 0.0753 21 0.0148 0.0744 22 0.0143 0.0731 23 0.0141 0.0719 24 0.0139 0.0716 25 0.0138 0.0705 26 0.0138 0.0682 27 0.0136 0.0676 28 0.0133 0.0672 29 0.0129 0.0663 30 0.0123 0.0661 31 0.0123 0.0658 32 0.0123 0.0648 33 0.0119 0.0631 34 0.0118 0.0618 35 0.0117 0.0615 36 0.0116 0.0603 37 0.0116 0.0597 38 0.0116 0.0587 39 0.0115 0.0587 40 0.0111 0.0586 41 0.0111 0.0584 42 0.0110 0.0581 43 0.0107 0.0577 44 0.0106 0.0575 45 0.0105 0.0574 46 0.0103 0.0571 47 0.0102 0.0570 48 0.0102 0.0569 49 0.0099 0.0564 50 0.0097 0.0561 51 0.0097 0.0559 52 0.0096 0.0554 53 0.0095 0.0554 54 0.0094 0.0547 55 0.0093 0.0545 56 0.0093 0.0544 57 0.0092 0.0542 58 0.0092 0.0538 59 0.0091 0.0528 60 0.0091 0.0522 61 0.0089 0.0521 62 0.0089 0.0520 63 0.0088 0.0520 Eastman King SFR Project #21013 Stormwater Site Plan Statiomo Engineering PLLC 64 0.0087 0.0519 65 0.0086 0.0518 66 0.0086 0.0510 67 0.0085 0.0508 68 0.0084 0.0506 69 0.0083 0.0502 70 0.0083 0.0502 71 0.0083 0.0497 72 0.0082 0.0497 73 0.0082 0.0494 74 0.0081 0.0491 75 0.0081 0.0489 76 0.0080 0.0485 77 0.0080 0.0480 78 0.0080 0.0480 79 0.0080 0.0474 80 0.0079 0.0471 81 0.0078 0.0471 82 0.0077 0.0469 83 0.0077 0.0468 84 0.0077 0.0465 85 0.0077 0.0455 86 0.0076 0.0453 87 0.0076 0.0448 88 0.0076 0.0440 89 0.0076 0.0438 90 0.0076 0.0438 91 0.0076 0.0437 92 0.0074 0.0436 93 0.0074 0.0426 94 0.0073 0.0419 95 0.0073 0.0419 96 0.0072 0.0416 97 0.0072 0.0415 98 0.0070 0.0413 99 0.0067 0.0410 100 0.0067 0.0410 101 0.0066 0.0407 102 0.0066 0.0406 103 0.0065 0.0399 104 0.0065 0.0399 105 0.0064 0.0396 106 0.0062 0.0395 107 0.0062 0.0389 108 0.0062 0.0387 109 0.0061 0.0386 110 0.0060 0.0384 111 0.0060 0.0383 112 0.0059 0.0377 113 0.0059 0.0376 114 0.0058 0.0374 115 0.0058 0.0372 116 0.0056 0.0371 117 0.0056 0.0367 118 0.0055 0.0364 119 0.0055 0.0364 120 0.0055 0.0361 Eastman King SFR Project #21013 Stormwater Site Plan Statiomo Engineering PLLC 121 0.0053 0.0358 122 0.0053 0.0356 123 0.0052 0.0355 124 0.0052 0.0355 125 0.0051 0.0355 126 0.0051 0.0355 127 0.0050 0.0354 128 0.0049 0.0350 129 0.0048 0.0348 130 0.0047 0.0345 131 0.0047 0.0337 132 0.0047 0.0335 133 0.0046 0.0333 134 0.0044 0.0321 135 0.0044 0.0318 136 0.0044 0.0318 137 0.0043 0.0317 138 0.0043 0.0314 139 0.0042 0.0314 140 0.0042 0.0311 141 0.0042 0.0310 142 0.0042 0.0309 143 0.0041 0.0307 144 0.0041 0.0301 145 0.0039 0.0299 146 0.0038 0.0297 147 0.0038 0.0292 148 0.0035 0.0284 149 0.0035 0.0277 150 0.0033 0.0275 151 0.0031 0.0271 152 0.0031 0.0270 153 0.0026 0.0268 154 0.0024 0.0265 155 0.0012 0.0262 156 0.0011 0.0234 157 0.0003 0.0225 Stream Protection Duration POC #1 The Facility FAILED Facility FAILED duration standard for 1+ flows. Flow(cfs) Predev Mit Percentage Pass/Fail 0.0043 32292 235065 727 Fail 0.0044 29958 225981 754 Fail 0.0046 27789 217228 781 Fail 0.0047 25841 208916 808 Fail 0.0049 24035 201264 837 Fail 0.0050 22361 193777 866 Fail 0.0052 20848 186951 896 Fail 0.0053 19422 180179 927 Fail 0.0055 18056 173684 961 Fail 0.0056 16878 167353 991 Fail 0.0058 15722 161628 1028 Fail Eastman King SFR Project #21013 Stormwater Site Plan Statiomo Engineering PLLC 0.0059 14671 155957 1063 Fail 0.0061 13724 150507 1096 Fail 0.0062 12816 145278 1133 Fail 0.0064 12006 140433 1169 Fail 0.0065 11236 135699 1207 Fail 0.0067 10526 131020 1244 Fail 0.0068 9859 126671 1284 Fail 0.0070 9254 122267 1321 Fail 0.0071 8670 118083 1361 Fail 0.0073 8180 114064 1394 Fail 0.0074 7729 110266 1426 Fail 0.0076 7294 106632 1461 Fail 0.0077 6865 103054 1501 Fail 0.0079 6501 99641 1532 Fail 0.0080 6127 96393 1573 Fail 0.0082 5797 93255 1608 Fail 0.0083 5500 90227 1640 Fail 0.0085 5239 87420 1668 Fail 0.0086 4975 84722 1702 Fail 0.0088 4713 81915 1738 Fail 0.0089 4484 79327 1769 Fail 0.0091 4278 76850 1796 Fail 0.0092 4051 74373 1835 Fail 0.0094 3853 71896 1865 Fail 0.0095 3696 69584 1882 Fail 0.0097 3505 67381 1922 Fail 0.0098 3321 65290 1965 Fail 0.0100 3148 63308 2011 Fail 0.0101 2978 61436 2062 Fail 0.0103 2846 59509 2090 Fail 0.0104 2712 57638 2125 Fail 0.0106 2592 55766 2151 Fail 0.0107 2486 54219 2180 Fail 0.0108 2388 52534 2199 Fail 0.0110 2291 50833 2218 Fail 0.0111 2204 49308 2237 Fail 0.0113 2112 47778 2262 Fail 0.0114 2035 46413 2280 Fail 0.0116 1955 45026 2303 Fail 0.0117 1880 43688 2323 Fail 0.0119 1818 42405 2332 Fail 0.0120 1751 41112 2347 Fail 0.0122 1693 39856 2354 Fail 0.0123 1611 38640 2398 Fail 0.0125 1541 37539 2436 Fail 0.0126 1470 36421 2477 Fail 0.0128 1406 35480 2523 Fail 0.0129 1352 34417 2545 Fail 0.0131 1289 33399 2591 Fail 0.0132 1229 32430 2638 Fail 0.0134 1190 31533 2649 Fail 0.0135 1142 30635 2682 Fail 0.0137 1090 29821 2735 Fail 0.0138 1037 28956 2792 Fail 0.0140 992 28120 2834 Fail 0.0141 952 27376 2875 Fail 0.0143 922 26617 2886 Fail Eastman King SFR Project #21013 Stormwater Site Plan Statiomo Engineering PLLC 0.0144 891 25896 2906 Fail 0.0146 861 25169 2923 Fail 0.0147 831 24525 2951 Fail 0.0149 800 23853 2981 Fail 0.0150 770 23209 3014 Fail 0.0152 742 22598 3045 Fail 0.0153 708 21960 3101 Fail 0.0155 670 21382 3191 Fail 0.0156 636 20792 3269 Fail 0.0158 608 20209 3323 Fail 0.0159 575 19675 3421 Fail 0.0161 541 19174 3544 Fail 0.0162 506 18701 3695 Fail 0.0164 481 18233 3790 Fail 0.0165 451 17781 3942 Fail 0.0167 431 17319 4018 Fail 0.0168 406 16845 4149 Fail 0.0170 372 16416 4412 Fail 0.0171 355 15987 4503 Fail 0.0173 340 15557 4575 Fail 0.0174 319 15166 4754 Fail 0.0176 305 14792 4849 Fail 0.0177 278 14423 5188 Fail 0.0179 262 14054 5364 Fail 0.0180 242 13702 5661 Fail 0.0182 228 13322 5842 Fail 0.0183 214 12986 6068 Fail 0.0185 199 12651 6357 Fail 0.0186 185 12342 6671 Fail 0.0188 172 12062 7012 Fail 0.0189 161 11786 7320 Fail 0.0191 145 11472 7911 Fail The development has an increase in flow durations from 1/2 Predeveloped 2 year flow to the 2 year flow or more than a 10% increase from the 2 year to the 50 year flow. The development has an increase in flow durations for more than 50% of the flows for the range of the duration analysis. 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. Eastman King SFR Project #21013 Stormwater Site Plan Statiomo Engineering PLLC LID Report LID Technique Used for Total Volume Volume Infiltration Cumulative Percent Water Quality Percent Comment Treatment? Needs Through Volume Volume Volume Water Quality Treatment Facility (ac-ft.) Infiltration Infiltrated Treated (ac-ft) (ac-ft) Total Volume Infiltrated 0.00 0.00 0.00 0.00 0.00 0% No Treat. Credit Compliance with LID Standard 8 Duration Analysis Result = Failed Perind and Impind Changes No changes have been made. Eastman King SFR Project #21013 Stormwater Site Plan Statiomo Engineering PLLC Edmonds Stormwater Addendum Detention Tank Sizing Project is Category z and is exempt from formal flow control per MR #7, but must comply with MR #5 using detention because OSM BMPs are infeasible due to steep slopes and dense soil conditions. In accordance with Edmonds Stormwater Addendum Section 6.3.1, with contributing impervious areas greater than or equal to 1,000 SF, the following sizing requirements apply: Orifice Size: 0.5" 36" diameter detention pipe length L = 0.008*A L = 0.008*5,825 SF L = 46.6 LF Rounded up to 5o LF of 36" diameter detention tank Eastman King SFR Project #21013 Stormwater Site Plan Statiomo Engineering PLLC Rational Method for Estimating Peak Flow Rates Rational Method C: Runoff coefficient I: Peak rainfall intensity (inlhr) A: Drainage subbasin area (acres) Calculate a Cumulative C value for the site: C A (sf) A (acres) C"A Dense forest 0.10 0.0 0 0 Light forest 0.15 0.0 0 0 Pasture 020 0 0 Lawns 0.25 7307.0 0.1677 0.042 Playgrounds 0.30 0.0000 0 Gravel areas 0.80 0.0 0 0 Pavement and roofs 0.90 6185.0 0,141988 0.128 Open water 1.00 0.0 0 0 13492.0 0.3097 0.170 Cc=sum(C"A)IAt Cc: 0.548 Calculate Peak Rainfall Intensity, I =P'i where P=total precip at the project site for the 24-hr duration (see isopluvial maps) and i=unit peak rainfall intensity factor, i=a*Tc"(-b) P a b Tc (min) i 2-yr 1.58 0.58 5 0.621 5-yr 2.33 0.63 0.000 10-yr 2.44 0,64 5 0.871 25-yr 3.5 2,66 0.65 5 0.934 50-yr 2.75 0.65 0.000 100-yr 4 2.61 0.63 5 0.947 Calculate Peak flow rate, Q Q=CIA C I A Q 2-yr 0,548 0.000 0.310 0.000 5-yr 0.548 0.000 0.310 0,000 10-yr 0.548 0.000 0.310 0.000 25-yr 0.548 3.271 0.310 0.555 50-yr 0.548 0.000 0.310 0.000 100-yr 0.548 3.787 0.310 0.643 I a.000 0.000 0.000 3.271 1000 3.787 Eastman King SFR Project #21013 Stormwater Site Plan Statiomo Engineering PLLC Manning's Equation for Estimating Pipe Capacity Manning's Equation for Pipe Capacity, Assuming pipe is flowing 100%full Q= (1.49/n)*A*R"2/3*S"1/2 Pipe diameter: 4 inches Pipe Slope: 0.02 in/in Manning's n: 0.014 A - pi*(D/2)"2 0.0873 5F Pipe X-sectional Area R = A/(pi*D) 0,08333 ft Hydraulic Radius Q = 0.25 CF5 Capacity of the pipe V = 2.87 ft/s Manning's Equation for Pipe Capacity, Assuming pipe is flowing 100%full Q= (1.49/n)*A*R"2/3*S"1/2 Pipe diameter: 6 inches Pipe Slope: 0.02 in/in Manning's n: 0.014 A= pi*(D/2)"2 0.1963 SF Pipe X-sectional Area R = A/(pi*D) 0.125 ft Hydraulic Radius Q= 0.74 CF5 Capacity of the pipe V = 3.76 ft/s 4 Inch Pipe In GPM, this is 112.4655 6 Inch Pipe In GPM, this is 331.5858 Eastman King SFR Project #21013 Stormwater Site Plan Statiomo Engineering PLLC Appendix B Geotechnical Report Eastman King SFR Project #21013 Stormwater Site Plan Statiomo Engineering PLLC COBALT 0 E 0 S C I E N C E S Geotechnical Investigation Proposed Residence 129 Skyline Drive Edmonds, Washington June 3, 2o21 GEOTECHNICAL INVESTIGATION EDMONDS, WASHINGTON Table of Contents 1.o INTRODUCTION............................................................................................................. 1 2.0 PROJECT DESCRIPTION.............................................................................................. 1 3.0 SITE DESCRIPTION....................................................................................................... 1 4.o FIELD INVESTIGATION............................................................................................... 2 4.1.1 Site Investigation Program................................................................................... 2 5.0 SOIL AND GROUNDWATER CONDITIONS.............................................................. 2 5.1.1 Area Geology........................................................................................................ 2 5.1.2 Groundwater........................................................................................................ 2 6.o GEOLOGIC HAZARDS................................................................................................... 3 6.1 Steep Slope Hazard.............................................................................................. 3 a TP-1 NEW.pdf 6.2 Erosion Hazard............................................................................ 6 6.3 Seismic Hazard.................................................................................................... 6 7.o DISCUSSION................................................................................................................... 6 7.1.1 General.................................................................................................................6 8.o RECOMMENDATIONS.................................................................................................. 7 8.1.1 Site Preparation................................................................................................... 7 8.1.2 Temporary Excavations........................................................................................ 7 8.1.3 Erosion and Sediment Control.............................................................................. 8 8.1.4 Foundation Design............................................................................................... 9 8.1.5 Reinforced Concrete Retaining Walls..................................................................10 8.1.6 Stormwater Management....................................................................................11 8.1.7 Slab-on-Grade.....................................................................................................11 8.1.8 Utilities...............................................................................................................12 8.1.9 Groundwater Influence on Construction.............................................................12 9.o CONSTRUCTION FIELD REVIEWS...........................................................................12 moCLOSURE...................................................................................................................13 GEOTECHNICAL INVESTIGATION SEATTLE, WASHINGTON June 3, 2021 Table of Contents (Continued) LIST OF APPENDICES Appendix A — Statement of General Conditions Appendix B — Figures Appendix C — Exploration Logs GEOTECHNICAL INVESTIGATION EDMONDS, WASHINGTON June 3, 2021 i.o Introduction COBALT GEOSCIENCES In accordance with your authorization, Cobalt Geosciences, LLC (Cobalt) has completed a geotechnical investigation for the proposed residence located at 129 Skyline Drive in Edmonds, Washington (Figure 1). The purpose of the geotechnical investigation was to identify subsurface conditions and to provide preliminary geotechnical recommendations for foundation design, retaining walls, earthwork, soil compaction, and suitability of the on -site soils for use as fill. The scope of work for the geotechnical investigation consisted of a site investigation followed by engineering analyses to prepare this report. Recommendations presented herein pertain to various geotechnical aspects of the proposed development, including foundation design, retaining walls, drainage, and earthwork. 2.0 Project Description The project includes construction of a new residence within the property. Based on topography, a daylight basement will likely be incorporated into the design. A new driveway will extend into the property from the north. We anticipate that structural loads will generally be light and site grading will include cuts and fills on the order of io feet or less for daylight basement construction. We should be provided with the plans once they become available so that we may update our recommendations, if necessary. Stormwater runoff will be infiltrated, if determined to be feasible. 3.0 Site Description The site is located at 129 Skyline Drive in Edmonds, Washington (Figure 1). The property consists of one irregularly shaped parcel (No. 00423000005300) with a total area of 0.32 acres. The property is currently undeveloped and vegetated with grasses. The site slopes downward from east to west at magnitudes of io to about 6o percent and total relief of about 27 feet. The steeper slopes are located in the western third to half of the property. There is a rockery in the western half of the property south of the subject property. This wall is 4 to io feet tall near the southwest corner of the subject property. The site is bordered to the north and east by Skyline Drive, to the south by a residence, and to the west by right-of-way and residences. PO Box 82243 Kenmore, WA 98028 cobaltgeoRgmail.com 2o6-331-1097 GEOTECHNICAL INVESTIGATION EDMONDS, WASHINGTON June 3, 2021 4.o Field Investigation 4.1.1 Site Investigation Program COBALT GEOSCIENCES The geotechnical field investigation program was completed on December 1, 202o and included excavating two test pits within the property for subsurface analysis. The soils encountered were logged in the field and are described in accordance with the Unified Soil Classification System (USCS). A Cobalt Geosciences field representative conducted the explorations, collected disturbed soil samples, classified the encountered soils, kept a detailed log of the explorations, and observed and recorded pertinent site features. The results of the test pit sampling are presented on the exploration logs enclosed in Appendix C. 5.0 Soil and Groundwater Conditions 5aa Area Geology The site lies within the Puget Lowland. The lowland is part of a regional north -south trending trough that extends from southwestern British Columbia to near Eugene, Oregon. North of Olympia, Washington, this lowland is glacially carved, with a depositional and erosional history including at least four separate glacial advances/retreats. The Puget Lowland is bounded to the west by the Olympic Mountains and to the east by the Cascade Range. The lowland is filled with glacial and non -glacial sediments consisting of interbedded gravel, sand, silt, till, and peat lenses. The Geologic Map of the Edmonds East and West Quadrangle, indicates that the site is near the contacts between Vashon Glacial Till and Vashon Advance Outwash. Vashon Advance Outwash consists of sand with variable amounts of gravel which are generally dense to very dense and relatively permeable. Vashon Glacial Till includes a mixture of silt, sand, gravel, and clay. These deposits are typically dense to very dense below a weathered zone. Explorations The test pits encountered approximately 6 inches of topsoil and grass underlain by approximately 3 to 5 feet of loose to medium dense, silty -fine to medium grained sand with gravel (Fill). This layer was underlain by medium dense to dense, silty -fine to medium grained sand with gravel (Glacial Till), which continued to the termination depths of the test pits. 5.1.2 Groundwater Groundwater was not encountered during our investigation. be encountered within the dense to very dense glacial till encountered, it would be expected to be light in volume. Light amounts of perched groundwater could during the wet season. If groundwater is 2 PO Box 82243 Kenmore, WA 98028 cobaltgeoRgmail.com 2o6-331-1097 GEOTECHNICAL INVESTIGATION EDMONDS, WASHINGTON June 3, 2021 COBALT GEOSCIENCES Water table elevations often fluctuate over time. The groundwater level will depend on a variety of factors that may include seasonal precipitation, irrigation, land use, climatic conditions and soil permeability. Water levels at the time of the field investigation may be different from those encountered during the construction phase of the project. 6.o Geologic Hazards 6.1 Steep Slope Hazards The site contains local steep slope areas based on magnitude and height. These areas are underlain by fill and glacial till. During our site visit, we observed the areas for signs of instability. We did not observe areas of erosion, landslide activity, or other signs of instability or historic landslide activity. The site appears stable and is underlain by dense glacial till which is not highly susceptible to global instability. The proposed construction includes a new residence with daylight basement level. We recommend a minimum effective setback of io feet from slopes with magnitudes of 30 percent or greater. The effective setback is the horizontal distance measured from the outside of the foundation areas laterally to the adjacent slope face. Deeper foundation embedment may be required for the footings in the western margin of the new residence (downslope side). Relevant code items with discussion for steep slope and erosion hazards are as follows: 23.80.o6o Development standards — General requirements. A. Alterations of geologically hazardous areas or associated buffers may only occur for activities that: 1. Will not increase the threat of the geological hazard to adjacent properties beyond predevelopment conditions; 2. Will not adversely impact other critical areas; 3. Are designed so that the hazard to the project is eliminated or mitigated to a level equal to or less than predevelopment conditions; and 4. Are certified as safe as designed and under anticipated conditions by a qualified engineer or geologist, licensed in the state of Washington. The site is situated within and contains moderately steep slope areas that were created over time through natural erosion along with historic grading activities. The site is not situated within an active or historic landslide and the risk of landslide activity is ver low. ow. The proposed residence will not increase the threat of geologic hazards on adjacent properties, will not impact other critical areas, and are safe as designed under anticipated conditions. The level of risk due to the proposed development will be the same or lower than what is currently present provided temporary and permanent runoff is fully controlled. 3 PO Box 82243 Kenmore, WA 98028 cobaltgeoRgmail.com 206-331-1097 COBALT GEOTECHNICAL INVESTIGATION GEOSCIENCES EDMONDS, WASHINGTON June 3, 2021 23.80.07o Development standards — Specific hazards. A. Erosion and Landslide Hazard Areas. Activities on sites containing erosion or landslide hazards shall meet the requirements of ECDC 2,1.80.o6o, Development standards — General requirements, and the specific following requirements: 1. Minimum Building Setback. The minimum setback shall be the distance required to ensure the proposed structure will not be at risk from landslides for the life of the structure, considered to be 120 years, and will not cause an increased risk of landslides taking place on or off the site. A setback shall be established from all edges of landslide hazard areas. The size of the setback shall be determined by the director consistent with recommendations provided in the geotechnical report to eliminate or minimize the risk of property damage, death, or injury resulting from landslides caused in whole or part by the development, based upon review of and concurrence with a critical areas report prepared by a qualified professional; A minimum effective building setback of io feet is recommended. 2. Buffer Requirements. A buffer may be established with specific requirements and limitations, including but not limited to, drainage, grading, irrigation, and vegetation. Buffer requirements shall be determined by the director consistent with recommendations provided in the geotechnical report to eliminate or minimize the risk of property damage, death, or injury resulting from landslides caused in whole or part by activities within the buffer area, based upon review of and concurrence with a critical areas report prepared by a qualified professional; The site has been previously graded and does not contain areas of native vegetation. No specific buffer is required from a geotechnical standpoint. We recommend that all site soils be vegetated or protected from erosion through placement of surface landscaping materials/hardscapes. 3. Alterations. Alterations of an erosion or landslide hazard area, minimum building setback and/or buffer may only occur for activities for which a hazards analysis is submitted and certifies that: a. The alteration will not increase surface water discharge or sedimentation to adjacent properties beyond predevelopment conditions; b. The alteration will not decrease slope stability on adjacent properties; and c. Such alterations will not adversely impact other critical areas; Provided earthwork activities are Derformed in accordance with the aDDroved Dlans, all runoff is full control, and periodic geotechnical oversight is performed, the development will not decrease slope stability on adjacent properties, will not increase surface water discharge or sedimentation bg and current levels, and will not impact other critical areas. Temporary and permanent erosion and sediment control devices should be in at all times during construction. 4. Design Standards within Erosion and Landslide Hazard Areas. Development within an erosion or landslide hazard area and/or buffer shall be designed to meet the following basic requirements unless it can be demonstrated that an alternative design that deviates from one or more of these standards provides greater long-term slope stability while meeting all other provisions of this title. The requirement for long-term slope stability shall exclude designs that require regular and periodic maintenance to maintain their level of function. The basic development design standards are: 4 PO Box 82243 Kenmore, WA 98028 cobaltgeoRgmail.com 206-331-1097 GEOTECHNICAL INVESTIGATION EDMONDS, WASHINGTON June 3, 2021 COBALT GEOSCIENCES a. The proposed development shall not decrease the factor of safety for landslide occurrences below the limits of 1.5 for static conditions and 1.2 for dynamic conditions. If stability at the proposed development site is below these limits, the proposed development shall provide practicable approaches to reduce risk to human safety and improve the factor of safety for landsliding. In no case shall the existing factor of safety be reduced for the subject property or adjacent properties; b. Structures and improvements shall be clustered to avoid geologically hazardous areas and other critical areas; c. Structures and improvements shall minimize alterations to the natural contour of the slope, and foundations shall be tiered where possible to conform to existing topography; d. Structures and improvements shall be located to preserve the most critical portion of the site and its natural landforms and vegetation; e. The proposed development shall not result in greater risk or a need for increased buffers on neighboring properties; f. The use of retaining walls that allow the maintenance of existing natural slope area is preferred over graded artificial slopes; and g. Development shall be designed to minimize impervious lot coverage; Based on site topography, underling soil conditions, and our experience with similar projects, the estimated static and seismic factors of safety are well above minimum requirements. The factor of safety for landslide activity will not be affected by the proposed development. The building loads and where they will be located will not affect global stability. Performed with proper erosion control and engineering controls, the proposed development does not pose a risk to critical areas or the need to increase buffers on adjacent properties. 5. Vegetation Retention. Unless otherwise provided or as part of an approved alteration, removal of vegetation from an erosion or landslide hazard area or related buffer shall be prohibited; 6. Seasonal Restriction. Clearing shall be allowed only from May 1st to October 1st of each year; provided, that the director may extend or shorten the dry season on a case -by -case basis depending on actual weather conditions, except that timber harvest, not including brush clearing or stump removal, may be allowed pursuant to an approved forest practice permit issued by the city of Edmonds or the Washington State Department of Natural Resources; 7. Point Discharges. Point discharges from surface water facilities and roof drains onto or upstream from an erosion or landslide hazard area shall be prohibited except as follows: a. Conveyed via continuous storm pipe downslope to a point where there are no erosion hazard areas downstream from the discharge; b. Discharged at flow durations matching predeveloped conditions, with adequate energy dissipation, into existing channels that previously conveyed storm water runoff in the predeveloped state; or c. Dispersed discharge upslope of the steep slope onto a low -gradient, undisturbed buffer demonstrated to be adequate to infiltrate all surface and storm water runoff, and where it can be demonstrated that such discharge will not increase the saturation of the slope; and 5 PO Box 82243 Kenmore, WA 98028 cobaltgeoRgmail.com 2o6-331-1097 GEOTECHNICAL INVESTIGATION EDMONDS, WASHINGTON June 3, 2021 COBALT GEOSCIENCES We concur with the above code items and have no additional comments at this time. 6.2 Erosion Hazard The Natural Resources Conservation Services (NRCS) maps for Snohomish County indicate that the property is underlain by Alderwood-Everett gravelly sandy loams (25 to 70 percent slopes). These soils can have a severe erosion potential when exposed. These soils are included in the Edmonds Municipal Code section 23.80.020 under Al. It is our opinion that typical erosion control measures will be suitable to limit/reduce erosion potential during construction. It is our opinion that soil erosion potential at this project site can be reduced through landscaping and surface water runoff control. Typically, erosion of exposed soils will be most noticeable during periods of rainfall and may be controlled by the use of normal temporary erosion control measures, such as silt fences, hay bales, mulching, control ditches and diversion trenches. The typical wet weather season, with regard to site grading, is from October 31st to April 1st. Erosion control measures should be in place before the onset of wet weather. 6.3 Seismic Hazard The overall subsurface profile corresponds to a Site Class D as defined by Table 1613.5.2 of the 2015 International Building Code (2015 IBC). A Site Class D applies to an overall profile consisting of medium dense or stiff soils within the upper too feet. We referenced the U.S. Geological Survey (USGS) Earthquake Hazards Program Website to obtain values for Ss, S,, FQ, and F,,. The USGS website includes the most updated published data on seismic conditions. The site specific seismic design parameters and adjusted maximum spectral response acceleration parameters are as follows: PGA (Peak Ground Acceleration, in percent of g) Ss 127.30% of g S, 49.8o% of g FA 1.00 Fv 1.502 Additional seismic considerations include liquefaction potential and amplification of ground motions by soft/loose soil deposits. The liquefaction potential is highest for loose sand with a high groundwater table. The relatively dense glacially consolidated materials that underlie the site have a low potential for liquefaction. 6 PO Box 82243 Kenmore, WA 98028 cobaltgeoRgmail.com 2o6-331-1097 GEOTECHNICAL INVESTIGATION EDMONDS, WASHINGTON June 3, 2021 7.o DISCUSSION 7.1.1 General COBALT GEOSCIENCES It is our opinion that the proposed residence may be supported on a shallow foundation system bearing on medium dense or firmer native soils. These soils will likely be encountered 3.5 to 5.5 feet below existing site elevations in areas underlain by loose native soils and fill materials. The basement excavation work will likely remove most of the undocumented fill that appears to be present over much of the site. Local overexcavation of fill will likely be necessary for shallow foundation elements near the low side of the building (west end). We recommend a minimum effective building setback of io feet from any slopes of 30 percent magnitude or greater. This may require greater foundation embedment along the western margin of the residence. It is our opinion that the proposed development will not increase the potential for soil movement or erosion at the property, and the risk of damage to the proposed development and adjacent properties will be minimal, provided the work is performed in accordance with approved plans and our recommendations and is monitored by the geotechnical engineer. 8.o Recommendations 8.m Site Preparation Trees, shrubs and other vegetation should be removed prior to stripping of surficial organic -rich soil. Based on observations from the site investigation program, it is anticipated that the stripping depth will range from 6 to 18 inches. Deeper excavations should be expected below larger vegetation and where undocumented fill is present. The near -surface soils consist of silty -sand with gravel (Fill and Native Soils). These soils are suitable for use as structural fill if they are compacted when the moisture levels are within a few percent of optimum. This is typically only possible during mid -late summer and early fall when there are extended periods of warm, dry weather. All fill soils should be compacted when they are within 3 percent of the optimum moisture as determined by the ASTM D 1557 proctor analysis test. Note that existing fill may need to be exported as fill typically has higher moisture contents Imported structural fill should consist of a sand and gravel mixture with a maximum grain size of 3 inches and less than 5 percent fines (material passing the U.S. Standard No. 200 Sieve). Structural fill should be placed in maximum lift thicknesses of 12 inches and should be compacted to a minimum of 95 percent of the modified proctor maximum dry density, as determined by the ASTM D 1557 test method. 8.1.2 Temporary Excavations Based on our understanding of the project, we anticipate that the grading could include local cuts on the order of approximately 10 feet or less for basement foundation placement, if proposed. These excavations should be sloped no steeper than 1.5H:1V (Horizontal:Vertical) in loose native or fill soils (upper 3 to 5 feet), 1H:1V in medium dense or firmer native soils and 3/4H:1V in dense to very dense native soils. If an 7 PO Box 82243 Kenmore, WA 98028 cobaltgeoRgmail.com 2o6-331-1097 GEOTECHNICAL INVESTIGATION EDMONDS, WASHINGTON June 3, 2021 COBALT GEOSCIENCES excavation is subject to heavy vibration or surcharge loads, we recommend that the excavations be sloped no steeper than 1.5H:1V, where room permits. The geotechnical engineer should be on site during excavation work to determine safe temporary slope angles. If the proposed residence will have a basement level and be located within about 10 feet of the south or east property lines, temporary shoring will likely be required. We can provide shoring recommendations upon request. Temporary cuts should be in accordance with the Washington Administrative Code (WAC) Part N, Excavation, Trenching, and Shoring. Temporary slopes should be visually inspected daily by a qualified person during construction activities and the inspections should be documented in daily reports. The contractor is responsible for maintaining the stability of the temporary cut slopes and reducing slope erosion during construction. Temporary cut slopes should be covered with visqueen to help reduce erosion during wet weather, and the slopes should be closely monitored until the permanent retaining systems or slope configurations are complete. Materials should not be stored or equipment operated within 10 feet of the top of any temporary cut slope. Soil conditions may not be completely known from the geotechnical investigation. In the case of temporary cuts, the existing soil conditions may not be completely revealed until the excavation work exposes the soil. Typically, as excavation work progresses the maximum inclination of temporary slopes will need to be re- evaluated by the geotechnical engineer so that supplemental recommendations can be made. Soil and groundwater conditions can be highly variable. Scheduling for soil work will need to be adjustable, to deal with unanticipated conditions, so that the project can proceed and required deadlines can be met. If any variations or undesirable conditions are encountered during construction, we should be notified so that supplemental recommendations can be made. If room constraints or groundwater conditions do not permit temporary slopes to be cut to the maximum angles allowed by the WAC, temporary shoring systems may be required. The contractor should be responsible for developing temporary shoring systems, if needed. We recommend that Cobalt Geosciences and the project structural engineer review temporary shoring designs prior to installation, to verify the suitability of the proposed systems. 8.1.3 Erosion and Sediment Control Erosion and sediment control (ESC) is used to reduce the transportation of eroded sediment to wetlands, streams, lakes, drainage systems, and adjacent properties. Erosion and sediment control measures should be implemented and these measures should be in general accordance with local regulations. At a minimum, the following basic recommendations should be incorporated into the design of the erosion and sediment control features for the site: • Schedule the soil, foundation, utility, and other work requiring excavation or the disturbance of the site soils, to take place during the dry season (generally May through September). However, provided precautions are taken using Best Management Practices (BMP's), grading activities can be completed during the wet season (generally October through April). • All site work should be completed and stabilized as quickly as possible. 8 PO Box 82243 Kenmore, WA 98028 cobaltgeoRgmail.com 2o6-331-1097 GEOTECHNICAL INVESTIGATION EDMONDS, WASHINGTON June 3, 2021 COBALT GEOSCIENCES • Additional perimeter erosion and sediment control features may be required to reduce the possibility of sediment entering the surface water. This may include additional silt fences, silt fences with a higher Apparent Opening Size (AOS), construction of a berm, or other filtration systems. • Any runoff generated by dewatering discharge should be treated through construction of a sediment trap if there is sufficient space. If space is limited other filtration methods will need to be incorporated. 8.1.4 Foundation Design The proposed residence may be supported on a shallow spread footing foundation system bearing on undisturbed medium dense or firmer native soils or on properly compacted structural fill placed on the suitable native soils. If structural fill is used to support foundations, then the zone of structural fill should extend beyond the faces of the footing a lateral distance at least equal to the thickness of the structural fill. For shallow foundation support, we recommend widths of at least 16 and 24 inches, respectively, for continuous wall and isolated column footings supporting the proposed structures. Provided that the footings are supported as recommended above, a net allowable bearing pressure of 2,000 pounds per square foot (psf) may be used for design. A 1/3 increase in the above value may be used for short duration loads, such as those imposed by wind and seismic events. Structural fill placed on bearing, native subgrade should be compacted to at least 95 percent of the maximum dry density based on ASTM Test Method D1557. Footing excavations should be inspected to verify that the foundations will bear on suitable material. Exterior footings should have a minimum depth of 18 inches below pad subgrade (soil grade) or adjacent exterior grade, whichever is lower. Interior footings should have a minimum depth of 12 inches below pad subgrade (soil grade) or adjacent exterior grade, whichever is lower. If constructed as recommended, the total foundation settlement is not expected to exceed 1 inch. Differential settlement, along a 25-foot exterior wall footing, or between adjoining column footings, should be less than 1/2 inch. This translates to an angular distortion of 0.002. Most settlement is expected to occur during construction, as the loads are applied. However, additional post -construction settlement may occur if the foundation soils are flooded or saturated. All footing excavations should be observed by a qualified geotechnical consultant. Resistance to lateral footing displacement can be determined using an allowable friction factor of 0.40 acting between the base of foundations and the supporting subgrades. Lateral resistance for footings can also be developed using an allowable equivalent fluid passive pressure of 250 pounds per cubic foot (pcf) acting against the appropriate vertical footing faces (neglect the upper 12 inches below grade in exterior areas). The allowable friction factor and allowable equivalent fluid passive pressure values include a factor of safety of 1.5. The frictional and passive resistance of the soil may be combined without reduction in determining the total lateral resistance. A 1/3 increase in the above values may be used for short duration transient loads. Care should be taken to prevent wetting or drying of the bearing materials during construction. Any extremely wet or dry materials, or any loose or disturbed materials at the bottom of the footing excavations, should be removed prior to placing concrete. The potential for wetting or drying of the bearing materials 9 PO Box 82243 Kenmore, WA 98028 cobaltgeoRgmail.com 2o6-331-1097 GEOTECHNICAL INVESTIGATION EDMONDS, WASHINGTON June 3, 2021 COBALT GEOSCIENCES can be reduced by pouring concrete as soon as possible after completing the footing excavation and evaluating the bearing surface by the geotechnical engineer or his representative. 8.1.5 Reinforced Concrete Retaining Walls The following table, titled Wall Design Criteria, presents the recommended soil related design parameters for retaining walls with a level backslope. Contact Cobalt if an alternate retaining wall system is used. Wall Design Criteria "At -rest" Conditions (Lateral Earth Pressure — EFD+) 55 pcf (Equivalent Fluid Density) "Active" Conditions (Lateral Earth Pressure — EFD+) 35 pcf (Equivalent Fluid Density) Seismic Increase for "At -rest" Conditions (Lateral Earth Pressure) 21H* (Uniform Distribution) 1 in 2,500 year event Seismic Increase for "At -rest" Conditions (Lateral Earth Pressure) 14H* (Uniform Distribution) 1 in 500 year event Seismic Increase for "Active" Conditions (Lateral Earth Pressure) 7H* (Uniform Distribution) Passive Earth Pressure on Low Side of Wall (Allowable, includes F.S. = 1.5) Level Ground; Neglect upper 2 feet, then 250 pcf EFD+ Soil -Footing Coefficient of Sliding Friction (Allowable; includes F.S. = 1.5) 0.40 *H is the height of the wall; Increase based on one in 2,500 year seismic event (2 percent probability of being exceeded in 50 years), + EFD — Equivalent Fluid Density The stated lateral earth pressures do not include the effects of hydrostatic pressure generated by water accumulation behind the retaining walls. Uniform horizontal lateral active and at -rest pressures on the retaining walls from vertical surcharges behind the wall may be calculated using active and at -rest lateral earth pressure coefficients of 0.3 and 0.5, respectively. The soil unit weight of 125 pcf may be used to calculate vertical earth surcharges. To reduce the potential for the buildup of water pressure against the walls, continuous footing drains (with cleanouts) should be provided at the bases of the walls. The footing drains should consist of a minimum fl- inch diameter perforated pipe, sloped to drain, with perforations placed down and enveloped by a minimum 6 inches of pea gravel in all directions. The backfill adjacent to and extending a lateral distance behind the walls at least 2 feet should consist of free -draining granular material. All free draining backfill should contain less than 3 percent fines (passing the U.S. Standard No. 200 Sieve) based upon the fraction passing the U.S. Standard No. 4 Sieve with at least 30 percent of the material being retained on the U.S. Standard No. 4 Sieve. The primary purpose of 10 PO Box 82243 Kenmore, WA 98028 cobaltgeo(d)gmail.com 2o6-331-1097 GEOTECHNICAL INVESTIGATION EDMONDS, WASHINGTON June 3, 2021 COBALT GEOSCIENCES the free -draining material is the reduction of hydrostatic pressure. Some potential for the moisture to contact the back face of the wall may exist, even with treatment, which may require that more extensive waterproofing be specified for walls, which require interior moisture sensitive finishes. We recommend that the backfill be compacted to at least go percent of the maximum dry density based on ASTM Test Method D1557. In place density tests should be performed to verify adequate compaction. Soil compactors place transient surcharges on the backfill. Consequently, only light hand operated equipment is recommended within 3 feet of walls so that excessive stress is not imposed on the walls. 8.1.6 Stormwater Management The site is underlain by fill which is underlain by weathered and unweathered glacial till. The glacial till has a low permeability which decreases with depth as soil density increases. The site contains steep slope areas which extend off site onto adjacent properties to the west and south. We do not recommend utilizing infiltration or dispersion devices due to the soil conditions and steep topography. We recommend collection of all runoff from new impervious surfaces with direct connection to City stormwater infrastructure. We can provide additional recommendations upon request. 8-1-7 Slab -on -Grade We recommend that the upper 12 inches of the native soils within slab areas be re -compacted to at least 95 percent of the modified proctor (ASTM D1557 Test Method). If loose fill soils or deep topsoil/roots are encountered, they should be removed and replaced with structural fill. Often, a vapor barrier is considered below concrete slab areas. However, the usage of a vapor barrier could result in curling of the concrete slab at joints. Floor covers sensitive to moisture typically requires the usage of a vapor barrier. A materials or structural engineer should be consulted regarding the detailing of the vapor barrier below concrete slabs. Exterior slabs typically do not utilize vapor barriers. The American Concrete Institutes ACI 36oR-o6 Design of Slabs on Grade and ACI 302.1R-04 Guide for Concrete Floor and Slab Construction are recommended references for vapor barrier selection and floor slab detailing. Slabs on grade may be designed using a coefficient of subgrade reaction of 18o pounds per cubic inch (pci) assuming the slab -on -grade base course is underlain by structural fill placed and compacted as outlined in Section 8.1. A minimum 4 inch thick capillary break is recommended over the prepared subgrade. This should consist of pea gravel or 5/8 inch clean angular rock. A perimeter drainage system is recommended unless interior slab areas are elevated a minimum of 12 inches above adjacent exterior grades. If installed, a perimeter drainage system should consist of a 4-inch diameter perforated drain pipe surrounded by a minimum 6 inches of drain rock wrapped in a non -woven geosynthetic filter fabric to reduce migration of soil particles into the drainage system. The perimeter drainage system should discharge by gravity flow to a suitable stormwater system. 11 PO Box 82243 Kenmore, WA 98028 cobaltgeoRgmail.com 2o6-331-1097 GEOTECHNICAL INVESTIGATION EDMONDS, WASHINGTON June 3, 2021 COBALT GEQSCIENCES Exterior grades surrounding buildings should be sloped at a minimum of one percent to facilitate surface water flow away from the building and preferably with a relatively impermeable surface cover immediately adjacent to the building. 8.1.8 Groundwater Influence on Construction Groundwater was not encountered in the test pits. There is a very slight chance that light volumes of perched groundwater could be encountered in the dense native soils. If groundwater is encountered during construction, we anticipate that sump excavations and small diameter pumps systems will adequately de -water short-term excavations, if required. Any system should be designed by the contractor. We can provide additional recommendations upon request. 8a.9 Utilities Utility trenches should be excavated according to accepted engineering practices following OSHA (Occupational Safety and Health Administration) standards, by a contractor experienced in such work. The contractor is responsible for the safety of open trenches. Traffic and vibration adjacent to trench walls should be reduced; cyclic wetting and drying of excavation side slopes should be avoided. Depending upon the location and depth of some utility trenches, groundwater flow into open excavations could be experienced, especially during or shortly following periods of precipitation. In general, sandy and silty soils were encountered at shallow depths in the explorations at this site. These soils have variable cohesion and density and may have a tendency to cave or slough in excavations. Shoring or sloping back trench sidewalls is required within these soils in excavations greater than 4 feet deep. All utility trench backfill should consist of imported structural fill or suitable on -site soils. Utility trench backfill placed in or adjacent to buildings and exterior slabs should be compacted to at least 95 percent of the maximum dry density based on ASTM Test Method D1557. The upper 5 feet of utility trench backfill placed in pavement areas should be compacted to at least 95 percent of the maximum dry density based on ASTM Test Method D1557. Below 5 feet, utility trench backfill in pavement areas should be compacted to at least 90 percent of the maximum dry density based on ASTM Test Method D1557. Pipe bedding should be in accordance with the pipe manufacturer's recommendations. The contractor is responsible for removing all water -sensitive soils from the trenches regardless of the backfill location and compaction requirements. Depending on the depth and location of the proposed utilities, we anticipate the need to re -compact existing fill soils below the utility structures and pipes. The contractor should use appropriate equipment and methods to avoid damage to the utilities and/or structures during fill placement and compaction procedures. 9.o Construction Field Reviews Cobalt Geosciences should be retained to provide part time field review during construction in order to verify that the soil conditions encountered are consistent with our design assumptions and that the intent of our recommendations is being met. This will require field and engineering review to: 12 PO Box 82243 Kenmore, WA 98028 cobaltgeoRgmail.com 2o6-331-1097 COBALT GEOTECHNICAL INVESTIGATION GEOSCIENCES EDMONDS, WASHINGTON June 3, 2021 ■ Monitor and test structural fill placement and soil compaction ■ Monitor temporary excavation stability ■ Verify footing drain installation ■ Observe bearing capacity at footing locations Geotechnical design services should also be anticipated during the subsequent final design phase to support the structural design and address specific issues arising during this phase. Field and engineering review services will also be required during the construction phase in order to provide a Final Letter for the project. mo Closure This report was prepared for the exclusive use of Sue Eastman -King and her appointed consultants. Any use of this report or the material contained herein by third parties, or for other than the intended purpose, should first be approved in writing by Cobalt Geosciences, LLC. The recommendations contained in this report are based on assumed continuity of soils with those of our test holes, and assumed structural loads. Cobalt Geosciences should be provided with final architectural and civil drawings when they become available in order that we may review our design recommendations and advise of any revisions, if necessary. Use of this report is subject to the Statement of General Conditions provided in Appendix A. It is the responsibility of Sue Eastman -King who is identified as "the Client" within the Statement of General Conditions, and its agents to review the conditions and to notify Cobalt Geosciences should any of these not be satisfied. Respectfully submitted, Cobalt Geosciences, LLC Original signed by: VkONY WA -d 2513-`' 00 54896 ��' lST ER�-�� d r s e 12/16/2020 Phil Haberman, PE, LG, LEG Principal 13 PO Box 82243 Kenmore, WA 98028 cobaltgeoRgmail.com 2o6-331-1097 APPENDIX A Statement of General Conditions Statement of General Conditions USE OF THIS REPORT: This report has been prepared for the sole benefit of the Client or its agent and may not be used by any third party without the express written consent of Cobalt Geosciences and the Client. Any use which a third party makes of this report is the responsibility of such third party. BASIS OF THE REPORT: The information, opinions, and/or recommendations made in this report are in accordance with Cobalt Geosciences present understanding of the site specific project as described by the Client. The applicability of these is restricted to the site conditions encountered at the time of the investigation or study. If the proposed site specific project differs or is modified from what is described in this report or if the site conditions are altered, this report is no longer valid unless Cobalt Geosciences is requested by the Client to review and revise the report to reflect the differing or modified project specifics and/or the altered site conditions. STANDARD OF CARE: Preparation of this report, and all associated work, was carried out in accordance with the normally accepted standard of care in the state of execution for the specific professional service provided to the Client. No other warranty is made. INTERPRETATION OF SITE CONDITIONS: Soil, rock, or other material descriptions, and statements regarding their condition, made in this report are based on site conditions encountered by Cobalt Geosciences at the time of the work and at the specific testing and/or sampling locations. Classifications and statements of condition have been made in accordance with normally accepted practices which are judgmental in nature; no specific description should be considered exact, but rather reflective of the anticipated material behavior. Extrapolation of in situ conditions can only be made to some limited extent beyond the sampling or test points. The extent depends on variability of the soil, rock and groundwater conditions as influenced by geological processes, construction activity, and site use. VARYING OR UNEXPECTED CONDITIONS: Should any site or subsurface conditions be encountered that are different from those described in this report or encountered at the test locations, Cobalt Geosciences must be notified immediately to assess if the varying or unexpected conditions are substantial and if reassessments of the report conclusions or recommendations are required. Cobalt Geosciences will not be responsible to any party for damages incurred as a result of failing to notify Cobalt Geosciences that differing site or sub -surface conditions are present upon becoming aware of such conditions. PLANNING, DESIGN, OR CONSTRUCTION: Development or design plans and specifications should be reviewed by Cobalt Geosciences, sufficiently ahead of initiating the next project stage (property acquisition, tender, construction, etc), to confirm that this report completely addresses the elaborated project specifics and that the contents of this report have been properly interpreted. Specialty quality assurance services (field observations and testing) during construction are a necessary part of the evaluation of sub -subsurface conditions and site preparation works. Site work relating to the recommendations included in this report should only be carried out in the presence of a qualified geotechnical engineer; Cobalt Geosciences cannot be responsible for site work carried out without being present. 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Box 82243 Kenmore, WA 98028 COBALT 129 Skyline Drive MAP (2o6) 331-1097 G E • S C I E N C k S Edmonds, Washington FIGURE i t^'ww.cobaltgeo.com cobaltgeoogmail.com Approximate TP_ Test Pit Location Proposed Residence 129 Skyline Drive Edmonds, Washington SITE PLAN FIGURE 2 N A Cobalt Geosciences, LLC P.O. Box 82243 Kenmore, WA 98028 (206) 331-1097 www.cobaltgeo.com cobaltgeoogmail.com APPENDIX C Exploration Logs Test Pit TP-1 Date: December 1, 2020 Depth. 9' Groundwater: None Contractor: Jim Elevation: Logged By: PH Checked By: SC a)J0 0) o Q Moisture Content (%) Plastic 1 Liquid � U E 3 Limit Limit } CI a a, L N Material Description c ? o DCP Equivalent N-Value o C 0 10 20 30 40 50 ------ — -- To�soilVetation -------------------------------- 1 SM Loose to medium dense, silty -fine to medium grained sand with gravel dark yellowish brown to grayish brown, moist. 2 (Fill) 3 ------ q ---- -- SM --------------------------------------------- Medium dense to dense, silty -fine to medium grained sand with gravel grayish brown, moist. 5 (Glacial Till) 6 8 End of Test Pit 9' 10 Test Pit TP-2 Date: December 1, 2020 Depth: 9' Groundwater: None Contractor: Jim Elevation: Logged By: PH Checked By: SC N 0 o N Moisture Content (%) u E 3 Plastic 1 Liquid Limit Limit L L N Material Description DCP Equivalent N-Value Q o �, ? o C 0 10 20 30 40 5 -- TopsoilVegetation ________________________________ 1 SM Loose to medium dense, silty -fine to medium grained sand with gravel dark yellowish brown to grayish brown, moist. 2 (Fill) 3 4 5 ------- 6 ---- -- SM --------------------------------------------- Medium dense to dense, silty -fine to medium grained sand with gravel grayish brown, moist. (Glacial Till) 8 End of Test Pit 9' 10 Cobalt Geosciences, LLC Proposed Residence P.O. Box 82243 Test Pit Kenmore, WA 98028 COBALT129 Skyline Drive (2o6) 331-1097 G E • S C I E N C k S Edmonds, Washington Logs www.cobaltgeo.com cobaltgeoogmail.com Appendix C Construction SWPPP Eastman King SFR Project #21013 Stormwater Site Plan Statiomo Engineering PLLC -J —,,% d [a I " ' 10 ENGINEERING CIVIL SITE DESIGN PO Box 171 Edmonds, WA 98020 206.419.0973 Preliminary Stormwater Pollution Prevention Plan (SWPPP) Project: Eastman King Single Family Residence (SFR) 131 Skyline Dr Edmonds, WA 98020 Parcel #: 00423000005300 Applicant: Sue Eastman King and Gerald King 131 Skyline Dr Edmonds, WA 98020 eastperson(@me.com Prepared By: Steve Hatzenbeler, PE Stationio Engineering PLLC PO Box 171 Edmonds, WA 98020 stevehpstaloengineering.com Date: June 3, 2021 Revised October 18, 2021 E HAT2 WAS f ry 1 `�A'C1 T'A'1� IONAL� I hereby state that this Construction Stormwater Pollution Prevention Plan for the Mulepati SFR has been prepared by me or under my supervision and meets the standard of care and expertise which is usual and customary in this community for professional engineers. I understand that the City of Edmonds does not and will not assume liability for the sufficiency, suitability, or performance of Construction SWPPP BMPs prepared by me. TABLE OF CONTENTS Section # Subiect Page # Section I Project Description......................................................................................1 Section 11 Existing Site Conditions...............................................................................1 Section I I I Adjacent Areas.............................................................................................2 SectionIV Critical Areas................................................................................................2 SectionV Soils..............................................................................................................2 Section VI Potential Erosion Problem Areas................................................................2 Section VI CSPP Elements.............................................................................................2 Section VIII Construction Phasing..................................................................................4 Section IX Construction Schedule................................................................................4 Section X Financial/Ownership Responsibilities.........................................................4 Section XI Engineering Calculations.............................................................................4 Section XI Certified Erosion and Sediment Control Lead (CESCL) .............................4 Attachment: TESC Plan Eastman King SFR Proi. # 21013 Preliminary SWPPP Statiomo Engineering PLLC Section I — Protect Description The project is a single family residence (SFR) in Edmonds, Washington. Sue Eastman King and Gerald King, the facility Owners, are applying for a grading and building permit to build the home and associated exterior improvements. The site is at 131 Skyline Drive in the Emerald Hills neighborhood on parcel #00423000005300. The z-story home will be built with a daylight basement on the west side, and the yard beyond that will be built on fill behind a large retaining wall. The project will include a storm drainage system and other necessary underground utilities. Several catch basins and trench drains and an underground conveyance system will be installed to route collected stormwater runoff to the new detention tank in the northwest corner of the property. The runoff collection is proposed throughout the site because low impact development features such as dispersion, permeable pavement, and bioretention are not feasible because of the topography and the dense native soils at the site. Proposed improvements in the public right of way include two new driveways, and connections to public utilities. The proposed improvements are designed to meet the requirements of the 2014 DOE Stormwater Management Manual for Western Washington and the June 2017 Edmonds Stormwater Addendum. Areas: • Total project site area:14,iz7 SF (0.324 acres) • Total new/replaced impervious area: 5,825 SF (0.134 acres) • Total proposed area to be disturbed: 13,58o SF (0.312 acres) Section II — Existing Site Conditions The existing site to be improved is undeveloped. It has been previously cleared, and the current condition is lawn/meadow. The project site disturbance area will be approximately 13,58o SF (0.312 ac). Along the west edge of the parcel there is a gravel community walking path; to the south is a residential property; to the east is a sidewalk along the east leg of Skyline Drive; and to the north is a curb line along the north leg of Skyline Drive. The existing topography on the site is variable. There is a level area on the eastern quarter of the parcel adjacent to the sidewalk on the east leg of Skyline Drive, and then there is a slope of 40% or more down to the gravel path on the west, dropping roughly 30 ft. The area is identified in the Edmonds CIS mapping as a Severe Erosion Hazard and Landslide Hazard Critical Area. There is no existing site stormwater runoff collection on site. No off -site drainage flows onto the property. There is a public drainage system consisting of catch basins and 12-inch conveyance pipes in the adjacent public right of way. Eastman King SFR Page 1 Proi. # 21013 Preliminary SWPPP Statiomo Engineering PLLC Section III - Adjacent Areas The project site is surrounded by the Emerald Hills residential neighborhood. Skyline Drive runs along the east and north sides of the site. A gravel community path runs along the west edge of the site. A single family residence is approximately to ft south of the south property line. Section IV - Critical Areas The area is identified in the Edmonds CIS mapping as a Severe Erosion Hazard and Landslide Hazard Critical Area. Section V - Soils A soils investigation was completed in December zozo. Two test pits were excavated to depths of 9 ft below existing grade. The geotechnical engineer observed loose to medium dense fill over dense glacial till. Groundwater was not encountered. Based on the dense soil conditions and steep topography, the geotechnical engineer's opinion is that the subsurface conditions at the site are not conducive to infiltration or dispersion. Refer to the geotechnical report for additional information on the location of the borings and the soil types encountered. Section VI - Potential Erosion Problem Areas Topography on the site is generally quite steep; consequently, stormwater runoff velocity could be relatively high. DOE approved TESC BMPs are included in the design. Large areas of the site will be cleared and left in a working condition for extended periods, and it is the contractor's responsibility to address erosion control and turbidity of stormwater runoff in accordance with the local requirements. Section VII - Construction Stormwater Pollution Prevention Elements 1. Preserve Vegetation and Mark Clearing Limits - Clearing limits have been indicated on the TESC plan. Proposed BMPs expected to be utilized are: BMP C233: Silt Fence • BMP C103: High Visibility Fence 2. Establish Construction Access - Temporary access comprised of quarry spall protection will be utilized; conceptual extents are shown on the TESC plan and shall be adjusted or extended as necessary. Parking for construction vehicles is expected to be off -site along the public street. Proposed BMPs expected to be utilized are: BMP C105: Stabilized Construction Entrance/Exit 3. Control Flow Rates - Controlling of flow rates will be provided by the stormwater detention tank on -site. Eastman King SFR Page z Proi. # 21013 Preliminary SWPPP Statiomo Engineering PLLC 4. Install Sediment Controls - Proposed sediment controls anticipated to be utilized are: • BMP C235: Straw Wattles • BMP C220: Catch basin protection • BMP C121: Mulching • BMP C123: Plastic covering • Sediment settling in the detention tank or a Baker Tank Stabilize Soils - Proposed BMPs expected to be utilized to temporarily stabilize soils in the areas of construction are: BMP C121: Mulching BMP C123: Plastic covering 6. Protect Slopes - Where stockpiles or cut slopes have steep temporary side slopes, the proposed BMPs expected to be utilized to protect the slopes are: • BMP C123: Plastic covering Protect Drain Inlets - Storm drain inlet protection (BMP Czzo) will be installed on existing and new storm drain inlets on and near the site. 8. Stabilize Channels and Outlets - Where temporary conveyance by channels or dikes is required, Interceptor Dikes and Swales (BMP Czoo) and Check Dams (BMP C207) will be utilized. All outlets will consist of piped connections. g. Control Pollutants - The contractor will be responsible for implementing appropriate BMPs for all pollutants that may be brought to the site. Expected BMPs to be utilized include: • BMP C151: Concrete Handling • BMP C152: Sawcutting and Surfacing Pollution Prevention • BMP C153: Material Delivery, Storage, and Containment • BMP C154: Concrete Washout Area lo. Control Dewatering - Temporary dewatering may be required in some areas of the site at some times of the year. If perched groundwater is encountered during trenching, it will be pumped or gravity drained to a dispersion area or the detention tank for sediment settling. 11. Maintain BMPs - All temporary and permanent TESC BMPs will be inspected and maintained as needed to assure continued performance of their intended function throughout the project. Maintenance and repair shall be conducted in accordance with the BMP specifications and the DOE requirements. Eastman King SFR Page 3 Proi. # 21013 Preliminary SWPPP Statiomo Engineering PLLC 12. Manage the Project - The project will not be formally phased because of its relatively small size; however, the contractor is to prioritize completing earthwork during the dry season so the risk of significant erosion will be minimized. All temporary and permanent TESC BMPs will be inspected and maintained as needed to assure continued performance of their intended function throughout the project until all surfaces have been stabilized. This SWPPP and the TESC plan will be reviewed and updated during the project to reflect current construction conditions and BMPs in use. 13. Protect Permanent Stormwater BMPs - Permanent stormwater BMPs consist of a stormwater detention tank and soil amendment. If any sediment is deposited in the detention tank prior to project completion, it shall be removed prior to being placed into service. Permanent surfacing and landscaping shall be protected from damage after installation. Section VIII - Construction Phasing Construction on the site is not expected to be phased because of its relatively small size. The contractor shall prioritize completing earthwork during the dry season so the risk of significant erosion will be minimized. Section IX - Construction Schedule Approximately August 2021 — June zozz Section X - Financial/Ownership Responsibilities The Owner will post any required bonds or other financial securities. Section XI - Engineering Calculations Stormwater calculations are provided in the project's Stormwater Site Plan Report. Section XII - Certified Erosion and Sediment Control Lead (CESCL) The project's CESCL will be named after the contractor has been selected. Please insert the name and contact information for the CESCL in the space below: Name: 24-hour Phone #: Email address: Eastman King SFR Page 4 Proi. # 21013 Preliminary SWPPP Statiomo Engineering PLLC Attachment: TESC Plan Eastman King SFR Page 5 Proj. # 21013 Preliminary SWPPP Statiomo Engineering PLLC RIM=345.48� I \ �•� r.� 9O :'RCP(RIM-343_t3 / / \ _ ` ENGINEERING :i1Y1L SITE CB5�16M 1 1 / \ \ V 4 / / 1 I 10 0 10 edmoods, wa 98020 28fi.418.o8J3 so I ss / I SCALE: 1' = 10' NK A NDETENTION FOUND SURFACE MTD BR. FOUND MNUMENT Datum I NK AT BEGINNI 3" SURFACE � - � V OF CT TO SE 3" SURFACE MTD BR- W/CUT CROSS / I / FOR SEDIM ss w/c ceoss LqV) Fi5 i GRAVEL I / / / SETTLING, PRvB I .i'!j BAKER TANKK " J i so I ss I Section, Township, Range IN, �/ / ''�� `Z I I ss NE 1/4, SE 1/4 SECThN 26, TOWNSHIP 27 N, RANGE 3E, WM SAWCUT AND R / ,.LR aA Legend r / TRScb� Tl s --- �SOMH s g ry / AND DRIVEWAY (TYP) RIM=373.98�I s z02 fqs ° / �I (w)E=369.4q CATCH BASIN PROTECTION p p p p p REMOVE CONCRETE I 2Q,Fy>�_ I 50 (N)E=369 3® 0 0 PAVEMENT/SIDEWALK 1 SET B ISS DISK RIMM=37722 \� STRAW WATTLE S 3,9 6 IE-366.97 I REMOVE CURB / 2 TABILI7/E6 CONSTRUC ° ° `I' I I FILTER FABRIC FENCE CA. ENTIjANCE PER COE STD - Qj / OFT ER-90�VYP) ° ,��CB E�yITT� I TEMP STABILIZED REMOVE ASPHALT PAVEMENT 3NP� CIa e CONSTRUCTION ENTRANCE I I I I iQ• SANITgqRY / / ° C4.0 SrER EASEMENT / Q / \ / / / / / i� i / ' / _ E E STD I ------- _ I SAWCUT PAVEMENT BET E -902 HANDIc (TYP) `9 I Ii II II / RI -376. IN Notes I 4 I 1 ��T��i� 1 "RCP IE 372.811 / t " I. SEE SHEET C4.0 FOR GENERAL NOTES AND TESC GENERAL NOTES. 2. MAINTAIN/RELOCATE TESL MEASURES AND PROVIDE ADDITIONAL TESL MEASURES AS REQUIRED TO STABILIZE INE STRAW WATTLES PER SOILS, MINIMIZE SEDIMENT TRANSPORT ON SITE, AND MEET ALL SITE DISCHARGE AND PERMIT REQUIREMENTS. COE STD DET ca.0 / ADDITIONAL FACILITIES BEYOND THOSE INDICATED ON THIS PLAN MAY BE REQUIRED, AND IT IS THE CONTRAC y I 1 1 \ \ \ \ j ER-903 (ttP) e RESPONSIBILITY TO DETERMINE AND PROVIDE ADDITIONAL MEASURES THAT ARE NECESSITATED DUE TO THEIR NS AND SEQUENCING OF THE WORK. REMOVE ALL TESC MEASURES FOLLOWING SITE STABILIZATION WITH FINAL PD I 1 LANDSCAPING. I I FILLER FA IC FEN V 1 PROPOSED BLDG / I\ I \ \ \ I 3. NOT ALL REQUIRED CB PROTECTION IS INDICATED ON THIS PLAN. INSTALL CB PROTECTION IN ALL EX CATCH \ PET?` COE ST.I7 JET ca.o \ 1 \ \ \ \ ° V' FOOTPRINT (lYP) / DOWNSTREAM OF THE SITE AND ALL INSTALLED CATCH BASINS. MAINTAIN PROTECTION UNTIL TRIBUTARY SURFE. HAT2 GONa / "I � // I STABILIZED. yt� a4 rAsgi�4�� ..I / 4. ALL LOCATIONS OF EXISTING UTILITIES SHOWN HEREON HAVE BEEN ESTABLISHED BY FIELD SURVEY OR OBTAIM AVAILABLE RECORDS AND SHOULD THEREFORE BE CONSIDERED APPROXIMATE ONLY AND NOT NECESSARILY C. FIELD VERIFY LOCATION AND DEPTH OF ALL UTILITIES IN AREA OF EXCAVATION AND NOTIFY ENGINEER OF AN DISCREPANCIES TWO WEEKS PRIOR TO PERFORMING ANY TEMP. SHORING OR EXCAVATION WORK. TEMPS CKPILE P.1.I R MOVE T JOINT �R I y 98 2 S WCUT AL NG SC RE 5. COORDINATE ALL UTILITY INTERRUPTIONS WITH AFFECTED FACILITY OWNERS. PROVIDE MINIMUM 2 WEEKS ADVAI:E PctsTEx�° I 1 \ \ \ 1 LOCATI .COVER - m STOCKPI )4/IN 24 ,!I' LIE (ttP) I OF SERVICE INTERRUPTIONS. SEE ALSO COE GENERAL NOTE ({29. ONAL' HRS y - 6. COMPLY WITH CITY OF EDMONDS TESC REQUIREMENTS, AND PROCURE ANY PERMITS AND REQUIRED APPROVALS FROM 7/8/21 \ I \ \ \ \ \ \ \ \ \ \ 1 \ I / i _------ AHJ FOR CONSTRUCTION DEWATERING/STORMWATER DISCHARGES. DESIGN AND PROVIDE ADDITIONAL TEMPORARY STORAGE I I II I 1 \ \ \ \ 1 \ \ \ \ \ \ 1 \ \ 1 /� �\ .p 17 AND WATER QUALITY TREATMENT, INCLUDING BUT NOT LIMITED TO PRETREATMENT AND STORAGE TANKS, SAND call B@}Of@ -.17 FILTRATION, CHEMICAL TREATMENT SYSTEMS, PIPING, AND/OR PUMPS, AS REQUIRED. DETERMINE THE NUMBER, TYPE T I AND LOCATION OF TREATMENT SYSTEMS IN ACCORDANCE WITH CONTRACTORS' OPERATIONS. YOU DiI \\ \\ \\ \\ \\ \ \ \I \\ \\ \\11 1 V i// I 7 PROVIDE SMS, PUMPS, DETERMINED HPE NUMBER, LOCATIONS, ANDESIZENOFSTEMPORARYYSTEMS ANDSUMPSCPIMPSINTEREPTORSANDESWALESSNAACCORDANCEATWITH 811 CONTRACTORS' OPERATIONS. 8. REMOVE ALL TEMPORARY PIPING AND CAP OR PLUG ALL TEMPORARY PIPE CONNECTIONS UPON TERMINATION OF USE. ,[ Rey n Dare Des�rlPrmn I \ 9. COORDINATE ALL UTILITY DEMOLITION WITH CONSTRUCTION OF NEW SYSTEMS. TEMPORARILY MAINTAIN EXISTING UTILITY 1 I I 1 1 \ \ 1 \ I F'.Q'I •' =' I SYSTEMS AS REQUIRED TO CONVEY FLOWS FROM PORTIONS OF SITE OUTSIDE CONSTRUCTION AREAS AND PROVIDE I I 1 I I I 1 I I \ \ I Y Q lone/zt - nt AS FOXMAIN LOCGIAp v 1 I TEMPORARY BYPASS AND PUMPING SYSTEMS AS REQUIRED BY CONTRACTOR'S OPERATIONS AND OWNER'S USE OF ------------------------ ------ ------ ---' of Gas MAIN PEIP P .. N FACILITIES. A 10. Jill PROVIDE ALL REQUIRED MONITORING, TESTING, REPORTING, AND ALL OTHER COMPLIANCE MEASURES AS NECESSARY TO MEET PROJECT PERMIT COVERAGE REQUIREMENTS. ............. 11. ADDITIONAL EROSION CONTROL MAY BE REQUIRED BY THE CLEARING AND GRADING INSPECTOR. ---------------------------------------------- / o� -�__Er KASK 976 IS s 3 9 I 12. AMEND SOIL IN ALL DISTURBED AREAS PER 2014 SWWMM BMP T5.13._--_--_--_--_--_--_--_--_--_--_--_--_--. // /1 \ \I I\ I I / I' - 13. INSTALL AND MAINTAIN ALL TESC MEASURES ACCORDING TO APPROVED PLANS, CITY OF EDMONDS STANDARD DETAILS. -___-____-____-____-____-_____-__, / AND ALL OTHER MEASURES THAT MAY BE REQUIRED DURING CONSTRUCTION. \ \ \14. COVER TEMPORARY SLOPES AN SOIL STOCKPILES WITH PLASTIC SHEETING WHEN WORK IS NOT TAKING PLACE. UTILIZE SANDBAGS AND/OR OTHER MEANS TO HOLD PLASTIC IN PLACE. stab Prolecr n SET RERAR / _ _ / _ �� _21013 LS 3 976 1 / _ J \ ; `Y',' \ I 5 IF REQUIRED DURING PERIOD OF EXCESSIVELY WET WEATHER, EXCAVATE A TEMPORARY SEDIMENT POND AND/OR PUMP s�6m�rrm. 1 I S g pg' ,{ f . a 8.19' I ,� I RUNOFF INTO A BAKER TANK (OR SIMILAR . 16. COVER BARE SOILS WITH STRAW AND ROCK (W/ WATTLES IN SLOPE AREAS) TO PREVENT SHEET FLOW WHEN WORK IS Permit ROCK WALL 1 I NOT TAKING PLACE. / 17. IF EROSION RESULTS IN SEDIMENT BUILD-UP AT THE SILT FENCES, IT SHOULD BE REMOVED, AND THE SOURCES OF eral No 8 C Q THE EROSION MUST BE MITIGATED AS SOON AS POSSIBLE. g Eastman Kin 1. ALL MATERIALS AND WORK SHOWN ON THESE PLANS SHALL CONFORM TO THE CITY OF EDMONDS S. CONTRACTOR SHALL LOCATE AND PROTECT ALL UTILITIES DURING CONSTRUCTION AND SHALL CONTACT THE 19. ALL FOOTING DRAINS SERVING BUILDINGS, WALLS, ROCKERIES, ETC. SHALL CONNECT TO THE DRAINAGE 29. CONTRACTOR SHALL OBTAIN APPROVAL FROM THE CITY AND FOLLOW CITY PROCEDURES FOR ALL WATER Residence STANDARD PLANS AND DETAILS, THE FOLLOWING SPECIFICATIONS AND CODES, AND ALL OTHER APPLICABLE UNDERGROUND UTILITIES LOCATION SERVICE (1-800-424-5555) AT LEAST 48 HOURS PRIOR TO SYSTEM DOWNSTREAM OF THE SITE STORMWATER DETENTION SYSTEM. SERVICE INTERRUPTIONS, HYDRANT SHUTOFFS, STREET CLOSURES OR OTHER ACCESS RESTRICTIONS. LOCAL MUNICIPAL, STATE, AND FEDERAL CODES, RULES AND REGULATIONS: CONSTRUCTION. CONTRACTOR SHALL NOT RELOCATE OR ELIMINATE ANY HYDRANTS WITHOUT FIRST OBTAINING WRITTEN - CURRENT INTERNATIONAL BUILDING CODE (IBC) 20. CONTRACTOR SHALL OBTAIN AND PAY FOR ALL PERMITS REQUIRED FOR INSTALLATION OF ALL SITE APPROVAL FROM THE FIRE MARSHAL 1 J1 Skyline Dr 9. CONTRACTOR SHALL VERIFY ALL CONDITIONS AND DIMENSIONS AT THE PROJECT SITE BEFORE STARTING IMPROVEMENTS INDICATED ON THESE DRAWINGS. - WSOT/APWA STANDARD SPECIFICATIONS FOR ROAD, BRIDGE AND MUNICIPAL CONSTRUCTION (CURRENT ECifY10r1dS, WA 98OZO WORK AND SHALL NOTIFY OWNER'S REPRESENTATIVE OF ANY DISCREPANCIES. 30. COORDINATE AND ARRANGE FOR ALL UTILITY CONNECTIONS, UTILITY RELOCATIONS AND/OR SERVICE EDITION) 21. A SEPARATE IRRIGATION PERMIT MUST BE OBTAINED FROM THE CITY PUBLIC WORKS DEPARTMENT. PRIOR TO INTERRUPTIONS WITH THE AFFECTED OWNERS AND APPROPRIATE UTILITY COMPANIES. CONNECTIONS TO y - WASHINGTON STATE DEPARTMENT OF ECOLOGY STORMWATER MANAGEMENT MANUAL FOR THE PUGET 10. PIPE LENGTHS WHERE SHOWN ARE APPROXIMATE AND MAY CHANGE DUE TO FIELD CONDITIONS. FINAL CONSTRUCTION ACCEPTANCE, PROVIDE TO THE Cltt WATER QUALITY TECHNICIAN, A COPY OF THE EXISTING UTILITIES SHALL BE MADE ONLY WITH ADVANCE WRITTEN APPROVAL OF THE AUTHORITIES OWYIerS: E SOUND BASIN (CURRENT EDITION) BACKFLOW TEST REPORT. TEST REPORTS CAN BE FAXED TO 425-744-6057 OR EMAILED TO GOVERNING SAID UTILITIES. s 11. CONTRACTOR SHALL OBTAIN A COPY OF THE GEOTECHNICAL REPORT (WHERE APPLICABLE) AND SHALL BACKFLOW TESTING SHALL BE COMPLETED BY THE OWNER ANNUALLY SUE' EaStfYlaft King 5 2. STA RD N TY UMBERS I DICATED THE E D GS REFER TO CITY OF ONDS THOROUGHLY FAMILIARIZE HIMSELF WITH THE CONTENTS THEREOF. ALL SITE WORK SHALL BE PERFORMED THEREAFTER, 31. ALL UTILITIES SHALL BE PLACED UNDERGROUND. and Gerald King _ STANDARD DETAILS, UNLESS NOTED OTHERWISE IN STRICT COMPLIANCE WITH THE RECOMMENDATIONS OF THIS REPORT. 22. AS A MINIMUM REQUIREMENT, ALL DISTURBED AREAS ON AND OFF SITE SHALL BE RETURNED TO THE 32. EXISTING UTILITY LINES IN SERVICE WHICH ARE DAMAGED DUE TO CONSTRUCTION WORK SHALL BE 3. A COPY OF THESE APPROVED PLANS MUST BE ON THE JOBSITE WHENEVER CONSTRUCTION IS IN 12. STRUCTURAL FILL MATERIAL AND PLACEMENT SHALL CONFORM TO THE RECOMMENDATIONS OF THE EQUIVALENT OF THEIR PRECONSTRUCTION CONDITION IN ACCORDANCE WITH APPROPRIATE REQUIREMENTS REPAIRED AT CONTRACTOR'S EXPENSE AND INSPECTED AND ACCEPTED BY CITY OF EDMONDS AND OWNER'S Des19� PROGRESS. PROJECT GEOTECHNICAL REPORT. AND STANDARDS. REPRESENTATIVE PRIOR TO BACKFILLING. 4. DEVIATIONS FROM THESE PLANS MUST BE APPROVED BY THE ENGINEER OF RECORD AND THE LOCAL SEH = 13. SUBGRADE SOILS IN ALL AREAS WHERE RAIN GARDENS, INFILTRATION OR PERVIOUS PAVEMENT IS TO BE 23. ALL DISTURBED SOIL AREAS SHALL BE COMPOST AMENDED AND SEEDED OR STABILIZED BY OTHER """-""'-""""-""'-""'-""""""-""" w GOVERNING AUTHORITY. 33. NEW UTILITY LOCATIONS ARE GENERALLY SHOWN BY DIMENSION, WHERE NO DIMENSIONS ARE INDICATED, orofriny: PLACED SHALL BE DELINEATED AND PROTECTED AT ALL TIMES FROM COMPACTIVE ACTIVITIES (i.e. HEAVY ACCEPTABLE METHODS FOR THE PREVENTION OF ON -SITE EROSION AFTER THE COMPLETION OF LOCATIONS MAY BE SCALED FROM DRAWINGS. FIELD ADJUSTMENTS SHALL BE APPROVED BY OWNER'S ' ? CONSTRUCTION. SEE EROSION CONTROL PLANS FOR SPECIFIC GRADING AND EROSION CONTROL -- '€ 5. CONTRACTOR SHALL RECORD ALL APPROVED DEVIATIONS FROM THESE PLANS ON A SET OF AS -BUILT' EQUIPMENT, STOCKPILING). REQUIREMENTS. REPRESENTATIVE AND CITY. _--_-----_-----_-----_-----_-----_------ DRAWINGS AND SHALL SUMMARIZE ALL AS- BUILT CONDITIONS ON ONE SET OF REPRODUCIBLE DRAWINGS cnl FOR SUBMITTAL TO THE OWNER PRIOR PROJECT COMPLETION AND ACCEPTANCE. A SET OF AS -BUILT 14. MANHOLES, CATCH BASINS, UTILITIES AND PAVEMENT SHALL BEAR ON MEDIUM DENSE TO VERY DENSE 34. FIELD STAKE ALL UTILITY STUBS AT THE PROPERTY LINE. 'a DRAWINGS SHALL BE SUBMITTED TO THE Cltt OF EDMONDS PRIOR TO FINAL APPROVAL OF THE BUILDING NATIVE SOIL OR COMPACTED STRUCTURAL FILL. IF SOIL IS DISTURBED, SOFT, LOOSE, WE OR IF ORGANIC 24. THE CONTRACTOR SHALL KEEP OFF -SITE STREETS CLEAN AT ALL TIMES BY SWEEPING. WASHING OF SEH w THESE STREETS WILL NOT BE ALLOWED WITHOUT PRIOR APPROVAL. 35. TRENCH BACKFILL OF UTILITIES LOCATED WITHIN THE CITY RIGHT-OF-WAY SHALL BE COMPACTED TO 95%. ---'-----------------------------------"--- ---- OCCUPANCY/FINAL PROJECT APPROVAL. MATERIAL IS PRESENT AT SUBGRADE ELEVATION, REMOVE AND REPLACE WITH COMPACTED STRUCTURAL COMPACTION TEST REPORTS SHALL BE PROVIDED TO THE CITY PRIOR TO PAVING. Dore FILL PER GEOTECHNICAL REPORT. 25. THIS PROJECT IS NOT A BALANCED EARTHWORK PROJECT. BOTH EXPORT AND IMPORT OF SOIL AND ROCK 6. ELEVATIONS SHOWN ARE IN FEET. SEE SURVEY FOR BENCHMARK INFORMATION. 15. SEE SURVEY AND ARCHITECTURAL DRAWINGS FOR DIMENSIONS AND LOCATIONS OF BUILDINGS, LANDSCAPED MATERIALS ARE REQUIRED. 36. WHERE NEW PIPE CLEARS AN EXISTING OR NEW UTILITY BY 6' OR LESS, PLACE POLYETHYLENE PLASTIC E/9/2/ 7. THE LOCATIONS OF EXISTING UTILITIES AND SITE FEATURES SHOWN HEREON HAVE BEEN FURNISHED BY AREAS AND OTHER PROPOSED OR EXISTING SITE FEATURES. . FOAM AS A CUSHION BETWEEN THE UTILITIES 26. SLOPE OF FINISHED GRADE SHALL BE CONSTANT BETWEEN FINISHED CONTOURS OR SPOT TESC and OTHERS BY FIELD SURVEY OR OBTAINED FROM AVAILABLE RECORDS AND SHOULD THEREFORE BE 16. SEE ARCHITECTURAL DRAWINGS FOR PERIMETER FOUNDATION DRAINS. FOUNDATION DRAINS SHALL BE ELEVATIONS SHOWN. 37. SEE MECHANICAL DRAWINGS (WHERE APPLICABLE) FOR CONTINUATION OF SITE UTILITIES WITHIN THE € CONSIDERED APPROXIMATE ONLY AND NOT NECESSARILY COMPLETE. IT TI THE SOLE RESPONSIBILITY OF INDEPENDENT OF OTHER SITE DRAIN LINES AND SHALL BE TIGHTLINED TO THE STORM DRAIN SYSTEM BUILDING. WHERE INDICATED ON THE PLANS. THE CONTRACTOR TO INDEPENDENTLY VERIFY THE ACCURACY OF ALL UTILITY LOCATIONS SHOWN AND TO 27. FINISHED GRADE SHALL SLOPE AWAY FROM BUILDING WALLS AT MINIMUM 5� SLOPE FOR A MINIMUM Site le Demo FURTHER DISCOVER AND PROTECT ANY OTHER UTILITIES NOT SHOWN HEREON WHICH MAY BE AFFECTED BY DISTANCE OF 10 FEET, 38. SEE ELECTRICAL DRAWINGS (WHERE APPLICABLE) FOR EXTERIOR ELECTRICAL WORK. THE IMPLEMENTATION OF THIS PLAN. CONTRACTOR SHALL VERIFY LOCATION, DEPTH, SIZE, TYPE AND 1T ALL REQUIRED STORMWATER FACILITIES MUST BE CONSTRUCTED AND IN OPERATION PRIOR TO Plan CONDITION OF EXISTING UTILITY LINES AT CONNECTION OR CROSSING POINTS BEFORE TRENCHING FOR NEW INSTALLATION OF ANY PAVEMENT UNLESS OTHERWISE APPROVED BY THE ENGINEER 28. CONTRACTOR SHALL BE RESPONSIBLE FOR AND SHALL INSTALL AND MAINTAIN SHORING AND BRACING AS 39. SEE LANDSCAPE DRAWINGS (WHERE APPLICABLE) FOR SITE IRRIGATION SYSTEM. UTILITIES. ENGINEER ASSUMES NO RESPONSIBILITY FOR THE COMPLETENESS OR ACCURACY OF THE NECESSARY TO PROTECT WORKERS, EXISTING BUILDINGS, STREETS, WALKWAYS, UTILITIES AND OTHER EXISTING UTILITIES AND SITE FEATURES PRESENTED ON THESE DRAWINGS. ENGINEER SHALL BE NOTIFIED 18. ALL ROOF DRAINS, PERIMETER FOUNDATION DRAINS, CATCH BASINS AND OTHER EXTERNAL DRAINS SHALL EXISTING AND PROPOSED IMPROVEMENTS AND EXCAVATIONS AGAINST LOSS OF GROUND OR CAVING 40. PIPE MATERIAL AND SIGNAGE SUBMITTALS SHALL BE PROVIDED TO CITY ENGINEERING DIVISION FOR IMMEDIATELY OF CONFLICTS THAT ARISE. BE CONNECTED TO THE STORM DRAINAGE SYSTEM, UNLESS NOTED OTHERWISE. ENTS. CONTRACTOR SHALL ALSO BE RESPONSIBLE FOR REMOVAL OF SHORING AND BRACING, AS APPROVAL PRIOR TO INSTALLATION. REQU REPAPPROVED FAR CONSTRUCTION s^Pel E CITY OF EDMONDS b Dare BY 1. CITY ENGINEERING DIVISION Appendix D Operation and Maintenance Manual Eastman King SFR Project #21013 Stormwater Site Plan Statiomo Engineering PLLC Project: 0-,% J re I " 10 ENGINEERING CIVIL SITE DESIGN PO Box 171 Edmonds, WA 98020 206.419.0973 STORMWATER FACILITIES OPERATION AND MAINTENANCE MANUAL Eastman King Single Family Residence (SFR) 131 Skyline Drive Edmonds, WA 98020 Parcel#00423000005300 Applicant: Sue Eastman King and Gerald King eastpersonpme.com Prepared By: Steve Hatzenbeler, PE Stationio Engineering PLLC PO Box 171 Edmonds, WA 98020 stevehPstaloengineering.com Date: June 3, 2021 Revised October 18, 2021 TABLE OF CONTENTS Section # Subject Page # Section 1 Project Description......................................................................................1 Section z Maintenance Importance and Intent..........................................................1 Section 3 Responsible Parties.....................................................................................2 Section 4 Facilities Requiring Maintenance................................................................2 Section 5 Maintenance Instructions...........................................................................3 Section 6 Vegetation Maintenance.............................................................................3 LIST OF FIGURES Figurei Site Map.......................................................................................................2 LIST OF APPENDICES Appendix A Example Maintenance Checklists Eastman King SFR Project #21013 Stormwater Facilities Operation and Maintenance Manual Statiomo Engineering PLLC Section i—Proiect Description The project is a development of a single family residence and associated site improvements such as driveways, retaining walls, and landscaping. The property Owner is applying for building permit to construct the home and related site improvements on an undeveloped parcel. The site is in the Emerald Hills neighborhood in Edmonds. Site Address: 131 Skyline Drive Parcel Number: 00423000005300 Parcel Size: 0.32 acres The project includes a new storm drainage system around the new home to control stormwater runoff in accordance with the Department of Ecology 2014 Stormwater Management Manual for Western Washington (DOE Manual) and the 2017 Edmonds Stormwater Addendum. Catch basins, area drains, and trench drains, and an underground conveyance system will be installed to route collected stormwater runoff to the new underground detention tank along the north edge of the property, which meters the release of stormwater runoff to the public drainage system. The outfall from the detention tank is a piped connection to the existing iz-inch storm drain main line in Skyline Drive along the north edge of the site. Stormwater detention is proposed throughout the site because the steep slopes and dense soil conditions make infiltration and dispersion infeasible at this site. See Figure i on the next page for proposed conditions and stormwater runoff BMPs. Section z — Maintenance Importance and Intent The importance of maintenance for the proper functioning of stormwater control facilities cannot be over -emphasized. A substantial portion of failures (clogging of filters, resuspension of sediments, loss of storage capacity, etc.) are due to inadequate maintenance. Stormwater BMP maintenance is essential to ensure that BMPs function as intended throughout their full life cycle. The fundamental goals of maintenance activities are to ensure the entire flow regime and treatment train designed for this site continue to fully function. For this site these include: • Maintain ability of storm facilities to attenuate flow rates. • Maintain ability to safely convey design stormwater flows. • Preserve soil and plant health, as well as stormwater flow contact with plant and soil systems. • Prevent large-scale or expensive stormwater system failures. • Prevent water quality violations. • Prevent damage to downstream properties. The intent of this maintenance manual is to pass on to the responsible parties all the information critical to understand the design of the system, risks and considerations for proper use, suggestions for maintenance frequency, and cost so that realistic budgets can be established. Eastman King SFR Page 1 Project #21013 Stormwater Facilities Operation and Maintenance Manual Statiomo Engineering PLLC m MAO ON E%12' so MAIN` I unuTr TRllgl RIN .ws os I SFCRON PER CRE STR J I - RFT cu-aRR (Tml IE .su�zz - . 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NECESSAP'T (T>p) � I E5' FE WATER ' I 131 Skyline Dr I 1 � I I' a _ semlRe ]' xunR uErar rI�R C 1 I I 1 I I FIFE Bsmt FFE 367.60 I � 7 I NppR CONNLG ID PU1- L- __} 1 ?- I r a]ErawNc - AA]ER/FIRE srnEN ANDk --- C[] J I I I 1'. •I (trPj d I Pot RCR IRENSAnpx 4 I jl l ,+]\� 'I flIN 376,7G. B'AKFiRY! ASfll&Y IE SI4pp 4 I'I. TRENCH PATL) DUN Y RIM 3MW.t r DUN 36]..I- 11 ARu PN1 ` I ons NsEvCcTO I RIM I I I BY P5E 1 36E,00 0 I _ - _ < nFPNOx'-W I A ELEC METER -`� I cor1 D IN P7 w I I Figure i - Site Map Section ; — Responsible Parties The property owner is responsible for maintenance and operation of the stormwater facilities and BMPs requiring maintenance. Section 4 — Facilities Requiring Maintenance Stormwater structures and BMPs requiring maintenance are as follows. The number listed with each item corresponds to the section from the DOE Manual recommended maintenance checklists, which are attached in Appendix A of this Maintenance Manual. • #3 Detention Tank • #4 Flow Control Structure • #5 Area Drains (similar to Catch Basins) • #5 Trench Drains (similar to Catch Basins) Eastman King SFR Page z Project #21013 Stormwater Facilities Operation and Maintenance Manual Stationio Engineering PLLC Section 5 — Maintenance Instructions The parties responsible for maintenance must review and apply the maintenance requirements contained herein. These maintenance instructions outline conditions for determining if maintenance actions are required, as identified through inspection. However, they are not intended to be measures of the facility's required condition at all times between inspections. Exceedance of these conditions at any time between inspections or maintenance activity does not automatically constitute a violation of these standards. However, based upon inspection observations, the inspection and maintenance presented in the checklists shall be adjusted to minimize the length of time that a facility is in a condition that requires a maintenance action. For facilities not owned and maintained by the City of Edmonds, a log of maintenance activity that indicates what actions were taken must be kept on site and be available for inspection by the City. For information on the purpose, function, and maintenance requirements for all stormwater structures and facilities on the Eastman King SFR site, refer to the DOE Manual recommended maintenance checklists, which are attached in Appendix A of this Maintenance Manual. Section 6 — Vegetation Maintenance There are no vegetated stormwater facilities on the site. There is extensive vegetation throughout the site that is to be maintained by the Owner. Eastman King SFR Page 3 Project #21013 Stormwater Facilities Operation and Maintenance Manual Statiomo Engineering PLLC Appendix A Example Maintenance Checklists Eastman King SFR Project #21013 Stormwater Facilities Operation and Maintenance Manual Statiomo Engineering PLLC No. 3 — Closed Detention Systems (Tanks/Vaults) Maintenance Defect Conditions When Maintenance is Needed Results Expected Component When Maintenance is Performed Storage Area Plugged Air Vents One-half of the cross section of a vent is Vents open and blocked at any point or the vent is damaged. functioning. Debris and Sediment Accumulated sediment depth exceeds 10% All sediment and of the diameter of the storage area for 1/2 debris removed from length of storage vault or any point depth storage area. exceeds 15% of diameter. (Example: 72-inch storage tank would require cleaning when sediment reaches depth of 7 inches for more than 1/2 length of tank.) Joints Between Any openings or voids allowing material to All joint between Tank/Pipe Section be transported into facility. tank/pipe sections (Will require engineering analysis to are sealed. determine structural stability). Tank Pipe Bent Out Any part of tank/pipe is bent out of shape Tank/pipe repaired or of Shape more than 10% of its design shape. (Review replaced to design. required by engineer to determine structural stability). Vault Structure Cracks wider than 1/2-inch and any Vault replaced or Includes Cracks in evidence of soil particles entering the repaired to design Wall, Bottom, structure through the cracks, or specifications and is Damage to Frame maintenance/inspection personnel structurally sound. and/or Top Slab determines that the vault is not structurally sound. Cracks wider than 1/2-inch at the joint of any No cracks more than inlet/outlet pipe or any evidence of soil 1/4-inch wide at the particles entering the vault through the walls. joint of the inlet/outlet pipe. Manhole Cover Not in Place Cover is missing or only partially in place. Manhole is closed. Any open manhole requires maintenance. Locking Mechanism Mechanism cannot be opened by one Mechanism opens Not Working maintenance person with proper tools. Bolts with proper tools. into frame have less than 1/2 inch of thread (may not apply to self-locking lids). Cover Difficult to One maintenance person cannot remove lid Cover can be Remove after applying normal lifting pressure. Intent removed and is to keep cover from sealing off access to reinstalled by one maintenance. maintenance person. Ladder Rungs Unsafe Ladder is unsafe due to missing rungs, Ladder meets design misalignment, not securely attached to standards. Allows structure wall, rust, or cracks. maintenance person safe access. Catch Basins See "Catch Basins" See "Catch Basins" (No. 5). See "Catch Basins" (No. 5) (No. 5). Volume V — Runoff Treatment BMPs — December 2014 4-36 No. 4 - Control Structure/Flow Restrictor Maintenance Defect Condition When Maintenance is Needed Results Expected Component When Maintenance is Performed General Trash and Debris Material exceeds 25% of sump depth or 1 Control structure (Includes Sediment) foot below orifice plate. orifice is not blocked. All trash and debris removed. Structural Damage Structure is not securely attached to Structure securely manhole wall. attached to wall and outlet pipe. Structure is not in upright position (allow up Structure in correct to 10% from plumb). position. Connections to outlet pipe are not watertight Connections to outlet and show signs of rust. pipe are water tight; structure repaired or replaced and works as designed. Any holes --other than designed holes --in the Structure has no structure. holes other than designed holes. Cleanout Gate Damaged or Missing Cleanout gate is not watertight or is missing. Gate is watertight and works as designed. Gate cannot be moved up and down by one Gate moves up and maintenance person. down easily and is watertight. Chain/rod leading to gate is missing or Chain is in place and damaged. works as designed. Gate is rusted over 50% of its surface area. Gate is repaired or replaced to meet design standards. Orifice Plate Damaged or Missing Control device is not working properly due to Plate is in place and missing, out of place, or bent orifice plate. works as designed. Obstructions Any trash, debris, sediment, or vegetation Plate is free of all blocking the plate. obstructions and works as designed. Overflow Pipe Obstructions Any trash or debris blocking (or having the Pipe is free of all potential of blocking) the overflow pipe. obstructions and works as designed. Manhole See "Closed See "Closed Detention Systems" (No. 3). See "Closed Detention Systems" Detention Systems" (No. 3). (No. 3). Catch Basin See "Catch Basins" See "Catch Basins" (No. 5). See "Catch Basins" (No. 5). (No. 5). Volume V — Runoff Treatment BMPs — December 2014 4-37 No. 5 — Catch Basins Maintenance Defect Conditions When Maintenance is Needed Results Expected When Component Maintenance is performed General Trash & Trash or debris which is located immediately No Trash or debris located Debris in front of the catch basin opening or is immediately in front of blocking inletting capacity of the basin by catch basin or on grate more than 10%. opening. Trash or debris (in the basin) that exceeds 60 No trash or debris in the percent of the sump depth as measured from catch basin. the bottom of basin to invert of the lowest pipe into or out of the basin, but in no case less than a minimum of six inches clearance from the debris surface to the invert of the lowest pipe. Trash or debris in any inlet or outlet pipe Inlet and outlet pipes free blocking more than 1/3 of its height. of trash or debris. Dead animals or vegetation that could No dead animals or generate odors that could cause complaints vegetation present within or dangerous gases (e.g., methane). the catch basin. Sediment Sediment (in the basin) that exceeds 60 No sediment in the catch percent of the sump depth as measured from basin the bottom of basin to invert of the lowest pipe into or out of the basin, but in no case less than a minimum of 6 inches clearance from the sediment surface to the invert of the lowest pipe. Structure Top slab has holes larger than 2 square Top slab is free of holes Damage to inches or cracks wider than 1/4 inch and cracks. Frame and/or Top Slab (Intent is to make sure no material is running into basin). Frame not sitting flush on top slab, i.e., Frame is sitting flush on separation of more than 3/4 inch of the frame the riser rings or top slab from the top slab. Frame not securely and firmly attached. attached Fractures or Maintenance person judges that structure is Basin replaced or repaired Cracks in unsound. to design standards. Basin Walls/ Bottom Grout fillet has separated or cracked wider Pipe is regrouted and than 1/2 inch and longer than 1 foot at the secure at basin wall. joint of any inlet/outlet pipe or any evidence of soil particles entering catch basin through cracks. Settlement/ If failure of basin has created a safety, Basin replaced or repaired Misalignment function, or design problem. to design standards. Vegetation Vegetation growing across and blocking more No vegetation blocking than 10% of the basin opening. opening to basin. 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 "Detention Ponds" (No. 1). No pollution present. and Pollution Volume V — Runoff Treatment BMPs — December 2014 4-38 No. 5 — Catch Basins Maintenance Defect Conditions When Maintenance is Needed Results Expected When Component Maintenance is performed Catch Basin Cover Not in Cover is missing or only partially in place. Catch basin cover is Cover Place Any open catch basin requires maintenance. closed Locking Mechanism cannot be opened by one Mechanism opens with Mechanism maintenance person with proper tools. Bolts proper tools. Not Working into frame have less than 1/2 inch of thread. Cover Difficult One maintenance person cannot remove lid Cover can be removed by to Remove after applying normal lifting pressure. one maintenance person. (Intent is keep cover from sealing off access to maintenance.) Ladder Ladder Rungs Ladder is unsafe due to missing rungs, not Ladder meets design Unsafe securely attached to basin wall, standards and allows misalignment, rust, cracks, or sharp edges. maintenance person safe access. Metal Grates Grate opening Grate with opening wider than 7/8 inch. Grate opening meets (If Applicable) Unsafe design standards. Trash and Trash and debris that is blocking more than Grate free of trash and Debris 20% of grate surface inletting capacity. debris. Damaged or Grate missing or broken member(s) of the Grate is in place and Missing. grate. meets design standards. *4&,.Debris Barriers (e.g., Trash Racks) Maintena Defect Condition When Maintenance is Results Expecte Components Needed Maintenan armed General Trash a rash or debris that is plugging more eared to design flow Debris % of the openings in the barri acity. Metal Damaged/ Bars are of shape n 3 Bars in place with no bends more Missing inches. than 3/4 inch. Bars. Ba sing or entire barrie Bars in place according to design. 9 Bars are loose and rust is causing 50% Barri d or repaired to deterioration to any part of barrier. design stan Inlet/Outlet Debris barrier missing or not attached to Barrier firmly attache Pipe pipe Volume V — Runoff Treatment BMPs — December 2014 4-39 Appendix E Maintenance Covenant Eastman King SFR Project #21013 Stormwater Site Plan Statiomo Engineering PLLC After recording return to: City Clerk City of Edmonds 121 Fifth Avenue North Edmonds, WA 98020 Document Title(s) Declaration of Covenant - Private Stormwater BMP Reference Number(s) of Related Documents City of Edmonds (permit number) Grantor(s) (Last, First and Middle Initial) Eastman King, Sue and King, Gerald 131 Skyline Dr Edmonds, WA 98020 Grantee: City of Edmonds Legal Description (abbreviated form; i.e., lot, plat or section, township, range, quarter/quarter) LOT 53, OF EMERALD HILLS, ACCORDING TO THE PLAT THEREOF RECORDED IN VOLUME 31 OF PLATS, PAGES 46-49, RECORDS OF SNOHOMISH COUNTY WASHINGTON. SITUATE IN THE COUNTY OF SNOHOMISH, STATE OF WASHINGTON. Assessor's Property Tax Parcel/Account Number at the Time of Recording: 00423000005300 The Auditor/Recorder will rely on the information provided on this form. The staff will not read the document to verify the accuracy or completeness of the indexing information provided herein. DECLARATION OF COVENANT Private Stormwater BMP WHEREAS, the undersigned Declarant(s) have installed one or more stormwater facilities under Edmonds Community Development Code (ECDC) Chapter 18.30 known as "stormwater best management practices (BMP)" as selected below: ❑ Permeable Pavement ❑ Infiltration Trench/Gallery/Drywell x❑ Detention Pipe/Tank/Vault ❑ Concentrated Flow Dispersion ❑ Other: ❑ Infiltration Tank/Vault ❑ Sheet Flow Dispersion ❑ Reduced Impervious Footprint ❑ Rain Garden / Bioretention Cell WHEREAS, the City of Edmonds has allowed installation of the BMP, subject to the execution and recording of this Declaration of Covenant; NOW, THEREFORE, THE UNDERSIGNED DECLARANT(S), being the owners of the real property ("the Property") located at the following address: 131 Skyline Drive in the City of Edmonds, Washington, and legally described on Exhibit A attached hereto and incorporated herein by this reference as if set forth in full, hereby covenants and agrees, on behalf of himself/herself/themselves/itself and his/her/their/its successors and assigns, as follows: 1. Declarant(s) warrant that he/she/they/it is/are the owner(s) of the property described on Exhibit A and have the authority to impose this covenant on the property and bind all future owners, successors, and assigns of the Declarant(s). The Declarant(s), future owners, successors, and assigns of the Declarant(s) shall be referred to collectively as "Owners." 2. The Owners of the Property agree that the Property contains one or more stormwater management facilities referred to as a 'BMP," which was installed to mitigate the stormwater quantity and quality impacts of some or all of the impervious or non-native pervious surfaces on the property. a. For infiltration -based BMPs, the BMP shall include all pretreatment devices upstream, the infiltration facility, and a minimum of 3-feet of soil beneath the infiltration contact layer, defined as the elevation at which runoff enters native soils. b. For bio-retention or rain garden BMPs, the BMP shall include all pretreatment devices upstream, the retention facility, the vegetation within the retention facility, and a minimum of 3-feet of soil beneath the infiltration contact layer, defined as the elevation at which runoff enters native soils. While specific plants are not necessarily required, a quantitative amount of vegetation coverage is required and may be subject to maintenance requests per Section 5. c. For dispersion based BMPs, the BMP shall include all pretreatment devices upstream, the dispersion mechanism/device, and all elements of the downstream vegetated flow path, including restrictions on slopes and surface materials, as required by ECDC 18.30. d. For detention BMPs, the BMP shall include all pretreatment devices upstream, the detention device, and the control structure device. e. For reduced impervious footprints, the BMP shall include all areas which are used as mitigation credits, including a full ten foot (10') driveway width when using wheel strip driveways. 3. The Owners shall maintain the size, placement, and design of the BMP as depicted on the approved site plan, Exhibit B, attached hereto and incorporated herein by this reference as if set forth in full, and design details shall be maintained and may not be changed without written approval either from the Engineering Division of the City of Edmonds or through a future development permit from the City of Edmonds. Chemical fertilizers and pesticides shall not be used where a BMP is located. All costs of maintenance and repair shall be the sole responsibility of the Owners. 4. The Owners shall inspect BMPs annually for physical defects. After major storm events, the system shall also be checked to ensure that the overflow system is working properly. The Owners also shall maintain all BMPs so they function as designed on a year-round basis. 5. The City of Edmonds is hereby granted by the Owners the right, but not the obligation, to enter upon the Property described on Exhibit A at all reasonable times for the purpose of inspecting the private stormwater BMP facility. If, as the result of any such inspection, the City of Edmonds determines that the BMP is in disrepair, requires maintenance or repair, or is otherwise not functioning as provided in the site plan, the City Engineer or his designee shall have the right, but not the obligation, to order the Owners to maintain or repair the same. The Owners agree to maintain reasonable one-man access to all portions of the BMP and shall avoid permanent or lockable obstructions from blocking a reasonable path of access by City inspectors. Such obstruction may be the sole cause for the City to request maintenance as noted above. 6. If the City of Edmonds determines that the BMP requires maintenance or repair pursuant to Section 5, the City of Edmonds shall provide notice to the Owners of the deadline within which such maintenance or repair must be completed. Said notice may further advise that, should the Owners fail to perform required maintenance or make repairs within the established deadline, the work may be done by the City or a contractor designated by the City Engineer and the expense thereof shall be charged to the Owners. The City's officers, agents, employees, and contractors shall have the right, which is hereby granted by the Owners, to enter upon the Property described on Exhibit A in order to perform such work. The Owners shall bear the cost of all work performed. 7. The Owners shall indemnify, defend and hold harmless the City of Edmonds, its officers, officials, employees and agents from any and all claims, demands, suits, penalties, losses, damages, judgments, attorneys' fees and/or costs of any kind whatsoever, arising out of or in any way resulting from the approval of the BMP(s), the installation and presence of the BMP(s), and the acts or omissions of the Owners, their officers, employees, contractors, and agents relating to the construction, operation and maintenance of the BMP(s) on the Property, except for the City's intentional and willful tortious acts, and waive and release the City of Edmonds from any and all claims for damages and injunctive relief which the Owners may themselves have now or in the future, by reason of the construction, maintenance and operation of said BMP(s). This covenant shall run with the land and be binding upon the Owners. Dated: DECLARANT(S): (Signature) (Print Name) (Signature) (Print Name) State of Washington ) Ss. County of Snohomish ) APPROVED: CITY OF EDMONDS (Signature) (Print Name) (Title) On this day personally appeared before me {Declarant(s)I to me known to be the individual, or individuals described in and who executed the within and foregoing instrument, and acknowledged that he/she/they/it signed the same as his/her/their/its free and voluntary act and deed, for the uses and purposes therein mentioned. SUBSCRIBED AND SWORN before me this day of (Signature) 20 . (Name legibly printed or stamped) Notary Public in and for the State of Washington. Residing at: My commission expires Exhibit A Legal description LOT 53, OF EMERALD HILLS, ACCORDING TO THE PLAT THEREOF RECORDED IN VOLUME 31 OF PLATS, PAGES 46-49, RECORDS OF SNOHOMISH COUNTY WASHINGTON. SITUATE IN THE COUNTY OF SNOHOMISH, STATE OF WASHINGTON. Exhibit B Site Plan ENGINEERING CIVIL SITE DESIGN PO Box 171 Edmonds, W 98020 206.419.0873 ��I I S SCT < R & CAP SSMH \ 76 RIM- \ IE=342.152.15 CATCH BASIN I / 9 D ®Ii.S% 5B MAIN ON EX 12- RIM=345.48 "RCP(E)IE=343.13 i UTILITY TRENG RIM 355.00 SECTION PER COE STD s5 50.56 (8") DETU-400 (TXP) / IE 350. " I A s I ' I � � / 2Q' W/ VANED I NNECT FD I GRATE DOW CTREAM OF \ 'P RIM 3554.75 EouNo MONUMENT [ I\ / 1 / \ FOUND MONUMENT _ _ D EN IIUN SYSTEM I I \ E 35�.70 (8' 3" SURFACE PITS BR. 3" SURFACE MTD BR W/CUT CROSS W/C CROSS T o Flow &UNTROL UCTURE I IM 16 LF CONNECT 1' I ss TIE 3 0.94 (8") I ,� J ®1.5%� / ABOVE 1PRINGLIN s°��- \ IF 35 .94 (36") I USINGFTEXIBLE I ss I I I INC / / ��' \ CONNf�TOR � I SSCO W/ 112" MPHOLE I / ��- \ ' J SS 3R9B6R CA I COVER W/ 1/J" HE�( BOLTS / 1 OSOMH AND A CON�2ETE COLLAR I I/ SN Y� t7 / I RIM=373.98 ss RIMI153*11 / �36, # I I I (w)IE=369.ag1 1 IB 349.74 / / NOP �� ?°? 2 I s° (N)I E=369 3 rt✓V / / E BeT r SSMH - I - SOL B 5S DISK RIM=377.22 F NEW SS 'LATERAL /• ® 9RA7 I _ _ _ / LS 319r6 IE=366.97 CONNECTION TO TOP OF SS h - MAIN PER COE ISTD SE 7- " ;-•7 -� •�--� ' TRENCH 1 �� ISS-202 57 LF 6" S�.`3 .® 1BZ/ - '�� DRAIN C4.1 t ly IF 342.7t (6" �S MAIN) FIELD VERIFY SS MAIN IE �i \', �� 6 ,♦ \ < \ �RAss NISK SET NI MIN 2 WKS f�RIOR TO I SA-�---- -� i I CONSTRUCTION C. \ WE, M ENT' i� / �� / ♦ �� i LS 3 976 SS EbSEMENT III HANDICAP � I AFN # 135318 vl I 1•r (L� , 1 ♦♦, _ Rt,M_P- '� y /'/ ♦♦� C TCH IN AREA DRAIN #3 I I R i - - -- -- I � ♦ � RI =376.6.5 I Ikdss.t7 1 f III Ai �' ♦ 1 "RCP IE 37z811 IE 3 3.0 (6") I 1 1 III I CONNECit (0--�� 80 LF 6" SD 1 IL?INGFOOTAG BRAIN I-----��_--_ ®2% MIN I I I � 50 LF 6 SD I I CONNECT TO BUIL ING 2% MIN 1 A -� 1 I, t - V A WASTEtyATER 5YS� M. SEWER -' I 1 \ \ co PEft\coE STD \DET SS-200 AREA DRAIN #2 I \ l• \ \ RIM 365�0 \ - •--•-•--•�• II I // 367.30 \ - \ IE 3665 6 I I \ I I 1\ \ I\ \ CONCEPT lj1LOCATIONS LF 6 1 \ I SwoWN. CO RD W/ C67ER D IGN AND ADdusT/ado I s Id 1s% oN I LK v vI I �� gc. i ` `OOTIN Ds coNNECTIdNs As - I\ D�pIN C4. NEC SSAR (4P) I I ( \ \ \ 1,31 SIQyIIne Dr\\ I �/ 1.5" PE WATER SERVICE 1' WATER EfER R FFE 11377.150 c E srD ET wA-130 Ssm FFE 367.66 _ Q I` KID \ cbNNECT TO BUILDING S li \ �•� I \ OVE HANG ` WATER/HIRE SYSTEM (ttP I \ 1 I AR41 DRAIN Q PO IE d A7I4. 0'FOR IR IGATION I I I 7 (4 )A V 1 BA KFLOW {'SEMBL I I II I I 1 I I .0 I ` �' •I PATTS� DRAIN 2 TRENCH t PAX I I I A\ V n DRAIN ,, D4.t I m GAS S O Y I AR N ..IN 1,1 I IE 363.59 (") I I ` \ \ 1 aE L@Jt¢ATIDN I CONN TION RRRRRR��R��R}}}}.... I I \ \ -- of S MNG PER ESE BY P IMI 067.20 I I I / I 1 $f' 1 IE 3 5l0 (6") h 'l - - - - I / = -�•� APPROX\GAS ELEd I F II 1 METER OC I SVC I i I III IL-- II --L 1 / +- ^ BASS ISK I- -� - -- = I �- A A LS 3 976 I - CONNECT WALL LJ X 7 - 0 I I l I I l 1V A \ \ 1 I DRAIN (TYR) Q SET &EcnP� LS 31976 o RIM 365.59 LEANOI� 2 I IF 363.59 (4�) � � 9 za < ROCK WALL I I I I IIIIr I I I 111 pr 10 0 10 SCALE: 1" = 10' Datum NAVD 88 Section, Township, Range NE 1/4, SE 1/4 SECTION 26, TOWNSHIP 27 N, RANGE 3E, WM Legend ® AREA DRAIN 0 PATIO DRAIN CB TYPE 1 PER COE STD GET SD-303 CB TYPE 2 FLOW CONTROL STRUCTURE 0 SO OR SS CLEANOUT --•-- PVC STORM DRAIN 4" ® 2% MIN PVC STORM DRAIN 6" & UP - - - - - - - - PERT UNDER -DRAIN/ - - - - 6" SANITARY SIDE SEWER PVC Z -•-•- SDR 35 W/ GASKETED FITTINGS WATER C N --- ELECTRICAL SERVICE LINE ----- TELECOM SERVICE LINE GAS SERVICE LINE RETAINING WALL Notes 1, SEE SHEET 11.1 FOR GENERAL NOTES. 2. SEE COE STD DET GU-400 FOR TYPICAL ROW TRENCH SECTION AND DETAIL 5 C4.0 FOR ON -SITE TRENCH SECTION. / 3. VERIFY LOCATION AND INVERTS OF ALL EX SYSTEMS AT PROPOSED POC9 TO NEW LINES PRIOR TO CONSTRUCTION OF ANY NEW PIPING, AND NOTIFY ENGINEER OF ANY DISCREPANCIES AT LEAST 4 WORKING DAYS PRIOR TO STARTING PIPE LAYING OPERATIONS. 4. MAINTAIN ALL EXISTING UTILITY SERVICES DURING CONSTRUCTION. PROVIDE TEMPORARY SERVICES AND ALL BYPASS SYSTEMS, INCLUDING PUMPING, AS NECESSARY TO ACCOMPLISH NEW CONSTRUCTION AND MINIMIZE SERVICE INTERRUPTIONS. 5. PLACE STORM DRAINS AND SANITARY SEWERS AT A MINIMUM SLOPE OF 2% AND A MAXIMUM SLOPE OF 50% UNLESS NOTED OTHERWISE. 6. COORDINATE BLDG SYSTEM CONNECTION LOCATIONS AND IE9 W/ MECH/PLUMBING CONTRACTOR. PROVIDE ALL RE RE 0 N 10 Q ORDINATE ALL UTILITY INTERRUPTIONS W/ AFFECTED FACILITY OWNERS. PROVIDE MIN 2 WEEKS ADVANCE NOTICEANY SERVICE INTERRUPTION. SEE ALSO COE GENERAL NOTE #29.N L AL RI P NG. 9. WHERE A NEW PIPE CLEARS AN EXISTING OR NEW UTILITY BY 6" OR LESS, PLACE POLYETHYLENE PLASTIC FOAM AS A CUSHION BETWEEN THE UTILITIES. 10. ADJUST ALL NEW AND EX UTILITY CASTINGS TO FINAL FINISHED GRADE PRIOR TO FINAL PAVING/PLANTING. 11. TAKE THE NECESSARY PRECAUTIONS DURING TRENCH EXCAVATION TO PROTECT EXISTING UTILITIES FROM DAMAGE AND SETTLEMENT. 12. PROVIDE 2.5' MIN COVER OVER ALL WATER LINES, UNLESS NOTED OTHERWISE. 1". P VI E 0 T L 0 14. A MINIMUM OF 2' OF COVER IS REQUIRED FOR ALL PIPES LOCATED UNDER DRIVABLE SURFACES AND 1' OF t COVER UNDER LANDSCAPED AREAS. 15. IF THE RIM TO IE EXCEEDS 5' THEN A TYPE II MANHOLE WILL BE REQUIRED. 16. A MINIMUM OF 3' HORIZONTAL SEPARATION IS REQUIRED BETWEEN THE DRY UTILITIES (POWER, GAS, PHONE, CABLE, ETC.) AND SEWER, WATER, AND STORM AND 5' FROM ANY CITY MAIN LINES. APPROVED FOR CONSTRUCTION CITY OF EDMONDS DATE: BY: CITY ENGINEERING DIVISION E HATZ v�oe rasgr�o y T 'p gBclS TE �l�' �tONAL Fad' 7/8/21 call Before You DiI 811 Rev # Date Description SI 10/18/21 CN N1 ----------------------------------------------- stalo Prolecr #: 21013 ----------------------------------------------- ---------------- S.-Itd: Permit Eastman King Residence 1 _'1 Skyline Dr Edmonds, WA 98020 Owners: Sue Eastman King and Gerald King Design. SEH Druf flog: Checketl SEH _---.............................................................. - ....... _.- --- _--- Duce 7/9/21 Drainage and Utility Plan S-1