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APPROVED_Drainage Report 06.05.20
C � ENGINEERING 250 4th Ave S Ste 200 Edmonds, WA 98020 Phone: (425) 778-8500 Fax: (425) 778-5536 civil & structural engineering & planning DRAINAGE REPORT Crouch-Maupin Residence COMPLIES WITH APPLICABLE C 1141 Viewland Way Edmonds, WA 98020 0610512020 CG Project No.: 20008.20 Table of Contents Section I — Project Overview Section II — Off -Site Analysis Section III — Permanent Stormwater Control Plan Section IV —Construction Stormwater Pollution Prevention Plan Section V — Special Reports and/or Studies Section VI — Other Permits Section VII — Bond Quantities & Operation and Maintenance Manual C � 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Crouch-Maupin Residence - CG #20008.20 June 2, 2020 Drainage Report Section I, Page 1 Section I — Project Overview Section I Summa Overview Existing Condition Developed Condition Minimum Requirements Overview This drainage report has been prepared in accordance with the 2014 Department of Ecology's Stormwater Management Manual for Western Washington (SWMMWW), Chapter 18.30 of the Edmonds Community Development Code (ECDC), and the 2017 Edmonds Stormwater Addendum. This drainage report is for a new single-family residence house on a 0.26 ac lot located at 1141 Viewland Way in Edmonds, WA (Tax Parcel Number: 00606600001800). The project is located in the Hindley Watershed, which outlets to the Shell Creek Watershed. The proposed development includes a roof area of approximately 3,504 sf along with an associated concrete driveway and concrete paver walkways totaling in approximately 4,756 sf (0.109 ac) of new/replaced hard surfaces. There is an existing single-family residential house with attached car port, shed, and associated walkways and driveway that will be mostly all demolished for the proposed construction. Approximately 780 sf of the existing driveway on -site will remain in the proposed condition. Since the project will add between 2,000 sf and 5,000 sf of new plus replaced hard surface area, the project is classified as Category 1 per the Edmonds Stormwater Addendum and must comply with Minimum Requirements #1-5 of ECDC Chapter 18.30 and the Edmonds Stormwater Addendum. Existing Condition The site is currently developed with a house, attached car port, shed, driveway and walkways on a rectangular, approximately 11,500 sf (0.26 ac) lot. Other ground cover includes small to medium-sized trees, shrubs and grass. Associated Earth Sciences completed a subsurface exploration for the site with two exploration borings, one to 26.5' and the other to 41.5', on September 12, 2019. According to the Geotechnical report, the grass/topsoil layer is approximately 4" thick. Fill soils "consisting of loose to dense, moist, light brown to brownish gray, very silty fine to medium sand with variable gravel content" were encountered to approximate depths of 4' below the surface. "Underlying the fill, exploration borings EB-1 and EB-2 encountered loose to medium dense, moist to wet, very silty, fine to medium sand, with variable amounts of gravel, organics, and wood fragments, to approximate depths below the surface of 13 and 29 feet, respectively." Groundwater was encountered at these depths as well. "Although not encountered at the time of drilling, perched groundwater within the fill or landslide deposits may be present during the wet season." More about the soils can be found in Section V in the Geotechnical Engineering Report. C 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Crouch-Maupin Residence - CG #20008.20 June 2, 2020 Drainage Report Section I, Page 2 The site is bound on the north and west by other single-family residences, 121h Ave N on the east, and Viewland Way on the south. Site/driveway access is from Viewland Way. The slopes along the eastern and western portions of the property are in excess of 40% and are considered to be Landslide Hazard Areas by the City of Edmonds. An erosion hazard map can be seen in Figure II-2 in Section II. The eastern portion of the driveway that will remain appears to be sloped such that runoff will collect on the eastern portion of the site. The western portion of the driveway to remain appears to slope toward Viewland Way. Downspouts were observed on the existing house that go underground. These are assumed to be connected to roof drains that are tight -lined to a public storm pipe in the ROW between the north pavement edge and the south property line. Utilities are generally located in the north edge of Viewland Way and include the sewer, water, and storm mains. There is an existing drainage ditch in between the north pavement edge of Viewland Way and the property's south property line. The ditch runs east to west and becomes a culvert under the existing driveway approach and continues west in an underground pipe. Near the SW property corner, the pipe daylights into an open, half -circle, concrete channel continuing down to catch basins and conveyance pipes that convey runoff to Hindley Creek and ultimately to Puget Sound. The site is generally flat around the existing house except for the steep slope areas on the east and west portions of the property. The site does not appear to take on significant upstream flows. The eastern steep slope is heavily vegetated with shrubs and small and medium-sized trees. The existing impervious areas on -site are as follows: Impervious Areas Roof: 2,802 sf (0.064 ac) Patio/walkways: 230 sf (0.005 ac) Driveway: 1,364 sf (0.031 ac) Total: 4,396 sf (0.101 ac) Developed Condition The project consists of the construction of a new single-family residence with associated walkways and a driveway. The total of new plus replaced hard surface is 4,756 sf (0.109 ac). Disturbance will affect most of the property outside of the steep slopes. The site will utilize two rows of 36"-diameter 19'-long detention pipes with 3' connectors between for a total of 44 lineal feet of detention pipe with a flow control structure to manage the new/replaced roof and other hard surfaces and existing driveway to remain to address Minimum Requirement #5. The detention pipe system will run SE/NW and will be located in the southwest quadrant of the site. All runoff on -site will be directed to the proposed house's roof drains, which will outlet into the proposed detention pipe system. The detention system will be connected to two Type II catch basins, one of which C 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Crouch-Maupin Residence - CG #20008.20 Drainage Report June 2, 2020 Section I, Page 3 will have a flow control structure and 12" discharge pipe. Proximity to structures and property lines can be seen in the civil drawings on sheet C3.1. The new and replaced hard surface areas are as follows: Hard Surface Areas Roof: 3,504 sf (0.080 ac) Patio/Walkways: 792 sf (0.018 ac) Driveway: 460 sf (0.011 ac) Total: 4,756 sf (0.109 ac) The existing hard surface area to remain on -site is as follows: Existing Hard Surface Area to Remain Driveway: 780 sf (0.018 ad Total: 780 sf (0.018 ac) Total lot area: 0.26 ac a Total new/replaced hard surfaces: 0.11 ac PGHS/PGIS: 0.03 ac Total disturbed area: 0.20 ac Average slope within clearing limits: 0-1% NRCS soil group: B Irmo C:) Ln N O V_ Figure 1-1. Vicinity map (City of Edmonds GIS Map). C 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Crouch-Maupin Residence - CG #20008.20 June 2, 2020 Drainage Report Section I, Page 4 W € PROJECT SITE J 120`6 1123 111 51 1141 4 lr _ � a IL EW-1976 Figure 1-2. Map showing existing utilities near site (City of Edmonds GIS Map). X;Mqll� # ,•x;-A; Pq 1p Ir rt f ' -AW # '} ; X 'fit � � f •�� �, �� -�i- A IL lJS w— M 11 Figure 1-3. Aerial image of site (from Google Maps). X's represent approximate boring locations (see Geotech report). C 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Crouch-Maupin Residence - CG #20008.20 Drainage Report June 2, 2020 Section I, Page 5 Minimum Requirements Stormwater requirements were determined per the December 2016 Edmonds Stormwater Addendum, ECDC Chapter 18.30, and the 2014 SWMMWW. The project is classified as a Category 1 Project Using Figure 1-4 (Figure 3.1 in the Edmonds Stormwater Addendum) and will comply with Minimum Requirements #1-5. Minimum Requirement #1: Preparation of Stormwater Site Plans: The stormwater site plan consists of this report and the civil drawings, and is prepared in accordance with Chapter 3 of Volume 1 of the SWMMWW and the requirements in the Edmonds Stormwater Addendum. Minimum Requirement #2: Construction Stormwater Pollution Prevention Plan (SWPPP): The SWPPP shall include a narrative and drawings. The SWPPP narrative shall include documentation that addresses the 13 elements of Construction Stormwater Pollution Prevention. See Section IV and the civil drawings. Minimum Requirement #3: Source Control of Pollution: Source control BMPs are described in Section IV and Source Control BMP sheets can be found in the Operation and Maintenance Manual in Section Vill. Minimum Requirement #4: Preservation of Natural Drainage Systems and Outfalls: Natural drainage patterns shall be maintained, and discharges from the project site shall occur at the natural location, to the maximum extent practicable. The manner by which runoff is discharged from the project site must not cause a significant adverse impact to downstream receiving waters and down -gradient properties. All projects shall submit an off -site qualitative analysis. A qualitative analysis of the upstream and downstream system entering the site is presented in Section 11. Minimum Requirement #5: On -Site Stormwater Management: Category 1 projects that discharge directly or indirectly to the City's MS4 and are required to comply with Minimum Requirements #1-5 (per ECDC 18.30.060.C) shall either use On -site Stormwater Management BMPs from List #1 or demonstrate compliance with the LID Performance Standard. This project will use On -site Stormwater Management BMPs from List #1 (see Section III). C 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Crouch-Maupin Residence - CG #20008.20 Drainage Report June 2, 2020 Section I, Page 6 [kx:s the project result in 2,000 square feet, or greater, urnew plus replaced hard surface area? OR Ikws the land disturbing activity total 7,000 square fr:ct or greater? es No Ntinimurn RequircmcnLs No. I through 5 apply Minimum Requirement No. 2 applies Next Quesfi m Dees the project add 5,000 square feet or more of new plus replaced hard surfaces? OR Convert 0.75 acres or more of vegetation to lawn or landscaped areas? OR Convert 2.5 acres or more of native vegetation to pasture? No Yes Is this a road related prnje10 Tea All Minimum RcyuLrt~mcnts apply to the new and replayed �� hard surfaces and converted vegetation areas_ All Minimum Requirements apply to the new hard srafac:cs and converted vegetation arcaa. Does the project acid 5,000 square feet or more of new hard surfaces? Yes Do new hard surfaces add 50%gar more to the existing hard surfaces within the project limits? No No No I Noadditional I requirements. Figure 1-4. Flow Chart for Determining Minimum Requirements for Development (Figure 3.1 in the Edmonds Stormwater Addendum). C 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Crouch-Maupin Residence - CG #20008.20 June 2, 2020 Drainage Report Section II, Page 1 Section II — Off -Site Analysis Section II Summary Task 1 — Define and map the study area Task 2 — Review all available information of the study area Task 3 — Field inspect the area Task 4 - Describe the drainage system, and its existing and predicted problems Task 1— Define and map the study area An initial qualitative analysis shall document potential off -site impacts of stormwater discharges for each upstream drainage system entering a site, and each downstream drainage system leaving a site according to Section 6.2 of the Edmonds Stormwater Addendum. The downstream analysis shall extend from the project site to the receiving water, or up to one -quarter mile, whichever is less. Runoff from the site enters the City's MS4 within one -quarter mile since the project proposes to connect into the public storm main along the project frontage. The receiving water is Hindley Creek which is about 0.28 mi downstream from the site. The downstream flowpath is outlined below in Figure II-1 from the City GIS map. OUTFALL I;... I.' o - c PROJECT SIT y� o 1206 112,1 1135 HINDLEY a VlFVL+LA 0°5 uwmi CREEK °.°4 mi P.Q7 r �i a 1020 �,�s � :I a PDs-s7 - 6 1'4[1 O o Figure II-1. Map showing stormwater flow path and distance from site to outfall. Task 2 — Review all available information on the studv area Existing stormwater improvements were determined from the survey and the City GIS map. There is an underground 8" concrete pipe that runs west under the existing driveway along the south edge of the property in the ROW. The 8" pipe daylights into an open, half -circle, concrete channel continuing down to a catch basin at the northwest corner of the intersection of Viewland Way and 11t" PI N. The flow crosses 11t" Place North and daylights into a ditch, then goes back under a driveway and into a ditch again where the flow enters the storm system underneath Olympic Avenue. The flow then enters a 24" concrete pipe and crosses Olympic Avenue and continues west down Viewland Way. The pipes change from 24" to 8" to 12" and then to a 36" concrete main before discharging to Hindley Creek. Per the City GIS map, the site contains erosion hazard areas. An erosion hazard area map can be seen below in Figure II-2. The east side of the lot has a steep slope, but is heavily vegetated and should not C 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Crouch-Maupin Residence - CG #20008.20 Drainage Report June 2, 2020 Section II, Page 2 contribute significant flows to the site. The west side of the lot has a steep slope that slopes down away from the house. Legend = x < �l_ti — Critical Areas , = Creeks + ® Seismic Hazard Areas - Earth Subsidence and Landslide Area L Minimum Buffer Adjacent to Hazard 17 Wetlands — Wetlands Boundary Wetland Boundaries Not Completely Delineated 1 Wetland Known Extents ® Floodplains — landslide and Erosion Hazard Landslide Hazard Area 40% severe Erosion Hazard 15%-40% Erosion Hazard Areas 15%-40% 1135 VIEWLAND WAY Q J& 1230 1r '14 ITE l0. I I-TV� v Legend Landslic... 0 30 60ft I A Figure II-2. Erosion hazard area map. 213 C) C) N 1[ Task 3 — Field inspect the study area A site visit was done on the afternoon of January 3, 2020. The weather was cloudy and it had lightly rained that day. From evaluating surrounding conditions, the site does not appear to take on significant upstream runoff. The steep eastern slope that slopes toward the site is heavily vegetated and is not expected to concentrate runoff. The project proposes to tie the roof drains to a 36"-diameter detention pipe system with a flow control structure prior to connecting to the storm main along Viewland Way. On the following pages, Figures II-3 through II-7 show pictures of the existing site and downstream of the site where runoff would enter the City's public storm system. The catch basins and open ditches that were observed along Viewland Way appeared to be free from problems. C 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Crouch-Maupin Residence - CG #20008.20 Drainage Report June 2, 2020 Section II, Page 3 w_C Figure II-3. Viewland Way, facing north at site. ~.tea", '�; ►- - !s �A ter ME- \11EWLMAC) WAY Figure II-4. Viewland Way, facing north at site. C � ENGINEERING 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Crouch-Maupin Residence - CG #20008.20 Drainage Report June 2, 2020 Section II, Page 4 0111 1•I� 17-1 i 1 i 4/ Vfi �`i in 1 • X Ae F f 'a/ •� Jw- - �_ .s e y� VIEW LAND WAY Figure II-5. Viewland Way, facing north at site. Figure II-6. Downstream of project site in neighboring driveway approach in ROW. C 4C—;.—V 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Crouch-Maupin Residence - CG #20008.20 Drainage Report June 2, 2020 Section II, Page 5 Figure II-7. Downstream of project site in north edge of Viewland Way. Task 4 — Describe the drainage system, and its existing and predicted problems Existing stormwater improvements were determined from the survey and the City GIS map. This is described in Task 2. The project proposes to route all runoff from impervious surfaces of the site to a 36"-diameter detention pipe system to meet the on -site stormwater management requirements (see Section III). A flow control structure with a 12" discharge pipe will be located at the east end of the detention system. The pipe will tie into the existing 8" PVC main that runs west along Viewland Way. There are no anticipated issues with the proposed drainage improvements. The detention pipe was designed conservatively to account for the entire existing driveway area to remain even though not all of the driveway will contribute to the detention system. It is assumed that all existing runoff from impervious surfaces is conveyed directly to the public storm system in Viewland Way and other runoff flows into Viewland Way and enters the public storm system by sheet flow. This project will manage stormwater on -site with a detention pipe before releasing stormwater to the public system. C 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Crouch-Maupin Residence - CG #20008.20 Drainage Report June 2, 2020 Section III Page 1 Section III — Permanent Stormwater Control Plan Section III Summary Narrative Feasibility Review Calculations Summary Narrative The proposed project is a Category 1 project per the Edmonds Stormwater Addendum that discharges to the City's MS4. It shall either use On -Site Stormwater Management BMPs from List No. 1 (per ECDC 18.30.060.D.5.d) for all new plus replaced hard surfaces and land disturbed, or demonstrate compliance with the LID performance standard (per ECDC 18.30.060.D.5.c ). The project proposes to use On -site Stormwater Management BMPs from List No. 1 (per ECDC 18.30.060.D.5.d). Feasibility Review The project must implement on -site stormwater management BMPs to the maximum extent feasible per Minimum Requirement #5. The following BMPs were evaluated per List No. 1 of the On -site Stormwater Management BMPs for Projects Triggering Minimum Requirements #1 through #5: Lawn and landscaped areas: 1. Post -construction soil quality and depth in accordance with BMP T5.13 in Chapter 5 of Volume V of the SWMMWW will be used for all disturbed pervious areas. Roofs: 1. Full Dispersion in accordance with BMP T5.30 is infeasible because a 65 to 10 ratio of forested or native vegetation area to impervious area cannot be achieved. Downspout Full Infiltration Systems in accordance with BMP T5.10A is infeasible because there is no area large enough on -site that is not within 50 feet of the top of slopes greater than 15%. 2. Rain Gardens in accordance with BMP T5.14A and Bioretention in accordance with Chapter 7 are infeasible because there is no area large enough on -site that is not within 50 feet of the top of slopes greater than 15%. 3. Downspout Dispersion Systems in accordance with BMP T5.1013 are infeasible because the required flowpath lengths cannot be achieved. 4. A Perforated Stub -Out Connection in accordance with BMP T5.10C is infeasible because there is no area large enough on -site that is not within 50 feet of the top of slopes greater than 15%. 5. Detention vaults or pipes in accordance with the Edmonds Stormwater Addendum are feasible and a detention pipe system will be used to manage runoff for all impervious surfaces on -site. Other Hard Surfaces: C 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Crouch-Maupin Residence - CG #20008.20 Drainage Report June 2, 2020 Section III Page 2 1. Full Dispersion in accordance with BMP T5.30 is infeasible because a 65 to 10 ratio of forested or native vegetation area to impervious area cannot be achieved. 2. Permeable pavement in accordance with BMP T5.15 in Chapter 5 of Volume V of the SWMMWW is infeasible because the proposed pavement areas on -site are all within 50 feet of the top of slopes greater than 15%. 3. Rain Gardens in accordance with BMP T5.14A and Bioretention in accordance with Chapter 7 are infeasible because there is no area large enough on -site that is not within 50 feet of the top of slopes greater than 15%. 4. Sheet Flow Dispersion in accordance with BMP T5.12, or Concentrated Flow Dispersion in accordance with BMP T5.11 in Chapter 5 of Volume V of the SWMMWW is infeasible because the dispersion area would be within 50 feet of the top of slopes greater than 15%. 5. Detention vaults or pipes in accordance with the Edmonds Stormwater Addendum are feasible and a detention pipe system will be used to manage runoff for all impervious surfaces on -site. r'nlriilntinnc Per the Edmonds Stormwater Addendum 6.3.1, a detention pipe was sized for length. A 36"-diameter pipe was sized using the equation L = 0.008*A, where L is length of pipe (ft) and A is contributing surface area (sf). Hard Surface Areas Contributing to Detention Pipe Roof: 3,504 sf Patio/Walkways: 792 sf New Driveway: 460 sf Existing driveway to remain: 780 sf* Total: 5,536 sf *Only about 530 sf of existing driveway will contribute to detention pipe. Total driveway area included to be conservative. L = 0.008*(5,536 sf) = 44.2 ft. Therefore, a 36"-diameter, a total of 44 ft of detention pipe was designed to mitigate stormwater runoff for the the site. See civil plans for more. C 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Crouch-Maupin Residence - CG #20008.20 Drainage Report June 2, 2020 Section IV, Page 1 Section IV — Construction Stormwater Pollution Prevention Plan Section IV Summarv: Narrative Construction SWPPP Elements Source Controls Erosion control details are provided consistent with the City of Edmonds guidelines. Erosion control plan sheets are provided in full size as a part of the civil drawing set. A Construction SWPPP is not required by the Department of Ecology because the site is under one acre (the land -disturbing activity threshold which requires the completion of their SWPPP document and Construction Stormwater General Permit). Construction SWPPP Elements The elements for construction pollution prevention are discussed as follows: Element 1: Mark Clearing Limits To protect adjacent properties and to reduce the area of soil exposed to construction, the limits of construction will be clearly marked before land -disturbing activities begin. Clearing limits will be to the extents of necessary land disturbance for the new house and associated driveway, walkways and utilities. The BMPs relevant to marking the clearing limits that will be applied for this project include: High Visibility Plastic or Metal Fence (BMP C103) Element 2: Establish Construction Access Construction access or activities occurring on unpaved areas shall be minimized, yet where necessary, access points shall be stabilized to minimize the tracking of sediment onto public roads. The existing driveway may be used as a stabilized construction entrance if approved by City inspector. Otherwise, a stabilized construction entrance should be installed per the following BMP: Stabilized Construction Entrance (BMP C105) Element 3: Control Flow Rates The site is small and flat enough that concentrated flow rates are not expected to occur within the construction activity area of this site and a silt fence that will be used for Element 4 is expected to be sufficient to control flow rates on -site. Element 4: Install Sediment Controls C 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Crouch-Maupin Residence - CG #20008.20 Drainage Report June 2, 2020 Section IV, Page 2 All stormwater runoff from disturbed areas shall pass through an appropriate sediment removal BMP before leaving the construction site or prior to being discharged. Silt fence is proposed to be installed along the north and west property lines and a portion of the south property line. This can be seen on the Temporary Erosion Control Plan, C2.1. Pollution prevention facilities on the erosion control plan must be constructed prior to or in conjunction with all clearing and grading to ensure that the transport of sediment to surface waters and adjacent properties is minimized. The specific BMPs to be used for controlling sediment on this project include: Silt Fence (BMP C233) Element 5: Stabilize Soils Exposed and unworked soils shall be stabilized with the application of effective BMPs to prevent erosion throughout the life of the project. The specific BMPs for soil stabilization that shall be used on this project include: Temporary and Permanent Seeding (BMP C120) Mulching (BMP C121) Nets and Blankets (BMP C122) Plastic Covering (BMP C123) Sodding (BMP C124) Topsoil ing/Composting (BMP C125) Surface Roughening (BMP C130) Dust Control (BMP C140) Element 6: Protect Slopes Exposed slopes shall be stabilized with BMPs found in Element 5. Element 7: Protect Drain Inlets Drain inlets along Viewland Way and as made operable on -site must be protected from sedimentation. Stormwater must not enter the conveyance system without first being filtered or treated to remove sediment. Inlet protection devices must be cleaned or removed and replaced when sediment has filled one-third of the available storage (or as specified by the manufacturer). The specific BMPs to be used for protecting drain inlets are: Storm Drain Inlet Protection (BMP C220) Element 8: Stabilize Channels and Outlets Existing conveyance channels in the vicinity of the site appear to be well -stabilized as -is. Element 9: Control Pollutants Design, install, implement and maintain effective pollution prevention measures to minimize the discharge of pollutants. The suggested BMPs are: C 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Crouch-Maupin Residence - CG #20008.20 Drainage Report June 2, 2020 Section IV, Page 3 Concrete Handling (BMP C151) Sawcutting and Surfacing Pollution Prevention (BMP C152) Material Delivery, Storage and Containment (BMP C153) Element 10: Control Dewatering Groundwater is not anticipated to be an issue (see Section V for Geotechnical report). Element 11: Maintain BMPs All temporary and permanent erosion and sediment control BMPs must be maintained and repaired as needed to ensure continued performance of their intended function. Element 12: Manage the Project • Phase development projects to the maximum degree practicable and take into account seasonal work limits. • Inspection and monitoring — Inspect, maintain, and repair all BMPs as needed to assure continued performance of their intended function. Conduct site inspections and monitoring in accordance with the Construction Stormwater General Permit or local plan approval authority. • Maintain an Updated Construction SWPPP - This SWPPP shall be retained on -site or within reasonable access to the site. - The SWPPP shall be modified whenever there is a change in the design, construction, operation, or maintenance at the construction site that has, or could have, a significant effect on the discharge of pollutants to waters of the state. - The SWPPP shall be modified if, during inspections or investigations conducted by the owner/operator, or the applicable local or state regulatory authority, it is determined that the SWPPP is ineffective in eliminating or significantly minimizing pollutants in stormwater discharges from the site. The SWPPP shall be modified as necessary to include additional or modified BMPs designed to correct problems identified. Revisions to the SWPPP shall be completed within seven (7) days following the inspection. Element 13: Protect Low Impact Development BMPs There are no LID BMPs proposed that will need protection. Sn1/rrP Cnntrnls This project should incorporate required BMPs from Volume IV of the DOE Manual: 5407 — BMPs for Dust Control at Disturbed Land Areas and Unpaved Roadways and Parking Lots; 5411— BMPs for Landscaping and Lawn/Vegetation Management; and 5417 — BMPs for Maintenance of Stormwater Drainage and Treatment Systems. The Operation & Maintenance Manual found in Section VII contains guide sheets for the aforementioned BMPs. C 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Crouch-Maupin Residence - CG #20008.20 Drainage Report June 2, 2020 Section V, Page 1 Section V — Special Reports and/or Studies Section V Summary: Narrative The following reports are included in this section: 1. Geotechnical Engineering Report by Associated Earth Sciences, dated October 15, 2019. 2. NRCS Soil Resource Report, dated February 27, 2020. C � 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com a s s o c i a t e d e a r t h s c i e n c e s incorporated Subsurface Exploration, Geologic Hazard, and Geotechnical Engineering Report MAUPIN—CROUCH RESIDENCE Edmonds, Washington Prepared For: TERRI MAUPIN AND PETE CROUCH Project No. 20190294E001 January 10, 2020 a s s o c i a t e d earth sciences i n c o r p o r a t e d January 10, 2020 Project No. 20190294EO01 Terri Maupin and Pete Crouch 1141 Viewland Way Edmonds, Washington 98020 Subject: Subsurface Exploration, Geologic Hazard, and Geotechnical Engineering Report Maupin—Crouch Residence 1141 Viewland Way Edmonds, Washington 98020 Dear Terri Maupin and Pete Crouch: We are pleased to present the enclosed copy of our geotechnical report. This report summarizes the results of our subsurface exploration, geologic hazard, and preliminary geotechnical engineering studies, and offers preliminary geotechnical recommendations for the design and development of the proposed project. We have enjoyed working with you on this study and are confident that the preliminary recommendations presented in this report will aid in the successful completion of your project. Please contact me if you have any questions or if we can be of additional help to you. Sincerely, ASSOCIATED EARTH SCIENCES, INC. Kirkland, Washington Anthony'W. Roma' nick, P. E. Senior Project Engineer AWR/ms/Id - 20190294EO01-4 Kirkland Office 1911 Fifth Avenue i Kirkland, WA 98033 P 1425.827.7701 Mount Vernon Office 1508 S. Second Street, Suite 101 i Mount Vernon, WA 98273 P 1425.827.7701 Tacoma Office i 1552 Commerce Street, Suite 102 i Tacoma, WA 98402 P i 253.722.2992 www.aesgeo.com SUBSURFACE EXPLORATION, GEOLOGIC HAZARD, AND GEOTECHNICAL ENGINEERING REPORT MAUPIN—CROUCH RESIDENCE Edmonds, Washington Prepared for: Terri Maupin and Pete Crouch 1141 Viewland Way Edmonds, Washington 98020 Prepared by: Associated Earth Sciences, Inc. 911 51h Avenue Kirkland, Washington 98033 425-827-7701 January 10, 2020 Project No. 20190294EO01 Subsurface Exploration, Geologic Hazard, and Maupin—Crouch Residence Geotechnical Engineering Report Edmonds, Washington Project and Site Conditions I. PROJECT AND SITE CONDITIONS 1.0 INTRODUCTION This report presents the results of Associated Earth Sciences, Inc.'s (AESI) subsurface exploration, geologic hazard, and geotechnical engineering study for a new single-family residence located at 1141 Viewland Way in Edmonds, Washington. Our understanding of the project is based on discussions and email exchanges with you; a topographic survey titled "Boundary and Topographic Survey, Maupin / Crouch Residence," prepared by Terrane, dated July 9, 2019; and our experience working in the project area. The site location is shown on the "Vicinity Map," Figure 1. The approximate locations of explorations completed for this study, along with existing site features, are shown on the "Existing Site and Exploration Plan," Figure 2. The conclusions and recommendations contained in this report should be reviewed and modified, or verified, once project plans are finalized. 1.1 Purpose and Scope The purpose of this study was to provide subsurface data to be utilized in the design and development of the referenced project. Our study included reviewing available geologic literature, completing two exploration borings with a mini -track drill rig, and performing geologic studies to assess the type, thickness, distribution, and physical properties of the subsurface sediments and groundwater. Geotechnical engineering studies were completed to determine site preparation recommendations, structural fill recommendations, the type of suitable foundations, retaining wall/lateral earth pressures, erosion considerations, geologic hazard assessments, and drainage considerations. This report summarizes our fieldwork and offers preliminary recommendations based on our present understanding of the project. We recommend that we be allowed to review the recommendations presented in this report and revise them, if needed, when the project design has been finalized. 1.2 Authorization This report has been prepared for the exclusive use of Terri Maupin and Pete Crouch, and their agents, for specific application to this project. Our work was performed in accordance with our scope of work and cost proposal, dated August 9, 2019. Within the limitations of scope, schedule, and budget, our services have been performed in accordance with generally accepted geotechnical engineering and engineering geology practices in effect in this area at the time our report was prepared. No other warranty, express or implied, is made. January 10, 2020 ASSOCIATED EARTH SCIENCES, INC. A WRIMS11d - 20190294EO01 -4 Page 1 Subsurface Exploration, Geologic Hazard, and Maupin—Crouch Residence Geotechnical Engineering Report Edmonds, Washington Project and Site Conditions 2.0 PROJECT AND SITE DESCRIPTION The project site is that of the existing single-family residential property located at 1141 Viewland Way in Edmonds, Washington (Snohomish County Parcel No. 00606600001800), as shown on Figure 1 "Vicinity Map." The parcel is rectangular in plan view and is approximately 0.26 acres in size. The parcel is currently occupied by a single-family residence centrally located on the parcel. The site is bounded on the north and west by single-family residences, to the east by 121h Avenue North, and to the south by Viewland Way. Site topography is gently to steeply sloping downward toward the west with a relatively flat area at the center of the parcel which contains the existing residence. The topography of the neighborhood surrounding the subject site is similar, suggesting that the area of the site had been graded to create building lots in a "terraced" configuration many years ago. Slopes near the eastern and western parcel boundaries range in height from 10 feet to 16 feet and have inclinations as steep as 62 percent. We understand that the current project plan includes demolition of the existing residence with the construction of a new single-family residence. The subject site includes Landslide Hazard Areas and Erosion Hazard Areas, as delineated in the City of Edmonds' maps. 3.0 SUBSURFACE EXPLORATION Our field study included advancing two exploration borings at the site (EB-1 and EB-2). The approximate locations of the borings are shown on Figure 2. The conclusions and recommendations presented in this report are based on the conditions encountered in these explorations. The number, locations, and depths of our explorations were completed within site and budgetary constraints. Copies of the exploration logs are included in Appendix A. Because of the nature of exploratory work below ground, interpolation of subsurface conditions between field explorations is necessary. It should be noted that subsurface conditions between the explorations may differ from those inferred by the boring data due to the random nature of deposition and the alteration of topography by past grading and/or filling. The nature and extent of any variations between the field explorations may not become fully evident until construction. If variations are observed at that time, it may be necessary to re-evaluate specific recommendations in this report and make appropriate changes. 3.1 Exploration Borings The exploration borings were drilled using a mini -track -mounted, hollow -stem auger drill rig. During the drilling process, samples were generally obtained at 2.5- to 5-foot-depth intervals. The exploration borings were continuously observed and logged by an engineering geologist January 10, 2020 ASSOCIATED EARTH SCIENCES, INC. A WRIMS11d - 20190294EO01 -4 Page 2 Subsurface Exploration, Geologic Hazard, and Maupin—Crouch Residence Geotechnical Engineering Report Edmonds, Washington Project and Site Conditions from our firm. The exploration logs presented in the Appendix are based on the field logs, drilling action, and observation of the samples secured. Disturbed, but representative samples were obtained by using the Standard Penetration Test (SPT) procedure in accordance with ASTM International (ASTM) D-1586. This test and sampling method consists of driving a standard 2-inch, outside -diameter, split -barrel sampler a distance of 18 inches into the soil with a 140-pound hammer free -falling a distance of 30 inches. The number of blows for each 6-inch interval is recorded, and the number of blows required to drive the sampler the final 12 inches is known as the Standard Penetration Resistance ("N") or blow count. If a total of 50 is recorded within one 6-inch interval, the blow count is recorded as the number of blows for the corresponding number of inches of penetration. The resistance, or N-value, provides a measure of the relative density of granular soils or the relative consistency of cohesive soils; these values are plotted on the boring logs in the Appendix. The samples obtained from the split -barrel sampler were classified in the field and representative portions placed in watertight containers. The samples were then transported to our laboratory for further visual classification. 4.0 SUBSURFACE CONDITIONS Subsurface conditions at the project site were inferred from the field explorations accomplished for this study, our visual reconnaissance of the site, and review of selected geologic literature. As shown on the field logs, the exploration borings generally encountered fill overlying old landslide debris and older in -place sediments. The following section presents more detailed subsurface information organized from the shallowest (youngest) to the deepest (oldest) sediment types. 4.1 Stratigraphy Grass/Topsoil A surficial layer of grass/topsoil was encountered at the location of our explorations. These organic layers were approximately 4 inches thick. Due to their high organic content, these materials are not considered suitable for foundation support, slab -on -grade floor support, or for use in a structural fill. January 10, 2020 ASSOCIATED EARTH SCIENCES, INC. A WRIMS11d - 20190294EO01 -4 Page 3 Subsurface Exploration, Geologic Hazard, and Maupin—Crouch Residence Geotechnical Engineering Report Edmonds, Washington Project and Site Conditions Existing Fill We encountered fill soils (soils not naturally placed) consisting of loose to dense, moist, light brown to brownish gray, very silty fine to medium sand with variable gravel content to approximately 4 feet below the surface in both explorations. The observed fill included minor amounts of organic material and contained small rootlets. Excavated existing fill material is suitable for reuse in structural fill applications if such reuse is specifically allowed by project plans and specifications, if excessively organic and any other deleterious materials are removed, and if the moisture content is adjusted to allow compaction to the specified level and to a firm and unyielding condition. Existing fill is also expected in unexplored areas of the site, such as the area surrounding and under the existing structure foundations, in existing utility trenches, and at previously graded landscaped areas. Due to their variable density and organic debris content, the existing fill soils are not suitable for structural support of foundations. Landslide Deposits Underlying the fill, exploration borings EB-1 and EB-2 encountered loose to medium dense, moist to wet, very silty, fine to medium sand, with variable amounts of gravel, organics, and wood fragments, to approximate depths below the surface of 13 and 29 feet, respectively. The loose condition of the material encountered, and the presence of organics and wood debris are suggestive of deposits derived from past earth movement (landslides). Due to their variable density and variable content, including organic material, the existing landslide debris is not recommended for foundation support. Pre -Fraser Nonglacial Deposits Underlying the landslide deposits in our exploration borings and extending to the depth explored, we encountered sediments generally consisting of medium dense to very dense or hard, fine to coarse sand with variable silt and gravel ranging to fine sandy silt with trace fine organics. We interpret these sediments to be representative of pre -Fraser nonglacial sediments. The high relative density of the sediments indicates that they have been overrun and consolidated by glacial ice. These sediments were deposited in a nonglacial environment prior to the Fraser glaciation. We anticipate these sediments are present at depths too deep to be considered for excavation and reuse as structural fill. The pre -Fraser nonglacial sediments are generally considered suitable for support of light to moderately loaded foundations. January 10, 2020 ASSOCIATED EARTH SCIENCES, INC. AWRIMS11d-20190294E001-4 Page 4 Subsurface Exploration, Geologic Hazard, and Maupin—Crouch Residence Geotechnical Engineering Report Edmonds, Washington Project and Site Conditions 4.2 Geologic Map Review Review of the regional geologic maps titled Geologic Map of the Edmonds East and Part of the Edmonds West Quadrangles, by J.P. Minard (1983) and Composite Geologic Map of Sno-King Area, by D.B. Booth, B.F. Cox, K.G. Troost, and S.A. Shimel (2004) indicate that the area of the subject site is underlain by Vashon advance outwash deposits (Qva), with pre -Fraser -age deposits mapped downslope of the subject site. Our interpretation of the sediments encountered below the landslide debris is in partial agreement with the geologic units mapped in the area as our borings did not encounter Vashon advance outwash underlying the surficial fill soils but did encounter pre -Fraser age deposits at depth beneath the landslide deposits. 4.3 Hydrology Shallow groundwater at the project site is expected to be present in two zones: a perched groundwater interval in the existing fill soils or landslide deposits, and the unconfined aquifer present in the pre -Fraser sediments. It should be noted that the depth to groundwater and duration or quantity of seepage can vary in response to changes in weather, season, changes in land use, and other factors. • Perched Groundwater: Although not encountered at the time of drilling, perched groundwater within the fill or landslide deposits may be present during the wet season. Perched groundwater occurs when rain or surface water infiltrates through upper, looser, and more permeable soils, such as existing fill and landslide deposits, and becomes trapped on top of siltier intervals located within these deposits. • Pre -Fraser Aquifer: Groundwater was observed near the top of the pre -Fraser nonglacial deposits. We interpret that this groundwater is representative of an unconfined aquifer located within the pre -Fraser sediments. January 10, 2020 ASSOCIATED EARTH SCIENCES, INC. A WRIMS11d - 20190294EO01 -4 Page 5 Subsurface Exploration, Geologic Hazard, and Maupin—Crouch Residence Geotechnical Engineering Report Edmonds, Washington Geologic Hazards and Mitigations II. GEOLOGIC HAZARDS AND MITIGATIONS The following discussion of potential geologic hazards is based on the geologic, slope, and shallow groundwater conditions, as observed and discussed herein. 61111 WI-110113311la:r_r�_1:].7_V1.3*:%I ia►:: The following paragraphs discuss the stability of the slopes and recommendations to mitigate risks to the public health, safety, or welfare. It must be understood that no recommendations or engineering design can yield a guarantee of stable slopes. Our observations, findings, and opinions are a means to identify and reduce the inherent risks to the owner. The slopes along the eastern and western portions of this property are in excess of 40 percent with greater than 10 feet of vertical relief and are located in areas of historic failures as determined by the landslide deposits underlying the site. As such, they are considered Landslide Hazard Areas by the City of Edmond's City Code (ECC). The site has been subject to past grading, including the abovementioned "terracing' of the surrounding neighborhood and the placement of fill over the parcel during the original construction of the residence. 5.1 LIDAR Mapping As stated above, we encountered landslide debris in our explorations. Based on our review of the Light Detection and Ranging (LIDAR) image encompassing the subject site, the slopes leading upward from the area of downtown Edmonds to the upland encompassing the subject site include several bowl -shaped slide features, including to the immediate east and south of the subject site. However, based on our review of the conditions observed during our site reconnaissance, it is our opinion that the landslide scarps suggested by the LIDAR image near to the subject site likely originated in the ancient past, possibly during or subsequent to ice retreat at the conclusion of the Vashon Stade of the Fraser Glaciation. 5.2 Slope Reconnaissance During our site reconnaissance and our subsurface explorations, we found no visual evidence of tension cracks, emergent seepage, hummocky topography, or other indications of recent slope instability at the subject site. The eastern slope is vegetated with grass, shrubs, and small trees, and the western slope has been altered recently in association with construction of the residence next door. Alteration to the western slope includes the construction of a relatively January 10, 2020 ASSOCIATED EARTH SCIENCES, INC. A WRIMS11d - 20190294EO01 -4 Page 6 Subsurface Exploration, Geologic Hazard, and Maupin—Crouch Residence Geotechnical Engineering Report Edmonds, Washington Geologic Hazards and Mitigations short rockery approximately 3 to 4 feet in height, near the base, removal of vegetation over the bottom two-thirds of the slope, and the installation of a jute net or similar erosion control product and new landscape plants. 5.3 Slope Stability Analysis An analysis of the stability of the western and eastern slopes under existing conditions was completed using the computer program SLOPE/W, version 8.16.2.14053 by GeoSlope International. The program used the Morgenstern —Price method for evaluating a rotational failure. Input parameters for the analysis included slope geometry, geology, and soil -strength parameters. The slope geometry was based on contours from the provided survey. The profile used for our analysis was located along section line A -A' as depicted on Figure 2. AESI modeled the slopes under existing conditions as project plans have not been completed. The geology of the slopes was based on the subsurface conditions encountered in our explorations and our experience. Our slope profile shows a thicker section of fill along the west property line when compared to the fill thickness encountered in EB-2. This is due to the difficulty of distinguishing the fill from landslide deposits in hollow -stem auger samples and the likely grading practice implemented during original site grading. Because the strength parameters between the fill and landslide debris are similar, defining the depth of the contact between these two soils has little effect on the results of our modeling. Soil strength parameters used for our analysis were assumed based on typical published values for similar materials and our prior experience. The values assumed for our analysis are shown on the attached SLOPE/W profiles. For evaluation of slope stability under seismic conditions, a horizontal ground acceleration of 0.27g was used for our analysis. This value is equivalent to % of the peak horizontal ground acceleration associated with a return period of 2,475 years, in accordance with the 2015 International Building Code (IBC). The factor of safety of a slope is the ratio between the forces that resist sliding to the forces that drive sliding. For example, a factor of safety of 1.0 would indicate a slope where the driving forces and the resisting forces are exactly equal. Increasing factor of safety values greater than 1.0 indicate increased stability. An acceptable factor of safety would depend on the level of risk deemed acceptable by the owner and City of Edmonds. The ECC requires the proposed development does not decrease the factor of safety below 1.5 for static conditions and 1.2 for short-term dynamic conditions. Minimum factors of safety of failure extending down to the existing residence from the east slope or starting at the existing residence for slides occurring on the west are provided in Table 1. The results of our SLOPE/W analysis are provided in Appendix B. January 10, 2020 ASSOCIATED EARTH SCIENCES, INC. A WRIMS11d - 20190294EO01 -4 Page 7 Subsurface Exploration, Geologic Hazard, and Maupin—Crouch Residence Geotechnical Engineering Report Edmonds, Washington Geologic Hazards and Mitigations Table 1 Slope Stability Results Slope Minimum Factor of Safety Static Minimum Factor of Safety Seismic East Slope >1.5 >1.2 West Slope >1.5 1.0 Our slope stability analysis indicates that the western slope exhibits factors of safety lower than 1.2 under seismic conditions for failures that extend under the residence. As discussed later in our "Foundations" section, we propose new foundations are supported by pipe piles that extend into the pre -Fraser sediments underlying the site. 5.4 Landslide Hazard Mitigation As previously mentioned, our slope stability analysis shows that during strong seismic events, slope failure surfaces from the western slope extend under the residence with factors of safety less than 1.2. To mitigate for these low factors of safety, we recommend that new foundations be supported by a pipe pile foundation system. We have provided pipe pile recommendations in our "Foundations," section. By supporting the new foundations on pipe piles, the project will avoid surcharging the west slope with new loads, will not decrease the factors of safety for either the east or west slope under both static and seismic conditions, and will help mitigate the risk to the residence associated with the low factor of safety for the west slope under seismic conditions. Additional recommendations for landslide hazard mitigation are discussed below. Provided the recommendations in this report are followed, it is our opinion that no adverse impact on the steep slope area or the proposed development will result through the elimination of the steep slope buffer for the western or eastern slope. We recommend a building setback of 10 feet measured from the top of the west steep slope. To the extent possible, we recommend that native vegetation be left on the slopes to provide erosion control. At no time should loose fill be pushed over the top of the slopes or soil excavated from the toe area without support by an engineered retaining structure. Uncontrolled fill on slopes or toe excavation may promote landslides or debris flow activity. AESI should review grading plans if grading is desired at the top of, on, or near the toe of the steep slopes. If the project is designed with the recommendations provided in this report, it is our opinion that the proposed project will not a) not increase surface water discharge or sedimentation to January 10, 2020 ASSOCIATED EARTH SCIENCES, INC. A WRIMS11d - 20190294EO01 -4 Page 8 Subsurface Exploration, Geologic Hazard, and Maupin—Crouch Residence Geotechnical Engineering Report Edmonds, Washington Geologic Hazards and Mitigations adjacent properties beyond predevelopment conditions, b) not decrease slope stability on adjacent properties, and c) not adversely impact other critical areas. 6.0 SEISMIC HAZARDS AND MITIGATION Earthquakes occur in the Puget Lowland with great regularity. The vast majority of these events are small and are usually not felt by people. However, large earthquakes do occur, as evidenced by the 1949, 7.2-magnitude event; the 2001, 6.8-magnitude event; and the 1965, 6.5- magnitude event. The 1949 earthquake appears to have been the largest in this region during recorded history and was centered in the Olympia area. Evaluation of earthquake return rates indicates that an earthquake of the magnitude between 5.5 and 6.0 is likely within a given 20- to 40-year period. Generally, there are four types of potential geologic hazards associated with large seismic events: 1) surficial ground rupture, 2) seismically induced landslides, 3) liquefaction, and 4) ground motion. The potential for each of these hazards to adversely impact the proposed project is discussed below. 6.1 Surficial Ground Rupture The nearest known fault trace to the project site is the South Whidbey Island Fault Zone (SWIFZ) located approximately 4 miles to the northeast. A recent study by the U.S. Geological Survey (USGS) (Sherrod, et al., 2005, Holocene Fault Scarps and Shallow Magnetic Anomalies Along the Southern Whidbey Island Fault Zone Near Woodinville, Washington, Open -File Report 2005-1136, March 2005) indicates that "strong" evidence of prehistoric earthquake activity has been observed along associated fault strands thought to be part of the SWIFZ. The study suggests as many as nine earthquake events along the SWIFZ may have occurred within the last 16,400 years. The recognition of this fault splay is relatively new, and data pertaining to it are limited, with the studies still ongoing. The recurrence interval of movement along this fault system is still unknown, although it is hypothesized to be in excess of 1,000 years. Due to the suspected long recurrence interval, it is our opinion that the potential for damage to the proposed structure by surficial ground rupture is considered to be low. No mitigations other than complying with 2015 IBC seismic design recommendations are recommended. 6.2 Seismically Induced Landslides Our slope stability modeling indicates that slope failure surfaces that extend from the west slope to under the residence are present with factors of safety under 1.2 for seismic conditions. See Section 5.0 for further discussion and mitigation recommendations. January 10, 2020 ASSOCIATED EARTH SCIENCES, INC. A WRIMS11d - 20190294EO01 -4 Page 9 Subsurface Exploration, Geologic Hazard, and Maupin—Crouch Residence Geotechnical Engineering Report Edmonds, Washington Geologic Hazards and Mitigations 6.3 Liquefaction Liquefaction is a condition where loose, saturated, typically sandy soils lose shear strength when subjected to high -intensity cyclic loads, such as those that occur during earthquakes. The resulting reduction in strength can cause differential foundation settlements and slope failures. Loose, saturated sands that cannot dissipate the buildup of pore water pressure are the predominant type of sediments subject to liquefaction. The landslide deposits encountered in our explorations had zones that are considered loose but were unsaturated, as were the fill soils. The pre -Fraser nonglacial deposits were saturated but were encountered as medium dense to dense and are not likely to liquefy as a result. In our opinion, the subsurface conditions observed in our exploration borings represent a low risk of liquefaction during a design -level seismic event. A detailed liquefaction hazard analysis was not performed as part of this study, and none is warranted in our opinion. 6.4 Ground Motion Structural design of the building should follow 2015 IBC standards using Site Class "D" as defined in Table 20.3-1 of American Society of Civil Engineers (ASCE) 7 - Minimum Design Loads for Buildings and Other Structures. 7.0 EROSION HAZARDS AND MITIGATION The sloping portions of the parcel are considered Erosion Hazard Areas based on the definition provided in Section 23.80.020 of the ECC. We anticipate that site construction will be limited to the flat areas of the parcel and the existing slopes will not be altered. However, a properly developed, constructed, and maintained erosion control plan consistent with local standards and best management erosion control practices will be required for this project. It will be necessary to make adjustments and provide additional measures to the Temporary Erosion and Sedimentation Control (TESC) plan in order to improve its effectiveness. Ultimately, the success of the TESC plan depends on a proactive approach to project planning and contractor implementation and maintenance. The erosion hazard of the site soils is low to high, depending primarily on slope and runoff velocity. Maintaining cover measures atop disturbed ground provides the greatest reduction to the potential generation of turbid runoff and sediment transport. During the local wet season (October 15t through March 315t), exposed soil should not remain uncovered for more than 2 days, unless it is actively being worked. Ground -cover measures can include erosion control matting, plastic sheeting, straw mulch, crushed rock or recycled concrete, or mature hydroseed. January 10, 2020 ASSOCIATED EARTH SCIENCES, INC. A WRIMS11d - 20190294EO01 -4 Page 10 Subsurface Exploration, Geologic Hazard, and Maupin—Crouch Residence Geotechnical Engineering Report Edmonds, Washington Geologic Hazards and Mitigations 7.1 Erosion Hazard Mitigation To mitigate the erosion hazards and potential for off -site sediment transport, we recommend the following: 1. All TESC measures for the work area should be installed prior to any activity. 2. During the wetter months of the year (typically October through April), or when large storm events are predicted during the summer months, the work area should be stabilized so that if showers occur, the work area can receive the rainfall without excessive erosion or sediment transport. 3. All disturbed areas should be revegetated as soon as possible. If it is outside of the growing season, the disturbed areas should be covered with mulch. 4. Under no circumstances should concentrated discharges be allowed to flow over the top of steep slopes. 5. Disturbance to vegetation on steep slope areas should be avoided, if possible. 6. Soils that are to be reused around the site should be stored in such a manner as to reduce erosion from the stockpile. Protective measures may include, but are not limited to, covering with plastic sheeting, the use of low stockpiles in flat areas, or the use of straw bales/silt fences around pile perimeters. We anticipate that if our recommendations for erosion mitigation are followed, the development of the project will not significantly increase the site's risk of erosion. January 10, 2020 ASSOCIATED EARTH SCIENCES, INC. A WRIMS11d - 20190294EO01 -4 Page 11 Subsurface Exploration, Geologic Hazard, and Maupin—Crouch Residence Geotechnical Engineering Report Edmonds, Washington Design Recommendations III. DESIGN RECOMMENDATIONS 8.0 INTRODUCTION Our explorations indicate that, from a geotechnical standpoint, the parcel is suitable for the proposed project provided the risks discussed are accepted and the recommendations contained herein are properly followed. The foundation -bearing stratum is moderately deep, ranging from roughly 13 to 29 feet or more below present surface grade. Due to the depth of the bearing soils, a driven pipe pile -supported foundation is recommended for the residence to mitigate the risk of post -construction settlements. 9.0 SITE PREPARATION Site preparation for the proposed residence should include removal of all trees, brush, debris, and any other deleterious material from the area of the planned building footprint. We recommend that any organic topsoil should be stripped from the entire planned building footprint. The sediments encountered in the exploration borings contained a variable percentage of fine-grained material, which makes them moisture -sensitive and subject to disturbance when wet. The contractor must use care during site preparation and excavation operations so that the underlying soils are not softened. If disturbance occurs, the softened soils should be removed, and the area brought to grade with structural fill. If construction will occur during the wet season, we recommend that the building footprint area be graded smooth and sloped to drain. The building footprint should then be blanketed with a minimum of 6 inches of clean, crushed, 2-inch rock (railroad ballast). Following placement of the crushed rock, a pipe pile foundation may be installed. AESI can provide field design recommendations for these areas, if needed. 9.1 Temporary Cut Slopes In our opinion, stable, temporary construction slopes should be the responsibility of the contractor and should be determined during construction. For planning purposes, we anticipate that temporary, unsupported cut slopes in unsaturated existing fill or landslide deposits, can be planned at a maximum slope of 1.5H:1V (Horizontal:Vertical). Flatter, temporary cut slopes will be needed if drainage is not installed prior to excavation and groundwater seepage is encountered. As is typical with earthwork operations, some sloughing and raveling may occur, January 10, 2020 ASSOCIATED EARTH SCIENCES, INC. A WRIMS11d - 20190294EO01 -4 Page 12 Subsurface Exploration, Geologic Hazard, and Maupin—Crouch Residence Geotechnical Engineering Report Edmonds, Washington Design Recommendations and cut slopes may have to be adjusted in the field. In addition, WISHA/OSHA regulations should be followed at all times. Permanent, unsupported cut or structural fill slopes should not exceed a gradient of 2H:1V. 10.0 STRUCTURAL FILL Structural fill may be necessary to establish desired grades or to backfill around foundations and utilities. All references to structural fill in this report refer to subgrade preparation, fill type, placement, and compaction of materials, as discussed in this section. If a percentage of compaction is specified under another section of this report, the value given in that section should be used. After overexcavation/stripping has been performed to the satisfaction of the geotechnical engineer/engineering geologist, the upper 12 inches of exposed ground should be recompacted to a firm and unyielding condition. If the subgrade contains too much moisture, adequate recompaction may be difficult or impossible to obtain and should probably not be attempted. In lieu of recompaction, the area to receive fill should be blanketed with washed rock or quarry spalls to act as a capillary break between the new fill and the wet subgrade. Where the exposed ground remains soft and further overexcavation is impractical, placement of an engineering stabilization fabric may be necessary to prevent contamination of the free -draining layer by silt migration from below. After stripping and subgrade preparation of the exposed ground is approved, or a free -draining rock course is laid, structural fill may be placed to attain desired grades. Structural fill is defined as non -organic soil, acceptable to the geotechnical engineer, placed in maximum 8-inch loose lifts, with each lift being compacted to 95 percent of the modified Proctor maximum density using ASTM D-1557 as the standard. The contractor should note that any proposed fill soils must be evaluated by AESI prior to their use in fills. This would require that we have a sample of the material at least 3 business days in advance to perform a Proctor test and determine its field compaction standard. Soils in which the amount of fine-grained material (smaller than the No.200 sieve) is greater than approximately 5 percent (measured on the minus No. 4 sieve size) should be considered moisture -sensitive. Use of moisture -sensitive soils in structural fills should be limited to favorable dry weather conditions. The on -site soils contained variable amounts of silt and are considered moisture -sensitive, and we expect that this material may be difficult to compact to structural fill specifications, particularly during and following wet weather. If proper compaction of the on -site soils cannot be achieved, we recommend that a select, import January 10, 2020 ASSOCIATED EARTH SCIENCES, INC. A WRIMS11d - 20190294EO01 -4 Page 13 Subsurface Exploration, Geologic Hazard, and Maupin—Crouch Residence Geotechnical Engineering Report Edmonds, Washington Design Recommendations material consisting of a clean, free -draining gravel and/or sand be used. Free -draining fill consists of non -organic soil with the amount of fine-grained material limited to 5 percent by weight when measured on the minus No. 4 sieve fraction. A representative from our firm should inspect the stripped subgrade and be present during placement of structural fill to observe the work and perform a representative number of in -place density tests. In this way, the adequacy of the earthwork may be evaluated as filling progresses and any problem areas may be corrected at that time. It is important to understand that taking random compaction tests on a part-time basis will not assure uniformity or acceptable performance of a fill. As such, we are available to aid the owner in developing a suitable monitoring and testing frequency. 11.0 FOUNDATIONS We recommend the use of steel pipe piles to support new foundations. Recommendations for pipe pile foundations are included in this section. For preliminary estimating purposes, pile lengths in the 20- to 40-foot range may be assumed. Actual pile lengths may differ significantly from the estimated range depending on local variations in soil conditions, pile size, and driving equipment used. Pile lengths can best be determined by driving a series of test piles. If the new home is located closer to the western steep slope, then the existing home additional horizontal pile surcharges may be necessary to mitigate seismic slope movement. AESI should be allowed to review the recommendations in this section once project plans have been finalized. 11.1 Pipe Pile Foundations Pipe piles should consist of 3-, 4-, or 6-inch-diameter pipe, depending on the required structural loads. The piles should be galvanized steel pipe, driven with a suitable hydraulic hammer to the refusal criteria shown in Table 2. The following table provides required minimum hammer weights, refusal criteria, and allowable loads for pipe piles. January 10, 2020 ASSOCIATED EARTH SCIENCES, INC. A WRIMS11d - 20190294EO01 -4 Page 14 Subsurface Exploration, Geologic Hazard, and Maupin—Crouch Residence Geotechnical Engineering Report Edmonds, Washington Design Recommendations Table 2 Pipe Pile Design Parameters Allowable Axial Pipe Minimum Hammer Refusal Compressive Diameter Wall Size Criterion* Load** (inches) Thickness (pounds) (seconds) (kips) 3 Schedule 40 400 25 10 4 Schedule 40 650 20 20 6 Schedule 40 1,500 15 30 * Refusal is defined as less than 1 inch of penetration in "X" seconds under constant driving. ** Allowable load to be verified by load tests in accordance with ASTM International (ASTM) D-1143 "quick load test." Anticipated settlement of pile -supported foundations should be less than % inch. Pile installation must be observed by AESI to verify that the design bearing capacity of the piles has been attained and that construction conforms to the recommendations contained herein. The City of Edmonds may also require such inspections. Lateral resistance can be derived from passive soil resistance against the buried portion of the foundation (i.e., the grade beam) or from the installation of batter piles. A passive equivalent fluid of 200 pounds per cubic foot (pcf) can be used to account for lateral resistance. Lateral resistance for batter piles should be taken as the horizontal component of the axial pile load. Batter piles are typically installed at 1H:4V inclination. Pile Inspections The actual total length of each pile may be adjusted in the field based on required capacity and conditions encountered during driving. Since completion of the pile takes place below ground, the judgment and experience of the geotechnical engineer or their field representative must be used as a basis for determining the required penetration and acceptability of each pile. Consequently, use of the presented pile capacities in the design requires that the installation of all piles be observed by a qualified geotechnical engineer or engineering geologist from our firm, who can interpret and collect the installation data and examine the contractor's operations. AESI, acting as the owner's field representative, would determine the required lengths of the piles and keep records of pertinent installation data. A final summary report would then be distributed following completion of pile installation. Load testing should be performed to verify that the design bearing capacity of the piles has been attained. Because of the variation in the soil types and their densities, we recommend that AESI monitor the load testing program. A common pile load testing program would consist of one or more 200-percent verification tests of the design bearing capacity of the pile in the January 10, 2020 ASSOCIATED EARTH SCIENCES, INC. A WRIMS11d - 20190294EO01 -4 Page 15 Subsurface Exploration, Geologic Hazard, and Maupin—Crouch Residence Geotechnical Engineering Report Edmonds, Washington Design Recommendations soil. Verification test piles are usually loaded in 25-percent increments that are held for 2 minutes up to the final load of 200-percent design load. The 200-percent load is commonly held for 20 minutes and creep -measured. The load is then reduced by 25-percent increments to evaluate the effect of elasticity in the pile to overall displacement. 12.0 LATERAL WALL PRESSURES All backfill behind retaining walls or around foundation units should be placed as per our recommendations for structural fill and as described in this section of the report. Horizontally backfilled retaining walls that are free to yield laterally at least 0.1 percent of their height may be designed using an equivalent fluid equal to 35 pcf. Fully restrained, horizontally backfilled, rigid walls that cannot yield should be designed for an equivalent fluid of 50 pcf. If roadways, parking areas, or other areas subject to vehicular traffic are adjacent to retaining walls, a surcharge equivalent to 2 feet of soil should be added to the wall height in determining lateral design forces. Retaining walls that retain sloping backfill at a maximum angle of 2H:1V should be designed using an equivalent fluid pressure of 55 pcf for yielding conditions or 75 pcf for fully restrained conditions. In accordance with the 2015 IBC, retaining wall design should include seismic design parameters. Based on the site soils and assumed wall backfill materials, we recommend a seismic surcharge pressure in addition to the equivalent fluid pressures presented above. A rectangular pressure distribution of 5H and 10H pounds per square foot (psf) (where H is the height of the wall in feet) should be included in design for "active" and "at -rest" loading conditions, respectively. The resultant of the rectangular seismic surcharge should be applied at the midpoint of the walls. The lateral pressures presented above are based on the conditions of a uniform horizontal backfill consisting of the on -site, natural, glacial sediments or imported sand and gravel compacted to 90 percent of ASTM D-1557. A higher degree of compaction is not recommended, as this will increase the pressure acting on the wall. Footing drains must be provided for all retaining walls, as discussed under the "Drainage Considerations" section of this report. It is imperative that proper drainage be provided so that hydrostatic pressures do not develop against the walls. This would involve installation of a minimum, 1-foot-wide blanket drain to within 1 foot of the ground surface using imported, washed gravel against the walls placed to be continuous with the footing drain. January 10, 2020 ASSOCIATED EARTH SCIENCES, INC. A WRIMS11d - 20190294EO01 -4 Page 16 Subsurface Exploration, Geologic Hazard, and Maupin—Crouch Residence Geotechnical Engineering Report Edmonds, Washington Design Recommendations 12.1 Passive Resistance and Friction Factors Retaining wall grade beams/keyways cast directly against undisturbed dense soils in a trench may be designed for passive resistance against lateral translation using an allowable equivalent fluid equal to 200 pcf. The passive equivalent fluid pressure diagram begins at the top of the buried portion of grade beam. Since the structure will be pile -supported, we do not recommend using base friction for resistance to lateral loads. 13.0 FLOOR SUPPORT Due to the loose nature of the subgrade soils, we recommend that structural support be provided for settlement -sensitive, slab -on -grade floors. The floors should be cast atop a minimum of 4 inches of washed pea gravel or washed crushed rock to act as a capillary break where moisture migration through the slabs is to be controlled. The capillary break material should be overlain by a 10-mil-thick vapor retarder material prior to concrete placement. American Concrete Institute (ACI) recommendations should be followed for all concrete placement. 14.0 DRAINAGE CONSIDERATIONS All retaining and perimeter foundation walls should be provided with a drain at the base of the footing elevation. Drains should consist of rigid, perforated, polyvinyl chloride (PVC) pipe surrounded by washed pea gravel. The level of the perforations in the pipe should be set at or slightly below the bottom of the footing grade beam, and the drains should be constructed with sufficient gradient to allow gravity discharge away from the building. In addition, all retaining walls should be lined with a minimum, 12-inch-thick, washed gravel blanket that extends to within 1 foot of the surface and is continuous with the foundation drain. Roof and surface runoff should not discharge into the foundation drain system, but should be handled by a separate, rigid, tightline drain. In planning, exterior grades adjacent to walls should be sloped downward away from the structure to achieve surface drainage. All collected runoff must be tightlined to a City -approved location. 15.0 PROJECT DESIGN AND CONSTRUCTION MONITORING Our recommendations are preliminary in that definite building locations and construction details have not been finalized at the time of this report. We are available to provide additional geotechnical consultation as the project design develops and possibly changes from that upon January 10, 2020 ASSOCIATED EARTH SCIENCES, INC. A WRIMS11d - 20190294EO01 -4 Page 17 Subsurface Exploration, Geologic Hazard, and Maupin—Crouch Residence Geotechnical Engineering Report Edmonds, Washington Design Recommendations which this report is based. If significant changes in grading are made, we recommend that AESI perform a geotechnical review of the plans prior to final design completion. In this way, our earthwork and foundation recommendations may be properly interpreted and implemented in the design. We are also available to provide geotechnical engineering and monitoring services during construction. The integrity of the foundations depends on proper site preparation and construction procedures. In addition, engineering decisions may have to be made in the field in the event that variations in subsurface conditions become apparent. Construction monitoring services are not part of this current scope of work. If these services are desired, please let us know, and we will prepare a proposal. We have enjoyed working with you on this study and are confident these recommendations will aid in the successful completion of your project. If you should have any questions or require further assistance, please do not hesitate to call. Sincerely, ASSOCIATED EARTH SCIENCES, INC. Kirkland, Washington Bruce L. Blyton, P.E / Senior Principal Engineer Anthony W. Romanick Senior Project Engineer Attachments: Figure 1: Vicinity Map Figure 2: Existing Site and Exploration Plan Appendix A: Exploration Logs Appendix B: SLOPE/W Results January 10, 2020 ASSOCIATED EARTH SCIENCES, INC. A WRIMS11d - 20190294EO01-4 Page 18 A A 1 J I . MM VIEWLAND WAY% nt Snohomish County — 13 R • �' eagal'i r '•f ! �� I _ 9l Iark �rf'�`✓��`�` II a .� ®-- Jr El lw 161 17 .17 99 I. ' UNINCOR-RORATE'D. J •-� Copyright:© 2013 Natidnal Geogra;phlc So�iety, i-cubed a s s o c i a t e d N earth sciences A e incorporated 0 1000 2000 VICINITY MAP FEET DATA SOURCES/REFERENCES: MAUPIN-GROUCH RESIDENCE USGS: 7.5' SERIES TOPOGRAPHIC MAPS, ESRI/1-CUBED/NATIONAL NOTE: BLACK AND WHITE GEOGRAPHIC SOCIETY2013 REPRODUCTION OF THIS COLOR EDMONDS, WASHINGTON SNOHOMISH CO: STREETS, CITY LIMITS, PARCELS, 2/19 ORIGINAL MAY REDUCE ITS EFFECTIVENESS AND LEAD TO PROD NO. DATE: FIGURE: LOCATIONS AND DISTANCES SHOWN ARE APPROXIMATE INCORRECT INTERPRETATION 190294EO01 9/19 1 is a 10 SITE O EXPLORATION BORING CROSS SECTION CONTOUR 10 FT CONTOUR 2 FT DATA SOURCES/REFERENCES: WA STATE LIDAR PORTAL: NORTH PUGET SOUND 2016 CONTOURS FROM LIDAR SNOHOMISH CO: STREETS, PARCELS 1/18 AERIAL: KING CO., PICTOMETRY INT. 2017 LOCATIONS AND DISTANCES SHOWN ARE APPROXIMATE KAI -- r >, ; i a s s o c i a t e d N earth sciences i n c o r p o r a t e d 50 EXISTING SITE AND Feet EXPLORATION PLAN MAUPIN-CROUCH RESIDENCE NOTE: BLACK AND WHITE REPRODUCTION OF THIS COLOR EVERETT, WASHINGTON ORIGINAL MAY REDUCE ITS EFF ECTIVENESS AND LEAD TO PROJ NO. DATE: FIGURE: INCORRECT INTERPRETATION 190294EO01 10/19 2 APPENDIX A Exploration Logs associated Exploration Borin earth sciences Project Number Exploration Number Sheet Incorporated 190294EO01 EB-1 1of1 Project Name Maupin-Crouch Residence Ground Surface Elevation (ft) —238 Location Edmonds, WA Datum NAVD 88 Driller/Equipment Geologic Drill / Mini -Track Date Start/Finish 9/19/1Q 9/1 /19 Hammer Weight/Drop 140# / 30 Hole Diameter (in) F E cL c a) n � J U) 3 Blows/Foot w d) a S 12 �, 0 u) o o T in DESCRIPTION " m m r ° 10 20 30 40 Grass / Topsoil - 4 inches S-1 2 2 $ Fill Slightly moist, light brown to gray with minor oxidation in upper 6 inches, 21 very silty, fine SAND, some medium sand, some gravel; minor organics; no S-2 :. apparent structure (SM). 10 15 s Moist, brownish gray, very silty, fine SAND, trace gravel; minor mottling; 13 broken gravel in sampler, blowcounts likely overstated; low recovery; no 5 apparent structure (SM). 3 S 3 : .. Gravelly drilling at 4 feet -1 5 9 Landslide Deposits 4 Moist to very moist, gray to dark gray with zones of moderate oxidation, very silty, fine to medium SAND, some gravel; layers of organics and woody debris; disturbed texture (SM). 10 S-4 Very moist to wet, light brownish gray to brown with bands of minor to 3 A13 moderate oxidation throughout, very silty, fine to medium SAND, some 5 gravel; disturbed texture (SM). 8 --———————————————————————— — — — — —— X Pre -Fraser Nonglacial Deposits Water on rods at -13 feet. 15 S-5 Wet, gray to brownish gray, fine SAND, trace to some silt, trace gravel; 5 A massive; minor mica flakes (SP/SP-SM). 8 19 11 20 S 6 Wet, gray, fine SAND, trace to some silt, trace gravel; minor to moderate 11 mica; massive (SP-SM/SP). 18 7 29 25 Wet, gray, fine to medium SAND, trace to some silt, trace to some gravel; S-7 _ minor to moderate mica content; some faint angular stratification 12 (SP-SM/SP). 23 58 35 Bottom of exploration boring at 26.5 feet Groundwater encountered at -13 feet. 30 35 40 Sampler Type (ST): m 2" OD Split Spoon Sampler (SPT) ❑ No Recovery M - Moisture Logged by: TG m 3" OD Split Spoon Sampler (D & M) Ring Sample Q Water Level Q Approved by: JHS ® Grab Sample 0 Shelby Tube Sample 1 Water Level at time of drilling (ATD) ass 0cl a t e d Exploration Boring earth sciences Project Number Exploration Number Sheet incorporated 190294EO01 EB-2 1 of Project Name Maupin-Crouch Residence Ground Surface Elevation (ft) —237 Location Edmonds, WA Datum NAVI71RR Driller/Equipment Geologic Drill / Mini -Track Date Start/Finish 9/19/1 A 9/19/1 A Hammer Weight/Drop 140# / 30 Hole Diameter (in) F m C U O 0 c O � a) > J °' Zo N Blows/Foot Y U a) S m> >N >E�5o p T � (D rn DESCRIPTION o C) @ 3: m ° 10 20 30 40 Topsoil - -4 inches S-1 _ - _- 1 10 20 30 Fill Slightly moist, light brownish gray with minor oxidation, very silty, fine to = medium SAND, some gravel; minor organics and rootlets; no apparent S-2 -=--= = structure (SM). 11 10 A 19 - Slightly moist to moist, light brownish gray with minor oxidation, very silty, 9 9 fine to medium SAND, some gravel; no apparent structure (SM). 5 -- = - - `Gravelly drilling at 4 feet. -J S-3 - - Landslide Deposits q _ Moist, brownish gray to dark gray with minor oxidation, silty, fine to medium 4 _ SAND, trace gravel; minor wood debris; minor organics; disturbed texture (SM). 10 S-4 = _= - Moist to very moist, dark gray to brownish gray with zones of minor to 3 Al _ moderate oxidation, silty, fine to medium SAND, some gravel; disturbed 5 _- -- = texture; minor organics (SM). 10 15 S 5 Very moist, dark gray, very silty, fine to medium SAND, some gravel; s -= - = disturbed texture; minor organics and organic odor (SM). 2 5 20 S 6 As above; contains woody debris. 5 - _ _- 6 11 _- - 5 Driller reports gravelly drilling at 24 feet. 25 S"� = _ Very moist to wet, gray to dark gray, silty, fine to medium SAND, some 10 gravel; minor organics; pockets of sandy silt; disturbed texture (SM). 10 20 10 : Water on rods at 29 feet. T 30 Pre -Fraser Nonglacial Deposits S-g Wet, dark gray, gravelly, fine to coarse SAND, some silt; quartz 4 A44 fragments?; moderately stratified (SP-SM). 11 33 35 S-g Wet, dark gray, sandy, SILT, trace gravel; minor mica content; single 8 A3 interbed (-3 inches thick) of silty, fine to medium sand (SM); minor fine 14 organics within sandy silt; organic odor; faintly laminated (ML). 22 40 S-10 Wet, dark gray, fine sandy, SILT, trace medium sand; minor to moderate 10 mica content; faint laminations (ML). 16 a1 25 Bottom of exploration boring at 41.5 feet Groundwater encountered at -29 feet. Sampler Type (ST): m 2" OD Split Spoon Sampler (SPT) ❑ No Recovery M - Moisture Logged by: TG ® 3" OD Split Spoon Sampler (D & M) Ring Sample �Z Water Level () Approved by: JHS IN Grab Sample Shelby Tube Sample 1 Water Level at time of drilling (ATD) APPENDIX 6 SLOPE/W Results W 61 Color Name Unit Cohesion' Phi' Piezometric Weight (psf) (') Line (Pcf) ■ Fill 120 50 33 1 Landslide 120 50 31 1 Deposits Pre -Fraser 130 100 36 1 Sediments 1.2 Maupin-Crouch Residence 190294EO01 Slope Profile Seismic vv 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130 135 140 145 150 155 160 165 170 175 180 185 190 195 200 A Distance (ft.) A' W 61 Color Name Unit Cohesion' Phi' Piezometric Weight (psf) (') Line (Pcf) ■ Fill 120 50 33 1 Landslide 120 50 31 1 Deposits ❑Pre -Fraser 130 100 36 1 Sediments 1.0 Maupin-Crouch Residence 190294EO01 Slope Profile Seismic vv 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130 135 140 145 150 155 160 165 170 175 180 185 190 195 200 A Distance (ft.) A' W 61 Color Name Unit Cohesion' Phi' Piezometric Weight (psf) (') Line (Pcf) ■ Fill 120 50 33 1 Landslide 120 50 31 1 Deposits Pre -Fraser 130 100 36 1 Sediments 1.9 Maupin-Crouch Residence 190294EO01 Slope Profile Static vv 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130 135 140 145 150 155 160 165 170 175 180 185 190 195 200 A Distance (ft.) A' W 61 Color Name Unit Cohesion' Phi' Piezometric Weight (psf) (') Line (Pcf) ■ Fill 120 50 33 1 Landslide 120 50 31 1 Deposits ❑Pre -Fraser 130 100 36 1 Sediments 1.5 Maupin-Crouch Residence 190294EO01 Slope Profile Static vv 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130 135 140 145 150 155 160 165 170 175 180 185 190 195 200 A Distance (ft.) A' USDA United States Department of Agriculture N RCS Natural Resources Conservation Service A product of the National Custom Soil Resource Cooperative Soil Survey, a joint effort of the United Report for States Department of Agriculture and other Snohomish County Federal agencies, State agencies including the Agricultural Experiment Area, Washington Stations, and local participants Crouch-Maupin Residence X,.y O or �-'- is 1 February 27, 2020 ry ryN N 47° 49' 12" N Custom Soil Resource Report Soil Map TM 547M 54-M3 547938 547943 547948 547%3 3. ,. a til . k T • j 1 r . ■m 1 .� 90 r F r _ 1�• 1 f # �r Soil M-ap may not be-va-I;id at this scale. 47° 49' 10" N 547913 547918 547923 5479M 547933 547938 3 " Map Scale: 1:248 if printed on A landscape (11" x 8.5') sheet Meters N 0 3 7 14 21 Feet 0 10 20 40 60 Map projection: Web Mercator Comer coordinates: WGS84 Edge tics: UTM Zone 1ON WGS84 1 -1 M" aim 54-1943 547948 547953 54M 3 ryN N 547963 47° 49' 12" N 1 r T - 47' 49' 10" N 547963 3 N LAI MAP LEGEND Area of Interest (AOI) Area of Interest (AOI) Soils 0 Soil Map Unit Polygons rwr Soil Map Unit Lines Soil Map Unit Points Special Point Features Uo Blowout ® Borrow Pit Clay Spot Closed Depression Gravel Pit Gravelly Spot Landfill Lava Flow Marsh or swamp + Mine or Quarry Miscellaneous Water Perennial Water Rock Outcrop Saline Spot d Sandy Spot Severely Eroded Spot Sinkhole Slide or Slip oa Sodic Spot Custom Soil Resource Report MAP INFORMATION Spoil Area The soil surveys that comprise your AOI were mapped at 1:24,000. Stony Spot Very Stony Spot Warning: Soil Map may not be valid at this scale. Wet Spot Enlargement of maps beyond the scale of mapping can cause Other misunderstanding of the detail of mapping and accuracy of soil .- Special Line Features line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed Water Features scale. Streams and Canals Transportation Please rely on the bar scale on each map sheet for map 1 1 F Rails measurements. Interstate Highways Source of Map: Natural Resources Conservation Service r.x US Routes Web Soil Survey URL: Coordinate System: Web Mercator (EPSG:3857) Major Roads Local Roads Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts Background distance and area. A projection that preserves area, such as the Aerial Photography Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: Snohomish County Area, Washington Survey Area Data: Version 21, Sep 16, 2019 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Sep 2, 2018—Sep 25, 2018 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. Custom Soil Resource Report Map Unit Legend Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI 3 Alderwood gravelly sandy loam, 15 to 30 percent slopes Totals for Area of Interest 0.3 0.3 100.0% 100.0% Map Unit Descriptions The map units delineated on the detailed soil maps in a soil survey represent the soils or miscellaneous areas in the survey area. The map unit descriptions, along with the maps, can be used to determine the composition and properties of a unit. A map unit delineation on a soil map represents an area dominated by one or more major kinds of soil or miscellaneous areas. A map unit is identified and named according to the taxonomic classification of the dominant soils. Within a taxonomic class there are precisely defined limits for the properties of the soils. On the landscape, however, the soils are natural phenomena, and they have the characteristic variability of all natural phenomena. Thus, the range of some observed properties may extend beyond the limits defined for a taxonomic class. Areas of soils of a single taxonomic class rarely, if ever, can be mapped without including areas of other taxonomic classes. Consequently, every map unit is made up of the soils or miscellaneous areas for which it is named and some minor components that belong to taxonomic classes other than those of the major soils. Most minor soils have properties similar to those of the dominant soil or soils in the map unit, and thus they do not affect use and management. These are called noncontrasting, or similar, components. They may or may not be mentioned in a particular map unit description. Other minor components, however, have properties and behavioral characteristics divergent enough to affect use or to require different management. These are called contrasting, or dissimilar, components. They generally are in small areas and could not be mapped separately because of the scale used. Some small areas of strongly contrasting soils or miscellaneous areas are identified by a special symbol on the maps. If included in the database for a given area, the contrasting minor components are identified in the map unit descriptions along with some characteristics of each. A few areas of minor components may not have been observed, and consequently they are not mentioned in the descriptions, especially where the pattern was so complex that it was impractical to make enough observations to identify all the soils and miscellaneous areas on the landscape. The presence of minor components in a map unit in no way diminishes the usefulness or accuracy of the data. The objective of mapping is not to delineate pure taxonomic classes but rather to separate the landscape into landforms or landform segments that have similar use and management requirements. The delineation of such segments on the map provides sufficient information for the development of resource plans. If intensive use of small areas is planned, however, onsite investigation is needed to define and locate the soils and miscellaneous areas. Custom Soil Resource Report An identifying symbol precedes the map unit name in the map unit descriptions. Each description includes general facts about the unit and gives important soil properties and qualities. Soils that have profiles that are almost alike make up a soil series. Except for differences in texture of the surface layer, all the soils of a series have major horizons that are similar in composition, thickness, and arrangement. Soils of one series can differ in texture of the surface layer, slope, stoniness, salinity, degree of erosion, and other characteristics that affect their use. On the basis of such differences, a soil series is divided into soil phases. Most of the areas shown on the detailed soil maps are phases of soil series. The name of a soil phase commonly indicates a feature that affects use or management. For example, Alpha silt loam, 0 to 2 percent slopes, is a phase of the Alpha series. Some map units are made up of two or more major soils or miscellaneous areas. These map units are complexes, associations, or undifferentiated groups. A complex consists of two or more soils or miscellaneous areas in such an intricate pattern or in such small areas that they cannot be shown separately on the maps. The pattern and proportion of the soils or miscellaneous areas are somewhat similar in all areas. Alpha -Beta complex, 0 to 6 percent slopes, is an example. An association is made up of two or more geographically associated soils or miscellaneous areas that are shown as one unit on the maps. Because of present or anticipated uses of the map units in the survey area, it was not considered practical or necessary to map the soils or miscellaneous areas separately. The pattern and relative proportion of the soils or miscellaneous areas are somewhat similar. Alpha -Beta association, 0 to 2 percent slopes, is an example. An undifferentiated group is made up of two or more soils or miscellaneous areas that could be mapped individually but are mapped as one unit because similar interpretations can be made for use and management. The pattern and proportion of the soils or miscellaneous areas in a mapped area are not uniform. An area can be made up of only one of the major soils or miscellaneous areas, or it can be made up of all of them. Alpha and Beta soils, 0 to 2 percent slopes, is an example. Some surveys include miscellaneous areas. Such areas have little or no soil material and support little or no vegetation. Rock outcrop is an example. Custom Soil Resource Report Snohomish County Area, Washington 3—Alderwood gravelly sandy loam, 15 to 30 percent slopes Map Unit Setting National map unit symbol: 2t627 Elevation: 0 to 1,000 feet Mean annual precipitation: 25 to 60 inches Mean annual air temperature: 46 to 52 degrees F Frost -free period: 160 to 240 days Farmland classification: Farmland of statewide importance Map Unit Composition Alderwood and similar soils: 85 percent Minor components: 15 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Alderwood Setting Landform: Ridges, hills Landform position (two-dimensional): Backslope Landform position (three-dimensional): Side slope, nose slope, talf Down -slope shape: Linear, convex Across -slope shape: Convex Parent material: Glacial drift and/or glacial outwash over dense glaciomarine deposits Typical profile A - 0 to 7 inches: gravelly sandy loam Bw1 - 7 to 21 inches: very gravelly sandy loam Bw2 - 21 to 30 inches: very gravelly sandy loam Bg - 30 to 35 inches: very gravelly sandy loam 2Cd1 - 35 to 43 inches: very gravelly sandy loam 2Cd2 - 43 to 59 inches: very gravelly sandy loam Properties and qualities Slope: 15 to 30 percent Depth to restrictive feature: 20 to 39 inches to densic material Natural drainage class: Moderately well drained Capacity of the most limiting layer to transmit water (Ksat): Very low to moderately low (0.00 to 0.06 in/hr) Depth to water table: About 18 to 37 inches Frequency of flooding: None Frequency of ponding: None Available water storage in profile: Very low (about 2.7 inches) Interpretive groups Land capability classification (irrigated): None specified Land capability classification (nonirrigated): 4e Hydrologic Soil Group: B Forage suitability group: Limited Depth Soils (G002XN302WA), Limited Depth Soils (G002XF303WA), Limited Depth Soils (G002XS301 WA) Hydric soil rating: No Custom Soil Resource Report Minor Components Everett Percent of map unit: 5 percent Landform: Karnes, eskers, moraines Landform position (two-dimensional): Backslope Landform position (three-dimensional): Side slope Down -slope shape: Convex Across -slope shape: Convex Hydric soil rating: No Indianola Percent of map unit: 5 percent Landform: Eskers, kames, terraces Landform position (three-dimensional): Tread Down -slope shape: Linear Across -slope shape: Linear Hydric soil rating: No Shalcar Percent of map unit: 3 percent Landform: Depressions Landform position (three-dimensional): Dip Down -slope shape: Concave Across -slope shape: Concave Hydric soil rating: Yes Norma Percent of map unit: 2 percent Landform: Depressions, drainageways Landform position (three-dimensional): Dip Down -slope shape: Concave, linear Across -slope shape: Concave Hydric soil rating: Yes Crouch-Maupin Residence - CG #20008.20 Drainage Report June 2, 2020 Section VI, Page 1 Section VI — Other Permits Section VI Summarv: Narrative The site will not require permits beyond those from the City of Edmonds. C � ENGINEERING 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Crouch-Maupin Residence - CG #20008.20 Drainage Report June 2, 2020 Section VII, Page 1 Section VII — Bond Quantities. Declaration of Covenant. & Operation and Maintenance Manual Section VII Summarv: Narrative The Bond Quantity Worksheet is a standalone document that can also be submitted to the City of Edmonds separately from this document. A Declaration of Covenant is provided for the on -site BMPs proposed. The Operation and Maintenance Manual is a standalone document that will be given to the owner(s) following the construction of the project. The maintenance covenant contained herein is for the Crouch-Maupin Residence single-family residence project. The contractor will be responsible for the maintenance and operation of all stormwater structures and BMPs requiring maintenance during construction and, after construction, responsibility will pass to the home owner(s). The project contractor will be responsible for passing along the information in this maintenance manual to the owner(s). Upon request by the City, it shall be made available for their inspection. It is generally expected that few to none of these defects will be present upon the yearly inspection of each facility. C 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com After recording return to: City Clerk City of Edmonds 121 Fifth Avenue North Edmonds, WA 98020 Document Title(s) Declaration of Covenant - Private Stormwater Facility Reference Number(s) of Related Documents City of Edmonds (permit number) Grantor(s) (Last, First and Middle Initial) Crouch, Peter D. Maupin, Terri K. Grantee(s) (Last, First and Middle Initial) City of Edmonds Legal Description (abbreviated form; i.e., lot, plat or section, township, range, quarter/quarter) Lot 18, Viewland Heights, NE 1/4, NE 1/4, Section 24, Township 27 North, Range 5 East Assessor's Property Tax Parcel/Account Number at the Time of Recording: 006-066-0000-1800 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 Facility WHEREAS, the undersigned Declarant(s) have installed one or more stormwater facilities under Edmonds Community Development Code Chapter 18.30 known as a "low impact development best management practices (LID BMP)" as selected below: ❑ Permeable Pavement ❑ Rain Garden / Bioretention Cell ❑ Drywell ❑ Infiltration Trench ❑ Gravelless Chamber ® Other Detention Pipe WHEREAS, the City of Edmonds has allowed installation of the LID 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: 1141 Viewland Way 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: Declarant(s) warrant that he/she/they are the owners 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 an "LID 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. "Low impact development" means development conducted in a way that seeks to minimize or completely prevent alterations to the natural hydrology of the site. Low impact development includes site planning and design to reduce alterations of natural soil and vegetation cover, minimize impervious surfaces, and specific practices that help to replicate natural hydrology such as permeable pavements, green roofs, soil amendments, bioretention systems, and dispersion of runoff. 3. The Owners shall maintain the size, placement, and design of the LID BMP as depicted on the approved site plan, Exhibit B, 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 LID BMP is located. All costs of maintenance and repair shall be the sole responsibility of the Owners. 4. The Owners shall inspect LID 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 LID 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 LID BMP facility. If, as the result of any such inspection, the City of Edmonds determines that the LID BMP is in disrepair, requires maintenance or repair, or is otherwise not functioning as provided in the BMP 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. 6. If the City of Edmonds determines that the LID 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 violator 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 LID BMP(s), the installation and presence of the LID 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 LID 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 LID BMP(s). 8. 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)} 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 signed the same as his/her/their free and voluntary act and deed, for the uses and purposes therein mentioned. SUBSCRIBED AND SWORN before me this day of , 201_ (Signature) (Name legibly printed or stamped) Notary Public in and for the State of Washington. Residing at: My commission expires Exhibit A Legal description (PER STATUTORY WARRANTY DEED RECORDING# 201808170192) LOT 18, VIEWLAND HEIGHTS, ACCORDING TO THE PLAT THEREOF RECORDED IN VOLUME 13 OF PLATS, PAGE 84, RECORDS OF SNOHOMISH COUNTY, WASHINGTON. SITUATE IN THE COUNTY OF SNOHOMISH, STATE OF WASHINGTON. Exhibit B Site Plan 14 RN I zo• PIN / /\ — N 88°3898' w= u /� I 8 �— d 14 FlRI$\� \ W I I _ 1 u To,/ zi CATCH BASIN \ DETENTION �l 1 � PIPE SYSTEM — �— 0 \ d w / A ATCH BASIN WITH / FLOW CON ROL / \ STRUeTU o SD SD _ .o n� VI AND WAY SD —SD —SD SD t Crouch-Maupin Residence - CG #20008.20 Drainage Report June 2, 2020 Section VII, Page 2 Crouch-Maupin Residence 1141 Viewland Way Edmonds, WA 98020 [a] "A -All V le] Z I_V 11 & f-1 I h"0 I_L L" W_L 14_l M Date: June 2020 C � 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Crouch-Maupin Residence - CG #20008.20 June 2, 2020 Drainage Report Section VII, Page 3 Operation and Maintenance Manual This Operation and Maintenance Manual has been created for the Crouch-Maupin Residence, a 0.11- acre building project on a 0.26-acre lot. The proposed storm system consists of a detention pipe system with a flow control structure that detains runoff from all impervious surfaces on -site. Included in this Operation and Maintenance Manual is an 11" x 17" grading and drainage plan sheet showing the location of the detention system. Please note that this map is generated during the design phase and may not reflect all changes made in permitting and construction. CG Engineering may be contacted for an updated copy of this map once the as -built drawings are completed for the site. The contractor will be responsible for the maintenance and operation of all stormwater structures and BMPs requiring maintenance during construction and, after construction, responsibility will pass to the property owner(s). A map of the project area can be seen on the following page in Figure VII-1. Included in this manual are maintenance sheets taken from the 2014 Stormwater Management Manual for Western Washington for the following facilities/activities: Area Drains: Concrete structures with metal grates that collect stormwater runoff from the site and act as junctions for storm conveyance pipes. See "No. 5" for maintenance. Trench Drains: Drainage pipes with metal grates crossing driveways to collect stormwater runoff. See "No. 5" for maintenance. Control Structures: Control structures are catch basins or manholes with a restrictor device for controlling outflow from a facility to meet the desired performance. See "No. 4" for maintenance. Closed Detention Systems (Detention Pipes/Tanks): Underground storage facilities typically constructed with large diameter corrugated metal or plastic pipe. See "No. 3" for maintenance. Vegetation Management: Landscaping can include grading, soil transfer, vegetation removal, pesticide and fertilizer applications, and watering. Stormwater contaminants include toxic organic compounds, heavy metals, oils, total suspended solids, coliform bacteria, fertilizers, and pesticides. Facilities shall be inspected for defects listed in the following facility sheets. Most maintenance tasks are generally reactionary to a defect being found, rather than a matter of constant upkeep. It is generally expected that few to none of these defects will be present upon the yearly inspection of each facility. The facility sheets list the potential conditions warranting maintenance and the expected result following any maintenance. Several engineer's notes for specific tasks are provided within the facility sheets. Unless otherwise noted on the facility sheets the maintenance tasks should be performed on an "as needed" basis: (a) when the described defect is visible to whomever performs the yearly inspection, or (b) should any defect become apparent between inspections. C 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Crouch-Maupin Residence - CG #20008.20 Drainage Report June 2, 2020 Section VII, Page 4 Figure VII-1. Map of project area (from Google Maps). C 4M 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com NE 1 /4, NE 1 /4, SECTION 24, TOWNSHIP 27 NORTH, RANGE 3 EAST, W.M. • / FOUND IRON PIPE \ I \ 0.29'E & 0.32'S OF I \ PROP COR 3 c FOUND REB�AR/CAP 22" MAP I I I I G\ LS 29276 I 1 %_ AP PCLOCO OF WATER 0.22'E & 0.42'S OF I / ( \ / \ \ / ' PROP COR ' \ / \ / I 3 / 40 /� II \ / \ \ _ I / _ y '/ O / PER CITY RECORDS � II \ / ROOF AND 2 \ _ `I' �I // 1 1 I FOOTING DRAINS e 1 / �� /yam tN'/LT ; 14" PIN I O I I 20" PIN I / \\ /� / rI _ N BE36'18- W 115.00' I - 1 �1 I I 1 @ O S% MIN-� _ _ 11 \ •I _� \ I I / I I J 1 IEWLAND WAY I I I \ $$ ,��$_ RF DRAIN IE: 236.30/ I I 010• FIR III-� ,JIO I I \ \ -�d�N' E1748009i \ 3 / iT 12 r FOUND MONIN CASE 2 + / �@RASS DISK) DOWN 0.6' II I �{�\� `ai39.08 - n/F IMF Zq / n/F �F \ I I /i \3 o I l G-GJ r+A II I I I I I I ~ 2 1.14 a v LL \ 238.78 4"AREA DRAIN RIM: 238.92 239.0 FTG DRAIN I236.47 T IIE INTO E: 2ury' I I v (TIE NTO ROOF DRAINS) 1 CONCRETE PAVERS k / PROPOSED SFR FIFE: 238.8 �38. 3 'N / PER ARCH I I I I AREA RAIN R.69 I I/I lII 2 IE: 236.36 CONCRETE PAVERS r a (TIE INTO ROOF DRAINS) PER ARCH 238.6 \ r I / *� APPROX LOC OF / I I I I I100 I 1238!8 a G�\.,\g0� / I I TI I / II I�- I I I �\ SIDE SEWER. PE ❑ r I I o II P PLO❑��(. / d/n- z3s.s clTr REcoos3 -� 39 / I I I� I O❑6 yyS �`51 / 1238. / 238.48 V' FIRbl �42B8.39 OOI I\ I �v /I \ I I I l FTG DRA71 • 6 2d8.39. / 3 I to - 238.8 / \ o 23i71/ C3 CONCRETE DRIVEWAY / 1 •r I I 3� 8 LF - 4" PVC @ 0.5% MIN i I I I ZI 9 -,e I lO 1238.JI5 TIE INTO d I 24 54" TYPE II CATCH BASIN I I I I I i ROOF FOR T I I d 4" TRAFI�14C RATED I 1 Iq I o 3� 12 LF ^ 4 PVC @ 0.5% RIM:237.75 I { 1 - v TRENCH RAIN 1r� IE(36"E): 232.0 I I I v ° 238.12 IE: 235.60 IE IS"N): 235.61 I I I Il I I a I 237.63 \\ 1 \ c�z4"AREADRAIN \ / 3 RIM: 237.0 (2) ROWS OF 19 LF ^"'• fM I 12" FIR IE: 235.67 RF DRAIN IE: 235.65 23796 / 2 36"0 N-12 DETENTIONS I I I y I 3 3e. PIPET 3 N I 1 / \ 54" TYPE II CB W/ FLOW 237.24 / \ 1 - CONNECTORS BETWEEN I _ ,I �- (_ 1 / FOUND REBAR/CAI' 3 / CONTROL STRUCTURE / V I 20 TIE FTG DRAIN TO FLOW I l - \ LS// 29276 RIM: 237.50 1 2 �I \ 6 �W / CONTLINE; RUCTURE / ) / P COR , IS(36 )5.232A 3. C3. rl \ I I NS I I W OUTLET LINE; IE: 230. / JE (12" S): 232.5 / 237.81 ✓ ✓ �J �� 237.61 APPROXIMATES 12" PIN i� SCO \ ✓\ BREAKNG GRADE /RIM=2267 / / I\ ) \ \ \ N ������ \\(z) 1� CED IF 8"CON .(E /s.) / / 1 \ /\ \ 237.46 IE 8'coNG(E) 1F 237.87 I 12" PIN,y�'/ =223.10'( \ \\ ee,y�/ -4\ \ \ i_ __I jac__1____ I 236.87 238.05 / / I 10" RINI 6• iiiiii DAYLIGHT PIPETODITCH Pp-p I VI _ p•36�1 ty+ W 11 00, - �� o T \ - / 20.O1Y� 3 AT APPROXIMATE IE: 229.0 \ E 12 ONC=2373' 10' FIR AND PROVIDE SPLASH i0P a0F SL SD SO Sz) I I I\ I I G // - PAD/QUARRY ROCK AT W W W� W W W \vy 8D W, I� -\ I 11 SO ANDS IMPERVIOUS SURFACES SURFACE SURFACE AREA (SF) STORMWATER CONTROL MEASURE NEW/REPLACED ROOF 3,504 RUNOFF ROUTEDTHROUGH ROOF DRAINSTO DETENTION SYSTEM NEW/REPLACED WALKWAYS 792 RUNOFF COLLECTED IN AREA DRAINS, CONVEYED TO ROOF DRAINS AND TO DETENTION SYSTEM NEW/REPLACED DRIVEWAY 460 RUNOFF COLLECTED INTRENCH DRAIN, CONVEVEDTO ROOF DRAINS AND TO DETENTION SYSTEM EXISTING DRIVE -TO REMAIN RUNOFF COLLECTEDINAREA DRAIN, CONVEYEDTOTRENCH 530 DRAIN, ROOF DRAINS AND TO DETENTION SYSTEM EXISTING DRIVEWAVTO REMAIN 250 RUNOFF SHEET FLOWS INTO STREET NOTE: TOTAL NEW/REPLACED IMPERVIOUS SURFACES ON -SITE ARE 4,756 SF C Im ENGINEERING 250 4TH AVE. S.. SUITE 200 EDMONDS, WASHINGTON 98020 PHONE (425) 778-8500 FAX (425) 778-5536 vvw/m I Q Z 4' DIA PERFORATED PVC PIPE Z O WITH 6 OF 1 MINUS GRAVEL 8" MIN FROM WOOD. w a ALL AROUND, WRAPPED IN SEE STRUCTURAL DRAWINGS z w NON WOVEN GEOTEXTILE FABRIC, O m SLOPE AT 0.5%MIN. TURN DOWN d 7 O w PERFORATIONS AS SHOWN FINISHED GRADE 6' DOWNSPOUT TIGHTLINE TO w o = Q a O U CONVEYANCE SYSTEM @ 0.5% MIN. PLACE NEXTTO FOOTING O O X _ DRAIN OR ASSHOWN ON GRADING & DRAINAGE PLAN m X CONTRACTOR MAY LOCATE ON EITHER SIDE OF FOOTING DRAIN) O� o O O te1 7 O O X X 00 Y ° O n O o� O0 ° o a LINE OF MAX EXCAVATION. o O a DESIGN: TAF I F SOIL IS OVEREXCAVATED, 0 0 oO n d REPLACE WITH LEAN MIX Ooo o O CONCRETE / DRAWN: ATE) FOOTING CHECK: JPU i 1 JOB NO: 20008.20 1 DATE: 03/23/2020 FOOTING AND ROOF DRAIN SECTION 2 SCALE: NTS CLASS 4000 CONCRETE PLACED AND FINISHED PER WSDOT STD SPEC 8-14.3(3) OUTLET. FINAL RESTORATION SS SS- SSr-SS I I SS -SS- I I SS SS j I /WORK I�WW W �`_\ Wyi3p f..; X / /r \�/ / _ - da - a. - d CRUSHED SURFACING REQUIREMENTSTOBE DETERMINED BY CITY ENGINEERING INSPECTOR. V1 - 3 ZONE FOR I I 1 �(G CVO WATER LINE WORK I II I L _J G� / I / G / IN ROW 3) MH.I I I I I I T-SS-SS-SS-SS I ORKZONE IFSIDE SEW ER WORK S SS- �- I ROW (TRAFFIC CONTROLSIGNA E I I / F / FOUND IRO 3 PIPE _ i. Po poo poo 000 O O O O Oo Oo Oo Oo BASE COURSE PER WSDOT STD SPEC 9A3.9(3) A STRUCTURE MAV BE / I I I ( UP I2TH AVE N TO PUGET DR) / m 0.12F & O37'S OF 0 00 00 0 REQUIRED �_ APPROX TO OF GAS PER CITY RECORDS c I I j I .I I -� N 88'36'18" W 589.36'-fir'-�� �+ \ \ `s IFI�LANIj I 3 5 SIM / / ( I I r C3. C3. f F _=G��G_G�-G�r, - G c� PROP COR SSMH RIM=2a5.04'IIIIIIIIIIII IE e"CONC(N./�.) 3 IIIIIIIIIIIIIII-III NATIVE BACKFILL COMPACTED T095%MAXIMUM DENSITY PER WSDOT SECTION 2-03 '4 4\ \ F -239 64'(C.C.) I I I I I I 3 - SD SDSDSDSDSD \ \ DSD SD SD ---PD--',,SD� W' W W� GRADING AND DRAINAGE PLAN CONCRETE PAVEMENT SECTION 1 130' © $ SCALE: 1" ----..------__----._..__-- 10 0 5 10 20 1. SOILS REPORTS REPORT NUMBER: 190294EO01 (GEOTECHNICAL ENGINEERING REPORT) PREPARED BY: ASSOCIATED EARTH SCIENCES DATED: OCTOBER 15, 2019 2. ALL DISTURBED AREAS ON AND OFF -SITE SHALL BE COMPOST -AMENDED PER THE REQUIREMENTS OF BMPT5.13 IN THE STORMWATER MANUAL VOLUME V, CHAPTER 5. 3. VEGETATION AFFECTED BY 12" PIPE FROM DETENTION SYSTEM SHALL BE RESTORED TO ORIGINAL CONDITION TO THE MAXIMUM EXTENTS PRACTICABLE. 4. A MINIMUM OF 3' HORIZONTAL SEPARATION AND V VERTICAL SEPARATION IS REQUIRED BETWEEN DRY UTILITIES (POWER, GAS, PHONE, CABLE, ETC) AND SEWER, WATER GRADING QUANTITIES PAVING LEGEND AND STORM, AND A MINIMUM OF 5' HORIZONTAL SEPARATION AND V VERTICAL SEPARATION FROM ANY CITY OWNED LINES. TOTAL EXCAVATION (CUT)- 30 CU YES TOTAL NEW ASPHALT S. ATVPE II CATCH BASIN IS REQUIRED WHENEVER RIM TO INVERT EXCEEDS S'. EMBANKM ENT(FILL)- 160 CU VDS® OVERLAY EXISTING ASPHALT/UTILTTV SAWCUT TOTAL 190 CU YES 6. A M IN IMUM OF TOF COVER IS REQUIRED FOR ALL PIPES LOCATED UNDER DRIVEABLE SURFACES AND I'OF COVER UNDER LANDSCAPE SURFACES. THEQUANTITIES SHOWN ABOVE ARE FOR THE PERMIT PROCESS NEWCONCRETE ONLY. THESE VALUES ARE APPROXIMATE. DO NOT USE FOR BIDDING, PAYMENT, OR ESTIMATING PURPOSES. APPROVED FOR CONSTRUCTION CITY OF EDMONDS DATE: BY; CITY ENONFEFING DIVISION W LLI U Q Z LLI Q 0 � J w >- 0 Q o' O rn W Z o Z Z Q Q < J Z Li vi Q U Z Z O m w p D:f J U Li 0 C SHEET C3.1 Crouch-Maupin Residence - CG #20008.20 Drainage Report June 2, 2020 Section VII, Page 5 SAMPLE ACTIVITY LOG DATE FACILITY MAINTENANCE PERFORMED RESULTS/ NOTES C 4M 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com 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. ai ena e �Deeyct on do he ai na a is R ults xpe ed en C po nts N de aint an is P rfor ed Ge ral Vi t i lug ' g e Tra or /eo B rier ear e to d ign w t n 2 o of ing n th arri apa y. M I ama d/ ent t of ape ore an Khac ith be s m e Mis ' g /�Baare B s. ars a miing enti bar ' r Ba�inpl a ordi to ign. mis ng. ars a to e a rus ca ing % Ba err ace �ra�i�o/de rior ' n t ny rt of arrie . sign an ds Ou t x1p eb ' bar ' r m' �nno tac d to XBi r f Xyah �to' e pi Volume V — Runoff Treatment BMPs — December 2014 4-39 No. 18 — Catchbasin Inserts Maintenance Defect Conditions When Maintenance is Results Expected When Component Needed Maintenance is Performed General Sediment When sediment forms a cap over the No sediment cap on the insert Accumulation insert media of the insert and/or unit. media and its unit. Trash and Trash and debris accumulates on insert Trash and debris removed Debris unit creating a blockage/restriction. from insert unit. Runoff freely Accumulation flows into catch basin. Media Insert Not Effluent water from media insert has a Effluent water from media Removing Oil visible sheen. insert is free of oils and has no visible sheen. Media Insert Catch basin insert is saturated with water Remove and replace media Water Saturated and no longer has the capacity to insert absorb. Media Insert -Oil Media oil saturated due to petroleum spill Remove and replace media Saturated that drains into catch basin. insert. Media Insert Use Media has been used beyond the typical Remove and replace media at Beyond Normal average life of media insert product. regular intervals, depending on Product Life insert product. Volume V — Runoff Treatment BMPs — December 2014 4-51 S406 BMPs for:Streets/ ig a pp ' ab B s: •. S ct a ant' ice tha au th eas adv se vir m al in t. ply nl s n de si m' in q tit' s. he pr tic e ro w de' rs c s c ciu ma es' in ac ate of siu ac te, si filar at als at aus es s dv e nv n to in t t a a, a s iu hl de. ` or nd ans r d nd nti in at ials n a im rvi s co ai en ad* ac rd ce th P for e o r s er Ou de S id w ater' is -P odu s o Fi he ro cts i is olu e. • S ep/ ea p cu at de d ti-i ng ate is d it from oad as on po ibl fte he ad rf e cl rs. ec d A iti al P I ens' r dw cl nin in rly rin to p o pa cu es fro ro su cc . nclu e 4 its..on to... is m talc. n th sp.. ifica ion for: e/a i-ice s. .• S407 BMPs for Dust Control at Disturbed Land Areas and Unpaved Roadways and Parking Lots Description of Pollutant Sources: Dust can cause air and water pollution problems particularly at demolition sites and in and areas where reduced rainfall exposes soil particles to transport by air. Pollutant Control Approach: Minimize dust generation and apply environmentally friendly and government approved dust suppressant chemicals, if necessary. Applicable Operational BMPs: • Sprinkle or wet down soil or dust with water as long as it does not result in a wastewater discharge. • Use only local and/or state government approved dust suppressant chemicals such as those listed in Ecology Publication #96-433, Techniques for Dust Prevention and Suppression. • Avoid excessive and repeated applications of dust suppressant chemicals. Time the application of dust suppressants to avoid or minimize their wash -off by rainfall or human activity such as irrigation. • Apply stormwater containment to prevent the conveyance of sediment into storm drains or receiving waters. Volume IV - Source Control BMPs — December 2014 2-15 Ecology prohibits the use of motor oil for dust control. Take care when using lignin derivatives and other high BOD chemicals in areas susceptible to contaminating surface water or ground water. Consult with Ecology and the local permitting authority on discharge permit requirements if the dust suppression process results in a wastewater discharge to the ground, ground water, storm drain, or surface water. Recommended Additional Operational BMPs for Roadways and Other Trafficked Areas: • Consider limiting use of off -road recreational vehicles on dust generating land. • Consider graveling or paving unpaved permanent roads and other trafficked areas at municipal, commercial, and industrial areas. • Consider paving or stabilizing shoulders of paved roads with gravel, vegetation, or local government approved chemicals. • Encourage use of alternate paved routes, if available. • Vacuum sweep fine dirt and skid control materials from paved roads soon after winter weather ends or when needed. • Consider using pre -washed traction sand to reduce dust emissions. Additional Recommended Operational BMPs for Dust Generating Areas: • Prepare a dust control plan. Helpful references include: Control of Open Fugitive Dust Sources (EPA-450/3-88-088), and Fugitive Dust Background Document and Technical Information Document for Best Available Control Measures (EPA-450/2-92-004). • Limit exposure of soil (dust source) as much as feasible. • Stabilize dust -generating soil by growing and maintaining vegetation, mulching, topsoiling, and/or applying stone, sand, or gravel. • Apply windbreaks in the soil such as trees, board fences, tarp curtains, bales of hay, etc. S408 BMPs fior:Du Co ro at an ac ri Ar as es pt' o of to o ces• nd tri ma ial an ng tiv' es c ge rat co der le o s o dus a 's t cal re ove usi xh st ste s. in ce nt d c cr pr uc an an in d ed ate ' s n a g era du . P icu e ter' s t t c ca e ai of io 'ncl e in st, w st, al, av , c e oc in , a bo' er as . Ai mi ion can ont in e s ter he ob' cti of is P ' to du th to wa r p uta s c se y st ene do an on 1. Volume IV - Source Control BMPs — December 2014 2-16 pp ' ab O of nal M • El' in u e to as at di ar s t se er, ou at , or rfa w er. onv u e to isc rg to an ry we f a we y e to se er tho y, to e pp e ea en Ob in ro iat tat nd oca e s th e d' cha es. e en d dit' nal pe do P . At in erc' an du 1 cil' 'es, nd t a ry ast at is ar co ec ' ns to o s a to Lirf e w e fol ws- • on ct iel su y u' in , pa cu y der it gs o er i us 1 as to to rai fr b ' di a p: axed sur ces of h e t e j 'n t pu is s rm rai ). • ur' g n -st r nd' on 'ns p t e s rm al or n- / s ter isc r e Re rd e 1 ati s o 11 n-s rm ater is ar . I 11 ed 'sch ge :'• us 1, e e a ap ar S w th a he o I o atio of o ew s, s it se ers nd ed d np i d ch es er' p os ay us 1. e re rds s ch i g s e ics o f ti n s' e s er on do an o th o e ap. on ' er n in e, e, o the ica s t s t et co ec ons etw o c ve nc ys s p ces a a sto w er). de b, c duc V sp do of e s rm rai an ec t ge v' eot e. in re e o se d 1 ati s o co ect' ns th e ' o do o e ap d r is e ap co in N e s e co ecti ns at e i on ten it e eld ry • enta co ect' ns st er or su ace a an tak th cti s s cif d a ve s a is e Ps S411 BMPs for Landscaping and Lawn/ Vegetation Management Description of Pollutant Sources: Landscaping can include grading, soil transfer, vegetation removal, pesticide and fertilizer applications, and watering. Stormwater contaminants include toxic organic compounds, heavy metals, oils, total suspended solids, coliform bacteria, fertilizers, and pesticides. Lawn and vegetation management can include control of objectionable weeds, insects, mold, bacteria, and other pests with pesticides. Examples include weed control on golf course lawns, access roads, and utility corridors and during landscaping; sap stain and insect control on lumber and logs; rooftop moss removal; killing nuisance rodents; fungicide application to patio decks, and residential lawn/plant care. It is possible to Volume IV - Source Control BMPs — December 2014 2-21 release toxic pesticides such as pentachlorophenol, carbamates, and organometallics to the environment by leaching and dripping from treated parts, container leaks, product misuse, and outside storage of pesticide contaminated materials and equipment. Poor management of the vegetation and poor application of pesticides or fertilizers can cause appreciable stormwater contamination. Pollutant Control Approach: Control of fertilizer and pesticide applications, soil erosion, and site debris to prevent contamination of stormwater. Develop and implement an Integrated Pest Management Plan (IPM) and use pesticides only as a last resort. Carefully apply pesticides/ herbicides, in accordance with label instructions. Maintain appropriate vegetation, with proper fertilizer application where practicable, to control erosion and the discharge of stormwater pollutants. Where practicable grow plant species appropriate for the site, or adjust the soil properties of the subject site to grow desired plant species. Applicable Operational BMPs for Landscaping: • Install engineered soil/landscape systems to improve the infiltration and regulation of stormwater in landscaped areas. Do not dispose of collected vegetation into waterways or storm sewer systems. Recommended Additional Operational BMPs for Landscaping: • Conduct mulch -mowing whenever practicable • Dispose of grass clippings, leaves, sticks, or other collected vegetation, by composting, if feasible. • Use mulch or other erosion control measures on soils exposed for more than one week during the dry season or two days during the rainy season. • Store and maintain appropriate oil and chemical spill cleanup materials in readily accessible locations when using oil or other chemicals. Ensure that employees are familiar with proper spill cleanup procedures. • Till fertilizers into the soil rather than dumping or broadcasting onto the surface. Determine the proper fertilizer application rate for the types of soil and vegetation encountered. • Till a topsoil mix or composted organic material into the soil to create a well -mixed transition layer that encourages deeper root systems and drought -resistant plants. • Use manual and/or mechanical methods of vegetation removal rather than applying herbicides, where practical. Volume IV - Source Control BMPs — December 2014 2-22 Applicable Operational BMPs for the Use of Pesticides: • Develop and implement an IPM (See section on IPM in ,4pplicable e Operational BMPs for Vegetation Manyg ment) and use pesticides only as a last resort. • Implement a pesticide -use plan and include at a minimum: a list of selected pesticides and their specific uses; brands, formulations, application methods and quantities to be used; equipment use and maintenance procedures; safety, storage, and disposal methods; and monitoring, record keeping, and public notice procedures. All procedures shall conform to the requirements of Chapter 17.21 RCW and Chapter 16-228 WAC (Appendix IV-D R.7). • Choose the least toxic pesticide available that is capable of reducing the infestation to acceptable levels. The pesticide should readily degrade in the environment and/or have properties that strongly bind it to the soil. Conduct any pest control activity at the life stage when the pest is most vulnerable. For example, if it is necessary to use a Bacillus thuringiens application to control tent caterpillars, apply it to the material before the caterpillars cocoon or it will be ineffective. Any method used should be site -specific and not used wholesale over a wide area. • Apply the pesticide according to label directions. Do not apply pesticides in quantities that exceed manufacturer's instructions. • Mix the pesticides and clean the application equipment in an area where accidental spills will not enter surface or ground waters, and will not contaminate the soil. • Store pesticides in enclosed areas or in covered impervious containment. Do not discharge pesticide contaminated stormwater or spills/leaks of pesticides to storm sewers. Do not hose down the paved areas to a storm sewer or conveyance ditch. Store and maintain appropriate spill cleanup materials in a location known to all near the storage area. • Clean up any spilled pesticides. Keep pesticide contaminated waste materials in designated covered and contained areas. • The pesticide application equipment must be capable of immediate shutoff in the event of an emergency. • Spraying pesticides within 100 feet of open waters including wetlands, ponds, and rivers, streams, creeks, sloughs and any drainage ditch or channel that leads to open water may have additional regulatory requirements beyond just following the pesticide product label. Additional requirements may include: • Obtaining a discharge permit from Ecology. • Obtaining a permit from the local jurisdiction. • Using an aquatic labeled pesticide. Volume IV - Source Control BMPs — December 2014 2-23 obtain a publication entitled "Suspended, Canceled, and Restricted Pesticides " which lists all restricted pesticides and the specific uses that are allowed. Applicable Operational BMPs for Vegetation Management: Use at least an eight -inch "topsoil" layer with at least 8 percent organic matter to provide a sufficient vegetation -growing medium. Amending existing landscapes and turf systems by increasing the percent organic matter and depth of topsoil can substantially improve the permeability of the soil, the disease and drought resistance of the vegetation, and reduce fertilizer demand. This reduces the demand for fertilizers, herbicides, and pesticides. Organic matter is the least water-soluble form of nutrients that can be added to the soil. Composted organic matter generally releases only between 2 and 10 percent of its total nitrogen annually, and this release corresponds closely to the plant growth cycle. Return natural plant debris and mulch to the soil, to continue recycling nutrients indefinitely. Select the appropriate turfgrass mixture for the climate and soil type. Certain tall fescues and rye grasses resist insect attack because the symbiotic endophytic fungi found naturally in their tissues repel or kill common leaf and stem -eating lawn insects. However, they do not, repel root -feeding lawn pests such as Crane Fly larvae, and are toxic to ruminants such as cattle and sheep. The fungus causes no known adverse effects to the host plant or to humans. Endophytic grasses are commercially available; use them in areas such as parks or golf courses where grazing does not occur. Local agricultural or gardening resources such as Washington State University Extension office can offer advice on which types of grass are best suited to the area and soil type. • Use the following seeding and planting BMPs, or equivalent BMPs to obtain information on grass mixtures, temporary and permanent seeding procedures, maintenance of a recently planted area, and fertilizer application rates: Temporary and Permanent Seeding, Mulching, Plastic Covering, and Sodding as described in Volume II. Adjusting the soil properties of the subject site can assist in selection of desired plant species. For example, design a constructed wetland to resist the invasion of reed canary grass by layering specific strata of organic matters (e.g., composted forest product residuals) and creating a mildly acidic pH and carbon -rich soil medium. Consult a soil restoration specialist for site -specific conditions. • Aerate lawns regularly in areas of heavy use where the soil tends to become compacted. Conduct aeration while the grasses in the lawn are growing most vigorously. Remove layers of thatch greater than 3/4-inch deep. Volume IV - Source Control BMPs — December 2014 2-25 Mowing is a stress -creating activity for turfgrass. Grass decreases its productivity when mown too short and there is less growth of roots and rhizomes. The turf becomes less tolerant of environmental stresses, more disease prone and more reliant on outside means such as pesticides, fertilizers, and irrigation to remain healthy. Set the mowing height at the highest acceptable level and mow at times and intervals designed to minimize stress on the turf. Generally mowing only 1/3 of the grass blade height will prevent stressing the turf. Irrigation: The depth from which a plant normally extracts water depends on the rooting depth of the plant. Appropriately irrigated lawn grasses normally root in the top 6 to 12 inches of soil; lawns irrigated on a daily basis often root only in the top 1 inch of soil. Improper irrigation can encourage pest problems, leach nutrients, and make a lawn completely dependent on artificial watering. The amount of water applied depends on the normal rooting depth of the turfgrass species used, the available water holding capacity of the soil, and the efficiency of the irrigation system. Consult with the local water utility, Conservation District, or Cooperative Extension office to help determine optimum irrigation practices. Fertilizer Management: Turfgrass is most responsive to nitrogen fertilization, followed by potassium and phosphorus. Fertilization needs vary by site depending on plant, soil, and climatic conditions. Evaluation of soil nutrient levels through regular testing ensures the best possible efficiency and economy of fertilization. For details on soils testing, contact the local Conservation District, a soils testing professional, or a Washington State University Extension office. Apply fertilizers in amounts appropriate for the target vegetation and at the time of year that minimizes losses to surface and ground waters. Do not fertilize when the soil is dry. Alternatively, do not apply fertilizers within three days prior to predicted rainfall. The longer the period between fertilizer application and either rainfall or irrigation, the less fertilizer runoff occurs. Use slow release fertilizers such as methylene urea, IDBU, or resin coated fertilizers when appropriate, generally in the spring. Use of slow release fertilizers is especially important in areas with sandy or gravelly soils. Time the fertilizer application to periods of maximum plant uptake. Ecology generally recommends application in the fall and spring, although Washington State University turf specialists recommend four fertilizer applications per year. Volume IV - Source Control BMPs — December 2014 2-26 S417 BMPs for Maintenance of Stormwater Drainage and Treatment Systems Description of Pollutant Sources: Facilities include roadside catch basins on arterials and within residential areas, conveyance systems, detention facilities such as ponds and vaults, oil/water separators, biofilters, settling basins, infiltration systems, and all other types of stormwater treatment systems presented in Volume V. Oil and grease, hydrocarbons, debris, heavy metals, sediments and contaminated water are found in catch basins, oil and water separators, settling basins, etc. Pollutant Control Approach: Provide maintenance and cleaning of debris, sediments, and oil from stormwater collection, conveyance, and treatment systems to obtain proper operation. Applicable Operational BMPs: Maintain stormwater treatment facilities per the operations and maintenance (O&M) procedures presented in Section 4.6 of Volume V in addition to the following BMPs: • Inspect and clean treatment BMPs, conveyance systems, and catch basins as needed, and determine necessary O&M improvements. • Promptly repair any deterioration threatening the structural integrity of stormwater facilities. These include replacement of clean -out gates, catch basin lids, and rock in emergency spillways. • Ensure adequacy of storm sewer capacities and prevent heavy sediment discharges to the sewer system. • Regularly remove debris and sludge from BMPs used for peak -rate control, treatment, etc. and discharge to a sanitary sewer if approved by the sewer authority, or truck to an appropriate local or state government approved disposal site. • Clean catch basins when the depth of deposits reaches 60 percent of the sump depth as measured from the bottom of basin to the invert of the lowest pipe into or out of the basin. However, in no case should there be less than six inches clearance from the debris surface to the invert of the lowest pipe. Some catch basins (for example, WSDOT Type 1 L basins) may have as little as 12 inches sediment storage below the invert. These catch basins need frequent inspection and cleaning to prevent scouring. Where these catch basins are part of a stormwater collection and treatment system, the system Volume IV - Source Control BMPs — December 2014 2-37 owner/operator may choose to concentrate maintenance efforts on downstream control devices as part of a systems approach. • Clean woody debris in a catch basin as frequently as needed to ensure proper operation of the catchbasin. • Post warning signs; "Dump No Waste - Drains to Ground Water," "Streams," "Lakes," or emboss on or adjacent to all storm drain inlets where possible. • Disposal of sediments and liquids from the catch basins must comply with "Recommendations for Management of Street Wastes" described in Appendix IV-G of this volume. Additional Applicable BMPs: Select additional applicable BMPs from this chapter depending on the pollutant sources and activities conducted at the facility. Those BMPs include: • S425 BMPs for Soil Erosion and Sediment Control at Industrial Sites • S427 BMPs for Storage of Liquid, Food Waste, or Dangerous Waste • S406 BMPs for Spills of Oil and Hazardous Substances • S410 BMPs for Illicit Connections to Storm Drains • S430 BMPs for Urban Streets X41 B s r n c in Ac it' s- ut de: D6*crjwotio of llu nt our `s: an act ng oll mant 'urc •s e de tsi pr ess rea , sta a ssi s, a ar s ere anu ctu 'ng tiv' h tak pl e i e st d s' nif ant po d po to ma rial re in. of do Co ro pp pack' C er d c ita' ou de an c ng d p ve so w4t6 ruK o nd nt in on he fe ible pli le/ pe ati al P• • w p p ed rea eg rl as ede , to ev t c to at' o ate . +' er e a vit y mi in or ni zin he nt in on sto w r. p ca S ct al `urce Control s: cl e t actity ( e F re 2. If • ssibie, ericIose'thfna fac rin act ty ' a ui in ov th cti 'ty d c ne flo edrofis t a s ita se r, i ' a rov d b he ca ew au orit . B o slo th oo as ee d t pre nt ain e o pol to to tsi ar S. u .7 Volume IV - Source Control BMPs — December 2014 2-38