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APVD STM RESUB3 BLD2023-1391+Storm_Drainage_Report+8.29.2024_4.34.57_PM+4471816C � ENGINEERING RESUB Aug 30 2024 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT 250 4th Ave S Ste 200 Edmonds, WA 98020 Phone: (425) 778-8500 Fax: (425) 778-5536 civil & structural engineering & planning BLD2023-1391 DRAINAGE REPORT Mathay Ballinger Park 24100 78th PI W, Edmonds, WA 98026 08129124 CG Project No.: 23072.20 COMPLIES WITH APPLICABLE CITY STORMWATER CODE 1 09/27/2024 1 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 CM 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 August 29, 2024 Drainage Report Section II, 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 9,694 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 is 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) Note: These areas are shown as areas prior to construction. Some of these areas will be removed and replaced with proposed asphalt or concrete. These areas will not match up directly with retrofit calculations. See Section III for storm calculations. 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 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 August 29, 2024 Section II, Page 2 infiltration trenches. The total new/replaced impervious hard surface is 9,694 sf, and the total land disturbance is 17,330 sf. The proposed new/replaced impervious areas on -site are as follows: Roof: 190 sf (0.004 ac) Concrete Pavement: 1,116 sf (0.003 ac) Asphalt Pavement: 8,388 sf (0.193 ac) Total: 9,694 sf (0.223 ac) q 21 0 0 7 242 o 2421 - 24207 242 24213 2421 2 Figure 1-1. Vicinity map (Edmonds GIS). 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 August 29, 2024 Drainage Report Section II, Page 3 11 k• I 241191 24118 s w w 14-288 16-685 _ I 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 August 29, 2024 Drainage Report Section II, Page 4 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 August 29, 2024 Drainage Report Section II, 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 August 29, 2024 Section II, 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. ? 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 ,iid:uunil 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 .1 City of Edmonds Map Title 52 ti Legend Storm Catch Basins o Edmonds p Private ■ Infiltration Storm Manholes p Edmonds p Private Infiltration • Detention Facilities Culvert <all other values> Yes o Facility Feature Creeks Storm Line — <all other values> No, BNSF; No, COUNTY; No, LYNI MOUNTLAKE TERRACE; No, POF SHORELINE; No, STATE; No, WO, — Yes, EDMONDS; Yes, PRIVATE; 1 Facility Lines Storm Ditch ArcSDE.GIS.STREET CENTERLINE' <all other values> 1 2 5; 4 Notes 0 126.30 252.6 Feet 188.1 This ma is a user generated static output from an Internet mapping site and is for Zr257 P � B P PP g reference only. Data layers that appear on this map may or may not be accurate, WGS_1984_Web_Mercator_Auxiliary_Sphere current, or otherwise reliable. © City of Edmonds THIS MAP IS NOT TO BE USED FOR DESIGN OR CONSTRUCTION TOTAL PROJECT AREA: 0.398 ACRES SE 1 /4, SE 1 /4, SECTION 31, TOWNSHIP 27 NORTH, RANGE 4 EAST, W.M. *TOTAL HARD SURFACE: 9,694 SF CB RIM=337.76 = J '_ _ _ '' 1 1 I F TOTAL OFFSITE HARD SURFACE: 1,404 SF ��7.24 3f6.80 ' 26" 2�„PROPOSED PGIS: 1,953 SF E 12" RCP(NW)=335.86 I' --/'---- }--//--I I I F F , M PROPOSED PGPS: 0 SF IE 12" RCP(SE)-335.76 x y' / / F 22» - EXISTING UNMANAGED HARD SURFACE: 4,925 SF / ,'J- f'-8 AA F l TOTAL DISTURBED AREA: 0.398 ACRES CB RIM-33671 _ I Ja �/ 16 F AVERAGE SLOPE: 10% E 12'%-kP(NW)=328.88 /ii _ //_ i : = i F :: ;_F\ 14x2 / NRCS SOIL GROUP: ALDERWOOD URBAN LAND E 12/" CPP(SW)=328.88 'EXISTCB,i' 26" r \ / COMPLEX / RIM: 330.71 i // / F ' / Q �!•� E (12"NWI: 328.88 .i _ -./ - S\ /' \ 34" INFILTRATION RATE: 0.19 IN/HR / V / IE(12"SW):328.88 / M / BRING TO GRADE W/RISER/5� \ / oO / - - -JP3 -/�- -�� - - - - i - - ILL SO LID D LID ON EXISTING CB \ / \ = AREAS TO INFILTRATION FACILITY #1--6,309� j F SF). SIZED TO RECEIVE RETROFIT AREAS. )=324.68 M t Iz Nvc(5w)=324.68 / , \ \ �� -� \�\ = AREAS TO INFILTRATION FACILITY #2 (--4,587 2� // � , � � / ,� � ,�' \ � , \,� \\ r_ r_ _ , \ -F). SIZED TO RECEIVE RETROFIT AREAS. x,/L ; 4 �. l 44" BQ = BYPASS (-2,455 SF). l//nn ;'` �� F F �� /j_-z.5'wl 'CRASS ' GRILL \\ , ' / r K/ y TO DIRECT RUNOFF TO CB AND q A Z6'"I \ Y SHED / I GATE ` > / ' INFILTRATI N TRENCH I O C 33" / I P / s)nt , 4 95,481 SF \ F2g = ASPHALT ROUTED TO INFILTRATION/� V f�/ 1RACK /50„ P 2 0431004028 ii TRENCH #2 IN PLACE OF BYPASS -2 500 SF .� - - - IE 12PVC(NE)-323.39 u / �� ,COST ' = 32" IE 12" RCP(S)=323.39 /� 3/ �� '�0 �� F // 68LF�6"PV 0.5% / I\ /-__-____ '�' `2\ RETROFIT 9 \ / /A-g/ �/f------�i� �/ �z3,' PLAY AREA / + �/ Q / /`i• ' 325.60 323.56 / 5 48" z z.�wlDeGaisNEDDITCH �' STAIRS TO DIRECT RUNOFF TO CB AND '/ 325.42 /F IN IL I ILT8ENC 3 /32a.s5 A 3 .98 gfa5o '3 - 8 X1 Q. x2` c ;'/'.'/ DEC / / - / 324.05 323.20 44 LF ^d0.5% 323 10 Alc 324.0 323.28 ✓ - / / / /i AREAS INCLUDED FOR ,� ;P•r > FENCE COK TRENCH #1 SIZING / 14 MAINTA�N COVER m;. OF CORNER ��T 22.27/ 48LABO-PIPE 42 �\ tl�/ O /,/ 323.65\ 98L/F'"4�'DIPI�4.0% Z 2� F I / O O z39 EXISTI G DAM CB RIM=319.82 »_ / 14» '2.5' WIDE GRAS�LINED DI CH /^'N / DEC D SD / 6�OIP 0.5% TO DIRECT RUNOFF TO CB AND / I E 2 PVG(W)=31 9.42 INFILT TION THE A 322.0 / / ✓ f 1$A� _ 0 004f3 00100 _ eSOUTHERN&RTION GRADING EXIST CB DDRAINAGE PLAN ' / \ RIM: 320.3&'' E (2" PVC Q: 319.43 OO i - > / - IE IS" • 26 ( ) IE (6" DIPS): 318.9 """"""•' 00491100000803 OOP DEC :•:):....:..... RETROFIT i F TP- / \ :I :FE:;3�� i •i:•i:•::•: }'r'r'r: Q , I '%I':':':':':':':':':'� • :•� � � � � � � � � � � • RESTROOM AND ALL UTILITY STUB \ �' / / �rl/' \ : 1•': •':.... ... OUTS PREVIOUSLY COMPLETED BY \\ OWNER. UTILITY STUB OUTS INCLUDE .+� / P f .':: 1:: •:::/' • .. G 36' ^O / SEWER, WATER AND STORM \\ '1I / PROPOSEDARPKING, PAVEMEN� I/� - $ ) " F ( / CB RIM=320.27 \\ / PATCHING, AND PORTIONS OF ' ••(( ZS 3 I \ WALKWAY TOECOURSE NG TO / _______COULD NOT OPEN - - - - - - - - ------_ \ NATURALWALKWAINAG LOWALETO TI I "''-"- 1 U----------- ---- - EXISTING CBS fi W------------------ r _ _sb I �: 321.34 320.60 321.07 N BS°06'02" E 6'(C) \ 135.88'(P) / II °' AREAS INCLUDED FOR IIf _ _ _ _I.. 0'8 °.- CONNECTTO EXISTING STORM LOT 4 320.89 I' r TRENCH #1 SIZING L , - Z�ZgS' II o' I 3o i WARNER ADDITION II - - -L ----�--- t --- - I n i > VOL 15, PG. 76 I I-t GRADING AND DRAINAGE PLAN ' 1 SCALE: 1" = 20' 20 0 10 20 40 GRADING AND UTILITY PLAN NOTES 1. SOILS REPORT REPORT NUMBER: 074217.010 PREPARED BY: LANDAU ASSOCIATES DATED: 23 JUNE 2023 2. A MINIMUM OF 3' HORIZONTAL SEPARATION AND I' VERTICAL SEPARATION 15 REQUIRED BETWEEN DRY UTILITIES (POWER, GAS, PHONE, CABLE, ETC) AND SEWER, WATER AND STORM, AND A MINIMUM OF 5' HORIZONTAL SEPARATION AND V VERTICAL SEPARATION FROM ANY CITY -OWNED LINES. 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 V OF COVER UNDER LANDSCAPE AND OTHER HARD SURFACES. 6. TOTAL NEW REPLACED HARD SURFACES: 9,694 SF. - NEW ASPHALT PAVEMENT:8,388 SF.4,733 SF PORTION ROUTED TO INFILTRATION#1, 1,200 SF PORTION ROUTED TO INFILTRATION TRENCH 12, 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:1,116 SF.1,044 SF PORTION ROUTED TO INFILTRATION#1, 72 SF PORTION ROUTED TO INFILTRATION TRENCH #2. NOTE: BOTH INFILTRATION TRENCHES SIZED FOR ALL PROPOSED HARDSCAPE AREAS INCLUDING 25% RETROFIT AND BYPASS AREAS. BYPASS AREAS ARE TO FLOW ALONG NATURAL DRAINAGE PATH AND INTO THE CITY M54 AS INDICATED ON PLANS. PORTIONS OF EXISTING HARDSCAPE TO FLOW TO INFILTRATION TRENCHES. GRADING QUANTITIES TOTAL EXCAVATION (CUT) - 10 CU YDS TOTAL EMBANKMENT (FILL) 340 CU YDS TOTAL 350 CU YDS THE QUANTITIES SHOWN ABOVE ARE FOR THE PERMIT PROCESS ONLY. THESE VALUES ARE APPROXIMATE. DO NOT USE FOR BIDDING, PAYMENT, OR ESTIMATING PURPOSES. PAVING LEGEND - NEW ASPHALT/UTILITY SAWCUT OVERLAY EXISTING ASPHALT NEW CONCRETE CATCH BASIN SCHEDULE MARK TYPE RIM ELEV INV ELEV NOTES CI TYPE 1 323.80 (6 S): 320.26 C3.3 C3.3 C3.3 �} TYPE 1 322.90 (6" N): 319.92 (6 W): 319.82 2 3 4 C3.3 C3.3 C3.3 /_ TYPE 1 322.10 (6' E): 319.60 (6' S): 319.50 2 3 4 C3. C3.3 C3.3 <4�' �-/ TYPE 1 321.80 IS" S): 318.71 2 3 4 C3.3 C3.3 C3.3 < TYPE 320.40 IS N): 318.69 (6 5): 318.58 2 3 4 C3.3 C3.3 C3.3 (6) TYPE I 320.54 (12 W. 318.44 (6 E). 318.54 (4 N): 318.54 2 3 4 C3.3 C3.3 C3.3 (,7,1 TYPE 1 320.50 (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 �,I 47' z 10' z 2' 321.0 319.0 IE: (6" PERF PVC): 319.50 IE: (4" DIP OVERFLOW): 321.0 5 C3.3 IE: IS" PVC, INLET, NW, N): 319,50 EYE 27' x 11' x 2' 320.0 318.0 IE: IS" DIP, INLET, E): 318.50 IE: (6" PERF PVC): 318.5. C3.3 e IE: (4" DIP OVERFLOW): 320.0 BLD2023-1391 APPROVED FOR CONSTRUCTION CITY OF EDMONDS DATE: BY: CITY ENGINEERING DIVISION o cm ENGINEERING 250 4TH AVE. S., SUITE 200 EDMONDS, WASHINGTON 98020 PHONE (425) 778-8500 FAX (425) 778-5536 FOR REPORT USE ONLY DESIGN: JCO DRAWN: ATD CHECK: JPU JOB NO: 23072.001 DATE: 10/27/23 (Ld V w a 3: IL Q J � LD w N Q W U Do Q Ld c� a 0> z 0 J a Q m Do N Z Q 0 Z Z 2 O 0 < Q < :2N�w C7D_ y SHEET C3.1 City of Edmonds Map Title 52 ti Legend Storm Catch Basins o Edmonds p Private ■ Infiltration Storm Manholes p Edmonds p Private Infiltration • Detention Facilities Culvert <all other values> Yes o Facility Feature Creeks Storm Line — <all other values> No, BNSF; No, COUNTY; No, LYNI MOUNTLAKE TERRACE; No, POF SHORELINE; No, STATE; No, WO, — Yes, EDMONDS; Yes, PRIVATE; 1 Facility Lines — Storm Ditch Contour Lines 10 50; 100 ArcSDE.GIS.STREET CENTERLINE' <all other values> Notes 0 126.30 2S2.6 Feet 188.1 This ma is a user generated static output from an Internet mapping site and is for 2,25% P � B P PP g reference only. Data layers that appear on this map may or may not be accurate, WGS_1984_Web_Mercator_Auxiliary_Sphere current, or otherwise reliable. © City of Edmonds THIS MAP IS NOT TO BE USED FOR DESIGN OR CONSTRUCTION Mathay Ballinger Park— CG # 23072.20 August 29, 2024 Drainage Report Section II, Page 7 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. 3 n a. 40TH 51 SW - l , •.a" • - :4ra- � J 24onieLsw 41srsr1w � r PROJECT 3 _ SITE OUTFALL rsw °• . F4106 - � 241Q 1a2n+ r. ]4212 74714 24211 ` 24218 24219 i4:,8 - ° 4 1i1" °„ OUTFALL :.1,„1 t ° ° Figure II-1. Vicinity map showing stormwater flow path and distance to outfall (Edmonds GIS). 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 August 29, 2024 Section II, Page 8 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 78th 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 Drainage Report August 29, 2024 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.b.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, two infiltration trenches were sized. This trench is split into an upper 47'x10'x2' trench and a lower 27'x11'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: Total Hardscape Area: New Walking Path (Asphalt): 6,372 sf (0.146 ac) New Restroom Roof.• 190 sf (0.004 ac) New Sawcut (Asphalt): 773 sf (0.018 ac) New Parking (Asphalt): 1,243 sf (0.029 ac) New Concrete Pads (Concrete): 1,116 sf (0.026 ac) *Existing Concrete (25% Retrofit): 498 sf (0.011 ac) **Existing Asphalt Pavement (25% Retrofit): 734 sf (0.017 ac) Total: 10,926 sf (0.251 ac) *Total existing concrete to remain is 1,993 sf. **Total existing asphalt to remain is 2,935 sf. 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 August 29, 2024 Section III, Page 2 Hardscape to Trench #1: New Walking Path (Asphalt): 4,733 sf (0.109 ac) New Concrete Pads (Concrete): 1,044 sf (0.024 ac) Existing Concrete (25% Retrofit): 498 sf (0.011 ac) Asphalt Pavement (25% Retrofit): 34 sf (0.001 ac) Total: 6,309 sf (0.145 ac) Hardscape to Trench # 2: New Walking Path (Asphalt): 1,639 sf (0.038 ac) New Restroom Roof- 190 sf (0.004 ac) New Sawcut (Asphalt): 773 sf (0.018 ac) New Parking (Asphalt): 1,243 sf (0.029 ac) New Concrete Pads (Concrete): 72 sf (0.002 ac) Existing Asphalt Pavement (25% Retrofit): 670 sf (0.015 ac) Total: 4,587 sf (0.105 ac) Note that approximately Z455 sf of the proposed walkway and parking area cannot be routed to the infiltration trenches due to existing elevations, feasible locations of infiltration trenches, and required pipe coverage and slope. Due to these reasons these areas are proposed to be routed to the existing drainage system and designed as a bypass. In its place existing areas totaling at least Z500 sf, originating from the existing asphalt and concrete areas, will flow into the proposed and existing catch basins and will be routed to the infiltration trenches. The infiltration trenches have been sized to incorporate the total proposed and retrofit areas. See sizing calculations below. Additionally, see 11x17 exhibits attached at the end of this section that display areas associated with WWHM calculations. 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: Asphalt Parking: 1,953 sf (0.045 ac) Total: 1,953 sf (0.045 ac) FlnIni rrintrnl The project has a total of less than 10,000 sf of new/replaced 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. Additionally, please see the map snips below, found using USGS EROS aerial maps, of the site prior to July 61", 1977. Aerial imagery is also provided from September 1977 as this aerial is clearer and shows the site as existing as grass/lawn 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 August 29, 2024 Section III, Page 3 areas. From historic aerials, the site looks to have been cleared in the 50's. The site existed as grass/lawn prior to July 6th, 1977 and is modelled as pasture areas to be conservative in our 0.15 cfs check. This shows that even with conservative assumptions, the 0.15 cfs increase requirement is met. Figure III-1. September 18th, 1971, aerial photo with time stamp. 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 August 29, 2024 Section I11, Page 4 Figure III-2. September 5th, 1977, aerial photo with time stamp. C CM 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 August 29, 2024 Section III, Page 5 : x 0 Y • I �4 A -;►*� _; ..��'� � ram. — imp Figure III-3. September 5`h, 1977, aerial photo zoomed to project site. CM 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 August 29, 2024 Section III, Page 6 Infiltration Trench #1 Sizing: F-7711-S)C tS Gravel Trench Bed 1 Mitigated SCENARIOS ❑ Pedeveloped 0 Mitigated Run Scen Basic Elements UNPIN ®UUm UNN® ®EM Pro Elemats rn Commercial Toolbox t C Move Elements Save v,y Load �,y - 40 #� Tue 10.09a�gard Facility Name Downstream Connection Facility Type r ReapitationAppfedto Facity � Evaporation Appfed to Facayi Gravel Trench Bed 1 Outlet 1 Outlet 2 Outlet 3 10 0 0 Gravel TrerchlBed Quids Trench I Facility Dimension Diagram Facility Dimensions Trench Length [it) 47 Trench BottomW kh MI 10 EDective Total Depth Ih1 0 Too and baton slope (HM 0� Left Side Slope IHM 0� Right Side Slope(HM 0� Material Layers for Trench/Bed Layer Thv'ckness(ft) 0 Layer 1 porosity 11111 0.3 Layet2 Thickness(@) 0 Layer 2 pao* (0-11 p� L yet 3 Thick- (n) Layer 3 porosity (0-11 Infiltration F---J Outlet Structure Data I Rea Hei¢t (ft) 1.95 J Rea Dimter f) 12 J Rea Type FF _-� Notch Type Orifice Diameter Height Number (n) (11) 1 Fo---J Fo­J 2 Fo---J 3 Fo---J Fo---J TteadsVol ne a Rem Head(ace) .DOB M.-red Inthstion Rate "I 0.19 J Reduction Facto lirli9adorl J Show Trench Open Table _J Use Wetted 5ulaceAna lsidavabl NO J IrivalStage(R] 0 Total Vclune Infiltrated [acfll 48519 Total Volme Though Fac74 (acitl 55-73 Total Vdune Though Rea (acel 621 Percent Infiltrated 8886 Size Infiltration Trench Target %: 100 J Figure III-4. Schematic snippet of modeling setup for infiltration trench #1. 501 POC 1 PredeveWped 801 POC1 Mk.Wdflpn .- 0.00 0 v 11100 0 J 0.00 0.00 10E-5 10Ed 10E3 10E-2 10E-1 1 10 100 Percent Time Exceeding Stearn Protection Duration LID Duration I Flow Frequency Walm Quafty Hydograph Welland Input Volunes LID Report Recharge Duration Recharge Redeveloped Redwge Mitigated Analyze dMaseta Co r Monthly FF mpact WDM � Delete Selected Duration Died AIIDatasets Flow Stage Reap Evap POC1 Flood Frequency Method IT Log Pearson Type III 178 (' Webull r Cr. n r Gringorten Facility PASSED F1oor(ofs) Predev Kit Percentage Pass/Fail 0.0002 586285 44552 7 Pass D.0002 565916 44453 7 Pass D.0002 545273 44348 8 Pass 0.0002 527491 44255 8 Pass D.0002 508884 44161 8 Pass D.0002 492810 44068 8 Pass 0.0003 476019 43947 9 Pass 0.0003 461541 43837 9 Pass 0.0003 447779 43743 9 Pass D.0003 433300 43655 10 Pass D.0003 420914 43583 10 Pass 0.0003 407977 43479 10 Pass 0.0003 396472 43424 30 Pass D.0003 384416 43325 11 Pass D.0003 373846 43264 11 Pass 0.0004 363662 43203 11 Pass 0.0004 352927 43137 12 Pass D.0004 343624 43082 12 Pass D.0004 333660 43011 12 Pass 0.0004 325017 42939 13 Pass 0.0004 315823 42879 13 Pass D.0004 307676 42813 13 Pass D.0004 299859 42736 14 Pass 0.0004 291491 42653 14 Pass 0.0004 284279 42581 14 Pass D.0005 276627 42504 15 Pass D.0005 269801 42438 15 Pass 0.0005 263085 42383 16 Pass 0.0005 255984 42334 16 Pass D.0005 249708 42273 16 Parser D.0005 243102 42202 17 Pass 0.0005 237267 42130 17 Pass 0.0005 231156 42047 18 Pass D.0005 225816 41992 18 Pass Figure III-5. LID Duration Hydrograph depicting compliance with standard (Trench #1). 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 August 29, 2024 Section 111, Page 7 WWHM2012 PROJECT REPORT Project Name: North Site Name: Mathay Ballinger Park Site Address: 24102 77TH PL W City : EDMOND Report Date: 8/27/2024 MGS Regoin Puget East Data Start 1901/10/1 Data End : 2058/09/30 DOT Data Number: 02 Version Date: 2023/01/27 Version : 4.2.19 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 C, Forest, Flat C, Forest, Mod Pervious Total Impervious Land Use Impervious Total Basin Total acre .021 .124 0.145 acre 0 0.145 Element Flows To: Surface Interflow MITIGATED LAND USE Name : Basin 1 Bypass: No Groundwater 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 August 29, 2024 Section III, Page 8 GroundWater: No Pervious Land Use acre Pervious Total 0 Impervious Land Use acre SIDEWALKS FLAT 0.036 *Concrete pad and retrofit SIDEWALKS MOD 0.109 *Proposed walking path Impervious Total 0.145 Basin Total 0.145 Element Flows To: Surface Interflow Groundwater Gravel Trench Bed 1 Gravel Trench Bed 1 Name : Gravel Trench Bed 1 Bottom Length: 47.00 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.): 49.519 Total Volume Through Riser (ac-ft.): 6.21 Total Volume Through Facility (ac-ft.): 55.73 Percent Infiltrated: 88.86 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 ANALYSIS RESULTS 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 August 29, 2024 Section III, Page 9 Stream Protection Duration Predeveloped Landuse Totals for POC #1 Total Pervious Area:0.145 Total Impervious Area:O Mitigated Landuse Totals for POC #1 Total Pervious Area:O Total Impervious Area:0.145 Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.002457 5 year 0.00381 10 year 0.004544 25 year 0.00529 50 year 0.005733 100 year 0.006097 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.034395 5 year 0.049738 10 year 0.059562 25 year 0.071516 50 year 0.080083 100 year 0.088371 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. LID Duration Ranked Annual Peaks for Predeveloped and Mitigated. Rank Predeveloped Mitigated 1 0.0074 0.1395 2 0.0072 0.1097 3 0.0072 0.0828 4 0.0068 0.0808 5 0.0067 0.0804 6 0.0064 0.0799 7 0.0062 0.0711 8 0.0060 0.0688 9 0.0057 0.0674 10 0.0056 0.0638 11 0.0056 0.0637 12 0.0054 0.0621 13 0.0053 0.0608 POC #1 250 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 August 29, 2024 Section III, Page 10 14 0.0053 0.0593 15 0.0050 0.0573 16 0.0050 0.0570 17 0.0050 0.0561 18 0.0049 0.0561 19 0.0047 0.0555 20 0.0042 0.0534 21 0.0042 0.0525 22 0.0041 0.0519 23 0.0041 0.0510 24 0.0040 0.0508 25 0.0040 0.0506 26 0.0040 0.0502 27 0.0039 0.0486 28 0.0039 0.0485 29 0.0038 0.0484 30 0.0038 0.0482 31 0.0038 0.0482 32 0.0037 0.0481 33 0.0035 0.0465 34 0.0034 0.0463 35 0.0034 0.0454 36 0.0034 0.0453 37 0.0033 0.0448 38 0.0033 0.0437 39 0.0032 0.0437 40 0.0032 0.0436 41 0.0032 0.0436 42 0.0031 0.0433 43 0.0031 0.0433 44 0.0030 0.0432 45 0.0030 0.0431 46 0.0029 0.0431 47 0.0028 0.0426 48 0.0028 0.0424 49 0.0028 0.0420 50 0.0028 0.0419 51 0.0028 0.0418 52 0.0027 0.0411 53 0.0027 0.0408 54 0.0027 0.0406 55 0.0027 0.0406 56 0.0027 0.0405 57 0.0027 0.0402 58 0.0027 0.0402 59 0.0026 0.0401 60 0.0026 0.0394 61 0.0026 0.0393 62 0.0026 0.0392 63 0.0026 0.0392 64 0.0025 0.0391 65 0.0025 0.0389 66 0.0025 0.0388 67 0.0025 0.0385 68 0.0025 0.0383 69 0.0024 0.0383 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 August 29, 2024 Section III, Page 11 70 0.0024 0.0382 71 0.0024 0.0380 72 0.0024 0.0375 73 0.0024 0.0374 74 0.0024 0.0371 75 0.0024 0.0360 76 0.0024 0.0358 77 0.0024 0.0353 78 0.0023 0.0348 79 0.0023 0.0347 80 0.0023 0.0338 81 0.0023 0.0338 82 0.0022 0.0333 83 0.0022 0.0328 84 0.0022 0.0328 85 0.0022 0.0328 86 0.0022 0.0323 87 0.0022 0.0320 88 0.0022 0.0320 89 0.0022 0.0320 90 0.0022 0.0315 91 0.0022 0.0313 92 0.0021 0.0308 93 0.0021 0.0307 94 0.0021 0.0305 95 0.0021 0.0305 96 0.0020 0.0304 97 0.0020 0.0303 98 0.0020 0.0303 99 0.0020 0.0299 100 0.0019 0.0294 101 0.0019 0.0290 102 0.0019 0.0289 103 0.0019 0.0281 104 0.0019 0.0278 105 0.0019 0.0278 106 0.0018 0.0276 107 0.0018 0.0275 108 0.0018 0.0274 109 0.0018 0.0272 110 0.0018 0.0269 111 0.0017 0.0268 112 0.0017 0.0266 113 0.0017 0.0264 114 0.0017 0.0262 115 0.0017 0.0260 116 0.0016 0.0259 117 0.0016 0.0258 118 0.0016 0.0255 119 0.0016 0.0253 120 0.0016 0.0252 121 0.0016 0.0247 122 0.0015 0.0247 123 0.0015 0.0246 124 0.0015 0.0245 125 0.0015 0.0245 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 August 29, 2024 Section III, Page 12 126 0.0014 0.0244 127 0.0014 0.0240 128 0.0014 0.0237 129 0.0013 0.0235 130 0.0013 0.0234 131 0.0013 0.0233 132 0.0013 0.0232 133 0.0013 0.0229 134 0.0012 0.0228 135 0.0012 0.0211 136 0.0012 0.0210 137 0.0012 0.0209 138 0.0012 0.0197 139 0.0012 0.0194 140 0.0012 0.0193 141 0.0011 0.0191 142 0.0011 0.0190 143 0.0011 0.0188 144 0.0010 0.0184 145 0.0010 0.0179 146 0.0010 0.0178 147 0.0010 0.0176 148 0.0010 0.0176 149 0.0009 0.0161 150 0.0009 0.0159 151 0.0008 0.0156 152 0.0007 0.0156 153 0.0006 0.0131 154 0.0006 0.0103 155 0.0003 0.0101 156 0.0002 0.0083 157 0.0001 0.0072 LID Duration POC #1 The Facility PASSED The Facility PASSED. Flow(cfs) Predev Mit Percentage Pass/Fail 0.0002 586285 44552 7 Pass 0.0002 565916 44453 7 Pass 0.0002 545273 44348 8 Pass 0.0002 527491 44255 8 Pass 0.0002 508884 44161 8 Pass 0.0002 492810 44068 8 Pass 0.0003 476019 43947 9 Pass 0.0003 461541 43837 9 Pass 0.0003 447779 43743 9 Pass 0.0003 433300 43655 10 Pass 0.0003 420914 43583 10 Pass 0.0003 407977 43479 10 Pass 0.0003 396472 43424 10 Pass 0.0003 384416 43325 11 Pass 0.0003 373846 43264 11 Pass 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 August 29, 2024 Section III, Page 13 0.0004 363662 43203 11 Pass 0.0004 352927 43137 12 Pass 0.0004 343624 43082 12 Pass 0.0004 333660 43011 12 Pass 0.0004 325017 42939 13 Pass 0.0004 315823 42879 13 Pass 0.0004 307676 42813 13 Pass 0.0004 299859 42736 14 Pass 0.0004 291491 42653 14 Pass 0.0004 284279 42581 14 Pass 0.0005 276627 42504 15 Pass 0.0005 269801 42438 15 Pass 0.0005 263085 42383 16 Pass 0.0005 255984 42334 16 Pass 0.0005 249708 42273 16 Pass 0.0005 243102 42202 17 Pass 0.0005 237267 42130 17 Pass 0.0005 231156 42047 18 Pass 0.0005 225816 41992 18 Pass 0.0006 220421 41937 19 Pass 0.0006 214751 41866 19 Pass 0.0006 209686 41789 19 Pass 0.0006 204402 41734 20 Pass 0.0006 199667 41668 20 Pass 0.0006 194603 41579 21 Pass 0.0006 190199 41524 21 Pass 0.0006 185960 41458 22 Pass 0.0006 181335 41387 22 Pass 0.0006 177262 41321 23 Pass 0.0007 172858 41249 23 Pass 0.0007 169059 41178 24 Pass 0.0007 164986 41112 24 Pass 0.0007 161297 41045 25 Pass 0.0007 157774 40990 25 Pass 0.0007 153920 40913 26 Pass 0.0007 150617 40853 27 Pass 0.0007 147149 40781 27 Pass 0.0007 143956 40710 28 Pass 0.0007 140488 40649 28 Pass 0.0008 137405 40594 29 Pass 0.0008 134378 40533 30 Pass 0.0008 131240 40478 30 Pass 0.0008 128432 40412 31 Pass 0.0008 125515 40352 32 Pass 0.0008 122872 40302 32 Pass 0.0008 120340 40236 33 Pass 0.0008 117587 40176 34 Pass 0.0008 115055 40104 34 Pass 0.0009 112413 40033 35 Pass 0.0009 110156 39966 36 Pass 0.0009 107623 39895 37 Pass 0.0009 105421 39823 37 Pass 0.0009 103274 39768 38 Pass 0.0009 100907 39708 39 Pass 0.0009 98870 39642 40 Pass 0.0009 96613 39576 40 Pass 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 August 29, 2024 Section III, Page 14 0.0009 94631 39515 41 Pass 0.0009 92539 39449 42 Pass 0.0010 90668 39388 43 Pass 0.0010 88851 39322 44 Pass 0.0010 86869 39234 45 Pass 0.0010 85218 39179 45 Pass 0.0010 83401 39119 46 Pass 0.0010 81695 39058 47 Pass 0.0010 79933 38987 48 Pass 0.0010 78392 38937 49 Pass 0.0010 76850 38882 50 Pass 0.0011 75199 38810 51 Pass 0.0011 73712 38733 52 Pass 0.0011 72116 38667 53 Pass 0.0011 70685 38607 54 Pass 0.0011 69363 38557 55 Pass 0.0011 67932 38486 56 Pass 0.0011 66611 38414 57 Pass 0.0011 65179 38342 58 Pass 0.0011 63968 38282 59 Pass 0.0011 62592 38210 61 Pass 0.0012 61381 38150 62 Pass 0.0012 60225 38084 63 Pass 0.0012 59014 37996 64 Pass 0.0012 57858 37941 65 Pass 0.0012 56702 37864 66 Pass 0.0012 55656 37809 67 Pass 0.0012 54494 37748 69 Pass 0.0012 53498 37682 70 Pass Passes up to 50% of the 2 year peak flow as required. 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 50.71 N 88.86 Total Volume Infiltrated 50.71 0.00 0.00 88.86 0.00 0% No Treat. Credit Compliance with LID Standard 8 Duration Analysis Result = Passed 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 August 29, 2024 Section III, Page 15 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. 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 August 29, 2024 Section III, Page 16 Infiltration Trench #2 Sizing: t o p E{ C• _- _ Ei Facility Name Gravel Tramh Bedl Outlet 1 Outlet 2 Outlet 3 DoMrnstream Connection 10 1 0 0� SCENARIOS ❑ Predeveloped ❑h'.li3ale Facility Type Gravel TrerrclyBstl r P-WitatianAppfedroFacYy, Quick Trench I r Evapaa(nAPpfed to Facility Facility Dimension Diagram I Run Scenario Basic Elements ®®®® ®�■� M®®L ®D Facility Dimensions Outlet Structure Data Trench Lergth (kl 0 Trench Bodom Wdh[k) 11 Reer HeShi[k] 1.95 J Rest D-Mer [nI 12 J slope [k) 0 Top and bokam slope MM 0 Rest Type � J Top and bottom Lek Side Slope HM 0 Notch Type Pro Elements Right Side Slope HM 0 Material Layers for Trench/Bed ®� Layer 1 Thickness [it) 0 Orifice Diameter Height Lay. 1 potosity[0-11 03 Number (n) 01) Layer 2 Thickness Btl 0 1 Fo--- JFo--- J Layer 2 pecrely[D1) 0 2 Fo---J Fo---J Layer 3 Thickress 0tl 0 3 Fo---J Fo---J Lay. 3 parusty (Dl) I� Commercial Toobox TrenchVaYme at Rem Head ecfl) .004 Infiltration�J Measmed Initiation Rate Cdhl 019 J Show Trench Open Tale J Facmr Cr�4actul �J m 0 M CRedctim Use Wetted SUdese Asea(sidewals) NO J Initial Stage W) 0 ., TotalVolme lrtirated(ack) 33.769 Tota1Volsne Though Fac 3978 Totalyol me Through Rim (ack) 601 Pacert Infiltrated MAST MareE� Size Infil%:17100n Trench Taret X: 10g0 Save zy I Load xy I x r'anc,1e1 K iF Tue 1019a-South �1 Ila F 0 00 )U 0.00 0 J IL 0.00 0.00 Figure III-4. Schematic snippet of modeling setup for infiltration trench #2. F----t Time E--Aling E 501 POC1 Predevelopecl iSgated Flow 30 Stream Protection Duration DD Duration Flow Frequency Water Quality Hydrograph Welland Input Volumes LID Report Recharge Duation Recharge Predevebped I Recharge Mitigated Analyze dalasets Cam r Mont*FF y pactWDM � Delete Selected Duration Chart 1 '1 80•1 All Datasets Fkxv Slage Preap Evap ?.PQC_1.... Flood Frequency Method G Log Pearson Type III 178 !' Weibull !' Curmane C' Gringorlen The Facility PASSED Fl-(cls3 Pt•etlev Kit Percentage Pass/Pail 0.0001 589038 64684 30 Pass 0.0001 569219 64519 11 Pass 0.0002 548190 64354 11 Pass 0.0002 530849 64299 12 Pass 0.0002 511967 64183 12 Pass 0.0002 496223 64078 12 Pass 0.0002 479212 63968 13 Pass 0.0002 465119 63803 13 Pass 0.0002 449650 63693 14 Pass 0.0002 436824 63528 14 Pass 0.0002 422951 63418 14 Pass 0.0002 411501 63308 15 Pass 0.0002 398784 63198 15 Pa- 0.00 02 387994 63088 16 Pss 0.0002 376268 62977 16 Pass 0.0003 366304 62812 17 Pass 0. 0003 355404 62702 17 Pass 0.0003 346376 62592 18 Pass 0.0003 337513 62482 18 Pass 0.0003 327769 62317 19 Pass 0.0003 319567 62207 19 Pass 0.0003 310538 62097 19 Pass 0.0003 302831 61987 20 Pass 0.0003 299299 61876 21 Pass 0.0003 287197 61711 21 Pass 0. 0003 279380 61601 22 Pass 0.0003 272719 61491 22 Pass 0, 0003 265287 61381 23 Pass 0.0004 259011 61326 23 Pass 0.0004 251965 61161 24 Pass 0.0004 246075 61oSl 24 Pass 0.0004 239524 60941 25 Pass 0.0004 234019 60831 25 Pass 0.0004 228073 60720 26 Pass Figure III-5. LID Duration Hydrograph depicting compliance with standard (Trench #2). 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 August 29, 2024 Section III, Page 17 WWHM2012 PROJECT REPORT Project Name: South Site Name: Mathay Ballinger Park Site Address: 24102 77TH PL W City : EDMOND Report Date: 8/27/2024 MGS Regoin Puget East Data Start 1901/10/1 Data End : 2058/09/30 DOT Data Number: 02 Version Date: 2023/01/27 Version : 4.2.19 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 C, Forest, Flat Pervious Total Impervious Land Use Impervious Total Basin Total acre .105 0.105 acre 0 0.105 Element Flows To: Surface Interflow MITIGATED LAND USE Name : Basin 1 Bypass: No Groundwater 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 August 29, 2024 Section III, Page 18 GroundWater: No Pervious Land Use acre Pervious Total 0 Impervious Land Use acre ROOF TOPS FLAT 0.004 *Restroom roof SIDEWALKS FLAT 0.048 *Walkways, concrete pads, and retrofit PARKING FLAT 0.053 *Pavement patching and parking. Existing areas to be routed to infiltration trench in place of these areas. Impervious Total 0.105 Basin Total 0.105 Element Flows To: Surface Interflow Gravel Trench Bed 1 Gravel Trench Bed 1 Name : Gravel Trench Bed 1 Bottom Length: 27.00 ft. Bottom Width: 11.00 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.): 33.769 Total Volume Through Riser (ac-ft.): 6.01 Total Volume Through Facility (ac-ft.): 39.78 Percent Infiltrated: 84.89 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 ANALYSIS RESULTS Groundwater 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 August 29, 2024 Section III, Page 19 Stream Protection Duration Predeveloped Landuse Totals for POC #1 Total Pervious Area:0.105 Total Impervious Area:O Mitigated Landuse Totals for POC #1 Total Pervious Area:O Total Impervious Area:0.105 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) 0.001765 0.002728 0.003249 0.003777 0.004091 0.004349 Predeveloped. POC #1 Periods for Mitigated Flow(cfs) 0.024904 0.035477 0.042854 0.052576 0.060099 0.067857 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. POC #1 LID Duration Ranked Annual Peaks for Predeveloped and Mitigated. Rank Predeveloped Mitigated 1 0.0052 0.1017 2 0.0052 0.0759 3 0.0049 0.0594 4 0.0049 0.0593 5 0.0046 0.0570 6 0.0044 0.0554 7 0.0044 0.0510 8 0.0043 0.0484 9 0.0041 0.0476 10 0.0040 0.0458 11 0.0039 0.0454 POC #1 250 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 August 29, 2024 Section III, Page 20 12 0.0039 0.0448 13 0.0038 0.0439 14 0.0038 0.0430 15 0.0036 0.0428 16 0.0036 0.0420 17 0.0036 0.0416 18 0.0035 0.0408 19 0.0030 0.0408 20 0.0030 0.0398 21 0.0030 0.0379 22 0.0030 0.0379 23 0.0029 0.0374 24 0.0029 0.0367 25 0.0029 0.0361 26 0.0028 0.0360 27 0.0028 0.0358 28 0.0028 0.0357 29 0.0027 0.0354 30 0.0027 0.0347 31 0.0027 0.0343 32 0.0027 0.0343 33 0.0025 0.0342 34 0.0025 0.0341 35 0.0025 0.0339 36 0.0024 0.0332 37 0.0023 0.0328 38 0.0023 0.0323 39 0.0022 0.0323 40 0.0022 0.0318 41 0.0022 0.0317 42 0.0022 0.0317 43 0.0022 0.0310 44 0.0022 0.0309 45 0.0021 0.0307 46 0.0021 0.0307 47 0.0020 0.0306 48 0.0020 0.0305 49 0.0020 0.0304 50 0.0020 0.0303 51 0.0020 0.0302 52 0.0020 0.0301 53 0.0020 0.0297 54 0.0020 0.0296 55 0.0019 0.0294 56 0.0019 0.0293 57 0.0019 0.0290 58 0.0019 0.0289 59 0.0019 0.0288 60 0.0019 0.0288 61 0.0019 0.0287 62 0.0019 0.0287 63 0.0019 0.0284 64 0.0018 0.0283 65 0.0018 0.0283 66 0.0018 0.0283 67 0.0018 0.0282 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 August 29, 2024 Section III, Page 21 68 0.0018 0.0282 69 0.0018 0.0282 70 0.0018 0.0280 71 0.0017 0.0279 72 0.0017 0.0278 73 0.0017 0.0277 74 0.0017 0.0275 75 0.0017 0.0275 76 0.0017 0.0273 77 0.0017 0.0266 78 0.0017 0.0257 79 0.0017 0.0253 80 0.0017 0.0253 81 0.0016 0.0246 82 0.0016 0.0246 83 0.0016 0.0245 84 0.0016 0.0241 85 0.0016 0.0240 86 0.0016 0.0235 87 0.0016 0.0234 88 0.0016 0.0232 89 0.0016 0.0230 90 0.0016 0.0229 91 0.0016 0.0229 92 0.0015 0.0229 93 0.0015 0.0228 94 0.0015 0.0225 95 0.0015 0.0225 96 0.0015 0.0220 97 0.0014 0.0220 98 0.0014 0.0219 99 0.0014 0.0218 100 0.0014 0.0217 101 0.0014 0.0216 102 0.0014 0.0216 103 0.0014 0.0213 104 0.0013 0.0211 105 0.0013 0.0209 106 0.0013 0.0206 107 0.0013 0.0205 108 0.0013 0.0205 109 0.0013 0.0204 110 0.0013 0.0202 111 0.0013 0.0202 112 0.0013 0.0196 113 0.0012 0.0194 114 0.0012 0.0192 115 0.0012 0.0192 116 0.0012 0.0192 117 0.0012 0.0191 118 0.0012 0.0191 119 0.0012 0.0189 120 0.0011 0.0189 121 0.0011 0.0187 122 0.0011 0.0185 123 0.0011 0.0183 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 August 29, 2024 Section III, Page 22 124 0.0011 0.0179 125 0.0011 0.0175 126 0.0010 0.0175 127 0.0010 0.0173 128 0.0010 0.0171 129 0.0010 0.0171 130 0.0010 0.0170 131 0.0009 0.0170 132 0.0009 0.0167 133 0.0009 0.0165 134 0.0009 0.0163 135 0.0009 0.0162 136 0.0009 0.0162 137 0.0009 0.0162 138 0.0009 0.0160 139 0.0009 0.0159 140 0.0009 0.0159 141 0.0008 0.0159 142 0.0008 0.0157 143 0.0008 0.0154 144 0.0008 0.0152 145 0.0007 0.0151 146 0.0007 0.0151 147 0.0007 0.0141 148 0.0007 0.0132 149 0.0006 0.0131 150 0.0006 0.0119 151 0.0006 0.0118 152 0.0005 0.0118 153 0.0004 0.0112 154 0.0004 0.0109 155 0.0002 0.0100 156 0.0001 0.0095 157 0.0001 0.0072 LID Duration POC #1 The Facility PASSED The Facility PASSED. Flow(cfs) Predev Mit Percentage Pass/Fail 0.0001 589038 64684 10 Pass 0.0001 569219 64519 11 Pass 0.0002 548190 64354 11 Pass 0.0002 530849 64299 12 Pass 0.0002 511967 64189 12 Pass 0.0002 496223 64078 12 Pass 0.0002 479212 63968 13 Pass 0.0002 465119 63803 13 Pass 0.0002 449650 63693 14 Pass 0.0002 436824 63528 14 Pass 0.0002 422951 63418 14 Pass 0.0002 411501 63308 15 Pass 0.0002 398784 63198 15 Pass 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 August 29, 2024 Section III, Page 23 0.0002 387994 63088 16 Pass 0.0002 376268 62977 16 Pass 0.0003 366304 62812 17 Pass 0.0003 355404 62702 17 Pass 0.0003 346376 62592 18 Pass 0.0003 337513 62482 18 Pass 0.0003 327769 62317 19 Pass 0.0003 319567 62207 19 Pass 0.0003 310538 62097 19 Pass 0.0003 302831 61987 20 Pass 0.0003 294299 61876 21 Pass 0.0003 287197 61711 21 Pass 0.0003 279380 61601 22 Pass 0.0003 272719 61491 22 Pass 0.0003 265287 61381 23 Pass 0.0004 259011 61326 23 Pass 0.0004 251965 61161 24 Pass 0.0004 246075 61051 24 Pass 0.0004 239524 60941 25 Pass 0.0004 234019 60831 25 Pass 0.0004 228073 60720 26 Pass 0.0004 222843 60610 27 Pass 0.0004 217063 60500 27 Pass 0.0004 212054 60390 28 Pass 0.0004 206604 60280 29 Pass 0.0004 202034 60170 29 Pass 0.0004 196915 60005 30 Pass 0.0004 192621 59895 31 Pass 0.0004 187776 59785 31 Pass 0.0005 183758 59674 32 Pass 0.0005 179133 59564 33 Pass 0.0005 175225 59454 33 Pass 0.0005 170931 59344 34 Pass 0.0005 167243 59234 35 Pass 0.0005 163169 59069 36 Pass 0.0005 159701 58959 36 Pass 0.0005 155847 58849 37 Pass 0.0005 152544 58739 38 Pass 0.0005 148911 58629 39 Pass 0.0005 145883 58518 40 Pass 0.0005 142415 58408 41 Pass 0.0005 139387 58353 41 Pass 0.0006 135974 58243 42 Pass 0.0006 133111 58133 43 Pass 0.0006 129974 58023 44 Pass 0.0006 127386 57913 45 Pass 0.0006 124744 57858 46 Pass 0.0006 121881 57748 47 Pass 0.0006 119404 57638 48 Pass 0.0006 116651 57472 49 Pass 0.0006 114284 57417 50 Pass 0.0006 111642 57307 51 Pass 0.0006 109440 57197 52 Pass 0.0006 106963 57087 53 Pass 0.0006 104816 56977 54 Pass 0.0007 102448 56867 55 Pass 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 August 29, 2024 Section III, Page 24 0.0007 100412 56757 56 Pass 0.0007 98155 56647 57 Pass 0.0007 96173 56537 58 Pass 0.0007 94026 56426 60 Pass 0.0007 92264 56371 61 Pass 0.0007 90172 56261 62 Pass 0.0007 88411 56151 63 Pass 0.0007 86484 56041 64 Pass 0.0007 84887 55931 65 Pass 0.0007 83016 55876 67 Pass 0.0007 81419 55766 68 Pass 0.0007 79658 55656 69 Pass 0.0007 78171 55546 71 Pass 0.0008 76465 55436 72 Pass 0.0008 74978 55381 73 Pass 0.0008 73382 55270 75 Pass 0.0008 71951 55160 76 Pass 0.0008 70409 55050 78 Pass 0.0008 69143 54957 79 Pass 0.0008 67712 54841 80 Pass 0.0008 66446 54742 82 Pass 0.0008 65014 54648 84 Pass 0.0008 63858 54560 85 Pass 0.0008 62427 54467 87 Pass 0.0008 61216 54362 88 Pass 0.0008 59950 54263 90 Pass 0.0009 58904 54175 91 Pass 0.0009 57693 54070 93 Pass 0.0009 56702 53977 95 Pass 0.0009 55491 53872 97 Pass 0.0009 54483 53762 98 Pass Passes up to 50% of the 2 year peak flow as required. 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 36.20 N 84.89 Total Volume Infiltrated 36.20 0.00 0.00 84.89 0.00 0% No Treat. Credit Compliance with LID Standard 8 250 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 August 29, 2024 Section III, Page 25 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. 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 August 29, 2024 Section III, Page 26 Flow Control Check: WWHM2012 PROJECT REPORT Project Name: 08.27.2024 FC Check Site Name: Mathay Ballinger Park Site Address: 24102 77TH PL W City : EDMOND Report Date: 8/27/2024 MGS Regoin Puget East Data Start 1901/10/1 Data End : 2058/09/30 DOT Data Number: 03 Version Date: 2023/01/27 Version : 4.2.19 Low Flow Threshold for POC 1 : 50 Percent of the 2 Year High Flow Threshold for POC 1: 50 year I:l ziDI93DWDo1[67:7DIBIB Rz&qMi'W* Name : Basin 1 Bypass: No GroundWater: No Pervious Land Use C, Forest, Flat C, Forest, Mod C, Pasture, Flat C, Pasture, Mod Pervious Total Impervious Land Use PARKING FLAT Impervious Total Basin Total Element Flows To: Surface MITIGATED LAND USE Name : Basin 1 Bypass: No C CM ENGINEERING acre .099 *Existing tree canopy .034 .071 *Existing lawn/pasture .14 0.344 acre 0.054 *Existing parking lot 0.054 0.398 *Total project area Interflow Groundwater 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 August 29, 2024 Section III, Page 27 GroundWater: No Pervious Land Use C, Pasture, Mod C, Pasture, Flat Pervious Total Impervious Land Use ROOF TOPS FLAT SIDEWALKS FLAT SIDEWALKS MOD PARKING FLAT patching Impervious Total Basin Total acre .062 *Amended Lawn .077 0.139 acre 0.004 *New restroom 0.084 *New walkway 0.08 *New walkway 0.082 *New & existing parking and pavement 0.25 0.389 Element Flows To: Surface Interflow Groundwater ANALYSIS RESULTS Stream Protection Duration Predeveloped Landuse Totals for POC #1 Total Pervious Area:0.344 Total Impervious Area:0.054 Mitigated Landuse Totals for POC #1 Total Pervious Area:0.139 Total Impervious Area:0.25 Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.019547 5 year 0.027366 10 year 0.033358 25 year 0.041921 50 year 0.049063 100 year 0.056898 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.077938 5 year 0.105391 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 August 29, 2024 Section III, Page 28 10 year 25 year 50 year 100 year 0.125869 0.154495 0.177907 0.203188 0.203188 - 0.056898 = 0.14629 < 0.15 cfs CM 250 4th Avenue South, Suite 200 Edmonds, WA 98020 ENGINEERING ph.425.778.8500 1 f.425.778.5536 www.cgengineering.com SE 1 /4, SE 1 /4, SECTION 31, TOWNSHIP 27 NORTH, RANGE 4 EAST, W.M. 4 - - -� -h - '- - -i Y r 24 -// 1 �� / , ' 26 TEMPORARY EROSION CONTROL PLAN NOTES: I l / b%/ iI -' - / J /' F 1. BEFORE BEGINNING LAND -DISTURBING ACTIVITIES, INCLUDING CLEARING AND GRADING, CLEARLY CB RIM=337.76 / MO EX13i GRAVY/ 28" 26 /12" MARK ALL CLEARING LIMITS. IE 12 RCP(NW)=335.86 1 /' \-1/--1 l ' F F / M 2. ALL DISTURBED PERVIOUS AREAS ON AND OFF -SITE SHALL BE COMPOST -AMENDED PER DETAIL F ' 6/C3.2. ALL DISTURBED AREAS SHALL BE COMPOST AMENDED PER 2019 SW MMW W BMP T5.13. E 12" RCP(SE)=335.76 x ;y'r ;' / ` ,` 22" / J/ ' g _ _' _ •_ _ \/' F 3, SOILS MUST BE STABILIZED AT THE END OF THE SHIFT BEFORE HOLIDAY OR WEEKENDIF NEEDED CB R1M=3,d71 I lPd� "����� - - -! � - - "," - �16" F I\\ ONTHE WEATHERFORECAST. p p / /- " \\ / 14 X2 ` / 4. CONCRETE TRUCKS MUST NOT BE WASHED OUT ONTO THE GROUND, OR INTO STORM DRAINS, E 12 /RCP NW-328.88 j \ / �JC - \,\§ / f L / - - - - - - ---•R_ \=\ / /' OPEN DITCHES, STREETS, OR STREAMS. EXCESS CONCRETE MUST NOT BE DUMPED ON -SITE. IE �� CPP(SW)=328.88 //- - - /' INSTTAL}/CATCH BASIFJ INSERT/-e /\I/' /' / '. F / 5. INSTALL CATCH BASINS INLET PROTECTION PER DETAIL 3/CL2 FOR ANY EXISTING INLETS WITHIN _ _ _/' / - /% /�1 , , 500' OFCONSTRUCrION SITE INTHE ROWANDAS PROPOSED DRAINAGE STRUCTURES ARE \ 34 INSTALLED UNLESS INLETS ARE PROTECTED BY A SEDIMENT TRAPPING BMP PER DOE SWMMWW Q ! ` J�L VOLUME II CHAPTER 3 BMP C220: INLET PROTECTION. Q , , J- - - - - i - - - - - - -, - - - - - �,� \ / 1 \� 6. ADDITIONAL BMPS MAY BE REQUIRED DURING CONSTRUCTION. CB RIM=327.80 // �0 / / I F ' _' ry _' _ 4. 2_ _ ,�/' 1 26 // 7. INSTALLAND MAINTAIN ALLTESC MEASURES ACCORDING TO APPROVED PLANS, CITY OF ( )- /-'-//�L�ljTi % /,` �C \\ 1 /' EDMONDS STANDARD DETAILS, AND ALL OTHER MEASURES THAT MAYBE REQUIRED DURING IE 12" CPP NE-324.68 / ,?5" IE 12" PVC(SW)=324.68 / C,PASTURE e \ /' M CONSTRUCTION. / IE CRARY CONSTRUCTIO E ANCE B. SOIL LOG LOCATIONS ARE APPROXIMATE AND SHOWN PER THE GEOTECHNICAL REPORT CREATED / MOD, 0.14 AC /� C2. \\Z� BY NGA. SEE SHEET C3.1. 1 \ 9. BMP C235 WATTLES ARE TO BE USED IN AREAS OF NEEDED IMMEDIATE EROSION PROTECTION, ON ,v>� / /y,,%U'/ IW I/' \\ ' ,"_/L I \\ EXPOSED SOILS DURING A PERIOD OF SHORT CONSTRUCTION DELAYS, OR OVER WINTER MONTHS, - -/ /'.6�'/2�" ANDON SLOPESREQUIRING STABILIZATION UNTIL PERMANENT VEGETATION CAN BEESTABLISHED �^, + // // , ,/ //' \\ 44 (/C2.2).SEE 2019SWMMWWSECTION VOLUMEII CHAPTER3, PAGE377 FORADDITIONAL V �4 q TP-4 I / / � \ //' - - -\ \� INFORMATION. BQ / /' \\\ / F I� F\\\\ F ' TREE PROTECTION NOTES: / SHED / Cj,GT -/ J� / ,/ 14 \33" I I �?� 1. THE APPLICANT MAY NOT FILL, EXCAVATE, STACK OR STORE ANY EQUIPMENT, OR COMPACTTHE ` / = /f BIKE > 95, 481 SF F EARTH IN ANY WAY WITHIN THE AREA DEFINED BYTHE DRIP LINE OF ANY TREE TO BE RETAINED. Po C FOREST MOD RACK 0, �,/ 0.034 AC " '/50 �1 oo4oL� w'/// /\ 2. OF APPLICANTSHALLDOTS. NAND MAINTAIN N,THEAPPLICAN SHALLPROVIDERS ON THE DRIP LINEOISION BALES , ' \ / _, ��� OF HAY TO PROTECT ROOTS. IN ADDITION, THE APPLICANT SHALL PROVIDE SUPERVISION /` SHED \ _ _ �/ _ ' / z - WHENEVER EQUIPMENT OR TRUCKS ARE MOVING NEAR TREES. /' / , , , -,i �� F INSTALLHIGH VISIBILITY PLASTIC \ / YL(/1[//1/� �i�/ /-��j`-/- -i / - - - ,/ x FENCI NG TO MARK LIMITS OF 1 Q 3. IF THE GRADE LEVEL ADJOINING ARETAINING TREE IS TO BE RAISED OR LOWERED, THE APPLICANT CB RIM=326.19 / r- ; "s' p / /. �. y. , `\ CLEARING AND GRAYING C2. SHALL CONSTRUCT DRY ROCK WALL OR ROCK WELL AROUND THE TREE. THE DIAMETER OF THIS E 12 PVC(NE)=323.39 / \ 32' (q/��� 'i I WALL OR WELL MUST BE EQUAL TO THE TREE'S DRIP LINE. E 12 RCP(S)=323.39 /4 4. THE APPLICANT MAY NOT INSTALL GROUND -LEVEL IMPERVIOUS SURFACE MATERIAL WITHIN THE t\ AREA DEFINED BY THE DRIP LINE OF ANY TREE TO BE RETAINED. 5. THE GRADE LEVEL AROUND ANY TREE TO BE RETAINED MAY NOT BE LOWERED WITHIN THE ,� S / n6 ,/' ,?`K / y�\\ '7,, ! CjI�O�.� GREATER OF THE FOLLOWING AREAS: THE AREA DEFINED BY THE DRIP LINE OF THE TREE, OR IBI / / //� / fl vl /� ;.,/ i % 'y0J ,// r �Y �� AN AREA AROUND THE TREE EQUAL TO ONE FOOT IN DIAMETER FOR EACH ONE INCH OF TREE I� p, CALIPER. / /// �O 0 o? 6. THE APPLICANT MAY PRUNE BRANCHES AND ROOTS AND WATER AS HORTICULTURALLY 'g IEGOVE RAMP _`\ �� /' � II .. .�1 AAPPROPRIATE FOR ANY TREES AND GROUND COVER WHICH ARE TO BE RETAINED. / I 1 '\ /i PINY AREA /' .0• +Fv 48 STAIRS N' a CQ SCR ET�E 0' �4 / F,- INSTI+.. FENCE C2.. A�\ ,,,/i// /'^lam/% / ��I /-\\ i' /, ///' ���•� 1 / ° / /�' i1 Q DEC C,PASTURE FLAT, 0.071 AC _ ..PIT-1 + rP � FENCE CDR. 0.3'(N) OF CORNER %``- " - ` E%ISTI '" k z C,FOREST FLAT, 42 , \\�I// \ O G STORM PIP OBE HH/ C3.1 FO REROUTE/, 16 p 0.099 AC 14" CB RIM=319.8'' IN6TALLSILTFE CE DEC DEC I C91 SD LOT 00100 ca IE 2" PVC(W)=319.42 i d �- /'/'//',�, INSTALL HIGH VISIBILITY PLASMIC FENCING TO MARK LI 1R OF C] 5 CLEARING AND C .DING �� /�Q / C IV1`- 38 00 / f PARKING FLAT, / RECOCATF♦STGN�RIC5.1 26 Hoof E 2" PVc(E)=319.� 00491100000803 0.054 AC �/ �ZG 14 ASPHALT \ \\ // INSSTALL CATCH♦BRSIN T r BASKET B..,,HH LL I \? / / Tp- ♦ C21 16 / SD / _ / , l i \ \9 STOCKPTICCOVERIN W/PLASTIC COVERING PER DOE BMP Cl\ � \ SD M 36 F L CATCH BASIN INSERT TREETO'BEREMOVZ" RIM=320.27 \ \ \INSTA \2 COULD NOT OPEN _____ \TI I _ N 8� 2 E 76' C \ 135.88'(P ( ) \ CB R1M_-_320_27 INSTALL CATCH BASIN INSERT \z C2 I 0.8' CB RIM=320.60 e . I n :, '. IE 12" RCP(N)=318.72 E 12" PVC(S) =318.70 IE 4" PVC(E)-319.32 CATCH BASIN TO BE REPLACED I LOT 4 I �5' I 0' 30' I JTEMPORARY EROSION CONTROL PLAN WARNER ADDITION I ' 1 SCALE: 1" = 20' �J 20 0 111 0 2011 40 BLD2023-1391 APPROVED FOR CONSTRUCTION CITY OF EDMONDS DATE: BY: CITY ENGINEERING DIVISION ENGINEERING 250 4TH AVE. S., SUITE 200 EDMONDS, WASHINGTON 98020 PHONE (425) 778-8500 FAX (425) 778-5536 FOR REPORT USE ONLY DESIGN: JCO DRAWN: ATD CHECK: JPU JOB NO: 23072.001 DATE: 10/27/23 J C) Z Y a � w - cn cn N w O U w Do W c� a rn Za a J Elf Q m Do 0 Z 2 00 Z O Q a 0 w :2 N LJ [-- E y SHEET C2.1 SE 1 /4, SE 1 /4, SECTION 31, TOWNSHIP 27 NORTH, RANGE 4 EAST, W.M. -; / rr GRADING AND UTILITY PLAN NOTES: CB RIM=337.76 3}6:8D - - -/- - - +26" 26"11 1 / / /12 1. SOUS REPORT E 12" RCP(NW)=335.86 _ _ _' - - 1 / / / / / I F / �\ REPORT D BY: LANDAU ASSOCIATES �+ I„� y/ , _ _ , 1F _ _ / PREPARED JU: E2023 ASSOCIATES IE 1j RCP(SE)-335.76 x / - / / j/// 0 1 22 / GATED: 23 JUNE 2023 UI - ` - /' F 2. AMINIMUM OF 3' HORIZONTAL SEPARATION AND VVERTICAL SEPARATION 15 REQUIRED CB RIM=33671 -_ / s % 3 - /// 16 F \\ BETWEEN DRY UTILITIES (POWER, GAS, PHONE, CABLE, ETC) AND SEWER, WATER AND STORM, " " - -/ - - - JF " " 1 / 14 X� \ , AND A MINIMUM OF 5' HORIZONTAL SEPARATION AND V VERTICAL SEPARATION FROM ANY E 1�2'j,%ICP(NW)=328.88 / / / `J/ - _F-_. \ / ` / CITY -OWNED LINES. IE 14 CPP(SW)-328.88 'EXIST CB­ -26'/ \�\I// \ /' 3. ALL DISTURBED AREAS TO BE COMPOST AMENDED PER 20195WMMWW BMPT5.13. SEE / RIM: 330.71- - i - - /- - / - - / DETAIL 6/C3.2. / FI-1E(12"NWI: 328.88-/ - rr - - - - /" - // - L� // 1 , / IE(12"SW): 328.88' - A: Y3q- _ - - - -/ i! -'= �'\\ / 11 34' / / 4. ATVPE II MANHOLE IS REQUIRED WHENEVER RIM TO INVERT EXCEEDS S'. foe " "ij / _ BRING TO GRADE 4V/RISERS, , 5. AMINIMUM OF 2'OF COVER IS REQUIRED FOR ALL PIPES LOCATED UNDER DRIVABLE p �A, O / fj�J �- / - i - - INST LL SOLID LID ON EXISTING CB CB RIM-327.80 // VVO / _/ _ y / F SURFACES AND I'OF COVER UNDER LANDSCAPE AND OTHER HARD SURFACES. / V•' .110 F ,, - - -- /,/ �C� \\ 11 // ' 6. TOTAL NEW REPLACED HARD SURFACES: 9,694 SF. IE 12 CPP IE=324.68 'A ,- / / /t r / IE 12' PVC(SW)=324.68// ' - - - -/�- J Q 3 \ ice` \ \ // ,� - NEW ASPHALT FPORTION IM ROUTED TO8NFILTR 33 INFILTRATION TRENCH 12, REMATO I INING FILTRATION#1, Gj \� 1,200SES INFILTRATION ROUT TRENCHES. EQUIVALENT F OF EXISTING 2,4555E BYPASSESO INFILTRATION RENCH.EQUIVALENT ^'2,5005F OF E%ISTING ASPHALT \�2� ROUTED TO INFILTRATION TRENCH#2. NEWROOF: 190 SF. RUNOFF ROUTED TO INFILTRATION TRENCH#2. 44 - N EW CONCRETE PAVEMENT: I,116SF.1,044SFPORTION ROUTED TO INFILTRATION #1, //�jJ, �'. ,, r�(�"yq�� / TPa /� // \\ ,' _\ \�// `l 725F PORTION ROUTEDTO INFILTRATION TRENCH#2. /� / _'-\\/ '/_'WIDE 6RA55 LINED DITCH Bw / / \\\ ' / F F \'LLAII".//7•\\ F NOTE: BOTH INFILTRATION TRENCHES SIZED FOR ALL PROPOSED HARDSCAPE AREAS CONCRETE PADS: 0.024 AC '/ INCLUDING25% RETROFIT AND BYPASS AREAS. BYPASS AREAS ARE TO FLOW ALONG �+ r \ _ '/_ / �_ RUNOFFTOCBAND / GRILL A \ ' / 26"I 1✓Y \ NATURAL DRAINAGE PATH AND INTO THE CITY M54AS INDICATED ON PLANS. PORTIONS / �� 95,481 j\,3,3' OF EXISTING HARDSCAPE TO FLOW TO INFILTRATION TRENCHES. r i- / RACK ' ' S0" y �. ' / 2 04310�4� QQ' GRADING QUANTITIES HED / // /` ' / - -- / \ __-� TOTAL EXCAVATION 10 CU VDS TOTAL / /- - - - !- /- - -/-/ - - -J% �/ F \/ / , 1 EMBANKMENT(FILL)- 340 CU VDS CB RIM=326.19 G TOTAL 350 CUYDS IE 12 PVC(NE)-323.39 / q / /�- -,/-, -/ - _ \ 32' y�/ /// / THE QUANTITIES SHOWN ABOVE ARE FOR THE PERMIT PROCESS IE 12 RC1P(S)=323.39 /�\3 '/� / ,,/, /ji/ / / F �/ / '- J// �\_ /' i ONLY. THESE VALUES ARETIMATIIMATE.OUU NOT USE FOR �' / ' ..66"" BIDDING, PAYMENT, OR ESTIMATING PURPOSES. '---- - PAVING LEGEND ' NEW ASPHALT/UTILITYSAWCUT r RETROFIT: 0.012 AC � OVERLAY EXISTING ASPHALT /{' ��' " 4 `/ �11V` NEW CONCRETE PLAY AREA // //- �F,` `j �.Y l / // / ,.' -/ - / GjO //i• ' 325.60 323.56 ^2.5 WIOE GRA55 LINED DITCH v �' STAIRS --a / / 31358 a COI.vCRE / /n ,,,VVV//^ \^7✓ 1/ , , , j� - TO DIRECT RUNOFF TO CB AND 325.a2 / /Fi.i/ IN IL I N�T�IENC 485 ✓� / / 324.25 � - `�2;3�- 37j AREAS INCLUDED FOR TRENCH #1 SIZING 324.05 323.20 44L "PVC@0.5% 323.1% SIDEWALK, FLAT: 0.036 AC - CONCRETE PADS 324.0 1, 323 a5 3f}.38 AND RETROFIT AREAS _ 323.28 _ � -- ----- SIDEWALK, MOD: 0.109 AC -WALKING PATH v FENCE 14'x3/, i s it / \ 136"x2 'L MAINTA�NC6VER� OF CORNER lj „'/>�42" /\ - ,'= 22.27/ AID�EPIPE WALKING PATH: 0.109 AC / \ �1y�y�{\\ Q /,/ 323.65 48 L//^'4\11DIP�4.0% / \\�v^/�� CONNECTO O \ z3.q�' 14» 'EXISTI B RIM=319.82 WALKING PATH: 0.038 AC .5 'WIDE RAS LINED DI CH ��� DEC D DIREC7RUNOFFTOCBAND /J } - \ 60LF RETROFIT: 0.015 AC VC(W)=319.42 \ l//✓/./ / \\-y / INFILT/RgTI�ON THE CH J°J 322.0 1�.'.✓J [I \ SOUTHERNORTION GRADING // ✓ - '7 / / Y / J EXIST OB / D DRAINAGE PLAN / O / \ C3. R / (n RIM: 320.3&_ i IE IT' PVC E): 3 00 \\ �26 IE (6" DIP 19.08 j ASPHALT \ �c� --- 4> „- __ E ,I CONCRETE PADS: 0.002 AC D NEW RESTROOM i F / TP- li �� -�-�� / i FFE:322.0 A vv - SD ' RESTROOM ROOF: 0.004 AC 1 22> PARKING: 0.029 AC , G 36" j11 - / PROPOSED PARKING, PAVEMEN i I� / S' I ZS" F ( ' CB RIM=320.27 \\ / PATCHING, AND PORTIONS OF I \ WALKWAY TO FLOW ALONG NATURAL DRAIN AGECOURSE TO TIC EXISTING Bsb� AREAS INCLUDED FOR TRENCH #1 SIZING CS _ \ 6' SAWCUT: 0.018 AC 321.34 320.60 321.07N 88°06'02 E 135. \ 135.88'(P) I J - ROOF TOPS, FLAT: 0.004 AC - RESTROOM ROOF CONNECTTO EXISTING STORM SIDEWALKS, FLAT: 0.048 AC - WALKWAYS, CONCRETE I ` 320.8PADS, RETROFIT AREAS 9 , Z�ZgS I I 30 PARKING, FLAT: 0.053 AC -PAVEMENT PATCHING AND I IIII /� ; PARKING _L - ----�--- -------------------------' GRADING AND DRAINAGE PLAN ' 1 SCALE: 1" = 20' �J 20 0 10 20 40 CATCH BASIN SCHEDULE MARK TYPE RIM ELEV INV ELEV NOTES CI TYPE 1 323.80 IS" S): 320.26 C3.3 C3.3 C3.3 �} TYPE 1 322.90 (I'N): 319.92 (6 W): 31982 2 3 4 C33 C3.3 C33 /_ TYPE 1 322.10 (6 E). 319.60 (6 S): 319.50 2 3 4 C3. C3.3 C3.3 <4�' �-/ TYPE 1 321.80 IS" S): 318.71 2 3 4 C3.3 C3.3 C3.3 < TYPE 320.40 (6'N): 318.69 IS" 5): 318.58 2 3 4 C3.3 C3.3 C3.3 (6) TYPE I 320.54 (12 W): 318.44 (6 E): 318.54 (4 N): 318.54 2 3 4 C3.3 C3.3 C3.3 (,7,1 TYPE 1 320.50 (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 � 47' x 10' x 2' 321.0 319.0 IE: IV PERF PVC): 319.50 IE: (4" DIP OVERFLOW): 321.0 5 C3.3 IE: IS" PVC, INLET, NW, N): 316.50 EYE 27' x 11' x 2' 320.0 318.0 IT (6" DIP, INLET, E): 318.50 IE: (6" PERF PVC): 318.50 C3.3 e IE: (4" DIP OVERFLOW): 320.0 BLD2023-1391 APPROVED FOR CONSTRUCTION CITY OF EDMONDS DATE: BY: CITY ENGINEERING DIVISION ENGINEERING 250 4TH AVE. S., SUITE 200 EDMONDS, WASHINGTON 98020 PHONE (425) 778-8500 FAX (425) 778-5536 FOR REPORT USE ONLY DESIGN: JCO DRAWN: ATD CHECK: JPJ JOB NO: 23072.001 DATE: 10/27/23 (W V w a 3: D_ Q J � cD w IN Q F- W U wo Q W c� _j a> z 0 J a Q m Do N Z Q 0 Z Z 2 O 0 < Q �LJ < :2 (V E y SHEET C3.1 SE 1 /4, SE 1 /4, SECTION 31, TOWNSHIP 27 NORTH, RANGE 4 EAST, W.M. CB RIM=337.76 / 3f°6:0 .../i....` 1 {126" 26„ ' F E 12" RCP(NW)=335.86 -' t _1_ - - />'12'^ _ E 12" RCP(SE)=335.76 ///. / .. 22 ' CB RIM=33671 J ' =� - / 116" F E 12'%RCP(NW)=328.88 %/ ii - F - - / 14"x2 �� L / _ \\ E 12/" CPP(SW)-328.88 'Ex1sTCB = f 26" / RIM: 3W.71 (12" NW):: 328.88 -j / rr 3 - 34' IE(12"SW): 328.88 -d -�. / i/. a,1 / YYYVVVJJJ �/--'3� M / >�- i - INS GLLOSOLID�I ONREXISSTTING CB \/ \ CB RIM=327.80 / p� ' / s 26"� / r " r /f /' 42 :,' F k E 12 CPP(NE)=324.68 '/D E 12" PVC(SW)=324.68/ / 2� 1-2 "2.5' WIi � CRASS LINED DITCH _ / A R A \ // i��+%///// / �/ _ / _ TO DIRECT RUNOFF TO CB AND / Ir�TII1 ' 26'"I vY SHED / GATE �/ ,> , ' f NFILTRATIONTRENCH \33' p� ��/ ��� / slat / 4_ 95,481 SF F2g o,� RACK ' S0" TIP 310040280�'�� < / r > SHED CB RIM=326.19 X/z, r--- / �GA1E32 ,' IE 12" PVC(NE)=323.39 F / IE 12" RCP S =323.39CD /- PV n 9 C. /T,3234p / , • ♦•♦-P, 1 PLAY AREA • ♦ • F /'I- S>� \� _ _ I �r / ' 325.60 323.56 a e♦ • • � -Iz.Sw1DeGaisSLmODo1TCH 4 STAIRS�� �' 358, COCRFT� ••�� �\ DIRECT RUNOFF TO CB AND-32 P\� O / / NIL NET NC C PASTURE MOD 0.062 AC F 4�8 s�; //'% ���� .• Ad/, / / / /324.85 7 ''.% / • ♦ / 3•DEC RETROFIT AREAS / �23 20 ` , 44 LF ^d0.5% 324.05 32 �323'4 3z4.oll \� �� sC• ��3ig.as �` --- ------ a A •� / ♦• B_ -- --- S ®IDEWALKS MOD, 0.08 AC ♦ PIT- CE /. /- -i ' f\^\J1'X2�i 'P1r ••♦� AINTA\ IN COVER OF . CORNER 36 /O.J l Vi - - / �,�', 22.27/ ABOVE PIPE 42 / /�d • 0 / 6s 48 L� a D'IP am z 2� 2.5' WIDE AS�'LINED DI CH TO DIREa UNOFF TO CB AND / ♦INFILT TION TREryCH Ip� C, PASTURE, FLAT, 0.077 AC ` / /' i 26 / \/i/-- `y' 34" � ♦ r SD / �� ♦ I I 11 / PROPOSED PARALrvG, PAVEMENT L Y AIL / PATCHING, A1IddD PORTIONS OF 0 I \ WALKWAY to FLOW ALONG ' \ NATURAL DRAINAGE COURSE TO 0 EXISTING CBS t 320. 321.34 I II I I II 320.89 0' II I i GRADING AND DRAINAGE PLAN \ 1 / SCALE: 1" = 20' i " DEC 0 � ' 3 .0 EXIST CB RIM: 320,38-' IE (2 PVC E): 319.43 IE 16' DIP N): 31909 IE(6 DIPS)' 3lW1,58nnD DEC _ I / CONNECTO EXISTING SUiO MT 60 LFLF ^ RI DIP 0a1 D.5% 00488�10010C ASPHALT NEW RESTROOM FFE:322.0 I I i 321.07 N 88°06'02" E 135. } I I I I ONNECTTO EXISTING STORM 1 I � I \ 00 SIDEWALKS FLAT, 0.084 AC _ 00 ' 00491100000803 28„� O CB RIM=319.82 RESTROOM AND ALL UTILITY STUB OUTS PREVIOUSLY COMPLETED BY OWNER. UTILITY STUB OUTS INCLUDE SEWER, WATER AND STORM CB RIM=320.27 COULD NOT OPEN E__________________________ �135.88'(P) li I ROOF TOPS FLAT, 0.004 AC LOT 4 PARKING FLAT, 0.082 AC (INCLUDES RETROFIT AREA WITHIN PROJECT CLEARING LIMITS) WARNER ADDITION VOL. 15, PO. 76 GRADING AND UTILITY PLAN NOTES 1. SOILS REPORT REPORT NUMBER: 074217.010 PREPARED BY: LANDAU ASSOCIATES DATED: 23 JUNE 2023 2. A MINIMUM OF 3' HORIZONTAL SEPARATION AND I' VERTICAL SEPARATION 15 REQUIRED BETWEEN DRY UTILITIES (POWER, GAS, PHONE, CABLE, ETC) AND SEWER, WATER AND STORM, AND A MINIMUM OF 5' HORIZONTAL SEPARATION AND V VERTICAL SEPARATION FROM ANY CITY -OWNED LINES. 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 V OF COVER UNDER LANDSCAPE AND OTHER HARD SURFACES. 6. TOTAL NEW REPLACED HARD SURFACES: 9,694 SF. - NEW ASPHALT PAVEMENT:8,388 SF.4,733 SF PORTION ROUTED TO INFILTRATION#1, 1,200 SF PORTION ROUTED TO INFILTRATION TRENCH 12, 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 TRENCH92. - NEW CONCRETE PAVEMENT:1,116 SF.1,044 SF PORTION ROUTED TO INFILTRATION#1, 72 SF PORTION ROUTED TO INFILTRATION TRENCH #2. NOTE: BOTH INFILTRATION TRENCHES SIZED FOR ALL PROPOSED HARDSCAPE AREAS INCLUDING 25% RETROFIT AND BYPASS AREAS. BYPASS AREAS ARE TO FLOW ALONG NATURAL DRAINAGE PATH AND INTO THE CITY M54 AS INDICATED ON PLANS. PORTIONS OF EXISTING HARDSCAPE TO FLOW TO INFILTRATION TRENCHES. GRADING QUANTITIES TOTAL EXCAVATION (CUT) - 10 CU YDS TOTAL EMBANKMENT (FILL) 340 CU YDS TOTAL 350 CU YDS THE QUANTITIES SHOWN ABOVE ARE FOR THE PERMIT PROCESS ONLY. THESE VALUES ARE APPROXIMATE. DO NOT USE FOR BIDDING, PAYMENT, OR ESTIMATING PURPOSES. PAVING LEGEND - NEW ASPHALT/UTILITY SAWCUT OVERLAY EXISTING ASPHALT NEW CONCRETE CATCH BASIN SCHEDULE MARK TYPE RIM ELEV INV ELEV NOTES CI TYPE 1 323.80 (6 S): 320.26 C3.3 C3.3 C3.3 �} TYPE 1 322.90 (6' N) 319.92 (6 W): 319.82 2 3 4 C3.3 C3.3 C3.3 /' TYPE 1 322.10 (6' E): 319.60 (6' S): 319.50 2 3 4 C3. C3.3 C3.3 <4�' �-/ TYPE 1 321.80 IS" S): 318.71 2 3 4 C3.3 C3.3 C3.3 < TYPE 320.40 16 N) 318.69 (6 5). 318.58 2 3 4 C3.3 C3.3 C3.3 <6> TYPE 320.54 (12 W): 318.44 (6 E): 318.54 (4 N) 318.54 2 3 4 C3.3 C3.3 C3.3 (�]) 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 47' x 10' x 2' 321.0 319.0 IE: (6" PERF PVC): 319.50 IE: (4' DIP OVERFLOW). 321.0 5 C3.3 IE: (6 PVC, INLET, NW, N): 319.50 EYE 27'x ll'x 2' 320.0 318.0 IF IS" DIP, INLET, E): 31850 IE (6" PERF PVC): 318.50 C3.3 e IE: (4' DIP OVERFLOW) 320.0 BLD2023-1391 APPROVED FOR CONSTRUCTION CITY OF EDMONDS DATE: BY: CITY ENGINEERING DIVISION o cm ENGINEERING 250 4TH AVE. S., SUITE 200 EDMONDS, WASHINGTON 98020 PHONE (425) 778-8500 FAX (425) 778-5536 FOR REPORT USE ONLY DESIGN- JCO DRAWN: ATD CHECK. JPU JOB NO: 23072.001 DATE: 10/27/23 (W V w a O Q J (D Ld N Q Q F- W U OOp Q W u j a> z 0 J a- m Do N Z Q 0 Z Z O 0 Q Q :2N�w C7W y SHEET C3.1 Mathay Ballinger Park— CG # 23072.20 August 29, 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 August 29, 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 August 29, 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 August 29, 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 August 29, 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. 3. Critical Areas Report dated June 03, 2024. CM 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 m _ L Oyu i - � • �� =Y � ','� ^ N� 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) - ~ 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 -a a)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 -a a)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 _ � o 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 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) 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 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 ti 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 v to D rn L/I ru D a �2 �F ,92 I�o �Q 70 Cn 'p m _ o Ln O D 77th PL W m :;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 � � n � 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 REOi'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 r0[a' [ on"".) wm7A) (� of xwc) wm=' f Ja=T-, JPSATM 242ND ST. S. W. ff( i I t r / � 1ESUR IAC[ SPDRT COURT MAf PAIN PICNIC SNEl,E1 _�.,,., �ia7p 0f0 C% �[r�^ I'y�RfSVRFAC[SPORT G➢VR[' 1 SITE PLAN SGLL ,• • w w a » Ro w CONS711FCi10F{.WSE 1L.. _....,.. _.. � •PEASE [ 1 $ PNAS[ 2 PAVING LEGEND N[W ASPHALTILMLTY UNCUT OVL RIAT (I STVIG 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 m Do 3 a ^0 CL Z m Q 0 ILL] M N W (/) =�EE7 CRITICAL AREAS REPORT GEOLOGICALLY HAZARDOUS AREAS MATHAY-BALLINGER PARK IMPROVEMENTS ZGA Project No. 2814.00 3 June 2024 Prepared for: City of Edmonds Prepared by: Z*ipperGeo Geoprofessional Consultants ZipperGeo Geoprofessional Consultants ZGA Project No. 2814.00 3 June 2024 City of Edmonds Parks, Recreation, and Human Services 700 Main Street Edmonds, Washington 98020 Attention: Mr. Kyle Woods, Planner & Capital Projects Manager Subject: Critical Areas Report Geologically Hazardous Areas Mathay-Ballinger Park Improvements 24105 78th Place West Edmonds, Washington City Permit No. BLD2023-1391 Dear Mr. Woods: In accordance with your request and written authorization, Zipper Geo Associates, LLC (ZGA) has completed this Critical Areas Report on behalf of the City of Edmonds (the City) for the above -referenced project. This report has been prepared in general accordance with Chapter 23.40.090 of the Edmonds Community Development Code (ECDC), our proposal number P24153, dated 29 April 2024, and our Professional Services Agreement with the City, dated 1 May 2024. This evaluation was limited to Geologically Hazardous Areas as defined in ECDC 23.80.020. We appreciate the opportunity to be of service to you on this project. If you have questions concerning this report, or if we may be of further service, please contact the undersigned. Respectfully Submitted, Zipper Geo Associates, LLC ogw Signed 6/3/24 355 v JEFFREY S. TINKLEPAUGH Jeffrey S. Tinklepaugh, LG, LEG Senior Engineering Geologist James P. Georgis, LG, LEG Principal Engineering Geologist 19019 36th Ave West, Suite E I Lynnwood, WA 98036 1 Phone: 425.582.9928 1 zippergeo.com ZipperGeo Geoprofessional Consultants TABLE OF CONTENTS Page INTRODUCTION........................................................................................................................................ 1 Purpose...................................................................................................................................................1 SiteLocation............................................................................................................................................1 ProjectUnderstanding.............................................................................................................................1 PreviousInvestigations by Others............................................................................................................2 PHYSICAL SETTING................................................................................................................................. 2 SurfaceConditions...................................................................................................................................2 GeologicSetting.......................................................................................................................................3 SubsurfaceConditions.............................................................................................................................3 GroundwaterConditions.........................................................................................................................3 GEOLOGICALLY HAZARDOUS AREAS.................................................................................................. 4 ErosionHazard Areas...............................................................................................................................4 LandslideHazard Areas............................................................................................................................5 SeismicHazard Areas...............................................................................................................................6 MitigationSequencing.............................................................................................................................7 CONCLUSIONS AND RECOMMENDATIONS.......................................................................................... 9 RELIANCE AND LIMITATIONS................................................................................................................. 9 REFERENCES........................................................................................................................................... 9 Appendix A — Figures Figure 1: Vicinity Map Figure 2: Site and Exploration Plan Appendix B — Landau Associates Soil Classification Procedures, Test Pit Logs, and Grain Size Testing Results 19019 36th Ave West, Suite E I Lynnwood, WA 98036 1 Phone: 425.582.9928 1 zippergeo.com CRITICAL AREAS REPORT GEOLOGICALLY HAZARDOUS AREAS MATHAY-BALLINGER PARK IMPROVEMENTS 24105 78T" PLACE WEST EDMONDS, WASHINGTON 3 June 2024 INTRODUCTION Purpose This report has been prepared by Zipper Geo Associates, LLC (ZGA) on behalf of the City of Edmonds (the City) in support of planned improvements to Mathay-Ballinger Park. This report has been prepared in general accordance with Chapter 23.40.090 of the Edmonds Community Development Code (ECDC), our proposal number P24153, dated 29 April 2024, and our Professional Services Agreement with the City, dated 1 May 2024. Our scope of services was limited to an evaluation of the presence/absence of Geologically Hazardous Areas as defined in ECDC 23.80 within the project area and recommendations for mitigating measures to reduce impacts to such critical areas, if necessary. Site Location Mathay-Bal linger Park is located at 24105 78th Place West, in Edmonds, Snohomish County, Washington (the Site). The Site is adjoined to the north and west by the Old Everett Traction Co. Right of Way and to the south and east by residential properties. The Site is accessed from the south from 78th Place West. The Site is located just over 1,000 feet to the west of Lake Ballinger. The location of the Site is depicted on Figure 1, Vicinity Map. Project Understanding ZGA was provided with a set of preliminary civil drawings for the Mathay-Ballinger Park Site Improvements, prepared by CG Engineering, revision dated 10 April 2024. From a review of these plans, we understand that the proposed site improvement will include: • Asphalt resurfacing of the existing parking area at the north end of 78th Place West; • Construction of new asphalt surfaces for additional parking spaces, walking paths, and maintenance access roads connecting 78th Place West to an existing asphalt -paved trail (the Interurban Trail) located to the north of the Site within the Old Seattle -Everett Traction Co. Right of Way; • Construction of a new single -stall restroom near the 78th Place West parking area; • Construction of new concrete pads for benches, picnic tables, and a new play area; • Minor regrading and fill placement; and • Utility improvements including new stormwater infiltration galleries and associated catch basins and below ground piping. Page 1 1 Critical Areas Report Geologically Hazardous Areas Mathay-Bal linger Park Improvements 3 June 2024 ZipperGeo Geoprofessional Consultants These improvements are generally depicted in Figure 2, Site and Exploration Plan. Previous Investigations by Others Our scope of services did not include a subsurface investigation. For the purposes of this report, we have utilized geologic information from readily available, published resources, our field observations from a site reconnaissance, and Site -specific subsurface data previously collected by Landau Associates. The results of Landau Associates previous geotechnical investigations are summarized in the following document: • Summary of Geotechnical Engineering Services, Moth ay -Ballinger Park Project, Edmonds, Washington, prepared by Landau Associates, dated 27 December 2023. According to this report, on May 24, 2023, Landau Associates advanced four test pits (TP-1 through TP-4) and completed one small-scale pilot infiltration test (PIT; PIT-1) at the Site, in the approximate locations indicated on Figure 2, Site and Exploration Plan. Test pits were advanced to depths of approximately 9 to 10 % feet below ground surface (bgs). PIT-1 was completed at a depth of approximately 3 feet bgs and was then extended to a depth of approximately 10 % feet bgs. Four soil samples (one from each test pit and from PIT-1) were submitted for grain size distribution and moisture content analysis. Landau Associates recorded their subsurface observations in test pit logs, which are enclosed in Appendix B. The results of moisture content analyses are presented on the boring logs. The results of grain size analyses are presented on a separate plot (Landau Figure 9), which is also enclosed in Appendix B. PHYSICAL SETTING Surface Conditions According to a survey by Pacific Coast Surveys, the park area is generally level with an overall gentle slope to the south and a total vertical relief of approximately 6 feet from elevation 328 feet above sea level (asl) near the north end of the park area to 322 feet asl near the parking area to the south. The Site includes portions of a steeper slope that adjoins the park to the north with a total vertical relief of approximately 6 to 10 feet with an asphalt -paved or gravel -surfaced trail located along the top of the slope. Slopes generally do not exceed 15% within the park area except for in limited, localized areas (15% represents a threshold slope within the ECDC for Erosion Hazard Areas). Slopes along the northern portion of the site, adjoining the trail, generally do exceed 15%, and in the westerly half of the Site often exceed 40% (40% represents a threshold slope within the ECDC for Landslide Hazard Areas). We conducted a reconnaissance of the Site on 8 May 2024. The majority of the park area is surfaced with grass. An asphalt parking area is located at the south end of the Site at the terminus of 781" Place Southwest. An asphalt sport court is located to the east of the parking area. A wood chip surfaced play Page 12 Critical Areas Report Geologically Hazardous Areas Mathay-Bal linger Park Improvements 3 June 2024 ZipperGeo Geoprofessional Consultants area is centrally located within the park. Numerous mature trees are scattered throughout the park. A gravel access road is located at the north end of the park extending up the slope and connecting to the paved portion of the Interurban Trail. Dense undergrowth consisting mainly of blackberries is located at the northeasterly end of the park and along the slope below the trail. We did not observe visible evidence of surface water, groundwater seepage, active erosion, or landsliding during our visit. According to the Natural Resources Conservation Service (NRCS) Web Soil Survey database', shallow soils at the Site belong to the Alderwood Series. Alderwood soils are generally described by the NRCS as gravelly, sandy loam derived from glacial drift deposits. Alderwood soils are recognized by the ECDC as prone to erosion when slopes exceed the 15% threshold. Geologic Setting Surficial geologic conditions for the Site are depicted on the Geologic Map of the Edmonds East and Part of the Edmonds West Quadrangles, Washington (Minard,1983). The surficial geology of the Site is mapped as Vashon Till (Qvt), which is generally classified as a poorly sorted (well graded), non -stratified mixture of clay, silt, sand, pebbles, and cobbles with occasional boulders. Unweathered Vashon Till typically exhibits an overall high density and low permeability, although layers or lenses of coarse grained sediment may occur within the unit. Also mapped in the vicinity of the site is the Vashon Recessional Outwash (Qvr) geologic unit, which is generally classified as stratified sand and gravel with minor silt and clay layers. Vashon Recessional Outwash typically exhibits a low to medium density and high permeability, although layers or lenses of fine-grained sediment may occur within the unit. Subsurface Conditions During test pit explorations, Landau Associates observed geologic conditions beneath the Site to depths of up to 10 % feet. According to their report and boring logs, subsurface conditions at the Site generally consist of 3 to 4 inches of topsoil over loose to medium dense or medium stiff, damp to moist, gray to light brown, sand with varying amounts of silt, gravel and cobbles to silt with varying amounts of sand, gravel, and cobbles. Landau Associates interpreted that these conditions were representative of the Vashon Recessional Outwash geologic unit described by Minard. All test pits were terminated within the Vashon Recessional Outwash unit. Groundwater Conditions Landau Associates reported that they did not observe groundwater within their field explorations. We expect that shallow groundwater beneath the Site generally flows towards Lake Ballinger (to the east) at a higher elevation than that of the water level within the lake. According to the City, the water level within ' https://websoilsurveV.nres.usda.gov/app/WebSoilSurveV.aspx Page 13 Critical Areas Report Geologically Hazardous Areas Mathay-Bal linger Park Improvements 3 June 2024 ZipperGeo Geoprofessional Consultants Lake Ballinger is typically below 280 feet2 asl except in flood conditions. 280 feet in elevation is approximately 40 feet below the lowest elevation at the Site. Therefore, the exact depth to groundwater below the Site is unknown but is expected to be greater than 10%feet and less than 40 feet. Groundwater levels should be expected to vary throughout the year depending on site use, precipitation rates, and local geologic conditions, with the highest groundwater levels generally occurring during late winter and early spring. GEOLOGICALLY HAZARDOUS AREAS ECDC 23.80.050(B) requires that a Critical Areas Report address geologically hazardous areas that are within the project area and all geologically hazardous areas within 200 feet of the project area or that have the potential to be affected by the proposal. Figure 2, Site and Exploration Plan, depicts the approximate extent of geologically hazardous areas identified by this assessment within the scope of the project's survey, provided by Pacific Coast Surveys. In addition to these areas, we reviewed portions of the King County West 2021 LiDAR digital elevation model, reviewed geologic hazard inventories from the Washington Geologic Information Portal (WGIP), and performed a site reconnaissance to assess the potential presence of geologically hazardous areas beyond the survey area. Our extended review did not identify geologically hazardous areas beyond the project survey bounds shown in Figure 2 that may adversely affect or be adversely affected by the proposed park improvements. Erosion Hazard Areas Erosion Hazard Areas are defined in ECDC 23.80.020(A) as those areas identified by the U.S. Department of Agriculture's Natural Resources Conservation Service as having a "moderate to severe," "severe," or "very severe" rill and inter -rill erosion hazard. Erosion hazard areas are also those areas impacted by shoreland and/or stream bank erosion. Within the city of Edmonds erosion hazard areas include: 1. Those areas of the city of Edmonds containing soils that may experience severe to very severe erosion hazard. This group of soils includes, but is not limited to, the following when they occur on slopes of 15 percent or greater: a. Alderwood soils (15 to 25 percent slopes); b. Alderwood/Everett series (25 to 70 percent slopes); c. Everett series (15 to 25 percent slopes); 2. Coastal and stream erosion areas which are subject to the impacts from lateral erosion related to moving water such as stream channel migration and shoreline retreat; https://www.edmondswa.gov/government/departments/public works and utilities/stormwater utility system/1 ake ballinger water level Page 14 Critical Areas Report Geologically Hazardous Areas Mathay-Bal linger Park Improvements 3 June 2024 ZipperGeo Geoprofessional Consultants 3. Any area with slopes of 15 percent or greater and impermeable soils interbedded with granular soils and springs or ground water seepage; and 4. Areas with significant visible evidence of ground water seepage, and which also include existing landslide deposits regardless of slope. Alderwood soils occur on the Site on slopes of 15% or greater. These areas therefore qualify as Erosion Hazard Areas. The approximate extent of Erosion Hazard Areas at the Site is depicted in Figure 2, Site and Exploration Plan. Planned Site improvements overlap with mapped Erosion Hazard Areas in the northern portion of the Site, where the access road will approach the existing paved asphalt trail, and in one other localized area to the south of the existing play area. Adverse effects of construction will be mitigated by implementingthe temporary erosion control measures outlined in Sheets C2.1 and C2.2 of the preliminary civil plan set. Permanent stormwater systems will be designed in accordance with the Stormwater Management Manual for Western Washington (Washington State Department of Ecology, 2019) and generally appear sufficient for the scope of site regrading and new impermeable surfaces. Permanent erosion control will be accomplished by revegetation of affected areas with appropriate ground cover or installation of erosion resistant surfacing. It is our opinion that conditions do not warrant a minimum setback from identified erosion hazard areas. Landslide Hazard Areas Landslide Hazard Areas are defined in ECDC 23.80.020(B) as areas potentially subject to landslides based on a combination of geologic, topographic, and hydrologic factors. They include areas susceptible because of any combination of soil, slope (gradient), slope aspect, structure, hydrology, or other factors. Within the city of Edmonds potential landslide hazard areas include: 1. Areas of ancient or historic failures in Edmonds which include all areas within the earth subsidence and landslide hazard area as identified in the 1979 report of Robert Lowe Associates and amended by the 1985 report of GeoEngineers, Inc., and further discussed in the 2007 report by Landau Associates; 2. Coastal areas mapped as class u (unstable), uos (unstable old slides), and urs (unstable recent slides) in the Department of Ecology Washington coastal atlas; 3. Areas designated as quaternary slumps, earthflows, mudflows, or landslides on maps published by the United States Geological Survey or Washington State Department of Natural Resources; 4. Any slope of 40 percent or steeper that exceeds a vertical height of 10 feet over a 25-foot horizontal run. Except for rockeries that have been engineered and approved by the engineer as having been built according to the engineered design, all other modified slopes (including slopes where there are breaks in slopes) meeting overall average steepness and height criteria should be considered potential landslide hazard areas); Page 15 Critical Areas Report Geologically Hazardous Areas Mathay-Bal linger Park Improvements 3 June 2024 5. Any slope with all three of the following characteristics: a. Slopes steeper than 15 percent; ZipperGeo Geoprofessional Consultants b. Hillsides intersecting geologic contacts with a relatively permeable sediment overlying a relatively impermeable sediment; and c. Springs or ground water seepage; 6. Any area potentially unstable as a result of rapid stream incision or stream bank erosion; 7. Any area located on an alluvial fan, presently subject to, or potentially subject to, inundation by debris flow or deposition of stream -transported sediments; and 6. Any slopes that have been modified by past development activity that still meet the slope criteria. The Site is not associated with nor in the vicinity of mapped landslide hazards per the Washington Geologic Information Portal (WGIP) landslide hazard inventory3. However, portions of the slope at the northwestern margin of the Site exceed 40% slope with a vertical height of over 10 feet and a horizontal run of at least 25 feet. These areas therefore qualify as Landslide Hazard Areas. The approximate extent of Landslide Hazard Areas at the Site is depicted in Figure 2, Site and Exploration Plan. Planned Site improvements are located downslope from Landslide Hazard Areas where they will not impart a surcharge load and are setback far enough from the toe of the slope that they are unlikely to reduce the lateral support of said slope. The risk that construction of the proposed Site improvements will have an adverse effect on the stability of nearby Landslide Hazard Areas is low. Additionally, proposed Site improvements do not include continuously occupied structures within the likely runout area of a landslide originating from the Landslide Hazard Areas identified in the vicinity. It is our opinion that conditions do not warrant a minimum setback from identified landslide hazard areas. In our opinion, no mitigation appears necessary. Seismic Hazard Areas Seismic Hazard Areas are defined in ECDC 23.80.020(C) as areas subject to severe risk of damage as a result of earthquake -induced ground shaking, slope failure, settlement, soil liquefaction, lateral spreading, or surface faulting. These areas are designated as having a "high" and "moderate to high" risk of liquefaction as mapped on the Liquefaction Susceptibility Map of Snohomish County by the Washington State Department of Natural Resources or areas located within landslide hazard areas. 3 Washington Geological Survey, 2023, Washington State Landslide Inventory Database-GIS data, June 2023: Washington Geological Survey Digital Data Series 29, version 1.1. https://fortress.wa.gov/dnr/geologydata/publications/data download/ger portal landslide database.zip Page 16 Critical Areas Report Geologically Hazardous Areas Mathay-Bal linger Park Improvements 3 June 2024 ZipperGeo Geoprofessional Consultants The Site is not located within an area designated as having a "high" or "moderate to high" risk of liquefaction. However, per ECDC 23.80.020(C), portions of the Site do qualify as Landslide Hazard Areas and therefore also qualify as Seismic Hazard Areas. The approximate extent of Seismic Hazard areas at the Site is depicted in Figure 2, Site and Exploration Plan. Planned Site improvements do not overlap with mapped Seismic Hazard Areas and the risk that construction of the proposed Site improvements will have an adverse effect on the stability of nearby Seismic Hazard Areas is low. In our opinion, no mitigation appears necessary. Mitigation Sequencing Per ECDC 23.40.120(A), applicants shall demonstrate that all reasonable efforts have been examined with the intent to avoid and minimize impacts to critical areas. Geologically hazardous areas in the vicinity of the proposed park improvements include erosion hazard areas, landslide hazard areas, and seismic hazard areas. The extents of these critical areas are depicted on Figure 2, Site and Exploration Plan. Per ECDC 23.40.120(B), when an alteration to a critical area is proposed, such alteration shall be avoided, minimized, or compensated for in the following sequential order of preference: 1. Avoiding the impact altogether by not taking a certain action or parts of an action; — The proposed site improvements avoid geologically hazardous areas to the extent practicable. Site improvements overlap with limited portions of erosion hazard areas near the existing park area and on the slope leading up to the Interurban Trail to the north. 2. Minimizing impacts by limiting the degree or magnitude of the action and its implementation by using appropriate technology or by taking affirmative steps, such as project redesign, relocation, or timing, to avoid or reduce impacts; — The proposed site improvements will utilize existing grades to the extent practicable and will cross the northerly erosion hazard area at a nearly perpendicular angle to minimize the amount of disturbance. — Project plans avoid surcharge loads or other modifications to the landslide/seismic hazard areas. 3. Rectifying the impact to wetlands, frequently flooded areas, and fish and wildlife habitat conservation areas by repairing, rehabilitating, or restoring the affected environment to the historical conditions or the conditions existing at the time of the initiation of the project; — The site is an active city park and it is our understanding that no wetlands, frequently flooded areas, and fish and wildlife habitat conservation areas are present. Page 17 Critical Areas Report Geologically Hazardous Areas Mathay-Bal linger Park Improvements 3 June 2024 ZipperGeo Geoprofessional Consultants — Permanent grades will be configured according to Sheet C3.1, Grading and Drainage Plan of Mathay-Bal linger Park Site Improvements (plans), prepared by CG Engineering, dated 10 April 2024 4. Minimizing or eliminating the hazard by restoring or stabilizing the hazard area through engineering or other methods; — Project plans include appropriate stormwater control measures — Project plans include permanent erosion control measures in the form of revegetation of affected areas with appropriate ground cover or installation of erosion resistant surfacing. — Project plans include temporary erosion control measures during construction. — Clearing and grading will be conducted during the dry season (roughly May 1 to October 1 per ECDC 23.80.070(A)(6)). 5. Reducing or eliminating the impact or hazard over time by preservation and maintenance operations during the life of the action; — Site improvements will be maintained in general accordance with City of Edmond Park Department Standards of Practice. 6. Compensating for the impact to wetlands, frequently flooded areas, and fish and wildlife habitat conservation areas by replacing, enhancing, or providing substitute resources or environments; and/or — Not applicable. 7. Monitoring the hazard or other required mitigation and taking remedial action when necessary. — Geotechnical construction monitoring will occur on an on -call basis during construction. These visits will include observations by a Certified Erosion & Sediment Control Lead (CESCL)-certified individual. Page 18 Critical Areas Report Geologically Hazardous Areas ZipperGeo Mathay-Bal linger Park Improvements GeoprofessionalGonsultants 3 June 2024 Cd010141ILIM[QLIPT_1►11111X4101LTA IAi140101_A1111[001.1 Portions of the Site and its vicinity qualify as Geologically Hazardous Areas per ECDC 23.80. These areas are depicted in Figure 2, Site and Exploration Plan. Based on our conceptual geologic model of the Site and our review of the preliminary civil plan set, it is our professional opinion that the risk that construction of the planned Site improvements will have an adverse effect on the stability of nearby Geologically Hazardous Areas is low. It is our opinion that conditions do not warrant a minimum setback from identified landslide or erosion hazard areas. Mitigating measures will include temporary erosion control during construction as outlined in Sheets C2.1 and C2.2 of the preliminary civil plan set. Based on our review, the proposed temporary erosion control measures appear sufficient. No further mitigation appears warranted in our opinion. RELIANCE AND LIMITATIONS This report is an instrument of service and has been prepared for the exclusive use of the City of Edmonds in accordance with generally accepted engineering geology practice for specific application to this project and site location. Our scope of services did not include a subsurface investigation. We assume that information provided by others is accurate and complete. No warranty, express or implied, is made. Technical Memorandum, Summary of Geotechnical Engineering Services, Mathay-Ballinger Park Project, Edmonds, Washington, prepared by Landau Associates, dated 27 December 2023. Critical Areas Determination, prepared by the City of Edmonds, dated 30 August 2024. DLD2023-1391, 24105 78th Place West, Fill/Grade — Mathay Ballinger Park, prepared by the City of Edmonds, dated 17 November 2023. City of Edmonds Community Development Code, revision dated 5 March 2024. Mathay-Bal linger Park Site Improvements (plans), prepared by CG Engineering, dated 10 April 2024. Geologic Map of the Edmonds East and Part of the Edmonds West Quadrangles, Washington, 1:24,000 scale, US Geological Survey Miscellaneous Field Studies Map MF-1541, prepared by Minard, J.P., dated 1983. Page 19 Critical Areas Report Geologically Hazardous Areas Mathay-Bal linger Park Improvements 3 June 2024 ZipperGeo Geoprofessional Consultants Appendix A Figures Page 1 10 53 it �, -.. -,&: r a -1�s L r -7 „ APPROXIMATE PROJECT AREA 0 '' ► ice+ �� _ �� -s REFERENCE: 2022 AERIAL PHOTOGRAPH, ACQUIRED FROM SNOHOMISH COUNTY ONLINE PROPERTY INFORMATION PORTAL. N•E , , ., CB RIM=339.44 - 10' / 30' M / 0EC 1 % M IE 12" RCP(SE)=336.39 / l / / /F 34' - - - �2? �/ 25' f� 0�� 28" / /t. B 26• CB RIM=337.76 26• /12' F s• j / IE 12" RCI=335.86 / / / / I F F / M /// JDECI � IE �12' RCI (S 335.7s I ^ / / / _ // ! �• / / / 7) I CB RIM= 36.71 _ L _ / / 8 6• 14'x2 l \ 'M / IE 12" P(NW)=328.88 /F / 1/ IE ,11/' CPP SW=328.88 E / //// ///I M,/ // CB RIM=327.80 / / j / 4' /'f F II 26" I 91100000804 IE 12' CPP(NE)_324.68 ' 60 0 30 60 IE 12' PVC(SW)=324.68 + / // S� F 28' SCALE IN FEET*, n /j// ' I /.: �// / \ / \M ��F----------1 T P-4 / / / / \ / F F YF� 4 F / 5 AR ` ' ' 26• SHED P j / // BIKE / / / 95,481 SF /X F SHED / Y " 2704310040280Q/ SHED //'/ // / F 10, CB RIM=326.19 / I IE 12' C(NE =323.39 0 • /i P(jS�/// / / IE 12" RCP(5;=323.39 �.% / / / // F / / / / � I 0049 Xx SrAIRSS 26 / .'•. A, 8• / DEC � + 10, _ __ / TP-1 PIT-1 // axt OFFFENCE 0.3(N) \ \ j/// , / / / �' M �3 HmH F 9' 14' DEC DEC / CB RW=319.82 \ /7� P� Y�� ? OT 1 . IE 2' PWM=319.42 \ 20'/ BACK) 00J4100100 NEW 20'x30' SLAB FOR PICNIC AREA \ 0049110 / 26 �(��/ / cl 00491100000803 \ /42 /F / j` 014" 695 nI �i / / /� NEW RESTROOM I u \ j / / / / F Q FFE: 322.0 I r \ m • 5'SETBACK C36" �329.05 / r RUCTURE SET�� I CO RIM=320.27 / 14' I I �- J �-- could Nor OPEN C M .6' / N as Os'02' E 135.78'(C) 1135.88'(P)EXISTING U. / / 7'-1 0.8, CB -r LANDSCAPING I I F .:': E 12" RCPSj 3I f72 IE 4' PIC(N)� 319.32 TO REMAIN LOT 4 E 12' PYC S)=318.70 IE 4' DIP(NW=319.32 I I Al 22 j l l 12' E 4' 1884 IE 12" DIP(W=319.32 I M / F g17f' / I I WARNER ADDITION 6 I LOT 2 I VOL. 15, PG. 76 / d CB RIM=319.44 LAKE &ILLINGER I I I CB RIM=319.89 I IE 12' M(N)=317.79 HOMESM ADD. I L 0.8' GPM I IE 12 RCP(S)=3/7.04 VOL 14, PG. 99 7. �- �-31`n IE 12' RCP((S94 318.I �, �-------- - - - - - - - - - I I I REFERENCE: SHEET C1.1, PRELIMINARY SITE PLAN, CG ENGINEERING, APRIL 10, 2024. FIGURE 2, SITE AND EXPLORATION PLAN, LANDAU ASSOCIATES, SUMMARY OF GEOTECHNICAL ENGINEERING SERVICES, DECEMBER 27, 2023. LEGEND TP-1 APPROXIMATE LOCATION AND ID OF TEST PIT (LANDAU, 2023) SPIT-1 APPROXIMATE LOCATION AND ID OF PILOT INFILTRATION TEST (LANDAU, 2023) EROSION HAZARD AREA PER ECDC 23.80.020(A) r LANDSLIDE/SEISMIC HAZARD L - - J AREA PER ECDC 23.80.020(B/C) THIS FIGURE IS MEANT TO BE VIEWED IN COLOR. GRAYSCALE REPRODUCTION MAY LEAD TO INCORRECT INTERPRETATION. Critical Areas Report Geologically Hazardous Areas ZipperGeo Mathay-Bal linger Park Improvements GeoprofessionalGonsultants 3 June 2024 Appendix 6 Landau Associates Soil Classification Procedures, Test Pit Logs, and Grain Size Testing Results Page 1 11 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) - ~ 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 -a a)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 -a a)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 _ � o 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 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) 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 Mathay Ballinger Park— CG # 23072.20 Drainage Report August 29, 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. CM 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 August 29, 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 below. 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 (BLD2023-1391) 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. EXISTING CATCH BASIN PROPOSED CATCH BASIN �0°/ -- -:-- - 47 x10 x2 INFILTRATION/ TRENCH SHED GA GRILL / /` - : �" " BIK / FO + RACK / 50 ° / 2 . O -�% - ------ ---- SHED - -/-_------ i F / rir / - f- I. /. .....� 0ti z ryry. PL4 AREA TAIRS .. NEW — 2s" CONVEYANCE / DITCH 4,x2�,/ /. DEC / EXISTING 27'x11'x2' / /� CATCH BASIN / INFILTRATION °° / z �o TRENCH 16 14' w PROPOSED �DEc ! LOT I CATCH BASIN ! 004 00100 F / HOOP EXISTING 014" ASPHALT \ CATCH BASIN �^ DEC NEW RESTROOM 1� / FFE: 322.0 r `PROPOSED / So 'CATCH BASIN r 28" F i I - N 88*0 '02" E 135.76(C) 13 • '(P) EXISTING CATCH BASIN 60 0 30 60 120 MATHAY BALLINGER PARK DATE 08 29 24 24100 78TH PLACE WEST PROJECT NO. 23072.001 C C EDMONDS WA 98026 SCALE 1 = 60 ENGINEERING TITLE DRAWN BY ATD EXHIBIT B CHECKED BY NAT REV 1 APPROVED BY JPU Mathay Ballinger Park— CG # 23072.20 Drainage Report August 29, 2024 Section VI I, Page 2 Mathay Ballinger Park 24100 78TH PL W, Edmonds, WA 98026 OPERATION AND MAINTENANCE MANUAL Date: August 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 August 29, 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 August 29, 2024 Drainage Report Section VI I, Page 4 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 SE 1 /4, SE 1 /4, SECTION 31, TOWNSHIP 27 NORTH, RANGE 4 EAST, W.M. CB RIM=337.76 / 3 6: o `r26 26„ F / >= '12 IE 12" RCP(NW)=335.86 , < l F ^ - - IE 12" RCP(SE)-335.76 x , = ` -; F 22" / CB RIM=3,i671 - _ ' s 3� .8» F F %RCP NW-328.88� \6„ 14"x2 E 12' ( ) - CPP(SW)=328.88 'E.STCB,i` /' / % 26" /F \I// / + RIM: 330.71 - - i - - - �_ - / 1 - - - _/� / FyNW): 32 E(12"8.SS- �- - - - -/- - / - 34 IE 112"SWI: 328.88' - �! - j ,� C �. / 7 - �"L'�j - �BRINGTO GRADE W/.,RISERS, \ ,/' 1 M� / CB RIM=327.80 VV00 / /-/ - �� J-,' - - 1 - - INST LLSOLID UDONEXISTING CB F k' 11 IE 12" CPP(NE)=324.68 IE 12" PVC(SW)=324.68// / (AIL /� i'\�.� 'j 'y' -i� LSIKtNFILTRATION TRENCH// ' / 95,481 SE`1 /Y\33 //%� ` I I� , P X / / 5 , F RACK ' So» 5% 2704310040280G,' i( _ 2�- /� � CB RIM=326.19;' ; z / IE 12" PVC(NE)=323.39 / (u / 0$Ti./... ,'/2 32" IE 12" RCP(S)=323.39 /� 3 \ /( ,J./ ! - _ >:'�0 1IN Fco // ---_____ 42" 34" TI IPI/-2 SD;'� 11 / PROPOSED PARKING, PAVEMEN�, / PATCHING, AND PORTIONS OF. WALKWAY TO FLOW ALONG NATURAL DRAINAGE COURSE TO EXISTING CBS I / GRADING AND DRAINAGE PLAN SCALE: IV 00 VV I CONNECT TO EXISTING STORM 1 I I I I I I I nT 9 � FENCE COR. 0.3'(N) OF CORNER -319.82 CB RIM C`- IE 2" PVC(W)=319.42 w V II� � 1 --------------- \ \ \ \ \ \ \ 00 00491100000803 \ \ \ RESTROOM AND ALL UTILITY STUB OUTS PREVIOUSLY COMPLETED BY OWNER. UTILITY STUB OUTS INCLUDE SEWER, WATER AND STORM (`R QlAd-Z7/1 97 WARNER ADDITION VOL. 15, PG. 76 I I I I I I I II I I 20 0 10 20 40 GRADING AND UTILITY PLAN NOTES 1. SOILS REPORT REPORT NUMBER: 074217.010 PREPARED BY: LANDAU ASSOCIATES DATED: 23 JUNE 2023 2. AMINIMUM 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 Y HORIZONTAL SEPARATION AND V 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. ATYPE 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: 9,694 SF. NEW ASPHALT PAVEMENT: 8,388 SF. 4,733 SF PORTION ROUTED TO INFILTRATION #1, 1,200 SF PORTION ROUTED TO INFILTRATION TRENCH 12, REMAINING 2,455 SF BYPASSES INFILTRATION TRENCHES. EQUIVALENT -2,500 SF OF EXISTING ASPHALT ROUTED TO INFILTRATION TRENCH #2. NEW ROOF: 191 SF. RUNOFF ROUTED TO INFILTRATION TRENCH 12. NEW CONCRETE PAVEMENT: 1,116 5F. 1,044 5F PORTION ROUTED TO INFILTRATION #1, 72 SF PORTION ROUTED TO INFILTRATION TRENCH #2. NOTE: BOTH INFILTRATION TRENCHES SIZED FOR ALL PROPOSED HARDSCAPE AREAS INCLUDING 25% RETROFIT AND BYPASS AREAS. BYPASS AREAS ARE TO FLOW ALONG NATURAL DRAINAGE PATH AND INTO THE CITY MS4 AS INDICATED ON PLANS. PORTIONS OF EXISTING HARDSCAPE TO FLOW TO INFILTRATION TRENCHES. GRADING QUANTITIES TOTAL EXCAVATION (CUT) - 10 CU YDS TOTAL EMBANKMENT (FILL) 340 CU YDS TOTAL 350 CU YDS THE QUANTITIES SHOWN ABOVE ARE FOR THE PERMIT PROCESS ONLY. THESE VALUES ARE APPROXIMATE. DO NOT USE FOR BIDDING, PAYMENT, OR ESTIMATING PURPOSES. PAVING LEGEND NEW ASPHALT/UTILITY SAWCUT OVERLAY EXISTING ASPHALT NEW CONCRETE CATCH BASIN SCHEDULE MARK TYPE RIM ELEV INV ELEV NOTES TYPE 323.80 IS" 5): 320.26 2 3 4 C3.3 C3.3 C3.3 TYPE 1 322.90 (6" N): 319.92 IS" W): 319.82 2 3 4 C3.3 C3.3 C3.3 TYPE 323.10 IV' E): 319.60 (S" S): 319.50 2 3 4 C3.3 C3.3 C3.3 V TYPE 321.80 16"S): 318.71 2 3 4 C3.3 C3.3 C3.3 v TYPE 1 320.40 (6" N): 318.68 IS" 5): 318.58 2 3 4 C3.3 C3.3 C3.3 C) TYPE 1 320.54 (12 W):318.44 (6 E) 318.54 (4' N): 318.54 2 3 4 C3.3 C3.3 C3.3 (\�� TYPE 320.50 (4 N): 319.0 (4" E): 319.0 (4" W): 319.0 2 3 4 C3.3 C3.3 C3.3 INFILTRATION TRENCH SCHEDULE MARK SIZE TOP BOT INV ELEV NOTES O1 47' x 10' x 2' 321.0 319.0 IE: IS" PERT PVC): 319.50 IE:(4" DIP OVERFLOW): 321.0 5 C3.3 IE: IS" PVC, INLET, NW, N): 318.50 DI 27' x 11' x 2' 320.0 318.0 IE: IV DIP, INLET, E): 318.50 IE: IS" PERF PVC): 318.50 e5 C3.3 IE: IV DIP OVERFLOW): 320.0 BLD2023-1391 APPROVED FOR CONSTRUCTION CITY OF EDMONDS DATE: BY: CITY ENGINEERING DIVISION C � ENGINEERING 250 4TH AVE. S., SUITE 200 EDMONDS, WASHINGTON 98020 PHONE (425) 778-8500 FAX (425) 778-5536 I 05129124 III DESIGN: JCO DRAWN: ATD CHECK: JPU JOB NO: 23072.001 DATE: 10/27/23 W Q � Y Z �w a � a- aJ � LID w N Q WU oC) L.L. turn z0 a Q CD m Dorn z Q 0 _ Z z O O F- Q Q � o J SHEET / 322.35 321. REPLACE/ADD CURBS AS REQUIRED 322.06 " / 321.93 _ ASPHALT WALKWAY - / 321.86 322.10 SE 1 /4, SE 1 /4, SECTION 31, 322.20 M 321.80 o I 321.86 321.91 O'`,. 321.93 322.0 321. 3 8 / h 322.0 EXIST CB �3278 RIM: 321.28 1 IF IF" W): 315.98 IE(8"S): 315.87 S 321.40 321.40 I � 321.54 42LF^6"P .5% 321.75 - \ I I 321.75 - L I --WA WAWA I -\i 321.07 - 321.58 I II\ _ 321.44 - 320.601 � / 1 321.13� I// MN �I C6 II. I � RIM: 320.60 321.78 11- g 322.0 32193 13 LF V DIP @05% 1 12 LF ^'6 DIP @0.5%MIN A wA-WA-WAS 56 LF - 12" DIP @ 0.5% `' N 88°06'0. 31 LF ^'12"DIP @3.8% 33 LF - 4" DIP @ 0.7% J - IF (12" RCP N): 318.72 jE 13-" RCP S). 317.27 d - IF (12" DIP Q: 317.27 I IE (12" DIP S): 317.27 I I 320.A9 I d Q' c I I I 45 LF -12" DIP @ 0.5% I EXIST CB RIM: 320.60 IE (12" RCP S): 317.04 r I I I IE (12" DIP N):317.04 I I I L I CATCH BASIN SCHEDULE MARK TYPE RIM ELEV INV ELEV NOTES TYPE 1 323.80 IF" 5): 320.26 2 3 4 C3.3 C3.3 C3.3 TYPE 1 322.90 (6" N): 319.92 IF" W): 319.82 2 3 4 C3.3 C3.3 C3.3 tiJ TYPE I 323.10 (6' Q: 319.60 (6" S): 319.50 2 3 4 C3.3 C3.3 C3.3 TYPE 321.80 IF" S): 318.71 2 3 4 C3.3 C3.3 C3.3 �S TYPE 1 320.40 IF" N): 318.68 IF" S): 318.58 2 3 4 C3.3 C3.3 C3.3 C) TYPE I 320.54 (12"W): 318.44 IF" E):318.54 (4" N): 318.54 4 C2 3 C3.3 C �7, TYPE 1 320.50 IV N): 319.0 (4" E): 319.0 (4" W): 319.0 2 3 4 C3.3 C3.3 C3.3 INFILTRATION TRENCH SCHEDULE MARK SIZE TOP BOT INV ELEV NOTES 0 47'x10'x2' 321.0 319.0 IE:(6" PERF PVC): 319.50 IE:(4" DIP OVERFLOW): 321.0 5 C3.3 IE: (6" PVC, INLET, NW, N): 318.50 0 27'x11'x 2' 320.0 318.0 E:(6" DIP, INLET, E): 318.50 IE: (6" PERF PVC): 318.50 C3.3 IE: (4" DIP OVERFLOW): 320.0 321.93 '�k✓, TOWNSHIP 27 NORTH, RANG err rr�� �60 LF ^'6"DIP @0.5% / NEW RESTROOM FEE: 322.0 I ROOF & FOOTING DRAIN 1 C� RESTRO M AND ALL UTILITY STUB r OUTS PREVIOUSLY COMPLETED BY r OWNER. UTILITY STUB OUTS INCLUDE SEWER, WATER AND STORM 16 LF ^'6"DIP @6.8% 24 LF ^' 4" DIP TI IHTLINE @ 6.8% E 135.76'(C) vv 135.88'(P) EXIST CB RIM: 320.27 IE (4" E): 319.32 _ IE (4" N): 318.87 IF (6" W):318.77 m E 4 EAST, W.M. SOIL LOGS: (PER SOIL REPORT BY LANDAU ASSOCIATES) PIT-1 (ELEV:NOT MEASURED) 0.0-0.25 SP-SM (TOPSOIL)BROWN, FINE TO COARSE, SAND WITH GRAVEL,SILT, AND ROOT ORGANICS (LOOSE, DAMP) 0.25-2.25 SM (RECESSIONAL OUTWASH)LIGHT BROWN, SILTY SAND WITH GRAVEL AND ROOT ORGANICS (LOOSE, DAMP) 2.25-10.25 ML BROWN -GRAY, SILT WITH GRAVEL TRACE COBBLES, AND MOTTLING (MEDIUM STIFF, DAMP)(INFILTRATION TEST DEPTH) 10.21-10.505M GRAY, SILTY, VERY GRAVELLY, SAND WITH COBBLES (MEDIUM DENSE, DAMP) SAMPLES WERE COLLECTED AT 1.25, 2.25, 6.25, AND 10.25 FEET GROUNDWATER NOT OBSERVED TEST PIT CAVING WAS NOT ENCOUNTERED TEST PIT WAS COMPLETED AT 10.5 FEET ON 05/24/23 TP-1 (ELEV:NOT MEASURED) 0.0-0.25 SP-SM (TOPSOIL)BROWN, FINE TO COARSE, SAND WITH GRAVEL,SILT, AND ROOT ORGANICS (LOOSE, DAMP) 0.25-1.75 SM (RECESSIONAL OUTWASH)LIGHT BROWN, SILTY SAND WITH GRAVEL AND ROOT ORGANICS (LOOSE, DAMP) 1.75-3.75 ML BROWN -GRAY, SILT WITH GRAVEL TRACE COBBLES, AND MOTTLING (MEDIUM STIFF, DAMP) 3.75-9.50 SM LIGHT BROWN,GRAVELLY, VERY SILTY, SAND WITH COBBLES (MEDIUM DENSE, DAMP) SAMPLES WERE COLLECTED AT 1.75, 3.75, 5 75, AND 8.25 FEET GROUNDWATER SEEPAGE WAS NOT ENCOUNTERED TEST PIT CAVING WAS NOT ENCOUNTERED TEST PIT WAS COMPLETED AT 9.5 FEET ON 05/24/23 TP-2 (ELEVAOT MEASURED) 0.0-0.25 SP-SM (TOPSOIL)BROWN, FINE TO COARSE, SAND WITH GRAVEL,SILT, AND ROOT ORGANICS (LOOSE, DAMP) 0.25-4.25 SM (RECESSIONAL OUTWASH)BROWN, SILTY SAND WITH GRAVEL ORGANICS, AND MOTTLING (LOOSE, DAMP) 4.25-5.75 ML BROWN -GRAY, SILT WITH GRAVEL, TRACE COBBLES, AND MOTTLING (MEDIUM STIFF, DAMP) 5.75-9.0 SM GRAY, SILTY SAND WITH GRAVEL AND COBBLES (MEDIUM DENSE, MOIST) SAMPLES WERE COLLECTED AT 1.50, 4.25, 5.75, AND 8.25 FEET GROUNDWATER SEEPAGE WAS NOT ENCOUNTERED TEST PIT CAVING WAS NOT ENCOUNTERED TEST PIT WAS COMPLETED AT 10.3 FEET ON 05/24/23 TP-3 (ELEV:NOT MEASURED) 0.0-0.25 SP-SM (TOPSOIL)BROWN, FINE TO COARSE, SAND WITH GRAVEL,SILT, AND ROOT ORGANICS (LOOSE, DAMP) 0.25-3.33 SM (RECESSIONAL OUTWASH)BROWN, SILTY SAND WITH GRAVEL ORGANICS, AND MOTTLING (LOOSE, DAMP) 3.33-10.30 ML LIGHT GRAY, SANDY SILT WITH MOTTLING(MEDIUM STIFF, DAMP) SAMPLES WERE COLLECTED AT 2.75, 3.33, AND 10.0 FEET GROUNDWATER SEEPAGE WAS NOT ENCOUNTERED TEST PIT CAVING WAS NOT ENCOUNTERED TEST PIT WAS COMPLETED AT 10.3 FEET ON 05/24/23 TP-4 (ELEV:NOT MEASURED) 0.0-0.25 SP-SM (TOPSOIL)BROWN, FINE TO COARSE, SAND WITH GRAVEL,SILT, AND ROOT ORGANICS (LOOSE, DAMP) 0.25-5.25 SM (RECESSIONAL OUTWASH)BROWN, SILTY SAND WITH GRAVEL ORGANICS, AND MOTTLING (LOOSE, DAMP) 3.33-8.25 ML BROWN -GRAY, SILT WITH GRAVEL, TRACE COBBLES, AND MOTTLING (MEDIUM STIFF, DAMP) 8.25-10.0 SM GRA,SILTY, VERY GRAVELLY, SAND WITH TRACE COBBLES (MEDIUM DENSE, DAMP) SAMPLES WERE COLLECTED AT 1.5, 5.25, AND 8.25 FEET GROUNDWATER SEEPAGE WAS NOT ENCOUNTERED TEST PIT CAVING WAS NOT ENCOUNTERED TEST PIT WAS COMPLETED AT 10.3 FEET ON 05/24/23 BLD2023-1391 APPROVED FOR CONSTRUCTION CITY OF EDMONDS DATE: BY: CITY ENGINEERING DIVISION C 4m ENGINEERING 250 4TH AVE. S. SUITE 200 EDMONDS, WASHINGTON 98020 PHONE (425) 778-8500 FAX (425) 778-5536 I 05/29/24 III DESIGN: JCO DRAWN: ATD CHECK: JPU JOB NO: 23072.001 DATE: 10/27/23 a J a_ Ld V Q � Y Z w Q a� IL � LID N Q Q� U O W 00 darn z a � a Q � m DQ l^ J V N � 0 Q z >_ O O Q a o Q N LiJ 0- (7 y SHEET C.2 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 Mathay Ballinger Park— CG # 23072.20 Drainage Report August 29, 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