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APPROVED STM_BLD2021-0985+Drainage_Report+7.15.2021_4.41.25_PM+2303659BLD2021-0985 RECEIVED Jul 16 2021 CITY OF EDMONDS DEVELOPMENT S ERVICES DEPARTMENT civil &structural ENGINEERING engineering & planning DRAINAGE REPORT Keck Residence 15722 72nd Ave W Edmonds, WA 98026 COMPLIES WITH APPLICABLE CITY STORMWATER CODE 0710212021 250 4th Ave S Ste 200 CG Project No. 21125.20 Edmonds, WA 98020 Phone: (425) 778-8500 Fax: (425) 778-5536 RECEIVED Jul 16 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Table of Contents Section I — Project Overview Section II — Minimum Requirements Section III — Off -Site Analysis Section IV — Permanent Stormwater Control Plan Section V — Construction Stormwater Pollution Prevention Section VI — Special Reports and/or Studies Section VII — Other Permits Section VIII — Operation and Maintenance Manual 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Keck Residence — CG #21125.20 July 2, 2021 Drainage Report SectionRIEEZEIVED Jul 16 2021 CITY OF EDMONDS Section I — Project Overview DEVELDEPARTMOPMENTSERVICES ENT Section I Summary Overview Existing Condition Developed Condition Overview This drainage report has been written for a new single-family residence project, the Keck Residence, located at 15722 72nd Ave W in Edmonds, WA 98026 (TPN: 00513100002501). The parcel is Lot 3 of the Meadowview Estates short plat (AF# 201612095001) and is on an elongated parcel of 0.72 ac spanning east to west. The site is currently undeveloped and is vegetated with trees and thick undergrowth. The site is on a steep downslope from east to west, and an Earth Subsidence and Landslide Area occupies a portion of the west side of the site. In the developed condition, there will be a single-family residence with associated retaining walls, a driveway, wood decks, and concrete patios and walkways. New and replaced impervious surfaces including Right -of -Way (ROW) improvements total 7,263 sf and the area of land disturbance is 16,380 sf. The project must comply with ECDC 18.30 — Stormwater Management Code, the 2014 Stormwater Management Manual of Western Washington (DOE Manual), and the 2017 Edmonds Stormwater Addendum (Edmonds Stormwater Addendum). It is classified as a Category 2 project per ECDC 18.30 and must meet Minimum Requirements #1-9 because the amount of new plus replaced impervious surfaces total over 5,000 sf. This report is based on the steps recommended in Chapter 7 of the Edmonds Stormwater Addendum. Existing Condition The site is currently undeveloped and densely vegetated with mostly deciduous trees on the eastern half of the site. The western half is occupied by mostly large conifers and considered an Earth Subsidence and Landslide Area (ESLA) per the survey and Edmonds GIS Map. The eastern half is on a moderate/steep downslope of about 15%, and the western half slopes at about 75%. Per the geotechnical engineering report, site soils consist of loose to medium dense slightly silty, gravelly sand with organics, becoming medium dense to dense wet soils at four feet below grade. The site borders both a private road and 72nd Ave W east/northeast, existing single-family residences to the north and west, and an undeveloped parcel to the south. Utilities are available at the site from the short plat development, including stormwater. There is an existing trench drain located above the steep western slope to mitigate hazards from the ESLA. Please see Section III for the off -site analysis. Developed Condition 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Keck Residence — CG #21125.20 July 2, 2021 Drainage Report SectionRIEEZEIVED Jul 16 2021 A 2-story single family residence including a daylighted basement and attached garage is proposedDf&.' MFENDT SOERVICES DEPARTMENT the site. An associated driveway, walkways, decks, and patios will be included in the site development. Retaining walls will be constructed throughout the site. Utilities are available at the site from the short plat development, including stub outs for water, sewer, power, and stormwater. The project proposed to install a sewer pump system to reach the existing sewer. Stormwater travels downstream from the site through conveyance pipes within drainage easements until it enters the City's MS4 within 75t" PI W about 0.1 mi downstream. The site is within the Puget Sound Piped Watershed. See Section III for the off -site analysis. On -site stormwater BMPs were evaluated for a project that discharges directly to Puget Sound through the City's MS4. All dispersion and infiltration BMPs were found to be infeasible. See Section IV for infeasibility criteria. The developed parcel areas are as follows: Pervious Areas Undisturbed Vegetation: 14,936 sf (0.343 ac) New Landscaping: 9,117 sf (0.209 ac) Total: 24,053 sf (0.552 ac) Impervious Areas Roof: 4,861 sf (0.112 ac) Driveway: 1,318 sf (0.035 ac) ROW Driveway: 63 sf (0.001 ac) Patio/Walkways: 1,021 sf (0.023 ac) Total: 7,263 sf (0.166 ac) Total Lot: 31,316 sf (0.719 ac) 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Keck Residence — CG #21125.20 Drainage Report July 2, 2021 SectionRUEZEIVED I unds Gulch ISeth $1 M Tiffany Hansen Sales 9 a Y d � PROJECT SITE A `m 1SBth S1 sw w a k � 4 �dr Figure 1-1. Vicinity Map (Google Maps). Jul 16 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Keck Residence — CG #21125.20 Drainage Report July 2, 2021 SectionRUE €IVED Figure 1-2. Aerial Photograph (Google Maps). Jul 16 2021 CITY OF EDMONDS DEVELOPMENT SERVICES 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Keck Residence — CG #21125.20 July 2, 2021 Drainage Report Section RUEZEIVED Jul 16 2021 CITY OF EDMONDS Section II — Minimum Requirements DEVELDEPARTMOPMENTSERVICES ENT Section II Summary Narrative The project must comply with ECDC 18.30 — Stormwater Management Code, the 2014 Stormwater Management Manual of Western Washington (DOE Manual), and the 2017 Edmonds Stormwater Addendum (Stormwater Addendum). It is classified as a Category 2 project per ECDC 18.30 and must meet Minimum Requirements #1-9 because the amount of new plus replaced impervious surfaces total over 5,000 sf. 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 I of the DOE Manual 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 V and the civil drawings. Minimum Requirement #3: Source Control of Pollution: All known, available and reasonable source control BMPs are required for all projects approved by the city. All single-family residential projects shall, at a minimum, incorporate required BMPs from SWMMWW Volume IV, S411 — BMPs for Landscaping and Lawn/Vegetation Management. The Operation & Maintenance Manual found in Section VII addresses Lawn/Vegetation management. 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 III. A conveyance capacity calculation for the downstream system is included in Section IV. Minimum Requirement #5: On -Site Stormwater Management: The proposed project discharges directly to Puget Sound through the City's MS4. Per ECDC 18.30, it must implement BMP T5.13 Post - Construction Soil Quality and Depth and evaluate BMPs T5.10A Downspout Full Infiltration Systems, T5.1013 Downspout Dispersion Systems, T5.10C Perforated Stub -out Connections, T5.11 Concentrated Flow Dispersion, and T5.12 Sheet Flow Dispersion. On -Site Stormwater BMPs were found to be infeasible for all hard surfaces due to the steep slope. See Section IV. 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Keck Residence — CG #21125.20 July 2, 2021 Drainage Report Section RUEZEIVED Jul 16 2021 Minimum Requirement #6: Runoff Treatment: This requirement applies to the new plus replaced hit MEN° SOERVICES DEPARTMENT surfaces and the converted vegetation areas. The following require construction of stormwater treatment facilities: i.) Projects in which the total of pollution -generating hard surface (PGHS) is 5,000 square feet or more in a threshold discharge area of the project, or ii.) projects in which the total of pollution -generating pervious surfaces (PGPS) — not including permeable pavements is 0.75 acres or more in a threshold discharge area, and from which there will be a surface discharge in a natural or man-made conveyance system from the site. The project's total amount of PGHS is less than 5,000 square feet and the amount of PGPS is less than 0.75 ac. Runoff treatment is not required. Roof materials will be non -pollution generating. There is standing seam metal roof on the plans, but it will include baked on enamel to avoid polluting runoff. Minimum Requirement #7: Flow Control: This requirement applies to projects that discharge stormwater directly, or indirectly through a conveyance system, into a fresh waterbody. Flow control is not required for projects that discharge directly to, or indirectly through the City's MS4 to Puget Sound. The project is within the Puget Sound Piped Watershed and therefore is exempt from this requirement. Minimum Requirement #8: Wetlands Protection: This requirement applies only to projects whose stormwater discharges into a wetland, either directly or indirectly through a conveyance system. This project site's stormwater does not discharge into a wetland and does not require wetland protection. Minimum Requirement #9: Operation and Maintenance: An operation and maintenance manual that is consistent with the provisions in Volume I and Volume V of the SWMMWW is required for proposed Stormwater Treatment and Flow Control BMPs/facilities. The party (or parties) responsible for maintenance and operation shall be identified in the operation and maintenance manual. For private facilities approved by the City, a copy of the operation and maintenance manual shall be retained on - site or within reasonable access to the site and shall be transferred with the property to the new owner. For public facilities, a copy of the operation and maintenance manual shall be retained in the appropriate department. A log of maintenance activity that indicates what actions were taken shall be kept and be available for inspection. See Section V111. 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Keck Residence — CG #21125.20 Drainage Report July 2, 2021 section RECEIVED Does the pn3jeel result in 2,ODO Square Feet, or greater, oFnew plu% replaced hard %urfacc area? OR Docs the land disturbing activity total 7,000 square feet or greatcr? Yes No Minimum Requirements No. 1 through 5 apply Minimum Requirement N.D. 2 applies Nex�--ti— E)Dcs the projcct add 5,000 squara feet or morc of new plus replaced hard surfaces? OR Convert 0.75 acres or mole of Vegetation to lawn or landscaped areas? OR Convert 2.5 acres or more of native vegetation to pasture? Yes No No Yes FIs this a road related pmjcct? Doc% the project add 5,000 %quarc feet or NO more ofnew hard surfaces? Yes All Minimum Requirements apply to the new and replaced Yes Do new hard surfaccs add 50%or hard surfaces and converted more to the existing hard surfaces vegetation areas_ within the Project liTnits`' All Minimum Requirements ]Ke No additional apply to the new hard surfaces requirements. and convened vegetation areas. Figure II-1 Flow Chart for Determining Requirements for Redevelopment (Figure 3.1 of the Edmonds Stormwater Addendum) Jul 16 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Keck Residence — CG #21125.20 July 2, 2021 Drainage Report Section RECEIVED Jul 16 2021 Section III — Off -Site AnalysisY OF CITEPARTMONDS DEVELOPMENT ERVICES DEPARTMSENT Section III 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. Runoff from the site enters the City's MS4 within one -quarter mile and therefore must evaluate and document downstream conditions up to and including runoff entry into the City's MS4. 7 .O O 73, ° Lun 's GUIC — __0 Watersh II � i 155218 x 9 - it • �, i�.;_: �, uJ 7124 I� i 15604 PRIV 15• `115• E CO_ NVEYANCE PIPE, N 1 7.:c] 15712 MS4 CONNECTION 400' DOWNSTUAM "" 7114 15 I ,r li 15701 i 1570b` �i 15714 15124 PROJECT SITE 15722 r i 1' 15730 FD.1 d 7400 i i ,_2•I + Figure III-1 Study Area 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Keck Residence — CG #21125.20 Drainage Report July 2, 2021 Section RECEIVED Jul 16 2021 Task 2 — Review all available information on the study area DECITY VELO MFENDT SOERVICES DEPARTMENT Existing stormwater improvements were determined from the survey and the City GIS map. There is an existing stormwater stub -out on the lot that was built as part of the short plat. From the stub -out, stormwater is directed to a catch basin within the access and utility easement to the west and is routed in conveyance pipes within the storm drainage easement to the public storm main within 75th PI W about 400 feet downstream to the west. The public storm system downstream consists of 12" and 18" CMP conveyance pipes that eventually discharge stormwater to Puget Sound an additional 0.07 mi downstream. Critical areas were evaluated using the City GIS map and western half of the lot is classified as an ESLA. Task 3 — Field inspect the study area A site visit was done on the afternoon of March 17, 2021. The weather was mostly sunny with no rain in the previous few days. From evaluating the surrounding conditions, the site does not appear to take on any significant upstream flow. There are existing catch basins on 72nd Ave W and the private drive upstream of the site. The following figures show the existing downstream conditions of the site. Figure III-2. From the eastern edge of the site property facing west towards the site. 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Keck Residence — CG #21125.20 Drainage Report July 2, 2021 Section RECEIVED Jul 16 2021 EDMONDS NT SERVICES tTMENT Figure III-3. From the area of the proposed building footprint facing west towards the proposed storm connection stub. 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 roof runoff through roof drains to a catch basin west of the proposed house. The catch basin will then connect to the existing stormwater stub onsite. No on -site stormwater BMPs for hard surfaces were found to be feasible for the project (see Section IV). The existing stormwater system and cutoff drain appeared to be in good condition, and it is not anticipated that the project will create any issues if runoff from all disturbed areas is routed to the stormwater stub. See Section IV for a conveyance capacity calculation for the downstream system. 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Keck Residence — CG #21125.20 July 2, 2021 Drainage Report Section DECEIVED Jul 16 2021 CITY OF EDMONDS Section IV — Permanent Stormwater Control Plan DEVELDOPMENT EPARTMENRVICES Section IV Summary Narrative BMP Feasibility Review Conveyance Capacity Calculation WWHM2012 Additional Flow Calculation Narrative The project must meet Minimum Requirement #5: On -Site Stormwater Management. Per ECDC 18.30, projects that directly discharge to Puget Sound through the City's MS4 must implement BMP T5.13 Post - Construction Soil Quality and Depth and evaluate BMPs T5.10A Downspout Full Infiltration Systems, T5.1013 Downspout Dispersion Systems, T5.10C Perforated Stub -out Connections, T5.11 Concentrated Flow Dispersion, and T5.12 Sheet Flow Dispersion. Water quality treatment and flow control facilities are not required for this project (see Minimum Requirements #6 and #7 in Section II). Feasibility Review Per ECDC 18.30, projects that discharges directly to Puget Sound through the City's MS4 must implement BMP T5.13 Post -Construction Soil Quality and Depth and evaluate BMPs T5.10A Downspout Full Infiltration Systems, T5.1013 Downspout Dispersion Systems, T5.10C Perforated Stub -out Connections, T5.11 Concentrated Flow Dispersion, and T5.12 Sheet Flow Dispersion. 1. BMP T5.13 Post -Construction Soil Quality and Depth: Feasible. All new landscaping will meet the Post -Construction Soil Quality and Depth in accordance with BMP T5.13 of the DOE Manual. 2. BMP T5.10A Downspout Full Infiltration Systems: Infeasible. A full infiltration system is not feasible since the facility would have to be located on slopes steeper than 25%. 3. BMP T5.1013 Downspout Dispersion Systems: Infeasible. The vegetated flowpath may not be on or above slopes greater than 15%. 4. BMP T5.10C Perforated Stub -out Connections: Infeasible. The perforated portion of the pipe may not be placed on or above slopes greater than 20%. 5. BMP T5.11 Concentrated Flow Dispersion: Infeasible. The vegetated flowpath may not be on or above slopes greater than 20%. 6. T5.12 Sheet Flow Dispersions: Infeasible. The vegetated flowpath may not be on or above slopes greater than 20%. 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Keck Residence — CG #21125.20 Drainage Report July 2, 2021 Section IREECEIVED Jul 16 2021 CITY OF EDMONDS Conveyance Capacity Calculation DEVELOPMENT SERVICES DEPARTMENT The project will add more impervious surfaces than was previously approved in the original short plat engineering design for Meadowview Estates (PLN20140015). The short plat allocated 5,700 sf of impervious surfaces for the subject parcel (Lot 1 of the short plat) whereas this project will be adding 1,515 sf more of impervious surfaces. A capacity analysis is required per the City Engineer to determine that the downstream conveyance system can handle the runoff from the additional impervious surfaces. Assuming an additional 0.03 ac (1,515 sf) of impervious surfaces, the project will add 0.016 cfs more during the 50-year storm than from the original calculations from the short plat drainage report done by LDC dated March 12, 2014. See the WWHM2012 output below. The original short plat calculations used the Stormshed program to model the conveyance capacity in the downstream conveyance pipes. The hydraulic model included the areas from the short plat as well as from two offsite basins to determine the flows and capacity of the downstream pipes. Figure IV-1 is a downstream node layout (from page 4-5 of the original report). CB #0 is the point of connection from the private conveyance to the public MS4 and is located in 75th Place W. For the purposes of this calculation, only the pipes surrounding the project site and the outfall will be analyzed (Pipes EX #0-9). The original drainage report included a summary table of the downstream pipes on page 4-21 with the pipe sizes, flows through the pipes, and flow capacity. The table has been updated below in this report to reflect the impact of the additional impervious surfaces. The additional 0.016 cfs was added to each flow and the new ratio was calculated. The additional flow has a negligible effect on the capacity of the pipes (less than 1%). The most constrained pipe is EX #8 located near the outfall, which is at 51% capacity. 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Keck Residence — CG #21125.20 Drainage Report July 2, 2021 Section PRECEIVED Figure IV-1 Downstream Node Layout (LDC, 2014) C 4MM, ENGINEERING Jul 16 2021 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Keck Residence - CG #21125.20 Drainage Report July 2, 2021 Section RECEIVED Table IV-1 Downstream Conveyance Capacity Calculation Jul 16 2021 CITY OF EDMONDS DEVELOPMENT SERVICES Reach ID Area (ac) Previous Flow (cfs) New Flow (cfs) Full Q (cfs) Previous Full Ratio New Full Ratio Size EX #7 2.02 0.4347 0.4502 27.2534 0.02 0.02 12" Diam EX #6 2.02 0.4347 0.4502 5.0521 0.09 0.09 12" Diam EX #5 2.02 0.4347 0.4502 12.731 0.03 0.04 12" Diam EX #4 2.02 0.4347 0.4502 25.2306 0.02 0.02 12" Diam EX #3 2.02 0.4347 0.4502 14.1324 0.03 0.03 12" Diam EX #2 2.02 0.4347 0.4502 23.8041 0.02 0.02 12" Diam EX #1 2.02 0.4347 0.4502 5.0521 0.09 0.09 12" Diam EX #0 14.6 3.8606 3.8761 19.0245 0.20 0.20 12" Diam EX #8 14.6 3.8606 3.8761 7.5952 0.51 0.51 18" Diam EX #9 14.6 3.8606 3.8761 33.307 0.12 0.12 18" Diam C CM ENGINEERING 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com WWHM2012 PROJECT REPORT Project Name: Keck Residence Site Name: Keck Residence Site Address: 15722 72nd Ave W City : Edmonds Report Date: 3/15/2021 MGS Regoin Puget East Data Start 1901/10/1 Data End : 2058/09/30 DOT Data Number: 03 Version Date: 2019/09/13 Version : 4.2.17 Low Flow Threshold for POC 1 : 50 Percent of the 2 Year High Flow Threshold for POC 1: 50 year PREDEVELOPED LAND USE Name : Basin 1 Bypass: No GroundWater: No Pervious Land Use acre A B, Forest, Mod .03 Pervious Total 0.03 Impervious Land Use acre Impervious Total 0 Basin Total 0.03 Element Flows To: Surface Interflow MITIGATED LAND USE Name : Basin 1 Bypass: No GroundWater: No Groundwater RECEIVED Jul 16 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Pervious Land Use acre Pervious Total 0 Impervious Land Use acre ROOF TOPS FLAT 0.03 Impervious Total 0.03 Basin Total 0.03 Element Flows To: Surface Interflow Groundwater ANALYSIS RESULTS Stream Protection Duration Predeveloped Landuse Totals for POC #1 Total Pervious Area:0.03 Total Impervious Area:O Mitigated Landuse Totals for POC #1 Total Pervious Area:O Total Impervious Area:0.03 Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.00012 5 year 0.000163 10 year 0.000187 25 year 0.000215 50 year 0.000233 100 year 0.00025 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.00746 5 year 0.009837 10 year 0.011542 25 year 0.013849 50 year 0.015683 100 year 0.017618 Perind and Impind Changes RECEIVED Jul 16 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT No changes have been made. RECEIVED Jul 16 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT This program and accompanying documentation are provided 'as -is' without warranty of any kind. The entire risk regarding the performance and results of this program is assumed by End User. Clear Creek Solutions Inc. and the governmental licensee or sublicensees disclaim all warranties, either expressed or implied, including but not limited to implied warranties of program and accompanying documentation. In no event shall Clear Creek Solutions Inc. be liable for any damages whatsoever (including without limitation to damages for loss of business profits, loss of business information, business interruption, and the like) arising out of the use of, or inability to use this program even if Clear Creek Solutions Inc. or their authorized representatives have been advised of the possibility of such damages. Software Copyright © by : Clear Creek Solutions, Inc. 2005-2021; All Rights Reserved. Keck Residence — CG #21125.20 July 2, 2021 Drainage Report Section ` UEZEIVED Jul 16 2021 �CFITY OF EDMONDS Section V — Construction Stormwater Pollution Preventio`DEPARTMENRVICES Section V Summary Narrative Erosion control details are provided consistent with the Edmonds Stormwater Addendum and the DOE Manual. 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). 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 building and associated parking area and walkways. 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 entrance to the site may be used as a stabilized construction entrance and expanded to the 15' minimum as necessary: Stabilized Construction Entrance (BMP C105) Element 3: Control Flow Rates The site is small enough that a silt fence used for Element 4 may be used to control flow rates. Element 4: Install Sediment Controls 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 will be installed along the west, north, and south edges of the site and 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: 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Keck Residence — CG #21125.20 Drainage Report Silt Fence (BMP C233) Wattles (BMP C235) Element 5: Stabilize Soils July 2, 2021 Section `RUEZEIVED Jul 16 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Leave existing ground cover undisturbed to the maximum extent feasible. Exposed and unworked soils shall be stabilized with the application of effective BMPs to prevent erosion throughout the life of the project. Soils must not remain exposed and unworked for more than the time periods set forth below to prevent erosion: • During the dry season (May 1— September 30): 7 days • During the wet season (October 1— April 30): 2 days 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) Topsoiling/Composting (BMP C125) Surface Roughening (BMP C130) Dust Control (BMP C140) Element 6: Protect Slopes The site is mapped as an Erosion Hazard Area by the City due to the steep slopes (30% average). Existing ground cover should be left undisturbed to the maximum extent feasible. Exposed slopes shall be stabilized with BMPs found in Element 5. The existing slope on the western half of the site will be protected from increased flow rates and sedimentation from the BMPs found in Element 4. Element 7: Protect Drain Inlets Drain inlets adjacent to the site and those made operable on -site will be protected from sedimentation. Stormwater shall not enter the conveyance system without first being filtered or treated to remove sediment. Inlet protection devices shall 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) 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Keck Residence — CG #21125.20 July 2, 2021 Drainage Report Section RIEEZEIVED Jul 16 2021 CITY OF EDMONDS Element 8: Stabilize Channels and Outlets DEVELOPMENT SERVICES DEPARTMENT Conveyance channels are not located on or in the immediate vicinity of the site. Element 9: Control Pollutants Design, install, implement, and maintain effective pollution prevention measures to minimize the discharge of pollutants. The suggested BMPs are: Concrete Handling (BMP C151) Sawcutting and Surfacing Pollution Prevention (BMP C152) Material Delivery, Storage and Containment (BMP C153) Element 10: Control Dewatering De -watering is not anticipated. Element 11: Maintain BMPs All temporary and permanent erosion and sediment control BMPs shall 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 consider 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 N/A — All infiltration and dispersion BMPs were found to be infeasible. 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Keck Residence — CG #21125.20 July 2, 2021 Drainage Report Section \RFECEIVED Jul 16 2021 Section VI — Special Reports and/or Studies CITY OFE DMONDS DEVELIMSENT DEVELOPMENT SERVICES DEPARTMENT Section VI Summary: Narrative The following reports are included in this section: 1. Geotechnical Engineering Study by Geotech Consultants, Inc, dated October 9, 2013. (Subdivision) 2. Geotechnical Engineering Study by Geotech Consultants, Inc, dated October 16, 2017. (Previous parcel owner) 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com ' RPM IYED �+ 13256 Northeast 20 ree , ut e 6 ■ Bellevue, Washidgtbd E02021 CONSULTANTS, INC. (425) 747-5618 FAX (425> 747,&Sfibs DEVELOPMENT SERVICES October 9, 2013 JN 13245 Meadowview Estates, LLC 12515 Willows Road Northeast, #20 Kirkland, Washington 98034 via email. kept@halvorsonconstruction.com Attention: E. Kent Halvorson Subject: Transmittal Letter-- Geotechnical Engineering Study Proposed Five -Lot Short Plat 15620 -- 72nd Avenue West Edmonds, Washington Dear Mr. Halvorson: We are pleased to present this geotechnical engineering report for the short -plat project in Edmonds, Washington. The scope of our services consisted of exploring site surface and subsurface conditions, and then developing this report to provide recommendations for general earthwork and criteria for foundations, retaining walls and building setbacks. This work was authorized by your acceptance of our proposal, P-8660, dated June 24, 2013. The attached report contains a discussion of the study and our recommendations. Please contact us if there are any questions regarding this report, or for further assistance during the design and construction phases of this project. Respectfully submitted, GEO CONSULTANTS, INC. D. Robert Ward, P.E. Principal cc: LDC, Inc. -- John Mirante via email to:jrnirante@ldccorp.com GEOTECH CONSULTANTS, INC. RECEIVED Jul 16 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT GEOTECHNICAL. ENGINEERING STUDY Proposed 5-Lot Short Plat 15620 -- 72nd Avenue West Edmonds, Washington This report presents the findings and recommendations of our geotechnical engineering study for the site of the proposed short -plat project to be located at in Edmonds. We were provided with a site plan that included topographic information. LDC Inc developed the plan, which is dated June 10, 2013. Based on this plan, we understand that the property will be short -platted into five lots. An existing residence that is located near the middle of the property will remain on one of the new lots. We understand that al! stormwater from impermeable surfaces (roofs, driveways) will be directed to a designated system and not toward the western portion of the site. If the scope of the project changes from what we have described above, we should be provided with revised plans in order to determine if modifications to the recommendations and conclusions of this report are warranted. SITE CONDITIONS SURFACE The Vicinity Map, Plate 1, illustrates the general location of the site in the northern portion of Edmonds. The generally square property has approximately 371 feet of frontage on its upslope, eastern side along 72nd Avenue West. The approximate central portion of the property is developed with an existing residence and detached garage. There is a main gravel driveway that extends mostly westward to the garage from the street. A gravel parking area extends off the south side of the driveway about 40 feet east of the western end of the driveway. Another driveway that is less developed is located on the southern portion of the property. It initially extends mostly westward from the street, but then extends northwesterly until is terminus near the southern side of the residence. Most of the property slopes downward to the west. With the exception of the western edge of the property, the inclination of the property is mostly in the range of 15 to 30 percent. Some small areas in the moderately sloped portion of the property have an inclination greater than 40 percent and a height of 10 feet, located around the gravel parking area and east of the residence/garage, it is very apparent that these areas were oversteepened from their original moderate inclinations because of manmade grading. There is a very steep slope that is on the western edge of the property and/or extends west of the property. This slope is approximately 80 to 100 feet tall. Gentle to moderate inclined, residential property is directly west of the very steep slope. In general, with the exception of the developed portions of the property, the site is forested. The southern portion of the majority, moderately -inclined property has a forest with some large trees and native underbrush. Fewer large trees and less native underbrush are generally located on the northern side of this moderately -inclined portion of the property. Some large trees are located near the top of the very steep slope, but mostly it is covered with more moderately -sized trees. An approximately 40-foot-wide, mostly 3- to 4-foot-deep landslide occurred on the very steep western slope on about January 1, 1997. The landslide followed a short period of extremely high GEOTECH CONSULTANTS, INC. RECEIVED Meadowview Estates, LLC job .IJ J 021 October 9, 2013 DEV TTERD CES DEPARTMENT precipitation and a very significant amount of landslides occurred on slopes in the Puget Sound. The landslide area was repaired by some grading at the top of the slope and installing a drainage system to handle surface and subsurface water in the area of the residence. The approximate location of the now -repaired landslide is shown on Plate 2. A Surface -mounted stormwater pipe now extends over the slope and through a neighboring property to the west to discharge this surface and subsurface water well west of the slope and subject property. In addition to the drainage improvements done on the subject property, a formal stormwater system has been constructed in the 72nd Avenue West since 1997. Apparently the water from this system also discharges water away from the steep western slope. We did not observe indications of recent instability of in the previous slide area and the steep western slope on and near the subject property. SUBSURFACE The subsurface conditions west/southwest of the existing residence were explored with three test borings in 1997 following the shallow landslide that occurred near the top of the steep western slope just west of the existing residence. To supplement this information, we recently explored the property by excavating seven test pits; the approximate locations of all the explorations are shown on the Site Exploration Plan, Plate 2. Our recent exploration program was based on the proposed construction, the past test borings, anticipated subsurface conditions and those encountered during exploration, and the scope of work outlined in our proposal. The seven test pits were excavated on July 3, 2013 with a trackhoe. A geotechnical engineer from our staff observed the excavation process and logged the test pits. The Test Pit Logs are attached to this report as Plates 3 through 6. The test borings were drilled on January 18, 1997 using a truck -mounted, hollow -stem auger drill. Samples were taken at 5-foot intervals with a standard penetration sampler. This split -spoon sampler, which has a 2-inch outside diameter, is driven into the soil with a 140-pound hammer falling 30 inches. The number of blows required to advance the sampler a given distance is an indication of the soil density or consistency. A geotechnical engineer from our staff observed the drilling process, logged the test borings, and obtained representative samples of the soil encountered. The Test Boring Logs are attached as Plates 7 through 9. Soil Conditions Test Borings 1 and 2, which were drilled near the top of the slope of the previous landslide area, encountered approximately 15 to 19 feet of dense to very dense, gravelly sand at the ground surface. This sand was underlain with stiff and dense, sandy silt and silty sand to the maximum explored depth of 31 feet. The third boring, drilled away from the slope, encountered dense sand near the ground surface. The sand was underlain by medium - dense to dense, silty sand to the maximum explored depth of 26 feet. We observed a lens of silt at about 20 feet below the crest of the slope in the landslide area. The test pits were excavated to a maximum explored depth of 7 feet. The soil revealed in the test pits was very similar to the upper soil in the test boring, consisting of sand with varying degrees of gravel and silt (mostly low silt content). Some boulders were revealed in the more gravelly sand. The upper, approximate 1 to 4 feet of the sand generally contained organics and was loose. The sand mostly became dense below these depths. GEOTECH CONSULTANTS, INC. Meadowview Estates, LLC October 9, 2013 RECEIVED JI�q3IA. J021 ONDS DEV EL ERVICES DEPARTMENT Per the "Soil Survey of Snohomish County Area Washington" (1978), the soil on the site is considered: 4-Alderwood-Everett gravelly sandy loam. We obtained the logs of some test borings drilled at slightly higher elevations just northwest of the property. Dense to very dense, gravelly silty sand was revealed in those test borings. We also obtained the logs of test borings drilled at elevations near or below the base of the steep western slope. Competent silty sand and silt were generally revealed at shallow depths in those test borings. Groundwater Conditions No groundwater seepage was encountered in the test pits, but some groundwater was observed in the borings at a depth of approximately 16 to 30 feet. The explorations were left open for only a short time period. Therefore, the seepage levels on the logs represent the location of transient water seepage and may not indicate the static groundwater level, Groundwater levels encountered during drilling can be deceptive, because seepage into the boring can be blocked or slowed by the auger itself. It should be noted that groundwater levels vary seasonally with rainfall and other factors. We believe that groundwater will only be found in during the normally wet winter and spring months. The stratification lines on the logs represent the approximate boundaries between soil types at the exploration locations. The actual transition between soil types may be gradual, and subsurface conditions can vary between exploration locations. The logs provide specific subsurface information only at the locations tested. Where a transition in soil type occurred between samples in the borings, the depth of the transition was interpreted. The relative densities and moisture descriptions indicated on the test pit and boring logs are interpretive descriptions based on the conditions observed during excavation and drilling. The compaction of backfili was not in the scope of our services. Loose soil will therefore be found in the area of the test pits. If this presents a problem, the backfill will need to be removed and replaced with structural fill during construction. LANDSLIDE INFORMATION FOR THE VICINITY OF THE SUBJECT SITE The City of Edmonds has mapped the western side of the subject property as being within an area known as the North Edmonds Earth Subsidence and Landslide Hazard Area (NEESLH). The large portion of the NEESLH is located downslope (west) and south of the property. A map of the area has been attached in the Appendix of this report. This area has been extensively studied, and multiple geotechnical reports have been published, with the most recent being the North Edmonds Earth Subsidence and Landslide Hazard Area Summary Report published by Landau Associates, dated March 14, 2007. This report describes the overall area as being a large historic/prehistoric landslide that includes a massive downset block of land. Large-scale landsliding of the area has been recorded as occurring in the 1940s and 1950s that reportedly destroyed approximately 6 homes and damaged many others. The historic Dames and Moore (1968) report indicates that the areas of large scale sliding occurred on the lower (western) portion of the overall slide mass to the north and south of the termination of North Meadowdale Drive. As such, the Landau report describes the zone just beneath the steep eastern slopes as being susceptible to the following risks: 1) reactivation of landslide debris (the slide complex) causing ground failure and movement, 2) encroaching landslide debris originating from shallow failures occurring upslope, and 3) GEOTECH CONSULTANTS, INC. ,1 RECEIVED Meadowview Estates, LLC jtggl3Nq021 October 9, 2013 DEVFL0&N9PSDERV CE8 DEPARTMENT landsliding occurring in ground that has not previously failed. The latter risk is the one that pertains to the subject site because the area upslope and east of the steep western slope definitely has not failed or had slope movement. The 2007 Landau report indicated that the subject site would be considered a "Zone D" area (see appendix). In 1979, Roger Lowe and Associates report for the overall area indicates that the subject site would have a varying probability of being affected by the various types of landsliding described above. A follow up report by GeoEngineers (1985) detailed the reduction slide probability associated with lowering of groundwater levels in the slide complex following installation of subsurface drainage facilities (LID circa 1984) in the eastern portion of the slide mass. Based on Figure 1 of the 1985 report, the western edge of the property (the steep slope) has a 2 percent probability of sliding (due to "debris slides") in a 25-year period. However, as we have noted above, several surface and subsurface drainage features have been added to the site and the adjacent street since 1997; these features reduces the probability of sliding. Therefore, we strongly believe that, based on the analysis done for the 1985 report, the probability of sliding in a 25-year period is no more than 1 percent. SLOPE STABILITY DISCUSSION AND ANALYSES As previously noted, mostly dense or denser sandy soils were revealed to the explored depth of the test borings. However, based on our experience and on Figure 1 of the 2007 Landau report, very stiff silt/clay soil very likely underlies the site. The depth of the sand and silt/clay interface is not exactly known, but again based on our experience and the Landau report; it is likely in the range of halfway down the steep western slope. We have made this assumption, and a slope/soil profile based on this assumption for the property is given in Plate 10. The soil parameters for both the sand and silt/clay soils are given on the profile. Also noted on the profile is the normal groundwater level, which would very likely be perched on the silt/clay. Using the existing slope configuration and appropriate soil parameters, stability analyses for both static and dynamic loading conditions were performed. For the dynamic analysis, a peak acceleration coefficient of 0.16g was used (this is based on a peak acceleration of 0.32g noted in a later section of this report). The analyses were done to determine where the easternmost edge of a landslide would occur having standard safety factors of at least 1.5 for static conditions, and 1.1 or 1.2 for dynamic conditions. The analyses indicated that a deep-seated slide for a static safety factor of 1.5 and a dynamic safety factor of 1.1 could occur as far as 50 feet from the top of the steep slope. An analysis having a dynamic safety factor of 1.2 revealed that a deep-seated slide could occur 65 feet from the top of the steep western slope. CONCLUSIONS AND RECOMMENDATIONS GENERAL THIS SECTION CONTAINS A SUMMARY OF OUR STUDY AND FINDINGS FOR THE PURPOSES OF A GENERAL OVERVIEW ONLY. MORE SPECIFIC RECOMMENDATIONS AND CONCLUSIONS ARE CONTAINED IN THE REMAINDER OF THIS REPORT. ANY PARTY RELYING ON THIS REPORT SHOULD READ THE ENTIRE DOCUMENT. The test pits and borings conducted for this study encountered dense to very dense, gravelly sand soils at depths of approximately 1 to 4 feet. The dense soil is very competent for supporting the building load, and thus conventional footings can be used for new residences and buildings. These soils also have high shear strength against slope instability. GEOTECH CONSULTANTS, INC. Meadowview Estates, LLC October 9, 2013 Conclusions and Recommendations Regarding Edmonds Code RECEIVED Jg4l3yQgWIID21 DEV O N�7ONDS SERVICES DEPARTMENT Based on The Edmonds Community Development Code (ECDC), Chapter 23.80 (Geologically Hazardous Areas), the steep western slope would be classified as a Landslide Hazard Area because it is steeper than 40 percent slope, and greater than 10 foot vertical relief. There are some other minor slopes on the property east of the western slope that are steeper than 10 feet, but they are obviously manmade as the entire area east of the western slope on and near the property has an average inclination of 15 to 30 percent. However, east of the western slope is considered an Erosion Hazard Area per Chapter 23.80. The ECDC suggests a minimum - development buffer equal to the height of the steep western slope, which is approximately 80 to 90 feet. Per the 2007 Landau report, the steep western slope and an area within about 80 to 90 feet of it are considered Zone D. The remainder of the property is Zone E. The Landau report recommends that a slope buffer be established using a rate of slope retreat or stable slope angle over a 125-year period. As noted earlier, we believe that, based on the analysis done for the 1985 GeoEngineers' report, the probability of a debris slide in a 25-year period is no more than 1 percent because of the numerous improvements in the control of surface water at the site in the last 15 years. We believe that the future control of surface water on the site once this development is in -place will readily maintain or possibly decrease this probability. Per Chapter 19.10.030H (6), an estimate of the retreat of the very steep western slope for a 125- and 25-year period is required. Based on the 1985 report analysis, and our experience on the site and in the Puget Sound region, we estimate that the very steep slope could retreat 3 to 4 feet in the next 125 years due to a debris (surface soil) slide (which is what essentially occurred on the site in 1997). We do not believe that any retreat will occur due to things such as freeze -thaw, wetting, etc because the slope is heavily vegetated. it is possible that a 3-to-4-foot deep debris slide could occur in the next 25 years in portions of the very steep slope, but an "average" movement of 3 to 4 feet is possible at any one area on the very steep slope in 125 years. The retreat of 3 to 4 feet of the slope due to a debris slide would very likely occur all in one episode, likely caused by heavy precipitation (as occurred in 1997). Based on ECDC 23.80.070.1, the buffer may be reduced when a qualified professional demonstrates that the reduction will adequately protect the proposed development, adjacent developments and uses, and the subject critical area. Based on our stability analyses, for a static and dynamic safety factor of 1.5 and 1.1, no slope movement would occur farther than 50 feet east of the top of the steep western slope. Therefore, it is our professional opinion that a buffer of 50 feet from the steep western slope is suitable for this project. We believe that this buffer is very suitable with regards to providing a stable slope angle for at least a 125-year period as required by the Landau report. A building setback of 15 feet is needed from the buffer, thus residences will be located no more than 65 feet from the slope. Based on our slope stability analysis, a dynamic safety factor of 1.2 was obtained 65 feet from the slope; thus, the 65-foot setback for residences from the steep western slope satisfies the design standards of ECDC 23.80.070.3. Therefore, in summary, we recommend a buffer of 50 feet be used for this project. Based on ECDC 23.80.060A, an alteration to a Landslide Hazard Area and associated buffer may occur for activities that, Will not increase the threat of the geologic hazard to adjacent properties beyond predevelopment conditions; Will not adversely affect other critical areas; GEOTECH CONSULTANTS, INC. RECEIVED Meadowview Estates, LLC Jkti 1§4W21 October 9, 2013 C NDS DEVET�ImE}rdi SERVICES DEPARTMENT 3. Are designed so that the hazard to the project is eliminated or mitigated to a level equal to or less that predevelopment conditions; and 4. Are certified as safe as designed and under anticipated conditions by a qualified engineer licensed in the State of Washington. In addition, ECDC 23,80.070A2 indicates that alterations of a Landslide Hazard Area and buffer may occur for activities for which a hazards analysis is submitted and certifies that: a) The development will not increase surface water discharge or sedimentation to adjacent properties beyond predevelopment conditions; b) The development will not decrease slope stability on adjacent properties; and c) Such alterations will not adversely impact other critical areas. Generally buffers are left undisturbed, but, as noted above, alterations can be made. We believe that altering the buffer so that disturbance can occur to itslaGt�at is suitable for this project provided grading will not involve adding more than 2 feet of fill in any one place and that no permanent sprinkler systems are installed. The 25 feet of the buffer closest to the steep western slope should be left as -is. Although it could be argued that some additional water that would otherwise be evapotranspirated by the native vegetation will reach the steep western slope, we believe that the amount of surface water that will be directed away from the slope and to a stormwater system will easily offset this additional water. We believe that the alteration is therefore suitable because: 1) it will not increase the potential for landslide to the adjacent, downslope properties, 2) it will not affect other critical areas, 3) the hazard is mitigated to be equal to predevelopment standards, 4) it is safe in our professional opinion, a) the alteration will not increase surface water discharge or sedimentation to adjacent properties, b) the alteration will not decrease slope stability, and c) the alteration will not adversely affect adjacent critical areas. The erosion control measures needed during the site development will depend heavily on the weather conditions that are encountered. While site clearing will expose a large area of bare soil, the erosion potential on the site is relatively low due to the gentle slope of the ground. We anticipate that a silt fence will be needed around the downslope sides of any cleared areas. Rocked construction access roads should be extended into the site to reduce the amount of soil or mud carried off the property by trucks and equipment. Wherever possible, these roads should follow the alignment of planned pavements, and trucks should not be allowed to drive off of the rock -covered areas. Cut slopes and soil stockpiles should be covered with plastic during wet weather. Following rough grading, it may be necessary to mulch or hydroseed bare areas that will not be immediately covered with landscaping or an impervious surface. The drainage and/or waterproofing recommendations presented in this report are intended only to prevent active seepage from flowing through concrete walls or slabs. Even in the absence of active seepage into and beneath structures, water vapor can migrate through walls, slabs, and floors from the surrounding soil, and can even be transmitted from slabs and foundation walls due to the concrete curing process. Water vapor also results from occupant uses, such as cooking and bathing. Excessive water vapor trapped within structures can result in a variety of undesirable conditions, including, but not limited to, moisture problems with flooring systems, excessively moist air within occupied areas, and the growth of molds, fungi, and other biological organisms that may be harmful to the health of the occupants. The designer or architect must consider the potential vapor sources and likely occupant uses, and provide sufficient ventilation, either passive or mechanical, to prevent a build up of excessive water vapor within the planned structure. GEOTECH CONSULTANTS, INC. �RECEIVED Meadowview Estates, LLC j�913&?121 October 9, 2013 DEONIES D R iNT Geotech Consultants, Inc. should be allowed to review the final development plans to verify that the recommendations presented in this report are adequately addressed in the design. Such a plan review would be additional work beyond the current scope of work for this study, and it may include revisions to our recommendations to accommodate site, development, and geotechnical constraints that become more evident during the review process. We recommend including this report, in its entirety, in the project contract documents. This report should also be provided to any future property owners so they will be aware of our findings and recommendations. SEISMIC CONSIDERATIONS In accordance with the International Building Code (IBC), the site soil profile within 100 feet of the ground surface is best represented by Site Class C (Very Dense Soil). The site soils have a low potential for seismic liquefaction because of their dense nature and the absence of near -surface groundwater. This statement regarding liquefaction includes the knowledge of the determined peak ground acceleration noted below. As noted in the USGS website, the mapped spectral acceleration value for a 0.2 second (SS) and 1.0 second period (Si) equals 1.2g and 0,4g, respectively. The International Building Code (IBC) states that a site -specific seismic study need not be performed provided that the peak ground acceleration be equal to Sps/2.5, where Scs is determined in ASCE 7. It is noted that Scs is equal to 2/3SMs• SMs equals Fa times Ss, where Fa is determined in Table 11.4-1. For our site, Fa = 1.0. Thus, the calculated peak ground acceleration that we utilized for the seismic -related parameters of this report equals 0.32g. CONVENTIONAL FOUNDATIONS The proposed structure can be supported on conventional continuous and spread footings bearing on undisturbed, medium -dense or denser, native sand soil, or on structural fill placed above this competent native soil. See the section entitled General Earthwork and Structural Fill for recommendations regarding the placement and compaction of structural fill beneath structures. Adequate compaction of structural fill should be verified with frequent density testing during fill placement. Prior to placing structural fill beneath foundations, the excavation should be observed by the geotechnical engineer to document that adequate bearing soils have been exposed. We recommend that continuous and individual spread footings have minimum widths of 12 and 16 inches, respectively. Exterior footings should also be bottomed at least 18 inches below the lowest adjacent finish ground surface for protection against frost and erosion. The local building codes should be reviewed to determine if different footing widths or embedment depths are required. Footing subgrades must be cleaned of loose or disturbed soil prior to pouring concrete. Depending upon site and equipment constraints, this may require removing the disturbed soil by hand. An allowable bearing pressure of 2,500 pounds per square foot (psf) is appropriate for footings supported on competent native soil and/or structural fill as noted above. A one-third increase in this design bearing pressure may be used when considering short-term wind or seismic loads. Lateral loads due to wind or seismic forces may be resisted by friction between the foundation and the bearing soil, or by passive earth pressure acting on the vertical, embedded portions of the foundation. For the latter condition, the foundation must be either poured directly against relatively GEOTECH CONSULTANTS, 1NC. RECEIVED Meaciowvi'ew Estates, LLC ,1ta OM:8021 >CCIOi]Er 9, 2013 DEVE�La=T8SERVSIC ES DEPARTMENT level, undisturbed soil or be, surrounded by level, well -compacted fill. We recommend using the following ultimate values for the foundation's resistance to lateral loading: ULTIMATE PARAMETER VALUE Coefficient of Friction 0.50 Passive Earth Pressure 300 pcf Where: (i) pcf is pounds per cubic foot, and (ii) passive earth pressure is computed using tt:e equivalent fluid density. If the ground in front of a foundation is loose or sloping, the passive earth pressure given above will not be appropriate. We recommend maintaining a safety factor of at least 1.5 for the foundation's resistance to lateral loading, when Using the above ultimate values. FOUNDATION AND RETAINING WALLS Retaining walls backfilled on only one side should be designed to resist the lateral earth pressures imposed by the soil they retain. The following recommended parameters are for walls that restrain backfill: Active Earth Pressure ' 35 pcf - backslope flatter than 3:1 (H.V) inclination Active Earth Pressure F 50 pcf -bac'cslope inclined between 2:1 and 3:1 (H:V) Passive Earth Pressure 300 pcf Coefficient of Friction 0.50 S=U�Light 135 pcf Where: (Ij pcf Is pounds per cubic foot, and (Pi) active. and passive earth presstires are computed using the equivalent fluid pressures. For a restrained wall that cannot deflect at least D.002 times its height, a uniform lateral pressure equal to 10 psf times the height & the wall shuuid be added to the above active equivalent fluid p rassu re, The design values given above do not include the effects of any hydrostatic pressures behind the walls and assume that no surcharges, suC> as those caused by slopes, vehicles, or adjacent foundations will be exerted on the walls. If these conditions exist, fhose pressures should be added to the above lateral soil pressures. Where sloping backfill is desired behind the walls, we will need to be given the wall dimensions and the slope of the backfill in order to provide the appropriate design earth pressures. The surcharge due to traffic loads behind a wail can typically be accounted for by adding a uniform pressure equal to 2 feet multiplied by the above active fluid density. heavy construction equipment should not be operated behind retaining and foundation walls ~within a distance equal to the height of a wall, unless the walls are designed for the additional lateral pressures resulting from the equipment. GEOTECH CONSULTANTS, 1NC. RECEIVED Meadowview Estates, LLC 0q413A�021 October 9, 2013 DE,pL4dE °RDCE8 DEPARTMENT The values given above are to be used to design only permanent foundation and retaining walls that are to be backfilled, such as conventional walls constructed of reinforced concrete or masonry. It is not appropriate to use the above earth pressures and soil unit weight to back -calculate soil strength parameters for design of other types of retaining walls, such as soldier pile, reinforced earth, modular or soil nail walls. We can assist with design of these types of walls, if desired. The passive pressure given is appropriate only for the depth of level, well -compacted fill placed in front of a retaining or foundation wall. The values for friction and passive resistance are ultimate values and do not include a safety factor. We recommend a safety factor of at least 1.5 for overturning and sliding, when using the above values to design the walls. Restrained wall soil parameters should be utilized for a distance of 1.5 times the wall height from corners or bends in the walls. This is intended to reduce the amount of cracking that can occur where a wall is restrained by a corner. Wall Pressures Due to Seismic Forces The surcharge wall loads that could be imposed by the design earthquake can be modeled by adding a uniform lateral pressure to the above -recommended active pressure. The recommended surcharge pressure is 8H pounds per square foot (psf), where H is the design retention height of the wall. Using this increased pressure, the safety factor against sliding and overturning can be reduced to 1.2 for the seismic analysis. Retaining Wall Backfill and Waterproofing Backfill placed behind retaining or foundation walls should be coarse, free -draining structural fill containing no organics. This backfill should contain no more than 5 percent silt or clay particles and have no gravel greater than 4 inches in diameter. The percentage of particles passing the No. 4 sieve should be between 25 and 70 percent. If the native sand is used as backfill, a minimum 12-inch width of free -draining gravel or a drainage composite similar to Miradrain 6000 should be placed against the backfilled retaining walls. The drainage composites should be hydraulically connected to the foundation drain system. The later section entitled Drainage Considerations should also be reviewed for recommendations related to subsurface drainage behind foundation and retaining walls. The purpose of these backfill requirements is to ensure that the design criteria for a retaining wall are not exceeded because of a build-up of hydrostatic pressure behind the wall. Also, subsurface drainage systems are not intended to handle large volumes of water from surface runoff. The top 12 to 18 inches of the backfill should consist of a compacted, relatively impermeable soil or topsoil, or the surface should be paved. The ground surface must also slope away from backfilled walls to reduce the potential for surface water to percolate into the backfill. Water percolating through pervious surfaces (pavers, gravel, permeable pavement, etc.) must also be prevented from flowing toward walls or into the backfill zone. The compacted subgrade below pervious surfaces and any associated drainage layer should therefore be sloped away. Alternatively, a membrane and subsurface collection system could be provided below a pervious surface. It is critical that the wall backfill be placed in lifts and be properly compacted, in order for the above -recommended design earth pressures to be appropriate, The wall design criteria assume that the backfill wilt be well -compacted in lifts no thicker than 12 inches. The compaction of backfill -near the walls should be accomplished with hand -operated equipment to prevent the walls from being overloaded by the higher soil forces that occur during compaction. The section entitled General Earthwork and Structural Fill contains GEOTECH CONSULTANTS, INC. MeadowviewEstates, LLC October 9, 2013 RECEIVED j031A8021 DOWEI TERDVIES DEPARTMENT additional recommendations regarding the placement and compaction of structural fill behind retaining and foundation walls, The above recommendations are not intended to waterproof below -grade walls, or to prevent the formation of mold, mildew or fungi in interior spaces. Over time, the performance of subsurface drainage systems can degrade, subsurface groundwater flow patterns can change, and utilities can break or develop leaks. Therefore, waterproofing should be provided where future seepage through the walls is not acceptable. This typically includes limiting cold -joints and wall penetrations, and using bentonite panels or membranes on the outside of the walls. There are a variety of different waterproofing materials and systems, which should be installed by an experienced contractor familiar with the anticipated construction and subsurface conditions. Applying a thin coat of asphalt emulsion to the outside face of a wall is not considered waterproofing, and will only help to reduce moisture generated from water vapor or capillary action from seeping through the concrete. As with any project, adequate ventilation of basement and crawl space areas is important to prevent a build up of water vapor that is commonly transmitted through concrete walls from the surrounding soil, even when seepage is not present. This is appropriate even when waterproofing is applied to the outside of foundation and retaining walls. We recommend that you contact an experienced envelope consultant if detailed recommendations or specifications related to waterproofing design, or minimizing the potential for infestations of mold and mildew are desired. The General, Slabs -On -Grade, and Drainage Considerations sections should be reviewed for additional recommendations related to the control of groundwater and excess water vapor for the anticipated construction. SLABS -ON -GRADS The building floors can be constructed as slabs -on -grade atop firm, non -organic native sand, or on structural fill. The subgrade soil must be in a firm, non -yielding condition at the time of slab construction or underslab fill placement. Any soft areas encountered should be excavated and replaced with select, imported structural fill. Even where the exposed soils appear dry, water vapor will tend to naturally migrate upward through the soil to the new constructed space above it. This can affect moisture -sensitive flooring, cause imperfections or damage to the slab, or simply allow excessive water vapor into the space above the slab. All interior slabs -on -grade should be underlain by a capillary break or drainage layer consisting of a minimum 4-inch thickness of gravel or crushed rock that has a fines content (percent passing the No. 200 sieve) of less than 3 percent and a sand content (percent passing the No. 4 sieve) of no more than 10 percent. This capillary break/drainage layer is not necessary if an underslab drainage system is installed. As noted by the American Concrete Institute (ACI) in the Guides for Concrete Floor and Slab Structures, proper moisture protection is desirable immediately below any on -grade slab that will be covered by tile, wood, carpet, impermeable floor coverings, or any moisture -sensitive equipment or products. ACI also notes that vapor retarders, such as 6-mil plastic sheeting, have been used in the past, but are now recommending a minimum 10-mil thickness. A vapor retarder is defined as a material with a permeance of less than 0.3 perms, as determined by ASTM E 96. It is possible that concrete admixtures may meet this specification, although the manufacturers of the admixtures should be consulted. Where vapor retarders are used under slabs, their edges should overlap by at least 6 inches and be sealed with adhesive tape. The sheeting should extend to the foundation walls for maximum vapor protection. If no potential for vapor passage through the slab is desired, a vapor barrier should be used. A vapor GEOTECH CONSULTANTS, INC. Meadowview Estates, LLC October 9, 2013 RECEIVED jt4413N!?021 DM141 SCERVICES DEPARTMENT barrier, as defined by ACi, is a product with a water transmission rate of 0.01 perms when tested in accordance with ASTM E 96, Reinforced membranes having sealed overlaps can meet this requirement. In the recent past, ACI (Section 4.1.5) recommended that a minimum of 4 inches of well -graded compactible granular material, such as a 5/8-inch-minus crushed rock pavement base, be placed over the vapor retarder or barrier for their protection, and as a "blotter" to aid in the curing of the concrete slab. Sand was not recommended by ACI for this purpose. However, the use of material over the vapor retarder is controversial as noted in current ACI literature because of the potential that the protection/blotter material can become wet between the time of its placement and the installation of the slab. If the material is wet prior to slab placement, which is always possible in the Puget Sound area, it could cause vapor transmission to occur up through the slab in the future, essentially destroying the purpose of the vapor barrier/retarder. Therefore, if there is a potential that the protection/blotter material will become wet before the slab is installed, ACI now recommends that no protection/blotter material be used. However, ACI then recommends that, because there is a potential for slab curl due to the loss of the blotter material, joint spacing in the slab be reduced, a low shrinkage concrete mixture be used, and 'other measures" (steel reinforcing, etc.) be used. ASTM E-1543-98 "Standard Practice for installation of Water Vapor Retarders Used in Contact with Earth or Granular Fill Under Concrete Slabs" generally agrees with the recent ACI literature. We recommend that the contractor, the project materials engineer, and the owner discuss these issues and review recent ACI literature and ASTM E-1643 for installation guidelines and guidance on the use of the protection/blotter material. The General, Permanent Foundation and Retaining Walls, and Drainage Considerations sections should be reviewed for additional recommendations related to the control of groundwater and excess water vapor for the anticipated construction. EXCAVATIONS AND SLOPE'S Excavation slopes should not exceed the limits specified in local, state, and national government safety regulations. Temporary cuts to a depth of about 4 feet may be attempted vertically in unsaturated soil, if there are no indications of slope instability. However, vertical cuts should not be made near property boundaries, or existing utilities and structures. Based upon Washington Administrative Code (WAC) 296, Part N, the soil at the subject site would generally be classified as Type B. Therefore, temporary cut slopes greater than 4 feet in height should not be excavated at an inclination steeper than 1:1 (Horizontal:Vertical), extending continuously between the top and the bottom of a cut. The above -recommended temporary slope inclination is based on the conditions exposed in our explorations, and on what has been successful at other sites with similar soil conditions. It is possible that variations in soil and groundwater conditions will require modifications to the inclination at which temporary slopes can stand. Temporary cuts are those that will remain unsupported for a relatively short duration to allow for the construction of foundations, retaining walls, or utilities. Temporary cut slopes should be protected with plastic sheeting during wet weather. It is also important that surface water be directed away from temporary slope cuts. The cut slopes should also be backfilled or retained as soon as possible to reduce the potential for instability, Please note that sand can cave suddenly and without warning. Excavation, foundation, and utility contractors should be made especially aware of this potential danger. These GEOTECH CONSULTANTS, ENC. r� RECEIVED Meadowvlew Estates, LLC jk�§4021 October 9, 2013 DEF'E,94ERD CE8 DEPARTMENT recommendations may need to be modified if the area near the potential cuts has been disturbed in the past by utility installation, or if settlement -sensitive utilities are located nearby. All permanent cuts into native soil should be inclined no steeper than 2:1 (H:V). Compacted fill slopes should also not be constructed with an inclination greater than 2:1 (H:V). To reduce the potential for shallow sloughing, fill must be compacted to the face of these slopes, This can be accomplished by overbuilding the compacted fill and then trimming it back to its final inclination. Adequate compaction of the slope face is important for long-term stability and is necessary to prevent excessive settlement of patios, slabs, foundations, or other improvements that may be placed near the edge of the slope. Water should not be allowed to flow uncontrolled over the top of any temporary or permanent slope. All permanently exposed slopes should be seeded with an appropriate species of vegetation to reduce erosion and improve the stability of the surficial layer of soil. Topsoil is often placed on regraded slopes to promote growth of vegetation. Proper preparation of the regraded surface, and use of appropriate topsoil is necessary to prevent the topsoil from sliding off the slope. This is most likely to occur following extended wet weather if a silty topsoil is used. On steeper slopes, it may be necessary to "track walk" the slope or cut small grooves across the slope prior to placing the topsoil. DRAINAGE CONSIDERATIONS Foundation drains should be used where (1) crawl spaces or basements will be below a structure, (2) a slab is below the outside grade, or (3) the outside grade does not slope downward from a building. Drains should also be placed at the base of all earth -retaining walls. These drains should be surrounded by at least 6 inches of 1-inch-minus, washed rock and then wrapped in non -woven, geotextile filter fabric (Mirafi 140N, Supac 4NP, or similar material). At its highest point, a perforated pipe invert should be at least 6 inches below the bottom of a slab floor or the level of a crawl space, and it should be sloped for drainage. All roof and surface water drains must be kept separate from the foundation drain system. A typical drain detail is attached to this report as Plate 11. For the best long-term performance, perforated PVC pipe is recommended for all subsurface drains. As a minimum, a vapor retarder, as defined in the Slabs -On -Grade section, should be provided in any crawl space area to limit the transmission of water vapor from the underlying soils. Also, an outlet drain is recommended for all crawl spaces to prevent a build up of any water that may bypass the footing drains. Some groundwater was observed in the 1997 test borings. if seepage is encountered in an excavation, it should be drained from the site by directing it through drainage ditches, perforated pipe, or French drains, or by pumping it from sumps interconnected by shallow connector trenches at the bottom of the excavation. The excavation and site should be graded so that surface water is directed off the site and away from the tops of slopes. Water should not be allowed to stand in any area where foundations, slabs, or pavements are to be constructed. Final site grading in areas adjacent to buildings should slope away at least 2 percent, except where the area is paved. Surface drains should be provided where necessary to prevent ponding of water behind foundation or retaining walls. Water from roof, storm water, and foundation drains should not be discharged onto the steep western slope; it should be tightlined to a suitable outfall located away from the western slope. GEOTECH CONSULTANTS, INC. A7eadowviewEstates, LLC October 9, 2013 GEiVERAL EARTHWORK AND STRUCTURAL. FILL. RECEIVED A413WO21 CITY OF ONDS D IBM SERVICES PARTMENT All building and pavement areas should be stripped of surface vegetation, topsoil, organic soil, and other deleterious material. The stripped or removed materials should not be mixed with any materials to be used as structural fill, but they could be used in non-structural areas, such as landscape beds. Structural fill is defined as any fill, including utility backfiii, placed under, or close to, a building, behind permanent retaining or foundation walls, or in other areas whore the underlying soil needs to support loads, All structural fill should be placed in horizontal lifts with a moisture content at, or near, the optimum moisture content. The optimum moisture content is that moisture content that results in the greatest compacted dry density. The moisture content of fill is very important and must be closely controlled during the filling and compaction process- i=ills placed on sloping ground should be keyed into the competent native sand soils. This is typically accomplished by placing and compacting the structural fill on level benches that are cut into the competent soils. The allowable thickness of the till lift will depend an the material type selected, the compaction equipment used, and the number of passes made to compact the lift. The loose lift thickness should not exceed 12 inches. We recommend testing the-5i1 as it is placed. If the fill is not sufficiently compacted, it can be recempacted before another lift Is placed. This eliminates the need to remove the fill to achieve the required compaction. The following table presents recommended relative compactions for structural fill: Beneath footings, slabs 98 or walkwa s Filled slopes and behind 90% reta 1 in 1 rl-q walls 95°%for upper 12 inches of Barteath pavements subgrade; 90°% below#hat level Where: Minimum Ralatfve Compaction is the ratio, expressed In percentages, of the compacted dry density to the maximum dry density, as determined in accordance with ASTM Test Designation 01557-01 (Modified Proctor). Use of On -Site Soil Debris or organic -laden onsite soils should not be used as structural fill. The on -site soil is somewhat silty and therefore somewhat moisture sensitive. Grading operations will be difficult during very wet weather, or when the moisture content of this sail well exceeds the optimum moisture content_ The moisture content of the silty, on -site sail must be at, or near, the optimum moisture content, as the soil cannot be consistently compacted to the required density when the moisture content is significantly greater than optimum. Moisture -sensitive soil may afro be susceptible to excessive softening and "pumping" from construction equipment, or even foot traffic, when the moisture content is greater than the optimum moisture content. It may be beneficial to protect subgrades with a layer of imparted sand or crushed rock to limit disturbance from traffic. GEOTECH CONSULTANTS, AG. Meadowview Estates, LLC October 9, 2013 RECEIVED JALu??021 DEe E -EEQQCERVICE3 DEPARTMENT Structural fill that will be placed in wet weather should consist of a coarse, granular soil with a silt or clay content of no more than 5 percent. The percentage of particles passing the No. 200 sieve should be measured from that portion of soil passing the three -quarter -inch sieve. LIMITATIONS The conclusions and recommendations contained in this report are based on site conditions as they existed at the time of our exploration and assume that the soil and groundwater conditions encountered in the test pits and test borings are representative of subsurface conditions on the site. If the subsurface conditions encountered during construction are significantly different from those observed in our explorations, we should be advised at once so that we can review these conditions and reconsider our recommendations where necessary. Unanticipated conditions are commonly encountered on construction sites and cannot be fully anticipated by merely taking samples in test pits and test borings. Subsurface conditions can also vary between exploration locations. Such unexpected conditions frequently require malting additional expenditures to attain a properly constructed project. it is recommended that the owner consider providing a contingency fund to accommodate such potential extra costs and risks. This is a standard recommendation for all projects. The recommendations presented in this report are directed toward the protection of only the proposed structure from damage due to slope movement. Predicting the future behavior of steep slopes and the potential effects of development on their stability is an inexact and imperfect science that is currently based mostly on the past behavior of slopes with similar characteristics. Landslides and soil movement can occur on steep scopes before, during, or after the development of property. However, the owner must ultimately accept the possibility that some slope movement could occur, resulting in possible loss of ground. However, we believe that the buffer determined in this report is suitable for at least 125 years. This report has been prepared for the exclusive use of E. Kent Halvorson and his representatives for specific application to this project and site. Our recommendations and conclusions are based on observed site materials and engineering analyses. Our conclusions and recommendations are professional opinions derived in accordance with current standards of practice within the scope of our services and within budget and time constraints. No warranty is expressed or implied. The scope of our services does not include services related to construction safety precautions, and our recommendations are not intended to direct the contractor's methods, techniques, sequences, or procedures, except as specifically described in our report for consideration in design. Our services also do not include assessing or minimizing the potential for biological hazards, such as mold, bacteria, mildew and fungi in either the existing or proposed site development. ADDITIONAL SERVICES in addition to reviewing the final plans, Geotech Consultants, Inc. should be retained to provide geotechnical consultation, testing, and observation services during construction. This is to confirm that subsurface conditions are consistent with those indicated by our exploration, to evaluate whether earthwork and foundation construction activities comply with the general intent of the recommendations presented in this report, and to provide suggestions for design changes in the event subsurface conditions differ from those anticipated prior to the start of construction. However, our work would not include the supervision or direction of the actual work of the GEOTECH CONSULTANTS, INC. x RECEIVED MeadowviawEstates, LC jdg3&J121 October 9, 2013 DAVON.DS -M; contractor and its employees or agents. Also, job and site safety, and dimensional measurements, will be the responsibility of the contractor. During the construction phase, we will provide geoteohnIcal observation and testing services when requested by you or your representatives. Please be aware that we can only document site work we actually observe. It is still the responsibility of your contractor or on -site construction team to verify that our recommendations are being followed, whether we are present at the site or not, The following plates are attached to complete this report: Plate t Vicinity Map Plate 2 Site Exploration Plan Plates 3 - 6 Test Pit Logs Plates T — 9 Test Boring Logs Plate 10 Site Cross -Section Plate I Typical Footing Drain Detail Appendix We appreciate the opportunity to be of service on this project. If you have any questlons, or if we may be of further service, please do not hesitate to contact us, TAJ/DRW; jyb Respectfully submitted, GEOTECH CONSULTANTS, INC, rn A. Johnson Senior Geologist D. Robert Ward, P.E. 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Edmonds, WashIngtvn /`/ Job H,, sQg P1a1 13M 2013 fJa Scele o 2 m IT7 D3o m Azm O mm0, zmZ CD O ~�O j �y m v IVEI �� Q1 �!y Jul 16 2021 �G�. ! T PIT I DEVE O MFEDMONDS TESEN SERVICES y DEPARTMENT Description FILL Topsail over; Brown, mottled, silty SEINE] with gravel and some organics, very dense, lease to medium dense becomes cemented, no organics, medium dense to dense Y SIM -` . 5 � if -[,ecomes gray, no gravel, more silty, wet * Teat Pit terminated at 7.0 feet on July 3, 2013. * Slight groundwater seepage was observed at 5.0 feet during excavation. * No saving observed during excavation. 10 a 90 o cR TEST PIT 2 over, Description crown, sirgnny spry, grsV911y -jANU Wn organics, sllgrivy moist, loose -becomes mostly gray, r.o organics, less silty, moist, dense lest Pit terminated at 6.0 feet on .July 3, 2013. * No groundwater was observed during excavation. * No caving observed during excavation. GEOTECH COINSULTAYrS, LAIC. TEST PIT LOG 15620 72nd Avenue West Edmonds, Washington Job Late; jLoggedb �+; P!a#e: 13245 July 2013 DRIN I 3 TEST PIT 3 :0 G Description RE= e 90 W 10 Jul 16 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT aI VYVI I, a11911uy .TREY, ylCWtNly Q7'%NU VYILR UFgdf11G5, 511UH11Y RIBS, [005e is meaiurn Qerlse -becomes dense, no organics -becomes gray, mottled, very moist to wet, medium dense to dense * Test Fit terminated at 6.0 feet on July 3, 2013. * No groundwater seepage was observed during excavation. * No caving observed during excavation, TEST PIT 4 ..I '0c. Description FILL Topsail over; Brown, slightly silty, gravelly SAND with organics, slightly n SI' -becomes mostly gray, r:o organics, less silt moist, dense 'I -qM y g �` 9 Y. Test Pit terminated at 6.0 feet on July 3, 2013. * No groundwater was observed during excavation. No caving observed during excavation. GIEOTECH CO SULTANTS, LN C. TEST PIT LOG 15620 72nd Avenue Vilest Edmonds, Washington ,fob Date: Logged by. 17;,-.,,e: 13245 July 2013 DR'A' 11111111 5 10 5 10 TEST PIT v Jul FE 2021 CITY OF DMONDS DEVELOPMENT SERVICES DEPARTMENT EPARTMENT Topsoil over, Brown, slightly silty, gravelly SAND, few organics, loose to moist -becomes mostly gray, no organics. moist, dense * Test Pit terminated at 4.0 feet on July 3, 2013. * No groundwater seepage was observed during excavation. * No caving observed during excavation. A CD TEST PIT 6 Description Gray, very gravelly SAND, coarse grained, medium dense -becomes dense * Test Pit terminated at 3.0 feet on July 3, 2013. * No groundwater seepage was observed during excavation. * No caving observed during excavation. GEOTECH CONSULTANTTS, INC. TEST PIT LOG 15520 72nd Avenue West Edmonds, Washington ,lob Dafe� Loggedby: Prate: 13245 July 2013 DR W 5 5 10 R-- TEST PIT 7 Description Topsoil over, Brawn, slightly silty, gravelly SAND with organics, loose to medium dense :SP litii SM 3 -becomes dense more gray, no organics * Test Pit terminated at 4.0 feet on July 3, 2013. * No groundwater seepage was observed during excavation. * No caving observed during excavation. GEOTECH GQNSV-L'rAN'S, Di c. Jul 16 2021 CITY OF EDMONDS DEVELOPMENT SERVICE: DEPARTMENT TEST PIT L G G 15520 72nd Avenue Vilest Edmonds, Washington Job Date. Logged by. F!a te: 13245 July 2013 TRW 6 RECEIVED Jul 16 2021 ---Z1TYVF -EDMON --MMARTMEN 0 �JF.n 7� Brown; giavelty SAND uridi soma silt, coarse,-gralnQ, mcdst, - very dense 51 IQ becomes less gravefly 36 211 74 becomes wet 2Q 26 33 Brown, slightly sandy and silty SAND, low plasticity, wet, stiff Mostly very fine grained, salty SAND .��' Moj�t' dense CTMY, saty S Test boring was tanTinated at feet below grade on 1-18-97 No g-r-oundwater seepage was encountered during drilling. GROTECH-' CONALTANTS, M. TEST BORING LOG rzOMOND8, Wk, d by.- 147tf,' ib N'W 'T IJL 13245 DA tdeA! M 1-07' 1 . 7W 7 RECEIVED Jul 16 2021 lot BORING2 8.gVEOOMFEEPTMSQ F1 SCES 'CEPARrMEN A, is To it Brown/mottied, silty SAND with grave�t,,. �t, 1pokojo mediumdense35 -Brown/mttled, gravelly SAND'wlth'sdmesllt; ymynaoisi,- dense- ao 33 35 40 I 4. Tan, very silty SA_�M, Lenses of silt, fine-grained, very wet, med ium -dense becomes very moist, darw SM -becomes wet, lens of silt X becomes satunted Test bolting was terminated at 31.5 feet below Zmda on 1-18-917. Groundwater seepage was encountemd. at 16' and 3 0' during drilling, GEOTECH TEST BORING Lola 15620 - 76TH AVENUE WEST EDMONDS, WA Job no; Dale! qed by? I Plate., 13245' 4JAPi 1. 7 QRW RECEIVED Jul 1.6 2021 G�T1' pO�yF�. EDMON N Its BORING 3 GEP RtMEA p Boll . ' .._...._ .. ... _. � • Brownlmotiled, sllt�'SAND'1�t�ith g�'U�i� �e.�y'ir++�t;'l�as�:: -.--- - - . -lens of Ot Brown, gravelly SAND same silt ' coarse -grained' wet dense l 50/411 a , 2 24 iS 3 25 4. 1 --.20 I 25 5 30 3� d4 1-53 1 uray, silty SAND, very fine-grained, vv t,.rriedlilrti-dense becomes less silty, moist -becomes wet _. -lens of silt _._ �c ... ...... _...,, Gray SAND, medium -trained, moist, dense Test boring was k'minated at 26.5 Feet below grade on 1-1$-97, Groundwater seepage 4vas encountered at 3' during drilling. AA#- GEOTECH G'ONSULTA TPS, INC. TEST BORING LOG 15620 - 76TH AVENUE -WEST EDMONDS, WA .lab No. D.1te: fag�:.eedd'b Alata: 13249 BAN 199r DR 9 20! 10] 100 200 RECEIVED Jul 16 2021 CITY OF EDMONDS DEVELOPMENT SERVICES QEPARTMENT aoo GEOTECH 440 too Geologic Cross Section 15620 72nd Amiue'Nest Seattle, Washing,on Jab No: 1,08te. ?la1a: 13246 1 J420`t3 NG$=I. r0 SJope backfill away from foundation. Provide surl drains where necessary, Backfill (See text for '. requirements) " C , F'x+/ti Nonwoven Geotextile ' �= Washed Rock (7/8" rain. size) ' 4" min. Tightline Roof Drain (Do not connect to footing drain) Filter Fabric o _, Possible Slab "4aP �FiIF.� I al 4" Perforated Hard PVC Pipe (Invert at least 5 inches below slab or crawl space. Slope to drain to appropriate outfall. Place holes downward.) Jul 16 2021 CITY OF EDMONDS DEVELOPMENT SERVICE'. DEPARTMENT pP p7�•Fav-��?9a�pox'�•sE °ya Pi .3 J. Vapor Retarded5arrier and Capillary BreaWDrainage Layer (Refer to Report text) NOTES: (1) In crawl spaces, provide an outlet drain to prevent buildup of water that bypasses the perimeter footing drains. (2) Refer to report text for additional drainage, waterproofing, and siab considerations. SkAr GEOTECH . CONSULTANTS, Lei C. FOOTING.DRAIN DETAIL 15620 72nd Avenue West Edmonds, Washington Job No: date '13245 Date: JuEy 2013 1, RECEIVED Jul 16 2021 A CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT 1 3 I i APPENDIX GEOTECH CONSULTANTS, INC. r-� RECEIVED E Jul 16 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT I' • f� 7 AD 3 • :a.' l 'tom � f � ; "0� E North Edmonds I Earth Subsidence and Landslide Hazard Areas Mai } � z r�"- �; • � � � a Legend Ncrih Edmonds Earth Sulmidonee and Landslide Hazard Area Q{See ECDC 23.=020 t3.1 and ECDC 19.lad � � > (ROIL-.Eoundaries are the apFroximats e}rrer:t w aft of previous }artdalfdirg; hara.rds ors prxsant • � r a�-1-:p� � � ••• adjacent to the tsndslide bcunderies) Ste opove S[opaAreas: Iff?5 f ,ryh �r L � S, �, h' r .k ti• .rs Pf Stof 40%or ateeperarA �� r with a �elilcal relief of ten (i0) ft or more�ia (See ECDC 23.50.020 8,2) NInimum butler equal to the height r of ihes.aep slope or 5t] peat, vrhichever ' ,•' .' �. i� � -•�, r i is grDaler (see ECOC 23.80.070 A.1) —�• 1 w �'"•'+(Thehuffershown isthe m!NrwnIbutfar r r.rl' r iFi i — — adjacent to the hlerth Edmunds,Aittsidenc and landslide Hazard Area; asirnliar 6utferrlvuld apply :a sleep sicFe aresa but Is net a ma on US crap far clarhy) r � 2R"(opxraphic�art3ovr •s[,. + '-,��-qq��'-�,.� � c °• t Wdk14f dalurn: i1L?,VE]e a aMemm a '167 xd ;� -� s • ra r � f /1�6riGIL'd 6ylA1LS91I.�Od�66.1p; (Ny�AL'} •I p •ly 11. y ••r". �- ! ) ThgeMIJD&R JoL% CNAYmd,r ina rtfrEB uhry�s: :m5'didid : •; •�'[�'¢s`S fA�' ",'� } 'L• 'r •�S' -- ,rur 1 101;r•J e l i I� I e rolenu�r lanacl:ae M azanl nrco and garter Equal to rh* ".1shr,.r lfw stoop Wes: 31apc ar so R Wnlehervk Crca'sr East mwh Edmond- E" 8u3xLuence xnd UrILVl+.'r ll—ld Are. rjCw 19.l Di EftYG13fA . one ion. zbnw Y I L I I t { iblwrAlsppu .I srotmdbNAea - - I I-. . � :`� F'aIa16.Y osp7s;ff,:_.sl�ac`w rP{i91.ri.i: • _ _ •�!�nR�LeniiNid'. , sew fJi!`;f:;_ ;• ^>tlmaTp�•d'. 6".' .. . Jar �..=„1!-�''.a5 •. Z:.ti .�..14' r `•i, ' loa.wrdi.r9.swn. - :'.:. �i�„ .,_`'j:.• r�•:_•:-.� �f.;.�.,� :;tdu_ r I I SbpulrpolQpl� R„ k �L r r € ,� rx fibs{hv Iryi 1 .f-r,�' _ �� t+sri'.t'd''.+.•r•'�SSSS :Y�'-•. _ _ .',: �• �.^5,. ' 'i Gal �' .. '+ ,�.•,.'u,""d':�.�'��, i.SFr'.:=rLil:"�5,:,�•:k�:}.:;::. :lir.. 1 rsvono5ed�u :i-1tf�y:'v. tirlti Iti� _ ! r _ - ,:i.�(:•i. _ � 1. •r'v .i• - j,a - ' ��_ -- :y. ..... - - I � ww,dl Laty45�fe 'A. _ •�i;��,. 4,.� 71. iYi1.7.•..• - il��'Lt... ,-:y _ _ I � SlopeYrCULtly- �,: .}.• l _-•��.�,i„-•-�s��.. _ �i.;.'... .r'~•`f'�js1'•-�i. ti;s_ , I r - f'• - :�:'+; - •.l`4;•rF€.�;"''J y}rr.lixk,�'ly��r�3'klxr'��';.,t'ti.l}: •,;.�;: .,+.. _ .. - _ .- , 1w, Iw • !'-i $r _ r� t�a�L+r.,uS;�F�:. f,rr+rws� +5�i1 i. I ., .i�{ter t_.•.�j.�;3ri i.,i..'rrk•.1•- Pobanuel[ape-Sw7e I.w - ;. :i.�.:, SJ�_{1:s're}Sy,•'rrF1 WIN -r.{•_-. r.: ;k _ _,.;�,y._ _ . S1ep�IrOIY�IY@ -J+-• �N': .i•Sip.f•'s fj1Y,Yx:1I.�75rR_}!-r'• I. j•.w:`.R•: '.I .I: _ }_. .-'; .. - "I i •� V':��. ,�::q==^•..� r..,ruwWfk I i Yl}i If i'in�i 3n,^�i�. �,i.j`�1,-��-�rs:`:is z�:�:`. 4, „ .r, •s - Pube:I9hN6 .. ? ..� t .�]Kn. 11f. aiMlrNSu+rd 11JI�Yi�a'y.le�'' ;IL. i. •PsAvldalrlert> ••, F•.i.. '�'Jy" -••9dieui�ifdigHy(rii`ellelirl]e;•aCaS Er'it,;}. _ - -- .�•-••w�'M7W ,.i : .1 .� - :'i� �3-''-c','�s •ti.:.,+r •�' _ n4 �°f°H•iprikHe ry rirA'r'tlFY��o 54, .i ii•= ._i i - - �FfaiWq - y..ii } i.� - • '�{s'e L-sl'.,.:L'dl i. +:4Y: 1 r, ' - rPdr!►.:.'. r, ,.._ e . . - ... .. . ' - - :jr'.; Y:'-i:r.. '� 2• -i' .. '.:. i.l•: 1�^7.:s !I~�!is'L.}"- -''1 :'r.l :.•'j,�.S=•sP�l.:tlr�' Qeyl, wrW.- - �: .. _ �,5•: i �i'S-n�r: SPi• - i+ •y<:..q�.t,�ii . J.li.+i 'R••i: i. •';:I` _ �T:r: pl+i.'LrCi ul' •.'�,��.}!rr!rIe1Y�(n.Pl7iliwi aRi';:I Lu MAU R 700 ono r+mm eciffm d. rwm zwbdde and Lsrtdedde North Comoods LandslideAtox r•rx��in.�3�.ue:r�r-•� Hama Area Gea1o9Y and Slide Mechanisms vamcm c+�ca.raeal=n Edmonea�Wuhk�yrr fture Profi 1 e . out Pcs'T'ABL6 by Purdue university modified by Peter 3. Bosscher university of Wisconsin -Madison --Slope 5ta'oil�ty analysis -- Simplified _72nbu, simplified Bishop or spencers method of slices PROBLEM DESCRIPTION BOUNDARY COORDINATES 4 Tap Boundaries 4 Fatal Boundaries Boundary X-Left Y-Left No. (ft) (ft) 1 0.00 0.00 2 95.00 19.00 3 140.00 58.00 4 192.00 93.00 ISOTROPIC SOIL PARAMETERS 2 Type(s) of Soil RECEIVED Jul 16 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT STAIlC. b,�-�Yas X-Right Y-Right soil Type (ft) (ft) Below Brd 95.00 18.00 2 140.00 58.00 2 192.00 99.00 1 510.00 163.00 1 Soil Total saturated cohesion Friction Pore Pressure Piet. Type Unit Wt. unit Wt. Intercept Angle Pressure Constant surface No. (pcf) (pcf) (psf) (deg) Param. (psf) No. 1 135.0 145.0 200.0 40.0 0.00 0.0 0 2 125.0 135.0 300.0 33.0 0.00 0.0 0 1 PIEZOMETRIC SURFACE(S) HAVE BEEN SPECIFIED Page 1 I Profile.out unit weight of Water = 62.40 Piezometric surface No. 1 specified by 2 coordinate Paints Point X-water Y-eater No. (ft) (ft) 1 140.00 58.00 2 510.00 58.00 A Critical Failure Surface Searching ,Method, using A Random Technique For Generating circular Surfaces, Has Been specified. 225 Trial surfaces Have Been Generated. 15 surfaces Initiate FrOm Each Of 15 Points Equally spaced Along The Gr❑und Surface Between X = 60.00 ft. and X � 110.00 ft. Each surface Terminates Between x 242.00 ft. and x = 245.00 ft. UnI esS Further Limitations were Imposed, The Minimum Elevation At which A Surface Extends Is Y = 0.00 ft, 10.60 ft. Line Segments Define Each Trial Failure surface,. Following Are Displayed The Ten most Critical of The Trial Failure surfaces Examined. They Are ❑rdered - Most critical First. * * safety Factors are Calculated 6y The modified 3anbu Method Failure Surface specified By 19 Coordinate Points Point X-Surf Y-Surf No. (ft) [-Ft) 1 95.71 18.64 2 105.47 20.82 3 115.14 23.40 4 124.69 26.35 5 134.12 29.68 6 143.41 33.38 7 152.55 37,44 8 161.52 41.86 9 170.31 46.63 Page 2 RECEIVED Jul 16 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT RECEIVED Jul 16 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Profile.out 10 178.90 51.75 11 187.28 57.19 12 195.45 62..97 13 203.37 69.07 14 211.06 75.47 15 219.48 82:17 16 225.63 89:16 17 232.50 96,43 18 239.08 103.96 19 243.39 109.31 1.512 Failure Surface Specified By 19 coordinate Points Point X--Surf Y-Surf No. (ft) (ft) .1 95.71 18.64 2 105.53 20.56 3 115.25 22.91 4 124.86 25.66 5 134.35 28.81 6 143.70 32.,37 7 152.89 36.31 8 161.90 40.64 9 170.72 45.35 10 179.34 50.43 11 187.73 55.87 12 195.89 61.65 13 203.79 67.78 14 211.43 74.24 15 218.78 81.01 16 225.85 88.09 17 232.61 95.46 18 239.05 103.11 3.9 243.93 109.43 1.518 Failure surface specified By 21 coordinate Points Point X-surf Y-surf No. (ft) (ft) 1 85.00 16.11 2 94.96 17.03 3 104.86 18.44 4 114.68 20.33 5 124.39 22.69 6 133.98 25.53 7 143.42 28.82 8 152.69 32.58 9 161.77 36.78 10 170.63 41.42 Page 3 RECEIVED Jul 16 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Profile.out 11 179.25 46.48 12 187.62 51.96 13 195.71 57.83 14 203.50 64.10 15 210.98 70.73 16 218.13 77.73 17 224.93 85.06 18 231.37 92.72 19 237.42 100.67 20 243.08 108.92 21 243.31 109.29 �* 1.521 *� Failure Surface Specified By 22 coordinate Points Point X-surf Y-surf No. (ft) (ft) 1 74.29 14.08 2 84.26 14.85 3 94.18 16.08 4 104.04 17.75 5 113.81 19.88 6 123.48 22.45 7 133.01 25.45 8 142.40 28.89 9 151.63 32.75 10 160.67 37.02 11 169.50 41.71 12 178.12 46.79 13 186.49 52.26 14 194.60 58.10 15 202.44 64.31 16 209.99 70.87 17 217.24 77.76 18 224.16 84.98 19 230.74 92.50 20 236.98 100.32 21 242.85 108.41 22 243.45 109.33 *� 1.523 �h Failure Surface Specified By 22 Coordinate Points Point X-Surf Y-Surf No. (ft) (ft) 1 67.14 12.72 2 77.14 12.87 3 87.12 13.51 4 97.06 14.63 5 106.93 16.24 6 116.71 18.32 Page 4 RECEIVED Jul 16 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Profile.out 7 126.38 20.88 8 135.91 23.90 9 145.28 27.38 10 154.48 31.32 11 163.47 35.70 12 172.23 40.51 13 180.76 45.74 14 189.02 51.38 15 196.99 57.41 16 204.66 63.82 17 212.01 70.60 18 219.03 77.73 19 225.68 85.20 20 231.97 92.97 21 237.87 101.05 22 243.30 109.29 1.527 *** Failure surface specified By 19 Coordinate Points Point X-Surf Y-Surf No. (ft) (ft) 1 95.71 18.64 2 105.09 22.11 3 114.38 25.81 4 123.58 29.73 5 132.69 33.86 6 141.70 38.20 7 150.60 42.75 8 159.40 47.51 9 168.08 52.47 10 176.64 57.64 11 185.08 63.01 12 193.39 68.57 13 201.57 74.33 14 209.61 80.27 15 217.50 86.40 16 225.26 92.72 17 232.86 99.22 18 240.31 105.89 19 244.12 109.47 1.529' Failure Surface specified By 22 Coordinate Points Point X-Surf Y-Surf No. Cft) (ft) 1 74.29 14.08 2 84.28 14.35 3 94.25 15.13 4 104.17 16.40 Page 5 RECEIVED 255.04 T 91:25i � 1.27', 63. 00 Jul 16 2021 CITY OF EDMONDS DEVELOPMENT SERVICES Safety Fsctors DEPARTMENT 1.51 1.52 1.52 1.52 1.53 1.63 1.53 1.53 1.53 t54 Prof-ile.out PCSTABL6 b Purdue University modified by Peter J. Bosscher Univer$ity of Wisconsin -Madison RECEIVED Jul .1,6 2021 ICES V NAM R 1VV1 �3 DEPJJJ��RRRTTTvMM1ENT K/ - G &J - -slope stability Analysis -- simplified Janbu, simplified Bishop or Spencer's Method of Slices PROBLEM DESCRIPTION BOUNDARY COORDINATES 4 Top Boundaries 4 Total Boundaries Boundary X-Left Y-Left x-Right Y-Right Soil Type No. (ft) (ft) (ft) (ft) Below Bnd 1 0.00 0.00 95.00 18,00 2 2 95.00 18.00 148.00 58,00 2 3 148.00 58.00 192.00 98,00 1 4 192-00 98.00 510.00 168.00 1 ISOTROPIC SOIL PARAMETERS 2 Type(s) of Soil soil Total saturated cohesion Friction Pore Pressure Piez. Type Unit Olt. Unit Wt. Intercept Angle Pressure Constant Surface No. (Pcf) (Pcf) (Psf) (deg) Param. [psf) No 1 135.0 145.0 200.0 40.0 0.04 0.0 0 2 125.0 135.0 300.0 33.0 0.00 0.0 0 1 PIEZOMETPIC SURFACE(5) HAVE BEEN SPECIFIED Page I RECEIVED Jul 16 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Profile.out Unit weight of water = 62.40 Piezometric surface No. 1 specified by 2 coordinate Points Point X-Water Y-water No. (ft) (ft) 1 148.00 58.00 2 510.00 58.00 A Horizontal Earthquake Loading coefficient Of0.160 Has Been Assigned A vertical Earthquake Loading Coefficient Of0.000 Has Been Assigned j cavitation Pressure = 0.0 psf A Critical Failure Surface Searching Method, Using A Random Technique For Generating circular surfaces, Has Been specified. 400 Trial surfaces Have Been Generated. 20 Surfaces initiate From Each of 20 Points Equally spaced Along The Ground surface Between X = 60.00 ft. and X = 110.00 ft. Each surface Terminates Between X = 242.00 ft. and X = 245.00 ft. Unless Further Limitations Were imposed, The Minimum Elevation At which A Surface Extends Is Y = 0.00 ft. 10.00 ft. Line Segments Define Each Trial Failure surface. Following Are Displayed The Ten Most Critical Of The Trial Failure surfaces Examined. They Are Ordered - Most critical First. Safety Factors Are Calculated By The Modified Bishop Method Failure Surface Specified By 19 Coordinate Points Point X-Surf Y-surf No. (ft) (ft) Page 2 RECEIVED Jul 16 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT 1 96.84 2 106.52 3 116.09 4 125.56 5 134.90 6 144.11 7 153.17 8 162.07 9 170.80 10 179.34 11 187.69 12 195.84 13 203.77 14 211.47 15 218.94 16 226.16 17 233.12 18 239.82 19 242.11 Circle Center At X * 1.120 v: Profile.out 19.39 21.92 24.80 28.02 31.59 35.49 39.73 44.29 49.17 54.36 59.86 65.66 71.76 78.13 84.78 91.70 98.88 106.30 109.03 32.0 ; Y = 287.1 and Radius, 275.4 Failure Surface specified By 19 Coordinate Points Point X--Surf NO. (ft) 1 99.47 2 109.21 3 118.84 4 128..36 5 137:75 6 147.00 7 156.10 8 165.02 9 173.76 10 182.29 11 190.62 12 198.72 13 206.58 14 214.19 15 221.54 16 228.62 17 235.41 18 241.91 19 242.62 Circle Center At X Y-surf (ft) 21.38 23.67 26.35 29.41 32.84 36.64 40.81 45.32 50.19 55.40 60.94 66.80 72.98 79.46 86.24 93.31 100.65 108.25 109.14 46.1 ; y = 269.0 and Radius, 253.4 1.133^ Failure surface Specified By 19 Coordinate Points Page 3 I , 0 a .JQ RECEIVED Jul 16 2021 CITY OF EDMONDS DEVELOPMENT SERVICES Safety Factors DEPARTMENT RECEIVED Jul 16 2021 CITY OF EDMONDS DEVELOPMENT SERVICES RTMENT Profile.out =' PCSTABL6 * by� Purdue university modified by Peter J. Bosscher University of Wisconsin --Madison --slope stability Analysis --- simplified Janbu, Simplified Bishop or spencer's method of slices PROBLEM DESCRIPTION BOUNDARY COORDINATES 4 Top Boundaries 4 Total Boundaries Boundary x-Left Y-Left x-Right Y-Right Soil Type No- (ft) (ft) (ft) (ft) Below Bnd 1 0.00 0.00 95.00 18.00 2 2 95.00 18.00 148.00 58.00 2 3 148.00 58.00 192.00 98.00 1 4 192.00 98.00 510.00 168.00 1 ISOTROPIC SOIL PARAMETERS 2 Type(s) of soil Soil Total Saturated Cohesion Friction Pore Pressure Piez. Type Unit Wt. Unit Wt. Intercept Angle Pressure Constant Surface No. (pcf) (pcf) (psf) (deg) Param. (psf) No. 1 135.0 145.0 200.0 40.0 0.00 0.0 0 2 125.0 135.0 300.0 33.0 0.00 0.0 0 1 PIEZOMETRIC SURFACE(S) HAVE BEEN SPECIFIED Page 1 RECEIVED Jul 16 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Profile.out Unit weight of water = 62.40 Piezometric surface No. 1 specified by 2 coordinate Points Point X-water Y-water No. (ft) (ft) 1 148.00 58.00 2 510.00 58.00 A Horizontal Earthquake Goading coefficient Of0.160 Has Been Assigned A vertical Earthquake Loading Coefficient Of0.000 Has Been Assigned Cavitation Pressure = 0.0 psf A critical Failure surface searching Method, using A Random Technique For Generating circular surfaces, Has Been Specified. 400 Trial Surfaces Have Been Generated. 20 surfaces Initiate From Each Of 20 Points Equally spaced Along The Ground surface Between X = 60.00 ft. and X = 110.00 ft. Each surface Terminates Between x = 257.00 ft. and x = 300.00 ft. unless Further Limitations were Imposed, The Minimum Elevation At which A surface Extends is Y = 0.00 ft. 10.00 ft. Line Segments Define Each Trial Failure surface. Following Are Displayed The Ten Most Critical Of The Trial Failure Surfaces Examined. They Are Ordered - Most Critical First. safety Factors Are calculated By The Modified Bishop Method Failure surface specified By 20 coordinate Points Point x--surf Y-Surf No. (ft) (ft) Page 2 ? � l Profile.aut 1 96.84 19.39 2 106.30 22.63 3 115.69 26.07 4 125-01 29.71 5 134.24 33.55 6 143.39 37,59 7 152.45 41.83 8 161.41 46.26 9 170.28 50.88 10 179.04 55.70 11 187.70 60.70 12 196.25 65.89 13 204.68 71.27 14 213.00 76..82 15 221.19 82.55 15 229.26 88.46 17 237.20 94- 54 18 245-00 100.79 19 252.67 107.21 20 259.00 112.75 Circle center At X = -48.1 ; Y = 453.7 and Radius, 462.6 e.v;* 1.179 *** Failure Surface Specified By 21. Coordinate Points Point X-surf Y-surf NO. ( t) (f't) 1 96.84 19.39 2 106-61. 21.-54 3 116.30 24.92 4 125.89 26.83 5 135.39 29.96 6 144.78 33.41 7 154.04 37.18 8 163.17 41.26 9 172.16 45.65 10 180.99 50.33 11 189.66 55.32 12 198.16 60.59 13 206.47 66.15 1.4 2-14.59 71.99 15 222.50 78.10 16 230.21 84.47 17 237.69 91.10 18 244.95 97.98 19 251.97 105.11 20 258.74 11.2.46 21 258.98 112.74 Circle ceriter At X = 38.2 ; Y = 308.7 and Radius, 295.2 �* 1.182 *** Page 3 RECEIVED Jul 16 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT RECEIVED Jul 16 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Profile.out Failure Surface Specified By 20 Coordinate Points Point X-surf Y-Surf NO. (ft) (ft) 1 99.47 21.38 2 109.24 23.52 3 118.93 26.00 4 128.53 28.80 5 138.02 31.94 6 147.41 35.40 7 156.67 39.17 8 165.79 43.27 9 174.77 47.67 10 183.59 52.38 11 192.24 57.39 12 200.72 62.70 13 209.01 68.29 14 217.11 74.16 15 225.00 80.30 16 232.67 86.72 17 240.12 93.39 18 247.33 100.31 19 254.30 107.48 20 259.11 112.77 circle center At X = 41.9 ; Y = 307.1 and Radius, 291.5 1.193 Failure Surface Specified By 21 Coordinate Points Point X-surf Y-Surf No. (ft) (ft) 1 96.84 19.39 2 106.75 20.78 3 116.58 22.59 4 126.33 24.82 5 135.97 27.46 6 145.50 30.50 7 154.89 33.95 8 164.12 37.80 9 173.17 42.04 10 182.05 46.65 11 190.71 51.64 12 199.16 57.00 13 207.37 62.70 14 215.33 68.76 15 223.02 75.14 16 230.44 81.85 17 237.57 88.87 18 244.39 96.18 19 250.89 103.78 20 257,06 111.64 21 257.65 112.45 Page 4 RECEIVED Jul 16 2021 CITY OF EDMONDS r DEVELOPMENT SERVICES S'arety r:aCtors DEPARTMENT 1.18 1.1a 1AD 1.20 1.21 1.22 i 1.22 1.22 1.23 1,23 GEOTECH CONSULTANTS, INC_ Johnston Design Group 411 University Ridge, Suite D Greenville, South Carolina 29601 Attention: Scott Johnston via email: Scott@johnstondesigngroup.us Subject: Geotechnical Engineering Study Proposed Ahern Residence 15722 — 72nd Avenue West Edmonds, Washington RECEIVED 244W11 $A Aft Seattle, Washhuoa E�TEW$Ey02C ��L��P��Yh1Eh�lll2S ES October 16, 2017 J N 17557 Our firm has prepared a geotechnical engineering study for the proposed Meadowview Estates short -plat project dated October 9, 2013. The proposed single-family residence that is under consideration in this report is located in the more southwestern portion of the short -plat. This report relies on the information contained in the study for the short -plat property, and provides geotechnical engineering design parameters for the new residence. The western edge of the short -plat property and the subject residential property contains a very steep slope. However, only a mostly gentle to moderate slope rise to the east above this steep slope. One of the main conclusions and recommendations noted in our study was that, based on stability analyses performed regarding the steep western slope, a 65-foot setback from the steep western slope should be maintained for new residences if standard footing foundations were used for new residences. Based on a recent site plan we received for the project, which was prepared by Johnston Design Group, the new residence on the subject site will indeed be located at least 65 feet from the steep western slope. In addition, we understand that stormwater from impervious site surfaces will discharge to an existing stormwater system. If the scope of the project changes from what we have described above, we should be provided with revised plans in order to determine if modifications to the recommendations and conclusions of this report are warranted. CONCLUSIONS AND RECOMMENDATIONS GENERAL THIS SECTION CONTAINS A SUMMARY OF OUR STUDY AND FINDINGS FOR THE PURPOSES OF A GENERAL OVERVIEW ONLY. MORE SPECIFIC RECOMMENDATIONS AND CONCLUSIONS ARE CONTAINED IN THE REMAINDER OF THIS REPORT. ANY PARTY RELYING ON THIS REPORT SHOULD READ THE ENTIRE DOCUMENT. GENERAL Several test pits and borings were conducted in the past as noted in our 2013 study in the area of the proposed residence, and these explorations encountered medium -dense to dense, sometimes very dense, gravelly sand soils at shallow depths. This soil is very competent for supporting building loads, and thus conventional footings that bear on this competent soil can be used as the foundation of the new residence. These soils also have high shear strength against slope instability. GEOTECH CONSULTANTS, INC. Johnston Design Group October 19, 2017 REGEWED Jupm2k i CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT As was noted in October 9, 2013 study for the entire short -plat, an "alteration" is needed per Edmonds Code for this project because the overall setback of 65 feet noted above is shorter than the default overall setback of about 95 to 105 feet (equal to the height of the western steep slope plus 15 feet). Based on the code, ECDC•23.BO.060.A, an alteration to a Landslide Hazard Area and associated buffer may occur for activities that: 1. Will not increase the threat of the geologic hazard to adjacent properties beyond predevelopment conditions; 2. Will not adversely affect other critical areas; 3. Are designed so that the hazard to the project is eliminated or mitigated to a level equal to or less that predevelopment conditions; and 4. Are certified as safe as designed and under anticipated conditions by a qualified engineer licensed in the State of Washington. In addition, ECDC 23.BO.070.A.3 indicates that alterations of a Landslide Hazard Area and buffer may occur for activities for which a hazards analysis is submitted and certifies that: 1. The development will not increase surface water discharge or sedimentation to adjacent properties beyond predevelopment conditions; 2. The development will not decrease slope stability on adjacent properties; and 3. Such alterations will not adversely impact other critical areas. As noted above, we performed full stability analysis on the property that included the steep western slope and an overall setback of 65 feet met all of the stability requirements. In addition, as is recommended earlier, all loads for the residence will be founded on medium -dense to dense or denser native soil. Because of these reasons, because the site stormwater will be taken to an existing stormwater system (which lowers the amount of water that reaches the western slope and thus provides some increase to the slope's stability), it is our professional opinion that this proposed development meets the seven standards noted above in both ECDC 23.80.060 and 070 provided the recommendations of this report are followed. The erosion control measures needed during the site development will depend heavily on the weather conditions that are encountered. We anticipate that a silt fence will be needed around the downslope sides of any cleared areas. Existing pavements, ground cover, and landscaping should be left in place wherever possible to minimize the amount of exposed soil. Rocked staging areas and construction access roads should be provided to reduce the amount of soil or mud carried off the property by trucks and equipment. Wherever possible, the access roads should follow the alignment of planned pavements. Trucks should not be allowed to drive off of the rock -covered areas. Cut slopes and soil stockpiles should be covered with plastic during wet weather. Following clearing or rough grading, it may be necessary to mulch or hydroseed bare areas that will not be immediately covered with landscaping or an impervious surface. On most construction projects, it is necessary to periodically maintain or modify temporary erosion control measures to address specific site and weather conditions. The drainage and/or waterproofing recommendations presented in this report are intended only to prevent active seepage from flowing through concrete walls or slabs. Even in the absence of active seepage into and beneath structures, water vapor can migrate through walls, slabs, and floors from the surrounding soil, and can even be transmitted from slabs and foundation walls due to the concrete curing process. Water vapor also results from occupant uses, such as cooking and bathing. Excessive water vapor trapped within structures can result in a variety of undesirable GEOTECH CONSULTANTS, INC. Johnston Design Group October 19, 2017 REGEWED Juf @g'2k1 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT conditions, including, but not limited to, moisture problems with flooring systems, excessively moist air within occupied areas, and the growth of molds, fungi, and other biological organisms that may be harmful to the health of the occupants. The designer or architect must consider the potential vapor sources and likely occupant uses, and provide sufficient ventilation, either passive or mechanical, to prevent a buildup of excessive water vapor within the planned structure. Geotech Consultants, Inc. should be allowed to review the final development plans to verify that the recommendations presented in this report are adequately addressed in the design. Such a plan review would be additional work beyond the current scope of work for this study, and it may include revisions to our recommendations to accommodate site, development, and geotechnical constraints that become more evident during the review process. We recommend including this report, in its entirety, in the project contract documents. This report should also be provided to any future property owners so they will be aware of our findings and recommendations. Geotech Consultants, Inc. should be allowed to review the final development plans to verify that the recommendations presented in this report are adequately addressed in the design. Such a plan review would be additional work beyond the current scope of work for this study, and it may include revisions to our recommendations to accommodate site, development, and geotechnical constraints that become more evident during the review process. We recommend including this report, in its entirety, in the project contract documents. This report should also be provided to any future property owners so they will be aware of our findings and recommendations. SEISMIC CONSIDERATIONS In accordance with the International Building Code (IBC), the site class within 100 feet of the ground surface is best represented by Site Class Type D (Stiff Soil Class). As noted in the USGS website, the mapped spectral acceleration value for a 0.2 second (S5) and 1.0 second period (S1) equals 1.33g and 0.52g, respectively. The site soils are not susceptible to seismic liquefaction during a large earthquake because of their dense nature and/or the absence of near -surface groundwater. CONVENTIONAL FOUNDATIONS The proposed structure can be supported on conventional continuous and spread footings bearing on undisturbed, medium -dense to dense, native sand soil. We recommend that continuous and individual spread footings have minimum widths of 16 and 24 inches, respectively. Exterior footings should also be bottomed at least 18 inches below the lowest adjacent finish ground surface for protection against frost and erosion. The local building codes should be reviewed to determine if different footing widths or embedment depths are required. Footing subgrades must be cleaned of loose or disturbed soil prior to pouring concrete. Depending upon site and equipment constraints, this may require removing the disturbed soil by hand. An allowable bearing pressure of 3,000 pounds per square foot (psf) is appropriate for footings supported on competent native sand soil. A one-third increase in this design bearing pressure may be used when considering short-term wind or seismic loads. For the above design criteria, it is anticipated that the total post -construction settlement of footings founded on competent native soil will be about one-half inch, with differential settlements on the order of one-half inch in a distance of 50 feet along a continuous footing with a uniform load. GEOTECH CONSULTANTS, INC. Johnston Design Group October 19, 2017 RWEIVED JLP419(2421 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Lateral loads due to wind or seismic forces may be resisted by friction between the foundation and the bearing soil, or by passive earth pressure acting on the vertical, embedded portions of the foundation. For the latter condition, the foundation must be either poured directly against relatively level, undisturbed soil or be surrounded by. level, well -compacted fill. We recommend using the following ultimate values for the foundation's resistance to lateral loading: PARAMETER ULTDIATE Coefficient of Friction 0.50 Passive Earth Pressure 300 pcf Where: pcf is Pounds per Cubic Foot, and Passive Earth Pressure is computed using the Equivalent Fluid Density. If the ground in front of a foundation is loose or sloping, the passive earth pressure given above will not be appropriate. We recommend maintaining a safety factor of at least 1.5 for the foundation's resistance to lateral loading, when using the above ultimate values. FDif INDA MAI AND RETAINING WALLS Retaining walls backfilled on only one side should be designed to resist the lateral earth pressures imposed by the soil they retain. The following recommended parameters are for walls that restrain level backfill: i Active Earth Pressure * 35 pcf Passive Earth Pressure 300 pcf Coefficient of Friction 0.50 Soil Unit Weight 130 pcf Where: pcf is Pounds per Cubic Foot, and Active and Passive Earth Pressures are computed using the Equivalent Fluid Pressures. * For a restrained wall that cannot deflect at least 0.002 times its height, a uniform lateral pressure equal to 10 psf times the height of the wall should be added to the above active equivalent fluid pressure. The design values given above do not include the effects of any hydrostatic pressures behind the walls and assume that no surcharges, such as those caused by slopes, vehicles, or adjacent foundations will be exerted on the walls. If these conditions exist, those pressures should be added to the above lateral soil pressures. Where sloping backfill is desired behind the walls, we will need to be given the wall dimensions and the slope of the backfill in order to provide the appropriate design earth pressures. The surcharge due to traffic loads behind a wall can typically be accounted for by adding a uniform pressure equal to 2 feet multiplied by the above active fluid density. Heavy construction equipment should not be operated behind retaining and foundation walls within a distance equal to the height of a wall, unless the walls are designed for the additional lateral pressures resulting from the equipment. The values given above are to be used to design only GEOTECH CONSULTANTS, INC. Johnston Design Group October 19, 2017 REGEWED CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT permanent foundation and retaining walls that are to be backfilled, such as conventional walls constructed of reinforced concrete or masonry. It is not appropriate to use the above earth pressures and soil unit weight to back -calculate soil strength parameters for design of other types of retaining walls, such as soldier pile, reinforced earth, modular or soil nail walls. We can assist with design of these types of walls, if desired. The passive pressure given is appropriate only for a shear key poured directly against undisturbed native soil, or for the depth of level, well -compacted fill placed in front of a retaining or foundation wall. The values for friction and passive resistance are ultimate values and do not include a safety Restrained wall soil parameters should be utilized for a distance of 1.5 times the wall height from corners or bends in the walls. This is intended to reduce the amount of cracking that can occur where a wall is restrained by a corner. Wall Pressures Due to Seismic Forces The surcharge wall loads that could be imposed by the design earthquake can be modeled by adding a uniform lateral pressure to the above -recommended active pressure. The recommended surcharge pressure is 8H pounds per square foot (psf), where H is the design retention height of the wall. Using this increased pressure, the safety factor against sliding and overturning can be reduced to 1.2 for the seismic analysis. Retaining Wall Backfill and Waterproofing Backfill placed behind retaining or foundation walls should be coarse, free -draining structural fill containing no organics. This backfill should contain no more than 5 percent silt or clay particles and have no gravel greater than 4 inches in diameter. The percentage of particles passing the No. 4 sieve should be between 25 and 70 percent. If the native sand is used as backfill, a drainage composite similar to Miradrain 6000 should be placed against the backfilled retaining walls. The drainage composites should be hydraulically connected to the foundation drain system. The later section entitled Drainage Considerations should also be reviewed for recommendations related to subsurface drainage behind foundation and retaining walls. The purpose of these backfill requirements is to ensure that the design criteria for a retaining wall are not exceeded because of a build-up of hydrostatic pressure behind the wall. Also, subsurface drainage systems are not intended to handle large volumes of water from surface runoff. The top 12 to 18 inches of the backfill should consist of a compacted, relatively impermeable soil or topsoil, or the surface should be paved. The ground surface must also slope away from backfilled walls to reduce the potential for surface water to percolate into the backfill. Water percolating through pervious surfaces (pavers, gravel, permeable pavement, etc.) must also be prevented from flowing toward walls or into the backfill zone. The compacted subgrade below pervious surfaces and any associated drainage layer should therefore be sloped away. Alternatively, a membrane and subsurface collection system could be provided below a pervious surface. It is critical that the wall backfill be placed in lifts and be properly compacted, in order for the above -recommended design earth pressures to be appropriate. The wall design criteria assume that the backfill will be well -compacted in lifts no thicker than 12 inches. The compaction of backfill near the walls should be accomplished with hand -operated equipment to prevent the walls from being overloaded by the higher soil forces that occur during compaction. The section entitled General Earthwork and Structural Fill contains additional recommendations regarding the placement and compaction of structural fill behind retaining and foundation walls. GEOTECH CONSULTANTS, INC. Johnston Design Group October 19, 2017 REGEWED CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT The above recommendations are not intended to waterproof below -grade walls, or to prevent the formation of mold, mildew or fungi in interior spaces. Over time, the performance of subsurface drainage systems can degrade, subsurface groundwater flow patterns can change, and utilities can break or develop leaks. Therefore, waterproofing should be provided where future seepage through the walls is not acceptable. This typically includes limiting cold -joints and wall penetrations, and using bentonite panels or membranes on the outside of the walls. There are a variety of different waterproofing materials and systems, which should be installed by an experienced contractor familiar with the anticipated construction and subsurface conditions. Applying a thin coat of asphalt emulsion to the outside face of a wall is not considered waterproofing, and will only help to reduce moisture generated from water vapor or capillary action from seeping through the concrete. As with any project, adequate ventilation of basement and crawl space areas is important to prevent a buildup of water vapor that is commonly transmitted through concrete walls from the surrounding soil, even when seepage is not present. This is appropriate even when waterproofing is applied to the outside of foundation and retaining walls. We recommend that you contact an experienced envelope consultant if detailed recommendations or specifications related to waterproofing design, or minimizing the potential for infestations of mold and mildew are desired. The General, Slabs -On -Grade, and Drainage Considerations sections should be reviewed for additional recommendations related to the control of groundwater and excess water vapor for the anticipated construction. SLABS -ON -GRADE The building floors can be constructed as slabs -on -grade atop firm native sand or on structural fill. The subgrade soil must be in a firm, non -yielding condition at the time of slab construction or underslab fill placement. Any soft areas encountered should be excavated and replaced with select, imported structural fill. Even where the exposed soils appear dry, water vapor will tend to naturally migrate upward through the soil to the new constructed space above it. This can affect moisture -sensitive flooring, cause imperfections or damage to the slab, or simply allow excessive water vapor into the space above the slab. All interior slabs -on -grade should be underlain by a capillary break drainage layer consisting of a minimum 4-inch thickness of clean gravel or crushed rock that has a fines content (percent passing the No. 200 sieve) of less than 3 percent and a sand content (percent passing the No.4 sieve) of no more than 10 percent. Pea gravel or crushed rock are typically used for this layer. As noted by the American Concrete Institute (ACI) in the Guides for Concrete Floor and Slab Structures, proper moisture protection is desirable immediately below anyon-grade slab that will be covered by tile, wood, carpet, impermeable floor coverings, or any moisture -sensitive equipment or products. ACI also notes that vapor retarders such as 6-mil plastic sheeting have been used in the past, but are now recommending a minimum 10-mil thickness for better durability and long term performance. A vapor retarder is defined as a material with a permeance of less than 0.3 perms, as determined by ASTM E 96. It is possible that concrete admixtures may meet this specification, although the manufacturers of the admixtures should be consulted. Where vapor retarders are used under slabs, their edges should overlap by at least 6 inches and be sealed with adhesive tape. The sheeting should extend to the foundation walls for maximum vapor protection. If no potential for vapor passage through the slab is desired, a vapor barrier should be used. A vapor barrier, as defined by ACI, is a product with a water transmission rate of 0.01 perms when tested in accordance with ASTM E 96. Reinforced membranes having sealed overlaps can meet this requirement. GEOTECH CONSULTANTS, INC. Johnston Design Group October 19, 2017 REGEWED JLP@9(2(721 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT In the recent past, ACI (Section 4.1.5) recommended that a minimum of 4 inches of well -graded compactable granular material, such as a 5/8-inch-minus crushed rock pavement base, be placed over the vapor retarder or barrier for their protection, and as a "blotter" to aid in the curing of the concrete slab. Sand was not recommended by ACI for this purpose. However, the use of material over the vapor retarder is controversial as noted in current ACI literature because of the potential that the protection/blotter material can become wet between the time of its placement and the installation of the slab. If the material is wet prior to slab placement, which is always possible in the Puget Sound area, it could cause vapor transmission to occur up through the slab in the future, essentially destroying the purpose of the vapor barrierl retarder. Therefore, if there is a potential that the protection/blotter material will become wet before the slab is installed, ACI now recommends that no protection/blotter material be used. However, ACI then recommends that, because there is a potential for slab curl due to the loss of the blotter material, joint spacing in the slab be reduced, a low shrinkage concrete mixture be used, and 'other measures" (steel reinforcing, etc.) be used. ASTM E-1643-98 "Standard Practice for Installation of Water Vapor Retarders Used in Contact with Earth or Granular Fill Under Concrete Slabs" generally agrees with the recent AClliterature. We recommend that the contractor, the project materials engineer, and the owner discuss these issues and review recent ACI literature and ASTM E-1643 for installation guidelines and guidance on the use of the protection/blotter material. The General, Permanent Foundation and Retaining Walls, and Drainage Considerations sections should be reviewed for additional recommendations related to the control of groundwater and excess water vapor for the anticipated construction. EXCAVATIONS AND SLOPES Excavation slopes should not exceed the limits specified in local, state, and national government safety regulations. Temporary cuts to a depth of about 4 feet may be attempted vertically in unsaturated soil, if there are no indications of slope instability. However, vertical cuts should not be made near property boundaries, or existing utilities and structures. Based upon Washington Administrative Code (WAC) 296, Part N, the soil at the subject site would generally be classified as Type B. Therefore, temporary cut slopes greater than 4 feet in height should not be excavated at an inclination steeper than 1: 1 (Horizontal:Vertical), extending continuously between the top and the bottom of a cut. The above -recommended temporary slope inclination is based on the conditions exposed in our explorations, and on what has been successful at other sites with similar soil conditions. It is possible that variations in soil and groundwater conditions will require modifications to the inclination at which temporary slopes can stand. Temporary cuts are those that will remain unsupported for a relatively short duration to allow for the construction of foundations, retaining walls, or utilities. Temporary cut slopes should be protected with plastic sheeting during wet weather. It is also important that surface runoff be directed away from the top of temporary slope cuts. Cut slopes should also be backfilled or retained as soon as possible to reduce the potential for instability. Please note that sand can cave suddenly and without warning. Excavation, foundation, and utility contractors should be made especially aware of this potential danger. These recommendations may need to be modified if the area near the potential cuts has been disturbed in the past by utility installation, or if settlement -sensitive utilities are located nearby. All permanent cuts into native soil should be inclined no steeper than 2: 1 (H:V). Water should not be allowed to flow uncontrolled over the top of any temporary or permanent slope. exposed slopes GEOTECH CONSULTANTS, INC. Johnston Design Group October 19, 2017 REGEWED Juf @g'2k1 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT should be seeded with an appropriate species of vegetation to reduce erosion and improve the stability of the surficial layer of soil. DRAINAGE CONSIDERATIONS Footing drains should be used where: (1) Crawl spaces or basements will be below a structure; (2) A slab is below the outside grade; or, (3) The outside grade does not slope downward from a building. Drains should also be placed at the base of all earth -retaining walls. These drains should be surrounded by at least 6 inches of 1-inch-minus, washed rock that is encircled with non -woven, geotextile filter fabric (Mirafi 140N, Supac 4NP, or similar material). At its highest point, a perforated pipe invert should be at least 6 inches below the bottom of a slab floor or the level of a crawl space. The discharge pipe for subsurface drains should be sloped for flow to the outlet point. Roof and surface water drains must not discharge into the foundation drain system. As a minimum, a vapor retarder, as defined in the Siabs-On-Grade section, should be provided in any crawl space area to limit the transmission of water vapor from the underlying soils. Crawl space grades are sometimes left near the elevation of the bottom of the footings. As a result, an outlet drain is recommended for all crawl spaces to prevent an accumulation of any water that may bypass the footing drains. Providing even a few inches of free draining gravel underneath the vapor retarder limits the potential for seepage to build up on top of the vapor retarder. The excavation and site should be graded so that surface water is directed off the site and away from the tops of slopes. Water should not be allowed to stand in any area where foundations, slabs, or pavements are to be constructed. Final site grading in areas adjacent to the residence should slope away at least 2 percent, except where the area is paved. Surface drains should be provided where necessary to prevent ponding of water behind foundation or retaining walls. A discussion of grading and drainage related to pervious surfaces near walls and structures is contained in the Foundation and Retaining Walls section. Water from roof, storm water, and foundation drains should not be discharged onto slopes; it should be tight lined to a suitable outfall located away from any slopes. GENERAL EARTHWORK AND STRUCTURAL FILL All building and pavement areas should be stripped of surface vegetation, topsoil, organic soil, and other deleterious material. The stripped or removed materials should not be mixed with any materials to be used as structural fill, but they could be used in non-structural areas, such as landscape beds. Structural fill is defined as any fill, including utility backfill, placed under, or close to, a building, behind permanent retaining or foundation walls, or in other areas where the underlying soil needs to support loads. All structural fill should be placed in horizontal lifts with a moisture content at, or near, the optimum moisture content. The optimum moisture content is that moisture content that results in the greatest compacted dry density. The moisture content of fill is very important and must be closely controlled during the filling and compaction process. The allowable thickness of the fill lift will depend on the material type selected, the compaction equipment used, and the number of passes made to compact the lift. The loose lift thickness should not exceed 12 inches. We recommend testing the fill as it is placed. If the fill is not sufficiently compacted, it can be recompacted before another lift is placed. This eliminates the need to remove the fill to achieve the required compaction. The following table presents recommended relative compactions for structural fill: or Filled slopes and behind 90% retaining walls 95% for upper 12 inches of Beneath pavements subgrade; 90% below that level Where: Minimum Relative GEOTECH CONSULTANTS, INC. Johnston Design Group REG E WE D October 19, 2017 JuPw2&1 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Compaction is the ratio, expressed in percentages, of the compacted dry density to the maximum dry density, as determined in accordance with ASTM Test Designation D 1557-91 (Modified Proctor). LIMITATIONS The conclusions and recommendations contained in this report are based on site conditions as they existed at the time of our exploration and assume that the soil and groundwater conditions encountered in earlier explorations on and near the subject site are representative of subsurface conditions on the site. If the subsurface conditions encountered during construction are significantly different from those observed in our explorations, we should be advised at once so that we can review these conditions and reconsider our recommendations where necessary. Unanticipated conditions are commonly encountered on construction sites and cannot be fully anticipated by merely taking samples in explorations. Subsurface conditions can also vary between exploration locations. Such unexpected conditions frequently require making additional expenditures to attain a properly constructed project. It is recommended that the owner consider providing a contingency fund to accommodate such potential extra costs and risks. This is a standard recommendation for all projects. The recommendations presented in this report are directed toward the protection of only the proposed structure from damage due to slope movement. Predicting the future behavior of steep slopes and the potential effects of development on their stability is an inexact and imperfect science that is currently based mostly on the past behavior of slopes with similar characteristics. Landslides and soil movement can occur on steep slopes before, during, or after the development of property. The owner of any property containing, or located close to steep slopes, must ultimately accept the possibility that some slope movement could occur at or near the steep western slope. This report has been prepared for the exclusive use of Johnston Architects, the homeowners, and their representatives, for specific application to this project and site. Our conclusions and recommendations are professional opinions derived in accordance with our understanding of current local standards of practice, and within the scope of our services. No warranty is expressed or implied. The scope of our services does not include services related to construction safety precautions, and our recommendations are not intended to direct the contractor's methods, techniques, sequences, or procedures, except as specifically described in our report for consideration in design. Our services also do not include assessing or minimizing the potential for biological hazards, such as mold, bacteria, mildew and fungi in either the existing or proposed site development. ADDITIONAL SERVICES In addition to reviewing the final plans, Geotech Consultants, Inc. should be retained to provide geotechnical consultation, testing, and observation services during construction. This is to confirm that subsurface conditions are consistent with those indicated by our exploration, to evaluate whether earthwork and foundation construction activities comply with the general intent of the recommendations presented in this report, and to provide suggestions for design changes in the event subsurface conditions differ from those anticipated prior to the start of construction. However, our work would not include the supervision or direction of the actual work of the contractor and its employees or agents. Also, job and site safety, and dimensional measurements, will be the responsibility of the contractor. During the construction phase, we will provide geotechnical GEOTECH CONSULTANTS, INC. Johnston Design Group October 19, 2017 RWEIVED ,Punt A l CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT observation and testing services when requested by you or your representatives. Please be aware that we can only document site work we actually observe. It is still the responsibility of your contractor or on -site construction team to verify that our recommendations are being followed, whether we are present at the site or not. We trust that this letter meets your immediate needs for the proposed development. Please contact us if we can be of further service. D RW: mw Respectfully submitted, GEOTECH CONSULTANTS, INC. D. Robert Ward, P.E. Principal r3;1 GEOTECH CONSULTANTS, INC. Keck Residence — CG #21125.20 July 2, 2021 Drainage Report Section VRICEIVED Jul 16 2021 Section VII — Other Permits CITY OFE DMONDS DEVELIMSENT DEVELOPMENT SERVICES DEPARTMENT Section VII Summ Narrative This project will not require permits beyond those required from the City of Edmonds. 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Keck Residence — CG #21125.20 July 2, 2021 Drainage Report Section VIRFE EIVED Jul 16 2021 CITY OF EDMONDS Section VIII — Operation and Maintenance Manual DEVELDOPMENT EPARTMENRVICES Section VIII Summary: Narrative The Operation and Maintenance Manual is a standalone document that will be given to the homeowner following the construction of the 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 homeowner. Upon request by the City of Edmonds, 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. 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Keck Residence — CG #21125.20 Drainage Report July 2, 2021 Section VIRECEIVED Keck Residence 15722 72Ind Ave W Edmonds, WA 98026 OPERATION AND MAINTENANCE MANUAL Date: July 2021 C IMM, ENGINEERING Jul 16 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com A PORTION SE 1 /4 OF THE SE 1 /4, HOUSE RIDGE rUUNU VLL3AN AND C I "LDC 48761" Ju 6 \ TOWNSHIP 27 NORTH, RANGE 6 EAST, W.M. \ I TEL-\\ EL = .6 D ELO9 fg1ENT SE \ \ I I \ DER RTMENT v v 10 UTILITY EASEMENT I I (AT. NO. 201603295002) \ N I V \ e 10' �It�T_Y EASEMENT OIL AMENDMENT PER BMP T5.1 OF THE SW MWW \ CB - �p (AF. NO. 2-01,603295002) n EICB \ 2 3 RIM:241.0 \ z 7 `AA \ ENTRY MONUMENT I IE (6' S): 237.0 `^� M 6" TRAFFIC RATED C3. C3. IE I6"NE): 2370 C3 �M TRENCH DRAIN \ EASEMENT (AF. NO, IE(6" SEE W). 236.9 T PAVEME T - - RIM:(VARIES, \ E IS" SE): 237.0\ SECTION OD - \SPOTELEVATIONS)e \\ 201512240192) I 6 ' BS L FIR TO OF 65 za4.3s \"I--� 246.2 �C w): za3sz c3. \\ EEP SLOPE DEN FED I - v RAI CHAIN AND SPLASH \ ROCK WIN PER ARCH N HIS S RVEY it/T 241.50 _ _... ..... _ ♦ - A 4 6 ATOP 246. 2 RIM: 29.0 \J , 239.5 \ \ \ I M S' 7 TOE 24.0ssM cM \ > \ IE I6'E): 226.0 32• 238.0 \ \ \ IE (6 W):226.23 0 231.0 \ 0.6 \ \ IE ROOF DRAIN INTO ` \ 2 YARD DRAIN ,2 s EI 6 5)7242.1 M I Fel \ DECK ABOVE 89 p \ 202°A ( IE I6 W): 242.06! 24145 \ \ _TOP: 247.0 sir �M TIE IN O EXISTING \ \ / SSt'-6„ \3 �. M -TOE 241.5 STOR STUB, \ / \ m PVC@55° 1 ?°� T P 246.0 \ , CEE 241. �, ss�w \ \\ \\ OOFAND 6 4\ 2SSCO a \ L W R LEVEL FO\ NG IN C3, \ ENTRY'`230.65 n - - _ \ <• PT \ 12' YARD DRAIN 229.0 \ RIM: 240.0 240.92 \ \ - SS TUB ' `O ° SEE DETAIL 4/C3.2 IE (6 N) 237.9 241.22 \ \ - ti� UNDERSLAB IE 6 SE): 238.0 a \ 240.94 12"YARD DRAIN \ e S I \ \ (IE) N250.29' so / DRAINAGE PLAN, TYP \ RIM: 245., \ \ Via\\ PROPOSED RESIDENCE \ \ P 0 IE (6"N): 243.0 \� -®-\ICY \ pJ'C v \ \ 1 FFE: 241.06 TT\/pOP Zq4/qS.D \ \p02 d TOP: 245. \ \ 15 LF-6"PVC a +• O:244.0 ` Ha _� INSTALLIUT MATTAND ULCH \ -- 228.50 ° a ° ° R \$ �)� 21 V /I WITHIN AC ESS EASEME T \ r T G \' / V WP FRONT ENTRY: 241.02 t �I� 220,' G \ \ \ 241.06 6" TRAR CRATED 2 1. 1 \ GARAGE\ K TT N T _ \ / TRENCH DRAIN \ \ ENTRY: 241.15 YYY ----- \ RIM: (VARIES, SEE SPOT \ t ZO 9SOO2) 1 TYPE C6� \ 8 ELEVATIONS) TIEWALLFOOTING i N2'15 °E RIM' 221 / IE 6" N 239.5 DRAIN TO BUILDING / P LOWER LEVEL C3, ( )' SD O.00• ENTRY: 230.65 FO TING DRAIN C3. C3. IE (6'NE): 2180 \ RGE \ TIE CUT FF DRAIN TO F OTING DRAI -- - IE (4 E): 218.5 BOULD (EXTEND FROM BLDG FTG DRAIN) IE IS NW):2180, \ / S °' 230.1 0F F 1 - - 01 .0 MIN TIE FOOTING6RA1 / / 1 S• •P\ yr F �"\` 1 �\�� /INTOATCH BASIN \ / \ / "j _S 230.61 </ '1/R \ - EL z2a.o FOU D REB ROOF OVERHANG LIN / / 229.0 / \ - V w R-• CUTOFF DRAIN(HANDDIG� AND GAP L -- ONLY IN ROOT ZONES) "LDG #48761 / 7 TOP: 229.5 TOE: 228.5 _ TOP: 234.5 ---" TOE: 232.0 -- LOWER DkCK _ SLOPE ALL UNCOVERED I HARD SURFACE AWAY _ _ L - 369.95' FROM BLDG \ \� �8_80' _ BUILDING SET BACK LINE \27�.0\5' APPPOYINAATP IOr4TIONI GRADING AND DRAINAGE PLAN 1 SCALE: 1" = 10' GRADING AND DRAINAGE PLAN NOTES: 10 0 5 10 20 GRADING QUANTITIES 1. THIS SITE IS DESIGNATED AS A STEEP SLOPE CRITICAL AREA. TOTAL EXCAVATION(CUT)- 150 CU YDS TOTAL 2. ALL DISTURBED AREAS ON AND OFF -SITE SHALL BE COMPOST -AMENDED PER THE REQUIREMENTS OF BMP EMBANKMENT(FILL)- 760 CU YDS T5.13 N THE STORMWATER MANUAL VOLUME V, CHAPTER 5. TOTAL 910 CU YDS 3. TOP AND TOE REFER TO FINISHED GRADE AT THE TOP AND BOTTOM OF THE WALLS, RESPECTIVELY. THE QUANTITIES SHOWN ABOVE ARE FOR THE PERMIT PROCESS ONLY. THESE VALUES ARE APPROXIMATE. DO NOT USE FOR 4. A MINIMUM OF T HORIZONTAL SEPARATION AND 1' VERTICAL SEPARATION IS REQUIRED BETWEEN DRY BIDDING, PAYMENT, OR ESTIMATING PURPOSES. UTILITIES (POWER, GAS, PHONE, CABLE, ETC) AND SEWER WATER AND STORM, AND A MINIMUM OF 5' HORIZONTAL SEPARATION AND V VERTICAL SEPARATION FROM ANY CITY -OWNED LINES. S. AMINIMUM OF 2'OF COVER IS REQUIRED FOR ALL PIPES LOCATED UNDER DRIVABLE SURFACESAND 11OF COVER UNDER LANDSCAPE SURFACES. 6. PRIOR TO PLACING ANY SURFACING MATERIAL ON THE DRIVEWAY, IT WILL BE THE RESPONSIBILITY OF THE DEVELOPER/CONTRACTOR TO PROVIDE DENSITY TEST REPORTS CERTIFIED BY A PROFESSIONAL ENGINEER REQUIRED IN THE STATE OF WASHINGTON. 7. NEW/REPLACED IMPERVIOUS SURFACE (INCLUDE PRIVATE DRIVE): 7,2635F - NEW BUILDING: 4,861 SF ROOF AREA (INCLUDING OVERHANGS). RUNOFF ROUTED TO STORM DRAIN STUB THOUGH ROOF DRAINS. - NEW DRIVEWAY: 1,381 SF. RUNOFF ROUTED TO STORM DRAIN STUB THROUGH TRENCH DRAIN. RUNOFF WILL FLOW INTO THE GUTTER AND PUBLIC STORM SYSTEM. -NEW WALKWAYS: 844 SF. RUNOFF ROUTED TO STORM DRAIN STUB THROUGH CATCH BASIN. APPROVED FOR CONSTRUCTION CITY OF EDMONDS DATE: _ BY: CITY ENGINEERING DIVISION e cm ENGINEERING 250 4TH AVE. S., SUITE 200 EDMONDS, WASHINGTON 98020 PHONE (425) 778-8500 FAX (425) 778-5536 01/02/2021 1 DESIGN: BJL DRAWN: ATD CHECK: JPU JOB NO: 21125.20 DATE: 07/02/2021 Lf.I^.1 V a z � J O H 1..1 U Q w 0 3::a p 0 Z Z La Q z Q Z Y N 0 Q Q Y-Ld J 0C SHEET C3.1 8. THE MAXIMUM DRIVEWAY GRADE IS 14%. Keck Residence — CG #21125.20 Drainage Report July 2, 2021 Section VIRFECEIVED Operation and Maintenance Manual Jul 16 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT This Operation and Maintenance Manual has been created for Keck Residence, a new single-family residence on a 0.72 ac lot located at 15722 72nd Ave W, Edmonds, WA 98026. The proposed stormwater management system consists of conveyance pipes and catch basins that collect roof and yard runoff and route it to a downstream conveyance system within the access and utility easement recorded with the existing short plat. Included in this Operation and Maintenance Manual is an 11" x 17" grading and drainage plan sheet showing the locations of the infiltration system and catch basins. 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. After construction, responsibility will pass to the homeowner. Included in this manual are maintenance sheets taken from the 2014 Stormwater Management Manual for Western Washington. Maintenance sheets are included for the following facilities/activities: Catch Basins: Concrete structures with steel grates that collect stormwater runoff from the site and act as junctions for storm conveyance pipes. See "No. 5" 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, (b) Should any defect become apparent between inspections. 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com RECEIVED Jul 16 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT 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 RECEIVED Jul 16 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT 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. Volume V — Runoff Treatment BMPs — December 2014 4-39 RECEIVED Jul 16 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT 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 RECEIVED Jul 16 2021 CITY OF EDMONDS DEVELOPMENT SERVICES release toxic pesticides such as pentachlorophenol, carbamates, and DEPARTMENT 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 RECEIVED Jul 16 2021 CITY OF EDMONDS DEVELOPMENT SERVICES Applicable Operational BMPs for the Use of Pesticides: DEPARTMENT • Develop and implement an IPM (See section on IPM in ,4pplicable Operational BMPs for Ve,,etation Manyems) 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 RECEIVED Jul 16 2021 CITY OF EDMONDS DEVELOPMENT SERVICES • Flag all sensitive areas including wells, creeks, and wetlands prior t(YEPARTMENT spraying. • Post notices and delineate the spray area prior to the application, as required by the local jurisdiction or by Ecology. Conduct spray applications during weather conditions as specified in the label direction and applicable local and state regulations. Do not apply during rain or immediately before expected rain. Recommended Additional Operational BMPs for the use of pesticides: Consider alternatives to the use of pesticides such as covering or harvesting weeds, substitute vegetative growth, and manual weed control/moss removal. • Consider the use of soil amendments, such as compost, that are known to control some common diseases in plants, such as Pythium root rot, ashy stem blight, and parasitic nematodes. The following are three possible mechanisms for disease control by compost addition (USEPA Publication 530-F-9-044): 1. Successful competition for nutrients by antibiotic production; 2. Successful predation against pathogens by beneficial microorganism; and 3. Activation of disease -resistant genes in plants by composts. Installing an amended soil/landscape system can preserve both the plant system and the soil system more effectively. This type of approach provides a soil/landscape system with adequate depth, permeability, and organic matter to sustain itself and continue working as an effective stormwater infiltration system and a sustainable nutrient cycle. • Once a pesticide is applied, evaluate its effectiveness for possible improvement. Records should be kept showing the effectiveness of the pesticides considered. Develop an annual evaluation procedure including a review of the effectiveness of pesticide applications, impact on buffers and sensitive areas (including potable wells), public concerns, and recent toxicological information on pesticides used/proposed for use. If individual or public potable wells are located in the proximity of commercial pesticide applications, contact the regional Ecology hydrogeologist to determine if additional pesticide application control measures are necessary. • Rinseate from equipment cleaning and/or triple -rinsing of pesticide containers should be used as product or recycled into product. For more information, contact the Washington State University (WSU) Extension Home -Assist Program, (253) 445-4556, or Bio-Integral Resource Center (BIRC), P.O. Box 7414, Berkeley, CA.94707, or EPA to Volume IV - Source Control BMPs — December 2014 2-24 RECEIVED Jul 16 2021 CITY OF EDMONDS DEVELOPMENT SERVICES obtain a publication entitled "Suspended, Canceled, and Restricted DEPARTMENT 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 RECEIVED Jul 16 2021 CITY OF EDMONDS DEVELOPMENT SERVICES Mowing is a stress -creating activity for turfgrass. Grass decreases it§EPARTMENT 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 RECEIVED Jul 16 2021 CITY OF EDMONDS DEVELOPMENT SERVICES • Properly trained persons should apply all fertilizers. Apply no fertiliMtRTMENT at commercial and industrial facilities, to grass swales, filter strips, or buffer areas that drain to sensitive water bodies unless approved by the local jurisdiction. Integrated Pest Management An IPM program might consist of the following steps: Step 1: Correctly identify problem pests and understand their life cycle Step 2: Establish tolerance thresholds for pests. Step 3: Monitor to detect and prevent pest problems. Step 4: Modify the maintenance program to promote healthy plants and discourage pests. Step 5: Use cultural, physical, mechanical or biological controls first if pests exceed the tolerance thresholds. Step 6: Evaluate and record the effectiveness of the control and modify maintenance practices to support lawn or landscape recovery and prevent recurrence. For an elaboration of these steps, refer to Appendix IV-F. Volume IV - Source Control BMPs — December 2014 2-27 Keck Residence — CG #21125.20 Drainage Report July 2, 2021 Section VIRFE €IVED SAMPLE ACTIVITY LOG DATE FACILITY MAINTENANCE PERFORMED RESULTS / NOTES C � ENGINEERING Jul 16 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com