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SEE FILL GRADE BLD2023-1391 RESUB2 BLD2023-1127+DRAINAGE REPORT+5.3.2024_3.33.58_PM+4236785C � ENGINEERING 250 4ch Ave S Ste 200 Edmonds, WA 98020 Phone: (425) 778-8500 Fax: (425) 778-5536 civil & structural engineering & planning DRAINAGE REPORT Mathay Ballinger Park 24100 78th PI W, Edmonds, WA 98026 05103124 CG Project No.: 23072.20 Table of Contents Section I — Project Overview Section II — Off -Site Analysis Section III — Permanent Stormwater Control Plan Section IV — Construction Stormwater Pollution Prevention Plan Section V — Special Reports and/or Studies Section VI — Other Permits Section VII — Bond Quantities, Declaration of Covenant, & 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 Mathay Ballinger Park— CG # 23072.20 May 3, 2024 Drainage Report Section I, Page 1 Section I — Project Overview Section I Summary Overview Existing Condition Developed Condition Minimum Requirements Overview This report has been written for a new development at Mathay Ballinger Park, part of a 2.19-acre lot at 24100 78th PI W (TPN:00488700100100, 270431-004-028-00). The project consists of the construction of a restroom building, asphalt parking and walkways, and concrete picnic areas. The site proposes 9,422 sf of new/replaced impervious hard surface and will meet Minimum Requirements (MR) #1-9 of the 2019 Stormwater Management Manual for Western Washington (SWMMWW). The project will adhere to Edmonds Community Development Code (ECDC) Section 18.30 and the January 2024 Addendum to ECDC 18.30 (Edmonds Stormwater Addendum). Existing Condition The site is developed with a parking area, basketball court, play area, and concrete picnic area. According to the Geotech Report by Landau Associates, site soils are classified as recessional outwash with a design infiltration rate of 0.19 in/hr. This report and the NRCS Web Soil Survey Report completed for the site re included in Section V of this report. The site is bordered by residential properties with accesses to 78th PL W to the south and 240th ST SW to the north. A storm main generally runs north to south through the project site. The site moderately slopes southeast to existing catch basins at the south end of the site. The site does not appear to take on any significant upstream flow. The site resides in the Lake Ballanger watershed. The existing impervious areas on -site are as follows: Concrete Pavement: 2,217 sf (0.051 ac) Asphalt Pavement: 3,023 sf (0.069 ac) Total: 5,240 sf (0.120 ac) Developed Condition The project consists of the construction of a restroom building, additional parking, a asphalt walkway spanning the site, and several concrete picnic pads. Stormwater runoff will be infiltrated by one of two infiltration trenches. The total new/replaced impervious hard surface is 9,422 sf, and the total land disturbance is 16,967 sf. The proposed new/replaced impervious areas on -site are as follows: 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Mathay Ballinger Park— CG # 23072.20 Drainage Report May 3, 2024 Section I, Page 2 i 4 Roof: 190 sf (0.004 ac) Concrete Pavement: 516 sf (0.012 ac) Asphalt Pavement: 8,716 sf (0.200 ac) Total: 9,422 sf (0.216 ac) j VM 242 0 a 242111 79ft' ^ Figure 1-1. Vicinity map (Edmonds GIS). 21 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Mathay Ballinger Park— CG # 23072.20 May 3, 2024 Drainage Report Section I, Page 3 11 k• 241191 24118 s w w 14-288 16-685 _ JL Figure 1-2. Utilities Map (Edmonds GIS). M16-49 121 PLL3p 4M 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Mathay Ballinger Park— CG # 23072.20 May 3, 2024 Drainage Report Section I, Page 4 •%'wrXLl�3i� via f�+� 4N rT f •T Figure 1-3. Aerial Photo (Google Maps). Minimum Requirements Stormwater requirements were determined per the Edmonds Stormwater Addendum, ECDC 18.30, and the SWMMWW. This report is based on the steps recommended in Chapter 7 of the Edmonds Stormwater Addendum and Section 3.1.7 of the SWMMWW. The project is classified as Category 2 because it will result in more than 5,000 sf of new plus replaced hard surfaces. Following the flow chart in Figure 1-4, Minimum Requirements #1-9 will apply to all new and replaced hard surfaces. Minimum Requirement #1: Preparation of Stormwater Site Plans: The stormwater site plan consists of this report and the civil drawings and is prepared in accordance with Chapter 3 of Volume 1 of the SWMMWW and the requirements in the Edmonds Stormwater Addendum. Minimum Requirement #2: Construction Stormwater Pollution Prevention Plan (SWPPP): The SWPPP shall include a narrative and drawings. The SWPPP narrative shall include documentation that addresses the 13 elements of Construction Stormwater Pollution Prevention. See Section IV and the civil drawings. 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Mathay Ballinger Park— CG # 23072.20 May 3, 2024 Drainage Report Section I, Page 5 Minimum Requirement #3: Source Control of Pollution: All known, available and reasonable source control BMPs must be required for all projects approved by the City. Mandatory Operational Source Control BMPs must be implemented by forming a pollution prevention team, good housekeeping practices, preventive maintenance, spill prevention and cleanup, employee training, inspections, and record keeping. See Section IV for a source control discussion and Section VII for source control guide sheets from the SWMMWW. 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. Runoff in the park is collected in catch basins which route stormwater toward 78t" Place West. Overflows from the proposed stormwater facilities will match this condition. A qualitative analysis of the upstream and downstream system entering the site is presented in Section II. Minimum Requirement #5: On -Site Stormwater Management: The proposed project is classified as a Category 2 project site per the Edmonds Stormwater Addendum. The project will either use on -site stormwater management BMPs from List No. 2 or use flow control BMPs to meet the LID performance standard. The project will meet the LID performance standard. See Section III for discussion. 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 in less than 5,000 sf of new pollution -generating hard surfaces. See Section III for discussion. Minimum Requirement #7: Flow Control: Flow control is required for projects that either will have an effective impervious surface of greater than 10,000 square feet in a threshold discharge area, will convert 0.75 acres or more of vegetation to lawn or landscape, or will cause a or surpass a 0.15 cubic feet per second (cfs) increase in the 100-year flow frequency from a threshold discharge area as estimated using WWHM or another approved model and 15-minute time steps. The project does not meet any of these thresholds, and flow control is not required. See Section III for Discussion. Minimum Requirement #8: Wetlands Protection: Not applicable. There are no wetlands located in the immediate 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 Flow Control BMPs/facilities. The party (or parties) responsible for maintenance and operation shall be identified in the operation and maintenance manual. For private facilities approved by the City, a copy of the operation and maintenance manual shall be retained on -site 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Mathay Ballinger Park— CG # 23072.20 Drainage Report May 3, 2024 Section I, Page 6 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. Lkxs the project result in 2,000 square feet, or greater, of new plus replaced hard surface area? OR Does the land disturbing activity total 7,000 square feet or greater.' Yea No Minimum Requirements No. I through 5 apple I Minimum Requirement No. 2 applic,. Next Question Does the project add 5,000 square tcct or more of new plus replaced hard surfaces? OR Convert 0.75 acres or more of vegetation to lawn or landscaped areas? OR Convert 2.5 acres or more of native vegetation to pasture? Tee Is this a road related project" No Tee Doc% the project add 5,000 square feet or No more of new hard surfaces? Yes All Minimum Requirements apply to the new and replaced Yea Do new hard surfaces add 50% or hard surfaces and converted more to the existing hard surfaces vegetation areas. within the project limits? All Minimum Requirements No � apply to the new hard surfaces Nil ,iiJ:uun�l and concerted vegetation areas. requucment; Figure 1-4. Flow chart for determining requirements for new development (Figure 3.1 in the Edmonds Stormwater Addendum). 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Mathay Ballinger Park— CG # 23072.20 May 3, 2024 Drainage Report Section II, Page 1 Section II — Off -Site Analysis Section II Summary Task 1— Define and map the study area Task 2 — Review all available information of the study area Task 3 — Field inspect the area Task 4 - Describe the drainage system, and its existing and predicted problems Task 1— Define and map the study area An initial qualitative analysis shall document potential off -site impacts of stormwater discharges for each upstream drainage system entering a site, and each downstream drainage system leaving a site according to Section 6.2 of the Edmonds Stormwater Addendum. The downstream analysis shall extend from the project site to the receiving water, or up to one -quarter mile, whichever is less. Runoff from the site that is not infiltrated will enter the city public storm main flowing southward down 78t" PL W to 242"d ST SW. From there it flows eastward down 242"d ST SW until reaching 76t" AVE W where the flow splits flowing north up 76t" then traveling east or continuing down 242nd. Eventually, the flow outfalls into Lake Ballinger after being conveyed 0.33 miles. The downstream flow path from the site is outlined in Figure II-1 from the Edmonds GIS map. ,.;On I FL SW PROJECT SITE 41 ST ST SW ^ 0 OUTFALL ST SW i e• 7410 24206 24112 71211 24211 :4,'l 24218 24219 i4(lh 92v �L eW � - a 4 421- • OUTFACE ro 2n un • Figure II-1. Vicinity map showing stormwater flow path and distance to outfall (Edmonds GIS). C �M ENGINEERING 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Mathay Ballinger Park— CG # 23072.20 Drainage Report May 3, 2024 Section II, Page 2 Task 2 — Review all available information on the studv area Existing stormwater improvements were determined from the survey and the City GIS map. The existing downstream drainage system is described in Task 1. The DOE Water Quality Atlas Map was used to find any Category 5 — 303D listings for the outfall. Lake Ballinger has 303D listings for 2,3,7,8-TCDD (Dioxin), Polychlorinated Biphenyls (PCBs), Bacteria — Fecal Coliform, and Methyl Mercury. Task 3 — Field inspect the study area From evaluating surrounding conditions, the site does not appear to take on significant upstream runoff. Runoff in the park is collected in catch basins which route stormwater toward 78t" Place West. Overflows from the proposed stormwater facilities will match this condition. Task 4 — Describe the drainage system, and its existing and predicted problems There does not appear to be any problems present. In the proposed condition, stormwater will be routed to infiltration trenches with an overflow to existing storm infrastructure at the south end of the site. There are no anticipated problems with this system. 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Mathay Ballinger Park— CG # 23072.20 May 3, 2024 Drainage Report Section III, Page 1 Section III — Permanent Stormwater Control Plan Section III Summary Narrative On -Site Stormwater Management Runoff Treatment Flow Control WWHM Infiltration Trench Report WWHM Flow Control Check Alrrrrrytivo This section specifically addresses SWMMWW Minimum Requirements #5-#7: On -site Stormwater Management, Runoff Treatment, and Flow Control. On -site Stormwater Management The project proposes to meet the LID performance standard using flow control BMPs for all new/replaced hard surfaces and apply BMP T5.13: Post -Construction Soil Quality and Depth for all disturbed pervious surfaces. The existing hard surfaces on site do not drain to an approved stormwater management facility. Therefore, per ECDC 18.30.060.D.5.iii, the retrofit requirement will be applied, and 25% of existing hard surfaces on site will be included as area for meeting the LID performance standard. The project proposes to meet the LID standard with infiltration trenches. Using a design infiltration rate of 0.19 in/hr, a 72'x10'x2'trench was sized. This trench is split into an upper 47'x10'x2' trench and a lower 27'x10'x2' trench. The WWHM report for the trench is attached at the end of this Section. The areas as included in the WWHM model are as follows: Roof: 190 sf (0.004 ac) Concrete Pavement: 516 sf (0.012 ac) Concrete Pavement (25% Retrofit): 532 sf (0.012 ac) Asphalt Pavement: 8,716 sf (0.200 ac) Asphalt Pavement (25% Retrofit): 756 sf (0.017 ac) Total: 10,710 sf (0.246 ac) Runoff Treatment The project proposes less than 5,000 sf of pollution generating hard surface (PGHS), and runoff treatment is not required. The proposed PGHS on site is as follows: 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Mathay Ballinger Park— CG # 23072.20 Drainage Report May 3, 2024 Section III, Page 2 Asphalt Parking: 1,803 sf (0.041 ac) Total: 1,803 sf (0.041 ac) Flow Control The project has a total of less than 10,000 sf of effective impervious areas, converts less than % acres of vegetation to land or landscape, and causes a less than 0.15 cfs increase in the 100-year flow frequency using WWHM. Therefore, flow control is not required. The WWHM report for the 0.15 cfs flow increase check is attached at the end of this Section. 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: WWWHM 2' Trench Site Name: Mathay Ballinger Park Site Address: 24102 77TH PL W City : EDMOND Report Date: 4/8/2024 Gage : Everett Data Start : 1948/10/01 Data End : 2009/09/30 Precip Scale: 1.00 Version Date: 2021/08/18 Version : 4.2.18 Low Flow Threshold for POC 1 : 50 Percent of the 2 Year High Flow Threshold for POC 1: 50 year PREDEVELOPED LAND USE Name : Basin 1 Bypass: No Groundwater: No Pervious Land Use acre C. Forest, Flat .111 C, Forest, Mod .134 Pervious Total 0.245 Impervious Land Use acre Impervious Total 0 Basin Total 0.245 Element Flows To: Surface Interflow Groundwater MITIGATED LAND USE Name : Basin 1 Bypass: No Groundwater: No Pervious Land Use acre Pervious Total 0 Impervious Land Use acre ROOF TOPS FLAT 0.004 SIDEWALKS FLAT 0.066 SIDEWALKS MOD 0.133 PARKING FLAT 0.042 Impervious Total 0.245 Basin Total 0.245 Element Flows To: Surface Interflow Groundwater Gravel Trench Bed 1 Gravel Trench Bed 1 Name : Gravel Trench Bed 1 Bottom Length: 72.00 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: 2 Pour Space of material for first layer: 0.3 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: 0.19 Infiltration safety factor: 1 Total Volume Infiltrated (ac-ft.): 32.109 Total Volume Through Riser (ac-ft.): 6.407 Total Volume Through Facility (ac-ft.): 38.516 Percent Infiltrated: 83.37 Total Precip Applied to Facility: 0 Total Evap From Facility: 0 Discharge Structure Riser Height: 1.95 ft. Riser Diameter: 12 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 0.016 0.000 0.000 0.000 0.0222 0.016 0.000 0.000 0.003 0.0444 0.016 0.000 0.000 0.003 0.0667 0.016 0.000 0.000 0.003 0.0889 0.016 0.000 0.000 0.003 0.1111 0.016 0.000 0.000 0.003 0.1333 0.016 0.000 0.000 0.003 0.1556 0.016 0.000 0.000 0.003 0.1778 0.016 0.000 0.000 0.003 0.2000 0.016 0.001 0.000 0.003 0.2222 0.016 0.001 0.000 0.003 0.2444 0.016 0.001 0.000 0.003 0.2667 0.016 0.001 0.000 0.003 0.2889 0.016 0.001 0.000 0.003 0.3111 0.016 0.001 0.000 0.003 0.3333 0.016 0.001 0.000 0.003 0.3556 0.016 0.001 0.000 0.003 0.3778 0.016 0.001 0.000 0.003 0.4000 0.016 0.002 0.000 0.003 0.4222 0.016 0.002 0.000 0.003 0.4444 0.016 0.002 0.000 0.003 0.4667 0.016 0.002 0.000 0.003 0.4889 0.016 0.002 0.000 0.003 0.5111 0.016 0.002 0.000 0.003 0.5333 0.016 0.002 0.000 0.003 0.5556 0.016 0.002 0.000 0.003 0.5778 0.016 0.002 0.000 0.003 0.6000 0.016 0.003 0.000 0.003 0.6222 0.016 0.003 0.000 0.003 0.6444 0.016 0.003 0.000 0.003 0.6667 0.016 0.003 0.000 0.003 0.6889 0.016 0.003 0.000 0.003 0.7111 0.016 0.003 0.000 0.003 0.7333 0.016 0.003 0.000 0.003 0.7556 0.016 0.003 0.000 0.003 0.7778 0.016 0.003 0.000 0.003 0.8000 0.016 0.004 0.000 0.003 0.8222 0.016 0.004 0.000 0.003 0.8444 0.016 0.004 0.000 0.003 0.8667 0.016 0.004 0.000 0.003 0.8889 0.016 0.004 0.000 0.003 0.9111 0.016 0.004 0.000 0.003 0.9333 0.016 0.004 0.000 0.003 0.9556 0.016 0.004 0.000 0.003 0.9778 0.016 0.004 0.000 0.003 1.0000 0.016 0.005 0.000 0.003 1.0222 0.016 0.005 0.000 0.003 1.0444 0.016 0.005 0.000 0.003 1.0667 0.016 0.005 0.000 0.003 1.0889 0.016 0.005 0.000 0.003 1.1111 0.016 0.005 0.000 0.003 1.1333 0.016 0.005 0.000 0.003 1.1556 0.016 0.005 0.000 0.003 1.1778 0.016 0.005 0.000 0.003 1.2000 0.016 0.006 0.000 0.003 1.2222 0.016 0.006 0.000 0.003 1.2444 0.016 0.006 0.000 0.003 1.2667 0.016 0.006 0.000 0.003 1.2889 0.016 0.006 0.000 0.003 1.3111 0.016 0.006 0.000 0.003 1.3333 0.016 0.006 0.000 0.003 1.3556 0.016 0.006 0.000 0.003 1.3778 0.016 0.006 0.000 0.003 1.4000 0.016 0.006 0.000 0.003 1.4222 0.016 0.007 0.000 0.003 1.4444 0.016 0.007 0.000 0.003 1.4667 0.016 0.007 0.000 0.003 1.4889 0.016 0.007 0.000 0.003 1.5111 0.016 0.007 0.000 0.003 1.5333 0.016 0.007 0.000 0.003 1.5556 0.016 0.007 0.000 0.003 1.5778 0.016 0.007 0.000 0.003 1.6000 0.016 0.007 0.000 0.003 1.6222 0.016 0.008 0.000 0.003 1.6444 0.016 0.008 0.000 0.003 1.6667 0.016 0.008 0.000 0.003 1.6889 0.016 0.008 0.000 0.003 1.7111 0.016 0.008 0.000 0.003 1.7333 0.016 0.008 0.000 0.003 1.7556 0.016 0.008 0.000 0.003 1.7778 0.016 0.008 0.000 0.003 1.8000 0.016 0.008 0.000 0.003 1.8222 0.016 0.009 0.000 0.003 1.8444 0.016 0.009 0.000 0.003 1.8667 0.016 0.009 0.000 0.003 1.8889 0.016 0.009 0.000 0.003 1.9111 0.016 0.009 0.000 0.003 1.9333 0.016 0.009 0.000 0.003 1.9556 0.016 0.009 0.004 0.003 1.9778 0.016 0.009 0.049 0.003 2.0000 0.016 0.009 0.118 0.003 ANALYSIS RESULTS Stream Protection Duration Predeveloped Landuse Totals for POC #1 Total Pervious Area:0.245 Total Impervious Area:O Mitigated Landuse Totals for POC #1 Total Pervious Area:O Total Impervious Area:0.245 Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 5 year 10 year 25 year 50 year 100 year 0.005384 0.008095 0.009972 0.012414 0.014273 0.016162 Flow Frequency Return Periods for Mitigated Return Period Flow(cfs) 2 year 0.079777 5 year 0.112324 10 year 0.135345 25 year 0.166075 50 year 0.190155 100 year 0.21525 Stream Protection Duration Annual Peaks for Predeveloped and Mitigated Year Predeveloped Mitigated 1949 0.003 0.053 1950 0.006 0.110 1951 0.005 0.094 1952 0.004 0.070 1953 0.003 0.055 1954 0.014 0.130 1955 0.008 0.108 1956 0.007 0.053 1957 0.008 0.095 1958 0.005 0.113 1959 0.006 0.088 1960 0.005 0.072 1961 0.005 0.155 1962 0.005 0.083 1963 0.006 0.146 1964 0.005 0.056 1965 0.005 0.043 1966 0.003 0.041 1967 0.006 0.206 1968 0.008 0.110 1969 0.007 0.125 1970 0.004 0.060 1971 0.006 0.084 1972 0.005 0.166 1973 0.004 0.059 1974 0.008 0.170 1975 0.004 0.062 1976 0.004 0.083 1977 0.003 0.090 1978 0.004 0.060 1979 0.008 0.140 1980 0.005 0.044 1981 0.004 0.074 1982 0.005 0.073 1983 0.008 0.076 1984 0.005 0.057 1985 0.007 0.092 POC #1 POC #1 1986 0.017 0.095 1987 0.007 0.120 1988 0.004 0.056 1989 0.004 0.040 1990 0.005 0.060 1991 0.006 0.070 1992 0.004 0.095 1993 0.003 0.077 1994 0.003 0.044 1995 0.006 0.079 1996 0.010 0.093 1997 0.019 0.117 1998 0.003 0.111 1999 0.005 0.057 2000 0.003 0.070 2001 0.001 0.078 2002 0.005 0.040 2003 0.004 0.067 2004 0.006 0.174 2005 0.004 0.071 2006 0.012 0.091 2007 0.010 0.103 2008 0.014 0.079 2009 0.004 0.054 Stream Protection Duration Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.0190 0.2065 2 0.0171 0.1742 3 0.0141 0.1696 4 0.0138 0.1662 5 0.0119 0.1551 6 0.0100 0.1458 7 0.0097 0.1401 8 0.0083 0.1301 9 0.0083 0.1245 10 0.0079 0.1198 11 0.0078 0.1166 12 0.0077 0.1133 13 0.0075 0.1105 14 0.0075 0.1102 15 0.0071 0.1098 16 0.0070 0.1075 17 0.0066 0.1032 18 0.0064 0.0954 19 0.0062 0.0948 20 0.0061 0.0948 21 0.0061 0.0940 22 0.0058 0.0934 23 0.0058 0.0917 24 0.0058 0.0912 25 0.0055 0.0896 26 0.0054 0.0880 27 0.0054 0.0838 28 0.0053 0.0833 29 0.0052 0.0831 30 0.0052 0.0789 31 0.0052 0.0786 32 0.0051 0.0785 33 0.0050 0.0766 34 0.0050 0.0760 35 0.0050 0.0738 36 0.0050 0.0728 37 0.0046 0.0724 38 0.0046 0.0711 39 0.0045 0.0705 40 0.0045 0.0701 41 0.0044 0.0700 42 0.0044 0.0675 43 0.0041 0.0622 44 0.0041 0.0602 45 0.0041 0.0601 46 0.0041 0.0599 47 0.0041 0.0588 48 0.0039 0.0571 49 0.0039 0.0568 50 0.0038 0.0559 51 0.0038 0.0557 52 0.0038 0.0555 53 0.0035 0.0540 54 0.0033 0.0528 55 0.0031 0.0528 56 0.0030 0.0445 57 0.0029 0.0436 58 0.0028 0.0427 59 0.0028 0.0406 60 0.0027 0.0402 61 0.0009 0.0396 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 500 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 Gravel Trench Bed 1 POC N 35.05 N 83.37 Total Volume Infiltrated 35.05 0.00 0.00 83.37 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. 2005-2024; All Rights Reserved. WWHM2012 PROJECT REPORT Project Name: 23072 Mathay Ballanger (0.15 Calc) Site Name: Mathay Ballinger Park Site Address: 24102 77TH PL W City : EDMOND Report Date: 10/20/2023 Gage : Everett Data Start : 1948/10/01 Data End : 2009/09/30 Precip Scale: 1.00 Version Date: 2019/09/13 Version : 4.2.17 Low Flow Threshold for POC 1 : 50 Percent of the 2 Year High Flow Threshold for POC 1: 50 year PREDEVELOPED LAND USE Name : Basin 1 Bypass: No GroundWater: No Pervious Land Use acre C, Lawn, Flat .766 C, Forest, Flat .089 C, Forest, Mod .326 C, Lawn, Mod .444 C, Forest, Steep .151 C, Lawn, Steep .186 Pervious Total 1.962 Impervious Land Use acre SIDEWALKS FLAT 0.058 Impervious Total 0.058 Basin Total 2.02 Element Flows To: Surface Interflow Groundwater MITIGATED LAND USE Name : Basin 1 Bypass: No GroundWater: No Pervious Land Use acre C, Forest, Flat .101 C, Forest, Mod .47 C, Forest, Steep .197 C, Lawn, Flat .632 C, Lawn, Mod .212 C, Lawn, Steep .124 Pervious Total 1.736 Impervious Land Use acre ROOF TOPS FLAT 0.004 DRIVEWAYS FLAT 0.004 SIDEWALKS FLAT 0.172 SIDEWALKS MOD 0.089 SIDEWALKS STEEP 0.015 Impervious Total 0.284 Basin Total 2.02 Element Flows To: Surface Interflow Groundwater ANALYSIS RESULTS Stream Protection Duration Predeveloped Landuse Totals for POC #1 Total Pervious Area:1.962 Total Impervious Area:0.058 Mitigated Landuse Totals for POC #1 Total Pervious Area:1.736 Total Impervious Area:0.284 Flow Frequency Return Return Period 2 year 5 year 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 Periods for Flow (cfs) 0.163225 0.290452 0.397606 0.561219 0.704985 0.868676 Predeveloped Periods for Mitigated Flow (cfs) 0.217594 0.343182 0.444285 0.594288 0.723395 0.868419 Stream Protection Duration Annual Peaks for Predeveloped and Mitigated Year Predeveloped Mitigated 1949 0.249 0.290 1950 0.276 0.323 1951 0.132 0.168 1952 0.164 0.213 1953 0.175 0.242 1954 0.487 0.528 1955 0.266 0.305 1956 0.119 0.143 1957 0.270 0.293 1958 0.622 0.678 1959 0.133 0.194 1960 0.205 0.247 1961 0.997 0.999 1962 0.165 0.206 1963 0.365 0.396 1964 0.166 0.185 1965 0.063 0.112 1966 0.066 0.123 1967 0.154 0.267 1968 0.181 0.222 1969 0.715 0.724 1970 0.117 0.159 1971 0.217 0.270 1972 0.313 0.369 1973 0.191 0.258 1974 0.262 0.315 1975 0.233 0.285 1976 0.117 0.150 1977 0.065 0.123 1978 0.071 0.119 1979 0.384 0.410 1980 0.154 0.196 1981 0.098 0.142 1982 0.106 0.134 1983 0.225 0.276 POC #1 POC #1 POC #1 1984 0.142 0.198 1985 0.206 0.245 1986 0.359 0.406 1987 0.153 0.236 1988 0.103 0.182 1989 0.209 0.253 1990 0.088 0.142 1991 0.076 0.127 1992 0.162 0.221 1993 0.087 0.145 1994 0.085 0.117 1995 0.084 0.137 1996 0.233 0.270 1997 0.461 0.469 1998 0.240 0.296 1999 0.073 0.118 2000 0.207 0.384 2001 0.042 0.095 2002 0.069 0.090 2003 0.053 0.121 2004 0.263 0.379 2005 0.075 0.141 2006 0.302 0.344 2007 0.259 0.308 2008 0.173 0.198 2009 0.096 0.156 Stream Protection Duration Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.9965 0.9987 2 0.7150 0.7235 3 0.6220 0.6784 4 0.4871 0.5278 5 0.4609 0.4686 6 0.3845 0.4101 7 0.3650 0.4056 8 0.3586 0.3965 9 0.3127 0.3837 10 0.3022 0.3785 11 0.2761 0.3693 12 0.2699 0.3441 13 0.2655 0.3232 14 0.2632 0.3147 15 0.2623 0.3079 16 0.2594 0.3048 17 0.2486 0.2960 18 0.2396 0.2928 19 0.2333 0.2898 20 0.2325 0.2846 21 0.2251 0.2757 22 0.2167 0.2702 23 0.2087 0.2695 24 0.2075 0.2672 25 0.2058 0.2582 26 0.2045 0.2528 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 0.1907 0.2468 0.1806 0.2450 0.1750 0.2422 0.1725 0.2356 0.1661 0.2218 0.1646 0.2207 0.1637 0.2129 0.1625 0.2060 0.1544 0.1982 0.1541 0.1981 0.1531 0.1961 0.1420 0.1939 0.1330 0.1855 0.1316 0.1821 0.1186 0.1684 0.1169 0.1589 0.1169 0.1558 0.1056 0.1503 0.1027 0.1446 0.0975 0.1425 0.0961 0.1419 0.0877 0.1418 0.0874 0.1409 0.0853 0.1370 0.0838 0.1340 0.0763 0.1269 0.0754 0.1228 0.0726 0.1226 0.0713 0.1205 0.0685 0.1194 0.0664 0.1179 0.0654 0.1174 0.0628 0.1123 0.0532 0.0946 0.0420 0.0897 Stream Protection Duration 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 Percent Water Quality Percent Comment Treatment? Needs Volume Water Quality Treatment Infiltrated Treated (ac-ft Total Volume Infiltrated 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. Volume Infiltration Cumulative Through Volume Facility (ac-ft.) (ac-ft) 0.00 0.00 Volume Infiltration Credit 0.00 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. Mathay Ballinger Park— CG # 23072.20 May 3, 2024 Drainage Report Section IV, Page 1 Section IV— Construction Stormwater Pollution Prevention Plan Section IV Summary: Narrative Source Control Narrative Erosion control details are provided consistent with the City of Edmonds guidelines. Erosion control plan sheets are provided in full-size as a part of the civil drawing set. For sites with disturbance under one acre in area, the Department of Ecology (DOE) does not require completion of the full Construction SWPPP or the Construction Stormwater General Permit. Therefore, a Construction SWPPP is not required for this site. The following is an abbreviated format of the SWPPP that addresses each of the 13 elements of construction pollution prevention for the city review. Element 1: Mark clearing limits To protect adjacent properties and to reduce the area of soil exposed to construction, the limits of construction will be clearly marked before land -disturbing activities begin. Clearing limits will be to the extents of necessary land disturbance for the new building and this can be seen on drawing sheet C2.1. 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. A stabilized construction entrance should be utilized as needed when possible to prevent sediment tracking. See C2.1 for placement. The BMPs relevant to establishing construction access that will be applied for this project include: Stabilized Construction Entrance (BMP C105) Element 3: Control Flow Rates The site generally moderately slopes from northwest to southeast. The site is small enough that a silt fence used for Element 4 may be used to control flow rates. Element 4: Install sediment controls All stormwater runoff from disturbed areas shall pass through an appropriate sediment removal BMP before leaving the construction site or prior to being discharged. Silt fences will be installed on the 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Mathay Ballinger Park— CG # 23072.20 May 3, 2024 Drainage Report Section IV, Page 2 downstream ends. Pollution prevention facilities on the erosion control plan must be constructed prior to or in conjunction with all clearing and grading so as to ensure that the transport of sediment to surface waters and adjacent properties is minimized. The specific BMPs to be used for controlling sediment on this project include: Silt Fence (BMP C233) Element 5: Stabilize Soils Exposed and unworked soils shall be stabilized with the application of effective BMPs to prevent erosion throughout the life of the project. The specific BMPs for soil stabilization that shall be used on this project include: Temporary and Permanent Seeding (BMP C120) Mulching (BMP C121) Nets and Blankets (BMP C122) Plastic Covering (BMP C123) Sodding (BMP C124) Topsoiling/Composting (BMP C125) Surface Roughening (BMP C130) Dust Control (BMP C140) Element 6: Protect Slopes There are existing surfaces that will be removed as part of the development. Exposed slopes shall be stabilized with BMPs found in Element 5. Element 7: Protect Drain Inlets Catch basins along Main St and the alley and as made operable on -site will be protected from sedimentation. Stormwater shall not enter the conveyance system without first being filtered or treated to remove sediment. Inlet protection devices shall be cleaned or removed and replaced when sediment has filled one-third of the available storage (or as specified by the manufacturer). The specific BMPs to be used for protecting drain inlets are: Storm Drain Inlet Protection (BMP C220) 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: 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Mathay Ballinger Park— CG # 23072.20 Drainage Report May 3, 2024 Section IV, Page 3 Concrete Handling (BMP C151) Saw cutting and Surfacing Pollution Prevention (BMP C152) Material Delivery, Storage and Containment (BMP C153) For this site, controlling the pollutants will also require strict compliance with the EMMP for the project. Section 10 of the EMMP lists requirements and recommendations for several different construction activities. Element 10: Control Dewatering De -watering is not anticipated, but if needed, should follow the EMMP. 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 take into account seasonal work limits. • Follow the recommendations and requirements of the EMMP. • 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 Install high visibility orange protective fencing around the areas of the proposed infiltration trenches. Cntirrc rnntrnlc This project should incorporate required BMPs from Volume IV of the DOE Manual: -S411— BMPs for Landscaping and Lawn/Vegetation Management -S417 — BMPs for Maintenance of Stormwater Drainage and Treatment Systems -S453 — BMPs for Formation of a Pollution Prevention Team 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Mathay Ballinger Park— CG # 23072.20 Drainage Report May 3, 2024 Section IV, Page 4 -S454 — BMPs for Preventative Maintenance/Good Housekeeping -S455 — BMPS for Spill Prevention and Cleanup -S457 — BM Ps for Inspections -S456 — BMPs for Record Keeping Many of these Department of Ecology Source Controls are straightforward practices that should be performed on any site per the recommendations in the included pages of this report. 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Mathay Ballinger Park— CG # 23072.20 Drainage Report May 3, 2024 Section V, Page 1 Section V — Special Reports and/or Studies Section V Summary: Narrative The following reports are included in this section: 1. NRCS Web Soil Survey dated August 8t", 2023. 2. Summary of Geotechnical Engineering Services by Landau Associates, dated December 27, 2023. 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com 3 N O N N 549410 47° 46' S3" N q 47o 46 47" N 3 o Map Scale: 1:1,480 if printed on A landscape (11" x 8.5") sheet N Meters NN 0 20 40 80 120 /V 0 50 100 200 300 Map projection: Web Mercator Comer coordinates: WGS84 Edge tics: UTM Zone 1ON WGS84 9 549W 549470 1 549500 1 Custom Soil Resource Report Soil Map 5495M 549%0 549590 ISM a Soi1'�Map may not be v_aflid A �. g - I I I I 549410 549440 549470 549500 549530 549560 549590 549620 549650 54%80 3 b O N N N 549710 47° 46' 53" N �I 47° 46' 47" N 549710 3 0 MAP LEGEND Area of Interest (AOI) E] Area of Interest (AO I) Soils 0 Soil Map Unit Polygons py Soil Map Unit Lines Soil Map Unit Points Special Point Features V Blowout ® Borrow Pit Clay Spot 0 Closed Depression Gravel Pit Gravelly Spot O Landfill x Lava Flow 4& Marsh or swamp Mine or Quarry O Miscellaneous Water OPerennial Water V Rock Outcrop + Saline Spot Sandy Spot Severely Eroded Spot C Sinkhole Slide or Slip o Sodic Spot Custom Soil Resource Report MAP INFORMATION y Spoil Area The soil surveys that comprise your AOI were mapped at 1:24,000. Q Stony Spot Very Stony Spot Warning: Soil Map may not be valid at this scale. d Wet Spot Enlargement of maps beyond the scale of mapping can cause p Other misunderstanding of the detail of mapping and accuracy of soil .• Special Line Features line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed Water Features scale. Streams and Canals Transportation Please rely on the bar scale on each map sheet for map 044 Rails measurements. ^/ Interstate Highways Source of Map: Natural Resources Conservation Service .y US Routes Web Soil Survey URL: Coordinate System: Web Mercator (EPSG:3857) Major Roads Local Roads Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts Background distance and area. A projection that preserves area, such as the Aerial Photography Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: Snohomish County Area, Washington Survey Area Data: Version 24, Sep 8, 2022 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Jul 31, 2022—Aug 8, 2022 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. 10 Custom Soil Resource Report Map Unit Legend Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI 5 Alderwood-Urban land complex, 2 to 8 percent slopes 6.5 62.5% 6 Alderwood-Urban land complex, 8 to 15 percent slopes 3.9 37.5% Totals for Area of Interest 10.4 100.0% 11 Custom Soil Resource Report Snohomish County Area, Washington 5—Alderwood-Urban land complex, 2 to 8 percent slopes Map Unit Setting National map unit symbol: 2hz9 Elevation: 50 to 800 feet Mean annual precipitation: 25 to 60 inches Mean annual air temperature: 48 to 52 degrees F Frost -free period. 180 to 220 days Farmland classification: Not prime farmland Map Unit Composition Alderwood and similar soils: 60 percent Urban land: 25 percent Minor components: 15 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Alderwood Setting Landform: Till plains Parent material: Basal till Typical profile H1 - 0 to 7 inches: gravelly ashy sandy loam H2 - 7 to 35 inches: very gravelly ashy sandy loam H3 - 35 to 60 inches: gravelly sandy loam Properties and qualities Slope: 2 to 8 percent Depth to restrictive feature: 20 to 40 inches to densic material Drainage class: Moderately well drained Capacity of the most limiting layer to transmit water (Ksat): Very low to moderately low (0.00 to 0.06 in/hr) Depth to water table: About 18 to 36 inches Frequency of flooding: None Frequency of ponding: None Available water supply, 0 to 60 inches: Low (about 3.0 inches) Interpretive groups Land capability classification (irrigated): None specified Land capability classification (nonirrigated): 4s Hydrologic Soil Group: B Ecological site: F002XA004WA - Puget Lowlands Forest Forage suitability group: Limited Depth Soils (G002XN302WA) Other vegetative classification: Limited Depth Soils (G002XN302WA) Hydric soil rating: No Minor Components Norma, undrained Percent of map unit: 5 percent Landform: Depressions Other vegetative classification: Wet Soils (G002XN102WA) Hydric soil rating: Yes `" Custom Soil Resource Report Terric medisaprists, undrained Percent of map unit: 5 percent Landform: Depressions Other vegetative classification: Wet Soils (G002XN102WA) Hydric soil rating: Yes Mckenna Percent of map unit: 5 percent Landform: Depressions Other vegetative classification: Wet Soils (G002XN102WA) Hydric soil rating: Yes 6—Alderwood-Urban land complex, 8 to 15 percent slopes Map Unit Setting National map unit symbol: 2hzn Elevation: 50 to 800 feet Mean annual precipitation: 25 to 60 inches Mean annual air temperature: 48 to 52 degrees F Frost -free period: 180 to 220 days Farmland classification: Not prime farmland Map Unit Composition Alderwood and similar soils: 60 percent Urban land: 25 percent Minor components: 5 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Alderwood Setting Landform: Till plains Parent material: Basal till Typical profile H1 - 0 to 7 inches: gravelly ashy sandy loam H2 - 7 to 35 inches: very gravelly ashy sandy loam H3 - 35 to 60 inches: gravelly sandy loam Properties and qualities Slope: 8 to 15 percent Depth to restrictive feature: 20 to 40 inches to densic material Drainage class: Moderately well drained Capacity of the most limiting layer to transmit water (Ksat): Very low to moderately low (0.00 to 0.06 in/hr) Depth to water table: About 18 to 36 inches Frequency of flooding: None Frequency of ponding: None Available water supply, 0 to 60 inches: Low (about 3.0 inches) 13 Custom Soil Resource Report Interpretive groups Land capability classification (irrigated): None specified Land capability classification (nonirrigated): 4s Hydrologic Soil Group: B Ecological site: F002XA004WA - Puget Lowlands Forest Forage suitability group: Limited Depth Soils (G002XN302WA) Other vegetative classification: Limited Depth Soils (G002XN302WA) Hydric soil rating: No Minor Components Norma, undrained Percent of map unit: 5 percent Landform: Drainageways Other vegetative classification: Wet Soils (G002XN102WA) Hydric soil rating: Yes 14 LALANDAU A S S O C I A T E S TECHNICAL MEMORANDUM TO: Kyle Woods, City of Edmonds, Planner and Capital Project Manager FROM: Steven R. Wright, PE DATE: December 27, 2023 RE: Summary of Geotechnical Engineering Services Mathay-Ballinger Park Project Edmonds, Washington Project No. 074217.010 INTRODUCTION This memorandum summarizes the results of geotechnical engineering services provided by Landau Associates, Inc. (Landau) in support of the Mathay-Ballinger Park Project in Edmonds, Washington (site, Figure 1). Services were provided in accordance with the scope outlined in Task Order No. 1 for the professional services agreement for on -call geotechnical services between Landau and the City of Edmonds Parks, Recreation & Human Services Department (City, project owner), executed on May 10, 2023. This memorandum has been prepared with information provided by the City, along with data collected during Landau's geotechnical field exploration and laboratory testing programs. PROJECT UNDERSTANDING The City proposes to complete improvements to Mathay-Bal linger Park in two phases. Phase 1 will include construction of a picnic shelter, a single -stall restroom, picnic tables, benches, and paved walkways. Phase 2 will include construction of two soft -surface loop trails and seven new parking stalls and resurfacing of two sport courts. Retaining walls, anticipated to be less than 4 feet (ft) high, may be required in certain areas along the new paved walkways. If feasible, stormwater runoff generated by impervious surfaces will be infiltrated on site. Preliminary plans for the two project phases are shown on Attachment 1; the locations of the proposed improvements will be finalized during the design phase. SITE CONDITIONS The proposed site improvements will be constructed generally within the central portion of the park. Existing improvements at the site include a playground, small parking lot, two sport courts, and benches. The site has two entrances: one off of 78th PI W to the south and one off of 240th St SW to the north near its intersection with the Interurban Trail. The park is in a residential neighborhood. SEATTLE 155 NE 100th Street, Ste 302, Seattle, WA 98125 T 206.631.8680 landauinc.com Summary of Geotechnical Engineering Services - Mathay-Ballinger Park Project December 27, 2023 GEOLOGIC SETTING Geologic information for the site and the surrounding area was obtained from the Geologic Map of the Edmonds East and Part of the Edmonds West Quadrangles, Washington (Minard 1983). Surficial deposits at the site are mapped as Vashon till (Qvt), a unit that is classified as poorly sorted, non -stratified mixture of clay, silt, sand, pebbles, and cobbles with occasional boulders. Within the vicinity of the site recessional outwash (Qvr), a unit that is classified as stratified sand and gravel with minor silt and clay layers with the inclusion of unstratified to poorly stratified ablation and melt -out deposits is also mapped. The subsurface conditions observed in Landau's explorations were generally consistent with the recessional outwash unit. SUBSURFACE CONDITIONS On May 24, 2023, Landau's excavating subcontractor advanced four test pits (TP-1 through TP-4) 9 to 10.25 ft below ground surface (bgs) and completed one small-scale pilot infiltration test (PIT; PIT-1) investigation at 3 ft bgs. Following the PIT investigation, exploration PIT-1 was extended to 10.5 ft bgs. The approximate locations of the explorations are shown on Figure 2. Landau personnel coordinated and monitored the explorations, collected representative soil samples, and maintained detailed logs of the subsurface soil and groundwater conditions observed. Subsurface conditions were described using the soil classification system shown on Figure 3, in general accordance with ASTM International (ASTM) standard D2488, Standard Practice for Description and Identification of Soils (Visual -Manual Procedures). Summary exploration logs are presented on Figures 4 through 8. Representative soil samples were transported to Landau's geotechnical laboratory for further examination and testing. Natural moisture content determinations were performed on select samples in accordance with ASTM standard test method D2216-19, Standard Test Methods for Laboratory Determination of Water (Moisture) Content of Soil and Rock by Mass. The natural moisture content is shown as "W = xx" (i.e., percentage of dry weight) in the "Test Data" column on Figures 4 through 8. Grain size or sieve analyses were performed on select samples in accordance with ASTM standard test method D6913, Standard Test Methods for Particle -Size Distribution (Gradation) of Soils Using Sieve Analysis. Samples selected for grain size analysis are designated with a "GS" in the "Test Data" column on Figures 4 through 8. The results of the grain size analyses are presented on Figure 9. Soil Conditions The soil observed underlying existing surface conditions (i.e., 3 to 4 inches of topsoil) was categorized into the following unit: Recessional Outwash: Recessional outwash was observed in all test pits and exploration PIT-1 and generally consisted of gray to light brown, sand with varying amounts of silt, gravel, and cobbles to silt with varying amounts of sand, gravel, and cobbles. The recessional outwash was in a loose to medium dense or medium stiff, damp to moist condition. All test pits and exploration PIT-1 were terminated in the recessional outwash unit. landauinc.com Summary of Geotechnical Engineering Services - Mathay-Ballinger Park Project December 27, 2023 Groundwater Conditions Groundwater was not observed in Landau's field explorations. The groundwater conditions reported herein are for the specific date and locations indicated and may not be representative of other locations and/or times. Site groundwater levels will vary depending on local subsurface conditions, weather conditions, and other factors. Groundwater levels will fluctuate seasonally, with maximum levels occurring during late winter and early spring. CONCLUSIONS AND RECOMMENDATIONS Based on the subsurface conditions observed in Landau's explorations, site soils will provide suitable support for the proposed improvements, provided the following recommendations are incorporated into the project design. Seismic Design Considerations Site class D should be used to complete seismic design of the proposed structures (ICC 2017). The site is underlain by unsaturated, loose to medium dense and medium stiff recessional outwash. In Landau's opinion, these soils have a low risk of seismically induced liquefaction and lateral spreading. Given the distance between the site and the nearest known active crustal fault (approximately 2,200 ft to the northwest), there is a low risk of ground rupture due to surface faulting. Foundation Considerations When developing the design parameters in Table 1, Landau assumed that shallow foundations would be established on medium dense or medium stiff recessional outwash, or on imported structural fill that extends to such soils. A qualified geotechnical engineer should evaluate foundation subgrades prior to placement of formwork, rebar, or structural fill. The foundation design parameters in Table 1 should be used in conjunction with the complete recommendations in this memorandum. Table 1. Summary of Design Parameters for Shallow Foundations Allowable soil bearing pressure = 2,000 psf (a) Allowable lateral bearing pressure for pole foundations =100 psf/ftibi Allowable friction coefficient = 0.25 Allowable passive earth pressure = 270 pcf Minimum foundation width = 12 inches (continuous), 18 inches (isolated) (a) Allowable soil bearing pressure for footings established on medium dense or medium stiff recessional outwash or an imported structural fill that extends to such soils. (b) Allowable lateral bearing pressure based on information provided in Table 1806.2 of the 2018International Building Code. pcf = pounds per cubic foot psf = pounds per square foot landauinc.com Summary of Geotechnical Engineering Services - Mathay-Ballinger Park Project December 27, 2023 The allowable soil bearing pressure in Table 1 applies to dead and live loads, exclusive of the weight of the footing and any overlying backfill. The bearing pressure can be increased by one-third for transient loads, such as those induced by wind and seismic forces. For frost protection, Landau recommends that perimeter footings are embedded at least 18 inches below the lowest adjacent grade, where the ground is flat. Interior footings should be embedded at least 12 inches below the nearest adjacent grade. Landau estimates that footings or slabs -on -grade will settle less than 1 inch, if constructed as recommended herein. Similarly loaded foundation elements will likely experience % inch or less of differential settlement over 25-ft spans. Settlement is expected to occur as building loads are applied during construction. An allowable coefficient of sliding resistance of 0.25, applied to vertical dead loads only, can be used to compute frictional resistance acting on the base of concrete shallow foundations. This coefficient includes a factor of safety of 1.5 on the calculated ultimate value. The passive resistance of properly compacted structural fill placed against the sides of concrete foundations can be considered equivalent to a fluid with a density of 270 pounds per cubic foot (pcf). The foundation passive earth pressure has been reduced by a factor of 1.5 to limit deflections to less than 2 percent of the embedded depth. The passive earth pressure and friction components can be combined, provided the passive component does not exceed two-thirds of the total. The upper 1 ft of soil should be excluded from the calculation, unless the foundation perimeter will be covered by concrete or pavement. Landau recommends that perimeter foundation footing drains are included in the design of structures. Landscape and hardscape should slope away from structures at a grade of at least 2 percent. Slabs -On -Grade Concrete slabs -on -grade should be installed on a uniformly firm, unyielding subgrade that consists of medium dense or medium stiff native soils or on imported structural fill that extends to such soils. Prior to slab construction, the exposed subgrade should be compacted to a firm, dense, and unyielding surface. The prepared subgrade should be checked by a qualified geotechnical engineer for any loose and/or disturbed areas. If detected, these areas should be overexcavated. All overexcavated areas should be backfilled to design slab subgrade with properly compacted structural fill according to the recommendations presented below under Construction Considerations. If moisture control within the building is critical, interior slabs -on -grade should include a vapor barrier and a capillary break layer, designed and installed in accordance with industry standards. Pilot Infiltration Test Investigation Landau completed a small-scale PIT investigation (PIT-1) at the approximate location shown on Figure 2. The investigation was completed in general accordance with the requirements in the 2019 Stormwater Management Manual for Western Washington. landauinc.com Summary of Geotechnical Engineering Services - Mathay-Ballinger Park Project December 27, 2023 Correction factors were applied to the in -situ infiltration rate to account for site variability and the number of locations tested (CFv = 0.8), the test method (CFt = 0.5), and the degree of influent control to prevent siltation and bio-buildup (CFm = 0.9). The recommended infiltration rate for use in design of shallow (3 ft or less in depth) infiltration facilities is provided in Table 2. Table 2. Recommended Design Infiltration Rate Using Pilot Infiltration Test Exploration PIT-1 ft = feet in/hr = inches per hour PIT = pilot infiltration test Pavement Design Depth Design Infiltration Rate (ft) (in/hr) 0.19 Asphalt pavement sections for the proposed expanded parking area should be constructed on a compacted subgrade or on structural fill, prepared as recommended herein. Because the expanded parking area will receive limited traffic volume that likely includes limited heavy vehicles, Landau recommends that the pavement section for the expanded parking area conform to the City of Edmonds' standard pavement section for an ally, which is presented in Table 3. Table 3. Recommended Asphalt Pavement Design Section Pavement Section Type Light duty Asphalt Pavement Thickness 2 inches Crushed Surfacing Base Course Thickness 6 inches Subgrade Compacted Native Soils Base course material should be compacted to at least 95 percent of the maximum dry density, determined in accordance with ASTM standard test method D1557, Standard Test Methods for Laboratory Compaction Characteristics of Soil Using Modified Effort (56,000 ft-Ibf/ft3 (2,700 kN-m/m3)). Compacted base and top course should meet the requirements in Section 9-03.9(3) of the Washington State Department of Transportation's 2023 Standard Specifications for Road, Bridge, and Municipal Construction (2023 WSDOTStandard Specifications). Prevention of road -base saturation is essential for pavement durability and efforts should be made to limit the amount of water entering the base and top course. Asphalt concrete should consist of Class B aggregate material or hot -mix asphalt, class % inch and PG58H-22 binder. Asphalt should conform to the requirements in Section 5-04 of the 2023 WSDOT Standard Specifications and should be compacted to at least 91 percent of the Rice density. landauinc.com Summary of Geotechnical Engineering Services - Mathay-Ballinger Park Project December 27, 2023 Retaining Walls If needed, retaining walls with level backslopes can be designed using an equivalent fluid density of 35 pcf for the active condition and 55 pcf for the at -rest condition. For the seismic loading condition, a uniformly distributed lateral pressure of 15H pounds per square foot, where H is the vertical height of the wall in feet, should be added to the static lateral earth pressures for non -restrained (yielding) walls with a level backslope. Lateral resistance parameters are provided in Table 1. When developing design parameters, Landau assumed that the wall would be backfilled with imported structural fill and drainage systems would be provided. The recommended lateral soil pressures do not account for traffic surcharges, the effects of sloping backfill, or hydrostatic pressure. Landau has assumed that the material behind the wall will consist of imported structural fill or undisturbed native soil that extends a horizontal distance equal to the wall height. Drainage systems should be constructed to collect water and prevent buildup of hydrostatic pressure. Landau recommends including a zone of free -draining backfill at the back of the wall. The backfill should meet the requirements for Gravel Backfill for Walls in Section 9-03.12(2) of the 2023 WSDOT Standard Specifications. The free -draining backfill zone should be at least 18 inches wide and should extend from the base of the wall to within 1 ft of the top of the wall. A drainpipe should be placed within the free - draining backfill along the base of the wall and should extend the length of the wall and should be sloped to drain to an approved discharge location. The pipe should be perforated, rigid, and smooth - walled and have a minimum diameter of 4 inches. Site Drainage Site grades should be sloped to drain away from structures and hardscapes. Where grades cannot be sloped, interceptor drains should be installed around the perimeter of structures and hardscapes. If needed, Landau should be asked to review site grading plans and provide recommendations regarding the depth and location of interceptor drains. Uncontrolled flow of stormwater onto slopes should be prevented. Critical Areas The slope along the northern side of Mathay-Ballinger Park (between the Interurban Trail and the Park) is mapped by the City of Edmonds as an erosion hazard area. Based on conversations with the City, it is understood that the City is not planning to perform any work in this area of the site, and as a result, no direct action is needed based on the erosion hazard area determination. Nevertheless, it should be noted that soil within the project area will be subject to erosion if left exposed without the use of appropriate best management practices to limit erosion and sedimentation. A temporary erosion and sediment control plan should be developed for the project and should be implemented and monitored to address potential erosion and siltation during construction. Furthermore, temporarily disturbed areas should be restored as soon as practical to minimize the risk of erosion. If these measures are taken, the landauinc.com Summary of Geotechnical Engineering Services - Mathay-Ballinger Park Project December 27, 2023 potential for the proposed project to cause significant erosion or to increase erosion hazard areas is considered to be low. CONSTRUCTION CONSIDERATIONS The following key points should be reviewed when developing project specifications: • Stripping: Topsoil should be stripped from areas designated for development (i.e., the proposed locations of footings, slabs -on -grade, and pavement sections). Stripped soils are not suitable for reuse as structural fill. Subgrade preparation: Before structural fill, formwork, or pavement base course is placed, the subgrade should be scarified, moisture -conditioned, and compacted to a firm, unyielding condition. The prepared subgrade should be proof -rolled in the presence of a qualified geotechnical engineer who is familiar with the site and can check for soft/disturbed soils. Areas of limited access can be evaluated with a steel T-probe. If probing or proof -rolling reveals loose and/or disturbed subgrades, additional moisture -conditioning and compaction should be completed to produce a firm, unyielding condition. Alternatively, unsuitable soils can be overexcavated and replaced with compacted structural fill. Utility trench excavation and backfill: If needed, utility trenches will likely be excavated in loose to medium dense or medium stiff recessional outwash. A heavy-duty hydraulic excavator should be able to reach trench depths of 5 to 8 ft bgs. A smooth -bladed bucket should be used to remove loose and/or disturbed soil from the trench bottom. The final trench bottom should be firm and free of roots, topsoil, lumps of silt and clay, construction debris, and organic and inorganic debris. • Oversized material: Cobbles and boulders are often present in glacially derived soils. The contractor should be prepared to manage such oversized material. • Site soil: The site soils are moisture sensitive and suitable for reuse only in the summer. Even then, moisture conditioning (wetting or drying) may be required. Earthwork should be avoided during heavy and/or extended periods of precipitation. • Imported structural fill: Gravel Borrow, as described in Section 9-03.14(1) of the 2023 WSDOT Standard Specifications, is a suitable source of imported structural fill. During periods of wet weather, the fines content should not exceed 5 percent, based on the minus %-inch fraction. • Fill placement and compaction: Structural fill should be placed on an approved subgrade that consists of uniformly firm, unyielding soil or of compacted structural fill that extends to such soil. Structural fill should be placed and compacted in accordance with the requirements in Section 2-03.3(14)C, Method C of the 2023 WSDOTStandard Specifications. Method A is appropriate for non-structural areas, such as landscaping. Each layer of structural fill should be compacted to at least 95 percent of the maximum dry density, determined in accordance with the compaction control tests in Section 2-03.3(14)D of the 2023 WSDOTStandard Specifications. Alternatively, the maximum dry density can be determined using ASTM standard test method D1557, Standard Test Methods for Laboratory Compaction Characteristics of Soil Using Modified Effort (56,000 ft-Ibf/ft3 (2,700 kN-m/m3)). Temporary construction dewatering: Temporary excavations should be dewatered to allow construction to be completed in the dry. Groundwater was not observed in Landau's field landauinc.com Summary of Geotechnical Engineering Services - Mathay-Ballinger Park Project December 27, 2023 explorations. Where shallow groundwater seepage is encountered, the use of conventional sumps and pumps should be sufficient to dewater excavations. The contractor should be responsible for the design, monitoring, and maintenance of any dewatering systems. Temporary slopes: Temporary excavations should be completed in accordance with the requirements in Section 2-09 of the 2023 WSDOTStandard Specifications. All applicable local, state, and federal safety codes should be followed. The contractor should be responsible for actual excavation configurations and the maintenance of safe working conditions, including temporary excavation stability. Temporary excavations in excess of 4 ft should be shored or sloped in accordance with the requirements outlined in Safety Standards for Construction Work, Part N (Washington Administrative Code Chapter 296-155). The soil likely to be exposed in the excavations should be considered Type C, with a maximum allowable excavation inclination of 1% horizontal to 1 vertical (1%1-1:1V). If groundwater seepage is present, flatter slopes, temporary shoring, and/or dewatering may be required. CONSTRUCTION MONITORING Monitoring, testing, and consultation should be provided during construction to confirm that site conditions are consistent with those observed in Landau's explorations and to provide expedient recommendations should conditions differ from those anticipated. Monitoring will also allow Landau to evaluate construction activities for compliance with the project plans and specifications and the recommendations herein. Construction activities may include evaluation of fill material, compaction testing of structural fill, and preparation of structural foundation subgrades. Landau would be pleased to provide construction monitoring services. USE OF THIS TECHNICAL MEMORANDUM Landau Associates, Inc. has prepared this technical memorandum for the exclusive use of the City of Edmonds Parks, Recreation & Human Services Department for specific application to the Mathay- Ballinger Park Project in Edmonds, Washington. No other party is entitled to rely on the information, conclusions, and recommendations included in this document without the express written consent of Landau. Reuse of the information, conclusions, and recommendations provided herein for extensions of the project or for any other project, without review and authorization by Landau, shall be at the user's sole risk. Landau warrants that, within the limitations of scope, schedule, and budget, its services have been provided in a manner consistent with that level of skill and care ordinarily exercised by members of the profession currently practicing in the same locality and under similar conditions. Landau makes no other warranty, either express or implied. landauinc.com Summary of Geotechnical Engineering Services - Mathay-Ballinger Park Project December 27, 2023 CLOSING We trust that this memorandum provides you with the information needed to proceed with the project. if you have questions or comments, or if we can be of further service, please contact Steven Wright at 425-329-0290 or at swright@landauinc.com. LANDAU ASSOCIATES, INC. �CtiV RWR��I Steven R. Wright, PE O ���► Principal ,3± .�G�, SC/SZW/tmh (P:\074\217.010\R\MATHAY BALDNGER TECHNICAL MEMORANDUM 5.23.2023.DOCX] Attachments: Figure 1. Vicinity Map Figure 2. Site and Exploration Location Plan Figure 3. Soil Classification System and Key Figures 4-8. Logs of Test Pits TP-1 through TP-4 and PIT-1 Figures 9. Grain Size Distribution Attachment 1. Concept Design REFERENCES ,7.1z�i2 ASTM. 2017. Annual Book of ASTM Standards. In: Soil and Rock (I). West Conshohocken, PA: ASTM International. Ecology, 2019. Stormwater Management Manual for Western Washington, Washington State Department of Ecology. July. ICC. 2017. 2018 International Building Code. International Code Council. August 31. Minard, J. P. 1983. Geologic Map of the Edmonds East and Part of the Edmonds West Quadrangles, Washington. Department of the Interior United States Geological Survey, WSDOT. 2022. M41-10: Standard Specifications for Road, Bridge, and Municipal Construction. 2023 Edition. Washington State Department of Transportation. September 14. 9 landauinc corn 10 �9p e NW 205thc"- N 205th St z a, a L /Vw.P00 4 5�> Ii O OyBeach Rd N Rich �Orla BOO a °h Ra c Rich 3 n Higr z C 220th St 1 244th St SW Echo Lake N 185th St —"— 0 0.5 1 Miles Data Source: Esri. Mathay Ballinger Park LALANDASU Edmonds, Washington Lake Ballinger NE pia FA Hall Lake St 3 a a z NF Project Location Spokane 40 Vicinity Map Figure 1 Y '4'r , 240th -=. 4� S- own _ a s ' 0 3 IL Oyu i - � • �� =Y � ','� ^ NY Legend Note M. PIT-1 ® Pilot Infiltration Test Location and Designation 1. Black and white reproduction of this color L TP-1 Test Pit Location and Designation original may reduce its effectiveness and lead to incorrect interpretation. ti N v' 0 100 200 r O 2 Data Source: Snohomish County GIS. Scale in Feet d Mathay Ballinger Park Figure LALANDAU Edmonds, Washington Site and Exploration Plan 2 A S S 0 C I A T E 5 MAJOR DIVISIONS Soil Classification System uscs GRAPHIC LETTER SYMBOL SYMBOL"' TYPICAL DESCRIPTIONS tz"3> GRAVEL AND CLEAN GRAVEL p:�.. j.:p: GW Well -graded gravel; gravel/sand mixture(s); little or no fines 0 @ w GRAVELLY SOIL (Little or no fines) Poorly graded gravel; gravel/sand mixture(s); little or no fines o: o. Q ,p ,o . GP 0 @� (More than Silty gravel; gravel/sand/siltmixture(s) GRAVEL WITH FINES GM w E'w coarse fraction retained (Appreciable amount of Qo N on No. 4 sieve) fines) GC Clayey gravel; gravelfsand/clay mixture(s) 0 LO z° SAND AND CLEAN SAND $W Well -graded sand; gravelly sand; little or no fines ui m c U) t r SANDY SOIL (Little or no fines) Poorly graded sand; gravelly sand; little or no fines SP Q oo O0 (More than 50%of fraction Silty sand; sand/siltmixture(s) SAND WITH FINES SM coarse passed (Appreciable amount of $C through No. 4 sieve) fines) Clayey sand; sand/clay mixture(s) ML Inorganic silt and very fine sand; rock flour; silty or clayey fine p r SILT AND CLAY sand or clayey silt withlow plasticity CL U) o - N Inorganic clay of low to medium plasticity; gravelly clay; sandy ov'v m (Liquid limit less than 50) clay; silty clay; lean clay OL Z @ w o Organic silt; organic, silty clay of low plasticity MH Inorganic silt; micaceous or diatomaceous fine sand; elastic silt a N o'er SILT AND CLAY uJ �,z° CH Inorganic clay of high plasticity; fat clay Z E LL (Liquid limit greater than 50) Organic clay of medium to high plasticity; organic silt OH HIGHLY ORGANIC SOIL PT Peat; humus; swamp soil with high organic content GRAPHIC LETTER OTHER MATERIALS SYMBOL SYMBOL TYPICAL DESCRIPTIONS PAVEMENT • :. AC Or PC Asphalt concrete pavement or Portland cement pavement ROCK RK Rock (See Rock Classification) WOOD WD Wood, lumber, wood chips DEBRIS O O O DB Construction debris, garbage Notes: 1. USCS letter symbols correspond to symbols used by the Unified Soil Classification System and ASTM classification methods. Dual letter symbols (e.g., SP-SM for sand or gravel) indicate soil with an estimated 5-15% fines. Multiple letter symbols (e.g., MUCL) indicate borderline or multiple soil classifications. 2. Soil descriptions are based on the general approach presented in the Standard Practice for Description and Identification of Soils (Visual -Manual Procedure), outlined in ASTM D 2488. Where laboratory index testing has been conducted, soil classifications are based on the Standard Test Method for Classification of Soils for Engineering Purposes, as outlined in ASTM D 2487. 3. Soil description terminology is based on visual estimates (in the absence of laboratory test data) of the percentages of each soil type and is defined as follows: Primary Constituent: > 50% - "GRAVEL," "SAND," "SILT," "CLAY," etc. Secondary Constituents: > 30% and < 50% -'very gravelly," 'very sandy," 'very silty," etc. > 15% and < 30% - "gravelly," "sandy," "silty," etc. Additional Constituents: > 5% and <_ 15% - "with gravel," "with sand," "with silt," etc. < 5% - "with trace gravel," "with trace sand," "with trace silt," etc., or not noted. 4. Soil density or consistency descriptions are based on judgement using a combination of sampler penetration blow counts, drilling or excavating conditions, field tests, and laboratory tests, as appropriate. Drilling and Sampling Key SAMPLER TYPE & METHOD SAMPLE NUMBER & INTERVAL Field and Lab Test Data Code WOR Description Weight of Rod Graphic Code Description Sample Identification Number ® a 3.25-in OD, 2.42-in ID Split Spoon WOH Weight of Hammer ® b 2.00-in OD, 1.50-in ID Split Spoon Sampler Graphic (variable) PP = 1.0 Pocket Penetrometer, tsf m c Thin -Wall Sampler (aka Shelby Tube) TV = 0.5 Torvane, tsf ® d Grab Sample Recovery Depth Interval PID = 100 Photoionization Detector VOC screening, ppm 0 e Single -Tube Core Barrel W = 10 to Moisture Content, El f Double -Tube Core Barrel 1 1� Sample Depth Interval D = 120 Dry Density, ® g 2.50-in OD, 2.00-in ID WSDOT Jpcf ® h 3.00-in OD, 2.37-in ID Mod. Calif. Portion of Sample Retained -200 = 60 Material smaller than No. 200 sieve, % ® i Other - See text if applicable for Archive or Analysis GS Grain Size - See separate figure for data 1 300-lb Hammer, 30-inch Drop Groundwater AL Atterberg Limits - See separate figure for data 2 140-lb Hammer, 30-inch Drop UU Triaxial Unconsolidated Undrained (UU) Strength 3 Direct Push V Approximate water level at time of Cu Triaxial Consolidated Undrained (CU) Strength 4 Vibrocore - drilling (ATD) Consol 1-D Consolidation Test 5 Other - See text if applicable Approximate water level at time after Perm Permeability Test 6 Piston Extraction - drilling/excavation/well CA Chemical Analysis I LANDAU Mathay-Ballinger Park Soil Classification Figure Edmonds, Washington System and Key 3 A S S O C I A T E S z s a 0 14 PIT-1 SAMPLE DATA SOIL PROFILE � Excavation Method: Tracked Excavator o z ca a cn 9 E Ground Elevation (ft): Not Measured .m -am Q o U) Excavated By: NW Excavating and Trucking, Inc. w in a 12 65 Logged By: SC rn 0s c� SP- Brown, fine to coarse, SAND with gravel, silt, SM and root organics (loose, damp) SM (TOPSOIL) Light brown, silty SAND with gravel and root S-1 = d W = 30 organics (loose, damp) (RECESSIONAL OUTWASH) S-2 = d WGS 1 ML -T Brown -gray, SILT with gravel, trace cobbles, and mottling (medium stiff, damp) Infiltration test depth S-3 = I d S-4 JW I d I FFFFS-M Gray, silty, very gravelly, SAND with cobbles (medium dense, damp) Test Pit Completed 05/24/23 Total Depth of Test Pit = 10.5 ft. GROUNDWATER Groundwater Not Observed Notes: 1. Stratigraphic contacts are based on field interpretations and are approximate. q 2. Reference to the text of this report is necessary for a proper understanding of subsurface conditions. 3. Refer to "Soil Classification System and Key" figure for explanation of graphics and symbols. N 7 n Figure LALANDAU Mathay-Ballinger Park Log of Test Pit PIT-1 Edmonds, Washington 9 4 A S S O C I A T E S z s a 0 12 TP-1 SAMPLE DATA SOIL PROFILE GROUNDWATER � Excavation Method: Tracked Excavator o z ca a cn 9 E Ground Elevation (ft): Not Measured .m -am Q o U) Excavated By: NW Excavating and Trucking, Inc. w in a 12 65 Logged By: SC rn 0s c� SP- Brown, fine to coarse, SAND with gravel, silt, SM f and root organics (loose, damp) SM (TOPSOIL) Brown, silty SAND with gravel, and root organics (loose, damp) (RECESSIONAL OUTWASH) S-1 = d W = 21 ML Browmgray, SILT with gravel, trace cobbles, Groundwater Not Observed and mottling (medium stiff, damp) S-2 = d W = 10 GS S-3 = d S-4 = d Test Pit Completed 05/24/23 Total Depth of Test Pit = 9.5 ft. --------------------- Light brown, gravelly, very silty, SAND with cobbles (medium dense, damp) -grades to gray, silty, and very gravelly Notes: 1. Stratigraphic contacts are based on field interpretations and are approximate. 0 2. Reference to the text of this report is necessary for a proper understanding of subsurface conditions. 3. Refer to "Soil Classification System and Key" figure for explanation of graphics and symbols. N 7 n Figure LALANDAU Mathay-Ballinger Park Log of Test Pit TP-1 Edmonds, Washington 9 A S S O C I A T E S N 14 TP-2 SAMPLE DATA SOIL PROFILE Excavation Method: Tracked Excavator z m a @ to -0 �, Ground Elevation (ft): Not Measured Q Q o r U) Excavated By: NW Excavating and Trucking, Inc. m e m iv CL m U) Logged By: SC w cn 05 cn 1-- (0 D SP- Brown, fine to coarse, SAND with gravel, silt, SM and root organics (loose, damp) (TOPSOIL) SM Brown, silty SAND with trace gravel, root organics, and mottling (loose, damp) S-1 I d = W 21 (RECESSIONAL OLITWASH) S-2= d ML Brown -gray, SILT with gravel, trace cobbles, and mottling (medium stiff, damp) ----------------------- S-3 = d SM Gray, silty SAND with gravel and cobbles (medium dense, moist) S-4 = d GS4 -grades to very gravelly, with trace cobbles, mottling, and medium dense to dense Test Pit Completed 05/24/23 Total Depth of Test Pit = 9.0 ft. GROUNDWATER Groundwater Not Observed Notes: 1. Stratigraphic contacts are based on field interpretations and are approximate. 0 2. Reference to the text of this report is necessary for a proper understanding of subsurface conditions. 3. Refer to "Soil Classification System and Key" figure for explanation of graphics and symbols. N athay 7 r Figure LALANDAU M Edmonds, Ballinger Park Log of Test Pit TP-2 Edmonds, Washington A S S O C I A T E S N SAMPLE DATA _ � m E C- z m � 0 o Z aD > E c E m w (n 05 in S-1I d S-2 I d W = 24 GS _' 10 S-3 T I d a Test Pit Completed 05/24/23 0 Total Depth of Test Pit = 10.3 ft. 0 0 12 TP-3 SOIL PROFILE o Tracked Excavator Excavation Method: E (o -0 >, Ground Elevation (ft): Not Measured r (Un Excavated By: NW Excavating and Trucking, Inc. 12 U) Logged By: SC (2 SP- SM Brown, fine to coarse, SAND with gravel, silt, and root organics (loose, damp) SM (TOPSOIL) Brown, silty SAND with gravel, organics, and mottling (loose, damp) (RECESSIONAL OUTWASH) --------------------- Light gray, sandy SILT with mottling (medium stiff, damp) -grades to gray and moist GROUNDWATER Groundwater Not Observed Notes: 1. Stratigraphic contacts are based on field interpretations and are approximate. 0 2. Reference to the text of this report is necessary for a proper understanding of subsurface conditions. 3. Refer to "Soil Classification System and Key" figure for explanation of graphics and symbols. N 7 athay r Figure LALANDAU M Edmonds, Ballinger Park Log of Test Pit TP-3 Edmonds, Washington / A S S O C I A T E S N TP-4 SAMPLE DATA SOIL PROFILE Excavation Method: Tracked Excavator z m a @ to -0 �, Ground Elevation (ft): Not Measured Q Q o r U) Excavated By: NW Excavating and Trucking, Inc. M c m iv CL m U) Logged By: SC w cn 05 cn 1-- (0 D SP- Brown, fine to coarse, SAND with gravel, silt, SM and root organics (loose, damp) SM (TOPSOIL) Light brown, silty SAND with gravel, tree roots, and trace cobbles (loose, damp) S-1I d = W 16 (RECESSIONAL OUTWASH) S-2I d ML Brown -gray, SILT with gravel, trace cobbles, and mottling (medium stiff, damp) S-3 = d SM Gray, silty, very gravelly, SAND with trace cobbles (medium dense, damp) Test Pit Completed 05/24/23 Total Depth of Test Pit = 10.0 ft. Notes: 1. Stratigraphic contacts are based on field interpretations and are approximate. 2. Reference to the text of this report is necessary for a proper understanding of subsurface conditions. 3. Refer to "Soil Classification System and Key" figure for explanation of graphics and symbols. GROUNDWATER Groundwater Not Observed � Figure LALANDAU M Edmonds, Ballinger Park Log of Test Pit TP-4 Q Edmonds, Washington v A S S O C I A T E S 74217.01 6/23/23 P:\074\217.010\T\GINT\074217.010.011 MATHAY BALLINGER PARK.GPJ GRAIN SIZE FIGURE 100 U.S. Sieve Opening in Inches 6 4 3 2 1.5 1 1/2 3/8 3 j U.S. Sieve Numbers 6 810 1416 20 30 40 5060 100 140 200 Hydrometer 90 80 70 L m a 60 c ii 50 c a 40 30 20 10 0 100 10 1 0.1 0.01 0.001 Grain Size in Millimeters LANDAUEdmonds, A S S O C I A T E S MathaLAy-Bal linger Park Washington Grain Size Distribution Figure Q J Cobbles Gravel Sand Silt or Clay Coarse Fine Coarse Medium Fine Symbol Exploration Number Sample Number Depth (ft) Natural0 Moisture (/o) Soil Description Unified Soil Classification • PIT-1 S-2 2.3 31 SILT ML m TP-1 S-2 3.8 10 Gravelly, very silty, fine to coarse SAND SM A TP-2 S-4 8.3 4 Silty, very gravelly, fine to coarse SAND SM * TP-3 S-2 3.4 24 Sandy, SILT ML ATTACHMENT 1 Concept Design 79th PL W I - S"J) • � i V m rn = z rn D c,-, m N z v, D z -p GZoo D D D n D l D > m rr— m cn r 4 (Y) D m N � _ O r J mm ;D 70 r � D� z ;o pr, 78th PL W } D D CD 77th PL W ell PON �.r ml y J I• � : +T '�[ a toy 79th PL W i I , 0 eA s LA F+ LA 0 O D D rn (n N D a �2 �F ,92 I�o �Q 70 Cn 'p m _ o Ln O D 77th PL W m m n N :;o C: z rn 2 D �o w D Ln o D Ln m O N o Q- C, tug n to Z m � N - z rn> z � � YJ m m r � 11CIi�, �v 78th PL W mP i fl! i i 1 � Ln z -0 � C m = D 70 CC r T C V) D Lr, m n O N m m r 0 O _J i r; SE 1 /4, SE 1 /4, SECTION 31, TOWNSH P 27 NORTH, RANGE 4 EAST, W.M. IoaPTRAIL ilINCHLS 1 SPADA SOFT SURFACE TRAIL / •� ��� F ) l 1 �1��`TR[f fO fY RCMOV[0 - _ / (TI k(w $741S L R REM'M [ r7�M' -- 7 RCSTROOM /• IT.. 111ES. IYP / `SOf T WRF WA TwL 7- Al. I [rL6.l ' rots, r j_z L'='71 ti. WP p I � 1 k Wo a' [ on"".) wm7A) (� of xwc) wm=' f Ja=T-, JPSATM 242ND ST. S. W. ff( i I t r / � 1ESUR IAC[ SPDRT COURT E16f PAIN PICNIC SNEl,E1 _�.,,., �ia7p 0f0 C% MET:;^ I'y�RfSVRFAC[SPORT G➢VR[' 1 SITE PLAN SGLL ,• • w w a » a w CONS711FCigk.WSE 1L.. _....,.. _.. � •PEASE [ 1 $ PNAS[ 2 PAVING LEGEND N[W ASPHALTILMLTY UNCUT OVL RIAT f itSTNU ASPHALT NEW CONCRETE PERMEAFILE PAVEMENT AUl01NG HATCH fT SURFACES C e r2[NEERM 250 {TH AVE. S.. SUITE 200 CDL[Ok02. WASNINOT01) 0=0 PWME (425) 77R-RS00 TAX (425) 775-nM DESir" CAG DqA-1 ATO c. CAG JO 23072.001 o xx/xx/xx .z W W 0 Qom' [1. Y ~ W a 3 to N 0:U W Q W 0 J QI Z a Q mDoo3 ^0 CL Z m Q 0 ILL] M N W (/) =�EE7 Mathay Ballinger Park— CG # 23072.20 Drainage Report May 3, 2024 Section VI, Page 1 Section VI — Other Permits Section VI Summary: Narrative Other permits are not anticipated to be required for this project besides those from the City of Edmonds. 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Mathay Ballinger Park— CG # 23072.20 May 3, 2024 Drainage Report Section VII, Page 1 Section VII — Bond Quantities, Declaration of Covenant, & Operation and Maintenance Manual Section VII Summary: Narrative The Bond Quantity Worksheet is a standalone document that can also be submitted to the City of Edmonds separately from this document. A Declaration of Covenant for the on -site BMPs proposed is provided. The Operation and Maintenance Manual is a standalone document that will be given to the owner following the construction of the project. Narrative The following maintenance manual is for the Mathay Ballinger Park project. The contractor will be responsible for the maintenance and operation of all stormwater structures and BMPs requiring maintenance during construction, and, after construction, responsibility will pass to the building owner. The project contractor will be responsible for passing along the information in this maintenance manual to the owner. Upon request by the City, it shall be made available for their inspection. It is generally expected that few to none of these defects will be present upon the yearly inspection of each facility. 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com After recording return to: City Clerk City of Edmonds 121 Fifth Avenue North Edmonds, WA 98020 Document Title(s) Declaration of Covenant - Private Stormwater BMP Reference Number(s) of Related Documents City of Edmonds (BLD2023-1127) Grantor(s) (Last, First and Middle Initial) EDMONDS PARKS, RECREATION & HUMAN SERVICES Grantee: City of Edmonds Legal Description (abbreviated form; i.e., lot, plat or section, township, range, quarter/quarter) For 27043100402800 - SE 1/4 OF THE SE 1/4 OF SECTION 31, TOWNSHIP 27 NORTH, RANGE 5 EAST, For 00488700100100 - LOT 1 OF LAKE BALLINGER HOMESITES ADDITION, ACCORDING TO THE PLAT THEREOF RECORDED IN VOLUME 14 OF PLATS, PAGE 99, IN SNOHOMISH COUNTY, WASHINGTON. Assessor's Property Tax Parcel/Account Number at the Time of Recording: 27043100402800 00488700100100 The Auditor/Recorder will rely on the information provided on this form. The staff will not read the document to verify the accuracy or completeness of the indexing information provided herein. DECLARATION OF COVENANT Private Stormwater BMP WHEREAS, the undersigned Declarant(s) have installed one or more stormwater facilities under Edmonds Community Development Code (ECDC) Chapter 18.30 known as "stormwater best management practices (BMP)" as selected below: ❑ Permeable Pavement ® Infiltration Trench/Gallery/Drywell ❑ Detention Pipe/Tank/Vault ❑ Concentrated Flow Dispersion ❑ Other: ❑ Infiltration Tank/Vault ❑ Sheet Flow Dispersion ❑ Reduced Impervious Footprint ❑ Rain Garden / Bioretention Cell WHEREAS, the City of Edmonds has allowed installation of the BMP, subject to the execution and recording of this Declaration of Covenant; NOW, THEREFORE, THE UNDERSIGNED DECLARANT(S), being the owners of the real property ("the Property") located at the following address: in the City of Edmonds, Washington, and legally described on Exhibit A attached hereto and incorporated herein by this reference as if set forth in full, hereby covenants and agrees, on behalf of himself/herself/themselves/itself and his/her/their/its successors and assigns, as follows: 1. Declarant(s) warrant that he/she/they/it is/are the owner(s) of the property described on Exhibit A and have the authority to impose this covenant on the property and bind all future owners, successors, and assigns of the Declarant(s). The Declarant(s), future owners, successors, and assigns of the Declarant(s) shall be referred to collectively as "Owners." 2. The Owners of the Property agree that the Property contains one or more stormwater management facilities referred to as a 'BMP," which was installed to mitigate the stormwater quantity and quality impacts of some or all of the impervious or non-native pervious surfaces on the property. a. For infiltration -based BMPs, the BMP shall include all pretreatment devices upstream, the infiltration facility, and a minimum of 3-feet of soil beneath the infiltration contact layer, defined as the elevation at which runoff enters native soils. b. For bio-retention or rain garden BMPs, the BMP shall include all pretreatment devices upstream, the retention facility, the vegetation within the retention facility, and a minimum of 3-feet of soil beneath the infiltration contact layer, defined as the elevation at which runoff enters native soils. While specific plants are not necessarily required, a quantitative amount of vegetation coverage is required and may be subject to maintenance requests per Section 5. c. For dispersion based BMPs, the BMP shall include all pretreatment devices upstream, the dispersion mechanism/device, and all elements of the downstream vegetated flow path, including restrictions on slopes and surface materials, as required by ECDC 18.30. d. For detention BMPs, the BMP shall include all pretreatment devices upstream, the detention device, and the control structure device. e. For reduced impervious footprints, the BMP shall include all areas which are used as mitigation credits, including a full ten foot (10') driveway width when using wheel strip driveways. 3. The Owners shall maintain the size, placement, and design of the BMP as depicted on the approved site plan, Exhibit B, attached hereto and incorporated herein by this reference as if set forth in full, and design details shall be maintained and may not be changed without written approval either from the Engineering Division of the City of Edmonds or through a future development permit from the City of Edmonds. Chemical fertilizers and pesticides shall not be used where a BMP is located. All costs of maintenance and repair shall be the sole responsibility of the Owners. 4. The Owners shall inspect BMPs annually for physical defects. After major storm events, the system shall also be checked to ensure that the overflow system is working properly. The Owners also shall maintain all BMPs so they function as designed on a year-round basis. 5. The City of Edmonds is hereby granted by the Owners the right, but not the obligation, to enter upon the Property described on Exhibit A at all reasonable times for the purpose of inspecting the private stormwater BMP facility. If, as the result of any such inspection, the City of Edmonds determines that the BMP is in disrepair, requires maintenance or repair, or is otherwise not functioning as provided in the site plan, the City Engineer or his designee shall have the right, but not the obligation, to order the Owners to maintain or repair the same. The Owners agree to maintain reasonable one-man access to all portions of the BMP and shall avoid permanent or lockable obstructions from blocking a reasonable path of access by City inspectors. Such obstruction may be the sole cause for the City to request maintenance as noted above. 6. If the City of Edmonds determines that the BMP requires maintenance or repair pursuant to Section 5, the City of Edmonds shall provide notice to the Owners of the deadline within which such maintenance or repair must be completed. Said notice may further advise that, should the Owners fail to perform required maintenance or make repairs within the established deadline, the work may be done by the City or a contractor designated by the City Engineer and the expense thereof shall be charged to the Owners. The City's officers, agents, employees, and contractors shall have the right, which is hereby granted by the Owners, to enter upon the Property described on Exhibit A in order to perform such work. The Owners shall bear the cost of all work performed. 7. The Owners shall indemnify, defend and hold harmless the City of Edmonds, its officers, officials, employees and agents from any and all claims, demands, suits, penalties, losses, 8. Dated: damages, judgments, attorneys' fees and/or costs of any kind whatsoever, arising out of or in any way resulting from the approval of the BMP(s), the installation and presence of the BMP(s), and the acts or omissions of the Owners, their officers, employees, contractors, and agents relating to the construction, operation and maintenance of the BMP(s) on the Property, except for the City's intentional and willful tortious acts, and waive and release the City of Edmonds from any and all claims for damages and injunctive relief which the Owners may themselves have now or in the future, by reason of the construction, maintenance and operation of said BMP(s). This covenant shall run with the land and be binding upon the Owners. DECLARANT(S): (Signature) (Print Name) (Signature) (Print Name) State of Washington M County of Snohomish APPROVED: CITY OF EDMONDS (Signature) (Print Name) (Title) On this day personally appeared before me {Declarant(s)I to me known to be the individual, or individuals described in and who executed the within and foregoing instrument, and acknowledged that he/she/they/it signed the same as his/her/their/its free and voluntary act and deed, for the uses and purposes therein mentioned. SUBSCRIBED AND SWORN before me this day of (Signature) 20 . (Name legibly printed or stamped) Notary Public in and for the State of Washington. Residing at: My commission expires Exhibit A Legal description 27043100402800- ALL THAT PORTION OF THE SOUTHEAST QUARTER OF THE SOUTHEAST QUARTER OF SECTION 31, TOWNSHIP 27 NORTH, RANGE 5 EAST, W.M. DESCRIBED AS FOLLOWS: ALL THAT PORTION OF THE NORTHWESTERLY 40 FEET OF THE 100 FOOT SEATTLE AND EVERETT INTERURBAN RAILWAY AS DEPICTED ON THE FACE OF THE PLAT OF MCALEER FIVE ACRE TRACTS ACCORDING TO THE PLAT THEREOF RECORDED IN VOLUME 5 OF PLATS, PAGE 48, RECORDS OF SNOHOMISH COUNTY WASHINGTON, LYING NORTHEASTERLY OF THE EAST LINE OF 78TH PLACE WEST EXTENDING NORTHERLY. SITUTATE IN THE COUNTY OF SNOHOMISH, STATE OF WASHINGTON. 00488700100100- LOT 1 OF LAKE BALLINGER HOMESITES ADDITION, ACCORDING TO THE PLAT THEREOF RECORDED IN VOLUME 14 OF PLATS, PAGE 99, IN SNOHOMISH COUNTY, WASHINGTON. SITUATE IN THE COUNTY OF SNOHOMISH, STATE OF WASHINGTON. Mathay Ballinger Park— CG # 23072.20 Drainage Report May 3, 2024 Section VI I, Page 2 Mathay Ballinger Park 24100 78TH PL W, Edmonds, WA 98026 OPERATION AND MAINTENANCE MANUAL Date: May 2024 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Mathay Ballinger Park— CG # 23072.20 May 3, 2024 Drainage Report Section VII, Page 3 Operation and Maintenance Manual This Operation and Maintenance Manual has been created for Mathay Ballinger Park, a site improvement project on a 2.19 ac lot. The proposed storm system consists of infiltration trenches that overflow to existing storm infrastructure. Included in this Operation and Maintenance Manual is an 11" x 17" Grading and Drainage Plan sheet showing the location of the system. Please note that this map is generated during the design phase and may not reflect all changes made in permitting and construction. CG Engineering may be contacted for an updated copy of this map once the as -built drawings are completed for the site. The contractor will be responsible for the maintenance and operation of all stormwater structures and BMPs requiring maintenance during construction, and, after construction, responsibility will pass to the owner. A map of the project area can be seen on the following page in Figure VII-1. Included in this manual are maintenance sheets taken from the 2019 Stormwater Management Manual for Western Washington for the following facilities/activities: Catch Basins: Concrete structures with steel grates that collect stormwater runoff from the site and act as junctions for storm conveyance pipes. Infiltration Trenches: Gravel trenches to infiltrate stormwater on -site. Vegetation Management: Landscaping can include grading, soil transfer, vegetation removal, pesticide and fertilizer applications, and watering. Stormwater contaminants include toxic organic compounds, heavy metals, oils, total suspended solids, coliform bacteria, fertilizers, and pesticides. Facilities shall be inspected for defects listed in the following facility sheets. Most maintenance tasks are generally reactionary to a defect being found, rather than a matter of constant upkeep. It is generally expected that few to none of these defects will be present upon the yearly inspection of each facility. The facility sheets list the potential conditions warranting maintenance and the expected result following any maintenance. Several engineer's notes for specific tasks are provided within the facility sheets. Unless otherwise noted on the facility sheets the maintenance tasks should be performed on an "as needed" basis: (a) when the described defect is visible to whomever performs the yearly inspection, or (b) should any defect become apparent between inspections. 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Mathay Ballinger Park— CG # 23072.20 May 3, 2024 Drainage Report Section VI I, Page 4 •%'wrXLl�3i� via f�+� P rT f •T r Figure VII-1. Map of project area (Google Maps). 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com Mathay Ballinger Park— CG # 23072.20 Drainage Report May 3, 2024 Section VII, Page 5 SAMPLE ACTIVITY LOG DATE FACILITY MAINTENANCE PERFORMED RESULTS / NOTES 4M 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com CB RIM=327.80 IE 12" CPP(NE)-324.6 IE 12" PVC(SW)=324.6 / SE 1 /4, SE 1 /4, SECTION 31, TOWNSHIP 27 NORTH, RANGE 4 EAST, W.M. CB RIM=3376 \ / 3�6.80 /' /'�J i26" 26" 12» F IE 12" RCP(NW)-335.86 1 7.24 /' i F 1 F F M n-- IE 1�" RCP(SE=335.76 8„ / \ 22" / F CB RIM=33671 -_ 1 �v / V6" F / / IE 12'%-O NW)=328.88 i �/ ;� F F 14"x2 IE /12/" CPP(SW)=328.88 ' EXIST CB /' /' 26" / RIM: 330.71 F , IE328.88, -3 / / 34" IE (12328.88' / 32"'1 / JBRING TO GRADE W/ RISERS, `\ ,' 1 M INST/kLLSOLID LID ONEXISTING CB F / 11 26»� ly / 42" 1 �•/4/ GRADING AND UTILITY PLAN NOTES 1. SOILS REPORT REPORT NUMBER: 074217.010 PREPARED BY: LANDAU ASSOCIATES DATED: 23 JUNE 2023 2. AMINI MUM OF 3' HORIZONTAL SEPARATION AND VVERTICAL SEPARATION IS REQUIRED BETWEEN DRY UTILITIES (POWER, GAS, PHONE, CABLE, ETC) AND SEWER, WATER AND STORM, AND A MINIMUM OF 5' HORIZONTAL SEPARATION AND 1' VERTICAL SEPARATION FROM ANY CITY -OWNED LINES. 3. ALL DISTURBED AREAS TO BE COMPOST AMENDED PER 2019 SWMMWW BMP T5.13. SEE DETAIL 6/C3.2. 4. A TYPE II MANHOLE IS REQUIRED WHENEVER RIM TO INVERT EXCEEDS 5'. 5. A MINIMUM OF 2' OF COVER IS REQUIRED FOR ALL PIPES LOCATED UNDER DRIVABLE SURFACES AND 1' OF COVER UNDER LANDSCAPE AND OTHER HARD SURFACES. 6. TOTAL NEW REPLACED HARD SURFACES: 9,422 SF. - NEW ASPHALT PAVEMENT: 8,716 SF. 5,436 SF PORTION ROUTED TO INFILTRATION #1, 825 SF PORTION ROUTED TO INFILTRATION TRENCH #2, REMAINING 2,455 SF BYPASSES INFILTRATION TRENCHES. EQUIVALENT -2,500 SF OF EXISTING ASPHALT ROUTED TO INFILTRATION TRENCH #2. - NEW ROOF: 190 SF. RUNOFF ROUTED TO INFILTRATION TRENCH #2. NEW CONCRETE PAVEMENT: 516 SF. 445 SF PORTION ROUTED TO INFILTRATION #1, i SF PORTION ROUTED TO INFILTRATION TRENCH #2. A R�A GRILL \\y 26"1 1 SHED GATE ./ \ SH� POSE /� / /' /' BIKE /k 95,481 SF \33, F i2� GRADING QUANTITIES �� RACK / /'50» is / q ,' - TOTAL EXCAVATION I00 CUVDSTOTAL �?Pp 27043100402 V'lL �\ \ � - EMBANKMENTIFILLI- 340 CU YD5 Z SHED ",' TOTAL 350 cuvos GB RIM=326.19 // /"�/_zz/ F ' l '//\ G'� THE QUANTITIES SHOWN ABOVE ARE FOR THE PERMIT PROCESS �,yl\///jj�� ONLY. THESE VALUES ARE APPROXIMATE. DO NOT USE FOR IE 12" PVC(NE)=323.39 / Wi / / / ,'O' /32 '��/ /'// / \ / / BIDDING, PAYMENT, OR ESTIMATING PURPOSES. IE 12" RCP(S)=323.39 /�,� j / '/� , ;/ /� 11I 1� F (D^Jy �PAVING LEGEND 11 U`^'6"PV� 0.5% ' I\ � 2 / , \\ -_---- I� NEW ASPHALT/UTILITY SAWCUT \/ OVERLAY EXISTING ASPHALT II /y M�, //// /, / j ,, / / //\ r l /\ '.''.'.`. NEW CONCRETE 9 \ // 0 325.60 1' ,' , � ,/ ' � PLAY AREA �az3,' 323.56 a / STAIRS s COICRf(E 325.42 N4 E8 / .. 1 ' "Ci✓� I,/�yrQ '7 / � /' /' /' /' / � }�JQ�� / F3 4./ / � ,- y� ' d„ " 324.25 3 .98 / 0.5% 'V23.20 DE44LF-6"PVCC4 324.011 ' 323.45 32a 38--------------- �i < / / F cn ,�Y / `� FENCE COR. 0.3' N ///14 X3,/ / 9//// i V / / % \"/36"x2 .28 OF CORNER( ) / 22.27/ 40 LF`4"DIP@6.1%� 42" �// 323.65,-HHF/ / 06 J/ o�Z'CB RIM=319.82 22/ /' ��� 14" DEC DECK/ n rn { LF-6' DIP 1 ;0.5% - IE 2" PVC(W)=319.42 / `�/ 60 322.0 004 00100 °; C M 320.38 . I 00 i _HOOP IE 2" PVC(E)=31$-- - 00491100000803 - ----LL- M_ - ------ / 42» 1/ ZG� 414 ASPHALT S4 / DEC I NEW RESTROOM I� \ F / I FFE:322.0 22 I F 28»( / CB RIM 320.27 COULD NOT OPEN I 3 321.34 320.60 321.o7N 88'06'02" E 135.6'(C)\ \133(P) / I i I I G i l LOT 4 II \ , I Ii R\ i I 320.89 r o' 30' WARNER ADDITION II VOL GRADING AND DRAINAGE PLAN -------------------------- 1 nT ? 76 1SCALE: 1" = 20' 20 0 10 20 40 CATCH BASIN SCHEDULE MARK TYPE RIM ELEV INV ELEV NOTES O TYPE 1 323.80 (6" S): 320.26 2 3 4 C3.3 C3.3 C3. O TYPE 1 322.90 (6" N): 319.92 IV W): 319.82 2 3 4 C3. C3.3 C3. TYPE 322.10 (6" E1: 319.60 (6" S): 319.50 2 3 4 C3. C3.3 C3. ® TYPE 321.80 IV 5): 318.71 2 3 4 C3. C3.3 C3.3 �$ TYPE 1 320.40 (V N): 318.58 (6" S): 318.58 2 3 4 C3.3 C3.3 C3.3 06 TYPE 1 320.50 (12" W): 317.56 (4" E): 317.56 (6" N): 318.10 2 3 4 C3.3 C3. C3.3 O TYPE 320.50 (4" N): 319.0 (4" E): 319.0 (4" W): 319.0 2 3 4 C3.3 C3. C3.3 INFILTRATION TRENCH SCHEDULE MARK SIZE TOP BOT INV ELEV NOTES QI 47' z 10' z 2' 321.0 319.0 IE: (6" PERF PVC): 319.50 IE: (4" DIP OVERFLOW): 321.0 5 C3.3 Q2 1 27' x 10' z 2' 320.0 318.0 IE: (6" PERF PVC): 318.50 IE: (4" DIP OVERFLOW): 320.0 5 C3.3 B L D2024-XXXX APPROVED FOR CONSTRUCTION CITY OF EDMONDS DATE: BY: CITY ENGINEERING DIVISION C 4Mmoh, ENGINEERING 250 4TH AVE. S., SUITE 200 EDMONDS, WASHINGTON 98020 PHONE (425) 778-8500 FAX (425) 778-5536 vg�� 05/05/24 DESIGN: JCO DRAWN: ATD CHECK: JPU JOB NO: 23072.001 DATE: 10/27/23 LI..I � WQNIL Z_ J ry Lo N � �W U Do Lli Z J 0 Z 0 mDou Za 0 z Z �0 � �a LdLL.I w 2 N CD 0- SHEET C3.1 n cause air pollution include grain dust, sawdust, coal, gravel, crushed rock, cement, and boil as Areimissions can contaminate stormwater. The objective of this BMP is to reduce the st m- wate ollutants caused by dust generation and control. Pollutan Control Approach: Prevent dust generation and emissions where feasibl , regularly clean-up du that can contaminate stormwater, and convey dust contaminated stor water to proper treatme t. Applicable BMRs: • Clean, as needed, owder material handling equipment/vehiies. • Regularly sweep dust cumulation areas that can contrmwater. Conduct sweep- ing using vacuum filter eq ipment to minimize dust geneo ensure optimal dust removal. Use dust filtration/collection syst s such as bagho e filters, cyclone separators, etc. to con- trol vented dust emissions that cou contaminate tormwater. Control of zinc dusts in rubber production is one example. Maintain on -site controls to prevent vehicIVrack-out. Maintain dust collection devices on a redular basis. Recommended BMPs: . In manufacturing operations, ain employees to handle owders carefully to prevent gen- eration of dust. • Use water spray to flu dust accumulations to sanitary sewers here allowed by the local sewer authority or t other appropriate treatment system. Use approved st suppressants such as those listed in Methods for st Control (Ecology, 2016b). Appl ation of some products may not be appropriate in close pr imity to receiving waters V'Urisdiction. nveyances close to receiving waters. For more information the with Ecology or the loca Recomrp'ended Treatment BMPs Ksedimentation basins, wet ponds, wet vaults, catch basin filters, vegetated filter strips, o qui- nt 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. 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 /V - Chapter 4 - Page 525 ://www.tcia.orci/TCIA/BUSINESS/ANSI A300 Standards /TCIA/BUSINESS/A300 Standards/A300 Standards. aspx?h key= 202ff566-4364-4686-b7cl -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 H im- 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 3/4-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. O Mowing is a stress -creating activity for turfgrass. C3 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 (Kina Countv 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 (TC IA) 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 Con of strialSites Description of P tant Sources: Industrial activities on soil areas; exp ed and disturbed soils; steep grading; etc. can sources of sediments that can contaminate rmwater runoff. Pollutant Control Approac . imit the exposure of erodible s i , stabilize, or cover erodible soil where necessary to prevent erosio and/or provide treatm for stormwater contaminated with TSS caused by eroded soil. Applicable BMPs: . Limit the exposure of erodible soil . Stabilize entrances/exits to event track -out. See BM 105: Stabilized Construction Access. . Stabilize or cove rod ible soil to prevent erosion. Cover practice o ons include: Us egetative cover such as grass, trees, shrubs, on erodible soil as. Cover exposed areas with mats such as clear plastic, jute, synthetic fiber. . C122: Nets and Blankets and BMP C123: Plastic Covering. Mn 2019 Stormwater Management Manual for Western Washington Volume IV - Chapter 4 - Page 527 \ Table V-A.1: Maintenance Standards - Detention Ponds (continued) / Maintena Com- Defect Conditions When Maintenance Is Needed Results Expected When Maintenance Is Performed ponent Line ' plic- able) Liner is visible and has more than three 1/4-inch holes in it. Liner repaired or replaced. Liner is fully covered. 1,117* rt of berm which has settled 4 inches lower than the design elevation If settlemen arent, measure berm to determine amount of settlement Settlements Settling can be an indic of more severe problems with the berm or outlet works. A Dike is built back to the design ele licensed engineer in the state o shington should be consulted to determine the source of Ponds Berms (Dikes) the settlement. Discemable water flow through pond berm. Ong oi osion with potential for erosion to con- tinue. Piping Piping eliminated. Erosion potential resolved. (Recommend a Gcethechnical engineer be called in to inspect and a to conditi recommend repair of condition. Tree growth on emergency spillways creates blockage problems may cause failure e bens due to uncontrolled overtopping. rees should removed. If root system is small (base less than 4 inches) the root system may be left in Tree Growth is plac herwise the roots should be removed and the berm restored. A licensed engineer in the state of Tree growth on berms over 4 feet in height ma to piping through the berm which could Washington Id be consulted for proper berm/spillway restoration. Emergency Overflow/ Spillway Berms lead to failure of the berm. and over 4 feet in height Discemable water flow thro and berm. Ongoing erosion with potential for erosion to con- tinue. Piping Piping eliminated. Erosion potential reso (Recom a Geotechnical engineer be called in to inspect and evaluate condition and mend repair of condition. Only one layer of rock exists above native soil in area five square feet or larger, or any expos - Emergency Over- Emer 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 /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) Maintenanc Defect Conditions When Maintenance is Needed Results Expected When nance is Per - Component rmed Plugged Air Vents One-half of the cross section of a vent is blocked at any point orthe vent is damaged. s open and functioning. Accumulated sediment depth exceeds 10% of the diameter of the storage area for 1/2 length of storage v ny point Debris and Sediment ceeds 15 % of diameter. All sediment and debris removed from storage e: 72-inc a tank would require cleaning when sediment reac of 7 inches for more than 1/2 length of 7tank.) area. Storage Area Any openings or voids allowing material to be into 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 a is bent out of shape more than 10% of its design shape. (Revs fired by engineer to determine Tank/pipe repaired or replaced to design. ral 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 spa - Vault Structure Include s in Wall, Bottom, tenance/inspection personnel determines that the vault is not structurally sound. s and d is structurally sound. Damage to and/or Top Slab Cracks wider than 1/2-inch at the joint of any inlet/outlet pipe or any evidence of soil particles entering the vault through the No cracks m\orelPlan3 inch 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