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FG APPROVED STM_RESUB 2-Drainage ReportJune 2021 Owner: Chris Pickering 302 6th Ave S Edmonds, WA 98020 COMPLIES WITH APPLICABLE CITY STORMWATER CODE /20/2021 RESUB 6/29/2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT For Submittal to: DAVIDO CONSULTING GROUP, INC. City of Edmonds CIVIL ■ STRUCTURAL ■ LAND USE Stormwater Site Plans — Rev 2 302 6th Ave S Edmonds CERTIFICATE OF ENGINEER June 2021 The technical material and data contained within this report has been prepared by or under the direction of the following registered professional engineer(s), licensed in accordance with the laws of the State of Washington to practice in the State of Washington. �PMIN °� Sig 69 : nj a' ..fI ns te: �FSSONT� Davido Consulting Group, Inc. Page i 20210608_302 6th Ave S Edmonds_ Drainage ReportRev 2 Stormwater Site Plans — Rev 2 302 6th Ave S Edmonds QUICK REFERENCE PROJECT INFORMATION General Project Information June 2021 Project Description Demolition of an existing single-family residence and the construction of 3 townhomes with associated driveway and walkways. Improvements also include drainage, grading, paving, utilities, and landscaping. Project Address 302 6th Ave S Edmonds, WA 98020 Project Size (onsite only) Site = 6,594 SF 0.15 acres Owner/Developer Chris Pickering 302 6th Ave S Edmonds, WA 98020 Consulting Engineer Ben Iddins, PE Davido Consulting Group, Inc. 9706 4th Ave NE, Suite 300 Seattle, WA 98115 Phone: 206 523-0024 ext. 115 Drainage Drainage 2012 DOE Stormwater Management Manual for Western Requirements Washington (as Amended in December 2014) and City of Edmonds amendments in the 2017 Stormwater Code Supplement (the combination of which is hereafter known as "The Stormwater Manual". • Minimum Requirements # 1-9 Tributary Drainage Predeveloped Conditions: Developed Conditions: Area & Land Cover Impervious Surface = 2,715 SF Total Impervious = 4,339 SF Summary (onsite only) Pervious Surface = 3,879 SF Pervious Surface = 2,255 SF Total = 6,594 SF 0.15 Acres Total = 6,594 SF 0.15 Acres Soils Geotechnical analysis was performed by Nelson Geotechnical Associates Inc. and summarized in a report dated March 21, 2019. The geotechnical report states that the site is underlain by native glacial soils. See APPENDIX A for the full geotechnical report. Drainage . Bioretention Planter Boxes w/ Underdrains Improvements • Detention Tank ESC Measures TESC plan required per the Stormwater Manual. TESC measures include storm drain inlet protection, perimeter protection, construction entrance, construction fencing and street cleaning. Davido Consulting Group, Inc. Page ll 20210608_302 6th Ave S Edmonds_ Drainage ReportRev 2 Stormwater Site Plans - Rev 2 302 61h Ave S Edmonds June 2021 TABLE OF CONTENTS 1. Project Overview.......................................................................................................... I 1.1 General Description of Project......................................................................................1 1.2 Predeveloped Site Conditions.......................................................................................2 1.3 Developed Site Conditions............................................................................................2 1.4 Site Area and Size of Improvements.............................................................................3 1.5 Predeveloped Stormwater Runoff Conditions...............................................................3 1.6 Postdeveloped Stormwater Runoff Conditions..............................................................4 1.7 Site Map.......................................................................................................................4 2. Minimum Requirements...............................................................................................4 2.1 Minimum Requirement #1: Preparation of Stormwater Site Plans.................................4 2.2 Minimum Requirement #2: Construction Stormwater Pollution Prevention Plan (SWPPP)......................................................................................................................4 2.3 Minimum Requirement #3: Source Control of Pollution...............................................4 2.4 Minimum Requirement #4: Preservation of Natural Drainage Systems and Outfalls .....5 2.5 Minimum Requirement #5: On -Site Stormwater Management......................................5 2.6 Minimum Requirement #6: Runoff Treatment..............................................................7 2.7 Minimum Requirement #7: Flow Control.....................................................................7 2.8 Minimum Requirement #8: Wetlands Protection...........................................................7 2.9 Minimum Requirement #9: Operation and Maintenance...............................................7 3. Site and Basin Assessment............................................................................................8 3.1 Offsite Analysis............................................................................................................8 3.2 Sub -basin Description...................................................................................................9 3.3 Soils/Infiltration Rates..................................................................................................9 3.4 Critical Areas and Flood Plain......................................................................................9 3.5 Assessment Summary...................................................................................................9 3.6 Stormwater BMP Sizing.............................................................................................10 4. Construction Stormwater Pollution Prevention Plan (SWPPP)....................................10 5. Permanent Stormwater Control Plan...........................................................................14 5.1 Flow Control..............................................................................................................14 5.2 Water Quality.............................................................................................................14 5.3 Source Control & Operation and Maintenance............................................................14 5.4 Conveyance System Analysis and Design...................................................................14 6. Special Reports and Studies........................................................................................15 6.1 Geotechnical Report...................................................................................................15 7. Other Permits..............................................................................................................15 8. Bonds.........................................................................................................................15 9. Additional Figures......................................................................................................16 Davido Consulting Group, Inc. Page iii 20210608_302 6th Ave S Edmonds -Drainage Report Rev 2 Stormwater Site Plans — Rev 2 302 6th Ave S Edmonds APPENDICES APPENDIX A Geotechnical Report APPENDIX B WWHM Summary APPENDIX C Operation and Maintenance Manual APPENDIX D Declaration of Covenant APPENDIX E Conveyance Calculations APPENDIX F King County Site Improvement Bond Quantity Worksheet June 2021 LIST OF TABLES TABLE 1 Project Site Area and Size of Improvements.........................................................3 TABLE 2 Bioretention Planter Box Sizing Table................................................................10 TABLE 3 Proposed ESC Measures.....................................................................................13 LIST OF FIGURES FIGURE1 Site Location........................................................................................................ I FIGURE 2 Site Assessment and Summary...........................................................................17 FIGURE 3 Drainage Plan.....................................................................................................18 FIGURE4 TESC Plan..........................................................................................................19 FIGURE 5 Offsite Analysis Photos......................................................................................20 FIGURE 6 Offsite Drainage System Analysis.......................................................................21 FIGURE 7 Developed Conditions Sub -Basin Exhibit...........................................................22 Davido Consulting Group, Inc. Page iv 20210608_302 6th Ave S Edmonds_ Drainage ReportRev 2 Stormwater Site Plans — Rev 2 302 6th Ave S Edmonds June 2021 1. PROJECT OVERVIEW The project involves the demolition of an existing single-family residence and the construction of 3 townhomes with associated driveways and walkways. Improvements also include drainage, paving, utilities, grading, and landscaping. Vehicular access to the site will be via a new driveway off of Maple Street as well as from the alley adjacent to the south property line of the site. The project site is bounded to the north by Maple St, to the west by residential buildings/lots, to the east by Oh Ave S, and to the south by an unnamed alley. The project location is shown in FIGURE 1. The City of Edmonds has adopted the 2012 Washington State Department of Ecology Stormwater Management Manual for the Puget Sound Basin (as Amended in December 2014), City of Edmonds Stormwater Management Code, and the 2017 City of Edmonds Stormwater Addendum; the combination of which is herein referred to as the "Stormwater Manual". This report follows the Stormwater Site Plan requirements as stipulated in the Stormwater Manual. 6y19=Eel NT%9[0lhill c_ s Ins S Herbc is -PUt� - N s an. FIGURE 1 Site Location l 1.1 General Description of Project The project involves the demolition of an existing single-family residence and the construction of 3 townhomes and associated driveways and walkways. Improvements also include drainage, paving, utilities, grading, and landscaping. Frontage improvements along Maple St and 6th Ave S Davido Consulting Group, Inc. Page 1 20210608_302 6th Ave S Edmonds_ Drainage ReportRev 2 Stormwater Site Plans — Rev 2 302 6th Ave S Edmonds June 2021 include new sidewalk, driveway approach, and landscaping strip. Additionally, the alley pavement adjacent to the south property line is being widened to encompass the entire ROW width. 1.2 Predeveloped Site Conditions Existing impervious surfaces on the site include a single-family residence, detached garage, walkways, and a driveway off of Maple St. The remainder of the site is grass which includes four trees. 1.3 Developed Site Conditions The developed site conditions, shown in the project plans submitted under separate cover, will include 3 new townhomes, walkways, and a driveway and parking area on the west side of the site. Drainage for the developed site will include four new bioretention planter boxes with underdrains which will mitigate stormwater runoff from the majority of the roof areas and the upper concrete parking and trash staging area in the SW corner of the site. Additionally, a detention pipe has been sized for all onsite impervious surfaces not routed to bioretention planter box with underdrains as well as offsite stormwater runoff collected in the alley. Overflows from the stormwater BMPs onsite will be routed to a catch basin located in the driveway prior to gravity flowing to the Public Storm main in Maple Street. TABLE 1 summarizes the predeveloped and developed site conditions and land cover. Davido Consulting Group, Inc. Page 2 20210608_302 6th Ave S Edmonds_ Drainage ReportRev 2 Stormwater Site Plans — Rev 2 302 6th Ave S Edmonds June 2021 1.4 Site Area and Size of Improvements The project site is a 0.15 acre parcel located on 6th Ave S. The drainage basin for the project site is the site itself in addition to the adjacent alley to the south and the frontage improvements along 6th Ave S and Maple St. The site area and size of improvements are shown in the project plans and summarized in TABLE 1. See Section 9 of this report for a layout of the proposed improvements. See FIGURE 7 for an exhibit showing the sub -basin areas within the site. TABLE 1 Project Site Area and Size of Improvements Project Site Areas Existing Develo ed SF Acres SF Acres Impervious Areas: Building (Onsite) 1,406 0.03 2,932 0.07 Walkways (Onsite) 432 0.01 210 0.00 Driveways (Onsite) 877 0.02 1,197 0.03 Alley/Driveways/Utility Cuts (ROW) - - 1,116 0.03 Sidewalks (ROW) - - 1,298 0.03 Total Impervious Surface (Onsite Only): 2,715 0.06 4,339 0.10 Total Impervious Surface (Onsite+ROW): - - 6,753 0.16 Total New/Replaced Impervious Surface: - - 6,753 0.16 Total Pollution Generating Impervious Surface: 877 0.02 2,313 0.05 Total New/Replaced Pollution Generating Impervious Surface: - - 2,313 0.05 Pervious Areas: Grass/Trees/Landscaping (Onsite) 3,879 0.09 2,255 0.05 Grass/Trees/Landscaping (ROW) - - 410 0.01 Total Pervious Surface 3,879 0.09 2,665 0.06 Total Project Site Area (Onsite Only) 6,594 0.15 6,594 0.15 Total Project Site Area (Onsite + ROW) 9,418 0.22 9,418 0.22 The existing areas in TABLE 1 were determined by area measurements in AutoCAD from a topographic survey dated December 19, 2018. As shown in TABLE 1, the developed site impervious surfaces total 6,753 SF consisting of the new building, driveways, alley pavement, walkways and frontage improvements. The areas in TABLE 1 represent the site coverage in the basin draining to the proposed bioretention planter boxes, detention tank, and/or City's storm system within Maple Street. 1.5 Predeveloped Stormwater Runoff Conditions Stormwater runoff from the existing single-family residence is collected in a gutter and downspout system and is likely conveyed to the City's storm system in 6th Ave S. All other stormwater runoff generated on the site either infiltrates onsite or sheet flows to the City's storm system in 6th Ave S or Maple Street. Davido Consulting Group, Inc. Page 3 20210608_302 6th Ave S Edmonds_ Drainage ReportRev 2 Stormwater Site Plans — Rev 2 302 6th Ave S Edmonds June 2021 1.6 Postdeveloped Stormwater Runoff Conditions The majority of stormwater from the proposed building roof will be collected in a gutter and downspout system and conveyed to four proposed bioretention planter boxes with underdrains. Stormwater generated from a portion of the western roof area could not be gravity fed to a bioretention planter box and therefore runoff from that area, all other hard surfaces on the site not being routed to a bioretention planter box, and overflows from the bioretention planter boxes with underdrains, will be routed to a 28 LF 36" diameter detention tank with associated flow control tee located on the north side of the site. Additionally, a trench drain will be installed at the bottom of the alley adjacent to the south property line to collect flow from the alley which will also be routed to the detention tank. All stormwater discharging from the detention tank will be routed via gravity to the public storm system in Maple Street. See Sections 2.5 and 5 for additional information on the proposed stormwater system and BMPs. See FIGURE 7 for an exhibit showing the sub -basin areas within the site. 1.7 Site Map Plans showing the proposed improvements have been attached in Section 9 of this report and contain all requirements set forth in the Stormwater Manual. 2. MINIMUM REQUIREMENTS Since the project proposes greater than 5,000 SF of new plus replaced hard surfaces it is considered a Category 2 project site and is therefore subject to all Minimum Requirements listed in the Stormwater Manual (MR 1-9). The project meets the Stormwater Manual Minimum Requirements as summarized in the following sections. 2.1 Minimum Requirement #1: Preparation of Stormwater Site Plans The Stormwater Site Plan was prepared in accordance with Volume 1 Chapter 3 of the SWMMWW and Section 5.1 of the City of Edmonds's Addendum to the SWMMWW and includes the minimum requirements applicable to the subject site based on thresholds of new and replaced site impervious coverage. 2.2 Minimum Requirement #2: Construction Stormwater Pollution Prevention Plan (SWPPP) The SWPPP was prepared in accordance with Volume 1 Chapter 2 Section 2.5.2 of the Stormwater Manual and is described in Section 0. The Temporary Erosion and Sediment Control Plan (TESC Plan) can be seen in Section 9 of this report and serves as a guide for the contractor to implement a final TESC Plan. As the site disturbance is less than one acre, a General Permit through the DOE is not required. 2.3 Minimum Requirement #3: Source Control of Pollution The proposed bioretention planter boxes, detention tank, Type I and II catch basins and spill control elbows serve as source control of pollution on the project site. In order to control pollutants, proper maintenance and cleaning of debris, sediments, and oil from stormwater collection and conveyance systems is required per the operation and maintenance recommendations found in Volume 5 Section 4.6 of the Stormwater Manual in addition to the Davido Consulting Group, Inc. Page 4 20210608_302 6th Ave S Edmonds_ Drainage ReportRev 2 Stormwater Site Plans — Rev 2 302 6th Ave S Edmonds June 2021 BMPs in Volume IV Section 2.2. See APPENDIX C for operation and maintenance requirements pertaining to the project. 2.4 Minimum Requirement #4: Preservation of Natural Drainage Systems and Outfalls The proposed drainage system consisting of a detention tank and bioretention planter boxes will emulate the natural pre -developed conditions of the site (i.e., forested conditions) as much as possible as stormwater will be absorbed onsite or will enter the City's storm system in Maple Street and eventually drain to Shell Creek, thus maintaining the natural drainage course from the site. 2.5 Minimum Requirement #5: On -Site Stormwater Management According to the City's Stormwater Code (Ch 18.30), Category 2 projects that discharge directly or indirectly to the City's MS4 and are required to comply with Minimum Requirements No. 1 through No. 9 shall either: a. Use On -site Stormwater Management BMPs from List No.2 for all new plus replaced hard surfaces and land disturbed (See ECDC 18.30.060.D.5.e); or b. Demonstrate compliance with the LID Performance Standard (See ECDC 18.30.060.D.5.c). This project proposes to meet MR #5 through the use of On -site Stormwater BMPs from List No.2, which requires roofs and other hard surfaces to evaluate different lists of BMPs in the order they are presented in the City's Stormwater Code. BMPs were evaluated and/or chosen in the following order: Law and Landscaped Areas: • Lawn and landscaped areas will meet the Post -Construction Soil Quality and Depth in accordance with BMP T5.13 in Chapter 5 of Volume V of the SWMMWW. Roofs: • Full Dispersion in accordance with BMP T5.30 in Chapter 5 of Volume V of the SWMMWW. This BMP is not feasible as the minimum required vegetated flowpath length is not available onsite. • Downspout Full Infiltration in accordance with BMP T5. l0A in Chapter 5 of Volume V of the SWMMWW. This BMP is not feasible as the measured infiltration rate found at the site was 0 in/hr (see Section 3.3 for additional information on the site soils). • Bioretention (See Chapter 7 of Volume V of the SWMMWW) facilities that have a minimum horizontally projected surface area below the overflow which is at least 5 percent of the total surface area draining to it. Bioretention planter boxes with underdrains were designed in accordance with BMP T5.1413 in Chapter 5 of Volume V of the SWMMWW and the bioretention planter boxes have been sized so that the horizontally projected surface area below the overflow is at least 5% of the roof area draining to it. All but 857 SF of roof area will be routed to the four bioretention planter boxes. The 857 SF of roof area not mitigated by a bioretention planter box could not be routed via gravity to a planter without making it very deep in which case it would not receive the proper sunlight necessary for it to function as intended. See Section 3.6 for the sizing of each bioretention planter box with underdrain. Davido Consulting Group, Inc. Page 5 20210608_302 6th Ave S Edmonds_ Drainage ReportRev 2 Stormwater Site Plans — Rev 2 302 6th Ave S Edmonds June 2021 • Downspout Dispersion Systems in accordance with BMP T5.IOB in Chapter 5 of Volume V of the SWMMWW. This BMP is not feasible as the minimum required vegetated flowpath length is not available onsite. • Perforated Stub -out Connections in accordance with BMP T5.1OC in Chapter 5 of Volume V of the SWMMWW. The small amount of roof area not served by a bioretention planter cannot be routed to an area on the site appropriate for a perforated stub -out connection (i.e. a non -paved area) that also meets horizontal setbacks from the building and property lines. • Detention vaults or pipes in accordance with the Edmonds Stormwater Addendum. A Detention Pipe has been sized in accordance with the Edmonds Stormwater Addendum to handle the 857 SF of roof not mitigated by a bioretention planter box as well as other hard surfaces (see section below). Other Hard Surfaces: • Full Dispersion in accordance with BMP T5.30 in Chapter 5 of Volume V of the SWMMWW. This BMP is not feasible as the minimum required vegetated flowpath length is not available onsite. • Permeable pavement in accordance with BMP T5.15 in Chapter 5 of Volume V of SWMMWW. Permeable pavement is not feasible since the measured infiltration rate at the site was 0 in/hr. • Bioretention (See Chapter 7 of Volume V of the SWMMWW) facilities that have a minimum horizontally projected surface area below the overflow which is at least 5 percent of the total surface area draining to it. Bioretention planter boxes were designed in accordance with BMP T5.1413 in Chapter 5 of Volume V of the SWMMWW. The upper parking area off of the alley (425 SF) will be routed to bioretention planter #4. See Section 3.6 for the sizing of each bioretention planter box with underdrain. • Sheet Flow Dispersion in accordance with BMP T5.12, or Concentrated Flow Dispersion in accordance with BMP T5.11 in Chapter 5 of Volume V of the SWMMWW. This BMP is not feasible as the minimum required vegetated flowpath length is not available onsite. • Detention vaults or pipes in accordance with the Edmonds Stormwater Addendum. A detention pipe has been sized in accordance with the Edmonds Stormwater Addendum to handle all "other hard surfaces" on the site besides 425 SF of upper parking area that will be routed to a bioretention planter box with underdrain. This include the driveway, stairs and entrances along the east side of the building, and site walls that will drain to the driveway, totaling 1,147 SF. In addition, the detention pipe has been sized for the 857 SF of roof not mitigated by a bioretention planter box, as described above. Lastly, the detention pipe has been sized to receive stormwater runoff from the alley to the south of the site (a trench drain will collect flow at the bottom of the alley and stormwater will be routed onsite to the detention facility). Runoff from the alley collected by the trench drain totals 1,420 SF. Therefore, the total new hard surface area routed to the detention facility is 3,424 SF. The detention pipe sizing equation listed in Section 6.3.1 for a 36" pipe is L = 0.008*A. Therefore, the required detention pipe length is 0.008*3,424 = 27.4'. The pipe length was increased to 28' as shown in the Civil Plans. Davido Consulting Group, Inc. Page 6 20210608_302 6th Ave S Edmonds_ Drainage ReportRev 2 Stormwater Site Plans — Rev 2 302 6th Ave S Edmonds June 2021 Since the project site is a corner lot there are frontage improvements required on two street frontages as well as widening the alley to a full 15' width. The total new and replaced impervious surfaces for the project, including improvements in the ROW, is 6,753 SF, as shown in TABLE 1. The four non -infiltrating bioretention planter boxes with underdrains and the detention facility will receive runoff from a total of 5,924 SF. That leaves 829 SF of new and replaced impervious surfaces unmitigated by a BMP. However, all of that area is street replacement or sidewalk installation that will drain to the street. There is no way to collect additional runoff from the ROW and route it to the detention facility onsite without collecting stormwater from the street flowline which will be a large tributary area. Since the unmitigated hard surface area is less than 1,000 SF, Minimum Requirement #5 is satisfied. 2.6 Minimum Requirement #6: Runoff Treatment Since this project is proposing less than 5,000 SF (2,313 SF is proposed) of pollution generating hard surface (PGHS) it is exempt from runoff treatment requirements. 2.7 Minimum Requirement #7: Flow Control This project is exempt from Minimum Requirement #7 because of the following: • the total effective impervious surface in the threshold discharge area is less than 10,000 SF (6,594 SF proposed); and • the project will not convert 0.75 acres or more of vegetation to lawn or landscape, or convert 2.5 acres or more of native vegetation to pasture in a threshold discharge area; and • that through a combination of hard surfaces and converted vegetation areas cause less than a 0.10 cubic feet per second (cfs) increase or greater in the 100-year flow frequency from a threshold discharge area as estimated using the Western Washington Hydrology Model or other approved model and one -hour time steps (or a 0.15 cfs increase or greater using 15-minute time steps). TABLE 1 shows that this project is under the area thresholds listed above and the WWHM2012 model report, which is included in APPENDIX B, shows that the increase in the 100-year flow frequency using 15-minute timesteps is less than 0.15 cfs (0.136345 cfs increase). Therefore, this project is exempt from flow control. 2.8 Minimum Requirement #8: Wetlands Protection The site is tributary to a wetland, but is below the thresholds for new plus replaced impervious and land disturbance. Therefore, because MR#7 is not triggered, MR #8 is also not triggered, making the wetlands protections standard not applicable. 2.9 Minimum Requirement #9: Operation and Maintenance An operation and maintenance manual consistent with Volume V of the Stormwater Manual has been provided in APPENDIX C. Davido Consulting Group, Inc. Page 7 20210608_302 6th Ave S Edmonds_ Drainage ReportRev 2 Stormwater Site Plans — Rev 2 302 6th Ave S Edmonds 3. SITE AND BASIN ASSESSMENT June 2021 The proposed project aims to preserve natural resources and maintain or restore natural hydrologic conditions on the site. The existing site conditions are summarized in the following sections. Existing Site Conditions: A. Topography The general topography of the site slopes north east at an approximate average slope of 3 %. B. Existing ground cover The existing site contains 2,715 SF of impervious surface, 3,879 SF of pervious surface, and 877 SF of pollution generating impervious surface (PGIS). C. Natural features of the parcel The pervious areas on the existing site consist of trees, grass, and shrubs. D. Offsite drainage to the property Very little, if any, offsite stormwater enters the site from the neighboring parcels, Maple St, Oh Ave S, or the paved alley, which surround the site. E. Environmentally sensitive areas on or down gradient of the property N/A. No environmentally sensitive areas exist on or immediately adjacent to the property. F. Drains, channels, and swales, within the project site and immediately adjacent An existing roof downspout system associated with the buildings onsite exists and likely routes stormwater to the City's storm system in Maple Street, although the connection location is unknown. G. Points of exit for existing drainage from the property Existing stormwater runoff from the site is likely routed north to the existing storm system in Maple St. H. Known historical drainage problems There are no known historical drainage problems associated with the site. I. Existing Structures/Improvements Existing impervious surfaces on the site include a 1,406 SF of buildings (single family residence and garage) and 877 SF of driveway, and 432 SF of concrete walkway. J. New Structures Improvements Three townhouses totaling 2,929 SF are proposed. K. Future Structures/Improvements Planned No future structures or improvements are planned for the site at this time. L. Remaining Undisturbed Land: The entire site will be cleared for the proposed development, thus leaving no undisturbed land on the site. 3.1 Offsite Analysis An offsite analysis is required for this project since the project proposes to discharge stormwater offsite to the City's storm system in Maple St. An offsite analysis was conducted on June 27, 2016. Prior to inspecting the upstream and downstream drainage system, research on the drainage system was conducted using available online GIS mapping. It is clear from the online Davido Consulting Group, Inc. Page 8 20210608_302 6th Ave S Edmonds_ Drainage ReportRev 2 Stormwater Site Plans — Rev 2 302 6th Ave S Edmonds June 2021 GIS mapping as well as the visual inspection of the drainage system that runoff from the site will eventually discharge to Shell Creek. The downstream drainage system was followed from the discharge point in Maple St to the discharge location to Shellabarger Creek, which is approximately 0.5 miles downstream. The project is proposing to discharge to the existing public storm system in Maple St (MS4). The drainage system in Maple St flows westerly and consists of 12" concrete pipe connecting a series of Type I and Type II catch basins until the system reaches 5th Ave S. The drainage system then flows northerly down 5th Ave S until it reaches Dayton St, where it turns westerly and flows to 3rd Ave S. It then flows southemly and finally discharges into Shellabarger Creek. There was no visual indication of conveyance system capacity problems, localized flooding, erosion impacts, or violations of surface water quality standards. Many of the catch basin lids were either locked or were within heavily trafficked areas and therefore the lids of these catch basins could not be pulled, and the condition of the system could not be visually inspected. However, there was no evidence of any damage to the drainage system. See FIGURE 5 and FIGURE 6 for offsite analysis photos and table. 3.2 Sub -basin Description Offsite flow from the alley south of the site will be captured in a trench drain and conveyed onsite to the proposed detention tank. All drainage on the site will be collected and routed to bioretention planter boxes and/or the detention facility onsite before discharging via gravity to the storm system within Maple St. Runoff from new sidewalks and replaced roadway surfaces will be collected within existing drainage infrastructure within Maple St and 6th Ave S and will enter the public storm system within the two streets. 3.3 Soils/Infiltration Rates A geotechnical analysis was performed by Nelson Geotechnical Associates Inc. and summarized in a report dated March 21, 2019. Nelson Geotechnical Associates excavated four test pits using a mini-trackhoe to depths ranging from 7.6 to 9.0 feet below the existing ground surface. In general, Nelson Geotechnical Associates determined that the site is underlain by glacial till soils. Groundwater seepage was encountered at depths from 7.0-8.0 feet below the existing surface and was interpreted as perched groundwater. Native soils on site were deemed not conductive for stormwater infiltration. See APPENDIX A for the full geotechnical report. 3.4 Critical Areas and Flood Plain There are no known critical areas on or in the immediate vicinity of the site. 3.5 Assessment Summary The area of study for this project was the project site itself, Maple St, 6th Ave S, and the paved alley south of the site. While the proposed project adds more impervious surface to the site than the existing conditions, runoff from the majority of the impervious surfaces will be routed to a BMP or will enter the city's existing stormwater system (see Section 2.5). Davido Consulting Group, Inc. Page 9 20210608_302 6th Ave S Edmonds_ Drainage ReportRev 2 Stormwater Site Plans — Rev 2 302 6th Ave S Edmonds June 2021 3.6 Stormwater BMP Sizing Bioretention planter boxes with underdrains were selected to manage stormwater runoff from the majority of the roof areas and the upper concrete parking area. The sizing factor used to determine the minimum horizontally projected surface area below the overflow for each bioretention planter box is 0.05 (5% of the contributing area) as required by the Stormwater Manual. The table below shows each planter size (internal horizontally projected surface area below the overflow) and the amount of roof area draining to each planter. TABLE 2 Bioretention Planter Box Sizing Table Bioretention Planter Box (Bioplanter) Number Area Tributary Minimum Bioretention Area Required Bioplanter Area Provided (SF) Bioplanter Dimensions BPI 193 9.65 10.0 5.0'L x 2.0'W BP2 449 22.45 26.0 13.0'L x 2.0'W BP3 519 25.95 31.9 14.5'L x 2.2'W BP4 1,339 66.95 67.2 16.0'L x 4.2'W See Section 2.5 for additional information on the BMP selection and for sizing of the detention tank. 4. CONSTRUCTION STORMWATER POLLUTION PREVENTION PLAN (SWPPP) The SWPPP was prepared in accordance with the Stormwater Manual. A Temporary Erosion and Sediment Control Plan is required per the Stormwater Manual. Erosion and sediment control (ESC) measures were designed for the project and shown on the TESC plan in Section 9 of this report. Both the SWPPP and TESC Plan serve as guides as the contractor is required to design a working TESC plan for the site. Refer to the TESC plan and TABLE 3 in this report for TESC measures. Element 1: Preserve Vegetation/Mark Clearing Limits BMPs used: • BMP C 103: High Visibility Fence • BMP C233: Silt Fence High visibility fence shall be placed around the site to mark the clearing limits and silt fence will be placed around the low points of the perimeter of the site (as shown on the TESC Plan in FIGURE 4). Element 2: Establish Construction Access BMPs used: • BMP C 105: Stabilize Construction Entrance/Exit The project site will have one construction access connecting to Maple Street. The contractor shall install a temporary construction entrance made from quarry spalls. All streets surrounding the site, including the alley, will be swept daily, or as needed, to remove sediment tracked from the project site. Element 3: Control Flow Rates BMPs used: Davido Consulting Group, Inc. Page 10 20210608_302 6th Ave S Edmonds_ Drainage ReportRev 2 Stormwater Site Plans — Rev 2 302 6th Ave S Edmonds • BMP C235: Wattles June 2021 If necessary, the contractor will implement compost socks and/or straw wattles to control flow rates and disperse stormwater. Element 4: Install Sediment Controls BMPs used: • BMP C233: Silt Fence • BMP C235: Wattles Silt fencing or straw wattles will be placed along the low points of the perimeter of the construction site to prevent sediment from escaping downstream of the site. Element 5: Stabilize Soils BMPs used: • BMP C 121: Mulching • BMP C 140: Dust Control Mulch will be used by the contractor whenever soils will be left exposed for a significant amount of time or whenever a rainfall event is anticipated. During summer months water will be sprinkled on the site as needed to minimize the amount of dust coming off of the site. Element 6: Protect Slopes BMPs used: • BMP C 121 Mulching Mulch will be added to soils on significant slopes to provide temporary protection from erosion. Element 7: Protect Drain Inlets BMPs used: • BMP C220: Storm Drain Inlet Protection Temporary catch basin inlet protection on all existing catch basins on and adjacent to the site as well as proposed catch basins will be implemented to prevent sediment from entering the drainage system. Element 8: Stabilize Channels and Outlets BMPs used: • BMP C207: Check Dams While there are no existing channels on the site, check dams will be used as necessary to control flowrates, trap sediment, and protect against erosion during construction. Element 9: Control Pollutants BMPs used: • BMP C 153: Material Delivery, Storage and Containment • BMP C 154: Concrete Washout Area A material delivery, storage and containment area shall be designated by the contractor and located away from traffic and near the construction entrance. An onsite concrete washout area for any concrete mixing shall be designated by the contractor as well. Element 10: Control De -Watering BMPs used: • Water Bars De -watering should not be an issue on this site as the groundwater table is not known to be near the surface. However, the contractor shall apply water bars during construction as needed. Element 11: Maintain BMPs BMPs used: Davido Consulting Group, Inc. Page 11 20210608_302 6th Ave S Edmonds_ Drainage ReportRev 2 Stormwater Site Plans — Rev 2 302 6th Ave S Edmonds • BMP C150: Materials On Hand June 2021 • BMP C 160: Certified Erosion and Sediment Control Lead The contractor shall keep erosion prevention and sediment control materials onsite for regular maintenance and emergency situations. The contractor will be the person in charge of erosion and sediment control for this project. Element 12: Manage the Project BMPs used: • BMP C150: Materials On Hand • BMP C160: Certified Erosion and Sediment Control Lead • BMP C 162: Scheduling The contractor will be in control of erosion and sediment control and will keep erosion prevention and sediment control materials onsite for regular maintenance and emergency situations. The construction project shall be sequenced in an orderly manner to minimize the duration of exposed soil to erosion. Element 13: Protect Low -Impact Development BMPs BMPs used: • BMP C 102: Buffer Zone • BMP C 103: High Visibility Fence • BMP C233: Silt Fence A high visibility fence and silt fence shall be placed around the site where sedimentation is most likely to escape and potentially harm any Low -Impact Development BMPs. Davido Consulting Group, Inc. Page 12 20210608_302 6th Ave S Edmonds_ Drainage ReportRev 2 Stormwater Site Plans — Rev 2 302 6th Ave S Edmonds TABLE 3 Proposed ESC Measures (All ESC Measures Shall Comply with the Stormwater Manual) June 2021 ESC Measure Comment 1 Identify Project Limits Mark by fencing or other means to contain the grubbing and grading activities. 2 Catch Basin Inlet Protection Install catch basin inlet protection in any drainage structures that may collect any stormwater flowing from the construction site. 3 Phase Grubbing and Grading Phase clearing so that only those areas that are actively being worked are uncovered. From October 1 through April 30, no soils shall remain exposed for more than 2 days. From May 1 through September 30, no soils shall remain exposed for more than 7 days. 4 Install Straw Wattles Install straw wattles around disturbed areas where sediment could be transported off - site. Adjust straw wattles as required by site conditions and construction sequencing. 5 Sod/Seed Exposed Areas Cleared areas will be sod/seeded as soon as possible after grading completed (few weeks). 6 Soil Removal Remove excess soil from the site as soon as possible after backfillin . 7 Protect Adjacent Properties Adjacent properties shall be protected from sediment deposition by appropriate use of vegetative buffer strips, sediment barriers or filters, dikes or mulching, or by a combination of these measures and other appropriate BMPs. 8 Street Cleaning Provide for periodic street cleaning to remove any sediment that may have been tracked out. Sediment should be removed by shoveling or sweeping and carefully removed to a suitable disposal area where it will not be re -eroded. 9 Inspect ESC BMPs Inspect all erosion and sediment control BMPs installed regularly, especially after any large storm. Maintenance, including removal and proper disposal of sediment should be done as necessary. Davido Consulting Group, Inc. Page 13 20210608_302 6th Ave S Edmonds_ Drainage ReportRev 2 Stormwater Site Plans — Rev 2 302 6th Ave S Edmonds 5. PERMANENT STORMWATER CONTROL PLAN June 2021 Total areas for new plus replaced impervious surfaces are shown in TABLE 1. The stormwater facility requirement thresholds are as follows: ➢ On -site stormwater management BMPs are required to handle site stormwater runoff. ➢ Flow Control is not required for the site (< 10,000 SF of effective impervious surface) ➢ Water quality treatment is not required for the site (< 5,000 SF new PGIS). The following sections address and summarize site specifics and requirements: 5.1 Flow Control N/A. • the total effective impervious surface in the threshold discharge area will be less than 10,000 SF; and • the project will not convert 0.75 acres or more of vegetation to lawn or landscape, or convert 2.5 acres or more of native vegetation to pasture in a threshold discharge area; and • that through a combination of hard surfaces and converted vegetation areas cause less than a 0.10 cubic feet per second (cfs) increase or greater in the 100-year flow frequency from a threshold discharge area as estimated using the Western Washington Hydrology Model or other approved model using one -hour time steps (or a 0.15 cfs increase or greater using 15-minute time steps). See TABLE 1 for a summary of the project areas and APPENDIX B for the full WWHM Report. 5.2 Water Quality N/A. Since the project is adding less than 5,000 SF of pollution generating impervious surface, it is exempt from water quality requirements. 5.3 Source Control & Operation and Maintenance The bioretention planter boxes with underdrains, detention tank, Type I & II catch basins, and spill control elbows serve as source control of pollution on the project site. In order to control pollutants, proper maintenance and cleaning of debris, sediments, and oil from stormwater collection and conveyance systems is required per the operation and maintenance recommendations found in Volume 5 Section 4.6 of the Stormwater Manual in addition to the BMPs in Volume IV Section 2.2. See APPENDIX C for operation and maintenance requirements pertaining to the project. 5.4 Conveyance System Analysis and Design The proposed onsite conveyance system is comprised of two new Type I catch basins, two Type II catch basins, four areas drains, and four to twelve -inch storm drain pipe. Four -inch roof downspouts will route the majority of roof stormwater runoff to the onsite bioretention planter Davido Consulting Group, Inc. Page 14 20210608_302 6th Ave S Edmonds_ Drainage ReportRev 2 Stormwater Site Plans — Rev 2 302 6th Ave S Edmonds June 2021 boxes (approximately 857 SF of roof area will bypass the bioretention planter boxes and be routed to the detention tank). The upper concrete parking area will also be routed to a bioretention planter box. Any overflow from the bioretention planter boxes, as well as roof runoff bypassing the planters, will be routed to a detention tank with overflow routing to a catch basin in the street flowline prior to gravity flowing to the City's storm system in Maple St. All proposed storm drains onsite have been sized to handle anticipated site runoff from a I00-year storm event. See conveyance calculations located in APPENDIX E. 6. SPECIAL REPORTS AND STUDIES 6.1 Geotechnical Report A geotechnical analysis was performed by Nelson Geotechnical Associates Inc. and summarized in a report dated March 21, 2019. Nelson Geotechnical Associates excavated four test pits using a mini-trackhoe to depths ranging from 7.6 to 9.0 feet below the existing ground surface. In general, native soils on site were deemed not conductive for stormwater infiltration, including low impact infiltration systems such as permeable pavement. See APPENDIX A for the full geotechnical report. 7. OTHER PERMITS Additional permits are not anticipated for the proposed project at this time. 8. BONDS The bond amount for the project has been calculated using the King County Site Improvement Bond Quantity Worksheet. A completed King County Site Improvement Bond Quantity Worksheet is included in APPENDIX F. Davido Consulting Group, Inc. Page 15 20210608_302 6th Ave S Edmonds_ Drainage ReportRev 2 Stormwater Site Plans — Rev 2 302 6th Ave S Edmonds 9. ADDITIONAL FIGURES June 2021 Davido Consulting Group, Inc. Page 16 20210608_302 6th Ave S Edmonds_ Drainage ReportRev 2 Stormwater Site Plans — Rev 2 302 6th Ave S Edmonds FIGURE 2 Site Assessment and Summary June 2021 Davido Consulting Group, Inc. Page 17 20210608_302 6th Ave S Edmonds_ Drainage ReportRev 2 lo 10 0� p elm wao SCALE IN FEET KEY NOTES KEY DESCRIPTION DETAIU SHEET Oi 4' DOWNSPOUT(TYP) - (D 4'ROOF DOWNSPOUT TIGHTLINE @ 2.00% MIN SLOPE AND 2' MIN COVER (TYP) PERIMETER FOOTING DRAIN -4' PERFORATED O PVC PIPE IN 6" MIN WASHED GRAVEL, WRAPPED IN NON -WOVEN FILTER FABRIC (TYP) NEW 6" SO CONNECTION TO EX 15" CP PSD W/ Oa 48' SADDLE CB W/ SOLID LOCKING LID MATCH RIM TO EXISTING GRADE I/C07 EX 15" PSD IE (W,E) 91.91E 12- IE (S) 91.25 O 10 LF 12"PVC SD@2.00%MIN - TO DRAIN VERTICALLY INTO BP ODOWNSPOUT (SPLASH PAD TO BE LOCATED UNDER BPIC07 DOWNSPOUT) ( 14 LF 12" PVC SD@2.00% MIN SLOPE - O6"SDCO RIM 99.30 UC08 6" IE 94.90 s 63 LF 6"RVC SO@1.50%MIN SLOPE - CB -TYPE 1, #2 HERRINGBONE GRATE OW/ ISO RIM 98.35 GIC06 6" IE (E) 95.50 (W/ SPILL CONTROL ELBOW) SDCB-TYPE 1,#3 HERRINGBONE GRATE OW/ RIM 104.10 G/C06 6' IE (S) 100.35 (W/ SPILL CONTROL ELBOW) O6" SDCO RIM 99.05 UCOB 6" IE BEAD DOWNSPOUT TO ROUTE ALONG FACE OF BUILDING AND DRAIN VERTICALLY INTO BPI DOWNSPOUT TO ROUTE ALONG FACE OF OBUILDING AND DRAIN VERTICALLY INTO BP (SPLASH PAD TO BE LOCATED UNDER DOWNSPOUT) O NOT USED O NOT USED FLOW CONTROL MH - 54' 0 W/ SOLID LOCKING LID RIM 99.05 O 8" IE (S) 94.86 12' IE (N) 92.12 S,T,U/C09 36- IE (E) 92.12 ORIFICE DATA ORIFICE #1: 0.50" 0 ELEV 91.12 4 LF 6' VC SD 1.00%MIN SLOPE - O PIPED INLET TO BP W/ CONC SPLASH BLOCK BPIC07 SDCB TYPE 2#5 W/ VANED GRATE ORIM 98.97 12 IE (S) 91.80 R,TIC09 12' IE (N) 91.70 CB TYPE 2 - 54' 0 W/ SOLID LOCKING LID ORIM 99.00 6" IE IS 95.SO T/C09 6" IE (E) 94.75 36' IE (W) 92.26 0 6LF 6' PVC SO@2.00% - 0 13 LF 6"PVC SD@2.00%MIN - DRAIN O6"TRENCH RIM 101.75 t 6" IE (NW) 97.75 0 28 LF 36" 0 DETENTION PIPE @ 0.50% U/C09 PLANTER W/ UNDERDAIN & 6" TABLE Al ®BIORETENTION PONDING DEPTH. SEE TABLE A ON SHEETC03 CO3, FOR DETAILS BP/C07 0 � I II� Jm na z ww H �zuz i5omrc �� O (SPLASH PAD TO BE LOCATED UNDER BPIC07 LEGEND: T -- g00. ODOWNSPOUT) 6LF6'PVCSO@1.00%MINSLOPE Ho+sE ee ' °.. DRAINAGE roNAL O SEE LANDSCAPE PLANS FOR PLANTINGS WITHIN BIORETENTION PLANTERS WI UNDERORAINS - CONCRETE �i�e II-' 81� / ° \I CONVEYANCE ROUTE 12""AREA DRAIN RIM 98.50 ASPHALT O ASPHALT GRIND&OVER 'Ir _ k II r "� ,°I :a 5°ves�1 6" IE (S) 95.75 8"IE(N)95.65 BIORETENTION PLANTE DRAINAGE I 2MIN SUMP (SEE DETAIL BP/C07) a21 W • W O 4" FOOTING DRAIN TIGHTLINE @ 2.00%MIN - LANDSCAPE CONVEYANCE ROUTE wl ml - O 99LF6"PVCSD@2.00%MINSLOPE - 8"SOC10 ROOF AREA CONTRIBUTI O -- 9�s O RIM 19890 UCOB BIORETENTION PLANTER OF SAME# ay a�as��. .. 3 i Oa a I, A. N 0 12-AREADRAIN O RIM 99.10 6"IE(E)96.50 - wire _ 1 _ i".p 1n C'J W N W ❑ Z 00zE O12"AREA DRAIN RIM 99.10 6" IE (E) 95.59 E°°rv°w°ry PIPE ■ �'- . =1"-�. 'NON -INFILTRATING zaro S Q 12" AREA DRAIN 6'E(E)96.50 PROJECT AREAS saoM c, o.e P1. °°arvEA�. e °s T b-';' _ BIORETENTION PLANTER (TYP) Q 6°soc0 RIM 10045 LIC66 " °� 6 IE IDO 19 . L ll' -OMP- - o w _o z O NOT USED - W Eno rPrvc fifiFF s. O 6LF6'PVCSD@2.00%MINSLOPE _ DEVELOPED AREA CALCULATIONS PROPOSED CONDITIONS � �� anus- E T \\ 1 Pos. N W 9 O BLF 6- PVC SD@2.00%MIN SLOPE - O T LF 6"PVCSD@2.00%MIN SLOPE - ON e,Mi _ -.°,I � _� - p n O TLF 6"PVCSD@2.00%MIN SLOPE _ 7rE6EA (o S,E) b w 4" PVCSD BIORETENTION N PLANTER OUT @ O 2.00% MIN SLOPE (TYP) S N 5p FT 2 ABLE A PRW -ER DESIGNED BY O ROOF AREA ROUTED DIRECTLY TO DETENTION ROOF FACILITY TMNHOUSE BUILDING Nvx vE 1-ELE INLET iE INVERT ELEV iNNEH.I. CHECKED BY TOTu irtty SUNFACES O.t00 t 2 0050 tOt.6a m00 10t.1e sa.e0 t00.1e ss.5o s S.2 to 0Lx S- IC-2-APPROVAL FOR CONSTRUCTION CITYOFEDMONDS vz. sxeErO E t BS a 10 -EC CO3 Stormwater Site Plans — Rev 2 302 6th Ave S Edmonds FIGURE 3 Drainage Plan June 2021 Davido Consulting Group, Inc. Page 18 20210608_302 6th Ave S Edmonds_ Drainage ReportRev 2 n 10 0 10 20 erm SCALE IN FEETomo c-c-ca_o_c z w w H, _ rc U KEY NOTES KEY DESCRIPTION DETAIU SHEET Oi 4' DOWNSPOUT(TYP) - (D 4"ROOF DOWNSPOUT TIGHTLINE @ 2.00% MIN SLOPE AND 2' MIN COVER (TYP) PERIMETER FOOTING DRAIN -4' PERFORATED O PVC PIPE IN 6" MIN WASHED GRAVEL, WRAPPED - IN NON WOVEN FILTER FABRIC (TVP) NEW 6" SO CONNECTION TO EX 15" CP PSD W/ Oa 48" SADDLE CB W/ SOLID LOCKING LID MATCH RIM TO EXISTING GRADE I/C07 EX 15" PSD IE (W,E) 91.01E 12" IE (S) 91.25 (D 10 LF 12"PVC ED@2.00%MIN - DOWNSPOUT TO DRAIN VERTICALLY INTO BP O (SPLASH PAD TO BE LOCATED UNDER BPIC07 DOWNSPOUT) (D 14 LF 12"PVC SO@2.00%MIN SLOPE - O6"SDCO RIM 99.30 UC08 6" IE 94.90 s 63 LFW PVC SO@1.50%MIN SLOPE - SDCB -TYPE 1, #2 HERRINGBONE GRATE OW/ RIM 98.35 GIC06 6" IE (E) 95.50 (W/ SPILL CONTROL ELBOW) SDCB-TYPE 1,#3 HERRINGBONE GRATE (DW/ RIM 104.10 G/C06 6' IE (S) 100.35 (W/ SPILL CONTROL ELBOW) O6" SDCO RIM 99.05 UCOB 6" IE BEAD DOWNSPOUT TO ROUTE ALONG FACE OF BUILDING AND DRAIN VERTICALLY INTO BPI DOWNSPOUT TO ROUTE ALONG FACE OF OBUILDING AND DRAIN VERTICALLY INTO BP (SPLASH PAD TO BE LOCATED UNDER DOWNSPOUT) O NOT USED O NOT USED FLOW CONTROL MH - 54" 0 W/ SOLID LOCKING LID RIM 99.05 O 8" IE (S) 94.86 12" IE (N) 92.12 S,T,U/C09 36" IE (E) 92.12 ORIFICE DATA ORIFICE #1: 0.50" 0 ELEV 91.12 4 LF6" VCSD 1.00%MINSLOPE - O PIPED INLET TO BP W/ CONC SPLASH BLOCK BPIC07 SDCB - TYPE 2 #5 W/ VANED GRATE ORIM 98.97 12 IE (S) 91.80 R,TIC09 12- IE (N) 91.70 CB TYPE 2 - 54- 0 W/ SOLID LOCKING LID ORIM 99.00 6" IE (S) 95.SO T/C09 8" IE (E) 94.75 36" IE (W) 92.26 0 6LF 6- PVC SO@2.00% - 0 13 LF 6" PVC SO@2.00%MIN - TRENCH DRAIN O6" RIM 101.75 t 6" IE (NW) 97.75 0 28 LF 36" 0 DETENTION PIPE @ 0.50% U/C09 PLANTER W/ UNDERDAIN & 6" TABLE Al ®BIORETENTION PONDING DEPTH. SEE TABLE A ON SHEET CO3 CO3, FOR DETAILS BP/CO] I I BI I© Jm O (SPLASH PAD TO BE LOCATED UNDER DOWNSPOUT) BPIC07 LEGEND: HoYsE E ee ] s Os .. o I � 9 g0s. O 6 LF 6' PVC SO @ 1.00% MIN SLOPE CONCRETE $ ��"I O' - any i �r _ \\\ i e s /oNns OBIORLANTERS SEE LANDSCAPE PLANS FOR PLANTINGS WITHIN PWI UNDERDRAIN S (TYP)ETENTION O ASPHALT I �m �e I n/ kp _ _� •1 \ <. 'e 12"AREA DRAIN I %1 axsnves�l I w 0 j i N 3 RIM 98.50 ASPHALT GRIND& OVERLAY a O 6" IE (S) 95.T5 8"IE N)95.65 BIORETENTION PLANTER W/UNDERDRAIN jT I- a�xl�21 ' ---- 2'MINSUMP (SEE DETAIL BP/C07) a •W x O 4" FOOTING GRAIN TIGHTLINE @ 2.00%MIN LANDSCAPE wl e O 99 LF 6- PVC SD@2.00%MIN SLOPE - F 8"SOCO ROOFAREACONTRIBUTINGTO OO -- w�F` 9 O RIM 1C 2 UC08 BIORETENTION PLANTER OF SAME# ay aa I O 12"AREADRAIN RIM 99.10 6"IE(E)96.50 _ _ ___-___ a0a�nvES = i'p \\ U, W N Q Z s DRAIN °- v = / Z _ Q O12"AREA RIM 99.10 I ".� s W 2 Q Z L1 d W 6"IE(E)96.50 rourvo wory vivE � = 1x A� Y O - 12"AREA DRAIN aPo a _ -r- T 1,.� _. d N C) H Q O RIM 99.10 - coxxEx rosin Os U?, 1 W x U Z Z Q Z 6"IE(E)96.50 6"SDCO RIM 10445 L/COB --- --- - _- o -�' x1 1 1' _j, 2 M of 0 U - ❑ W W In Y z 6 IE 100.19 -aw- - d W O NOT USED 6LF6"PvcsD@2.00%MwsLOPe - DEVELOPED AREA CALCULATIONS (PROPOSED CONDITIONS) \\ ) w 's B LF B'PVC SD 2.00%MIN SLOPE @ O TLF 6"PVC SD@2.00%MIN SLOPE - oN O TLF 6"PVC SD@2.00%MINSLOPE - 6[A (orvsn[) b w O 4" PVC SD BIORETENTION PLANTER OUTLET @ 2.00%MIN SLOPE (TVP)ARF N so FT -TAClEl ABLE A PRW -ER OROOF AREA ROUTED DIRECTLY TO DETENTION BY FACILITYDESIGNED 00 evx 111-WILE i11-1 INNI o1N. BY TOTaLirtty SURFACES O.tCHECKED t 1G.. m00 sa.s0 ss.50 2 S.2 0'L R 2.OW APPROVAL FOR CONSTRUCTION x2. sxeErO EPERVSGUSPMEAS ARE INSOFT AR-ACRES2 /Ot.6a t0t.1e t00.Te -BS -10 -EC to 0Lx S- CITY OF EDMONDS E CO3 FILTER FABRIC SILT FENCE A PER COE STANDARD PUN EN 900 C01 3 esaola OMK) D IIDr m Ex® tar fftwTRl asv101ns rrsunrt ORE rnlx u^ arRr]Nrz u�.nsn�ml' mE CIFANOVi DETAIL AT PROPERTY DAIS/COY EASFNENT SE, NOTES i b ACE a Sm-a Na n:Ms 9w1 SE RBFa I] P.0 A111G DEUIn 15HV1 BE NIBTRunm AS ro�LLDws. FL I (C EaIE°R21111 _ Da -- EMML) w R - TYPMJL CIFANODT x ADEwrix/uwDA'MD urtw5. DMa R�•.]�'.0' TINDER ASPHALT ON SDROSETE CDOM aR iw wNETEx a DEEP SSS CLEANOUT E PER CITY OF EDMONDS STANDARD DErAL Ss-m0 COq NOT�ECITY5 1.ON .wl11 TPUE n.rm Numb ro Nur smlETulE. IL T. RE,m.NSION u nwT 0. TO s/I wrE PIEMMnm .uER Sum HIS DEKwa/I SE M— w,m clan s rnw vSR- I—EFEDt— .wlT MDISY a12 NOMP S. ID. ED 13. NL�/�G11nD+c tle mYa a: Cm M'.xEFAwED 9r cm DMaFfl1. CONCRETE CURB AND GUTTER / L1 PER CDE STAN0AR0PIAN TR-sz0 COS ovcR FiowKHoiEs" CATCH BASIN STRAW BALES MAY BE USED IN CERTAIN CIRCUMSTANCES (SEE DETAIL EI.I.I), THIS APPLICAITDN SHALL BE MAINTAINS➢ AT ALL TIMES ➢URING CBNSTRUCITBN PERIOD. CATCH BASIN INLET PROTECTION F PER CITY or EDMONDS STANOnND DETAIL ER-a0z C01 NOTES: ea( "" � wsD'T"' ""'Inoxs. THE SQ�T (nss a,jTH, w H— NOT OE IINCR s1wLL NOT .O.DTD'/IHD a�iEEITa SECTION OE w ocmaonxcE WITH THE wsooijxEPwA DETAIL NOTES - ID µoiaw'-- �`roEx""Px�--44DIOEo As xEcas(a. ro ENS ' — Is xm tR ' — — sQ Are DaNDTAY —P —/Da — —C. — I] w,DE NM. SEE T,IaIESU-1 WA aELOw Eoa aEDDBEO IFI«.,tl. N9 TME cxm.,,cF F RNS I Pu,. A wwRY .,ml s., SCRo"HE wLL SE xa.Imm u�D/ v c°IEwoI'n`o —uA I-111sxus D I wws.ED Oa T-RES orT sllE .wD/Da S'S PDeuc "�'ar SIR cTT IxsPEcroa. xm CITY INSPECRON REQUIRED ON ALL ENOSION CONTROL MEMODS BEFORE OTHER RORK CIN BEGIN CONSTRUCTION ENTRANCE — PER CITY OF EDMONDS STANDARD DETAILS ER101 C01 OPRE SEE � F A D �� ('mot sm�aEc a-m.m7 tY (wswT sum srt�c a�m.u(t)7 AIiN wsNf SiIHawOIS SPELtDUnON D�D]]D(]) E e°WSRr�01u z)�_E F_ SR _ OR 4 •. TPLs MCxgnSK SE [E Elm miiaEEm TI[ D w .N,D al]Ea EE�,Nx R1N. E.DaO �nm. E"TMN CATCH BASIN TYPE I / G PER CITY OF EDMONDS STANDARD DETAIL SD_ CO3 ski 2 BUSINESS DAYS w o Zam 000 2 Y f~O Q 3 W N a 6 ro F N °z cD 0 W Z 0 O of o _ W W 06. Y 0 o Ed O Z a W APPROVAL FOR CONSTRUCTION CITY OFEDMONDS 2 Ey DAE C06 8 , 9NL`mlI c.oL ro sWq w nn• wua ca,c NOTES. S— CONCRETE SIDEWALK / n PERary Or EDMONDS srArvDAxO Dsrna TR531 CO BIORETENTION PLANTER (W/UNDERDRAIN) . W mob ....I.a., v ..n o 0 " A ono grow w�: 99R�.:wu M 9 .i.E..E �t� ,.wr9 swm w,a i nua BIORETENTION PLANTER W/ UNDERDRAIN BP PER Cm Or SEATTLE STANDARD DETAIL BP CO3 KREER 111— cL —TI� 48" SADDLE CB FOR 24" ADMo-PIPE PERCITrOr EDMONDS STANu/ C POST CONSTRUCTION SOIL QUALITY AND DEPTH SA PER —Or EDMONDS—DARD DETAIL SD-2 C01 N9IES: ,0 a SE Po3BE. sEP.R„EL. E,ro. ,RE —RES ON ,aM RMn< p U. 'A.- T. 9M..AOE . ,.NS . p w.,�,/.• �P .r O• DRIVEWAY APPROACH TYPE / PER CITY Or EDMONDS srnrvoaRO DETA :I61, CO Nn cc. ..... Pu,S �...P PIPE a Nr....M ......N.L �T." T. ° Ru D. .a. a NYC � ,ff R. 9 . �.. AS .E.I. BEFORE YOU DIG TYPICAL TRENCH SECTION IFIC—OEEDMONDSSTArvDARDDETAILOOaw C038CO4 0 SsmN'�� 0 a 3 APPROVAL FOR CONSTRUCTION CITY OF EDMONDS EErrv1 1 2 Sy C07 CLEANOUT COVER IN PAVED AREA coy=LEa uwn/ �Ex ax. E (MX)rNDS m "I cox�ernoxCLEjM)SNO'T x0 0) XccXwl (sxmm Mrxix a irclur4 CLEANOUT COVER INT COVER IN L�liGD51 Q[E�iPEE EE GENERAL NOTESNOTES: � uMxR>rNCE AccEss ro Au PIrts NOTES. RBm rov sxuL eE iarwrm ainslDE of PI>tiNXc Mus wnEAE PI,svaz. STORM DRAINAGE CLEANOUT PER CITY OPEDMONDS STANDARD DEruLsoa1. CO � pFP suvxr uto wsiuyxm �p}JIRu:tpx (aut TMuaxc CWE) � xc ]/xurEA uRcwSF; 6 uAxC J/Y uE1m. CDNIRV.'Ita ell O n eml6 SNYL X]r ¢ SEr IX DIdrEJYAY MEAS VH166 rRMPIe Mrm B]x B IFmo'rID eY an FMAXEER. 3/4"A" WATER SERVICE INSTALLATION KN PER CIW DP EDMONDS STANDARD D—LwA-t]o C(� (Ii sue iaa ENTI unms". rv°ixE• `n aneo enwz. llmlr 40�z ""APPEp A°"'xo nrz Mo z .. srMz Ar w Mw>: INS SE mE sm va es-zao .€L r uaro�muro era vex e1wLss• tC mG110X iQIEaL ov aX 1 xxH ACX,Em xsw REeAT .aXDmRLL .,xDu: D+DM P�EESPBxsuxE_ DEcaEEL MXx sPx.rLPaL ca RDX.c muPuxc sXM. a usm MD sEmRm PER �Bmw,M640XfAEiF/"" srRawecx iuBco Rc SUNS �. X sDe Pca PunRE Dz.:LCPNZXr. ug aueffa ,o.R aBaXr Pub ea oa.a M.IeHm .sEaRoa n,a. OE sDDARE .11L x R NEW LATERAL SEWER P PER Cm OF EDMONosRL.SAaooETAlL Ssz C0q TREE GRATE O PER C— OF FDUONDS STANDARD IF-1 rR SSt C05 MIMI log sJ _ eL x,T Dwxm c —I.D llUllEH EL. ru sPEc OMC x�i/�s w E LEM Di © noLEMAMcnoR LExcrn l L eE ii III �iNwa IxDesrnes drama DR m—T © �mwa IxDesrnis"EdrmioaDa °DunnaNT SIGN POST INSTALLATION SIDE WALK AREA O PER arr OF EDMONDS STANDARD DE-L Ta57: C05 2 BUSINESS DAYS 0 3 w w o Z a m 0 0 2 In Y m a 0 W N a 6 ro F N °z cD 0 w Zoo 0U 6, w w Y o W U Z EL w Q APPROVAL FOR CONSTRUCTION CITY OFEDMONDS 2 NY C08 e_TL II7. ITj7v a �P �• SECBOR A- tT.0 �=-vY cAL cBR<7 C g A A 83ys Djr : i i%r ../s• r�'r,`r � '� u ...ten` y,�, ,w r°n. µD nnDXDE ,+° I.oODND .oDD en•-� XD n..IM.,: „EE ,w srzu roDnET XMD t. (IUF11 RE Rxls. 3' IGMD. a�DD�,\w� .XD wmR a wEw,®m ,«r: DR. obll.>•..n. CITY OF EDMONDS STANDARD FRAME INSTALLATION PUBLIC WORKS STANDARD DEPARTMENT DETAIL SD-320 STANDARD FRAME INSTALLATION / R , PER cm OF EDNwrvDESTANDARDDIT ILSDaz CO NDF tdT To SE () m T I res i MVIFIr W/J l� moss Rp; � I I wcE.tpnr�[r+ uip ff sFLe CONNECRON h CONTROL DEVICE pDyLnR ➢ETA LA isFEODDON N o o cv %w ~�- ( 1.11u1 Molm 0. a�Jis) D�l' D. — _s¢ ��PIPE SUPPORT �ouurnx. OFTui R FLOW CONTROL STRUCTURE SXOWN W/ M f NOTES : .XD�E . EXOR Wre "DRD o%muE°`°'t�nnLn OF CITY OF EDMONDS FLOW CONTROL mt. PUBLIC WORKS STRUCTURE DEPARTMENT (FCS) STANDARD DETAIL O.S SD-301 FLOW CONTROL STRUCTURE / a PER cm FA OF EDMONDS STANDARD DEu ID-D CO PROFILE VIEW OF DETENTION PIPE AND FLOW / u CONTROLSTRUCTURE CO "" , u,M'IYwf 9w11M� E clFutW[E Srtv�lx1 u�ia1 �AIMx SIVu W.YE) 6 1N1 STEP 1. SEE 6CITY OF EDMONDS CATCH BASIN. TYPE II mte 48", 54", 80", PUBLIC WORKS H B g 9B" STANDARD DEPARTMENT DETAIL — tYg° SD-300 CATCH BASIN TYPE II / I PER cl,v OF EDmoNDs srArvDARD DETAILso-Doo CO 1 12 BUSINESS DAYS I. w o Zam o2 2 2 In Y DOa 3 In a 6 ro F DO °z 0 w Zoo = o i w w U p ❑ Y 0 o W U Z � a w Q x r APPROVAL FOR CONSTRUCTION CITY OFEDMONDS 2 DAE C09 Stormwater Site Plans — Rev 2 302 6th Ave S Edmonds FIGURE 4 TESC Plan June 2021 Davido Consulting Group, Inc. Page 19 20210608_302 6th Ave S Edmonds_ Drainage ReportRev 2 bm ID o IS s SCALE IN FEET � �Ev KEY NOTES KEY DESCRIPTION DETAIL! SHEET casrs sloswn w °� oo �w€�� MAP E STREET ONLET PROTTECTIOECTIO RV gpgpqp Im°o� IN STORM DRAIN F/C06 NI— -- IN -NI— a£ INSTALL TEMPORARY STORM DRAIN w—w— ��I "� OINLET PROTECTION TO ALL STORM HOUR w—w—"'—w —w—w w—wow—w—w—� —w—,i w--� } pm m a DRAIN INLETS 50' DOWNSTREAM OF — — N"'mil PROPERTY LINE _ CONTRACTOR TO SWEEP STREETS O DAILY AT OR MORE FREQUENT NTERVALS AS NEEDED I NSTALL APPROXIMATELY 209 LF vs vso—P Osso�vso o--vso—vso—aso-- —vs�vs alm= '40 ___vim ems— w v O PERIMETER PROTECTION. -INSTALL coarvc rcv I I m EE S o x°cnvnrcucosna esn J-HOOKS AS NECESSARY TO AIC06 . wrvxaE m a INCREASE RETENTION TIME aim OIN TALL APPROXIMATELY 209 LF HIGH VISIBILITY FENCE �11 i REUSE CONSTRUCTION DRIVEWAY STALL ;: a O DURING CONSTRUCTION OR INSTALL cw c s sm TEMPORARY STABILIZED D/C06 CONSTRUCTION ENTRANCE ea�asa,.c "LtzE Oi SOILAMENDMENT SNCOT O EX STING HARD SURFACE TO BEREMOVI • y'cK+ •`: j O EXISTING FENCE TO BE REMOVED O PRELIMINARY STOCKPILE LOCATION. FINAL LOCATION TBD BY 1—rqq,`. CONTRACTOR v �.`. `. `. `.'. / \ I IEceav,c cvCALL 811 NOT USED -- °USE r'•'.'.':'.' I I IESMn,w P 2 BUSINESS DAYS 4 CAP EX WATER SERVICE AT PIE PRIORTO n� s. 9 / IEwmss,o _v BEFGRE YOU DIG O WATER MLETER TO EITION OF TREUSED FOR J € ss sm "' I••,�� s \\�\ NEW DEVELOPMENT APPROXIMATE LOCATION OF EX SIDE SEWER SERVING EX SFR(NOT slss I••. `. m` 's nj in O SURVEYED). CUT AND CAP SIDE SEWER AT PROPERTY LINE PRIOR TO I L I sseci .TiE DEMOLITION OF STRUCTURES EX POWER SERVICES TO PROPERTY yy"rrS'' �r-M' EM ses OFROM THIS POLE (NOT SURVEYED) TO BE DECOMISSIONED PRIOR TO - S DEMOLITIONOFSTRUCTURES 'INSTALL PERIMETER PROTECTION SUCH AS SILT FENCING, COMPOST SOCKS, OR STRAW WATTLES IN ACCORDANCE WITH VOL. II OF THE DOE (2104 AMENDED) STORMWATER II MANAGEMENT MANUAL FOR WESTERN WASHINGTON GENERAL NOTES II V Q CONSTRUCTION PERMIT IS REQUIRED FOR ALL m o wOB—ITHINTHELITYNIGHT-DRwAYmI LONG AS ,s3SIaLEOGRINGTHE WRSEOFCON3TRu n N aINEOa3 wST2. TatLarvlD rtulDENry nlN nli�i TESCM SUae3 nCC0 orvGEOnavaOveo Tx III !n I M1 W ❑ PI-ANS, CITY OF EDMONDS STANDARD DETAILS Tw1T MAY BE REQUIRED DURING CONSTRUCTIONNO P110THER MEASURES \ \\ Z a O ZO ZQ 3 IN —NnVTI. SUCH •�','•' ' ' ° w < Z °w o AS sloEwaLK RERwwASMENr AND unuTv caNNEcrlorvs. �(��'( p r O ..ono U' 7 \.' Z O LEGEND: .� .1 I o o U, W EL c�i k a 2 M In N e I U In z w ®STABILIZED CONSTRUCTION coaxEa vosln -I" o W U Z ~ ENTRANCE _ "'ff _ _ Q —x— PERIMETER PROTECTION _ v _ � ;\ - —OXP— HIGH VISIBILITY FENCING po�ax%V \\ O { 7 REMOVE EXISTING TREE nU nLLEv �\\ z cesemnw wryI vosry ry I W g — — EXTENTS OF DISTURBANCE �� ? S I o Mrs o STOCKPILE LOCATION w sn Rxa I PRa.MaNBGER: as DESIGNED BY SOILAMENDMENT esvau ODRNNN BY CHECKED BY SOIL AMENDMENT NOTE: I aow" APPROVAL FOR OF DMONDS CONSTRUCTION scat azns sg 3 1. ALL DISTURBED PERVIOUS SURFACE AREAS SHALL BE AMENDED TO MEET THE SOIL QUALITY AND DEPTH REQUIREMENT PER BMP I 18a \ � H DATE: NUMBER TEAS OF THE 2014 DOE STORMWATER MANAGEMENT MANUAL C01 FOR WESTERN WASHINGTON (SEE DETAIL SAICOI). e FILTER FABRIC SILT FENCE A PER COE STANDARD PUN EN 900 C01 3 esaola OMK) D IIDr m Ex® tar fftwTRl asv101ns rrsunrt ORE rnlx u^ arRr]Nrz u�.nsn�ml' mE CIFANOVi DETAIL AT PROPERTY DAIS/COY EASFNENT SE, NOTES i b ACE a Sm-a Na n:Ms 9w1 SE RBFa I] P.0 A111G DEUIn 15HV1 BE NIBTRunm AS ro�LLDws. FL I (C EaIE°R21111 _ Da -- EMML) w R - TYPMJL CIFANODT x ADEwrix/uwDA'MD urtw5. DMa R�•.]�'.0' TINDER ASPHALT ON SDROSETE CDOM aR iw wNETEx a DEEP SSS CLEANOUT E PER CITY OF EDMONDS STANDARD DErAL Ss-m0 COq NOT�ECITY5 1.ON .wl11 TPUE n.rm Numb ro Nur smlETulE. IL T. RE,m.NSION u nwT 0. TO s/I wrE PIEMMnm .uER Sum HIS DEKwa/I SE M— w,m clan s rnw vSR- I—EFEDt— .wlT MDISY a12 NOMP S. ID. ED 13. NL�/�G11nD+c tle mYa a: Cm M'.xEFAwED 9r cm DMaFfl1. CONCRETE CURB AND GUTTER / L1 PER CDE STAN0AR0PIAN TR-sz0 COS ovcR FiowKHoiEs" CATCH BASIN STRAW BALES MAY BE USED IN CERTAIN CIRCUMSTANCES (SEE DETAIL EI.I.I), THIS APPLICAITDN SHALL BE MAINTAINS➢ AT ALL TIMES ➢URING CBNSTRUCITBN PERIOD. CATCH BASIN INLET PROTECTION F PER CITY or EDMONDS STANOnND DETAIL ER-a0z C01 NOTES: ea( "" � wsD'T"' ""'Inoxs. THE SQ�T (nss a,jTH, w H— NOT OE IINCR s1wLL NOT .O.DTD'/IHD a�iEEITa SECTION OE w ocmaonxcE WITH THE wsooijxEPwA DETAIL NOTES - ID µoiaw'-- �`roEx""Px�--44DIOEo As xEcas(a. ro ENS ' — Is xm tR ' — — sQ Are DaNDTAY —P —/Da — —C. — I] w,DE NM. SEE T,IaIESU-1 WA aELOw Eoa aEDDBEO IFI«.,tl. N9 TME cxm.,,cF F RNS I Pu,. A wwRY .,ml s., SCRo"HE wLL SE xa.Imm u�D/ v c°IEwoI'n`o —uA I-111sxus D I wws.ED Oa T-RES orT sllE .wD/Da S'S PDeuc "�'ar SIR cTT IxsPEcroa. xm CITY INSPECRON REQUIRED ON ALL ENOSION CONTROL MEMODS BEFORE OTHER RORK CIN BEGIN CONSTRUCTION ENTRANCE — PER CITY OF EDMONDS STANDARD DETAILS ER101 C01 OPRE SEE � F A D �� ('mot sm�aEc a-m.m7 tY (wswT sum srt�c a�m.u(t)7 AIiN wsNf SiIHawOIS SPELtDUnON D�D]]D(]) E e°WSRr�01u z)�_E F_ SR _ OR 4 •. TPLs MCxgnSK SE [E Elm miiaEEm TI[ D w .N,D al]Ea EE�,Nx R1N. E.DaO �nm. E"TMN CATCH BASIN TYPE I / G PER CITY OF EDMONDS STANDARD DETAIL SD_ CO3 ski 2 BUSINESS DAYS w o Zam 000 2 Y f~O Q 3 W N a 6 ro F N °z cD 0 W Z 0 O of o _ W W 06. Y 0 o Ed O Z a W APPROVAL FOR CONSTRUCTION CITY OFEDMONDS 2 Ey DAE C06 Stormwater Site Plans — Rev 2 302 6th Ave S Edmonds FIGURE 5 Offsite Analysis Photos June 2021 Davido Consulting Group, Inc. Page 20 20210608_302 6th Ave S Edmonds_ Drainage ReportRev 2 Photos Project: 302 6' Ave S Edmonds, Parcel#00434212201900 Aerial Photo w/ Corresponding Photo Locations North r Page 1 of 3 11 1 Photos Project: 302 6' Ave S Edmonds, Parcel#00434212201900 Photo 1 (looking NE): Manhole (#1) upstream of the point of connection to the 15" concrete storm main that flows west. - r - � x Photo 2 (looking W): Manhole (#2) 15" concrete inlet from the east and 15" concrete outlet that flows west. Photo 3 (looking SW): Catch basin (#1) 15" concrete inlet from the east and 15" concrete outlet that flows west. lei vl.--'""!�A' Photo 4 (looking NW): Manhole (#3) 15" concrete inlet from the east and 15" concrete outlet that flows west. Manhole (#4) 15" concrete inlet from the east and 15" concrete outlet that flows north. Photo 5 (looking N): Manhole (#5) 15" concrete inlet from the south and 15" concrete outlet that flows west. Photo 6 (looking NW): Manhole (#6) 15" concrete inlet from the east and 18" concrete outlet that flows west. Manhole (#7) 18" concrete inlet from the east and 18" concrete outlet that flows west. Page 2 of 3 Photos Project: 302 6' Ave S Edmonds, Parcel#00434212201900 Photo 7 (looking W): Manhole (#8) 18" concrete inlet from the east and 18" concrete outlet that flows southwest. Photo 8 (looking W): Manhole (#9) 18" concrete inlet from the northeast and 36" concrete outlet that flows south. ,3 Photo 9 (looking W): Manhole (#10) 36" concrete inlet from the north and 36" concrete outlet that flows south. Photo 10 (looking S): Manhole (#11) 36" concrete inlet from the north and 36" concrete outlet flows to the south. Photo 11 (looking W): Manhole (#12) could not be found but according to Edmonds GIS it has a 24" concrete outlet that flows west into Shellabarger Creek. Page 3 of 3 Stormwater Site Plans — Rev 2 302 61h Ave S Edmonds FIGURE 6 Offsite Drainage System Analysis June2021 Davido Consulting Group, Inc. Page 21 20210608_302 6th Ave S Edmonds —Drainage Report Rev 2 Project: 302 6th Ave S Edmonds Owner: Parcels: 00434212201900 DOWNSTREAM DRAINAGE SYSTEM ANALYSIS Basin: Shellabarger Creek Subbasin: N/A Subbasin #: N/A Date: 7/2/2019 Date of Inspection: 6/27/2019 Weather: Sunny Observations of field Drainage Component Type, Drainage Component Distance from site inspector, resource reviewer, Symbol Name, and Size Description Slope Length discharge Existing Problems Potential Problems or resident Type: sheet flow, swale, drainage basin, vegetation, constrictions, under capacity, ponding, overtopping, flooding, tributary area, likelihood of see map stream, channel, pipe, pond; cover, depth, type of % ft /o ml = 1,320 ft. habitat or organism destruction, scouring, bank sloughing, problem, overflow pathways, Size: diameter, surface area sensitive area, volume sedimentation, incision, other erosion potential impacts From Manhole #1 through 15 1 to 2 concrete pipe to Manhole #2 in Pavement 2.0% 330 0 to 330 No Problems No Problems None Maple St From Manhole #2 through 15" 2 to 3 concrete pipe to catch basin #1 Pavement 2.0% 100 330 to 430 No Problems No Problems None in Maple St From catch basin #1 through 3 to 4 15 concrete pipe to Manhole Pavement 2.0% 217 430 to 647 No Problems No Problems None #3 in Maple St From manhole #3 through 15" 4 concrete pipe to manhole #4 in Pavement 2.0% 24 647 to 671 No Problems No Problems None the intersection of Maple St and 5th Ave S From manhole #4 through 15" 4 to 5 concrete pipe to manhole #5 in Pavement 2.0% 300 671 to 971 No Problems No Problems None 5th Ave S From manhole #5 through 15" 5 to 6 concrete pipe to manhole #6 in Pavement 2.0% 310 971 to 1281 No Problems No Problems None Dayton St From manhole #6 through 18" 6 concrete pipe to manhole #7 in Pavement 2.0% 6 1281 to 1287 No Problems No Problems None Dayton St From manhole #7 through 18" 6 to 7 concrete pipe to manhole #8 in Pavement 2.0% 310 1287 to 1597 No Problems No Problems None Dayton St From manhole #8 through 18" 7 to 8 concrete pipe to manhole #9 in Pavement 2.0% 65 1597 to 1662 No Problems No Problems None the intersection of Dayton St and 3rd Ave S From manhole #9 through 36" 8 to 9 concrete pipe to manhole #10 Pavement 2.0% 390 1662 to 2052 No Problems No Problems None in 3rd Ave S From manhole #10 through 36" 9 to 10 concrete pipe to manhole #11 Pavement 2.0% 470 2052 to 2522 No Problems No Problems None in 3rd Ave S From manhole #11 through 36" 10 to 11 concrete pipe to manhole #12 Pavement 2.0% 300 2522 to 2822 No Problems No Problems None in 3rd Ave S Page 1 of 1 Stormwater Site Plans — Rev 2 302 6th Ave S Edmonds FIGURE 7 Developed Conditions Sub -Basin Exhibit June 2021 Davido Consulting Group, Inc. Page 22 20210608_302 6th Ave S Edmonds_ Drainage ReportRev 2 LEGEND: DRIVEWAY AREA TO AREA TRIBUTARY TO DETENTION TANK (3,424 SF) DETENTION TANK -AREA TRIBUTARY TO BIORETENTION 772 SF PLANTER BOX #1 (193 SF) -AREA TRIBUTARY TO BIORETENTION PLANTER BOX #2 (449 SF) AREA TRIBUTARY TO BIORETENTION PLANTER BOX #3 (519 SF) °a AREA TRIBUTARY TO BIORETENTION g ' PLANTER BOX #4 (1,339 SF) ROOF AREA TO AREA BYPASSING DETENTION TANK STORMWATER BMPS (829 SF) B 857 SF w UPPER PARKING AREA TO BP #4 425 SF ALLEY AREA (INCLUDING e EX PAVEMENT) TO -- ----- DETENTION TANK 1,420 SF om 0 ROOF BASIN 2 T4BP#2 449 SF WALKWAYS TOSSDAYS4 YOU DIG DETENTION TANK 375 SF Pt -- O i\j F ROOBASIN 3 TO BP #3 Pw J 519 SF FF g Sa Es o i ROOF BASIN 4 TO BP #4 2E� — ,. —i, EDo wN oZ 914SF o. ZQ� ooZs FF992, EL "•��+ Yea 3:ED °_LE FRONTAGE IMPROVEMENTS BYPASSING BMPS °T 829 SF APPROVAL FOR CONSTRUCTION C ITY OF EDMONDS EEz021 2 DIE MBER rE o FERN o =a CO3 Stormwater Site Plans — Rev 2 302 6th Ave S Edmonds APPENDIX A Geotechnical Report June 2021 20210608_302 6th Ave S Edmonds_ Drainage ReportRev 2 NGA Main Office 17311— 135" Ave NE, A-500 Woodinville, WA 98072 (425) 486-1669 • FAX (425) 481-2510 March 21, 2019 Mr. Chris Pickering VIA Email: crispyjzreen@comcast.net NELSON GEOTECHNICAL ASSOCIATES, INC. GEOTECHNICAL ENGINEERS & GEOLOGISTS Engineering -Geology Branch 5526 Industry Lane, #2 East Wenatchee, WA 98802 (509) 665-7696 • FAX (509) 665-7692 Geotechnical Engineering Evaluation Pickering 6" Avenue South Townhome Residential Development 302 - 6" Avenue South Edmonds, Washington NGA Project No. 1083719 Dear Mr. Pickering: We are pleased to submit the attached report titled "Geotechnical Engineering Evaluation — Pickering 6t' Avenue South Townhome Residential Development — 302 - 6' Avenue South — Edmonds, Washington." This report summarizes our observations of the existing surface and subsurface conditions within the site, and provides general recommendations for the proposed site development. Our services were completed in general accordance with the proposal signed by you on January 23, 2019. The relatively level to gently sloping, rectangular -shaped subject site is currently occupied by a single- family residence and detached garage structure within the northern and southwestern portions of the site, respectively. The property is bordered to the west and south by existing residential properties, to the north by Maple Street, and to the east by 6t' Avenue South. We understand the proposed improvements within the site will consist of removing the existing structures and constructing a new three -unit townhome residence structure. Specific grading and stormwater plans were not available when this report was prepared, however we understand that stormwater may be directed to on -site infiltration facilities, if feasible. In addition to providing recommendations for the development of the new residential structure, we have been requested to evaluate the infiltration capacity of the site soils. The City of Edmonds utilizes the 2014 WSDOE Stormwater Management Manual for Western Washington to determine the design of infiltration facilities. According to this manual, on -site infiltration testing consisting of the small Pilot Infiltration Test (PIT) is used to determine the long-term design infiltration rates. We monitored the excavation of four test pit explorations throughout the property, two of which we utilized for our small-scale PIT testing. Our explorations indicated that the site was underlain by surficial undocumented fill with competent, native glacial soils at depth. It is our opinion that the proposed site development is feasible from a geotechnical engineering standpoint, provided that our recommendations for site development are incorporated into project plans. In general, the competent bearing native glacial soils underlying the site should adequately support the planned structures. Foundations should be advanced through any loose and/or undocumented fill soils down to the competent native bearing material for bearing capacity and settlement considerations. These soils should generally be encountered approximately five feet below the existing ground surface, based on our explorations. If loose soils or undocumented fill are encountered in unexplored areas of the site, they should be removed and replaced with structural fill for foundation and pavement support. Final NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation NGA File No. 1083719 Pickering 6r' Ave South Residential Development March 21, 2019 Edmonds, Washington Summary — Page 2 stormwater plans have also not been developed, but we understand that on -site infiltration is being considered for this site. Based on our onsite testing, it is our opinion that the onsite soils are not conducive to traditional methods of stormwater infiltration, however low -impact design systems may be feasible. The subsurface soils generally consisted of surficial undocumented fill soils underlain by silty fine to medium sand with varying amounts of gravel and iron -oxide weathering that we interpreted as native glacial soils at relatively shallow depths. We recommend that any low impact stormwater infiltration systems be designed in accordance with the 2014 WSDOE Stormwater Management Manual for Western Washinaton. In the attached report, we have also provided general recommendations for site grading, slabs -on -grade, structural fill placement, retaining walls, erosion control, and drainage. We should be retained to review and comment on final development plans and observe the earthwork phase of construction. We also recommend that NGA be retained to provide monitoring and consultation services during construction to confirm that the conditions encountered are consistent with those indicated by the explorations, to provide recommendations for design changes should the conditions revealed during the work differ from those anticipated, and to evaluate whether or not earthwork and foundation installation activities comply with contract plans and specifications. It has been a pleasure to provide service to you on this project. Please contact us if you have any questions regarding this report or require further information. Sincerely, NELSON GEOTECHNICAL ASSOCIATES, INC. M Khaled M. Shawish, PE Principal Engineer TABLE OF CONTENTS INTRODUCTION............................................................................................................. I SCOPE............................................................................................................................... 1 SITECONDITIONS......................................................................................................... 2 SurfaceConditions....................................................................................................... 2 SubsurfaceConditions.................................................................................................. 2 HydrogeologicConditions........................................................................................... 3 SENSITIVE AREA EVALUATION............................................................................... 3 SeismicHazard............................................................................................................. 3 ErosionHazard............................................................................................................. 4 CONCLUSIONS AND RECOMMENDATIONS.......................................................... 4 General......................................................................................................................... 4 ErosionControl............................................................................................................ 5 Site Preparation and Grading....................................................................................... 5 Temporary and Permanent Slopes............................................................................... 6 Foundations.................................................................................................................. 7 RetainingWalls............................................................................................................ 8 StructuralFill................................................................................................................ 9 Slab-on-Grade............................................................................................................ 10 Pavement Subgrade and Other Hard Surfaces........................................................... 10 Utilities....................................................................................................................... 1 l SiteDrainage.............................................................................................................. 11 CONSTRUCTION MONITORING............................................................................. 12 USEOF THIS REPORT................................................................................................ 13 LIST OF FIGURES Figure 1 Vicinity Map Figure 2 Site Plan Figure 3 Soil Classification Chart Figure 4 Test Pit Logs NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation Pickering 6" Avenue South Townhome Residential Development 302 - 6' Avenue South Edmonds, Washington INTRODUCTION This report presents the results of our geotechnical engineering investigation and evaluation of the planned 6th Avenue South Residential Development project in the Edmonds, Washington. The project site is located at 302 - 6tn Avenue South, as shown on the Vicinity Map in Figure 1. The purpose of this study is to explore and characterize the site's surface and subsurface conditions and to provide geotechnical recommendations for the planned site development. For our use in preparing this report, we have been provided with an undated preliminary site plan titled "Pickering Townhomes," showing the proposed conditions within the site. The property is currently occupied by a single-family residence and detached garage structure within the northern and southwestern portions of the site, respectively. The remaining portions of the property are occupied by a concrete driveway and a grass -covered yard area within the western and southern portions of the site, respectively. The site is generally level to gently sloping from the south to the north. We understand that the proposed development within the site will include constructing a new three -unit townhome structure. Final development and grading plans have not been prepared at the time this report was issued. Final stormwater plans have also not been developed, however, we understand that stormwater may be directed to on -site infiltration systems, if feasible. The existing and proposed site layout is shown on the Site Plan in Figure 2. SCOPE The purpose of this study is to explore and characterize the site surface and subsurface conditions, and provide general recommendations for site development. Specifically, our scope of services includes the following: 1. Review available soil and geologic maps of the area. 2. Explore the subsurface soil and groundwater conditions within the site with trackhoe- excavated test pits. Trackhoe was provided by the client. 3. Conduct laboratory analyses on selected soil samples, as needed. 4. Provide recommendations for earthwork, foundation support, and slab on grade subgrades. 5. Provide recommendations for pavement subgrade preparation. 6. Provide recommendations for temporary and permanent slopes. 7. Determine feasibility of on -site stormwater infiltration. NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation NGA File No. 1083719 Pickering 6r' Ave South Residential Development March 21, 2019 Edmonds, Washington Page 2 8. Provide long-term design infiltration rates based on two on -site Small Scale Pilot Infiltration Test (PIT) per the 2014 WSDOE Stormwater Management Manual for Western Washington. Location and depth of test was determined by civil engineer. Water for the test was secured by client. 9. Provide recommendations for infiltration system installation. 10. Provide recommendations for site drainage and erosion control. 11. Document the results of our findings, conclusions, and recommendations in a written geotechnical report. SITE CONDITIONS Surface Conditions The subject site consists of a rectangular -shaped parcel covering approximately 0.15 acres. The site is generally level to gently sloping from the south to the north and is currently occupied by a single-family residence, a detached garage and a concrete driveway within the northern, southwestern, and western portions of the site, respectively. The southeastern and central portions of the property generally consist of grass -covered yard areas, landscaping plants, and scattered trees. The site is bound to the north by Maple Street, to the east by 6' Avenue South, and to the south and west by existing residential properties. We did not observe surface water throughout the site during our visit on February 21, 2019. Subsurface Conditions Geology: The geologic units for the overall site are shown on Geologic map of the Edmonds East and part of the Edmonds West quadrangles, Washington, by Minard, J.P. (USGS, 1983). The site is mapped as Transitional Beds (Qtb) with Vashon till (Qvt) and Advance Outwash (Qva) in the near vicinity. The transitional beds seem to grade upward into the base of the overlying advance outwash at some localities and consist of clay, silt and fine to very fine sand. The Till is generally described as a non -sorted mixture of clay, silt, sand, pebbles, cobbles, and boulders, all in variable amounts. The advance outwash is described as mostly clean gray pebbly sand. Our explorations typically encountered surficial undocumented fill underlain by silty fine to medium sand with varying amounts of gravel, which we interpreted as native glacial till soils at depth. Explorations: The subsurface conditions within the site were explored on February 21, 2019 by excavating four test pits to approximate depths in the range of 7.6 to 9.0 feet below the existing ground surface using a mini-trackhoe. The approximate locations of our explorations are shown on the Site Plan in Figure 2. A geologist from NGA was present during the explorations, examined the soils and geologic conditions encountered, obtained samples of the different soil types, and maintained logs of the test pits. NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation NGA File No. 1083719 Pickering 6r' Ave South Residential Development March 21, 2019 Edmonds, Washington Page 3 The soils were visually classified in general accordance with the Unified Soil Classification System, presented in Figure 3. The logs of our test pits are attached to this report and are presented as Figure 4. We present a brief summary of the subsurface conditions in the following paragraph. For a detailed description of the subsurface conditions, the logs of the test pits should be reviewed. At the surface of Infiltration Pits 1 and 2 and Test Pits I and 2, we generally encountered 4.8 to 5.5 feet of loose, dark brown to orange -brown, silty fine to medium sand with gravel, roots, and organics, which we interpreted as undocumented fill soils. Underlying the fill soils in each of our explorations, we generally encountered gray, silty fine to medium sand with gravel, cobbles, and iron -oxide staining, which we interpreted as native glacial soils. Infiltration Pit 1 and 2 and Test Pit 1 and 2 were terminated within the native glacial till soils at depths in the range of 7.6 to 9.0 feet below the existing ground surface. Hydrogeologic Conditions We encountered varying degrees of groundwater seepage within Infiltration Pit 1 and Infiltration Pit 2 at depths in the range of 7.0 to 8.0 feet below the existing ground surface. We interpret the water observed as a perched groundwater condition. Perched water occurs when surface water infiltrates through less dense, more permeable soils and accumulates on top of relatively low permeability materials. The more permeable soils consist of the topsoil/weathered soils and undocumented fill. The low permeability soil consists of relatively silty native deposits. Perched water does not represent a regional groundwater "table" within the upper soil horizons. Perched water tends to vary spatially and is dependent upon the amount of rainfall. We would expect the amount of perched groundwater to decrease during drier times of the year and increase during wetter periods. SENSITIVE AREA EVALUATION Seismic Hazard We reviewed the 2018 International Building Code (IBC) for seismic site classification for this project. Since competent glacial soils are inferred to underlie the site at depth, the site conditions best fit the IBC description for Site Class D. Table 1 below provides seismic design parameters for the site that are in conformance with the 2018 IBC, which specifies a design earthquake having a 2% probability of occurrence in 50 years (return interval of 2,475 years), and the 2008 USGS seismic hazard maps. NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation NGA File No. 1083719 Pickering 6r' Ave South Residential Development March 21, 2019 Edmonds, Washington Page 4 Table 1 — 2018 IBC Seismic Design Parameters Site Class Spectral Acceleration Spectral Acceleration Site Coefficients Design Spectral at 0.2 sec. (g) at 1.0 sec. (g) Response S, S 1 Parameters F,, F, SDs SDI r-D 1.269 0.497 1.000 1.503 0.846 0.498 The spectral response accelerations were obtained from the USGS Earthquake Hazards Program Interpolated Probabilistic Ground Motion website (2008 data) for the project latitude and longitude. Hazards associated with seismic activity include liquefaction potential and amplification of ground motion. Liquefaction is caused by a rise in pore pressures in a loose, fine sand deposit beneath the groundwater table. It is our opinion that the medium dense or better native deposits interpreted to underlie the site have a low potential for liquefaction or amplification of ground motion. Erosion Hazard The criteria used for determination of the erosion hazard for affected areas include soil type, slope gradient, vegetation cover, and groundwater conditions. The erosion sensitivity is related to vegetative cover and the specific surface soil types, which are related to the underlying geologic soil units. The Soil Survey of Snohomish County Area, Washington, by the Natural Resources Conservation Service (MRCS) was reviewed to determine the erosion hazard of the on -site soils. The surface soils for this site were mapped as Everett very gravelly sandy loam, 15 to 30 percent slopes. The erosion hazard for this material is listed as moderate. This site is relatively level to gently sloping and there are no steep slopes on the property. It is our opinion that the erosion hazard for site soils should be low in areas where the site is not disturbed. CONCLUSIONS AND RECOMMENDATIONS General It is our opinion that the planned development is feasible from a geotechnical standpoint. Our explorations indicated that the site is generally underlain by competent native bearing glacial soils at relatively shallow depths. The native soils encountered at depth should provide adequate support for foundation, slab, and pavement loads. We recommend that the planned structure be designed utilizing shallow foundations. Footings should extend through any loose soil or undocumented fill soils and be founded on the underlying medium dense or better native bearing glacial soils, or structural fill extending to these soils. The medium dense or better native glacial soils should typically be encountered approximately five feet below the existing surface, based on our explorations. We should note that localized areas of deeper unsuitable soils and/or undocumented fill could be encountered at this site. This NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation NGA File No. 1083719 Pickering 6r' Ave South Residential Development March 21, 2019 Edmonds, Washington Page 5 condition would require additional excavations in foundation, slab, and pavement areas to remove the unsuitable soils. We have provided detailed recommendations regarding slab -on -grade, pavement and hard surfacing in the Slab -on -Grade and Pavement subgrade and Other Hard Surfaces subsections of this report. Based on the results of our infiltration testing and soil explorations throughout the site, it is our opinion that the onsite native soils are not conducive for traditional methods of stormwater infiltration. This is further discussed in the Site Drainage section of this report. Erosion Control The erosion hazard for the on -site soils is interpreted to be moderate for exposed soils, but actual erosion potential will be dependent on how the site is graded and how water is allowed to concentrate. Best Management Practices (BMPs) should be used to control erosion. Areas disturbed during construction should be protected from erosion. Erosion control measures may include diverting surface water away from the stripped or disturbed areas. Silt fences and/or straw bales should be erected to prevent muddy water from leaving the site. Disturbed areas should be planted as soon as practical and the vegetation should be maintained until it is established. The erosion potential of areas not stripped of vegetation should be low. Site Preparation and Grading After erosion control measures are implemented, site preparation should consist of stripping the topsoil, undocumented fill and loose soils from foundation, slab, pavement areas, and other structural areas, to expose medium dense or better native bearing glacial soils. The stripped soil should be removed from the site or stockpiled for later use as a landscaping fill. Based on our observations, we anticipate stripping depths of approximately five feet, depending on the specific locations. However, additional stripping may be required if areas of deeper undocumented fill and/or loose soil are encountered in unexplored areas of the site. After site stripping, if the exposed subgrade is deemed loose, it should be compacted to a non -yielding condition and then proof -rolled with a heavy rubber -tired piece of equipment. Areas observed to pump or weave during the proof -roll test should be reworked to structural fill specifications or over -excavated and replaced with properly compacted structural fill or rock spalls. If loose soils are encountered in the pavement areas, the loose soils should be removed and replaced with rock spalls or granular structural fill. If significant surface water flow is encountered during construction, this flow should be diverted around areas to be developed, and the exposed subgrades should be maintained in a semi -dry condition. NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation NGA File No. 1083719 Pickering 6r' Ave South Residential Development March 21, 2019 Edmonds, Washington Page 6 If wet conditions are encountered, alternative site stripping and grading techniques might be necessary. These could include using large excavators equipped with wide tracks and a smooth bucket to complete site grading and covering exposed subgrade with a layer of crushed rock for protection. If wet conditions are encountered or construction is attempted in wet weather, the subgrade should not be compacted as this could cause further subgrade disturbance. In wet conditions it may be necessary to cover the exposed subgrade with a layer of crushed rock as soon as it is exposed to protect the moisture sensitive soils from disturbance by machine or foot traffic during construction. The prepared subgrade should be protected from construction traffic and surface water should be diverted around areas of prepared subgrade. The site soils are considered to be moisture -sensitive and will disturb easily when wet. We recommend that construction takes place during the drier summer months if possible. However, if construction takes place during the wet season, additional expenses and delays should be expected due to the wet conditions. Additional expenses could include the need for placing a blanket of rock spalls on exposed subgrades, construction traffic areas, and paved areas prior to placing structural fill. Wet weather grading will also require additional erosion control and site drainage measures. Some of the native on -site soils may be suitable for use as structural fill, depending on the moisture content of the soil at the time of construction. It is our opinion that the undocumented fill soils encountered within the site are not suitable for structural fill. NGA should be retained to evaluate the suitability of all on -site and imported structural fill material during construction. Temporary and Permanent Slopes Temporary cut slope stability is a function of many factors, including the type and consistency of soils, depth of the cut, surcharge loads adjacent to the excavation, length of time a cut remains open, and the presence of surface or groundwater. It is exceedingly difficult under these variable conditions to estimate a stable, temporary, cut slope angle. Therefore, it should be the responsibility of the contractor to maintain safe slope configurations at all times as indicated in OSHA guidelines for cut slopes. The following information is provided solely for the benefit of the owner and other design consultants and should not be construed to imply that Nelson Geotechnical Associates, Inc. assumes responsibility for job site safety. Job site safety is the sole responsibility of the project contractor. For planning purposes, we recommend that temporary cuts in the upper undocumented fill soils be no steeper than 2 Horizontal to 1 Vertical (2H:IV). Temporary cuts in the competent native glacial soils at depth should be no steeper than 1.5H:IV. If significant groundwater seepage or surface water flow were encountered, we would expect that flatter inclinations would be necessary. We recommend that cut slopes be protected from erosion. The slope protection measures may include covering cut slopes with plastic sheeting and diverting surface runoff away from the top of cut slopes. We do not recommend NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation NGA File No. 1083719 Pickering 6r' Ave South Residential Development March 21, 2019 Edmonds, Washington Page 7 vertical slopes for cuts deeper than four feet, if worker access is necessary. We recommend that cut slope heights and inclinations conform to appropriate OSHA/WISHA regulations. Permanent cut and fill slopes should be no steeper than 2H:IV. However, flatter inclinations may be required in areas where loose soils are encountered. Permanent slopes should be vegetated and the vegetative cover maintained until established. Foundations Conventional shallow spread foundations should be placed on medium dense or better native bearing soils, or be supported on structural fill or rock spalls extending to those soils. Medium dense soils should be encountered approximately five feet below ground surface based on our explorations. Where undocumented fill or less dense soils are encountered at footing bearing elevation, the subgrade should be over -excavated to expose suitable bearing soil. The over -excavation may be filled with structural fill, or the footings may be extended down to the competent native bearing soils. If footings are supported on structural fill, the fill zone should extend outside the edges of the footing a distance equal to one half of the depth of the over -excavation below the bottom of the footing. Footings should extend at least 18 inches below the lowest adjacent finished ground surface for frost protection and bearing capacity considerations. Foundations should be designed in accordance with the 2018 IBC. Footing widths should be based on the anticipated loads and allowable soil bearing pressure. Water should not be allowed to accumulate in footing trenches. All loose or disturbed soil should be removed from the foundation excavation prior to placing concrete. For foundations constructed as outlined above, we recommend an allowable design bearing pressure of not more than 2,500 pounds per square foot (psf) be used for the design of footings founded on the medium dense or better native bearing soils or structural fill extending to the competent native bearing material. The foundation bearing soil should be evaluated by a representative of NGA. We should be consulted if higher bearing pressures are needed. Current IBC guidelines should be used when considering increased allowable bearing pressure for short-term transitory wind or seismic loads. Potential foundation settlement using the recommended allowable bearing pressure is estimated to be less than 1-inch total and'/2-inch differential between adjacent footings or across a distance of about 20 feet, based on our experience with similar projects. NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation NGA File No. 1083719 Pickering 6r' Ave South Residential Development March 21, 2019 Edmonds, Washington Page 8 Lateral loads may be resisted by friction on the base of the footing and passive resistance against the subsurface portions of the foundation. A coefficient of friction of 0.35 may be used to calculate the base friction and should be applied to the vertical dead load only. Passive resistance may be calculated as a triangular equivalent fluid pressure distribution. An equivalent fluid density of 200 pounds per cubic foot (pcf) should be used for passive resistance design for a level ground surface adjacent to the footing. This level surface should extend a distance equal to at least three times the footing depth. These recommended values incorporate safety factors of 1.5 and 2.0 applied to the estimated ultimate values for frictional and passive resistance, respectively. To achieve this value of passive resistance, the foundations should be poured "neat" against the native medium dense soils or compacted fill should be used as backfill against the front of the footing. We recommend that the upper one foot of soil be neglected when calculating the passive resistance. Retaining Walls Specific grading plans for this project were not available at the time this report was prepared, but retaining walls may be incorporated into project plans. In general, the lateral pressure acting on retaining walls is dependent on the nature and density of the soil behind the wall, the amount of lateral wall movement which can occur as backfill is placed, wall drainage conditions, and the inclination of the backfill. For walls that are free to yield at the top at least one thousandth of the height of the wall (active condition), soil pressures will be less than if movement is limited by such factors as wall stiffness or bracing (at -rest condition). We recommend that walls supporting horizontal backfill and not subjected to hydrostatic forces, be designed using a triangular earth pressure distribution equivalent to that exerted by a fluid with a density of 40 pcf for yielding (active condition) walls, and 60 pcf for non -yielding (at -rest condition) walls. A seismic design loading of 8H should also be included in the wall design, where H represents the total height of the wall. These recommended lateral earth pressures are for a drained granular backfill and are based on the assumption of a horizontal ground surface behind the wall for a distance of at least the height of the wall, and do not account for surcharge loads. Additional lateral earth pressures should be considered for surcharge loads acting adjacent to walls and within a distance equal to the height of the wall. This would include the effects of surcharges such as traffic loads, floor slab loads, slopes, or other surface loads. We could consult with the structural engineer regarding additional loads on retaining walls during final design, if needed. The lateral pressures on walls may be resisted by friction between the foundation and subgrade soil, and by passive resistance acting on the below -grade portion of the foundation. Recommendations for frictional and passive resistance to lateral loads are presented in the Foundations subsection of this report. NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation NGA File No. 1083719 Pickering 6r' Ave South Residential Development March 21, 2019 Edmonds, Washington Page 9 All wall backfill should be well compacted as outlined in the Structural Fill subsection of this report. Care should be taken to prevent the buildup of excess lateral soil pressures due to over -compaction of the wall backfill. This can be accomplished by placing wall backfill in 8-inch loose lifts and compacting the backfill with small, hand -operated compactors within a distance behind the wall equal to at least one-half the height of the wall. The thickness of the loose lifts should be reduced to accommodate the lower compactive energy of the hand -operated equipment. The recommended level of compaction should still be maintained. Permanent drainage systems should be installed for retaining walls. Recommendations for these systems are found in the Subsurface Drainage subsection of this report. We recommend that we be retained to evaluate the proposed wall drain backfill material and observe installation of the drainage systems. Structural Fill General: Fill placed beneath foundations, pavement, or other settlement -sensitive structures should be placed as structural fill. Structural fill, by definition, is placed in accordance with prescribed methods and standards, and is monitored by an experienced geotechnical professional or soils technician. Field monitoring procedures would include the performance of a representative number of in -place density tests to document the attainment of the desired degree of relative compaction. The area to receive the fill should be suitably prepared as described in the Site Preparation and Grading subsection prior to beginning fill placement. Materials: Structural fill should consist of a good quality, granular soil, free of organics and other deleterious material, and be well graded to a maximum size of about three inches. All-weather fill should contain no more than five -percent fines (soil finer than U.S. No. 200 sieve, based on that fraction passing the U.S. 3/4-inch sieve). Some of the more granular native on -site soils may be suitable for use as structural fill, but this will be highly dependent on the moisture content of these soils at the time of construction. In our opinion, the surficial undocumented fill soils are not suitable for use as structural fill. We should be retained to evaluate all proposed structural fill material prior to placement. Fill Placement: Following subgrade preparation, placement of structural fill may proceed. All filling should be accomplished in uniform lifts up to eight inches thick. Each lift should be spread evenly and be thoroughly compacted prior to placement of subsequent lifts. All structural fill underlying building areas and pavement subgrade should be compacted to a minimum of 95 percent of its maximum dry density. Maximum dry density, in this report, refers to that density as determined by the ASTM D-1557 Compaction Test procedure. The moisture content of the soils to be compacted should be within about two percent of optimum so that a readily compactable condition exists. It may be necessary to over - excavate and remove wet soils in cases where drying to a compactable condition is not feasible. All NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation NGA File No. 1083719 Pickering 6r' Ave South Residential Development March 21, 2019 Edmonds, Washington Page 10 compaction should be accomplished by equipment of a type and size sufficient to attain the desired degree of compaction and should be tested. Slab -on -Grade Slabs -on -grade should be supported on subgrade soils prepared as described in the Site Preparation and Grading subsection of this report. However, undocumented fill soils may be encountered at slab subgrade elevations. If some future slab settlement and/or cracking cannot be tolerated, we recommend that at a minimum, the slab subgrade be overexcavated by two feet and the overexcavation backfilled with P/4-inch crushed rock compacted to structural fill specifications. The resulting overexcavation subgrade should be compacted to an unyielding condition prior to placement of the crushed rock backfill. Additional reinforcement and doweled cold joints should be incorporated into the slab design. We recommend that all floor slabs be underlain by at least six inches of free -draining gravel with less than three percent by weight of the material passing Sieve #200 for use as a capillary break. We recommend that the capillary break be hydraulically connected to the footing drain system to allow free drainage from under the slab. A suitable vapor barrier, such as heavy plastic sheeting (6-mil minimum), should be placed over the capillary break material. An additional 2-inch-thick moist sand layer may be used to cover the vapor barrier. This sand layer may be used to protect the vapor barrier membrane and to aid in curing the concrete. Pavement Subgrade and Other Exterior Hard Surfaces Pavement and walkway subgrade preparation should be completed as recommended in the Site Preparation and Grading and Structural Fill subsections of this report. Depending on tolerance to cracking, we recommend that at least the upper two feet of the existing material be removed and replaced with granular structural fill or crushed rock. The subgrades should be proof -rolled with a heavy, rubber - tired piece of equipment, to identify soft or yielding areas that may require repair prior to placing any structural fill and prior to placing the pavement base course. We should be retained to observe the proof - rolling and to recommend repairs prior to placement of the asphalt or hard surfaces. The hard surface section should be thickened and reinforced with rebar where applicable to further reduce the effects of settlement due to the loose/soft soils, but potential long-term cracking should still be expected if any undocumented fill is left in place below the upper crushed rock backfill. NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation NGA File No. 1083719 Pickering 6r' Ave South Residential Development March 21, 2019 Edmonds, Washington Page 11 Utilities We recommend that underground utilities be bedded with a minimum six inches of pea gravel prior to backfilling the trench with on -site or imported material. Trenches within settlement sensitive areas should be compacted to 95% of the modified proctor as described in the Structural Fill subsection of this report. Trench backfill should be compacted to a minimum of 95% of the modified proctor maximum dry density. Trenches located in non-structural areas and five feet below roadway subgrade should be compacted to a minimum 90% of the maximum dry density. The trench backfill should be tested. Site Drainage Infiltration: The subsurface soils generally consisted of undocumented fill soils underlain by silty sand with varying amounts of gravel that we interpreted as native glacial deposits to the depths explored. The 2014 WSDOE Stormwater Management Manual for Western Washin tg_on was utilized to determine the long term design infiltration rate of the site soils. In accordance with this manual, on -site infiltration testing consisting of the Small Scale Pilot Infiltration Test (Small PIT) was used to determine the long- term design infiltration rates. We conducted two Small PITs within Infiltration Pit 1 and Infiltration Pit 2 located within the northeastern and central portions of the site respectively, as shown on the attached Site Plan in Figure 2. These tests were performed in The tests were conducted within pits that measured 6.0-feet long by 3.3- feet wide by 8.5-feet deep and 5.0-feet long by 2.5-feet wide by 8.0-feet deep for Infiltration Pit 1 and 2 respectively. The pits were filled with 12-inches of water at the beginning of the day and we began the soaking period of the PIT for approximately 6 hours. At this time, the water flow rate into the holes was monitored with a Great Plains Industries (GPI) TM 075 water flow meter for the pre-soak period. At the conclusion of the pre-soak period, we observed the water level for an additional hour. During the pre-soak period and additional hour, we did not observe any water level movement with no additional water added. Based on the results of our onsite infiltration testing and the relatively dense and silty nature of the native glacial soils encountered at depth, it is our opinion that traditional methods of stormwater infiltration are not feasible within the site. Low impact design infiltration systems such as pervious pavements, rain gardens and/or bio-retention systems may be feasible within the site. This should be further discussed with the project civil engineer. Any low -impact design systems should be designed with an incorporated overflow component that is directed to discharge into an approved off -site point of discharge. NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation NGA File No. 1083719 Pickering 6r' Ave South Residential Development March 21, 2019 Edmonds, Washington Page 12 We recommend that any proposed low -impact design infiltration systems be placed as to not negatively impact any proposed or existing nearby structures and also meet all required setbacks from existing property lines, structures, and sensitive areas as discussed in the drainage manual. In general, infiltration systems should not be located within the fill areas associated with site grading or retaining wall backfill as such condition could lead to failures of the placed fills and/or retaining structures. We should be retained to evaluate the infiltration system design and installation during construction. Surface Drainage: The finished ground surface should be graded such that stormwater is directed to an approved stormwater collection system. Water should not be allowed to stand in any areas where footings, slabs, or pavements are to be constructed. Final site grades should allow for drainage away from the residences. We suggest that the finished ground be sloped at a minimum gradient of three percent, for a distance of at least 10 feet away from the residences. Surface water should be collected by permanent catch basins and drain lines, and be discharged into an approved discharge system. Subsurface Drainage: If groundwater is encountered during construction, we recommend that the contractor slope the bottom of the excavation and collect the water into ditches and small sump pits where the water can be pumped out and routed into a permanent storm drain. We recommend the use of footing drains around the structures. Footing drains should be installed at least one foot below planned finished floor elevation. The drains should consist of a minimum 4-inch- diameter, rigid, slotted or perforated, PVC pipe surrounded by free -draining material wrapped in a filter fabric. We recommend that the free -draining material consist of an 18-inch-wide zone of clean (less than three -percent fines), granular material placed along the back of walls. Pea gravel is an acceptable drain material. The free -draining material should extend up the wall to one foot below the finished surface. The top foot of backfill should consist of impermeable soil placed over plastic sheeting or building paper to minimize surface water or fines migration into the footing drain. Footing drains should discharge into tightlines leading to an approved collection and discharge point with convenient cleanouts to prolong the useful life of the drains. Roof drains should not be connected to wall or footing drains. CONSTRUCTION MONITORING We should be retained to provide construction monitoring services during the earthwork phase of the project to evaluate subgrade conditions, temporary cut conditions, fill compaction, and drainage system installation. NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation NGA File No. 1083719 Pickering 6r' Ave South Residential Development March 21, 2019 Edmonds, Washington Page 13 USE OF THIS REPORT NGA has prepared this report for Mr. Chris Pickering and his agents, for use in the planning and design of the development on this site only. The scope of our work does not include services related to construction safety precautions and our recommendations are not intended to direct the contractors' methods, techniques, sequences, or procedures, except as specifically described in our report for consideration in design. There are possible variations in subsurface conditions between the explorations and also with time. Our report, conclusions, and interpretations should not be construed as a warranty of subsurface conditions. A contingency for unanticipated conditions should be included in the budget and schedule. We recommend that NGA be retained to provide monitoring and consultation services during construction to confirm that the conditions encountered are consistent with those indicated by the explorations, to provide recommendations for design changes should the conditions revealed during the work differ from those anticipated, and to evaluate whether or not earthwork and foundation installation activities comply with contract plans and specifications. We should be contacted a minimum of one week prior to construction activities and could attend pre -construction meetings if requested. Within the limitations of scope, schedule, and budget, our services have been performed in accordance with generally accepted geotechnical engineering practices in effect in this area at the time this report was prepared. No other warranty, expressed or implied, is made. Our observations, findings, and opinions are a means to identify and reduce the inherent risks to the owner. rss NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation Pickering 6r' Ave South Residential Development Edmonds, Washington NGA File No. 1083719 March 21, 2019 Page 14 It has been a pleasure to provide service to you on this project. If you have any questions or require further information, please call. Sincerely, NELSON GEOTECHNICAL ASSOCIATES, INC. e � Alex B. Rinaldi, GIT Staff Geologist II zof washi �S? co 7 2883� /DSQd G@OLO LEE S. BELLAH Lee S. Bellah, LG Project Geologist Maher A. Shebl, PhD, PE, M.ASCE Senior Engineer ABR:LSB:MAS:dy Four Figures Attached NELSON GEOTECHNICAL ASSOCIATES, INC. VICINITY MAP N Not to Scale f3rackett's OF EDMONDS Landing _ Shoreline Holy Rosary Church Calci 4131V Sanctuary.. Edmonds Center Wt."°N Glen S'[ In Ferry For the Arts Brackett's Daley 51 r 5CB ns'ry t:l Landing North cam.. 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N G A 1083719 Residential Development 1 3/12/19 Original DPN ABR Z h' GEOTECHNICAL ENGINEERS & GEOLOGISTS it Figure 1 •`i Vicinity Map WooclinvilleOffice East Wenatchee Office 17311-135th Ave. NE, A-500 5526 Industry Lane, #2 Woodinville. WA98072 East Wenatchee, WA 98802 N (425)486-1669/Fax:481-2510—nelsongeotech.com (509)665-7696/Fax : 665-7692 Z Site Plan Maple St aN � � I ! U d t ,CW Conc �3fo I \ Picket —Fence (t o / 0.11' 59.97' Site BM P2 V \ 0 9 .87 I/ goo' INF-1 / NEI iey 8.1' I I Fli I � I ° I ' 3 I 0.95' r o N Existing o 340 0,�� o Residence `n EM n x . •.' w N. - -- -i 3 �- c D I i INF-2 v0 Lot 18 0 S-, °L 19 —m—Lot 20 � '� U o f v I o ° o U' V a CW T1 TP-1 I Z o ` h Wood Fenc (,c�nc. T6(D I Wire Fence X T10 O Existing �� I M Garage TP-2 00 T160 I `n F — I LL5.8 P 2' e 1 �J S 89e58'45" E--- ---59. ISO )5.28 f s. l LEGEND Property line INr 0 20 40 ' Number and approximate location of infiltration test pit TP-1 Scale: 1 inch = 20 feet a I Number and approximate _ location of test pit Reference: Site Plan based on a plan dated September 8, 2014 titled "Topographic Survey," prepared by Emerald Land Surveying. Inc. a 0 Project Number NELSON GEOTECHNICAL No. Date Revision By t CK ry Pickering 6th Avenue South ASSOCIATES, INC. NC7A ° 1083719 Residential Development sns,s Original DPN LSB GEOTECHNICAL ENGINEERS & GEOLOGISTS Z Figure 2 Site Plan Wootlinville06" East Wenatchee Office , 7 W -,151h Ave. NE, A.500 5526 Industry L— $2 WooCinvJle, WA98072 Earl Wenatchee, WA 98802 (4251486.1889 f Fax: 481.2510 nc•Iswg<roI-h com (509) 665-7696 f Fax_ 665.7692 Z UNIFIED SOIL CLASSIFICATION SYSTEM GROUP MAJOR DIVISIONS GROUP NAME SYMBOL CLEAN GW WELL -GRADED, FINE TO COARSE GRAVEL COARSE- GRAVEL GRAVEL GP POORLY -GRADED GRAVEL GRAINED MORE THAN 50 % GRAVEL GM SILTY GRAVEL OF COARSE FRACTION RETAINED ON SOILS NO.4 SIEVE WITH FINES GC CLAYEY GRAVEL SAND CLEAN SW WELL -GRADED SAND, FINE TO COARSE SAND SAND SP POORLY GRADED SAND MORE THAN 50 % RETAINED ON MORE THAN 50 % NO. 200 SIEVE OF COARSE FRACTION SAND SM SILTY SAND PASSES NO. 4 SIEVE WITH FINES SC CLAYEY SAND FINE - SILT AND CLAY ML SILT INORGANIC GRAINED LIQUID LIMIT CL CLAY LESS THAN 50 % SOILS ORGANIC OL ORGANIC SILT, ORGANIC CLAY SILT AND CLAY MH SILT OF HIGH PLASTICITY, ELASTIC SILT INORGANIC MORE THAN 50 % PASSES LIQUID LIMIT CH CLAY OF HIGH PLASTICITY, FAT CLAY NO. 200 SIEVE 50 % OR MORE ORGANIC OH ORGANIC CLAY, ORGANIC SILT HIGHLY ORGANIC SOILS PT PEAT NOTES: 1) Field classification is based on visual SOIL MOISTURE MODIFIERS: examination of soil in general accordance with ASTM D 2488-93. Dry - Absence of moisture, dusty, dry to the touch 2) Soil classification using laboratory tests is based on ASTM D 2488-93. Moist - Damp, but no visible water. 3) Descriptions of soil density or Wet - Visible free water or saturated, consistency are based on usually soil is obtained from interpretation of blowcount data, below water table visual appearance of soils, and/or test data. Project Number NELSON GEOTECHNICAL No. Date Revision By CK 1083719 Pickering 6th Avenue South ASSOCIATES, INC. N G A Residential Development GEOTECHNICAL ENGINEERS & GEOLOGISTS 1 3/12/19 Original DPN ABR Figure 3 Soil Classification Chart "'°°°`""veOffice East WenatcheeLane, 811-1851h Ave. 9 A-500 5526Industry Lane,88 W WA 98072 East Wenatchee, WA 98802 ootlinville, (425)486-1669/Fax:481-2510—nelsongeotech.com (509)665-7696/Fax:665-7692 LOG OF EXPLORATION DEPTH (FEET) USC SOIL DESCRIPTION INFILTRATION PIT ONE 0.0 - 5.0 GRASS UNDERLAIN BY DARK BROWN TO LIGHT BROWN, SILTY FINE TO MEDIUM SAND WITH GRAVEL, ROOTS, AND ORGANICS (LOOSE TO MEDIUM DENSE, MOIST) (UNDCOUMENTED FILL) 5.0 - 8.5 SM GRAY, SILTY FINE TO MEDIUM SAND WITH GRAVEL, COBBLES, AND TRACE IRON -OXIDE STAINING (MEDIUM DENSE TO DENSE, MOIST) SAMPLE WAS NOT COLLECTED MINOR GROUNDWATER SEEPAGE WAS ENCOUNTERED AT 8.0 FEET TEST PIT CAVING WAS NOT ENCOUNTERED TEST PIT WAS COMPLETED AT 8.5 FEET ON 2/21/2019 INFILTRATION PIT TWO 0.0 - 5.5 DARK BROWN TO ORANGE -BROWN, SILTY FINE TO MEDIUM SAND WITH GRAVEL, ROOTS, ORGANICS, AND TRACE IRON -OXIDE STAINING (LOOSE TO MEDIUM DENSE, MOIST) (UNDOCUMENTED FILL) 5.5-8.0 SM GRAY WELL -CEMENTED SILTY FINE TO MEDIUM SAND WITH GRAVEL, COBBLES, AND TRACE IRON -OXIDE STAINING (MEDIUM DENSE TO DENSE, MOIST) SAMPLE WAS COLLECTED AT 7.5 FEET GROUNDWATER SEEPAGE WAS ENCOUNTERED FROM 7.0 TO 8.0 FEET TEST PIT CAVING WAS NOT ENCOUNTERED TEST PIT WAS COMPLETED AT 7.5 FEET ON 2/21/2019 TEST PIT ONE 0.0-4.8 GRASS UNDERLAIN BY DARK BROWN TO LIGHT BROWN, SILTY FINE TO MEDIUM SAND WITH GRAVEL, ROOTS, AND ORGANICS (LOOSE TO MEDIUM DENSE, MOIST) (UNDCOUMENTED FILL) 4.8 - 7.6 SM GRAY WELL -CEMENTED SILTY FINE TO MEDIUM SAND WITH GRAVEL (MEDIUM DENSE TO DENSE, MOIST) SAMPLE WAS COLLECTED AT 7.0 FEET GROUNDWATER SEEPAGE WAS NOT ENCOUNTERED TEST PIT CAVING WAS NOT ENCOUNTERED TEST PIT WAS COMPLETED AT 7.6 FEET ON 2/21/2019 TEST PIT TWO 0.0-5.4 GRASS UNDERLAIN BY DARK BROWN TO ORANGE -BROWN, SILTY FINE TO MEDIUM SAND WITH GRAVEL, ROOTS, AND ORGANICS (LOOSE TO MEDIUM DENSE, MOIST) (UNDCOUMENTED FILL) 5.4 - 9.0 SM GRAY, SILTY FINE TO MEDIUM SAND WITH GRAVEL AND TRACE COBBLES (MEDIUM DENSE TO DENSE, MOIST) SAMPLE WAS COLLECTED AT 9.0 FEET GROUNDWATER SEEPAGE WAS NOT ENCOUNTERED TEST PIT CAVING WAS NOT ENCOUNTERED TEST PIT WAS COMPLETED AT 9.0 FEET ON 2/21/2019 ABR:LSB NELSON GEOTECHNICAL ASSOCIATES, INC. FILE NO 1083719 FIGURE 4 Stormwater Site Plans — Rev 2 302 61h Ave S Edmonds APPENDIX B WWHM Summary June2021 20210608_302 6th Ave S Edmonds —Drainage Report Rev 2 WWHM2012 PROJECT REPORT THIS REPORT IS FOR THE PURPOSE OF SHOWING THAT THE 100-YR DEVELOPED PEAK FLOW IS LESS THAN A 0.15-CFS INCREASE FROM THE PREDEVELOPED SITE 100-YR PEAK FLOW General Model Information Project Name: Pickering Edmonds Site Name: Pickering Edmonds Site Address: 302 6th Ave S City: Edmonds Report Date: 6/10/2021 MGS Region: Puget East Data Start: 1901 /10/1 Data End: 2058/09/30 Timestep: 15 Minute DOT Data Number03 Version Date: 2019/09/13 Version: 4.2.17 POC Thresholds Low Flow Threshold for POC1: 50 Percent of the 2 Year High Flow Threshold for POC1: 50 Year Pickering Edmonds 6/10/2021 12:27:14 PM Page 2 Landuse Basin Data Predeveloped Land Use Basin 1 Bypass: No GroundWater: No Pervious Land Use acre C, Forest, Mod 0.22 Pervious Total 0.22 Impervious Land Use acre Impervious Total 0 Basin Total 0.22 Element Flows To: Surface Interflow Groundwater Pickering Edmonds 6/10/2021 12:27:14 PM Page 3 Mitigated Land Use Basin 1 Bypass: No GroundWater: No Pervious Land Use acre C, Lawn, Mod 0.06 Pervious Total 0.06 Impervious Land Use acre ROADS MOD 0.03 ROOF TOPS FLAT 0.07 DRIVEWAYS MOD 0.03 SIDEWALKS MOD 0.03 Impervious Total 0.16 TOTAL SITE AREA + ROW IMPROVEMENTS Basin Total 0.22 Element Flows To: Surface Interflow Groundwater Pickering Edmonds 6/10/2021 12:27:14 PM Page 4 Routing Elements Predeveloped Routing Pickering Edmonds 6/10/2021 12:27:14 PM Page 5 Mitigated Routing Pickering Edmonds 6/10/2021 12:27:14 PM Page 6 Analysis Results POC 1 0.01 U 0.m J 0.00 0.00 Percent Time Exceetlir�g ,.0 o, o ao, lnri . —1 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #1 Total Pervious Area: 0.22 Total Impervious Area: 0 Mitigated Landuse Totals for POC #1 Total Pervious Area: 0.06 Total Impervious Area: 0.16 Flow Frequency Method: Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.003733 5 year 0.005794 10 year 0.006911 25 year 0.008048 <_ LESS THAN 0.15 100 year 0.009279 1 CFS INCREASE Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.051561 5 year 0.071002 10 year 0.086012 25 year 0.107589 50 year 0.125684 100 year 0.145624 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1902 0.005 0.058 1903 0.002 0.064 1904 0.003 0.076 1905 0.002 0.036 1906 0.001 0.041 1907 0.006 0.049 1908 0.004 0.042 1909 0.004 0.053 1910 0.006 0.048 1911 0.003 0.054 Pickering Edmonds 6/10/2021 12:27:14 PM Page 7 1912 0.011 0.107 1913 0.006 0.041 1914 0.001 0.161 1915 0.002 0.034 1916 0.003 0.063 1917 0.001 0.031 1918 0.004 0.049 1919 0.003 0.030 1920 0.003 0.045 1921 0.004 0.034 1922 0.004 0.052 1923 0.003 0.043 1924 0.002 0.070 1925 0.002 0.031 1926 0.003 0.062 1927 0.004 0.049 1928 0.003 0.039 1929 0.006 0.069 1930 0.003 0.080 1931 0.004 0.034 1932 0.002 0.041 1933 0.003 0.040 1934 0.008 0.067 1935 0.003 0.034 1936 0.005 0.050 1937 0.004 0.061 1938 0.004 0.034 1939 0.000 0.046 1940 0.003 0.082 1941 0.003 0.081 1942 0.005 0.062 1943 0.002 0.057 1944 0.004 0.080 1945 0.004 0.061 1946 0.003 0.047 1947 0.002 0.036 1948 0.008 0.045 1949 0.006 0.083 1950 0.003 0.039 1951 0.004 0.075 1952 0.011 0.091 1953 0.010 0.082 1954 0.003 0.045 1955 0.003 0.041 1956 0.002 0.034 1957 0.004 0.043 1958 0.010 0.053 1959 0.006 0.052 1960 0.002 0.039 1961 0.006 0.125 1962 0.003 0.049 1963 0.002 0.033 1964 0.003 0.121 1965 0.008 0.069 1966 0.001 0.041 1967 0.003 0.061 1968 0.004 0.044 1969 0.003 0.039 Pickering Edmonds 6/10/2021 12:28:20 PM Page 8 1970 0.004 0.053 1971 0.008 0.049 1972 0.005 0.207 1973 0.006 0.095 1974 0.003 0.067 1975 0.009 0.076 1976 0.004 0.074 1977 0.002 0.031 1978 0.007 0.053 1979 0.002 0.053 1980 0.004 0.060 1981 0.004 0.063 1982 0.002 0.042 1983 0.006 0.059 1984 0.002 0.054 1985 0.004 0.066 1986 0.003 0.032 1987 0.006 0.060 1988 0.004 0.035 1989 0.004 0.046 1990 0.005 0.041 1991 0.003 0.060 1992 0.005 0.056 1993 0.004 0.069 1994 0.008 0.045 1995 0.002 0.032 1996 0.008 0.048 1997 0.004 0.041 1998 0.004 0.049 1999 0.000 0.058 2000 0.003 0.051 2001 0.002 0.061 2002 0.005 0.084 2003 0.004 0.045 2004 0.004 0.063 2005 0.005 0.133 2006 0.003 0.049 2007 0.003 0.063 2008 0.004 0.050 2009 0.002 0.041 2010 0.002 0.051 2011 0.002 0.050 2012 0.003 0.047 2013 0.003 0.052 2014 0.002 0.041 2015 0.007 0.118 2016 0.001 0.042 2017 0.006 0.075 2018 0.010 0.053 2019 0.011 0.080 2020 0.003 0.062 2021 0.005 0.052 2022 0.002 0.071 2023 0.004 0.085 2024 0.009 0.119 2025 0.003 0.065 2026 0.006 0.064 2027 0.003 0.066 Pickering Edmonds 6/10/2021 12:28:20 PM Page 9 2028 0.001 0.028 2029 0.004 0.037 2030 0.008 0.084 2031 0.002 0.028 2032 0.002 0.043 2033 0.002 0.044 2034 0.002 0.036 2035 0.009 0.050 2036 0.005 0.040 2037 0.001 0.056 2038 0.005 0.051 2039 0.000 0.093 2040 0.002 0.043 2041 0.003 0.047 2042 0.009 0.064 2043 0.004 0.067 2044 0.006 0.048 2045 0.004 0.040 2046 0.004 0.037 2047 0.003 0.050 2048 0.004 0.042 2049 0.003 0.066 2050 0.002 0.038 2051 0.004 0.065 2052 0.002 0.049 2053 0.004 0.042 2054 0.005 0.094 2055 0.002 0.050 2056 0.001 0.067 2057 0.002 0.033 2058 0.003 0.062 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.0113 0.2074 2 0.0113 0.1614 3 0.0110 0.1334 4 0.0104 0.1248 5 0.0102 0.1211 6 0.0097 0.1188 7 0.0094 0.1178 8 0.0091 0.1071 9 0.0088 0.0955 10 0.0086 0.0940 11 0.0085 0.0926 12 0.0082 0.0908 13 0.0081 0.0849 14 0.0080 0.0837 15 0.0076 0.0836 16 0.0076 0.0834 17 0.0075 0.0822 18 0.0074 0.0819 19 0.0074 0.0808 20 0.0064 0.0805 21 0.0064 0.0800 22 0.0063 0.0798 23 0.0062 0.0760 Pickering Edmonds 6/10/2021 12:28:20 PM Page 10 24 0.0061 0.0758 25 0.0060 0.0749 26 0.0060 0.0748 27 0.0060 0.0739 28 0.0059 0.0709 29 0.0058 0.0700 30 0.0058 0.0690 31 0.0057 0.0690 32 0.0056 0.0686 33 0.0053 0.0672 34 0.0052 0.0671 35 0.0052 0.0671 36 0.0052 0.0666 37 0.0051 0.0665 38 0.0050 0.0664 39 0.0050 0.0660 40 0.0049 0.0653 41 0.0049 0.0649 42 0.0047 0.0641 43 0.0047 0.0640 44 0.0046 0.0638 45 0.0045 0.0634 46 0.0043 0.0634 47 0.0043 0.0632 48 0.0043 0.0628 49 0.0042 0.0625 50 0.0042 0.0624 51 0.0042 0.0621 52 0.0041 0.0620 53 0.0041 0.0613 54 0.0041 0.0608 55 0.0041 0.0607 56 0.0041 0.0607 57 0.0041 0.0604 58 0.0040 0.0602 59 0.0040 0.0597 60 0.0040 0.0586 61 0.0040 0.0581 62 0.0040 0.0580 63 0.0039 0.0565 64 0.0038 0.0563 65 0.0038 0.0562 66 0.0038 0.0544 67 0.0038 0.0541 68 0.0037 0.0534 69 0.0037 0.0531 70 0.0037 0.0529 71 0.0036 0.0526 72 0.0036 0.0526 73 0.0036 0.0525 74 0.0036 0.0524 75 0.0036 0.0524 76 0.0036 0.0520 77 0.0036 0.0516 78 0.0035 0.0514 79 0.0035 0.0512 80 0.0035 0.0509 81 0.0034 0.0505 Pickering Edmonds 6/10/2021 12:28:20 PM Page 11 82 0.0034 0.0504 83 0.0034 0.0502 84 0.0034 0.0500 85 0.0034 0.0497 86 0.0034 0.0496 87 0.0033 0.0494 88 0.0033 0.0493 89 0.0033 0.0493 90 0.0033 0.0491 91 0.0033 0.0490 92 0.0033 0.0489 93 0.0032 0.0488 94 0.0032 0.0488 95 0.0032 0.0485 96 0.0031 0.0483 97 0.0030 0.0477 98 0.0030 0.0471 99 0.0030 0.0467 100 0.0030 0.0467 101 0.0030 0.0460 102 0.0029 0.0458 103 0.0029 0.0453 104 0.0028 0.0451 105 0.0028 0.0450 106 0.0028 0.0448 107 0.0028 0.0446 108 0.0027 0.0441 109 0.0027 0.0435 110 0.0027 0.0433 111 0.0027 0.0429 112 0.0027 0.0429 113 0.0026 0.0427 114 0.0026 0.0423 115 0.0025 0.0422 116 0.0025 0.0418 117 0.0025 0.0417 118 0.0025 0.0417 119 0.0024 0.0415 120 0.0024 0.0414 121 0.0024 0.0413 122 0.0023 0.0413 123 0.0023 0.0411 124 0.0022 0.0411 125 0.0022 0.0407 126 0.0022 0.0406 127 0.0022 0.0405 128 0.0021 0.0403 129 0.0020 0.0401 130 0.0020 0.0400 131 0.0020 0.0393 132 0.0019 0.0393 133 0.0019 0.0390 134 0.0019 0.0390 135 0.0018 0.0383 136 0.0018 0.0371 137 0.0018 0.0370 138 0.0018 0.0364 139 0.0018 0.0363 Pickering Edmonds 6/10/2021 12:28:20 PM Page 12 140 0.0018 0.0363 141 0.0017 0.0346 142 0.0017 0.0344 143 0.0016 0.0341 144 0.0016 0.0339 145 0.0016 0.0339 146 0.0015 0.0336 147 0.0015 0.0336 148 0.0014 0.0331 149 0.0013 0.0327 150 0.0013 0.0319 151 0.0012 0.0316 152 0.0010 0.0312 153 0.0009 0.0309 154 0.0009 0.0305 155 0.0004 0.0299 156 0.0003 0.0280 157 0.0002 0.0276 Pickering Edmonds 6/10/2021 12:28:20 PM Page 13 Duration Flows Flow(cfs) Predev Mit Percentage Pass/Fail 0.0019 53305 420804 789 Fail 0.0019 49061 412106 839 Fail 0.0020 45130 403683 894 Fail 0.0021 41772 395481 946 Fail 0.0021 38656 387884 1003 Fail 0.0022 35832 380452 1061 Fail 0.0023 33228 373351 1123 Fail 0.0024 30916 366414 1185 Fail 0.0024 28879 359753 1245 Fail 0.0025 26953 353312 1310 Fail 0.0026 25169 346927 1378 Fail 0.0026 23435 340926 1454 Fail 0.0027 21882 335036 1531 Fail 0.0028 20347 329366 1618 Fail 0.0028 18921 323806 1711 Fail 0.0029 17671 318411 1801 Fail 0.0030 16510 313181 1896 Fail 0.0030 15453 308006 1993 Fail 0.0031 14451 302997 2096 Fail 0.0032 13504 298207 2208 Fail 0.0033 12607 293418 2327 Fail 0.0033 11792 288628 2447 Fail 0.0034 11060 284059 2568 Fail 0.0035 10421 279600 2683 Fail 0.0035 9837 275196 2797 Fail 0.0036 9309 270847 2909 Fail 0.0037 8786 266773 3036 Fail 0.0037 8291 262590 3167 Fail 0.0038 7850 258571 3293 Fail 0.0039 7393 254552 3443 Fail 0.0039 7035 250699 3563 Fail 0.0040 6667 246955 3704 Fail 0.0041 6342 243322 3836 Fail 0.0042 6034 239689 3972 Fail 0.0042 5742 236055 4111 Fail 0.0043 5474 232532 4247 Fail 0.0044 5217 229009 4389 Fail 0.0044 4988 225541 4521 Fail 0.0045 4756 222293 4673 Fail 0.0046 4539 219155 4828 Fail 0.0046 4333 215797 4980 Fail 0.0047 4124 212604 5155 Fail 0.0048 3939 209521 5319 Fail 0.0048 3770 206383 5474 Fail 0.0049 3631 203466 5603 Fail 0.0050 3491 200603 5746 Fail 0.0051 3368 197740 5871 Fail 0.0051 3253 194933 5992 Fail 0.0052 3145 192180 6110 Fail Pickering Edmonds 6/10/2021 12:28:20 PM Page 14 0.0056 2586 176436 6822 Fail 0.0057 2491 173904 6981 Fail 0.0057 2389 171537 7180 Fail 0.0058 2278 169224 7428 Fail 0.0059 2180 166802 7651 Fail 0.0060 2080 164490 7908 Fail 0.0060 1997 162178 8121 Fail 0.0061 1928 159921 8294 Fail 0.0062 1863 157719 8465 Fail 0.0062 1790 155462 8685 Fail 0.0063 1717 153370 8932 Fail 0.0064 1664 151223 9087 Fail 0.0064 1595 149131 9349 Fail 0.0065 1535 147149 9586 Fail 0.0066 1479 145167 9815 Fail 0.0066 1418 143131 10093 Fail 0.0067 1360 141259 10386 Fail 0.0068 1298 139332 10734 Fail 0.0069 1242 137515 11072 Fail 0.0069 1188 135589 11413 Fail 0.0070 1146 133717 11668 Fail 0.0071 1100 131900 11990 Fail 0.0071 1045 130084 12448 Fail 0.0072 1000 128432 12843 Fail 0.0073 953 126726 13297 Fail 0.0073 916 124964 13642 Fail 0.0074 877 123257 14054 Fail 0.0075 830 121551 14644 Fail 0.0075 788 119844 15208 Fail 0.0076 754 118248 15682 Fail 0.0077 710 116651 16429 Fail 0.0078 663 115055 17353 Fail 0.0078 627 113514 18104 Fail 0.0079 595 111972 18818 Fail 0.0080 554 110541 19953 Fail 0.0080 515 109110 21186 Fail 0.0081 461 107623 23345 Fail 0.0082 421 106192 25223 Fail 0.0082 392 104761 26724 Fail 0.0083 360 103329 28702 Fail 0.0084 334 102008 30541 Fail 0.0084 306 100577 32868 Fail 0.0085 285 99256 34826 Fail 0.0086 264 97934 37096 Fail 0.0087 247 96613 39114 Fail 0.0087 233 95237 40874 Fail The development has an increase in flow durations from 1/2 Predeveloped 2 year flow to the 2 year flow or more than a 10% increase from the 2 year to the 50 year flow. The development has an increase in flow durations for more than 50% of the flows for the range of the duration analysis. Pickering Edmonds 6/10/2021 12:28:20 PM Page 15 Water Quality Water Quality BMP Flow and Volume for POC #1 On-line facility volume: 0 acre-feet On-line facility target flow: 0 cfs. Adjusted for 15 min: 0 cfs. Off-line facility target flow: 0 cfs. Adjusted for 15 min: 0 cfs. Pickering Edmonds 6/10/2021 12:28:20 PM Page 16 LID Report LID Technique Used for Total Volume Volume Infiltration Cumulative Percent Water Quality Percent Comment Treatment? Needs Through Volume Volume Volume Water Quality Treatment Facility (ac-ft) Infiltration Infiltrated Treated (ac-ft) (ac-ft) Credit Total Volume Infiltrated 0.00 0.00 0.00 0.00 0.00 0% No Treat. Credit Compliance with LID Duration Standard 8% of 2-yr to 50% of Analysis 2 yr Result = Failed Pickering Edmonds 6/10/2021 12:28:20 PM Page 17 Model Default Modifications Total of 0 changes have been made. PERLND Changes No PERLND changes have been made. IMPLND Changes No IMPLND changes have been made. Pickering Edmonds 6/10/2021 12:28:39 PM Page 18 Appendix Predeveloped Schematic Basin 1 1 0.22ac Pickering Edmonds 6/10/2021 12:28:39 PM Page 19 Mitigated Schematic Basin 1 0.22ac Pickering Edmonds 6/10/2021 12:28:40 PM Page 20 Predeveloped UCI File RUN GLOBAL WWHM4 model simulation START 1901 10 01 END RUN INTERP OUTPUT LEVEL 3 0 RESUME 0 RUN 1 END GLOBAL 2058 09 30 FILES <File> <Un#> OPN SEQUENCE UNIT SYSTEM 1 <----------- File Name---- -------------------------->*** *** INGRP INDELT 00:15 PERLND 11 COPY 501 DISPLY 1 END INGRP END OPN SEQUENCE DISPLY DISPLY-INFO1 # - #<---------- Title ----------- >***TRAN PIVL DIG1 FIL1 1 Basin 1 MAX END DISPLY-INFO1 END DISPLY COPY TIMESERIES # - # NPT NMN *** 1 1 1 501 1 1 END TIMESERIES END COPY GENER OPCODE # # OPCD *** END OPCODE PARM # # K *** END PARM END GENER PERLND GEN-INFO PYR DIG2 FIL2 YRND 1 2 30 9 <PLS ><------- Name ------- >NBLKS Unit -systems Printer *** # - # User t-series Engl Metr *** in out *** 11 C, Forest, Mod 1 1 1 1 27 0 END GEN-INFO *** Section PWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC *** 11 0 0 1 0 0 0 0 0 0 0 0 0 END ACTIVITY PRINT -INFO <PLS > ***************** Print -flags ***************************** PIVL PYR # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC ********* 11 0 0 4 0 0 0 0 0 0 0 0 0 1 9 END PRINT -INFO Pickering Edmonds 6/10/2021 12:28:40 PM Page 21 PWAT-PARM1 <PLS > PWATER variable monthly parameter value flags *** # - # CSNO RTOP UZFG VCS VUZ VNN VIFW VIRC VLE INFC HWT *** 11 0 0 0 0 0 0 0 0 0 0 0 END PWAT-PARM1 PWAT-PARM2 <PLS > PWATER input info: Part 2 *** # - # ***FOREST LZSN INFILT LSUR SLSUR KVARY 11 0 4.5 0.08 400 0.1 0.5 END PWAT-PARM2 PWAT-PARM3 <PLS > PWATER input info: Part 3 # - # ***PETMAX PETMIN INFEXP 11 0 0 2 END PWAT-PARM3 PWAT-PARM4 <PLS > PWATER input info: Part 4 # - # CEPSC UZSN NSUR 11 0.2 0.5 0.35 END PWAT-PARM4 AGWRC 0.996 *** INFILD DEEPFR BASETP AGWETP 2 0 0 0 *** INTFW IRC LZETP *** 6 0.5 0.7 PWAT-STATEI <PLS > *** Initial conditions at start of simulation ran from 1990 to end of 1992 (pat 1-11-95) RUN 21 *** # - # *** CEPS SURS UZS IFWS LZS AGWS 11 0 0 0 0 2.5 1 END PWAT-STATEI END PERLND IMPLND GEN-INFO <PLS ><------- Name ------- > END GEN-INFO *** Section IWATER*** Unit -systems Printer *** User t-series Engl Metr *** in out *** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW IWAT SLD IWG IQAL *** END ACTIVITY PRINT -INFO <ILS > ******** Print -flags ******** PIVL PYR # - # ATMP SNOW IWAT SLD IWG IQAL ********* END PRINT -INFO IWAT-PARM1 <PLS > IWATER variable monthly parameter value flags *** # - # CSNO RTOP VRS VNN RTLI *** END IWAT-PARM1 IWAT-PARM2 <PLS > IWATER input info: Part 2 *** # - # *** LSUR SLSUR NSUR RETSC END IWAT-PARM2 IWAT-PARM3 <PLS > IWATER input info: Part 3 *** # - # ***PETMAX PETMIN END IWAT-PARM3 IWAT-STATEI <PLS > *** Initial conditions at start of simulation # - # *** RETS SURS END IWAT-STATEI GWVS 0 Pickering Edmonds 6/10/2021 12:28:40 PM Page 22 END IMPLND SCHEMATIC <-Source-> <Name> # Basin 1*** PERLND 11 PERLND 11 ******Routing****** END SCHEMATIC <--Area--> <-Target-> MBLK <-factor-> <Name> # Tbl# 0.22 COPY 501 12 0.22 COPY 501 13 NETWORK <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** COPY 501 OUTPUT MEAN 1 1 48.4 DISPLY 1 INPUT TIMSER 1 <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** END NETWORK RCHRES GEN-INFO RCHRES Name Nexits Unit Systems Printer *** # - #<------------------ >< --- > User T-series Engl Metr LKFG *** in out *** END GEN-INFO *** Section RCHRES*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # HYFG ADFG CNFG HTFG SDFG GQFG OXFG NUFG PKFG PHFG *** END ACTIVITY PRINT -INFO <PLS > ***************** Print -flags ******************* PIVL PYR # - # HYDR ADCA CONS HEAT SED GQL OXRX NUTR PLNK PHCB PIVL PYR ********* END PRINT -INFO HYDR-PARM1 RCHRES Flags for each HYDR Section *** # - # VC Al A2 A3 ODFVFG for each *** ODGTFG for each FUNCT for each FG FG FG FG possible exit *** possible exit possible exit * * * * * * * * * * * * * * *** END HYDR-PARM1 HYDR-PARM2 # - # FTABNO LEN DELTH STCOR KS DB50 *** <------ ><-------- ><--------><--------><--------><--------><--------> *** END HYDR-PARM2 HYDR-INIT RCHRES Initial conditions for each HYDR section *** # - # *** VOL Initial value of COLIND Initial value of OUTDGT *** ac-ft for each possible exit for each possible exit <------><-------- > <---><---><---><---><---> *** <---><---><---><---><---> END HYDR-INIT END RCHRES SPEC -ACTIONS END SPEC -ACTIONS FTABLES END FTABLES EXT SOURCES <-Volume-> <Member> SsysSgap<--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # tem strg<-factor->strg <Name> # # <Name> # # *** WDM 2 PREC ENGL 1 DIV PERLND 1 999 EXTNL PREC WDM 2 PREC ENGL 1 DIV IMPLND 1 999 EXTNL PREC Pickering Edmonds 6/10/2021 12:28:40 PM Page 23 WDM 1 EVAP ENGL 0.76 PERLND 1 999 EXTNL PETINP WDM 1 EVAP ENGL 0.76 IMPLND 1 999 EXTNL PETINP END EXT SOURCES EXT TARGETS <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Volume-> <Member> Tsys Tgap Amd *** <Name> # <Name> # #<-factor->strg <Name> # <Name> tem strg strg*** COPY 501 OUTPUT MEAN 1 1 48.4 WDM 501 FLOW ENGL REPL END EXT TARGETS MASS -LINK <Volume> <-Grp> <-Member-><--Mult--> <Target> <-Grp> <-Member->*** <Name> <Name> # #<-factor-> <Name> <Name> # #*** MASS -LINK 12 PERLND PWATER SURD 0.083333 COPY INPUT MEAN END MASS -LINK 12 MASS -LINK 13 PERLND PWATER IFWO 0.083333 COPY INPUT MEAN END MASS -LINK 13 END MASS -LINK END RUN Pickering Edmonds 6/10/2021 12:28:40 PM Page 24 Mitigated UC/ File RUN GLOBAL WWHM4 model simulation START 1901 10 01 END RUN INTERP OUTPUT LEVEL 3 0 RESUME 0 RUN 1 END GLOBAL 2058 09 30 FILES <File> <Un#> OPN SEQUENCE UNIT SYSTEM 1 <----------- File Name---- -------------------------->*** *** INGRP INDELT 00:15 PERLND 17 IMPLND 2 IMPLND 4 IMPLND 6 IMPLND 9 COPY 501 DISPLY 1 END INGRP END OPN SEQUENCE DISPLY DISPLY-INFO1 # - #<---------- Title ----------- >***TRAN PIVL DIG1 FIL1 1 Basin 1 MAX END DISPLY-INFO1 END DISPLY COPY TIMESERIES # - # NPT NMN *** 1 1 1 501 1 1 END TIMESERIES END COPY GENER OPCODE # # OPCD *** END OPCODE PARM # # K *** END PARM END GENER PERLND GEN-INFO PYR DIG2 FIL2 YRND 1 2 30 9 <PLS ><------- Name ------- >NBLKS Unit -systems Printer *** # - # User t-series Engl Metr *** in out *** 17 C, Lawn, Mod 1 1 1 1 27 0 END GEN-INFO *** Section PWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC *** 17 0 0 1 0 0 0 0 0 0 0 0 0 END ACTIVITY PRINT -INFO <PLS > ***************** Print -flags ***************************** PIVL PYR Pickering Edmonds 6/10/2021 12:28:40 PM Page 25 # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC ********* 17 0 0 4 0 0 0 0 0 0 0 0 0 1 9 END PRINT -INFO PWAT-PARM1 <PLS > PWATER variable monthly parameter value flags *** # - # CSNO RTOP UZFG VCS VUZ VNN VIFW VIRC VLE INFC HWT *** 17 0 0 0 0 0 0 0 0 0 0 0 END PWAT-PARM1 PWAT-PARM2 <PLS > PWATER input info: Part 2 *** # - # ***FOREST LZSN INFILT LSUR SLSUR KVARY 17 0 4.5 0.03 400 0.1 0.5 END PWAT-PARM2 PWAT-PARM3 <PLS > PWATER input info: Part 3 # - # ***PETMAX PETMIN INFEXP 17 0 0 2 END PWAT-PARM3 PWAT-PARM4 <PLS > PWATER input info: Part 4 # - # CEPSC UZSN NSUR 17 0.1 0.25 0.25 END PWAT-PARM4 AGWRC 0.996 *** INFILD DEEPFR BASETP AGWETP 2 0 0 0 *** INTFW IRC LZETP *** 6 0.5 0.25 PWAT-STATEl <PLS > *** Initial conditions at start of simulation ran from 1990 to end of 1992 (pat 1-11-95) RUN 21 *** # - # *** CEPS SURS UZS IFWS LZS AGWS 17 0 0 0 0 2.5 1 END PWAT-STATEI END PERLND IMPLND GEN-INFO <PLS ><------- Name ------- > 2 ROADS/MOD 4 ROOF TOPS/FLAT 6 DRIVEWAYS/MOD 9 SIDEWALKS/MOD END GEN-INFO *** Section IWATER*** Unit -systems Printer *** User t-series Engl Metr *** in out *** 1 1 1 27 0 1 1 1 27 0 1 1 1 27 0 1 1 1 27 0 ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW IWAT SLD IWG IQAL *** 2 0 0 1 0 0 0 4 0 0 1 0 0 0 6 0 0 1 0 0 0 9 0 0 1 0 0 0 END ACTIVITY PRINT -INFO <ILS > ******** Print -flags ******** PIVL PYR # - # ATMP SNOW IWAT SLD IWG IQAL ********* 2 0 0 4 0 0 0 1 9 4 0 0 4 0 0 0 1 9 6 0 0 4 0 0 0 1 9 9 0 0 4 0 0 0 1 9 END PRINT -INFO IWAT-PARM1 <PLS > IWATER variable monthly parameter value flags *** # - # CSNO RTOP VRS VNN RTLI *** 2 0 0 0 0 0 GWVS 0 Pickering Edmonds 6/10/2021 12:28:40 PM Page 26 4 0 0 0 0 0 6 0 0 0 0 0 9 0 0 0 0 0 END IWAT-PARM1 IWAT-PARM2 <PLS > IWATER input info: Part 2 *** # - # *** LSUR SLSUR NSUR RETSC 2 400 0.05 0.1 0.08 4 400 0.01 0.1 0.1 6 400 0.05 0.1 0.08 9 400 0.05 0.1 0.08 END IWAT-PARM2 IWAT-PARM3 <PLS > IWATER input info: Part 3 *** # - # ***PETMAX PETMIN 2 0 0 4 0 0 6 0 0 9 0 0 END IWAT-PARM3 IWAT-STATEI <PLS > *** Initial conditions at start of simulation # - # *** RETS SURS 2 0 0 4 0 0 6 0 0 9 0 0 END IWAT-STATEI END IMPLND SCHEMATIC <-Source-> <--Area--> <-Target-> MBLK *** <Name> # <-factor-> <Name> # Tbl# *** Basin 1*** PERLND 17 0.06 COPY 501 12 PERLND 17 0.06 COPY 501 13 IMPLND 2 0.03 COPY 501 15 IMPLND 4 0.07 COPY 501 15 IMPLND 6 0.03 COPY 501 15 IMPLND 9 0.03 COPY 501 15 ******Routing****** END SCHEMATIC NETWORK <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** COPY 501 OUTPUT MEAN 1 1 48.4 DISPLY 1 INPUT TIMSER 1 <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** END NETWORK RCHRES GEN-INFO RCHRES Name Nexits Unit Systems Printer *** # - #<------------------ >< --- > User T-series Engl Metr LKFG *** in out *** END GEN-INFO *** Section RCHRES*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # HYFG ADFG CNFG HTFG SDFG GQFG OXFG NUFG PKFG PHFG *** Pickering Edmonds 6/10/2021 12:28:40 PM Page 27 END ACTIVITY PRINT -INFO <PLS > ***************** Print -flags ******************* PIVL PYR # - # HYDR ADCA CONS HEAT SED GQL OXRX NUTR PLNK PHCB PIVL PYR ********* END PRINT -INFO HYDR-PARM1 RCHRES Flags for each HYDR Section *** # - # VC Al A2 A3 ODFVFG for each *** ODGTFG for each FUNCT for each FG FG FG FG possible exit *** possible exit possible exit * * * * * * * * * * * * * * *** END HYDR-PARM1 HYDR-PARM2 # - # FTABNO LEN DELTH STCOR KS DB50 *** <------ ><-------- ><--------><--------><--------><--------><--------> *** END HYDR-PARM2 HYDR-INIT RCHRES Initial conditions for each HYDR section *** # - # *** VOL Initial value of COLIND Initial value of OUTDGT *** ac-ft for each possible exit for each possible exit <------><-------- > <---><---><---><---><---> *** <---><---><---><---><---> END HYDR-INIT END RCHRES SPEC -ACTIONS END SPEC -ACTIONS FTABLES END FTABLES EXT SOURCES <-Volume-> <Member> SsysSgap<--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # tem strg<-factor->strg <Name> # # <Name> # # *** WDM 2 PREC ENGL 1 DIV PERLND 1 999 EXTNL PREC WDM 2 PREC ENGL 1 DIV IMPLND 1 999 EXTNL PREC WDM 1 EVAP ENGL 0.76 PERLND 1 999 EXTNL PETINP WDM 1 EVAP ENGL 0.76 IMPLND 1 999 EXTNL PETINP END EXT SOURCES EXT TARGETS <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Volume-> <Member> Tsys Tgap Amd *** <Name> # <Name> # #<-factor->strg <Name> # <Name> tem strg strg*** COPY 1 OUTPUT MEAN 1 1 48.4 WDM 701 FLOW ENGL REPL COPY 501 OUTPUT MEAN 1 1 48.4 WDM 801 FLOW ENGL REPL END EXT TARGETS MASS -LINK <Volume> <-Grp> <-Member-><--Mult--> <Target> <Name> <Name> # #<-factor-> <Name> MASS -LINK 12 PERLND PWATER SURO 0.083333 COPY END MASS -LINK 12 MASS -LINK 13 PERLND PWATER IFWO 0.083333 COPY END MASS -LINK 13 MASS -LINK 15 IMPLND IWATER SURD 0.083333 COPY END MASS -LINK 15 END MASS -LINK END RUN <-Grp> <-Member->*** <Name> # #*** INPUT MEAN INPUT MEAN INPUT MEAN Pickering Edmonds 6/10/2021 12:28:40 PM Page 28 Predeveloped HSPF Message File Pickering Edmonds 6/10/2021 12:28:40 PM Page 29 Mitigated HSPF Message File Pickering Edmonds 6/10/2021 12:28:40 PM Page 30 Disclaimer Legal Notice 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. Clear Creek Solutions, Inc. 6200 Capitol Blvd. Ste F Olympia, WA. 98501 Toll Free 1(866)943-0304 Local (360)943-0304 www.clearcreeksolutions.com Pickering Edmonds 6/10/2021 12:28:40 PM Page 31 Stormwater Site Plans — Rev 2 302 61h Ave S Edmonds APPENDIX C Operation and Maintenance Manual June2021 20210608_302 6th Ave S Edmonds —Drainage Report Rev 2 302 6" Ave S — Edmonds Townhouses Operation and Maintenance Manual Person or Organization Responsible for Maintenance of the On -Site Storm System: Chris Pickering 302 6th Ave S Edmonds, WA 98020 The Location Where the Operation and Maintenance Manual is to be Kept: 302 6th Ave S Edmonds, WA 98020 *Note: The manual and maintenance activity log must be made available to the City of Edmonds for inspection purposes. Description of On -Site Storm System The on -site storm system for the 302 6th Ave S townhouses consists of 4-12" storm drain pipe, four bioretention planter boxes, a detention tank, and Type I & Type II catch basins. Stormwater runoff from the proposed 3-unit townhouse building will be collected in a gutter and downspout system and routed to either a bioretention planter box or directly into the onsite conveyance system. Any runoff from the driveway will be collected in Type 1 catch basins. An elevated concrete parking area from the alley south of the site will be routed to a bioretention planter box. Any overflows from the bioretention planter boxes, driveway, or walkways, as well as approximately 857 SF of roof area bypassing the bioretention planter boxes, will be conveyed to a 28' detention pipe at the north side of the site prior to gravity flowing to the City's storm system in Maple St. The proposed bioretention planter boxes, detention tank, and Type I & Type II catch basins serve as source control of pollution on the project site. In order to control pollutants, proper maintenance and cleaning of debris, sediments, and oil from stormwater collection and conveyance systems is required per the operation and maintenance recommendations found in Volume 5 Section 4.6 of the Stormwater Manual in addition to the BMPs in Volume IV Section 2.2. See the attached sheets for operation and maintenance requirements pertaining to the project. Contact Information for Stormwater Facility Manufacturers and Installers: Contractor (Installer of On -Site Stormwater Facilities) TBD Civil Engineer (Designer of On -Site Stormwater Facilities) Ben Iddins, P.E. Davido Consulting Group, Inc 9706 4th Ave NE, Suite 300 Seattle, WA 98115 Phone — 206.523.0024 ben(a),dcgen rg com Attachments • SWMMWW Operation and Maintenance Manual for Catch Basins • SWMMWW Maintenance Standards and Procedures for Detention Tanks and Control Structure/Flow Restrictor • SWMMWW Maintenance Standards and Procedures for Bioretention Facilities No. 5 — Catch Basins Maintenance Defect Conditions When Maintenance is Needed Results Expected When Component Maintenance is performed General Trash & Trash or debris which is located immediately No Trash or debris located Debris in front of the catch basin opening or is immediately in front of blocking inletting capacity of the basin by catch basin or on grate more than 10%. opening. Trash or debris (in the basin) that exceeds 60 No trash or debris in the percent of the sump depth as measured from catch basin. the bottom of basin to invert of the lowest pipe into or out of the basin, but in no case less than a minimum of six inches clearance from the debris surface to the invert of the lowest pipe. Trash or debris in any inlet or outlet pipe Inlet and outlet pipes free blocking more than 1 /3 of its height. of trash or debris. Dead animals or vegetation that could No dead animals or generate odors that could cause complaints vegetation present within or dangerous gases (e.g., methane). the catch basin. Sediment Sediment (in the basin) that exceeds 60 No sediment in the catch percent of the sump depth as measured from basin the bottom of basin to invert of the lowest pipe into or out of the basin, but in no case less than a minimum of 6 inches clearance from the sediment surface to the invert of the lowest pipe. Structure Top slab has holes larger than 2 square Top slab is free of holes Damage to inches or cracks wider than 1/4 inch and cracks. Frame and/or Top Slab (Intent is to make sure no material is running into basin). Frame not sitting flush on top slab, i.e., Frame is sitting flush on separation of more than 3/4 inch of the frame the riser rings or top slab from the top slab. Frame not securely and firmly attached. attached Fractures or Maintenance person judges that structure is Basin replaced or repaired Cracks in unsound. to design standards. Basin Walls/ Bottom Grout fillet has separated or cracked wider Pipe is regrouted and than 1/2 inch and longer than 1 foot at the secure at basin wall. joint of any inlet/outlet pipe or any evidence of soil particles entering catch basin through cracks. Settlement/ If failure of basin has created a safety, Basin replaced or repaired Misalignment function, or design problem. to design standards. Vegetation Vegetation growing across and blocking more No vegetation blocking than 10% of the basin opening. opening to basin. Vegetation growing in inlet/outlet pipe joints No vegetation or root that is more than six inches tall and less than growth present. six inches apart. Contamination See "Detention Ponds" (No. 1). No pollution present. and Pollution Volume V — Runoff Treatment BMPs — December 2014 4-38 No. 3 — Closed Detention Systems (Tanks/Vaults) Maintenance Defect Conditions When Maintenance is Needed Results Expected Component When Maintenance is Performed Storage Area Plugged Air Vents One-half of the cross section of a vent is Vents open and blocked at any point or the vent is damaged. functioning. Debris and Sediment Accumulated sediment depth exceeds 10% All sediment and of the diameter of the storage area for 1/2 debris removed from length of storage vault or any point depth storage area. exceeds 15% of diameter. (Example: 72-inch storage tank would require cleaning when sediment reaches depth of 7 inches for more than 1/2 length of tank.) Joints Between Any openings or voids allowing material to All joint between Tank/Pipe Section be transported into facility. tank/pipe sections (Will require engineering analysis to are sealed. determine structural stability). Tank Pipe Bent Out Any part of tank/pipe is bent out of shape Tank/pipe repaired or of Shape more than 10% of its design shape. (Review replaced to design. required by engineer to determine structural stability). Vault Structure Cracks wider than 1/2-inch and any Vault replaced or Includes Cracks in evidence of soil particles entering the repaired to design Wall, Bottom, structure through the cracks, or specifications and is Damage to Frame maintenance/inspection personnel structurally sound. and/or Top Slab determines that the vault is not structurally sound. Cracks wider than 1/2-inch at the joint of any No cracks more than inlet/outlet pipe or any evidence of soil 1/4-inch wide at the particles entering the vault through the walls. joint of the inlet/outlet pipe. Manhole Cover Not in Place Cover is missing or only partially in place. Manhole is closed. Any open manhole requires maintenance. Locking Mechanism Mechanism cannot be opened by one Mechanism opens Not Working maintenance person with proper tools. Bolts with proper tools. into frame have less than 1/2 inch of thread (may not apply to self-locking lids). Cover Difficult to One maintenance person cannot remove lid Cover can be Remove after applying normal lifting pressure. Intent removed and is to keep cover from sealing off access to reinstalled by one maintenance. maintenance person. Ladder Rungs Unsafe Ladder is unsafe due to missing rungs, Ladder meets design misalignment, not securely attached to standards. Allows structure wall, rust, or cracks. maintenance person safe access. Catch Basins See "Catch Basins" See "Catch Basins" (No. 5). See "Catch Basins" (No. 5) (No. 5). No. 4 — Control Structure/Flow Restrictor Maintenance Defect Condition When Maintenance is Needed Results Expected Component When Maintenance is Performed General Trash and Debris Material exceeds 25% of sump depth or 1 Control structure (Includes Sediment) foot below orifice plate. orifice is not blocked. All trash and debris removed. Structural Damage Structure is not securely attached to Structure securely manhole wall. attached to wall and outlet pipe. Structure is not in upright position (allow up Structure in correct to 10% from plumb). position. Connections to outlet pipe are not watertight Connections to outlet and show signs of rust. pipe are water tight; structure repaired or replaced and works as designed. Any holes --other than designed holes --in the Structure has no structure. holes other than designed holes. Cleanout Gate Damaged or Missing Cleanout gate is not watertight or is missing. Gate is watertight and works as designed. Gate cannot be moved up and down by one Gate moves up and maintenance person. down easily and is watertight. Chain/rod leading to gate is missing or Chain is in place and damaged. works as designed. Gate is rusted over 50% of its surface area. Gate is repaired or replaced to meet design standards. Orifice Plate Damaged or Missing Control device is not working properly due to Plate is in place and missing, out of place, or bent orifice plate. works as designed. Obstructions Any trash, debris, sediment, or vegetation Plate is free of all blocking the plate. obstructions and works as designed. Overflow Pipe Obstructions Any trash or debris blocking (or having the Pipe is free of all potential of blocking) the overflow pipe. obstructions and works as designed. Manhole See "Closed See "Closed Detention Systems" (No. 3). See "Closed Detention Systems" Detention Systems" (No. 3). (No. 3). Catch Basin See "Catch Basins" See "Catch Basins" (No. 5). See "Catch Basins" (No. 5). (No. 5). No. 21 - Maintenance Standards and Procedures for Bioretention Facilities. Note that the inspection and routine maintenance frequencies listed below are recommended by Ecology. They do not supersede or replace the municipal stormwater permit requirements for inspection frequency required of municipal stormwater permittees for "stormwater treatment and flow control BMPs/facilities." Maintenance Recommended Frequency • Condition when Maintenance is Needed Action Needed Inspection Routine Component (Standards) (Procedures) Maintenance Facility Footprint Earthen side slopes B, S Erosion (gullies/ rills) greater than 2 inches deep around Eliminate cause of erosion and stabilize damaged area (regrade, rock, vegetation, erosion control matting) and berms inlets, outlet, and alongside slopes For deep channels or cuts (over 3 inches in pending depth), temporary erosion control measures should be put in place until permanent repairs can be made. • Properly designed, constructed and established facilities with appropriate flow velocities should not have erosion problems except perhaps in extreme events. If erosion problems persist, the following should be reassessed: (1) flow volumes from contributing areas and bioretention facility sizing; (2) flow velocities and gradients within the facility; and (3) flow dissipation and erosion protection strategies at the facility inlet. A Erosion of sides causes slope to become a hazard Take actions to eliminate the hazard and stabilize slopes A, S Settlement greater than 3 inches (relative to undisturbed Restore to design height sections of berm) A, S Downstream face of berm wet, seeps or leaks evident Plug any holes and compact berm (may require consultation with engineer, particularly for larger berms) A Any evidence of rodent holes or water piping in berm Eradicate rodents (see "Pest control') • Fill holes and compact (may require consultation with engineer, particularly for larger berms) Concrete sidewalls A Cracks or failure of concrete sidewalls Repair/ seal cracks . Replace if repair is insufficient Rockery sidewalls A Rockery side walls are insecure Stabilize rockery sidewalls (may require consultation with engineer, particularly for walls 4 feet or greater in height) Facility area All maintenance Trash and debris present Clean out trash and debris visits (at least biannually) Facility bottom area A, S Accumulated sediment to extent that infiltration rate is • Remove excess sediment reduced (see "Ponded water") or surface storage capacity • Replace any vegetation damaged or destroyed by sediment accumulation and removal significantly impacted • Mulch newly planted vegetation • Identify and control the sediment source (if feasible) • If accumulated sediment is recurrent, consider adding presettlement or installing berms to create a forebay at the inlet During/after fall leaf Accumulated leaves in facility Remove leaves if there is a risk to clogging outlet structure or water flow is impeded drop Low permeability A, S Sediment, vegetation, or debris accumulated at or blocking Clear the blockage check dams and (or having the potential to block) check dam, flow control weirs weir or orifice A, S Erosion and/or undercutting present Repair and take preventative measures to prevent future erosion and/or undercutting A Grade board or top of weir damaged or not level Restore to level position a Frequency: A = Annually; B = Biannually (twice per year); M = Monthly; W = At least one visit should occur during the wet season (for debris/clog related maintenance, this inspection/maintenance visit should occur in the early fall, after deciduous trees have lost their leaves); S = Perform inspections after major storm events (24-hour storm event with a 10-year or greater recurrence interval). IPM - Integrated Pest Management ISA - International Society of Arboriculture Volume V— Runoff Treatment BMPs —December 2014 4-54 No. 21 (continued) - Maintenance Standards and Procedures for Bioretention Facilities. Maintenance Recommended Frequency • Condition when Maintenance is Needed Action Needed Inspection Routine Component (Standards) (Procedures) Maintenance Facility Footprint (cont'd) Ponded water B, S Excessive ponding water: Water overnows during storms Determine cause and resolve in the following order: smaller than the design event or ponded water remains in 1) Confirm leaf or debris buildup in the bottom of the facility is not impeding infiltration. If necessary, remove leaf litter/debris. the basin 48 hours or longer after the end of a storm. 2) Ensure that underdrain (if present) is not clogged. If necessary, clear underdrain. 3) Check for other water inputs (e.g., groundwater, illicit connections). 4) Verify that the facility is sized appropriately for the contributing area. Confirm that the contributing area has not increas ad. If steps #1-4 do not solve the problem, the bioretention soil is likely clogged by sediment accumulation at the surface or has become overly compacted. Dig a small hole to observe soil profile and identify compaction depth or clogging front to help determine the soil depth to be removed or otherwise rehabilitated (e.g., tilled). Consultation with an engineer is recommended. Bioretention soil As needed Bioretention soil media protection is needed when • Minimize all loading in the facility footprint (foot traffic and other loads) to the degree feasible in order to prevent compaction media performing maintenance requiring entrance into the facility of bioretention soils. footprint • Never drive equipment or apply heavy loads in facility footprint. • Because the risk of compaction is higher during saturated soil conditions, any type of loading in the cell (including foot traffic) should be minimized during wet conditions. • Consider measures to distribute loading if heavy foot traffic is required or equipment must be placed in facility. As an example, boards may be placed across soil to distribute loads and minimize compaction. • If compaction occurs, soil must be loosened or otherwise rehabilitated to original design state. Inlets/Outlets/Pipes Splash block inlet A Water is not being directed properly to the facility and Reconfigure/ repair blocks to direct water to facility and away from structure away from the inlet structure Curb cut inlet/outlet M during the Weekly during fall Accumulated leaves at curb cuts Clear leaves (particularly important for key inlets and low points along long, linear facilities) wet season leaf drop and before severe storm is forecasted Pipe inlet/outlet A Pipe is damaged Repair/ replace W Pipe is clogged Remove roots or debris A, S Sediment, debris, trash, or mulch reducing capacity of Clear the blockage inlet/outlet Identify the source of the blockage and take actions to prevent future blockages Weekly during fall Accumulated leaves at inlets/outlets Clear leaves (particularly important for key inlets and low points along long, linear facilities) leaf drop A Maintain access for inspections Clear vegetation (transplant vegetation when possible) within 1 foot of inlets and outlets, maintain access pathways • Consultation with a landscape architect is recommended for removal, transplant, or substitution of plants Erosion control at A Concentrated flows are causing erosion Maintain a cover of rock or cobbles or other erosion protection measure (e.g., matting) to protect the ground where inlet concentrated water enters the facility (e.g., a pipe, curb cut or swale) Volume V— Runoff Treatment BMPs —December 2014 4-55 No. 21 (continued) - Maintenance Standards and Procedures for Bioretention Facilities. Maintenance Recommended Frequency. Condition when Maintenance is Needed Action Needed Inspection Routine Component (Standards) (Procedures) Maintenance Inlets/Outlets/Pipes (cont'd) Trash rack S Trash or other debris present on trash rack Remove/dispose A Bar screen damaged or missing Repair/replace Overflow A, S Capacity reduced by sediment or debris Remove sediment or debris/dispose Underdrain pipe Clean pipe as Clean orifice at least • Plant roots, sediment or debris reducing capacity of • Jet clean or rotary cut debris/roots from underdrain(s) needed biannually (may underdrain If underdrains are equipped with a flow restrictor (e.g., orifice) to attenuate flows, the orifice must be cleaned regularly. need more frequent • Prolonged surface ponding (see "Ponded water") cleaning during wet season) Vegetation Facility bottom area Fall and Vegetation survival rate falls below 75% within first two Determine cause of poor vegetation growth and correct condition and upland slope Spring years of establishment (unless project O&M manual or Replant as necessary to obtain 75% survival rate or greater. Refer to original planting plan, or approved jurisdictional vegetation record drawing stipulates more or less than 75% survival species list for appropriate plant replacements (See Appendix 3 - Bioretention Plant List, in the LID Technical Guidance rate). Manual for Puget Sound). • Confirm that plant selection is appropriate for site growing conditions • Consultation with a landscape architect is recommended for removal, transplant, or substitution of plants Vegetation (general) As needed Presence of diseased plants and plant material Remove any diseased plants or plant parts and dispose of in an approved location (e.g., commercial landfill) to avoid risk of spreading the disease to other plants • Disinfect gardening tools after pruning to prevent the spread of disease • See Pacific Northwest Plant Disease Management Handbook for information on disease recognition and for additional resources • Replant as necessary according to recommendations provided for "facility bottom area and upland slope vegetation". Trees and shrubs All pruning seasons Pruning as needed Prune trees and shrubs in a manner appropriate for each species. Pruning should be performed by landscape professionals (timing varies by familiar with proper pruning techniques species) All pruning of mature trees should be performed by or under the direct guidance of an ISA certified arborist A Large trees and shrubs interfere with operation of the Prune trees and shrubs using most current ANSI A300 standards and ISA BMPs. facility or access for maintenance Remove trees and shrubs, if necessary. Fall and Standing dead vegetation is present Remove standing dead vegetation Spring • Replace dead vegetation within 30 days of reported dead and dying plants (as practical depending on weather/planting season) • If vegetation replacement is not feasible within 30 days, and absence of vegetation may result in erosion problems, temporary erosion control measures should be put in place immediately. • Determine cause of dead vegetation and address issue, if possible • If specific plants have a high mortality rate, assess the cause and replace with appropriate species. Consultation with a landscape architect is recommended. Fall and Planting beneath mature trees • When working around and below mature trees, follow the most current ANSI A300 standards and ISA BMPs to the extent Spring practicable (e.g., take care to minimize any damage to tree roots and avoid compaction of soil). • Planting of small shrubs orgroundcovers beneath mature trees may be desirable in some cases; such plantings should use mainly plants that come as bulbs, bare root or in 4-inch pots; plants should be in no larger than 1-gallon containers. Volume V— Runoff Treatment BMPs —December 2014 4-56 No. 21 (continued) - Maintenance Standards and Procedures for Bioretention Facilities. Maintenance Recommended Frequency. Condition when Maintenance is Needed Action Needed Inspection Routine Component (Standards) (Procedures) Maintenance Vegetation (cont'd) Trees and shrubs Fall and Planting beneath mature trees When working around and below mature trees, follow the most current ANSI A300 standards and ISA BMPs to the extent (cont'd) Spring practicable (e.g., take care to minimize any damage to tree roots and avoid compaction of soil). . Planting of small shrubs orgroundcovers beneath mature trees may be desirable in some cases; such plantings should use mainly plants that come as bulbs, bare root or in 4-inch pots; plants should be in no larger than 1-gallon containers. Fall and Presence of or need for stakes and guys (tree growth, . Verify location of facility liners and underdrain (if any) prior to stake installation in order to prevent liner puncture or pipe Spring maturation, and support needs) damage • Monitor tree support systems: Repair and adjust as needed to provide support and prevent damage to tree. • Remove tree supports (stakes, guys, etc.) after one growing season or maximum of 1 year. . Backfill stake holes after removal. Trees and shrubs A Vegetation causes some visibility (line of sight) or driver Maintain appropriate height for sight clearance adjacent to vehicle safety issues When continued, regular pruning (more than one time/ growing season) is required to maintain visual sight lines for safety or travel areas (or clearance along a walk or drive, consider relocating the plant to a more appropriate location. areas where visibility Remove or transplant if continual safety hazard needs to be Consultation with a landscape architect is recommended for removal, transplant, or substitution of plants maintained) Flowering plants A Dead or spent flowers present Remove spent flowers (deadhead) Perennials Fall Spent plants Cut back dying or dead and fallen foliage and stems Emergent vegetation Spring Vegetation compromises conveyance • Hand rake sedges and rushes with a small rake or fingers to remove dead foliage before new growth emerges in spring or earlier only if the foliage is blocking water flow (sedges and rushes do not respond well to pruning) Ornamental grasses Winter and Spring Dead material from previous year's growing cycle or dead Leave dry foliage for winter interest (perennial) collapsed foliage • Hand rake with a small rake or fingers to remove dead foliage back to within several inches from the soil before new growth emerges in spring or earlier if the foliage collapses and is blocking water flow Ornamental grasses Fall and Spring Dead growth present in spring Hand rake with a small rake or fingers to remove dead growth before new growth emerges in spring (evergreen) • Clean, rake, and comb grasses when they become too tall • Cut back to ground or thin every 2-3 years as needed Noxious weeds M Listed noxious vegetation is present (refer to current By law, class A & B noxious weeds must be removed, bagged and disposed as garbage immediately (March — October, county noxious weed list) Reasonable attempts must be made to remove and dispose of class C noxious weeds preceding seed . It is strongly encouraged that herbicides and pesticides not be used in order to protect water quality; use of herbicides and dispersal) pesticides may be prohibited in some jurisdictions • Apply mulch after weed removal (see "Mulch") . Frequency: A = Annually; B = Biannually (twice per year); M = Monthly; W = At least one visit should occur during the wet season (for debris/clog related maintenance, this inspection/maintenance visit should occur in the early fall, after deciduous trees have lost their leaves); S = Perform inspections after major storm events (24-hour storm event with a 10-year or greater recurrence interval). IPM - Integrated Pest Management ISA - International Society of Arboriculture Volume V— Runoff Treatment BMPs —December 2014 4-57 No. 21 (continued) - Maintenance Standards and Procedures for Bioretention Facilities. Maintenance Recommended Frequency. Condition when Maintenance is Needed Action Needed Inspection Routine Component (Standards) (Procedures) Maintenance Vegetation (cont'd) Weeds M Weeds are present Remove weeds with their roots manually with pincer -type weeding tools, flame weeders, or hot water weeders as (March — October, appropriate preceding seed • Follow IPM protocols for weed management (see "Additional Maintenance Resources" section for more information on IPM dispersal) protocols) Excessive vegetation Once in early to mid- Low-lying vegetation growing beyond facility edge onto Edge or trim groundcovers and shrubs at facility edge May and once in sidewalks, paths, or street edge poses pedestrian safety Avoid mechanical blade -type edger and do not use edger or trimmer within 2 feet of tree trunks early- to mid- hazard or may clog adjacent permeable pavement • While some clippings can be left in the facility to replenish organic material in the soil, excessive leaf litter can cause surface September surfaces due to associated leaf litter, mulch, and soil soil clogging As needed Excessive vegetation density inhibits stormwater flow Determine whether pruning or other routine maintenance is adequate to maintain proper plant density and aesthetics beyond design ponding or becomes a hazard for • Determine if planting type should be replaced to avoid ongoing maintenance issues (an aggressive grower under perfect pedestrian and vehicular circulation and safety growing conditions should be transplanted to a location where it will not impact flow) . Remove plants that are weak, broken or not true to form; replace in -kind • Thin grass or plants impacting facility function without leaving visual holes or bare soil areas • Consultation with a landscape architect is recommended for removal, transplant, or substitution of plants As needed Vegetation blocking curb cuts, causing excessive sediment • Remove vegetation and sediment buildup buildup and flow bypass Mulch Mulch Following weeding Bare spots (without mulch cover) are present or mulch Supplement mulch with hand tools to a depth of 2 to 3 inches depth less than 2 inches Replenish mulch per O&M manual. Often coarse compost is used in the bottom of the facility and arborist wood chips are used on side slopes and rim (above typical water levels) • Keep all mulch away from woody stems Watering Irrigation system (if Based on Irrigation system present • Follow manufacturer's instructions for O&M any) manufacturer's instructions A Sprinklers or drip irrigation not directed/located to properly • Redirect sprinklers or move drip irrigation to desired areas water plants Summer watering Once every 1-2 Trees, shrubs and groundcovers in first year of • 10 to 15 gallons per tree (first year) weeks or as needed establishment period • 3 to 5 gallons per shrub during prolonged dry • 2 gallons water per square foot for groundcover areas periods • Water deeply, but infrequently, so that the top 6 to 12 inches of the root zone is moist • Use soaker hoses or spot water with a shower type wand when irrigation system is not present o Pulse water to enhance soil absorption, when feasible o Pre -moisten soil to break surface tension of dry or hydrophobic soils/mulch, followed by several more passes. With this method , each pass increases soil absorption and allows more water to infiltrate prior to runoff • Add a tree bag or slow -release watering device (e.g., bucket with a perforated bottom) for watering newly installed trees when irrigation system is not present . Frequency: A = Annually; B = Biannually (twice per year); M = Monthly; W = At least one visit should occur during the wet season (for debris/clog related maintenance, this inspection/maintenance visit should occur in the early fall, after deciduous trees have lost their leaves); S = Perform inspections after major storm events (24-hour storm event with a 10-year or greater recurrence interval). IPM - Integrated Pest Management ISA - International Society of Arboriculture Volume V— Runoff Treatment BMPs —December 2014 4-58 No. 21 (continued) - Maintenance Standards and Procedures for Bioretention Facilities. Maintenance Recommended Frequency. Condition when Maintenance is Needed Action Needed Inspection Routine Component (Standards) (Procedures) Maintenance Watering (cont'd) Summer watering Once every 2-4 Trees, shrubs and groundcovers in second or third year of . 10 to 15 gallons per tree (second and third weeks or as needed establishment period • 3 to 5 gallons per shrub years) during prolonged dry • 2 gallons water per square foot for groundcover areas periods Water deeply, but infrequently, so that the top 6 to 12 inches of the root zone is moist • Use soaker hoses or spot water with a shower type wand when irrigation system is not present o Pulse water to enhance soil absorption, when feasible o Pre -moisten soil to break surface tension of dry or hydrophobic soils/mulch, followed by several more passes. With this method , each pass increases soil absorption and allows more water to infiltrate prior to runoff Summer watering As needed Established vegetation (after 3 years) • Plants are typically selected to be drought tolerant and not require regular watering after establishment; however, trees may (after establishment) take up to 5 years of watering to become fully established • Identify trigger mechanisms for drought -stress (e.g., leaf wilt, leaf senescence, etc.) of different species and water immediately after initial signs of stress appear • Water during drought conditions or more often if necessary to maintain plant cover Pest Control 06 Mosquitoes B, S Standing water remains for more than 3 days after the end Identify the cause of the standing water and take appropriate actions to address the problem (see "Ponded water") of a storm • To facilitate maintenance, manually remove standing water and direct to the storm drainage system (if runoff is from non pollution -generating surfaces) or sanitary sewer system (if runoff is from pollution -generating surfaces) after getting approval from sanitary sewer authority. • Use of pesticides or Bacillus thuringiensis israelensis (Bti)may be considered only as a temporary measure while addressing the standing water cause. If overnow to a surface water will occur within 2 weeks after pesticide use, apply for coverage under the Aquatic Mosquito Control NPDES General Permit. Nuisance animals As needed Nuisance animals causing erosion, damaging plants, or • Reduce site conditions that attract nuisance species where possible (e.g., plant shrubs and tall grasses to reduce open depositing large volumes of feces areas for geese, etc.) • Place predator decoys • Follow IPM protocols for specific nuisance animal issues (see "Additional Maintenance Resources" section for more information on IPM protocols) . Remove pet waste regularly • For public and right-of-way sites consider adding garbage cans with dog bags for picking up pet waste. Insect pests Every site Signs of pests, such as wilting leaves, chewed leaves and • Reduce hiding places for pests by removing diseased and dead plants visit bark, spotting or other indicators • For infestations, follow IPM protocols (see "Additional Maintenance Resources" section for more information on IPM associated protocols) with vegetation management . Frequency: A = Annually; B = Biannually (twice per year); M = Monthly; W = At least one visit should occur during the wet season (for debris/clog related maintenance, this inspection/maintenance visit should occur in the early fall, after deciduous trees have lost their leaves); S = Perform inspections after major storm events (24-hour storm event with a 10-year or greater recurrence interval). IPM - Integrated Pest Management ISA - International Society of Arboriculture Volume V— Runoff Treatment BMPs —December 2014 4-59 Stormwater Site Plans — Rev 2 302 6th Ave S Edmonds APPENDIX D Declaration of Covenant June 2021 20210608_302 6th Ave S Edmonds_ Drainage ReportRev 2 After recording return to: City Clerk City of Edmonds 121 Fifth Avenue North Edmonds, WA 98020 Document Title(s) Declaration of Covenant - Private Stormwater Facility Reference Number(s) of Related Documents Grantor(s) (Last, First and Middle Initial) Pickering, Chris Grantee(s) (Last, First and Middle Initial) City of Edmonds Legal Description (abbreviated form; i.e., lot, plat or section, township, range, quarter/quarter) LOTS 19 AND 20, BLOCK 122, CITY OF EDMONDS ADDITION ACCORDING TO THE PLAT THEREOF RECORDED IN VOLUME 2 OF PLATS, PAGE 39, RECORDS OF SNOHOMISH COUNTY, WASHINGTON. Assessor's Property Tax Parcel/Account Number at the Time of Recording: PARCEL NUMBER 00434212201900 The Auditor/Recorder will rely on the information provided on this form. The staff will not read the document to verify the accuracy or completeness of the indexing information provided herein. DECLARATION OF COVENANT Private Stormwater Facility WHEREAS, the undersigned Declarant(s) have installed one or more stormwater facilities under Edmonds Community Development Code Chapter 18.30 known as a "low impact development best management practices (LID BMP)" as selected below: ❑ Permeable Pavement ❑ Rain Garden / Bioretention Cell ❑ Drywell ❑ Infiltration Trench ❑ Gravelless Chamber A Other underdrain Bioretention Planters Detention Pipe WHEREAS, the City of Edmonds has allowed installation of the LID BMP, subject to the execution and recording of this Declaration of Covenant; NOW, THEREFORE, THE UNDERSIGNED DECLARANT(S), being the owners of the real property ("the Property") located at the following address: 302 6th Ave S in the City of Edmonds, Washington, and legally described on Exhibit A attached hereto and incorporated herein by this reference as if set forth in full, hereby covenants and agrees, on behalf of himself/herself/themselves/itself and his/her/their/its successors and assigns, as follows: I. Declarant(s) warrant that he/she/they are the owners of the property described on Exhibit A and have the authority to impose this covenant on the property and bind all future owners, successors, and assigns of the Declarant(s). The Declarant(s), future owners, successors, and assigns of the Declarant(s) shall be referred to collectively as "Owners." 2. The Owners of the Property agree that the Property contains one or more stormwater management facilities referred to as an "LID BMP," which was installed to mitigate the stormwater quantity and quality impacts of some or all of the impervious or non-native pervious surfaces on the property. "Low impact development" means development conducted in a way that seeks to minimize or completely prevent alterations to the natural hydrology of the site. Low impact development includes site planning and design to reduce alterations of natural soil and vegetation cover, minimize impervious surfaces, and specific practices that help to replicate natural hydrology such as permeable pavements, green roofs, soil amendments, bioretention systems, and dispersion of runoff. 3. The Owners shall maintain the size, placement, and design of the LID BMP as depicted on the approved site plan, Exhibit B, and design details shall be maintained and may not be changed without written approval either from the Engineering Division of the City of Edmonds or through a future development permit from the City of Edmonds. Chemical fertilizers and pesticides shall not be used where LID BMP is located. All costs of maintenance and repair shall be the sole responsibility of the Owners. 4. The Owners shall inspect LID BMPs annually for physical defects. After major storm events, the system shall also be checked to ensure that the overflow system is working properly. The Owners also shall maintain all LID BMPs so they function as designed on a year-round basis. 5. The City of Edmonds is hereby granted by the Owners the right, but not the obligation, to enter upon the Property described on Exhibit A at all reasonable times for the purpose of inspecting the private stormwater LID BMP facility. If, as the result of any such inspection, the City of Edmonds determines that the LID BMP is in disrepair, requires maintenance or repair, or is otherwise not functioning as provided in the BMP site plan, the City Engineer or his designee shall have the right, but not the obligation, to order the Owners to maintain or repair the same. 6. If the City of Edmonds determines that the LID BMP requires maintenance or repair pursuant to Section 5, the City of Edmonds shall provide notice to the Owners of the deadline within which such maintenance or repair must be completed. Said notice may further advise that, should the violator fail to perform required maintenance or make repairs within the established deadline, the work may be done by the city or a contractor designated by the City Engineer and the expense thereof shall be charged to the Owners. The City's officers, agents, employees, and contractors shall have the right, which is hereby granted by the Owners, to enter upon the Property described on Exhibit A in order to perform such work. The Owners shall bear the cost of all work performed. 7. The Owners shall indemnify, defend and hold harmless the City of Edmonds, its officers, officials, employees and agents from any and all claims, demands, suits, penalties, losses, damages, judgments, attorneys' fees and/or costs of any kind whatsoever, arising out of or in any way resulting from the approval of the LID BMP(s), the installation and presence of the LID BMP(s), and the acts or omissions of the Owners, their officers, employees, contractors, and agents relating to the construction, operation and maintenance of the LID BMP(s) on the Property, except for the City's intentional and willful tortious acts, and waive and release the City of Edmonds from any and all claims for damages and injunctive relief which the Owners may themselves have now or in the future, by reason of the construction, maintenance and operation of said LID BMP(s). 8. This covenant shall run with the land and be binding upon the Owners. Dated: DECLARANT(S): (Signature) (Print Name) (Signature) (Print Name) State of Washington RIM County of Snohomish APPROVED: CITY OF EDMONDS (Signature) (Print Name) (Title) On this day personally appeared before me {Declarant(s)} to me known to be the individual, or individuals described in and who executed the within and foregoing instrument, and acknowledged that he/she/they signed the same as his/her/their free and voluntary act and deed, for the uses and purposes therein mentioned. SUBSCRIBED AND SWORN before me this day of , 201_. (Signature) (Name legibly printed or stamped) Notary Public in and for the State of Washington. Residing at: My commission expires Exhibit A Legal description LOTS 17 AND 18 BLOCK 98 OF THE PLAT OF CITY OF EDMONDS, ACCORDING TO THE PLAT THEREOF RECORDED IN VOLUME 2 OF PLATS, PAGES 39 AND 39A, RECORDS OF SNOHOMISH COUNTY AUDITOR. PARCEL No. 00434209801700 ADDRESS: 650 BELL STREET, EDMONDS, WASHINGTON 98020 Exhibit B Site Plan TYPE 2 CB W/ FLOW ` RESTRICTOR TEE ',' = �, "•.• 28 LF 36" DIAMETER ;. DETENTION TANK ' 5'x2' BIORETENTION • PLANTER BOX W/ s — UNDERDRAIN • 13'x2' BIORETENTION s ' 300 6TH AVE S PLANTER BOX W/ UNDERDRAIN • 14.5'x2.2' BIORETENTION PLANTER BOX W/ �. 302 6TH AVE S I UNDERDRAIN It i ate! 'a 304 6TH AVE S 16.7'x4.2' BIORETENTION ��= =' PLANTER BOX W/ UNDERDRAIN Pi w •1 Stormwater Site Plans — Rev 2 302 6th Ave S Edmonds APPENDIX E Conveyance Calculations June 2021 20210608_302 6th Ave S Edmonds_ Drainage ReportRev 2 RATIONAL METHOD for Conveyance Facility Sizing Project: 302 6th Ave S Edmonds Description: Rational method for SD pipe sizing Design Storm: 100 yr Q=CIA Where: Q = peak flow (cfs) I = peak rainfall intensity (inches/hour) C = estimated composite runoff coefficient A = drainage subbasin area (acres) Composite Runoff Coefficient Cc = (C1*A1+C2*A2... )/At Where: Cc = composite runoff coefficient A# = area of land cover (acres) C# = runoff coefficient for Area # At = total area (acres) Area C # Description Area (sf) (acres) C A*C 1 Onsite/New Impervious Surface 5,800 0.13 0.90 0.12 2 Onsite/New Pervious Surface 0 0.00 0.25 0.00 Totals: 0.13 0.12 Cc = 0.90 (total C#*A#)/(total area) Time of Concentration Travel Upper Lower Slope Time Seg. # Description of Flow Path Segment Length (ft) kr Elev Elev (ft/ft) (minutes) 1 Paved Area (sheet flow) and shallow gutter flow 110 20 105.01 99.23 0.053 0.40 Totals: 110 0.4 Unity Peak Intensity Factor it = ar*TcA-br where: Tc = time of concentration (minutes) ar and br = coefficients from Table 3.2.1.E Tc = 6.30 minutes (from table above or 6.3 minimum or 100 max) ar = 2.61 (from Table 3.2.1.13) br = 0.63 (from Table 3.2.1.13) it = 0.82 Peak Rainfall Intensity Ir = Pr*ir where: Ir = peak rainfall intensity (inches/hour) Pr = total 24-hour precipitation for design return period (inches/24 hours) it = unit peak rainfall intensity factor Pr = 4 precipitation (inches) it = 0.82 unit peak intensity factor (from above) Ir = 3.27 inches/hour Peak Runoff Rate Q = C*Ir*A C = 0.90 Cc (unitless) from above Ir = 3.27 Ir (inches/hour) from above A = 0.13 total area (acres) from above Q = 0.392 cfs Pipe Capacity Calculations (Manning's Equation) Full Flow (d/D = 0.90) Description ID (inches) Area (sf) 6" for Entire site 6 0.196349541 Wetted Per. Hyd. Manning's Slope Velocity (ft) Radius (ft) n (ft/ft) (ft/s) 1.570796327 0.125 0.013 0.01 2.87 6/10/2021 Pipe Capacity Req'd Flow (cfs) (cfs) 0.563 0.392 Capacity OK Storm Drain Pipe Sizing_Rational Method_BI Calculations DCG, Inc. Page 1 of 1 Stormwater Site Plans — Rev 2 302 61h Ave S Edmonds June2021 APPENDIX F King County Site Improvement Bond Quantity Worksheet 20210608_302 6th Ave S Edmonds —Drainage Report Rev 2 Site Improvement Bond Quantity Worksheet S15 Webdate: 04/03/2015 L■ King County Department of Permitting & Environmental Review 35030 SE Douglas Street, Suite 210 Snoqualmie, Washington 98065-9266 For alternate formats, call 206-296-6600. 206-296-6600 TTY Relay 711 Project Name: Location: 302 6th Ave S Edmonds 302 6th Ave S Edmonds Clearing greater than or equal to 5,000 board feet of timber? yes If yes, Forest Practice Permit Number: (RCW 76.09) Page 1 of 9 KC BQ Worksheet_Complete X no Date: Project No.: Activity No.: 6/10/2021 BLD2020-0388 Note: All prices include labor, equipment, materials, overhead and profit. Prices are from IRS Means data adjusted for the Seattle area or from local sources if not included in the IRS Means database. Unit prices updated: 3/2/2015 Version: 3/2/2015 Report Date: 6/10/2021 Site Improvement Bond Quantity Worksheet S15 Web date: 04/03/2015 Reference # Unit Price Unit Quantity # of Applications Cost EROSION/SEDIMENT CONTROL Number Backfill & compaction -embankment ESC-1 $ 6.00 CY Check dams, 4" minus rock ESC-2 SWDM 5.4.6.3 $ 80.00 Each Crushed surfacing 1 1/4" minus ESC-3 WSDOT 9-03.9(3) $ 95.00 CY Ditching ESC-4 $ 9.00 CY Excavation -bulk ESC-5 $ 2.00 CY Fence, silt ESC-6 SWDM 5.4.3.1 $ 1.50 LF 227 1 $ 340.50 Fence, Temporary (NGPE) ESC-7 $ 1.50 LF 209 1 $ 313.50 Hydroseeding ESC-8 SWDM 5.4.2.4 $ 0.80 SY Jute Mesh ESC-9 SWDM 5.4.2.2 $ 3.50 SY $ - Mulch, by hand, straw, 3" deep ESC-10 SWDM 5.4.2.1 $ 2.50 SY $ - Mulch, by machine, straw, 2" deep ESC-11 SWDM 5.4.2.1 $ 2.00 SY $ - Piping, temporary, CPP, 6" ESC-12 $ 12.00 LF $ - Piping, temporary, CPP, 8" ESC-13 $ 14.00 LF $ - Piping, temporary, CPP, 12" ESC-14 $ 18.00 LF $ - Plastic covering, 6mm thick, sandbagged ESC-15 SWDM 5.4.2.3 $ 4.00 SY $ - Rip Rap, machine placed; slopes ESC-16 WSDOT 9-13.1(2) $ 45.00 CY $ - Rock Construction Entrance, 50'x15'x1' ESC-17 SWDM 5.4.4.1 $ 1,800.00 Each 1 1 $ 1,800.00 Rock Construction Entrance, 100'x15'x1' ESC-18 SWDM 5.4.4.1 $ 3,200.00 Each Sediment pond riser assembly ESC-19 SWDM 5.4.5.2 $ 2,200.00 Each $ - Sediment trap, 5' high berm ESC-20 SWDM 5.4.5.1 $ 19.00 LF $ - Sed. trap, 5' high, riprapped spillway berm section ESC-21 SWDM 5.4.5.1 $ 70.00 LF $ - Seeding, by hand Sodding, 1" deep, level ground ESC-22 SWDM 5.4.2.4 $ 1.00 SY $ - ESC-23 SWDM 5.4.2.5 $ 8.00 SY $ - Sodding, 1" deep, sloped ground ESC-24 SWDM 5.4.2.5 $ 10.00 SY $ - TESC Supervisor ESC-25 $ 110.00 HR 40 1 $ 4,400.00 Water truck, dust control ESC-26 SWDM 5.4.7 $ 140.00 HR $ - WRITE -IN -ITEMS **** (see page 9) Inlet Protection $ 74.00 Each 8 1 592 ESC SUBTOTAL: 30% CONTINGENCY & MOBILIZATION: ESC TOTAL: COLUMN: Page 2 of 9 KC BQ Worksheet_Complete $ 7,446.00 $ 2,233.80 $ 9,679.80 A Unit prices updated: 3/2/2015 Version: 3/2/2015 Report Date: 6/10/2021 Site Improvement Bond Quantity Worksheet Web date: 04/03/2015 Existing Right -of -Way Future Public Right of Way & Drainage Facilities Private Improvements Unit Price Unit Quant. Cost Quant. Cost Quant. Cost GENERAL ITEMS No. Backfill & Compaction- embankment GI - 1 $ 6.00 CY Backfill & Compaction- trench GI - 2 $ 9.00 CY 124 1,116.00 65 585.00 Clear/Remove Brush, by hand GI - 3 $ 1.00 SY Clearing/Grubbing/Tree Removal GI - 4 $ 10,000.00 Acre 0.21 2,100.00 Excavation - bulk GI - 5 $ 2.00 CY Excavation - Trench GI - 6 $ 5.00 CY 124 620.00 65 325.00 Fencing, cedar, 6' high GI - 7 $ 20.00 LF Fencing, chain link, vinyl coated, 6' high GI - 8 $ 20.00 LF Fencing, chain link, gate, vinyl coated, 20' GI - 9 $ 1,400.00 Each Fencing, split rail, 3' high GI - 10 $ 15.00 LF Fill & compact - common barrow GI - 11 $ 25.00 CY Fill & compact - gravel base GI - 12 $ 27.00 CY Fill & compact - screened topsoil GI - 13 $ 39.00 CY Gabion, 12" deep, stone filled mesh GI - 14 $ 65.00 SY Gabion, 18" deep, stone filled mesh GI - 15 $ 90.00 SY Gabion, 36" deep, stone filled mesh GI - 16 $ 150.00 SY Grading, fine, by hand GI - 17 $ 2.50 SY Grading, fine, with grader GI - 18 $ 2.00 SY 400 800.00 Monuments, 3' long GI - 19 $ 250.00 Each Sensitive Areas Sign GI - 20 $ 7.00 Each Sodding, 1" deep, sloped ground GI - 21 $ 8.00 SY Surveying, line & grade GI - 22 $ 850.00 Day Surveying, lot location/lines GI - 23 $ 1,800.00 Acre Traffic control crew ( 2 flaggers) GI - 24 $ 120.00 HR 40 4,800.00 Trail, 4" chipped wood GI - 25 $ 8.00 SY Trail, 4" crushed cinder GI - 26 $ 9.00 SY Trail, 4" top course GI - 27 $ 12.00 SY Wall, retaining, concrete GI - 28 $ 55.00 SF 90 4,950.00 Wall, rockery GI - 29 $ 15.00 SF Page 3 of 9 SUBTOTAL 6,536.00 760.00 Unit prices updated: 03/02/2015 "KCC 27A authorizes only one bond reduction. Version: 03/02/2015 KC BQ Worksheet_Complete Report Date: 6/10/2021 Site Improvement Bond Quantity Worksheet Web date: 04/03/2015 Existing Right-of-way Future Public Right of Way & Drainage Facilities Private Improvements Unit Price Unit Quant, Cost Quant. Cost Quant. Cost ROAD IMPROVEMENT No. AC Grinding, 4' wide machine < 1000sy RI - 1 $ 30.00 SY AC Grinding, 4' wide machine 1000-2000 RI - 2 $ 16.00 SY AC Grinding, 4' wide machine > 2000sy RI - 3 $ 10.00 SY AC Removal/Disposal RI - 4 $ 35.00 SY 77 2,695.00 Barricade, type III ( Permanent) RI - 6 $ 56.00 LF Curb & Gutter, rolled RI - 7 $ 17.00 LF Curb & Gutter, vertical RI - 8 $ 12.50 LF 50 625.00 Curb and Gutter, demolition and disposal RI - 9 $ 18.00 LF 50 900.00 Curb, extruded asphalt RI - 10 $ 5.50 LF Curb, extruded concrete RI - 11 $ 7.00 LF Sawcut, asphalt, 3" depth RI - 12 $ 1.85 LF 202 373.70 Sawcut, concrete, per 1" depth RI - 13 $ 3.00 LF Sealant, asphalt RI - 14 $ 2.00 LF Shoulder, AC, ( see AC road unit price ) RI - 15 $ - SY Shoulder, gravel, 4" thick RI - 16 $ 15.00 SY Sidewalk, 4" thick RI - 17 $ 38.00 SY 135 5,130.00 Sidewalk, 4" thick, demolition and disposal RI - 18 $ 32.00 SY 135 4,320.00 Sidewalk, 5" thick RI - 19 $ 41.00 SY Sidewalk, 5" thick, demolition and disposal RI - 20 $ 40.00 SY Sign, handicap RI - 21 $ 85.00 Each Striping, per stall RI - 22 $ 7.00 Each Striping, thermoplastic, ( for crosswalk) RI - 23 $ 3.00 SF Striping, 4" reflectorized line RI - 24 $ 0.50 1 LF 449 224.50 Page 4 of 9 611113 r91CAI 14,043.70 224.50 Unit prices updated: 03/02/2015 "KCC 27A authorizes only one bond reduction. Version: 03/02/2015 KC BQ Worksheet_Complete Report Date: 6/10/2021 Site Improvement Bond Quantity Worksheet Web date: 04/03/2015 Existing Right-of-way Future Public Right of Way & Drainage Facilities Private Improvements Unit Price Unit Quant. Cost Quant. Cost Quant. Cost ROAD SURFACING No. 4" Rock = 2.5 base & 1.5" top course 9 1/2" Rock= 8" base & 1.5" top course Additional 2.5" Crushed Surfacing RS - 1 $ 3.60 SY HMA 1/2" Overlay, 1.5" RS - 2 $ 14.00 SY HMA 1/2" Overlay 2" RS - 3 $ 18.00 SY HMA Road, 2", 4" rock, First 2500 SY RS - 4 $ 28.00 SY HMA Road, 2", 4" rock, Qty. over 2500 SY RS - 5 $ 21.00 SY HMA Road, 3", 9 1/2" Rock, First 2500 S RS - 6 $ 42.00 SY HMA Road, 3", 9 1/2" Rock, Qty Over 250 RS - 7 $ 35.00 SY Not Used RS - 8 Not Used RS - 9 HMA Road, 6" Depth, First 2500 SY RS - 10 $ 33.10 SY 278 9,201.80 HMA Road, 6" Depth, Qty. Over 2500 SY RS - 11 $ 30.00 SY HMA 3/4" or 1", 4" Depth RS - 12 $ 20.00 SY Gravel Road, 4" rock, First 2500 SY RS - 13 $ 15.00 SY Gravel Road, 4" rock, Qty. over 2500 SY RS - 14 $ 10.00 SY PCC Road (Add Under Write -Ins w/Desig RS - 15 Thickened Edge IRS - 17 $ 8.60 LF Page 5 of 9 SUBTOTAL 9,201.80 Unit prices updated: 03/02/2015 "KCC 27A authorizes only one bond reduction. Version: 03/02/2015 KC BQ Worksheet_Complete Report Date: 6/10/2021 Site Improvement Bond Quantity Worksheet Web date: 04/03/2015 Existing Right-of-way Future Public Right of Way & Drainage Facilities Private Improvements Unit Price Unit Quant. Cost Quant. I Cost Quant. Cost DRAINAGE (CPP = Corrugated Plastic Pipe, N12 or Equivalent) For Culvert prices, Average of 4' cover was assumed. Assume perforated PVC is same price as solid pipe. Access Road, R/D D - 1 $ 21.00 SY Bollards - fixed D - 2 $ 240.74 Each Bollards - removable D - 3 $ 452.34 Each " (CBs include frame and lid) CB Type I D - 4 $ 1,500.00 Each 1 1,500.00 2 3,000.00 CB Type IL D - 5 $ 1,750.00 Each CB Type II, 48" diameter D - 6 $ 2,300.00 Each 1 2,300.00 for additional depth over 4' D - 7 $ 480.00 FT CB Type II, 54" diameter D - 8 $ 2,500.00 Each 1 2,500.00 2 5,000.00 for additional depth over 4' D - 9 $ 495.00 FT CB Type II, 60" diameter D - 10 $ 2,800.00 Each for additional depth over 4' D - 11 $ 600.00 FT CB Type II, 72" diameter D - 12 $ 3,600.00 Each for additional depth over 4' D - 13 $ 850.00 FT Through -curb Inlet Framework (Add) D - 14 $ 400.00 Each Cleanout, PVC, 4" D - 15 $ 150.00 Each Cleanout, PVC, 6" D - 16 $ 170.00 Each 9 1,530.00 Cleanout, PVC, 8" D - 17 $ 200.00 Each Culvert, PVC, 4" D - 18 $ 10.00 LF 14 140.00 Culvert, PVC, 6" D - 19 $ 13.00 LF 308 4,004.00 Culvert, PVC, 8" D - 20 $ 15.00 LF Culvert, PVC, 12" D - 21 $ 23.00 LF 7 161.00 4 92.00 Culvert, CMP, 8" D - 22 $ 19.00 LF Culvert, CMP, 12" D - 23 $ 29.00 LF Culvert, CMP, 15" D - 24 $ 35.00 LF Culvert, CMP, 18" D - 25 $ 41.00 LF Culvert, CMP, 24" D - 26 $ 56.00 LF Culvert, CMP, 30" D - 27 $ 78.00 LF Culvert, CMP, 36" D - 28 $ 130.00 LF 28 3,640.00 Culvert, CMP, 48" D - 29 $ 190.00 LF Culvert, CMP, 60" D - 30 $ 270.00 LF Culvert, CMP, 72" D - 31 $ 350.00 LF Page 6 of 9 SUBTOTAL 6,461.00 17,406.00 Unit prices updated: 03/02/2015 "KCC 27A authorizes only one bond reduction. Version: 03/02/2015 KC BQ Worksheet_Complete Report Date: 6/10/2021 Site Improvement Bond Quantity Worksheet Web date: 04/03/2015 DRAINAGE CONTINUED Existing Right-of-way Future Public Right of Way & Drainage Facilities Private Improvements No. Unit Price Unit Quant. Cost Quant. Cost Quant. Cost Culvert, Concrete, 8" D - 32 $ 25.00 LF Culvert, Concrete, 12" D - 33 $ 36.00 LF Culvert, Concrete, 15" D - 34 $ 42.00 LF Culvert, Concrete, 18" D - 35 $ 48.00 LF Culvert, Concrete, 24" D - 36 $ 78.00 LF Culvert, Concrete, 30" D - 37 $ 125.00 LF Culvert, Concrete, 36" D - 38 $ 150.00 LF Culvert, Concrete, 42" D - 39 $ 175.00 LF Culvert, Concrete, 48" D - 40 $ 205.00 LF Culvert, CPP, 6" D - 41 $ 14.00 LF Culvert, CPP, 8" D - 42 $ 16.00 LF Culvert, CPP, 12" D - 43 $ 24.00 LF Culvert, CPP, 15" D - 44 $ 35.00 LF Culvert, CPP, 18" D - 45 $ 41.00 LF Culvert, CPP, 24" D - 46 $ 56.00 LF Culvert, CPP, 30" D - 47 $ 78.00 LF Culvert, CPP, 36" D - 48 $ 130.00 LF Ditching D - 49 $ 9.50 CY Flow Dispersal Trench (1,436 base+) D - 50 $ 28.00 LF French Drain (3' depth) D - 51 $ 26.00 LF Geotextile, laid in trench, polypropylene D - 52 $ 3.00 SY Mid -tank Access Riser, 48" dia, 6' deep D - 54 $ 2,000.00 Each Pond Overflow Spillway D - 55 $ 16.00 SY Restrictor/Oil Separator, 12" D - 56 $ 1,150.00 Each Restrictor/Oil Separator, 15" D - 57 $ 1,350.00 Each Restrictor/Oil Separator, 18" D - 58 $ 1,700.00 Each Riprap, placed D - 59 $ 42.00 CY Tank End Reducer (36" diameter) D - 60 $ 1,200.00 Each Trash Rack, 12" D - 61 $ 350.00 Each Trash Rack, 15" D - 62 $ 410.00 Each Trash Rack, 18" 1 D - 63 $ 480.00 1 Each Trash Rack, 21" 1 D - 64 1 $ 550.00 1 Each Page 7 of 9 SUBTOTAL Unit prices updated: 03/02/2015 "KCC 27A authorizes only one bond reduction. Version: 03/02/2015 KC BQ Worksheet_Complete Report Date: 6/10/2021 Site Improvement Bond Quantity Worksheet Web date: 04/03/2015 Existing Right-of-way Future Public Right of Way & Drainage Facilities Private Improvements Unit Price Unit Quant. Price Quant. I Cost Quant. Cost PARKING LOT SURFACING Not To Be Used For Roads Or Shoulders No. 2" AC, 2" top course rock & 4" borrow PL - 1 $ 21.00 SY NA NA 2" AC, 1.5" top course & 2.5" base cours PL - 2 $ 28.00 SY NA NA 4" select borrow PL - 3 $ 5.00 SY NA NA 1.5" top course rock & 2.5" base course PL - 4 $ 14.00 SY NA NA UTILITY POLES & STREET LIGHTING Utility pole relocation costs must be accompanied by Franchise Utility's Cost Estimate Utility Pole(s) Relocation UP-1 Lump Sum Street Light Poles w/Luminaires UP-2 $ 7,500.00 1 Each WRITE -IN -ITEMS (Such as detention/water quality vaults.) No. Remove OHP, Install UGP WI-3 $ 5,000.00 LS 1 5000 1 5,000.00 New 1"Water Service/Meter/Connection WI-4 $ 1,500.00 LS 3 4500 New Gas Services/Connection WI-5 $ 3,000.00 LS 1 3000 6" Concrete Driveway W 1 - 6 $ 65.00 SY 14 910.00 Concrete Stairs W 1 - 7 $ 50.00 SY 6 300.00 Flow Control Tee W 1 - 8 $ 500.00 EA 1 500.00 Trench Drain WI-9 $ 500.00 LS 1 500.00 Bioretention Planter Box wi - to $ 15,000.00 LS 1 15,000.00 SUBTOTAL 12,500.00 SUBTOTAL (SUM ALL PAGES): 48,742.50 48,600.50 30%CONTINGENCY & MOBILIZATION: 14,622.75 14,580.15 GRANDTOTAL: 63,365.25 63,180.65 COLUMN: B C D Page 8 of 9 Unit prices updated: 03/02/2015 "KCC 27A authorizes only one bond reduction. Version: 03/02/2015 KC BQ Worksheet_Complete Report Date: 6/10/2021 Site Improvement Bond Quantity Worksheet Original bond computations prepared by: Name: Ben Iddins, PE Date: PE Registration Number: 54904 Tel. #: Firm Name: Davido Consulting Group, Inc. Address: 9706 4th Ave NE Suite 300, Seattle, WA 98115 Project No: Stabilization/Erosion Sediment Control (ESC) Existing Right -of -Way Improvements Future Public Right of Way & Drainage Facilities Private Improvements Calculated Quantity Completed Total Right -of Way and/or Site Restoration Bond*/** (First $7,500 of bond* shall be cash.) Performance Bond* Amount (A+B+C+D) = TOTAL Maintenance/Defect Bond* Total I01/1JI:Ei70» ;WeP►1a 7:l LT-11 7104Eel 0P►IDIIi 7:1B1gL"INP►A (A) (B) (C) (D) Web date: 04/03/2015 6/10/2021 206-523-0024 BLD2020-0388 FINANCIAL GUARANTEE REQUIREMENTS PERFORMANCE BOND* MINIMUM BOND* AMOUNT PUBLIC ROAD & DRAINAGE AMOUNT REQUIRED FOR RECORDING OR MAINTENANCE/DEFECT BOND* TEMPORARY OCCUPANCY AT $ 9,679.8 SUBSTANTIAL COMPLETION *** $ 63,365.3 $ 63,180.7 (A+B) $ 73,045.1 (T) $ 136,225.7 Minimum is $2000. T x 0.30 $ 40,867.7 Minimum is $2000. (B+C) x 0.25 = $ 15,841.3 Minimum is $2000. Date: * NOTE: The word "bond" as used in this document means a financial guarantee acceptable to King County. ** NOTE: KCC 27A authorizes right of way and site restoration bonds to be combined when both are required. The restoration requirement shall include the total cost for all TESC as a minimum, not a maximum. In addition, corrective work, both on- and off -site needs to be included. Quantities shall reflect worse case scenarios not just minimum requirements. For example, if a salmonid stream may be damaged, some estimated costs for restoration needs to be reflected in this amount. The 30% contingency and mobilization costs are computed in this quantity. *** NOTE: Per KCC 27A, total bond amounts remaining after reduction shall not be less than 30% of the original amount (T) or as revised by major design changes. REQUIRED BOND* AMOUNTS ARE SUBJECT TO REVIEW AND MODIFICATION BY KING COUNTY Page 9 of 9 Unit prices updated: 03/02/2015 Check out the DDES Web site at www.kinpcounty._poy/permits Version: 03/02/2015 KC BQ Worksheet_Complete Report Date: 6/10/2021