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APPROVED_BLD2023-0312+DRAINAGE REPORT +9.7.2023_9.09.19_AM+3768640C � ENGINEERING civil & structural engineering & planning Avid Landscaping Site Improvements BLD2023-0312 RESUB Sep 07 2023 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT 250 4th Ave S Ste 200 Edmonds, WA 98020 Phone: (425) 778-8500 Fax: (425) 778-5536 DRAINAGE REPORT 7328 2101h St SW & 21019 74th Ave W Edmonds, WA 98026 0910612023 CG Project No.: 22414.20 COMPLIES WITH APPLICABLE CITY STORM CODE Y",&7 a7A-�,,i. P 15. 09/07/2023 Table of Contents Section I — Project Overview Section II — Minimum Requirements Section III — Off -Site Analysis Section IV — Stormwater Pollution Prevention Plan (SWPPP) Narrative Section V — Permanent Stormwater Control Plan Narrative Section VI — Special Reports and/or Studies Section VII — Operation and Maintenance Manual 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Avid Landscaping Site Improvements - 22414.20 Drainage Report September 6, 2023 Section I, Page 1 Section I — Project Overview Section I Summa Overview Existing Condition Developed Condition Overview This drainage report has been prepared for the redevelopment of a 0.17 ac parcel and 0.16 ac parcel currently occupied by two single-family residences (SFR). The proposed improvements consist of the addition of gravel parking surface and concrete parking and walkways. The project results in the addition of 5,730 sf of new/replaced impervious area, and land disturbance will occur across the entire project parcel. The project will address Minimum Requirements #1-9 of the 2019 DOE Stormwater Manual for Western Washington (SWMMWW) and comply with the requirements as modified in the Edmonds Community Development Code Chapter 18.30 (herein referred to as ECDC 18.30) and the June 2022 Addendum to ECDC 18.30 (Edmonds Stormwater Addendum). Site Address: 7328 210th St SW & 21019 74th Ave W, Edmonds, WA 98026 Tax Parcel Numbers: 00566900501001, 00566900500901 Existing Conditions The site is currently developed with two SFRs, a garage, two sheds, and gravel, concrete, and asphalt surfaces. The project parcel is L-shaped. The site is mostly flat, with a small steep slope at the southeast corner of the site. The site is underlain by Vashon advance outwash (HSG B). Infiltration was found to be feasible for the site based on site constraints and soil conditions. The site is in the Halls Creek Watershed. Developed Conditions In the developed condition, gravel and concrete pavements for parking, concrete walkways and frontage improvements will be constructed. The project triggers minimum requirements #1-9 of the SWMMWW and must consider On -Site Stormwater Management (OSM) BMPs from List #2 for all hard surfaces or comply with the LID performance standard. The project will comply with the LID performance standard. Further details on on -site stormwater management can be found in Section V of this report. The project will meet the retrofit requirement per ECDC 18.30.060.D.5.b for the existing impervious area to remain. Stormwater management BMPs will manage at least 25% of the existing impervious area. The requirement is explained in more detail in Section V. 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Avid Landscaping Site Improvements - 22414.20 Drainage Report September 6, 2023 Section I, Page 2 The proposed areas on site (including in the ROW) are as follows: Existing Roof/Pavement to Remain: 4,582 sf (0.11 ac) Landscaping: 5,370 sf (0.12 ac) New Gravel Driveway: 3,756 sf (0.09 ac) New Concrete Walkway/Driveway: 771 sf (0.02 ac) New Concrete Walkway/Driveway (ROW): 1,203 sf (0.03 ac) Total Site Area: 14,479 sf (0.33 ac) Total Site Impervious Area (excludes ROW): 9,109 sf (0.21 ac) Total New/Replaced Impervious Area (includes ROW): 5,730 sf (0.13 ac) MPMJ 7,31,0 I 7r3,15 7303 PROJECT SITE � r14 of M r+. N 210( N n L 211J 7F31�3 Figure 1-1 Vicinity Map (Edmonds GIS) C 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Avid Landscaping Site Improvements - 22414.20 September 6, 2023 Drainage Report Section 1, Page 3 Figure 1-2 Aerial Photograph (Edmonds GIS) 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph. 425.778.8500 1 f. 425.778.5536 www.cgengineering.com Avid Landscaping Site Improvements - 22414.20 September 6, 2023 Drainage Report Section II, Page 1 Section II — Minimum Requirements Section II Summa Narrative The project must meet Minimum Requirements #1-9 of the SWMMWW because it is a redevelopment resulting in greater than 5,000 sf of new plus replaced impervious surface area. (See Figure II-1) Minimum Requirement #1: Preparation of Stormwater Site Plans The stormwater site plan consists of this report and the civil drawings and is prepared in accordance with Chapter 3 of Volume 1 of the SWMMWW. Minimum Requirement #2: Stormwater Pollution Prevention Plans (SWPPPs) The SWPPP includes a narrative and drawings. The SWPPP narrative shall include documentation that addresses the 13 elements of Construction Stormwater Pollution Prevention. See Section IV and the civil drawings. A Construction Stormwater General Permit does not need to be submitted to the Washington State Department of Ecology because land disturbance will be under an acre. Minimum Requirement #3: Source Control of Pollution Source control BMPs during construction are described in Section IV, which addresses Minimum Requirement #2. It is anticipated that permanent source control BMPs may be required per the activities listed in Vol IV Ch. 3-5 of the SWMMWW. See Section IV. Minimum Requirement #4: Preservation of Natural Drainage Systems and Outfalls: Natural drainage patterns shall be maintained, and discharges from the project site shall occur at the natural location, to the maximum extent practicable. The manner by which runoff is discharged from the project site must not cause a significant adverse impact to downstream receiving waters and down -gradient properties. All projects shall submit an off -site qualitative analysis. See Section III. Minimum Requirement #5: On -Site Stormwater Management: The project must evaluate On -Site Stormwater Management BMPs and consider On -Site Stormwater Management BMPs from List #2 for all hard surfaces or comply with the LID performance standard. This project will choose to comply with the LID performance standard. Further details on on -site stormwater management can be found in Section V of this report. Minimum Requirement #6: Runoff Treatment: This requirement applies to the new plus replaced hard surfaces and the converted vegetated areas that will generate pollutants and be conveyed to the public storm system through stormwater runoff. Runoff treatment is not required because the project will result less than 5,000 sf of pollution -generating hard surfaces in a threshold discharge area. 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Avid Landscaping Site Improvements - 22414.20 September 6, 2023 Drainage Report Section 11, Page 2 Minimum Requirement #7: Flow Control: Projects must provide flow control to reduce the impacts of stormwater runoff from hard surfaces and land cover conversions. The requirement below applies to projects that discharge stormwater directly, or indirectly through a conveyance system, into a fresh waterbody. The following circumstances require achievement of the standard flow control requirement for western Washington: i.) Projects in which the total of effective impervious surfaces is 10,000 square feet or more in a threshold discharge area, or ii.) projects that convert 0.75 acres or more of vegetation to lawn or landscape, or iii.) projects that through a combination of hard surfaces and converted vegetation areas cause a 0.15 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 15-minute time steps. The total target effective new/replaced hard surfaces in the site threshold discharge area is 5,730 sf, there is no vegetation to be converted to lawn/landscape, and the difference between predeveloped and mitigated flows is less than 0.15 cfs. Therefore, the project does not require flow control. The WWHM report for the flow increase check can be found in Section III. Minimum Requirement #8: Wetlands Protection: Not applicable. There are no wetlands located in the vicinity of the site. Minimum Requirement #9: Operation and Maintenance: An operation and maintenance manual that is consistent with the provisions in Volume I and Volume V of the SWMMWW is required for proposed Stormwater Treatment and On -Site Stormwater Management facilities. The party (or parties) responsible for maintenance and operation shall be identified in the operation and maintenance manual. For private facilities approved by the City, a copy of the operation and maintenance manual shall be retained on -site or within reasonable access to the site and shall be transferred with the property to the owner. For public facilities, a copy of the operation and maintenance manual shall be retained in the appropriate department. A log of maintenance activity that indicates what actions were taken shall be kept and be available for inspection. 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Avid Landscaping Site Improvements - 22414.20 Drainage Report September 6, 2023 Section II, Page 3 Does the Project result in 2,000 square feet, or more, of new plus replaced hard surface area? OR Does the land disturbing activity total 7,000 square feet or greater? Jye—s No Minimum Requirements #1 through #5 IF apply to the new and replaced hard Minimum Requirement #2 applies. surfaces and the land disturbed. Does the Project add 5,000 square feet or more of new hard surfaces? OR Convert Y4 acres or more of vegetation to lawn or landscaped areas? OR Convert 2.5 acres or more of native vegetation to pasture? Yes No All Minimum Requirements apply ext Question Is this a road to the new hard surfaces and the related project? converted vegetation areas. Yes Does the Project add 5,000 square feet or more of new hard surfaces? Yes I No Is the total of new plus replaced hard surfaces 5,000 1 square feet or more, Do the new hard AND surfaces add 50% or does the value of the proposed improvements - more to the existing No No additional o including interior improvements - exceed 50% of the 10 hard surfaces within requirements. assessed value (or replacement value) of the: the Site? • existing Project Site improvements (for commercial or industrial projects) OR • existing Site improvements (for all other projects) Yes All Minimum Requirements apply to the new and replaced hard surfaces and converted vegetation areas. Yes sol''�� Flow Chart for Determining Requirements for Redevelopment Revised March 2019 DEPARTMENT OF ECOLOGYJPlease see http://www.ecy.wa.gov/copyright.html for copyright notice including permissions, State of Washington limitation of liability, and disclaimer. Figure II-1 Flow Chart Determining Minimum Requirements for New Development (Figure 1-3.2 in the SWMMWW) 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Avid Landscaping Site Improvements - 22414.20 September 6, 2023 Drainage Report Section III, Page 1 Section III — Off -Site Analysis Section III Summary Task 1 — Define and map the study area Task 2 — Review all available information of the study area Task 3 — Field inspect the area Task 4 - Describe the drainage system, and its existing and predicted problems An offsite analysis has been prepared per Chapter 3, Volume I of the SWMMWW. It shall assess the potential off -site water quality, erosion, slope stability, and drainage impacts associated with the project and propose appropriate mitigation of those impacts. An initial qualitative analysis shall extend downstream for the entire flow path from the project site to the receiving water or up to one mile, whichever is less. If a receiving waterbody is within one -quarter mile, the analysis shall extend within the receiving water to one -quarter mile from the project site. Task 1— Define and map the study area The study area is defined as the entire flow path from the project site to the receiving waterbody or up to one mile, whichever is less. Per the survey and site visit, runoff flows either south or west from the site into stormwater mains along 2101" St SW of 74t" Ave W. Runoff continues east on 212t" St SW before being routed south on 74t" Ave W to the quarter mile mark. The site is in the Halls Creek drainage basin. Task 2 — Review all available information on the studv area Online information was reviewed from the Edmonds GIS Map and the survey. There is an existing landslide/erosion hazard area near the east boundary of the site. Figure III-1 depicts the study area from the Edmonds GIS Map. The existing drainage system consists of roof downspouts which disperse stormwater in the natural flow direction. There is no drainage system in place for other hard surfaces, and stormwater is dispersed in the natural flow direction. 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Avid Landscaping Site Improvements - 22414.20 Drainage Report September 6, 2023 Section III, Page 2 PD10-19 o � OF [P_jD.J0M%7tMTTf SV 8* PROJECT SITE 0 Q h o 00 �- 0 o 0 0 t 0 0 O I 0 O PD,,10-11 ♦ r� 0.12 mi No h+ PD14-8 0 ♦ O F-' L' I V rAU '"W ♦ I»I I ❑ o 0 0 ❑ Q�= 0 .I - 1406 0 0 U u Cl -I5 >T A--- 0 Cn PD10-40 3 PD14 -39 J 3 MILE MARK 00 VUl4-V 0 1 fiftvtSW Figure III-1 Study Area 4 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Avid Landscaping Site Improvements - 22414.20 September 6, 2023 Drainage Report Section III, Page 3 Task 3 — Field inspect the study area The upstream and downstream conditions were observed. The site does not take on any significant upstream runoff. The downstream conditions were observed to be the same as what is described in Task 1. Task 4 — Describe the drainage system, and its existing and predicted problems There do not appear to be any problems with the current site drainage condition. In the proposed condition, new and replaced site impervious areas will be routed to a fully infiltration infiltration trench with an overflow to the storm system on 210th St SW via a splashblock. Runoff from new impervious areas in the ROW will follow the curb lines to existing catch basins in the ROW of 210th St SW and 74th Ave W. No problems are predicted with the proposed system. Figure III-2: from the project site on 741h Ave W, facing south (downstream). 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Avid Landscaping Site Improvements - 22414.20 September 6, 2023 Drainage Report Section III, Page 4 Figure III-3: from the project site frontage on 2101" St SW, facing east (downstream). 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Avid Landscaping Site Improvements - 22414.20 Drainage Report September 6, 2023 Section III, Page 5 Figure III-4: from the north side of the intersection of 72"d Ave W and 212t' St SW, facing south towards the % mile mark. C 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Avid Landscaping Site Improvements - 22414.20 September 6, 2023 Drainage Report Section IV, Page 1 Section IV — Stormwater Pollution Prevention Plan (SWPPP) Narrative Section IV Summary Narrative Land disturbance will occur on the entire project parcel. Erosion control details will be provided consistent with City of Edmonds guidelines. An erosion control plan sheet is provided in full size as a part of the civil drawing set. Sediment and Erosion Best Management Practices (BMPs) are addressed as follows: Element 1: Mark Clearing Limits To protect adjacent properties and to reduce the area of soil exposed to construction, the limits of construction will be clearly marked before land -disturbing activities begin. Clearing limits will be to the extents of necessary land disturbance for the project's improvements. The BMPs relevant to marking the clearing limits that will be applied for this project include: High Visibility Plastic or Metal Fence (BMP C103) Element 2: Establish Construction Access Construction access or activities occurring on unpaved areas shall be minimized, yet where necessary, access points shall be stabilized to minimize the tracking of sediment onto public roads. The existing entrance to the site may be used as a stabilized construction entrance and expanded to the 15' minimum as necessary: Stabilized Construction Entrance (BMP C105) Element 3: Control Flow Rates The site is generally flat. The site is small enough that a silt fence used for Element 4 may be used to control flow rates. The suggested BMPs include: Silt Fence (BMP C233) Element 4: Install Sediment Controls All stormwater runoff from disturbed areas shall pass through an appropriate sediment removal BMP before leaving the construction site or prior to being discharged. Silt fence will be installed along the downstream property lines. Pollution prevention facilities on the erosion control plan must be constructed prior to or in conjunction with all clearing and grading to ensure that the transport of sediment to surface waters and adjacent properties is minimized. The specific BMPs to be used for controlling sediment on this project include: Silt Fence (BMP C233) 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Avid Landscaping Site Improvements - 22414.20 Drainage Report September 6, 2023 Section IV, Page 2 Element 5: Stabilize Soils Exposed and unworked soils shall be stabilized with the application of effective BMPs to prevent erosion throughout the life of the project. The specific BMPs for soil stabilization that shall be used on this project include: Temporary and Permanent Seeding (BMP C120) Mulching (BMP C121) Nets and Blankets (BMP C122) Plastic Covering (BMP C123) Sodding (BMP C124) Topsoiling/Composting (BMP C125) Surface Roughening (BMP C130) Dust Control (BMP C140) Element 6: Protect Slopes Exposed slopes shall be stabilized with BMPs found in Element 5. Element 7: Protect Drain Inlets Existing drain inlets along 210th St SW, 74th Ave W, and those that are made operable during construction must be protected from sedimentation. Stormwater shall not enter the conveyance system without first being filtered or treated to remove sediment. Inlet protection devices shall be cleaned or removed and replaced when sediment has filled one-third of the available storage (or as specified by the manufacturer). The specific BMPs to be used for protecting drain inlets are: Storm Drain Inlet Protection (BMP C220) Element 8: Stabilize Channels and Outlets Conveyance channels are not located on or in the immediate vicinity of the site. Element 9: Control Pollutants Design, install, implement, and maintain effective pollution prevention measures to minimize the discharge of pollutants. The suggested BMPs are: Concrete Handling (BMP C151) Sawcutting and Surfacing Pollution Prevention (BMP C152) Material Delivery, Storage and Containment (BMP C153) Element 10: Control Dewatering Dewatering is not anticipated. 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Avid Landscaping Site Improvements - 22414.20 Drainage Report September 6, 2023 Section IV, Page 3 Element 11: Maintain BMPs All temporary and permanent erosion and sediment control BMPs shall be maintained and repaired as needed to ensure continued performance of their intended function. Element 12: Manage the Project • Phase development projects to the maximum degree practicable and consider seasonal work limits. • Inspection and monitoring— Inspect, maintain, and repair all BMPs as needed to assure continued performance of their intended function. Conduct site inspections and monitoring in accordance with the Construction Stormwater General Permit or local plan approval authority. • Maintain an Updated Construction SWPPP - This SWPPP shall be retained on -site or within reasonable access to the site. - The SWPPP shall be modified whenever there is a change in the design, construction, operation, or maintenance at the construction site that has, or could have, a significant effect on the discharge of pollutants to waters of the state. - The SWPPP shall be modified if, during inspections or investigations conducted by the owner/operator, or the applicable local or state regulatory authority, it is determined that the SWPPP is ineffective in eliminating or significantly minimizing pollutants in stormwater discharges from the site. The SWPPP shall be modified as necessary to include additional or modified BMPs designed to correct problems identified. Revisions to the SWPPP shall be completed within seven (7) days following the inspection. Element 13: Protect Low Impact Development BMPs The site proposes to use an infiltration trench for stormwater management on site. The trench area should be protected from compaction by placing high visibility orange fencing around the proposed trench area during construction. Permanent Source Control BMPs The site may be used for the storage or transfer of raw materials and will consider S429 BMPs for Storage or Transfer (Outside) of Solid Raw Materials, Byproducts, or Finished Products. The site will install a manufactured treatment device for stormwater pretreatment. This is explained further in Section V. 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 l f.425.778.5536 www.cgengineering.com Avid Landscaping Site Improvements - 22414.20 September 6, 2023 Drainage Report Section V, Page 1 Section V — Permanent Stormwater Control Plan Narrative Section V Summary On -Site Stormwater Management BMPs WWHM Reports Alrrrrrytivo The project triggers Minimum Requirements #1-9 of the SWMMWW. It must address Minimum Requirement#5: On -Site Stormwater Management BMPs. Runoff treatment is not required for the project since the total PGHS on site is less than 5,000 sf. Flow Control is not required since the project does not result in a greater than 0.15 cfs 100-year flow increase from the predeveloped to developed condition of the site. Refer to the WWHM report attached at the end of this section for the flow increase calculation. On -Site Stormwater Management The project proposes to utilize a gravel infiltration trench to meet the LID Duration Standard. The trench is designed to infiltration 100% of the flow control standard, and will have an overflow near the northeast corner of the site. The trench is sized to include ROW areas and will overflow to the storm main on 210th St SW. Refer to the WWHM report at the end of this section. The project will meet the retrofit requirement per ECDC 18.30.060.D.5.b, and the infiltration trench will manage at least 1,145 additional square feet, or approximately 25% of the existing impervious areas. The project proposes to route existing roof drains to the infiltration trench. The existing roof area to be rerouted is 1,375 sf (0.03 ac), and the retrofit requirement is expected to be met. A pretreatment BMP is required upstream of the infiltration trench. The project will use Contech CDS as the manufactured treatment device for pretreatment. Refer to sheet C3.4 of the civil plans. 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com WWHM2012 PROJECT REPORT Project Name: Avid Landscaping Flow Control Check 03.09.23 Site Name: Site Address: City Report Date: 3/9/2023 MGS Regoin Puget East Data Start 1901/10/1 Data End : 2058/09/30 DOT Data Number: 03 Version Date: 2019/09/13 Version : 4.2.17 Low Flow Threshold for POC 1 : 50 Percent of the 2 Year High Flow Threshold for POC 1: 50 year PREDEVELOPED LAND USE Name : Basin 1 Bypass: No Groundwater: No Pervious Land Use acre A B. Forest, Flat .33 Pervious Total 0.33 Impervious Land Use acre Impervious Total 0 Basin Total 0.33 Element Flows To: Surface Interflow Groundwater MITIGATED LAND USE Name : Basin 1 Bypass: No GroundWater: No Pervious Land Use acre A B. Lawn, Flat .12 Pervious Total 0.12 Impervious Land Use acre ROOF TOPS FLAT 0.11 SIDEWALKS FLAT 0.1 Impervious Total 0.21 Basin Total 0.33 Element Flows To: Surface Interflow ANALYSIS RESULTS Stream Protection Duration Predeveloped Landuse Totals for POC #1 Total Pervious Area:0.33 Total Impervious Area:O Mitigated Landuse Totals for POC #1 Total Pervious Area:0.12 Total Impervious Area:0.21 Groundwater Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 5 year 10 year 25 year 50 year 100 year 0.00007 0.000073 0.000075 0.000077 0.000078 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.052397 5 year 0.069279 10 year 0.081407 25 year 0.097851 50 year 0.110939 100 year 0.124768 Stream Protection Duration Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1902 0.000 0.058 1903 0.000 0.065 1904 0.000 0.073 1905 0.000 0.034 1906 0.000 0.039 1907 0.000 0.052 1908 0.000 0.046 1909 0.000 0.060 1910 0.000 0.054 1911 0.000 0.057 1912 0.000 0.104 1913 0.000 0.034 1914 0.000 0.133 1915 0.000 0.036 1916 0.000 0.057 1917 0.000 0.035 1918 0.000 0.052 1919 0.000 0.031 1920 0.000 0.045 1921 0.000 0.033 1922 0.000 0.046 1923 0.000 0.048 1924 0.000 0.062 1925 0.000 0.034 1926 0.000 0.066 1927 0.000 0.047 1928 0.000 0.043 1929 0.000 0.071 1930 0.000 0.081 1931 0.000 0.037 1932 0.000 0.043 1933 0.000 0.041 1934 0.000 0.068 1935 0.000 0.039 1936 0.000 0.041 1937 0.000 0.058 1938 0.000 0.039 1939 0.000 0.054 1940 0.000 0.074 1941 0.000 0.062 1942 0.000 0.057 1943 0.000 0.064 1944 0.000 0.095 1945 0.000 0.064 1946 0.000 0.045 1947 0.000 0.041 1948 0.000 0.052 1949 0.000 0.084 1950 0.000 0.035 1951 0.000 0.055 1952 0.000 0.090 1953 0.000 0.087 1954 0.000 0.046 1955 0.000 0.040 1956 0.000 0.032 1957 0.000 0.046 1958 0.000 0.060 1959 0.000 0.057 1960 0.000 0.045 1961 0.000 0.127 1962 0.000 0.051 1963 0.000 0.035 1964 0.000 0.091 1965 0.000 0.056 1966 0.000 0.042 1967 0.000 0.046 1968 0.000 0.042 1969 0.000 0.047 1970 0.000 0.055 1971 0.000 0.057 1972 0.000 0.167 1973 0.000 0.092 1974 0.000 0.070 1975 0.000 0.080 1976 0.000 0.069 1977 0.000 0.032 1978 0.000 0.059 1979 0.000 0.053 1980 0.000 0.052 1981 0.000 0.060 1982 0.000 0.043 1983 0.000 0.060 1984 0.000 0.057 1985 0.000 0.055 1986 0.000 0.037 1987 0.000 0.059 1988 0.000 0.039 1989 0.000 0.038 1990 0.000 0.040 1991 0.000 0.065 1992 0.000 0.065 1993 0.000 0.075 1994 0.000 0.049 1995 0.000 0.035 1996 0.000 0.051 1997 0.000 0.042 1998 0.000 0.054 1999 0.000 0.059 2000 0.000 0.059 2001 0.000 0.054 2002 0.000 0.077 2003 0.000 0.040 2004 0.000 0.069 2005 0.000 0.100 2006 0.000 0.044 2007 0.000 0.061 2008 0.000 0.048 2009 0.000 0.046 2010 0.000 0.057 2011 0.000 0.039 2012 0.000 0.058 2013 0.000 0.043 2014 0.000 0.046 2015 0.000 0.079 2016 0.000 0.037 2017 0.000 0.085 2018 0.000 0.060 2019 0.000 0.074 2020 0.000 0.063 2021 0.000 0.058 2022 0.000 0.075 2023 0.000 0.082 2024 0.000 0.113 2025 0.000 0.045 2026 0.000 0.050 2027 0.000 0.060 2028 0.000 0.028 2029 0.000 0.044 2030 0.000 0.068 2031 0.000 0.032 2032 0.000 0.037 2033 0.000 0.040 2034 0.000 0.043 2035 0.000 0.056 2036 0.000 0.040 2037 0.000 0.056 2038 0.000 0.054 2039 0.000 0.088 2040 0.000 0.045 2041 0.000 0.052 2042 0.000 0.061 2043 0.000 0.070 2044 0.000 0.048 2045 0.000 0.044 2046 0.000 0.043 2047 0.000 0.058 2048 0.000 0.048 2049 0.000 0.072 2050 0.000 0.044 2051 0.000 0.073 2052 0.000 0.046 2053 0.000 0.048 2054 0.000 0.073 2055 0.000 0.046 2056 0.000 0.061 2057 0.000 0.037 2058 0.000 0.066 Stream Protection Duration Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.0001 0.1665 2 0.0001 0.1334 3 0.0001 0.1266 4 0.0001 0.1133 5 0.0001 0.1042 6 0.0001 0.0997 7 0.0001 0.0945 8 0.0001 0.0923 9 0.0001 0.0912 10 0.0001 0.0904 11 0.0001 0.0879 12 0.0001 0.0874 13 0.0001 0.0846 14 0.0001 0.0841 15 0.0001 0.0820 16 0.0001 0.0810 17 0.0001 0.0796 18 0.0001 0.0792 19 0.0001 0.0768 20 0.0001 0.0754 21 0.0001 0.0753 22 0.0001 0.0736 23 0.0001 0.0736 24 0.0001 0.0735 25 0.0001 0.0735 26 0.0001 0.0729 27 0.0001 0.0724 28 0.0001 0.0714 29 0.0001 0.0700 30 0.0001 0.0697 31 0.0001 0.0688 32 0.0001 0.0686 33 0.0001 0.0684 34 0.0001 0.0680 35 0.0001 0.0663 36 0.0001 0.0658 37 0.0001 0.0651 38 0.0001 0.0649 39 0.0001 0.0647 40 0.0001 0.0645 41 0.0001 0.0643 42 0.0001 0.0626 43 0.0001 0.0624 44 0.0001 0.0620 45 0.0001 0.0612 46 0.0001 0.0611 47 0.0001 0.0609 48 0.0001 0.0604 49 0.0001 0.0603 50 0.0001 0.0602 51 0.0001 0.0598 52 0.0001 0.0597 53 0.0001 0.0596 54 0.0001 0.0590 55 0.0001 0.0590 56 0.0001 0.0589 57 0.0001 0.0586 58 0.0001 0.0584 59 0.0001 0.0581 60 0.0001 0.0581 61 0.0001 0.0581 62 0.0001 0.0577 63 0.0001 0.0572 64 0.0001 0.0571 65 0.0001 0.0571 66 0.0001 0.0569 67 0.0001 0.0569 68 0.0001 0.0568 69 0.0001 0.0568 70 0.0001 0.0563 71 0.0001 0.0562 72 0.0001 0.0562 73 0.0001 0.0554 74 0.0001 0.0553 75 0.0001 0.0550 76 0.0001 0.0541 77 0.0001 0.0540 78 0.0001 0.0538 79 0.0001 0.0538 80 0.0001 0.0535 81 0.0001 0.0534 82 0.0001 0.0524 83 0.0001 0.0520 84 0.0001 0.0519 85 0.0001 0.0519 86 0.0001 0.0517 87 0.0001 0.0511 88 0.0001 0.0506 89 0.0001 0.0500 90 0.0001 0.0487 91 0.0001 0.0484 92 0.0001 0.0484 93 0.0001 0.0483 94 0.0001 0.0482 95 0.0001 0.0480 96 0.0001 0.0469 97 0.0001 0.0468 98 0.0001 0.0464 99 0.0001 0.0464 100 0.0001 0.0463 101 0.0001 0.0462 102 0.0001 0.0461 103 0.0001 0.0459 104 0.0001 0.0458 105 0.0001 0.0456 106 0.0001 0.0456 107 0.0001 0.0452 108 0.0001 0.0449 109 0.0001 0.0448 110 0.0001 0.0447 111 0.0001 0.0446 112 0.0001 0.0442 113 0.0001 0.0442 114 0.0001 0.0441 115 0.0001 0.0437 116 0.0001 0.0431 117 0.0001 0.0430 118 0.0001 0.0429 119 0.0001 0.0429 120 0.0001 0.0427 121 0.0001 0.0425 122 0.0001 0.0423 123 0.0001 0.0418 124 0.0001 0.0416 125 0.0001 0.0415 126 0.0001 0.0415 127 0.0001 0.0407 128 0.0001 0.0404 129 0.0001 0.0400 130 0.0001 0.0399 131 0.0001 0.0398 132 0.0001 0.0398 133 0.0001 0.0394 134 0.0001 0.0389 135 0.0001 0.0389 136 0.0001 0.0387 137 0.0001 0.0386 138 0.0001 0.0375 139 0.0001 0.0373 140 0.0001 0.0371 141 0.0001 0.0370 142 0.0001 0.0368 143 0.0001 0.0367 144 0.0001 0.0358 145 0.0001 0.0354 146 0.0001 0.0351 147 0.0001 0.0351 148 0.0001 0.0348 149 0.0001 0.0343 150 0.0000 0.0341 151 0.0000 0.0340 152 0.0000 0.0333 153 0.0000 0.0318 154 0.0000 0.0317 155 0.0000 0.0316 156 0.0000 0.0306 157 0.0000 0.0278 Stream Protection Duration POC #1 The Facility FAILED Facility FAILED duration standard for 1+ flows. Flow(cfs) Predev Mit Percentage Pass/Fail 0.0000 3176 385076 12124 Fail 0.0000 3103 384113 12378 Fail 0.0000 3006 382874 12736 Fail 0.0000 2918 381911 13088 Fail 0.0000 2827 380810 13470 Fail 0.0000 2746 379571 13822 Fail 0.0000 2691 378608 14069 Fail 0.0000 2629 377645 14364 Fail 0.0000 2552 376544 14754 Fail 0.0000 2481 375718 15143 Fail 0.0000 2386 374617 15700 Fail 0.0000 2289 373516 16317 Fail 0.0000 2243 372690 16615 Fail 0.0000 2174 371727 17098 Fail 0.0000 2104 370763 17621 Fail 0.0000 2053 369938 18019 Fail 0.0000 1996 368837 18478 Fail 0.0000 1935 368148 19025 Fail 0.0000 1870 367185 19635 Fail 0.0000 1813 366359 20207 Fail 0.0000 1767 365671 20694 Fail 0.0000 1700 364708 21453 Fail 0.0000 1642 363744 22152 Fail 0.0000 1603 362919 22639 Fail 0.0000 1561 359616 23037 Fail 0.0000 1503 357551 23789 Fail 0.0000 1470 356863 24276 Fail 0.0000 1411 356037 25232 Fail 0.0000 1363 355212 26061 Fail 0.0000 1331 354524 26635 Fail 0.0000 1286 353698 27503 Fail 0.0000 1248 352872 28275 Fail 0.0000 1216 352322 28973 Fail 0.0000 1166 351633 30157 Fail 0.0000 1134 350945 30947 Fail 0.0000 1082 350120 32358 Fail 0.0000 1038 349294 33650 Fail 0.0000 1006 348743 34666 Fail 0.0000 971 348055 35845 Fail 0.0000 939 347229 36978 Fail 0.0000 912 346679 38013 Fail 0.0001 881 345991 39272 Fail 0.0001 849 345303 40671 Fail 0.0001 818 344615 42128 Fail 0.0001 778 343926 44206 Fail 0.0001 743 343238 46196 Fail 0.0001 717 342688 47794 Fail 0.0001 677 342000 50516 Fail 0.0001 639 341449 53434 Fail 0.0001 613 340899 55611 Fail 0.0001 593 340210 57370 Fail 0.0001 563 339798 60354 Fail 0.0001 540 339109 62797 Fail 0.0001 511 338421 66227 Fail 0.0001 483 337871 69952 Fail 0.0001 457 337320 73811 Fail 0.0001 435 336632 77386 Fail 0.0001 413 336082 81375 Fail 0.0001 387 335531 86700 Fail 0.0001 362 334981 92536 Fail 0.0001 348 334430 96100 Fail 0.0001 322 333880 103689 Fail 0.0001 297 333192 112185 Fail 0.0001 279 332779 119275 Fail 0.0001 260 332228 127780 Fail 0.0001 239 331540 138719 Fail 0.0001 219 331127 151199 Fail 0.0001 183 330577 180643 Fail 0.0001 160 330164 206352 Fail 0.0001 135 329613 244157 Fail 0.0001 111 329063 296453 Fail 0.0001 92 328650 357228 Fail 0.0001 73 328099 449450 Fail 0.0001 59 327549 555167 Fail 0.0001 45 327136 726968 Fail 0.0001 30 326586 1088620Fail 0.0001 13 326035 2507961Fail 0.0001 4 325622 8140550Fail 0.0001 4 325209 8130225Fail 0.0001 4 324659 8116475Fail 0.0001 4 324246 8106150Fail 0.0001 4 323695 8092375Fail 0.0001 4 323145 8078625Fail 0.0001 4 322870 8071750Fail 0.0001 4 322319 8057975Fail 0.0001 4 321906 8047650Fail 0.0001 4 321356 8033900Fail 0.0001 4 320943 8023575Fail 0.0001 4 320530 8013250Fail 0.0001 4 319980 7999500Fail 0.0001 4 319567 7989175Fail 0.0001 4 319154 7978850Fail 0.0001 4 318741 7968525Fail 0.0001 4 318328 7958200Fail 0.0001 4 317915 7947875Fail 0.0001 4 317502 7937550Fail 0.0001 4 317089 7927225Fail 0.0001 4 316677 7916925Fail 0.0001 4 316264 7906600Fail 0.0001 4 315851 7896275Fail The development has an increase in flow durations from 1/2 Predeveloped 2 year flow to the 2 year flow or more than a 10% increase from the 2 year to the 50 year flow. The development has an increase in flow durations for more than 50% of the flows for the range of the duration analysis. Water Quality BMP Flow and Volume for POC #1 On-line facility volume: 0 acre-feet On-line facility target flow: 0 cfs. Adjusted for 15 min: 0 cfs. Off-line facility target flow: 0 cfs. Adjusted for 15 min: 0 cfs. 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 Standard 8 Duration Analysis Result = Failed Perind and Impind Changes No changes have been made. 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. 2005-2023; All Rights Reserved. WWHM2012 PROJECT REPORT Project Name: Avid Landscape Infiltration 08.24.23 Site Name: Site Address: City Report Date: 9/6/2023 MGS Regoin Puget East Data Start 1901/10/1 Data End : 2058/09/30 DOT Data Number: 03 Version Date: 2019/09/13 Version : 4.2.17 Low Flow Threshold for POC 1 : 50 Percent of the 2 Year High Flow Threshold for POC 1: 50 year PREDEVELOPED LAND USE Name : Basin 1 Bypass: No Groundwater: No Pervious Land Use acre .16 Pervious Total 0.16 Impervious Land Use acre Impervious Total 0 Basin Total 0.16 Element Flows To: Surface Interflow Groundwater MITIGATED LAND USE Name : Basin 1 Bypass: No GroundWater: No Pervious Land Use acre Pervious Total Impervious Land Use ROOF TOPS FLAT SIDEWALKS FLAT PARKING FLAT Impervious Total Basin Total Element Flows To: Surface Gravel Trench Bed 1 0 acre 0.03 0.05 0.08 0.16 0.16 Interflow Groundwater Gravel Trench Bed 1 Name : Gravel Trench Bed 1 Bottom Length: 52.00 ft. Bottom Width: 10.00 ft. Trench bottom slope 1: 0 To 1 Trench Left side slope 0: 0 To 1 Trench right side slope 2: 0 To 1 Material thickness of first layer: 3 Pour Space of material for first layer: 0.33 Material thickness of second layer: 0 Pour Space of material for second layer: 0 Material thickness of third layer: 0 Pour Space of material for third layer: 0 Infiltration On Infiltration rate: 2.5 Infiltration safety factor: 1 Total Volume Infiltrated (ac-ft.): 60.497 Total Volume Through Riser (ac-ft.): 0 Total Volume Through Facility (ac-ft.): 60.497 Percent Infiltrated: 100 Total Precip Applied to Facility: 0 Total Evap From Facility: 0 Discharge Structure Riser Height: 2.95 ft. Riser Diameter: 6 in. Element Flows To: Outlet 1 Outlet 2 Gravel Trench Bed Hydraulic Table Stage(feet) Area(ac.) volume(ac-ft.) Discharge(cfs) Infilt(cfs) 0.0000 0.011 0.000 0.000 0.000 0.0333 0.011 0.000 0.000 0.030 0.0667 0.011 0.000 0.000 0.030 0.1000 0.011 0.000 0.000 0.030 0.1333 0.011 0.000 0.000 0.030 0.1667 0.011 0.000 0.000 0.030 0.2000 0.011 0.000 0.000 0.030 0.2333 0.011 0.000 0.000 0.030 0.2667 0.011 0.001 0.000 0.030 0.3000 0.011 0.001 0.000 0.030 0.3333 0.011 0.001 0.000 0.030 0.3667 0.011 0.001 0.000 0.030 0.4000 0.011 0.001 0.000 0.030 0.4333 0.011 0.001 0.000 0.030 0.4667 0.011 0.001 0.000 0.030 0.5000 0.011 0.002 0.000 0.030 0.5333 0.011 0.002 0.000 0.030 0.5667 0.011 0.002 0.000 0.030 0.6000 0.011 0.002 0.000 0.030 0.6333 0.011 0.002 0.000 0.030 0.6667 0.011 0.002 0.000 0.030 0.7000 0.011 0.002 0.000 0.030 0.7333 0.011 0.002 0.000 0.030 0.7667 0.011 0.003 0.000 0.030 0.8000 0.011 0.003 0.000 0.030 0.8333 0.011 0.003 0.000 0.030 0.8667 0.011 0.003 0.000 0.030 0.9000 0.011 0.003 0.000 0.030 0.9333 0.011 0.003 0.000 0.030 0.9667 0.011 0.003 0.000 0.030 1.0000 0.011 0.003 0.000 0.030 1.0333 0.011 0.004 0.000 0.030 1.0667 0.011 0.004 0.000 0.030 1.1000 0.011 0.004 0.000 0.030 1.1333 0.011 0.004 0.000 0.030 1.1667 0.011 0.004 0.000 0.030 1.2000 0.011 0.004 0.000 0.030 1.2333 0.011 0.004 0.000 0.030 1.2667 0.011 0.005 0.000 0.030 1.3000 0.011 0.005 0.000 0.030 1.3333 0.011 0.005 0.000 0.030 1.3667 0.011 0.005 0.000 0.030 1.4000 0.011 0.005 0.000 0.030 1.4333 0.011 0.005 0.000 0.030 1.4667 0.011 0.005 0.000 0.030 1.5000 0.011 0.005 0.000 0.030 1.5333 0.011 0.006 0.000 0.030 1.5667 0.011 0.006 0.000 0.030 1.6000 0.011 0.006 0.000 0.030 1.6333 0.011 0.006 0.000 0.030 1.6667 0.011 0.006 0.000 0.030 1.7000 0.011 0.006 0.000 0.030 1.7333 0.011 0.006 0.000 0.030 1.7667 0.011 0.007 0.000 0.030 1.8000 0.011 0.007 0.000 0.030 1.8333 0.011 0.007 0.000 0.030 1.8667 0.011 0.007 0.000 0.030 1.9000 0.011 0.007 0.000 0.030 1.9333 0.011 0.007 0.000 0.030 1.9667 0.011 0.007 0.000 0.030 2.0000 0.011 0.007 0.000 0.030 2.0333 0.011 0.008 0.000 0.030 2.0667 0.011 0.008 0.000 0.030 2.1000 0.011 0.008 0.000 0.030 2.1333 0.011 0.008 0.000 0.030 2.1667 0.011 0.008 0.000 0.030 2.2000 0.011 0.008 0.000 0.030 2.2333 0.011 0.008 0.000 0.030 2.2667 0.011 0.008 0.000 0.030 2.3000 0.011 0.009 0.000 0.030 2.3333 0.011 0.009 0.000 0.030 2.3667 0.011 0.009 0.000 0.030 2.4000 0.011 0.009 0.000 0.030 2.4333 0.011 0.009 0.000 0.030 2.4667 0.011 0.009 0.000 0.030 2.5000 0.011 0.009 0.000 0.030 2.5333 0.011 0.010 0.000 0.030 2.5667 0.011 0.010 0.000 0.030 2.6000 0.011 0.010 0.000 0.030 2.6333 0.011 0.010 0.000 0.030 2.6667 0.011 0.010 0.000 0.030 2.7000 0.011 0.010 0.000 0.030 2.7333 0.011 0.010 0.000 0.030 2.7667 0.011 0.010 0.000 0.030 2.8000 0.011 0.011 0.000 0.030 2.8333 0.011 0.011 0.000 0.030 2.8667 0.011 0.011 0.000 0.030 2.9000 0.011 0.011 0.000 0.030 2.9333 0.011 0.011 0.000 0.030 2.9667 0.011 0.011 0.011 0.030 3.0000 0.011 0.011 0.059 0.030 ANALYSIS RESULTS Stream Protection Duration Predeveloped Landuse Totals for POC #1 Total Pervious Area:0.16 Total Impervious Area:O Mitigated Landuse Totals for POC #1 Total Pervious Area:O Total Impervious Area:0.16 Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.00003 5 year 0.000034 10 year 25 year 50 year 100 year Flow Frequency Return Return Period 2 year 5 year 10 year 25 year 50 year 100 year 0.000035 0.000037 0.000037 0.000038 Periods for Mitigated Flow(cfs) 0 0 0 0 0 0 Stream Protection Duration Annual Peaks for Predeveloped and Mitigated Year Predeveloped Mitigated 1902 0.000 0.000 1903 0.000 0.000 1904 0.000 0.000 1905 0.000 0.000 1906 0.000 0.000 1907 0.000 0.000 1908 0.000 0.000 1909 0.000 0.000 1910 0.000 0.000 1911 0.000 0.000 1912 0.000 0.000 1913 0.000 0.000 1914 0.000 0.000 1915 0.000 0.000 1916 0.000 0.000 1917 0.000 0.000 1918 0.000 0.000 1919 0.000 0.000 1920 0.000 0.000 1921 0.000 0.000 1922 0.000 0.000 1923 0.000 0.000 1924 0.000 0.000 1925 0.000 0.000 1926 0.000 0.000 1927 0.000 0.000 1928 0.000 0.000 1929 0.000 0.000 1930 0.000 0.000 1931 0.000 0.000 1932 0.000 0.000 1933 0.000 0.000 1934 0.000 0.000 1935 0.000 0.000 1936 0.000 0.000 1937 0.000 0.000 1938 0.000 0.000 1939 0.000 0.000 1940 0.000 0.000 POC #1 POC #1 1941 0.000 0.000 1942 0.000 0.000 1943 0.000 0.000 1944 0.000 0.000 1945 0.000 0.000 1946 0.000 0.000 1947 0.000 0.000 1948 0.000 0.000 1949 0.000 0.000 1950 0.000 0.000 1951 0.000 0.000 1952 0.000 0.000 1953 0.000 0.000 1954 0.000 0.000 1955 0.000 0.000 1956 0.000 0.000 1957 0.000 0.000 1958 0.000 0.000 1959 0.000 0.000 1960 0.000 0.000 1961 0.000 0.000 1962 0.000 0.000 1963 0.000 0.000 1964 0.000 0.000 1965 0.000 0.000 1966 0.000 0.000 1967 0.000 0.000 1968 0.000 0.000 1969 0.000 0.000 1970 0.000 0.000 1971 0.000 0.000 1972 0.000 0.003 1973 0.000 0.000 1974 0.000 0.000 1975 0.000 0.000 1976 0.000 0.000 1977 0.000 0.000 1978 0.000 0.000 1979 0.000 0.000 1980 0.000 0.000 1981 0.000 0.000 1982 0.000 0.000 1983 0.000 0.000 1984 0.000 0.000 1985 0.000 0.000 1986 0.000 0.000 1987 0.000 0.000 1988 0.000 0.000 1989 0.000 0.000 1990 0.000 0.000 1991 0.000 0.000 1992 0.000 0.000 1993 0.000 0.000 1994 0.000 0.000 1995 0.000 0.000 1996 0.000 0.000 1997 0.000 0.000 1998 0.000 0.000 1999 0.000 0.000 2000 0.000 0.000 2001 0.000 0.000 2002 0.000 0.000 2003 0.000 0.000 2004 0.000 0.000 2005 0.000 0.000 2006 0.000 0.000 2007 0.000 0.000 2008 0.000 0.000 2009 0.000 0.000 2010 0.000 0.000 2011 0.000 0.000 2012 0.000 0.000 2013 0.000 0.000 2014 0.000 0.000 2015 0.000 0.000 2016 0.000 0.000 2017 0.000 0.000 2018 0.000 0.000 2019 0.000 0.000 2020 0.000 0.000 2021 0.000 0.000 2022 0.000 0.000 2023 0.000 0.000 2024 0.000 0.000 2025 0.000 0.000 2026 0.000 0.000 2027 0.000 0.000 2028 0.000 0.000 2029 0.000 0.000 2030 0.000 0.000 2031 0.000 0.000 2032 0.000 0.000 2033 0.000 0.000 2034 0.000 0.000 2035 0.000 0.000 2036 0.000 0.000 2037 0.000 0.000 2038 0.000 0.000 2039 0.000 0.000 2040 0.000 0.000 2041 0.000 0.000 2042 0.000 0.000 2043 0.000 0.000 2044 0.000 0.000 2045 0.000 0.000 2046 0.000 0.000 2047 0.000 0.000 2048 0.000 0.000 2049 0.000 0.000 2050 0.000 0.000 2051 0.000 0.000 2052 0.000 0.000 2053 0.000 0.000 2054 0.000 0.000 2055 0.000 0.000 2056 0.000 0.000 2057 0.000 0.000 2058 0.000 0.000 Stream Protection Duration Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.0001 0.0028 2 0.0000 0.0000 3 0.0000 0.0000 4 0.0000 0.0000 5 0.0000 0.0000 6 0.0000 0.0000 7 0.0000 0.0000 8 0.0000 0.0000 9 0.0000 0.0000 10 0.0000 0.0000 11 0.0000 0.0000 12 0.0000 0.0000 13 0.0000 0.0000 14 0.0000 0.0000 15 0.0000 0.0000 16 0.0000 0.0000 17 0.0000 0.0000 18 0.0000 0.0000 19 0.0000 0.0000 20 0.0000 0.0000 21 0.0000 0.0000 22 0.0000 0.0000 23 0.0000 0.0000 24 0.0000 0.0000 25 0.0000 0.0000 26 0.0000 0.0000 27 0.0000 0.0000 28 0.0000 0.0000 29 0.0000 0.0000 30 0.0000 0.0000 31 0.0000 0.0000 32 0.0000 0.0000 33 0.0000 0.0000 34 0.0000 0.0000 35 0.0000 0.0000 36 0.0000 0.0000 37 0.0000 0.0000 38 0.0000 0.0000 39 0.0000 0.0000 40 0.0000 0.0000 41 0.0000 0.0000 42 0.0000 0.0000 43 0.0000 0.0000 44 0.0000 0.0000 45 0.0000 0.0000 46 0.0000 0.0000 47 0.0000 0.0000 48 0.0000 0.0000 49 0.0000 0.0000 50 0.0000 0.0000 51 0.0000 0.0000 52 0.0000 0.0000 53 0.0000 0.0000 54 0.0000 0.0000 55 0.0000 0.0000 56 0.0000 0.0000 57 0.0000 0.0000 58 0.0000 0.0000 59 0.0000 0.0000 60 0.0000 0.0000 61 0.0000 0.0000 62 0.0000 0.0000 63 0.0000 0.0000 64 0.0000 0.0000 65 0.0000 0.0000 66 0.0000 0.0000 67 0.0000 0.0000 68 0.0000 0.0000 69 0.0000 0.0000 70 0.0000 0.0000 71 0.0000 0.0000 72 0.0000 0.0000 73 0.0000 0.0000 74 0.0000 0.0000 75 0.0000 0.0000 76 0.0000 0.0000 77 0.0000 0.0000 78 0.0000 0.0000 79 0.0000 0.0000 80 0.0000 0.0000 81 0.0000 0.0000 82 0.0000 0.0000 83 0.0000 0.0000 84 0.0000 0.0000 85 0.0000 0.0000 86 0.0000 0.0000 87 0.0000 0.0000 88 0.0000 0.0000 89 0.0000 0.0000 90 0.0000 0.0000 91 0.0000 0.0000 92 0.0000 0.0000 93 0.0000 0.0000 94 0.0000 0.0000 95 0.0000 0.0000 96 0.0000 0.0000 97 0.0000 0.0000 98 0.0000 0.0000 99 0.0000 0.0000 100 0.0000 0.0000 101 0.0000 0.0000 102 0.0000 0.0000 103 0.0000 0.0000 104 0.0000 0.0000 105 0.0000 0.0000 106 0.0000 0.0000 107 0.0000 0.0000 108 0.0000 0.0000 109 0.0000 0.0000 110 0.0000 0.0000 111 0.0000 0.0000 112 0.0000 0.0000 113 0.0000 0.0000 114 0.0000 0.0000 115 0.0000 0.0000 116 0.0000 0.0000 117 0.0000 0.0000 118 0.0000 0.0000 119 0.0000 0.0000 120 0.0000 0.0000 121 0.0000 0.0000 122 0.0000 0.0000 123 0.0000 0.0000 124 0.0000 0.0000 125 0.0000 0.0000 126 0.0000 0.0000 127 0.0000 0.0000 128 0.0000 0.0000 129 0.0000 0.0000 130 0.0000 0.0000 131 0.0000 0.0000 132 0.0000 0.0000 133 0.0000 0.0000 134 0.0000 0.0000 135 0.0000 0.0000 136 0.0000 0.0000 137 0.0000 0.0000 138 0.0000 0.0000 139 0.0000 0.0000 140 0.0000 0.0000 141 0.0000 0.0000 142 0.0000 0.0000 143 0.0000 0.0000 144 0.0000 0.0000 145 0.0000 0.0000 146 0.0000 0.0000 147 0.0000 0.0000 148 0.0000 0.0000 149 0.0000 0.0000 150 0.0000 0.0000 151 0.0000 0.0000 152 0.0000 0.0000 153 0.0000 0.0000 154 0.0000 0.0000 155 0.0000 0.0000 156 0.0000 0.0000 157 0.0000 0.0000 Stream Protection Duration POC #1 The Facility PASSED The Facility PASSED. Flow(cfs) Predev Mit Percentage Pass/Fail 0.0000 3187 2 0 Pass 0.0000 3110 2 0 Pass 0.0000 3037 2 0 Pass 0.0000 2945 2 0 Pass 0.0000 2872 2 0 Pass 0.0000 2753 2 0 Pass 0.0000 2699 2 0 Pass 0.0000 2651 2 0 Pass 0.0000 2591 2 0 Pass 0.0000 2488 2 0 Pass 0.0000 2411 2 0 Pass 0.0000 2327 2 0 Pass 0.0000 2268 2 0 Pass 0.0000 2213 2 0 Pass 0.0000 2125 2 0 Pass 0.0000 2084 2 0 Pass 0.0000 2023 2 0 Pass 0.0000 1972 2 0 Pass 0.0000 1883 2 0 Pass 0.0000 1846 2 0 Pass 0.0000 1793 2 0 Pass 0.0000 1735 2 0 Pass 0.0000 1678 2 0 Pass 0.0000 1618 2 0 Pass 0.0000 1584 2 0 Pass 0.0000 1541 2 0 Pass 0.0000 1493 2 0 Pass 0.0000 1427 2 0 Pass 0.0000 1397 2 0 Pass 0.0000 1354 2 0 Pass 0.0000 1313 2 0 Pass 0.0000 1283 2 0 Pass 0.0000 1232 2 0 Pass 0.0000 1194 2 0 Pass 0.0000 1157 2 0 Pass 0.0000 1123 2 0 Pass 0.0000 1065 2 0 Pass 0.0000 1022 2 0 Pass 0.0000 998 2 0 Pass 0.0000 965 2 0 Pass 0.0000 939 2 0 Pass 0.0000 901 2 0 Pass 0.0000 875 2 0 Pass 0.0000 846 2 0 Pass 0.0000 812 2 0 Pass 0.0000 758 2 0 Pass 0.0000 740 2 0 Pass 0.0000 706 2 0 Pass 0.0000 677 2 0 Pass 0.0000 645 2 0 Pass 0.0000 605 2 0 Pass 0.0000 590 2 0 Pass 0.0000 562 2 0 Pass 0.0000 541 2 0 Pass 0.0000 505 2 0 Pass 0.0000 479 2 0 Pass 0.0000 457 2 0 Pass 0.0000 436 2 0 Pass 0.0000 418 2 0 Pass 0.0000 385 2 0 Pass 0.0000 364 2 0 Pass 0.0000 348 2 0 Pass 0.0000 328 2 0 Pass 0.0000 297 2 0 Pass 0.0000 278 2 0 Pass 0.0000 262 2 0 Pass 0.0000 248 2 0 Pass 0.0000 226 2 0 Pass 0.0000 185 2 1 Pass 0.0000 162 2 1 Pass 0.0000 140 2 1 Pass 0.0000 117 2 1 Pass 0.0000 87 2 2 Pass 0.0000 73 2 2 Pass 0.0000 60 2 3 Pass 0.0000 50 2 4 Pass 0.0000 34 2 5 Pass 0.0000 17 2 11 Pass 0.0000 4 2 50 Pass 0.0000 4 2 50 Pass 0.0000 4 2 50 Pass 0.0000 4 2 50 Pass 0.0000 4 2 50 Pass 0.0000 4 2 50 Pass 0.0000 4 2 50 Pass 0.0000 4 2 50 Pass 0.0000 4 2 50 Pass 0.0000 4 2 50 Pass 0.0000 4 2 50 Pass 0.0000 4 2 50 Pass 0.0000 4 2 50 Pass 0.0000 4 2 50 Pass 0.0000 4 2 50 Pass 0.0000 4 2 50 Pass 0.0000 4 2 50 Pass 0.0000 4 2 50 Pass 0.0000 4 2 50 Pass 0.0000 4 2 50 Pass 0.0000 4 2 50 Pass 0.0000 4 2 50 Pass Water Quality BMP Flow and Volume for POC #1 On-line facility volume: 0 acre-feet On-line facility target flow: 0 cfs. Adjusted for 15 min: 0 cfs. Off-line facility target flow: 0 cfs. Adjusted for 15 min: 0 cfs. LID Report 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 Gravel Trench Bed 1 POC N 55.05 N 100.00 Total Volume Infiltrated 55.05 0.00 0.00 100.00 0.00 0% No Treat. Credit Compliance with LID Standard 8 Duration Analysis Result = Passed Perind and Impind Changes No changes have been made. 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. 2005-2023; All Rights Reserved. Avid Landscaping Site Improvements - 22414.20 Drainage Report September 6, 2023 Section VI, Page 1 Section VI — Special Reports and/or Studies Section VI Summary: 1. Infiltration Test Report by PanGEO, Inc, dated February 24, 2023. 250 4th Avenue South, Suite 200 CM Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com PanGEOC O R P O R A T E D Geotechnical & Earthquake Engineering Consultants February 24, 2023 File No. 23-017.200 Robert Boyker Avid Landscape Management LLC 7328 210 Street SW Edmonds, WA 98026 Subject: Infiltration Test Report Proposed Gravel Parking 21019 74th Avenue West Edmonds, Washington Dear Mr. Boyker, As requested, PanGEO, Inc. completed an infiltration test at 21019 74th Avenue West in Edmonds, Washington. Our service scope consisted of reviewing available geologic and geotechnical data in the site vicinity, observing the excavation of four test pits by the client, performing one small Pilot Infiltration Test (PIT), and preparation of this report. PROJECT BACKGROUND The subject site is a rectangular parcel approximately 0.17 acres in size located at 21019 74th Avenue West in Edmonds, Washington (see Vicinity Map, Figure 1). The subject site is bordered to the west by 74th Avenue West, to the northwest by two single -story buildings occupied by Avid Landscaping, to the northeast by an elevated asphalt parking lot, and to the south and east by asphalt parking for the neighboring office park. The site is occupied by a single -story residence with two sheds. Based on our field observations and review of the topographic survey, the site grade slopes down from west to east with an average gradient of about eight percent. An approximate 4-foot-tall rockery provides a grade -break with the asphalt parking to the east of the site, becoming approximately 12- foot-tall as the rockery wraps around to the southern property boundary. 3213 Eastlake Avenue East, Suite B Seattle, WA 98102 Tel (206) 262-0370 www.pangeoinc.com Infiltration Test Report Proposed Gravel Parking: 21019 74th Avenue W, Edmonds, WA February 24, 2023 We understand the proposed project includes demolishing the existing structures at the site and installing a gravel parking lot. We also understand that it is planned to infiltrate surface water from the planned impervious surfaces into the site soils, provided that the site soils are conducive to infiltration. Based on the information provided to us, the proposed infiltration system may consist of an infiltration trench with facility bottom at about 5 to 6 feet below grade (near Elevation 400') in the middle portion of the site, if feasible. The approximate layout of the site and the location of the infiltration test is shown on Figure 2, Site and Exploration Plan. SITE GEOLOGY AND SUBSURFACE CONDITIONS SITE GEOLOGY Based on our review of the Composite Geologic Map of Sno-King Area, Central Puget Lowland, Washington (Booth, et al, 2004), the project site is underlain by Vashon advance outwash (Map Unit: Qva). Vashon advance outwash (Qva) consists of sand and gravel deposited by meltwater streams emerging from an advancing glacier. Advance outwash has also been glacially overridden and as such is dense to very dense. Advance outwash normally exhibits low to moderate infiltration capability except in upper section where an increase in cobble and gravel content is present. TEST PIT EXCAVATIONS Subsurface exploration for the infiltration assessment at the site included observing the excavation of four test pits (PIT-1 and TP-1 through TP-3) excavated by the client on January 25, 2023. The test pits were excavated to a maximum depth of about 8 feet below existing grade. The approximate locations of the test pits are indicated on the attached Figure 2. Test pits TP-1 through TP-3 were excavated to a depth of about 8 feet to explore the site soil conditions, and to evaluate/assist the infiltration test depth. PIT-1 was completed at a depth of approximately 5 feet for infiltration testing. After the infiltration test was completed, PIT-1 was over -excavated to check for possible groundwater mounding. PIT -I was ultimately terminated at about 8 feet depth. A geologist from PanGEO was present during the field exploration to observe the test pit excavations, obtain representative samples, and to describe and document the soils encountered in the explorations. The soils were logged in general accordance with the 23-017.200 21019 74th Ave W Infiltration Rpt 2 PanGEO, Inc. Infiltration Test Report Proposed Gravel Parking: 21019 74th Avenue W, Edmonds, WA February 24, 2023 system summarized on Figure A-1, Terms and Symbols for Boring and Test Pit Logs. The summary test pit logs are included as Figures A-2 through A-5 in Appendix A, which provides descriptions of the materials encountered, depths to soil contacts, and depths of seepage or caving, if present, observed in the test pit sidewalls. The relative in -situ density of cohesionless soils, or the relative consistency of fine- grained soils, was estimated from the excavating difficulty, probing the sidewalls with a 1/2-inch diameter steel rod, and the stability of the test pit sidewalls. Where soil contacts were gradual or undulating, the average depth of the contact was recorded in the logs. The test pits excavated for this study were backfilled with the excavated soils after the soils were logged. The backfill was tamped with the backhoe bucket and the ground surface leveled. The backfill was not compacted to a dense condition for the structural support. During construction of the project, the earthwork contractor should locate the test pits, remove the loose backfill and replace it with properly compacted structural fill if the test pit is located in the load -bearing structural areas. SOIL CONDITIONS In general, the soils encountered in the test pits consisted of about 21/2 to 4 feet of loose to medium dense silty sand with debris (fill) overlying dense sand with gravel and cobble that extended to a maximum depth of about 8 feet below ground surface, which we interpret as the Vashon advance outwash mapped at the site. Detailed descriptions of the subsurface conditions encountered at the test pit locations are included in Appendix A of this report. GROUNDWATER Groundwater or seepage was not encountered within the excavation depths at the test pit locations at the time of excavation. It should be noted that groundwater or seepage levels will likely fluctuate depending on the season, amount of rainfall, surface water runoff, tides, and other factors. Generally, the water level is higher and seepage rates are greater in the wetter, winter months (typically October through May). 23-017.200 21019 74th Ave W Infiltration Rpt 3 PanGEO, Inc. Infiltration Test Report Proposed Gravel Parking: 21019 74th Avenue W, Edmonds, WA February 24, 2023 INFILTRATION TESTING The field infiltration test was conducted in general accordance with the procedure for the Small Pilot Infiltration Test (PIT) as outlined in the 2019 Washington Department of Ecology Stormwater Management Manual for Western Washington (WDOE Manual) and 2022 Edmonds Community Development Code Chapter 18.30. In general, the test consisted of the following procedure: • A test pit was excavated to the approximate design bottom of the proposed infiltration facilities with a minimum bottom area of 12 square feet. • The test pit was pre-soaked by maintaining a water level of 12 inches above the bottom of the pit. • At the end of the pre-soak period, a flow meter is used to monitor the amount of water needed to maintain a constant head of 12 inches for at least one hour and until a point at which a constant volume of water per time unit is achieved. • At the end of the constant head test, we measure the falling head infiltration rate by shutting off the water flow and recording the drop in water level over regular time intervals for one hour or until all of the water was infiltrated. The field infiltration rate was then calculated based on the final measured volume per time unit, and the surface area of the hole. The results of our tests are summarized in Table 1, below. Based on the soil conditions and test results, we selected the constant head rates of 12.9 inches per hour as the field infiltration rate at 5 feet depth at PIT-1. Table 1— Field Infiltration Test Results Test Pre- Soak Test Test Duration Test Result Soils Location/Depth Duration Stage (hours) (inches/hour) (hours) Constant 1 12.9 SAND with PIT-1 at 5 feet Head gravel (Vashon 6 Advance Falling Head 1 11.3 Outwash) DESIGN INFILTRATION RATE The infiltration test results measured in the field are considered short-term rates. The short-term rate needs to be reduced through correction factors to generate a design 23-017.200 21019 74th Ave W Infiltration Rpt 4 PanGEO, Inc. Infiltration Test Report Proposed Gravel Parking: 21019 74th Avenue W, Edmonds, WA February 24, 2023 infiltration rate. The corrections factors account for site variability and the number of locations tested, test method, and the degree of long-term maintenance and influent control to prevent siltation and bio-buildup. The correction factors to be used with in -situ infiltration measurements are recommended in Table V-5.1, Chapter 5, Volume V of the 2019 Stormwater Management Manual for Western Washington, reproduced as Table 2, on the following page. Table 2 - Correction Factors to be used with In -Situ Saturated Hydraulic Conductivity Measurements to Estimate Design Rates (source: Table V-5.1, Vol. 5, DOE Stormwater Manual) Issue Partial Correction Factor Site variability and number of locations tested CFv = 0.33 to 1.0 Test Method: Large -Scale PIT CFt = 0.75 Small -Scale PIT CFt = 0.50 Grain Size Method CFt = 0.40 Degree of influent control to prevent siltation and bio- CFm = 0.9 buildup The method for calculating the total correction factor is provided below: CFTotal Correction Factor = CFvariability x CFtesting x CFinaintenance The partial correction factor for site variability (CFv) is selected based on the number of locations tested and the consistency of the underlying soil conditions and ranges from 0.33 to 1.0. Based on our experience and engineering judgment, we recommend a correction factor of 0.5 for site variability. From the Table 2 above, the partial correction factor for CFm is 0.9 and the partial correction factor for CFt is 0.5 when using the small- scale PIT method. Using the partial correction factors described above, in our opinion a Total Correction Factor (CFT) of about 0.225 is appropriate. The total correction factor (CFT = CFv x CFM) is then applied to the field rate to obtain a long-term design infiltration rate. The estimated long-term infiltration rate for the infiltration facility is provided in Table 3, below. We recommend that an allowable design rate of 2.9 inches per hour be used for the proposed infiltration trench. 23-017.200 21019 74th Ave W Infiltration Rpt 5 PanGEO, Inc. Infiltration Test Report Proposed Gravel Parking: 21019 74th Avenue W, Edmonds, WA February 24, 2023 Table 3 — Design Infiltration Rate Field Infiltration Rate Long -Term Infiltration Test Location/Depth Rate (inches/hour) (inches/hour) PIT-1 at 5 feet 12.9 2.9 INFILTRATION CONCLUSIONS AND CONSTRUCTION CONSIDERATIONS Based on the testing results and the applied correction factor, it is our opinion that a design infiltration rate of 2.9 inches per hour may be used to size the infiltration trench at PIT-1. Infiltration facilities are post -construction facilities which are designed to improve the quality and manage the volume of stormwater runoff by encouraging natural infiltration on -site. In order to protect the infiltration receptor soils from becoming clogged with sediment and/or compacted during construction, we recommend the following measures be implemented during construction: • The infiltration facilities should be constructed as late in the schedule as feasible and should not be constructed until after the upstream areas are stabilized. • Heavy equipment traffic on prepared subgrades should be limited, especially during wet weather. • If fine grained sediment is deposited or tracked onto the infiltration system subgrade, it should be removed using an excavator with a grade plate, small dozer or vacuum truck. • The subgrade should be scarified prior to placing fill to prevent sealing of the receptor soils. • Structural fill and aggregate base materials should be end -dumped at the edge of the fill area and the material pushed out over the subgrade. 23-017.200 21019 74th Ave W Infiltration Rpt 6 PanGEO, Inc. Infiltration Test Report Proposed Gravel Parking: 21019 74th Avenue W, Edmonds, WA February 24, 2023 • Grading of the infiltration galleries should be accomplished using low -impact earth -moving equipment to prevent compaction of the underlying soils. Wide tracked vehicles such as back hoes, small dozers and bobcats are suggested. Furthermore, infiltration facilities should be located as far away as possible from any footings and basements in order to avoid water migration into adjacent structures and long terms settlement of foundation soils. PanGEO should be retained during construction to observe excavations of infiltration facilities to confirm the infiltration facilities are constructed in the intended soil unit. LIMITATIONS We have prepared this report for use by Avid Landscape Management LLC and the project team. Recommendations contained in this report are based on a site reconnaissance, a subsurface exploration/testing program, review of pertinent subsurface information, and our understanding of the project. The study was performed using a mutually agreed -upon scope of work. This report may be used only by the client and for the purposes stated, within a reasonable time from its issuance. Land use, site conditions (both off and on -site), or other factors including advances in our understanding of applied science, may change over time and could materially affect our findings. Therefore, this report should not be relied upon after 24 months from its issuance. PanGEO should be notified if the project is delayed by more than 24 months from the date of this report so that we may review the applicability of our conclusions considering the time lapse. Within the limitation of scope, schedule, and budget, PanGEO engages in the practice of geotechnical engineering and endeavors to perform its services in accordance with generally accepted professional principles and practices at the time the Report or its contents were prepared. No warranty, express or implied, is made. We trust that the information outlined in this letter meets your need at this time. Please call if you have any questions. Sincerely, 23-017.200 21019 74th Ave W Infiltration Rpt 7 PanGEO, Inc. Infiltration Test Report Proposed Gravel Parking: 21019 74th Avenue W, Edmonds, WA February 24, 2023 5-a� �)_ d*_94�' Bart Weitering, G.I.T. Project Geologist f -LIN C '[ F A.O �b 0212412023 Chien -Lin (Johnny) Chen, P.E. Senior Geotechnical Engineer Enclosures: Figure 1 Vicinity Map Figure 2 Site and Exploration Plan Appendix A Summary Test Pit Logs Figure A-1 Terms and Symbols for Boring and Test Pit Logs Figure A-2 Log of Test Pit PIT-1 Figure A-3 Log of Test Pit TP-1 Figure A-4 Log of Test Pit TP-2 Figure A-5 Log of Test Pit TP-3 23-017.200 21019 74th Ave W Infiltration Rpt 8 PanGEO, Inc. Infiltration Test Report Proposed Gravel Parking: 21019 74th Avenue W, Edmonds, WA February 24, 2023 REFERENCES: Booth, D. B., Cox, B.F., Troost, K. A., and Shimel, S. A., 2004, The Composite Geologic Map of Sno-King Area, Central Puget Lowland, Washington: scale 1: 24, 000. City of Edmonds, 2022, Edmonds Community Development Code Chapter 18.30 Stormwater Management. Washington State Department of Ecology, 2019, Stormwater Management Manual for Western Washington, Volume V, Chapter 5, Publication Number 19-10-021. 23-017.200 21019 74th Ave W Infiltration Rpt 9 PanGEO, Inc. L C Lynndale Park ? x Sierra Q park c v OD Q r v s2a C L W io 196 th St SW Edmonds Communty Coll ono Lynnwood Rdge Gol Course Park Project Site r Gold Park g a� 188thrSt SW > Q F vvlk-o Park Scfllef Lake Park 26i I th St S','4' u Q 2041h St S-N y Q L_ 208 th St SW 1 S'iti Swodrsh Edmonds Ho sprtal a Q = L L 2 20 th St IT 0 � 44 -s Long • a Park 2241h St SW Q � L v m1rJ %'OL C v L J a a c ,p Spokane o Tomato Tacoma ;4SHINGTON C mok Park Base Map: ESRI Topographic Map 07 Yakima NORTH M � kemewc4 Not to Scale M N Poql-d N � N Infiltration Test VICINITY MAP 3 FbnGEO 21019 74th Avenue West 1 N C O R P O R A T E D Edmonds, Washington Project No. 23-017.200 IFigure No. 1 _ �--210TH ST SW P N 8 '1 31" 60.0 • r� wv 8' Evc \p �. �✓ a>S O 24'. 36' EVG LS/N D9 EBAR/CAP vry FROCK'. 0.06'S FROM PROP CDR STEPS — --�� / 11. FENCE COR '-1 - 5.1' W 'A ASPH i i!'•' ,e H E L I n FENCE m 7328 210th St SW rn 56' W 2 I r F WALL 0,3' E m_}} — p ' FENCE COR 4?'r % o 0 9' W GATE `} - po 7i nIL PAVERCONC S 63 -. &ALL WALL f - E P:4VER5 'FENCE F T I T= - _ �`QN W FOUND IRON PIPE F1LDG t F ri 0.121 OF LINE h �►w� 0.1' W _ -.Gk;'(1 1� 0.66'N FROM o - YYhl1 P PROP COR FlLD4r°° sW Z ..i....-.. FENCE CDR Z 8, W X FENCE 0.6'S OF UNE Ok 1.2'E FROM ..�d N ; '�y ..: C{;'.............4i L PROP CDR . m 30• s: FENCE EV) �::: �c > ROW '. U+ •.I%., . ..r.•... �'�..... 0.6'S '.F U'E 1L tD .Y. .%.�: 4i:f.i'r':.:•:_:_•. h 1.6 E F ..... Ci a•::• :..Ew. �. PROP C:i H L _ .: .:•1�,' : i::i{;•:.'•::v:.'Y.`iV'(Y:i - - tr.m FE' E = o....:..::.:.... ip ::fit :.......:.. ........ A _. '•;n:Z41;�.... 89'18.25" E 60. 2' a I pfj E E' SET 'iR" E• 4F j�� l L r I TP-1 REBAR/CAP ;F� ✓' . E HL HOUSE HE E Z 2101? '1I O rn FOOTPRI'.T PIT-1 T -1,076 f F - 21019 74th' IR"ERY _ Ave W F, TP-2 f rt E H- -LL 'E_ r STEP, H F EL= E F D REB 9 .j•:• l r HE 22969 'As �+ — 0.06'S of L 3 p0 _iE 0.12'E FRCA N '18'S2' C, P � o r^ L E E to.. o> WOOD '�. i•;� ...•,� :I FENCE CO^ ASPH ; �o > WALL ' rn ♦ 0.9E OF U`+E I 16" n- F r�- y i k 3 9'S F ROV v SSMH -' 11 R > z PROP CO". RIM-405.54' 34.+ h = H E 8-CONC(N.) f FE E CORN r Base map modified from Topographic & Boundary Survey by Terrane, dated October 14, 2022 Legend: 61 Approx. Test Pit Location PanGEO, Inc., January 2023 Approx. Scale 1"=30' PanGEO Infiltration Test SITE AND EXPLORATION PLAN 21019 74th Avenue West INCORPORATED Edmonds, Washington Project No. 23-017.200 Figure No. 2 APPENDIX A SUMMARY TEST PIT LOGS RELATIVE DENSITY / CONSISTENCY SAND / GRAVEL SILT / CLAY SPT Approx. Relative SPT Approx. Undrained Shear DensityN-values Density (%) Consistency N-values Strength (psf) Very Loose <4 <15 Very Soft <2 <250 Loose 4 to 10 15 - 35 Soft 2 to 4 250 - 500 Med. Dense 10 to 30 35 - 65 Med. Stiff 4 to 8 500.1000 Dense 30 to 50 65 - 85 Stiff 8 to 15 1000 - 2000 Very Dense >50 85.100 Very Stiff 15 to 30 2000 - 4000 Hard >30 >4000 UNIFIED SOIL CLASSIFICATION SYSTEM MAJOR DIVISIONS GROUP DESCRIPTIONS •�' GW: Well -graded GRAVEL Gravel GRAVEL (<5% fines) .. .....: ...................................................... 50% or more of the coarse o ° GP : : Poorly -graded GRAVEL fraction retained on the #4 sieve. Use dual symbols leg. o ° GM ...................................................... Silty GRAVEL GP -GM) for 5% to 12% fines. GRAVEL (>12% fines) •••••••••••••••••••••••••••••• GC : ........................••• Clayey GRAVEL ...................................................................... .......................................................... SW: Well -graded SAND Sand SAND (<5 /° fines) " "'' 50% or more of the coarse ....................................:....> % SP Poorly -graded raded SAND y-g fraction passing the #4 sieve. Use duals leg. SP-SM � ; ":r" ............................................................ SM: Silt SAND y %fin for s%to12%fines.g SAND (>1 2% fines) , ••••••••••••••••••••••••••••••••••••••••••••••••••••••••• SC : Clayey SAND ...................................................................... ............................................................. ML : SILT Liquid Limit < 50 ............................................................ CL : Lean CLAY Silt and Clay ............................................................ OL : Organic SILT or CLAY == — 50%or more passing #200 sieve :.................................. :...................................................... MH : Elastic SILT Liquid Limit > 50 CH Fat CLAY OH Organic SILT or CLAY — , .................................................................. Highly Organic Soils ............................................................ PT : PEAT Notes: 1. Soil exploration to s contain material descriptions based on visual observation and field tests using a system modified from the Uniform Soil Classification System (USCS). Where necessary laboratory tests have been conducted (as noted in the "Other Tests" column), unit descriptions may include a classification. Please refer to the discussions in the report text for a more complete description of the subsurface conditions. 2. The graphic symbols given above are not inclusive of all symbols that may appear on the borehole to s. Other symbols may be used where field observations indicated mixed soil constituents or dual constituent materials. DESCRIPTIONS OF SOIL STRUCTURES Layered: Units of material distinguished by color and/or Fissured: Breaks along defined planes composition from material units above and below Slickensided: Fracture planes that are polished or glossy Laminated: Layers of soil typically 0.05 to 1 mm thick, max.1 cm Blocky: Angular soil lumps that resist breakdown Lens: Layer of soil that pinches out laterally Disrupted: Soil that is broken and mixed Interlayered: Alternating layers of differing soil material Scattered: Less than one per foot Pocket: Erratic, discontinuous deposit of limited extent Numerous: More than one per foot Homogeneous: Soil with uniform color and composition throughout BCN: Angle between bedding plane and a plane normal to core axis COMPONENT DEFINITIONS COMPONENT SIZE / SIEVE RANGE COMPONENT SIZE / SIEVE RANGE Boulder: > 12 inches Sand Cobbles: 3 to 12 inches Coarse Sand: #4 to #10 sieve (4.5 to 2.0 mm) Gravel Medium Sand: #10 to #40 sieve (2.0 to 0.42 mm) Coarse Gravel: 3 to 3/4 inches Fine Sand: #40 to #200 sieve (0.42 to 0.074 mm) Fine Gravel: 3/4 inches to #4 sieve Silt 0.074 to 0.002 mm Clay <0.002 mm TEST SYMBOLS for In Situ and Laboratory Tests listed in "Other Tests" column. ATT AtterbergLimit Test Comp Compaction Tests Con Consolidation DID Dry Density DS Direct Shear %F Fines Content GS Grain Size Perm Permeability PP Pocket Penetrometer R R-value SG Specific Gravity TV Torvane TXC Triaxial Compression UCC Unconfined Compression SYMBOLS Sample/In Situ test types and intervals 2-inch OD Split Spoon, SPT (140-lb. hammer, 30" drop) H3.25-inch OD Spilt Spoon (300-lb hammer, 30" drop) Non-standard penetration test (see boring log for details) Thin wall (Shelby) tube Grab Rock core ® Vane Shear MONITORING WELL SZ Groundwater Level at time of drilling (ATD) 1 Static Groundwater Level Cement / Concrete Seal Bentonite grout / seal Silica sand backfll Slotted tip Slough Bottom of Boring MOISTURE CONTENT Dry Dusty, dry to the touch Moist Damp but no visible water Wet Visible free water GPmE® Terms and Symbols for I IN C 0 R P 0 R A T E D Boring and Test Pit Logs Figure A-1 Phone: 206.262.0370 Test Pit Logs Project No: Project Name: Project Location: Excavated: 23-017.200 Infiltration Test 21019 74th Avenue West, Edmonds, WA 01/25/2023 by Avid Landscape w/ Kubota Small -Track Excavator Test Pit No. PIT-1 Location: 298408, 1272042 (Washington State Plane - North) Approximate ground surface elevation: 405 feet (NAVD88) Depth ft Material Description [Topsoil / Fill] 0 — 2 1/2 Approximately 6 inches of topsoil above: medium dense, orangish-brown, silty SAND, trace gravel and cobble, trace rootlets; occasional trash debris and burnt wood fragments; non -plastic, moist [Vashon Advance Outwash - Qva] 2 1/2 — 8 Dense, gray -brown, poorly -graded SAND with gravel and cobble, trace rootlets and roots; non -plastic, moist .f •s.'3 =�-n�,. 'aye, ' . ,rs �,t '" �, �!` . J . y. "la— t Image of PIT-1 at approximately 5 feet below the existing ground surface (testing depth). After infiltration testing, the pit was overdug to approximately 8 feet below ground surface. No groundwater was encountered at time of explorations. Logged by: S. Scott PmGEOP O R A T E O Ge (t h,ksl B EarMq— Engineering Co ... 1—R Figure A-2 Test Pit Logs Project No: Project Name: Project Location: Excavated: 23-017.200 Infiltration Test 21019 74th Avenue West, Edmonds, WA 01/25/2023 by Avid Landscape w/ Kubota Small -Track Excavator Test Pit No. TP-1 Location: 298422, 1272072 (Washington State Plane - North) Approximate ground surface elevation: 402 feet (NAVD88) Denth ft Material Description [Topsoil / Fill] 0-4 Approximately 24 inches of topsoil and duff above: loose to medium dense, gray -brown, silty SAND, trace gravel and cobble, occasional roots and rootlets, trash debris; non -plastic, moist [Vashon Advance Outwash - Qva] 4-8 Dense, gray -brown to gray, poorly -graded SAND with gravel and cobble, occasional roots and rootlets; non -plastic, moist A. • _ l f'�. �.� •,fit � � .11.1 � f ME �d>`R� Yie-�{+� � -' F��T- i a•' axe _ Image of TP-1 approximately 8 feet below the existing ground surface. No groundwater was encountered at time of exploration. Logged by: S. Scott PmGEE) C O R P O R A T fi D Ga twh,kal & Ea,Mp.aka Enp/ae d q Cons.Ift— Figure A-3 Test Pit Logs Project No: Project Name: Project Location: Excavated: 23-017.200 Infiltration Test 21019 74th Avenue West, Edmonds, WA 01/25/2023 by Avid Landscape w/ Kubota Small -Track Excavator Test Pit No. TP-2 Location: 298393, 1272071 (Washington State Plane - North) Approximate ground surface elevation: 402 feet (NAVD88) Depth ft Material Description [Topsoil / Fill] 0-3 Approximately 12 inches of topsoil above: medium dense, gray -brown, silty SAND, trace gravel and cobble, abundant rootlets; occasional trash debris; non -plastic, moist [Vashon Advance Outwash - Qva] 3-8 Dense, gray -brown, poorly -graded SAND with gravel and cobble, trace rootlets; non -plastic, moist ,i �:�� "ate.'• . �'�', ``y' . P `a. Image of TP-2 approximately 8 feet below the existing ground surface. No groundwater was encountered at time of exploration. Logged by: S. Scott PmGEOP O R A T E O Ge (l h,ksl B EarMq— Engineering Co ... 1—R Figure A-4 Test Pit Logs Project No: Project Name: Project Location: Excavated: 23-017.200 Infiltration Test 21019 74th Avenue West, Edmonds, WA 01/25/2023 by Avid Landscape w/ Kubota Small -Track Excavator Test Pit No. TP-3 Location: 298380, 1272030 (Washington State Plane - North) Approximate ground surface elevation: 405 feet (NAVD88) Depth ft Material Description [Topsoil / Fill] 0-3 Approximately 12 inches of topsoil above: medium dense, gray -brown, silty SAND, trace gravel and cobble, trace rootlets; occasional trash debris; non - plastic, moist [Vashon Advance Outwash - Qva] 3-8 Dense, gray -brown to gray, poorly -graded SAND with gravel and cobble, trace rootlets; non -plastic, moist " AN, - Y 4.r.. ° � i+III; �►. "'� •4'\. _� � "l. �' y, ,LA • �£ l Jr � .1• �� s ice Image of TP-3 approximately 8 feet below the existing ground surface. No groundwater was encountered at time of exploration. Logged by: S. Scott PanGEOO R P O R A T E O Ge (t h,ks1 B E, Mqo Engine g Co...1—R Figure A-5 Avid Landscaping Site Improvements - 22414.20 Drainage Report September 6, 2023 Section VII, Page 1 Section VII — Operation and Maintenance Manual Section VII Summary: Narrative Grading & Drainage Plan (11x17) The Operation and Maintenance Manual is a standalone document that will be given to the owner following the construction of the project. The contractor will be responsible for the maintenance and operation of all stormwater structures and BMPs requiring maintenance during construction and responsibility will pass to the owner after construction. Upon request by the County, it shall be made available for their inspection. It is generally expected that few to none of these defects will be present upon the yearly inspection of each facility. 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Avid Landscaping Site Improvements - 22414.20 Drainage Report September 6, 2023 Section VI I, Page 2 Avid Landscaping Site Improvements 7328 210th St SW & 21019 74th Ave W Edmonds, WA 98026 OPERATION AND MAINTENANCE MANUAL Date: September 2023 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Avid Landscaping Site Improvements - 22414.20 September 6, 2023 Drainage Report Section VII, Page 3 This Operation and Maintenance Manual has been created for the stormwater management system associated with this project. The proposed stormwater structures include conveyance pipes, catch basins, and an infiltration trench. Included in this Operation and Maintenance Manual is an 11" x 17" grading and drainage plan sheet showing the locations of stormwater structures. Please note that this map is generated during the design phase and may not reflect all changes made in permitting and construction. CG Engineering may be contacted for an updated copy of this map once the as -built drawings are completed for the site. The contractor will be responsible for the maintenance and operation of all stormwater structures and BMPs requiring maintenance during construction and responsibility will pass to the owner after construction. Attached at the end of this section are maintenance sheets taken from the 2019 SWMMWW. Maintenance sheets are included for the following facilities: Catch Basins: Concrete structures with steel grates that collect stormwater runoff from the site and act as junctions for storm conveyance pipes. Catch basin Inserts: Storm drain inlet protection designed to prevent coarse sediments from entering the storm system during construction. Infiltration Trench: A underground gravel trench bed designed to infiltration stormwater into the surrounding soils. Most maintenance tasks are generally reactionary to a defect being found, rather than a matter of constant upkeep. It is generally expected that few to none of these defects will be present upon the yearly inspection of each facility. The facility sheets list the potential conditions warranting maintenance and the expected result following any maintenance. Several engineer's notes for specific tasks are provided within the facility sheets. Unless otherwise noted on the facility sheets the maintenance tasks should be performed on an "as needed" basis: (a) When the described defect is visible to whomever performs the yearly inspection, (b) Should any defect become apparent between inspections. 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com CB (TYPE 1)� 1 �Sb RIM=408.81' IE 8"CONC(SE.)=406`.661' ' v I CASE WN 0.9' \ SSMH W W RIM=409.09' \\� 'CONC(N./E./S./W.) =391.64'(C.C.) J to CB (TYPE 1) RIM-409.50' 1 E 8"CONC(NE.)=407.60' / G CB (TYPE 1) RIM=409.48' SS Y SD Sil SW 1 /4, SW 1 /4, SECTION 20, TOWNSHIP 27 NORTH, RANGE 4 EAST, W.M. s IE 36"CONC(N.)=396.16' �IK�K E 36"CONC(E.)=395.95 IE 12"CONC(S.)=UNABLE TO MEASURE � APPROX. LOCATION OF WATER f LINE, PER RECORDS V W-W-W 1) SITE TBM SET PK NAIL W/ RED WASHER ELEV=405.74' / /-------SSM,H \ \ ` RIM=TD4J1' iy IE 8"PVC(N.)F391.30' A -SD-SD-SD-SD-SD-SD-SD- (LItIt IE 8"CON C(E./`W.)-391.3Q'(C. C.) 2 \ SS -SS -SS -SS SS -SS -SS- 404.95 SS -SS \ SS \ 404.45 CURB\\ \ -404 .a < < RAMP \ \ ,pa. P PAP �IP P P P-E)-P-P-P G-G-IGI-G� - 404.58 10" EVG 4II Q4 W', 36" EVG IE 8 CONC(E./SW.)=407.23 I 1 406.98 P I - 40723 17 gg 1 I I\ ! INSTALL 3'x2'xb"ROCK SPLASf�PAq \ 40696 407.25 40Y.\8 ROCK p \ / / ) I STEPS lF7. EfyTRV:4�0 EXIST SIDE SEWER PER EDMON DES / I GIS AS -BUILT DRAWINGS LANDSLIDE/STEEP CB (TYPE 2' I I � \ \\I / // SLOPE HAZARD AREA RIM=408.32' c; 407.28 CON, I� II / / �I I IE 8"GONG W. =405.62' O ASPH . I SS LF^6"PVC@1.6% ( ) 1.5% USE Y:407.0 LAND\ G / IE 12"CONC(N.)=405.42' I m �r vi `' HOUSE NO. 7328 / FOOTPRINT=1,230 fS.F. / I IANDSCAPE STRIP. 12" YARD DRAIN f m _ TIE EXISTROOFAREA f RIM: 407.50 ONSITE DOWNSPOUTS TO IE (6" 405.50 I q --) I m TOW: 406.0 CURB RAMP ° ' YARD DRAIN IE (6" N): 405.50 1 �I- 1 / 1 I I Z e � 13 I1_ ..,BOW: 409.E ______________- I TOW:406.2 1 ENTRY: 406.7I D 1 1 BOW: 404.5 407.90 1 I I I I- I I m z aW' 1 \ \ 406.63 I I OR.1 I J "1a; °a I I0 1 1 G-G-� 'C D I I v?� HA D13AIL NP ,a� _ o/ I TOW: 405.8 Vim-, I a "CO E I' BOW: 403.9 I O IA I F 13 t0 BLOCK 1 u.1.1 WALL WW<RhOEY.06TPR1Nt-48Q I29 LF 6 1 4 m 1 1 D f tS.F. < PVC@7.3%116.43. I 406.45 ENTRY: 408.95 > .I .1., ..I 1 O ' 1 Z J �101 D N 405:71p j BLOCK 6 \ A. w i. LOCATION OF GAS LINE, PER I I 40867 ENTRY: 408.95 WALL 1 "VL 1 1 PSE MAP NO. Q163070 i O 408.511 I' 1 I V --- / Z�7 408.4s 408.45 I \ \ \ I \ EA 408.53 4 �< b ll / I 53 LF ^' 6" PVC @ 0.9%(OVERFLOW PIPE) \ \ X/ ROW 408.34 CONIC I i 401s2 =AT=H LINE C3.2 lowMATCH LINE C3.1 I Imo' i / �\ 1 jlJ,o%- E- P-D�RNT EASEMENT TO SOUTH PROPERTY, TO BE - 4 I.� I RECORRIFA PRIOR TO PERMIT FINAL APPROVAL ;..EVG.; // / I O.� .G'R VL £ 24 89,418'25" E 60.03' ENLARGED GRADING AND UTILITY PLAN 6 VG 1 SCAIF V - 10' 10 0 5 10 20 CO\ISDI-65 ^ SO_ SD-SD-SDG�-SD-SO W)E+-W W-W-W W-W�-W 210TH ST SW \ N 89'17'31" $ � CURB RAMP TOC 406.50 RELOCATE EXIT F/ ROC: 406.0 WM IN PLANTER 66 -�-- ---- ---- STRIP. REPLACE 1" SS I SS SS- POLY SERVICE LINESS SS / LANDSCAPE STRIP AS NEED D / �U I 5D ( 1 407.44 - 1 P. e--r I - I 1 II I 1 I I I 1 Y 43LF-6" VC@5.1% 407.47\ �\ �- 407.5151 \- i 784 GRADING AND DRAINAGE PLAN NOTES: 1. SOILS REPORT REPORT NUMBER: 23-017.200 PREPARED BY: PANGEO, INC DATED: FEBRUARY 24, 2023 2. ALL DISTURBED AREAS ON AND OFF -SITE SHALL BE COMPOST -AMENDED PER THE REQUIREMENTS OF BMP T5.131N THE STORMWATER MANUAL VOLUME V, CHAPTER 11. 4. A MINIMUM OF T HORIZONTAL SEPARATION AND V VERTICAL SEPARATION IS REQUIRED BETWEEN DRY UTILITIES (POWER, GAS, PHONE, CABLE, ETC) AND SEWER, WATER AND STORM, AND A MINIMUM OF 5' HORIZONTAL SEPARATION AND V VERTICAL SEPARATION FROM ANY CITY -OWNED LINES. 5. A TYPE II CATCH BASIN IS REQUIRED WHENEVER RIM TO INVERT EXCEEDS 5'. 6. A MINIMUM OF T OF COVER IS REQUIRED FOR ALL PIPES LOCATED UNDER DRIVEABLE SURFACES AND 1' OF COVER UNDER LANDSCAPE SURFACES. 7. ADA PARKING STALLS SHALL BE NO MORE THAN 2% MAX IN ALL DIRECTIONS. 9. NEW/REPLACED IMPERVIOUS SURFACE (INCLUDING ROW): 5,730 SF -- NEW GRAVEL PARKING:3,756 SF. RUNOFF ROUTED TO INFILTRATION TRENCH THROUGH CATCH BASINS AND CONVEYANCE PIPES. -- NEWCONCRETESIDEWALK: 771 SF. RUNOFF ROUTED TO INFILTRATION TRENCH THOUGH CATCH BASINS AND CONVEYANCE PIPES. -- NEW/REPLACED ROW CONCRETE SIDEWALK:1,203 SF. RUNOFF FLOWS TO EXISTING STORM SYSTEM IN ROW. INFILTRATION TRENCH DESIGNED TO INCLUDE THIS AREA. -- REPLACED ROW ASPHALT/UTILITY SAWCUTS: 134 SF. RUNOFF FLOWS TO EXISTING STORM SYSTEM ON ROW. INFILTRATION TRENCH DESIGNED TO INCLUDE THIS AREA. GRADING QUANTITIES TOTAL EXCAVATION (CUT) - 30 CU YDS TOTAL EMBANKMENT(FILL)- 35 CU YDS TOTAL 65 CU YDS THE QUANTITIES SHOWN ABOVE ARE FOR THE PERMIT PROCESS ONLY. THESE VALUES ARE APPROXIMATE. DO NOT USE FOR BIDDING, PAYMENT, OR ESTIMATING PURPOSES. PAVING LEGEND NEW ASPHALT/UTILITYSAWCUT OVERLAY EXISTING ASPHALT NEW CONCRETE GRAVELSURFACE CATCH BASIN SCHEDULE MARK TYPE RIM ELEV INV ELEV NOTES O 12" YARD DRAIN 407.20 IE (6" E): 405.20 - O TYPE 405.0 IE(6'S): 403.0 IE(6' W): 402.90 2 3 5 C3. C3. C3.3 O 12" YARD DRAIN 407.50 IE (6' E): 405.50 E(6'N): 40550 _ ® TYPE 1 406.40 IE (6" W): 403.40 IE (6' S): 402.50 IE (6' N): 402.60 2 3 5 C3.3 C3. C3.3 55 CONTECH CDS-4-C W/ GRATED INLET 405.10 IE (6' E): 401.54 IE (6' N) 40154 IE (6' W): 401.54 1 C3.4 © TYPE I 405.10 IE (6' W): 401.90 2 3 5 C3.3 C3. C3.3 PROJECTS WILL BE CONSTRUCTED WITHOUT PHASING AND ARE TREATED AS ONE FOR STORMWATER THRESHOLDS 7328 210TH ST SW: BLD 2022-0670 21019 74TH AVE W: (BLD2023-0312) APPROVED FOR CONSTRUCTION CITY OF EDMONDS DATE: BY: CITY ENGINEERING DIVISION O 6 6VGINEERING 250 4TH AVE. S.. SUITE 200 EDMONDS, WASHINGTON 98020 PHONE (425) 778-8500 FAX (425) 778-5536 ,el, Gwl' 09106123 In Q O 0 C W 0 7 w a ^ t w r r W w s O 0 a C V UI 0 DESIGN: BJL DRAWN: ATD CHECK: JPU JOB NO: 22414.20 DATE: 03/10/23 10 W I- Q z W H W > Q c rn Z D_ o a N 0 Id W Z v) Z FL N 0)o (N Q Q Q v, Ld z vi o < N Z f DO O Q J_ >rnp Z� Q Il- W Ld 7 SHFFT C3.1 MATCH LINE C3.2 MATCH LINE C3.1 �c c IG ENLARGED GRADIN SCALE 1"=10' KUW 408.34 - i408.32 - / 1 / I i / ( IFa / B / II �d�l SW 1 /4, SW 1 /4, SECTION 20, TOWNSHIP 27 NORTHIII I, r, RANGE 4 EAST, W.M. s �� \\\ 2 7 I _ Q:\ /WIDE PROPOSED C� EASEyd1ENT TO SOUTH PROPERTY, T08E I RECORDRO PRIOR TO PERMIT FINAL APPROVAL I f RELOCATE EXIST Z IN PLANTER STRIP; USE FOR IRRIGATION W/ DCVA ON PRII ATE PROPEj O 0 I (ADo > f a N I O rn� I 1 O D " ASP �30.01, >Z U) In \I / T c P N 8 18'52ssz" T 4o 405.90 ASPH SSMH RIM=405.54' IS 8"CONC(N.) =396.39'(C.C.) v Pi AKI ` 4" (MIN) b OBSERVATION WELL NOTE: PER NOTE 1 OBSERVATION WELL SHALL CONFORM TO WSDOT SPEC. METAL FRAME AND rDOUBLE LAYER OF 12" 9-0512(6), PERFORATED PVC GRATE MARKED "DRAIN" 1 / OVERLAY FILTER FABRIC UNDERDRAIN PIPE ml TYPICAL 10' WIDE INFILTRATION TRENCH 2 SCALE: NTS Ir __ _ _ ///CURB' Lam-- 1 --- N 89118'25" E 60y� I I \ ..6_ VCV (6) 6" DEC 406.40 / -- -.:✓. a;'I.:.''_;'.: ... ... —' ..� J' 405.60 I / I / 405.91 r ',,.,. ... i. \ :..—:. SHE 30," EVG OBSERVATION PORT, TYP '' POST -CONSTRUCTION SOIL I I I i/ j\ I QUALITY AND DEPTH I /T'•''•: 52'x 10'x 3'INFILTRATIO4TRENCH, d /� ° Wa .. ....\ -.'...1'.'. ., .. IF(6 PDREPVC):, ...I EO(T" PERE 01.50 B 400.0 �/ I FIR / ... .. .. � VE :. '�' _ �'.. ..... .. .. /•,• .:: ....I.::.: ,........ ,•� �. .�.� 53�LF^.6"RIP@0.8%.'�� I II / 25 ^'6"PVC@0:W' 405.3S $ \\ 'I, II-- ° a • .-�.:. '." /I SHED / \ 381 EVG I .. .:. :.� 404.40 405.20 n :..'': "...: ... /-405.97 \/ 405.40 18,��/VG 40 .ss J' \ 16 16 �4.y:/ 12" ENV a \ /tv , CURB II FINISHED GRADE CONTECH CDS-4-C W/ (GRAVELSURFACE) ` GRATED INLET PER PLAN WRAP GRAVEL ENTIRELY WITH AND OVERLAP FILTER FABRIC SECTIONS WASHED ROCK 11/2" - 3/4" 6" OVERFLOW PIPE PER PLAN PAVING LEGEND NEW ASPHALT/UTILITY SAWCUT OVERLAY EXISTING ASPHALT NEW CONCRETE GRAVEL SURFACE C CMI ENGINEERING 250 4TH AVE. S.. SUITE 200 EDMONDS, WASHINGTON 98020 PHONE (425) 778-8500 FAX (425) 778-5536 ¢ ,n Q � O m w 0 7 w H a ,n m w � F- F- w w m O C a C V W 0 09106123 WALL DESIGN: BJL DRAWN: ATD CHECK: JPU JOB NO: 22414.20 \ - - - - - - DATE: 03/10/23 CATCH BASIN SCHEDULE MARK TYPE RIM ELEV INV ELEV NOTES O$ CONTECH CDS-4-C W/ 405.10 IE IS' E): 401.54 IE (6" N): 401.54 1 C3 GRATED INLET IE IS" W): 401.54 © TYPE I 405.10 IE IS" W): 401.90 2 3 5 C3. C3.3 C3.3 T �J PROJECTS WILL BE CONSTRUCTED WITHOUT PHASING AND ARE TREATED AS ONE FOR STORMWATER THRESHOLDS 7328 210TH ST SW: BLD 2022-0670 21019 74TH AVE W: (BLD2023-0312) APPROVED FOR CONSTRUCTION CITY OF EDMONDS DATE: BY: CITY ENGINEERING DIVISION :0 w I— Q z La = W � > c rn Z D_ a N o t I Z N N N 00 � Z rn a (N Q Q Q 0 0- vim)=�3-- o � Ld z vi CD < N Z � DO O J J >rnp Z� Q f\ La Ld 7 SHFFT C3.2 Appendix V-A: BMP Maintenance Tables Ecology intends the facility -specific maintenance standards contained in this section to be conditions for determining if maintenance actions are required as identified through inspection. Recognizing that Permittees have limited main- tenance funds and time, Ecology does not require that a Permittee perform all these maintenance activities on all their stormwater BMPs. We leave the determination of importance of each maintenance activity and its priority within the stormwater program to the Permittee. We do expect, however, that sufficient maintenance will occur to ensure that the BMPs continue to operate as designed to protect ground and surface waters. Ecology doesn't intend that these measures identify the facility's required condition at all times between inspections. In other words, exceedance of these conditions at any time between inspections and/or maintenance does not auto- matically constitute a violation of these standards. However, based upon inspection observations, the Permittee shall adjust inspection and maintenance schedules to minimize the length of time that a facility is in a condition that requires a maintenance action. Table V-A.1: Maintenance Standards - Detention Ponds Maintenance Com- Defect Conditions When Maintenance Is Needed Results Expected When Maintenance Is Performed ponent Any trash and debris which exceed 1 cubic feet per 1,000 square feet. In general, there should be no visual evidence of dumping. Trash &Debris Trash and debris cleared from site If less than threshold all trash and debris will be removed as part of next scheduled main- tenance. Any poisonous or nuisance vegetation which may constitute a hazard to maintenance per- No danger of poisonous vegetation where maintenance personnel or the public might normally be. (Coordin- Poisonous Veget- sonnel or the public. ate with local health department) ation and noxious weeds An evidence of noxious weeds as defined b State or local reulations. y y g Complete eradication of noxious weeds may not be possible. Compliance with State or local eradication (Apply requirements of adopted IPM policies forthe use of herbicides). policies required Contaminants and Any evidence of oil, gasoline, contaminants or other pollutants Pollution (Coordinate removallcleanuptyith local water quality response agency). No contaminants or pollutants present. General Rodent Holes Any evidence of rodent holes if facility is acting as a dam or berm, or any evidence of water Rodents destroyed and dam or berm repaired. (Coordinate with local health department; coordinate with piping through dam or berm via rodent holes. Ecology Dam Safety Office if pond exceeds 10 acre-feet.) Facility is returned to design function. Beaver Dams Dam results in change or function of the facility. (Coordinate trapping of beavers and removal of dams with appropriate permitting agencies) Insects destroyed or removed from site. Insects When insects such as wasps and hornets interfere with maintenance activities. Apply insecticides in compliance with adopted IPM policies Tree growth does not allow maintenance and inspection access or interferes with main- tenance activity (i.e., slope mowing, silt removal, vactoring, or equipment movements). If Trees do not hinder maintenance activities. Harvested trees should be recycled into mulch or other bene- Tree Growth and trees are not interfering with access or maintenance, do not remove ficial uses (e. g., alders for firewood). Hazard Trees If dead, diseased, or dying trees are identified Remove hazard Trees (Use a certified Arborist to determine health of tree or removal requirements) Eroded damage over inches deep where cause of damage is still present or where there is Slopes should be stabilized using appropriate erosion control measure(s); e.g., rock reinforcement, planting Side Slopes of Pond Erosion potential for continued erosion. of grass, compaction. Any erosion observed on a compacted berth embankment. If erosion is occurring on compacted berms a licensed engineer in the state of Washington should be con- sulted to resolve source of erosion. Storage Area Sediment Accumulated sediment that exceeds 10% of the designed pond depth unless otherwise spe- Sediment cleaned out to designed pond shape and depth; pond reseeded if necessary to control erosion. cified or affects inletting oroutletting condition of the facility. 2019 Stormwater Management Manual for Western Washington Volume V - Appendix A - Page 1005 Table V-A.1: Maintenance Standards - Detention Ponds (continued) Maintenance Com- Defect Conditions When Maintenance Is Needed Results Expected When Maintenance Is Performed ponent Liner (if Applic- able) Liner is visible and has more than three 1/4-inch holes in it. Liner repaired or replaced. Liner is fully covered. Any part of berm which has settled 4 inches lower than the design elevation If settlement is apparent, measure berm to determine amount of settlement Settlements Settling can be an indication of more severe problems with the berm or outlet works. A Dike is built back to the design elevation. licensed engineer in the state of Washington should be consulted to determine the source of Ponds Berms (Dikes) the settlement. Discernable waterflow through pond berm. Ongoing erosion with potential for erosion to con- tinue. Piping Piping eliminated. Erosion potential resolved. (Recommend a Gcethechnical engineer be called in to inspect and evaluate condition and recommend repair of condition. Tree growth on emergency spillways creates blockage problems and may cause failure of the bens due to uncontrolled overtopping. Trees should be removed. If root system is small (base less than 4 inches) the root system may be left in Tree Growth place. Otherwise the roots should be removed and the berm restored. A licensed engineer in the state of Emergency Overflow/ Tree growth on berms over 4 feet in height may lead to piping through the berm which could Washington should be consulted for proper berm/spillway restoration. Spillway Berms lead to failure of the berm. and over 4 feet in height Discernable waterflow through pond berm. Ongoing erosion with potential for erosion to con- tinue. Piping Piping eliminated. Erosion potential resolved. (Recommend a Geotechnical engineer be called in to inspect and evaluate condition and recommend repair of condition. Only one layer of rock exists above native soil in area five square feet or larger, or any expos - Emergency Over- Emergency Over- ure of native soil at the top of out flow path of spillway. Rocks and pad depth are restored to design standards. flow/Spillway flow/Spillway (Rip -rap on inside slopes need not be replaced.) Erosion See "Side Slopes of Pond" Table V-A.2: Maintenance Standards - Infiltration Maintenance Component Defect Conditions When Maintenance Is Needed Results Expected When Maintenance Is Per- formed See Table V-A.1: Maintenance Standards - Deten- Trash & Debris See Table V-A.1: Maintenance Standards - Detention Ponds tion Ponds Poisonous/Noxious See Table V-A.1: Maintenance Standards - Deten- See Table V-A. Maintenance Standards - Detention Ponds General Vegetation tion Ponds Contaminants and Pol- See Table V-A.1: Maintenance Standards - Deten- See Table V-A. Maintenance Standards - Detention Ponds lution tion Ponds See Table V-A.1: Maintenance Standards - Deten- Rodent Holes See Table V-A.1: Maintenance Standards - Detention Ponds tion Ponds Water ponding in infiltration pond after rainfall ceases and appropriate time allowed for infiltration. Treatment basins should infiltrate Sediment is removed and/or facility is cleaned so Storage Area Sediment Water Quality Design Storm Volume within 48 hours, and empty within 24 hours after cessation of most rain events. that infiltration system works according to design. 2019 Stormwater Management Manual for Western Washington Volume V - Appendix A - Page 1006 Table V-A.2: Maintenance Standards - Infiltration (continued) Maintenance Component Defect Conditions When Maintenance Is Needed Results Expected When Maintenance Is Per- formed (A percolation test pit or test of facility indicates facility is only working at 90 % of its designed capabilities. Test every 2 to 5 years. If two inches or more sediment is present, remove). Filled with Sediment and Filter Bags if a licable 9( applicable) Debris Sediment and debris fill bagmore than 112 full. Filter bag is replaced ors stem is redesigned. 9y 9 Rock Filters Sediment and Debris By visual inspection, little or no water flows through filter during heavy rain storms. Gravel in rock filter is replaced. Side Slopes of Pond Erosion See Table V-A.1: Maintenance Standards - Detention Ponds See Table V-A.1: Maintenance Standards - Deten- tion Ponds Tree Growth See Table V-A.1: Maintenance Standards - Detention Ponds See Table V-A.1: Maintenance Standards - Deten- Emergency Overflow Spillway tion Ponds and Berms over feet in height. See Table V-A. Maintenance Standards - Deten- Piping See Table V-A.1: Maintenance Standards -Detention Ponds tion Ponds Rock Missing See Table V-A.1: Maintenance Standards - Detention Ponds See Table V-A.1: Maintenance Standards - Deten- Emergency Overflow Spillway tion Ponds Erosion See Table V-A.1: Maintenance Standards - Detention Ponds See Table V-A.1: Maintenance Standards - Deten- tion Ponds Facility or sump filled Pre -settling Ponds and Vaults with Sediment and/or 6" or designed sediment trap depth of sediment. Sediment is removed. debris Table V-A.3: Maintenance Standards - Closed Detention Systems (TanksiVaults) Maintenance Defect Conditions When Maintenance is Needed Results Expected aintenance is Per - Component formed Plugged Air Vents One-half of the cross section of a vent is blocked at any point orthe vent is damaged. Vents open and functioning. Accumulated sediment depth exceeds 10% of the diameter of the storage area for 1/2 length of stora or any point Debris and Sediment deds 15 % ep of diameter. All sediment and debris removed from storage (Example: 72-inch s nk would require cleaning when sediment re epth of 7 inches for more than 1/2 length of area. Storage Area tank.) Any openings or voids allowing material to be nto facility. Joints Between Tank/Pipe Section All joint between tank/pipe sections are sealed. (Will require engineering anal etermine structural stability). Tank Pipe Bent Out of Shape Any part of to ' is bent out of shape more than 10% of its design shape. (Review ' d by engineer to determine Tank/pipe repaired or replaced to design. st stability). Cracks wider than 1/2-inch and any evidence of soil particles entering the structure through the cracks, or main- Vault replaced or repaired to design spe- Structure I ll' Structure Includes Cra all, Bottom, tenance/inspection personnel determines that the vault is not structurally sound. ci and is structurally sound. Damage to r op Slab Cracks widerthan 1/2-inch at the joint of any inlet/outlet pipe or any evidence of soil particles entering the vault through the No cracks more t ch wide at thejoint of walls. the inlet/outlet pipe. 2019 Stormwater Management Manual for Western Washington Volume V - Appendix A - Page 1007 Table V-A.S: Maintenance Standards - Catch Basins Maintenance Defect Conditions When Maintenance is Needed Results Expected When Maintenance is per - Component formed Trash or debris which is located immediately in front of the catch basin opening or is blocking inletting capacity of the basin by more than 10 %. No Trash or debris located immediately in front of Trash or debris (in the basin) that exceeds 60 percent of the sump depth as measured from the bottom of basin to invert of the lowest pipe into or out of the catch basin or on grate opening. basin, but in no case less than a minimum of six inches clearance from the debris surface to the invert of the lowest pipe. No trash or debris in the catch basin. Trash & Debris Trash or debris in an inlet or outlet i blocking more than 1/3 of its height. Y pipe 9 9 Inlet and outlet pipes free of trash or debris. Dead animals or vegetation that could generate odors that could cause complaints or dangerous gases (e.g., methane). No dead animals or vegetation present within the catch basin. Sediment (in the basin) that exceeds 60 percent of the sump depth as measured from the bottom of basin to invert of the lowest pipe into or out of the Sediment basin, but in no case less than a minimum of 6 inches clearance from the sediment surface to the invert of the lowest pipe. No sediment in the catch basin General Structure Damage to To slab has holes larger than 2 square inches or cracks wider than 1/4 inch. Intent is to make sure no material is tannin into basin P r9 q ( 9 )� Top slab is free of holes and cracks. Frame and/or Top Slab Frame not sitting flush on top slab, i.e., separation of more than 314 inch of the frame from the top slab. Frame not securely attached Frame is sitting flush on the riser rings or top slab and firmly attached. Fractures or Cracks in Maintenance person judges that structure is unsound. Basin replaced or repaired to design standards. Basin Walls/ Bottom Grout fillet has separated orcracked widerthan 1/2 inch and longerthan 1 foot at thejoint of any inlet/outlet pipe or any evidence of soil particles entering Pipe is regrouted and secure at basin wall. catch basin through cracks. Settlement/ Mis- alignment If failure of basin has created a safety, function, or design problem. Basin replaced or repaired to design standards. Vegetation growing across and blocking more than 10% of the basin opening. No vegetation blocking opening to basin. Vegetation Vegetation growing in inlet/outlet pipe joints that is more than six inches tall and less than six inches apart. No vegetation or root growth present. Contamination and Pol- lution See Table V-A.1: Maintenance Standards - Detention Ponds No pollution present. Cover Not in Place Cover is missing oronly partially in place. Any open catch basin requires maintenance. Cover/grate is in place, meets design standards, and is secured Catch Basin Locking Mechanism Not Working Mechanism cannot be opened by one maintenance person with proper tools. Bolts into frame have less than 1/2 inch of thread. Mechanism opens with proper tools. Cover Cover Difficult to One maintenance person cannot remove lid after applying normal lifting pressure. Cover can be removed by one maintenance per - Remove (Intent is keep coverfrom sealing off access to maintenance.) son. Ladder Ladder Rungs Unsafe Ladder is unsafe due to missing rungs, not securely attached to basin wall, misalignment, rust, cracks, or sharp edges. Ladder meets design standards and allows main- tenance person safe access. Grate opening Unsafe Grate with opening wider than 7/8 inch. Grate opening meets design standards. Metal Grates Trash and Debris Trash and debris that is blocking more than 20% of grate surface inletting capacity. Grate free of trash and debris. (If Applicable) Grate is in place, meets the design standards, and Damaged or Missing. Grate missing or broken member(s) of the grate. is installed and aligned with the flow path. 2019 Stormwater Management Manual for Western Washington Volume V - Appendix A - Page 1009 Table V-A.17: Maintenance Standards - Coalescing Plate Oil/Water Separators Mai ce Component Defect Condition When Maintenance is Needed Results Expected When Maintenance is Perfo Monitoring Inspection of discharge waterfor obvious signs of poor water quality. Effluent discharge from vault should be clear ' o thick visible sheen. Sediment Accumulation Sediment depth in bottom of vault exceeds 6-inches in depth and/or visible signs of sediment on No sediment deposits on vau m and plate media, which would impede flow plates. through the vaulgpd4edrice separation efficiency. Trash and Debris Accumulation d debris accumulated in vault, or pipe inlet/outlet, floatables and non-floatables. Tra ebris removed from vault, and inlet/outlet piping. Oil Accumulation Oil accumulation that a 1-inch at the watersurface. Oil is extracted from vault using vectoring methods. Coalescing plates are cleaned by thoroughly rinsing and flushing. Should be no visible oil depth on water. Damaged Coalescing Plates Plate media broken, deformed, cracked and/or s failure. A portion of the media pack or the entire plate pack is replaced depending on sever- ity of failure. General Damaged Pipes Inlet oroutlet piping damaged or bro in need of repair. Pipe repaired and or replaced. Baffles Baffles corroding, c warping and/or showing signs of failure as determined by Baffles repaired or replaced to specifications. tenance/i on person. racks widerthan 1/2-inch or evidence of soil particles entering the structure through the cracks, Vault replac a airs made so that vault meets design specifications and is Vault Structure Damage - Includes Crac or maintenance/inspection personnel determine that the vault is not structurally sound. structurally sound. Walls, Bottom, Damage to F /or Top Slab Cracks wider than 1/2-inch at the joint of any inlet/outlet pipe or evidence of soil particles enter- Vault repaired so that no cracks ems than 1/4-inch at the joint of the ing through the cracks. inlet/outlet pipe. Access Ladder Damaged Ladder is corroded or deteriorated, not functioning property, not securely attached to structure Ladder replaced or repaired and meets specifications, and is s seas determ- wall, missing rungs, cracks, and misaligned. ined by inspection personnel. Table V-A.18: Maintenance Standards - Catch Basin Inserts Maintenance Component Defect Conditions When Maintenance is Needed Results Expected When Maintenance is Performed Sediment Accumulation When sediment forms a cap over the insert media of the insert and/or unit. No sediment cap on the insert media and its unit. Trash and Debris Accumulation Trash and debris accumulates on insert unit creating a blockage/restriction. Trash and debris removed from insert unit. Runoff freely flows into catch basin. Media Insert Not Removing Oil Effluent waterfrom media insert has a visible sheen. Effluent waterfrom media insert is free of oils and has no visible sheen. General Media Insert Water Saturated Catch basin insert is saturated with water and no longer has the capacity to absorb. Remove and replace media insert Media Insert -Oil Saturated Media oil saturated due to petroleum spill that drains into catch basin. Remove and replace media insert. Media Insert Use Beyond Product Life Media has been used beyond the typical average life of media insert product. Remove and replace media at regular intervals, depending on insert product. Table V-A.19: Maintenance Standards - Media Filter Drain (MFD) Maintenance Component Defect Conditions When Maintenance is Needed Results Ex aintenance is Performed Sediment Remove sediment deposits on grass treatment area of the embankment. When finished, embank - accumulation Sediment depth exceeds 2 inches or creates uneven gradin th sheet flow -ineat should be level from side to side and drain freely toward the toe of the embankment slope. General on grass filter There shou nding wateronce inflow has ceased. strip strip No-ve ow spreader is uneven or clogged so that flows are not uniformly distributed over entire embankment width. Level the spreader and clean to spread flows evenly over entire em an 2019 Stormwater Management Manual for Western Washington Volume V - Appendix A - Page 1017 n cause air pollution include grain dust, sawdust, coal, gravel, crushed rock, cement, and boiler as Nir emissions can contaminate stormwater. The objective of this BMP is to reduce the stor - water ollutants caused by dust generation and control. Pollutant ontrol Approach: Prevent dust generation and emissions where feasible, gulp clean-up dus at can contaminate stormwater, and convey dust contaminated stor ater to proper treatme Applicable B . Clean, as needed, Xwder material handling equipment and . Regularly sweep dust a umulation areas that can contamin stormwater. Conduct sweep- ing using vacuum filter eq ment to minimize/tormwater. n and to ensure optimal dust removal. . Use dust filtration/collection syste s such as , cyclone separators, etc. to con- trol vented dust emissions that coul ontamiControl of zinc dusts in rubber production is one example. . Maintain on -site controls to prevent vehic^ck-out. . Maintain dust collection devices on a r.6aular Recommended BMPs: . In manufacturing/operationtrain employees to handle p ders carefully to prevent gen- eration of dust. . Usewaterspray accumulations to sanitary sewers ere allowed by the local sewer authority propriate treatment system. Use approve dust suppressants such as those listed in Methods for Du Control (Ecology, 2016b . A li-ation of some products may not be appropriate in close proxi it to receiving waters conveyances close to receiving waters. For more information check ith Ecology or the I al jurisdiction. ► hmended Treatment BMPs tall sedimentation basins, wet ponds, wet vaults, catch basin filters, vegetated filter strips, or valent sediment removal BMPs. S411 BMPs for Landscaping and Lawn / Vegetation Management Description of Pollutant Sources: Landscaping can include grading, soil transfer, vegetation planting, and vegetation removal. Examples include weed control on golf course lawns, access roads, and utility corridors and during landscaping; and residential lawn/plant care. Proper man- agement of vegetation can minimize excess nutrients and pesticides. 2019 Stormwater Management Manual for Western Washington Volume IV - Chapter 4 - Page 523 Pollutant Control Approach: Maintain appropriate vegetation to control erosion and the dis- charge of stormwater pollutants. Prevent debris contamination of stormwater. Where practicable, grow plant species appropriate for the site, or adjust the soil properties of the site to grow desired plant species. Applicable BMPs: • Install engineered soil/landscape systems to improve the infiltration and regulation of storm - water in landscaped areas. • Select the right plants for the planting location based on proposed use, available main- tenance,soil conditions, sun exposure, water availability, height, sight factors, and space avail- able. • Ensure that plants selected for planting are not on the noxious weed list. For example, but- terfly bush often gets planted as an ornamental but is actually on the noxious weed list. The Washington State Noxious Weed List can be found at the following webpage: https://www.nwcb.wa.gov/printable-noxious-weed-list • Do not dispose of collected vegetation into waterways or storm sewer systems. . Do not blow vegetation or other debris into the drainage system. • Dispose of collected vegetation such as grass clippings, leaves, sticks by composting or recyc- ling. • Remove, bag, and dispose of class A & B noxious weeds in the garbage immediately. • Do not compost noxious weeds as it may lead to spreading through seed or fragment if the composting process is not hot enough. . Use manual and/or mechanical methods of vegetation removal (pincer -type weeding tools, flame weeders, or hot water weeders as appropriate) rather than applying herbicides, where practical. • Use at least an eight -inch "topsoil' layer with at least 8 percent organic matter to provide a suf- ficient vegetation -growing medium. o Organic matter is the least water-soluble form of nutrients that can be added to the soil. Composted organic matter generally releases only between 2 and 10 percent of its total nitrogen annually, and this release corresponds closely to the plant growth cycle. Return natural plant debris and mulch to the soil, to continue recycling nutrients indef- initely. . Select the appropriate turfgrass mixture for the climate and soil type. Certain tall fescues and rye grasses resist insect attack because the symbiotic endo- phytic fungi found naturally in their tissues repel or kill common leaf and stem -eating lawn insects. 2019 Stormwater Management Manual for Western Washington Volume IV - Chapter 4 - Page 524 ■ The fungus causes no known adverse effects to the host plant or to humans. ■ Tall fescues and rye grasses do not repel root -feeding lawn pests such as Crane Fly larvae. ■ Tall fescues and rye grasses are toxic to ruminants such as cattle and sheep Endophytic grasses are commercially available; use them in areas such as parks or golf courses where grazing does not occur. Local agricultural or gardening resources such as Washington State University Exten- sion office can offer advice on which types of grass are best suited to the area and soil type. • Use the following seeding and planting BMPs, or equivalent BMPs, to obtain information on grass mixtures, temporary and permanent seeding procedures, maintenance of a recently planted area, and fertilizer application rates: BMP C120: Temporary and Permanent Seeding, BMP C121: Mulching, BMP C123: Plastic Covering, and BMP C124: Sodding. . Adjusting the soil properties of the subject site can assist in selection of desired plant species. Consult a soil restoration specialist for site -specific conditions. Recommended Additional BMPs: • Conduct mulch -mowing whenever practicable. • Use native plants in landscaping. Native plants do not require extensive fertilizer or pesticide applications. Native plants may also require less watering. • Use mulch or other erosion control measures on soils exposed for more than one week during the dry season (May 1 to September 30) or two days during the rainy season (October 1 to April 30). . Till a topsoil mix or composted organic material into the soil to create a well -mixed transition layer that encourages deeper root systems and drought -resistant plants. . Apply an annual topdressing application of 3/8" compost. Amending existing landscapes and turf systems by increasing the percent organic matter and depth of topsoil can: Substantially improve the permeability of the soil. Increase the disease and drought resistance of the vegetation. Reduces the demand for fertilizers and pesticides. • Disinfect gardening tools after pruning diseased plants to prevent the spread of disease. • Prune trees and shrubs in a manner appropriate for each species. . If specific plants have a high mortality rate, assess the cause and replace with another more appropriate species. • When working around and below mature trees, follow the most current American National Standards Institute (ANSI) ANSI A300 standards (see 2019 Stormwater Management Manual for Western Washington Volume IV - Chapter 4 - Page 525 http://www.tcia.org/TCIA/BUSINESS/ANSI A300 Standards /TCIA/BUSINESS/A300 Standards/A300 Standards. aspx?hkey=202ff566-4364-4686-b7c1-2a365af59669) and International Society of Arboriculture BMPs to the extent practicable (e.g., take care to min- imize any damage to tree roots and avoid compaction of soil). . Monitor tree support systems (stakes, guys, etc.). Repair and adjust as needed to provide support and prevent tree damage. Remove tree supports after one growing season or maximum of 1 year. Backfill stake holes after removal. • When continued, regular pruning (more than one time during the growing season) is required to maintain visual sight lines for safety or clearance along a walk or drive, consider relocating the plant to a more appropriate location. . Make reasonable attempts to remove and dispose of class C noxious weeds. • Re -seed bare turf areas until the vegetation fully covers the ground surface. . Watch for and respond to new occurrences of especially aggressive weeds such as Him- alayan blackberry, Japanese knotweed, morning glory, English ivy, and reed canary grass to avoid invasions. • Plant and protect trees per BMP T5.16: Tree Retention and Tree Planting. . Aerate lawns regularly in areas of heavy use where the soil tends to become compacted. Con- duct aeration while the grasses in the lawn are growing most vigorously. Remove layers of thatch greater than %-inch deep. • Set the mowing height at the highest acceptable level and mow at times and intervals designed to minimize stress on the turf. Generally mowing only 1/3 of the grass blade height will prevent stressing the turf. • Mowing is a stress -creating activity for turfgrass. • Grass decreases its productivity when mowed too short and there is less growth of roots and rhizomes. The turf becomes less tolerant of environmental stresses, more dis- ease prone and more reliant on outside means such as pesticides, fertilizers, and irrig- ation to remain healthy. Additional BMP Information: . King County's Best Management Practices for Golf Course Development and Operation (King County, 1993) has additional BMPs for Turfgrass Maintenance and Operation. . King County, Seattle Public Utilities, and the Saving Water Partnership have created the fol- lowing natural lawn and garden care resources that include guidance on building healthy soil with compost and mulch, selecting appropriate plants, watering, using alternatives to pesti- cides, and implementing natural lawn care techniques. 2019 Stormwater Management Manual for Western Washington Volume IV - Chapter 4 - Page 526 ■ Natural Yard Care -Five steps to make your piece of the planet a healthier place to live (King County and SPU, 2008) ■ The Natural Lawn & Garden Series: Smart Watering (Saving Water Partnership, 2006) ■ Natural Lawn Care for Western Washington (Saving Water Partnership, 2007) ■ The Natural Lawn & Garden Series: Growing Healthy Soil, Choosing the Right Plants, - and Natural Pest, Weed and Disease Control (Saving Water Partnership, 2012) . The International Society of Arboriculture (ISA) is a group that promotes the professional prac- tice of arboriculture and fosters a greater worldwide awareness of the benefits of trees through research, technology, and education. ISA standards used for managing trees, shrubs, and other woody plants are the American National Standards Institute (ANSI) A300 standards. The ANSI A300 standards are voluntary industry consensus standards developed by the Tree Care Industry Association (TCIA) and written by the Accredited Standards Com- mittee (ASC). The ANSI standards can be found on the ISA website: www.isa-arbor.- com/education/publications/index.aspx . Washington State University's Gardening in Washington State website at http://garden- ing.wsu.edu contains Washington State specific information about vegetation management based on the type of landscape. . See the Pacific Northwest Plant Disease Management Handbook (Pscheidt and Ocamb, 2016) for information on disease recognition and for additional resources. %1n MPs for Soil Erosion and Sediment Contr strial Sites Description of utant Sources: Industrial activities on soil areas; expos and disturbed soils; steep grading; etc. can sources of sediments that can contaminate st water runoff. Pollutant Control Approac imit the exposure of erodible so' abilize, or cover erodible soil where necessary to prevent erosio and/or provide treatme or stormwater contaminated with TSS caused by eroded soil. Applicable BMPs: . Limit the exposure of erodible . Stabilize entrances/exits t revent track -out. See BM Access. 05: Stabilized Construction . StabilizZtive erodible soil to prevent erosion. Cover practice op%soila e: cover such as grass, trees, shrubs, on erodibl. o Cover exposed areas with mats such as clear plastic, jute, synthetic fiber C122: Nets and Blankets and BMP C123: Plastic Covering. MP 2019 Stormwater Management Manual for Western Washington Volume IV - Chapter 4 - Page 527 Avid Landscaping Site Improvements - 22414.20 Drainage Report September 6, 2023 Section VII, Page 4 SAMPLE ACTIVITY LOG DATE FACILITY MAINTENANCE PERFORMED RESULTS/ NOTES 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com