Loading...
APPROVED STM BLD2020-0965+Storm_Drainage_Report+12.23.2020_10.29.29_AM+1961202RESUB Dec 23 2020 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Johannessen Short Plat Lot 2 10729 226t" Street SW Edmonds, WA 98020 Storm Drainage Report Prepared for: Leif Helleren Date: September 15, 2020 Revised: December 21, 2020 COMPLIES WITH APPLICABLE CITY STORMWATER CODE of d 36508 9W� \� ISTEg��� I01�rn r . 12/21/2020 Prepared by: Rob Long, PE RAM Enginpering, Ines 16531 13t" Ave W, Suite A108, Lynnwood WA 98037 (425) 678-6960 RAMengineeringinc.com Job No. 17-002 Lot 2 of Johannessen Short Plat 10729 226th Street SW Edmonds, WA 98020 Introduction: This summary report provides site design information for a lot 2 of the Johannessen 3-lot short. This report includes storm drainage analysis to support the building permit review and approval. The property is located on the north side of 2261h St SW and east 1081h Ave W (N Deer Dr), in the southwest 1/4 of Section 25, T 27 N, R 3 E, W.M. Site Address: 10729 226th Street SW Applicant: Leif Helleren Edmonds, WA 98020 P.O. Box 1764 Edmonds, WA 98020 Tax Parcel Number: 270325-002-035-00 (new parcel to be assigned by Sno Co.) TABLE OF CONTENTS SECTION PAGES A. Project Summary............................................................................................................................... 3 B. Parcel (Vicinity) Map.......................................................................................................................... 1 C. Site Plan............................................................................................................................................. 2 D. Aerial Photo....................................................................................................................................... 1 E. Stormwater Control System Summary............................................................................................. 15 F. Drainage Basin Description and Maps............................................................................................... 3 G. Grading and Erosion Control Summary (SWPPP Evaluation)............................................................ 3 H. Operation and Maintenance Guidelines.......................................................................................... 10 I. Geotechnical Engineering Report.................................................................................................... 14 RAM =ngineering, Inc. Johannessen Short Plat Final Engineering and Drainage Report Lot 2 #10729 226t'' St SW RAM No. 17-002 Page i A. PROJECT SUMMARY: This report provides engineering information for the proposed construction a single family residence on Lot 2 of the Johannessen short plat located at 10727 226th St SW in the City of Edmonds. Existing Conditions. Lot 2 of the Johannessen short plat consists of about 16,654 sf (0.38 acres) and is currently a vacant lot of the short plat. The site is surrounded by large -lot single family residences to the north, west, and east; and 226th St SW to the south (see attached aerial photo- section D). The site generally slopes in a south direction towards 226th St SW at a relatively flat slope. There is about two feet of fall across the lot with an average grade slope of about 1%. The site's drainage runoff would sheet flow southerly direction towards 226th St SW. No stream or wetlands were discovered on or immediately adjacent to the site; Deer Creek is located about 900 feet south of the site. Additional discussion of the local drainage basin and downstream path is discussed in section F of this report. Developed Conditions. The proposed project includes the construction of single residence and associated driveway and utilities. The lot will utilize a shared access driveway apron off 2261h St SW for access with Lot 1 (west of the site) of the short plat. New infrastructure improvements include a stormwater conveyance and separate infiltration trench/dry well; water; sewer; power; and communications. The individual lot infiltration trench/dry well system is designed and sized to provide 100% infiltration of the project's hard surfaces and meet compliance with the LID performance standard of the Edmonds Community Development Code (ECDC). All disturbed pervious (lawn and landscape) areas will preserve or restore the health and water -holding capacity of the soils by compost -amending (Per DOE BMP T5.13: Post -Construction Soil Quality and Depth). Due to the fact, the pollution generating driveway area is less than 5,000 sf (2,450 sf) no water quality treatment system will be provided. A full overview of the proposed storm drainage control facilities, offsite/downstream analysis and grading and erosion control measures are discussed in the following sections of this report. RAMEngineering, Inc. Engineering and Drainage Report RAM No. 17-002 Johannessen Short Plat Lot 2 #10729 226t" St SW Page A-1 Summary of Minimum Requirements for Category 2 Project: 5.1 Minimum Requirement#1—Preparation of StormwaterSite Plan. The proposed Lot 2 site development is part of a larger short plat development that will creating/replacing about 16,650 sf of hard surface area. Thus, the project is classified as a Category 2 project per the City's classification system. The civil site development plans and this report have been prepared to address the projects impacts. 5.2 Minimum Requirement #2 — Construction Stormwater Pollution Prevention. A construction Stormwater Pollution Prevention Plan (SWPPP) has be incorporated into the site development plans. A summary of the site's erosion control measures that evaluates the typical 13 elements of a SWPPP are included in section G. The total site disturbance area of the project is less than one acre, thus a formal Notice of Intent application for NPDES coverage will not be made to the Department of Ecology. 5.3 Minimum Requirement #3 —Source Control of Pollution. Specific source controls are not required for single family residential sites. General requirements for these sites include preventing the discharge of pollutants to the City's storm drainage system per Edmonds City Code Chapter 7.200 (Illicit Discharges). This includes common household items such as pesticides, herbicides, fertilizers, detergents, and fluids from vehicle maintenance. Single family residences shall incorporate DOE's S411 BMPs for landscape and lawn vegetation management. Lawn and vegetation management can include control of objectionable weeds, insects, mold, bacteria, and other pests with pesticides. Examples include weed control on golf course lawns, access roads, and utility corridors and during landscaping; sap stain and insect control on lumber and logs; rooftop moss removal; killing nuisance rodents; fungicide application to patio decks, and residential lawn/plant care. It is possible to release toxic pesticides such as pentachlorophenol, carbamates, and organometallics to the environment by leaching and dripping from treated parts, container leaks, product misuse, and outside storage of pesticide contaminated materials and equipment. Poor management of the vegetation and poor application of pesticides or fertilizers can cause appreciable stormwater contamination. 5.4 Minimum Requirement #4 — Preservation of Natural Drainage Systems and Outfalls. The site does not have a defined discharge location and due to the underlying outwash soils, it is believed a majority of the stormwater runoff dissipates/infiltrates prior to leaving the site. The proposed project will utilize infiltration trench/ dry well to mitigate new hard surfaces, no outfall discharge point is proposed. The site is located within the Deer Creek watershed basin and eventually discharge to the Puget Sound (via Deer Creek) per the City of Edmonds maps (see section F). 5.5 Minimum Requirement #5 — Onsite Stormwater Management. The developed site conditions include new/replaced hard surface for the roof top, driveway, and walkway/patio areas for the proposed residence. All rooftop and exterior area collection drains shall convey stormwater run-off to the on -site infiltration trench/dry well system on the lot. The individual lot infiltration trench/dry well system has been designed and sized to meet compliance with the LID performance standard (MR #5) of the Edmonds Community Development Code (ECDC). Additionally, all disturbed pervious (lawn and landscape) areas will preserve or restore the health and water -holding capacity of the soils by compost -amending (Per DOE BMP T5.13: Post - Construction Soil Quality and Depth). See civil site development plans and section E for additional sizing calculations and construction details. RAMEngineering, Inc. Engineering and Drainage Report RAM No. 17-002 Johannessen Short Plat Lot 2 #10729 226t" St SW Page A-2 5.6 Minimum Requirement #6 — Runoff Treatment. The project does not propose to create/replace more than 5,000 sf of pollution -generation impervious surface onsite. The project will create about 2,450 sf of pollution generation hard surfaces (driveway); most the site's hard surface is rooftop and walkway/patio areas (non -pollution generation surfaces). Thus, no basic or enhanced water quality treatment system is required. The site's stormwater control system will include a sump and a floatable tee that will provide some water quality and oil/water separation of the collected runoff. 5.7 Minimum Requirement #7— Flow Control. An infiltration trench/dry well will provide flow control of the site's stormwater runoff. The infiltration trench/dry well shall meet the flow control standards of a Category 2 project in a creek or lake basin and meet full flow control (due to the fact the total short plat project proposes more than 10,000 sf of hard surface area). The individual lot stormwater infiltration system is designed to fully mitigate the increased hard surfaces and be in full compliance with the LID Standard and full flow control (match flow durations between 8 percent of the 2-year flow through the full 50-year flow). 5.8 Minimum Requirement #8— Wetland Protection. No wetlands are known to exist on or adjacent to the site. 5.9 Minimum Requirement #9 — Operation and Maintenance. An operation and maintenance summary is provided in section H. RAMEngineering, Inc. Engineering and Drainage Report RAM No. 17-002 Johannessen Short Plat Lot 2 #10729 226t" St SW Page A-3 B. SHORT PLAT PARCEL (VICINITY) MAP QUAR rtR �.... !C':ASHV NAB K ..,A SW j 25 27 C 3 CfnelrAnf - - tat BsocM — Sfctton - — - coyrrr Gw w — ' • s.,e&v — ftOw — Ouanx To ACcI •- I ::'.+ »:: _ " •It:: M1 YIWf Onfr Lot 1ho ROW Info (•Af4R.er11 i.-. I Win for '''' sir Ww�Fll !'�wlp •y�MwrM. "::....:.. Mela YAtlr Yr OtlStier — b4c LG1 ... - _—.._ NW454743 !00PAR#( i 7 at bsr' o2•'t102 7..,. j .., 1!i Esc H[— fa 7 t FLf,4 WAY 7i 6$ ' t I jai 3 NOOMINIUM 12I ' 01 r,1, 2.140 tt 5 pL PH ! t'-r f f 7 f (8383) Pr.,;.. 1 o-i 14 n s2 s t9 r .. .. 220TH8r 'SW - 3.012 Nt t 1s �'A n p 17 14 ' EL 3L �o s a 7 y{P"f i g ' Zs t1 fL04 or s w s A01 ' 5472 = ¢ r r s 00 s WILLOW � # tr f4 1s 7Y 4 3 ¢ . w �I a to- tt 1s o y J 4 f TWIN VIE : 3# s ! P11 1 ]S 14 .` f (73&1) 14 1! 12 11 W 3 4 1 3 T 4 s 3as5 CREEK 7 30t6 is V 22 L f t� 4 — F 4 7 ELM s^---^^'�'. a s I x s a e CONDOMINIUM spri` PLACE 3.6t6 .,S t7 1 2 7 a 7 ''Q .. P1ir ... '*"°_ «.. 3-019 _ is O� _f - - - I 1 `h ] ff ! T 5- to A - 7354 < s 2 t —&020 _ w 61RCH PL 4 suoe t. S 10 1 7 a ►{� ■ S 5 O0 3-029 I 9.9t&3 11 I 12 SITE 3-103 f0 n1 I 13 EI a IT N 223RO ST SW 16 11 1 3-026 30 33 14 tr s1 sf N s 3 I r n m: C ❑ ADO" '3_ ]s ' M1 a 3A3'a 1 1 r7 u 39 144• P $ 50 7 13TH WAY SW .. 1 2 { r u3 LLr 3 y 4,s '13rH WAY34 ;i'�; t i I 3 3-048 m S s g1ro 2 'r = Al 4! 39 3! 17lu 3-1 + 2 3 f 3-051 i rS PA K 128 ng+'",a 3-p6G L to - --14TH ST. .— 3'073 - ` ..'/q-44_1��N os •:� � is to e ► 1 'r • -.. 16 a,m l;•tci ��53 57 ' _ U.. WAY 34Y ' , I 06 - 97 02 13 BELT, ADf_ 14 eL p 12 St i6 17 4 - P�.� tS 4 t 19 u� t3 ' u y 3 = t{ 13 ...... ;9•Vl 00 S S•1fi3 ^� �. r 14TH WAY SW 11 ""-"- g ..12� t1 04 s 3-054 a 73 [� v e 3•L199., t t]9t C tf 17 9 t0 127 o tirrl w1r 7 7z oV 7 ' i 1E 0 t "=3i5t,.. 7 f 4 I 2asry �. -3.1p0 Q::; • is 3 f !! tl: 3•094 ] 11 f t l q 4 1 AT 3496 - r•S ? 3.093 5S S'x Sh C 226TH ST SW g 151N 4 3 2 gT19 1 r 31 t0 SW 3 ii+ 1 t M 7 i f r t 17 1 to 3 146 -3 105y1y 'y t4E S 0PAT ILIA 3-tt7 3.116 ; 3-115 3-114 3 t4 .•.d m Ql s 3 1 l t f E :' ZnTH PL SW 3• 109 ".,.._...i.......w.wb,w......r .......,, 3 72 _ ,� 1!j p n 14 21 v Ill IS116 3.119 f tl ; rl rn ml� SA �f �1 4 5• f 4 r 0� M....» ...._..__...,.._.._.Ww. e u w r3-126 3'� k AN1�N PA 3 3.121 ' 3-120 7 tr x !^ 1 OL M C Jr: ...,.__._.._..._._...m„_....w.......m._...... a is f3.1t1 a I z 1 3-056 2 s a 5 3'122 3-123 °r9 +, 1f ,! 3•7 3-062 s �'-2'i7TH K SW 27 LL-2000-136 01) 12 tt t7 ES Ar s No i P-161 ...... • _.. eJZ PQ6 'IdfES-TPARK_1.074... NYY.16�2T•63 RAM Engineering, Inc. Engineering and Drainage Report RAM No. 17-002 Johannessen Short Plat Lot 2 #10729 2261" St SW Page 8-1 C. SHORT PLAT SITE PLAN �Af£X NIXNAR / // UNPLATTEO i ------------ AFN \ (crR.aal r PAEL T `C^ I ! I / /' ��'f',•t�� /'%���f ��/ I � \\��'a® � �Cj � `Caw'esr i----- \/ J ' psi x vrJ i o tF alJ,,' I ie3 ASSESSOR'S PLAT 0 ;; Epp xo� OF NOOONAY PARK I �A_i/ / ' y♦1 1 '/—� 1 r�® rwUsc oK'1or AFN 20050f0450O2 �I 0 YYY / //r� / 9a �t'F\ ioor �wwww//accrrU lJ 12 / ✓ a�zr� rARPiucJ N. mu zr�w61 \ \ /gyp rv� f---- _i_ �\ \ hM1 i i mcposco ra I ___ Ccm crrarvrves) \ .•P _ -snnxs MVAT / J l c smc r �! --ssco __- X M7 i ` 1 g i �� - II !I li Nn �l F----------. � II /✓ / ,\ _ . sas e sswn K-� / A I l � »tsne. x a eumsu / \, fd]H9ry GSEMENr I / I I �n II SNO PLAr$-2009 • }55 \---_-_____-__ p I / I IIN 1 AINTOOS0104500T �' /// rd• ry I 2 T , _ _ L -- - wsrun,�araau�r y i ____________ ________J ' —'—fsE orrAu av sir or-arl Inns cwr _'/z" '° r----I ' l wArcR ___ ior�elieor r r-r/z' wnn ! I 1 w mr __ urury eager tow;certav �. frs%u�mRr'' zss siu - - -'-'---_,-=� ---� fcors a?1 an �.saxcv me E✓<hiRt�AUP �.- � �c RAM Engineering, Inc. Engineering and Drainage Report RAM No. 17-002 Johannessen Short Plat Lot 2 #10729 226t" St SW Page C-1 LOT 2 SITE PLAN: RAM Engineering, Inc. Engineering and Drainage Report RAM No. 17-002 Johannessen Short Plat Lot 2 #10729 226t" St SW Page C-2 D. SHORT PLAT AERIAL PHOTO (City of Edmonds GIS, 2015 photo) RAM Engineering, Inc. Engineering and Drainage Report RAM No. 17-002 • 40momljff� Johannessen Short Plat Lot 2 #10729 2261" St SW 0" Page D-1 E. STORMWATER CONTROL SYSTEM SUMMARY AND CALCULATIONS: The project development of Lot 2 will create 8,220 sf of hard surface. The hard surface areas include the roof top, driveway, walk/patio areas together with 50% of the shared driveway access apron off 2261" St SW. To mitigate the development of the site, an individual lot infiltration trench/drywell system will be installed to control the drainage runoff (flow control). The project applicant has elected to meet the LID Performance Standard to comply with ECDC 18.30.060.D.b (ii) and (iii), stormwater discharges shall match developed discharge durations to pre -developed durations for the range of pre -developed discharge rates from 8 percent of the 2-year peak flow to 50 percent of the 2-year peak flow from the project site. Additionally, the project will meet Minimum Requirement No. 7 and match flow durations between 8 percent of the 2-year flow through the full 50-year flow. The following is a summary of the Lot 2 hard surface areas: Lot 2 Hard Surface Summary: House = 5,170 sf Driveway = 2,050 sf Walk/Patio = 600 sf 50% 226t" St SW Frontage Apron = 400 sf Lot 2 Hard Surface = 8,220 sf (0.189 ac) A site specific geotechnical evaluation was made to assess the use of infiltration and LID measures onsite. The evaluation determined infiltration is feasible onsite and recommends a long-term infiltration design rate of 18.0 in/hr. The infiltration trench/dry well will be located at the southerly portion of Lot 2. The infiltration trench shall be a minimum of 7 feet wide, 28 feet long and 2.5 feet deep; and filled with %" to 1-%" washed drain rock (35% voids). The below calculations demonstrate that the trench will fully mitigate the increased hard surfaces and the project will be in full compliance with the LID Standard and full flow control (match flow durations between 8 percent of the 2-year flow through the full 50-year flow). The developed runoff rates and storage calculations were performed using the DOE 2012 Western Washington Hydrology Model (WWHM2012) continuous runoff model. See WWHM2012 printout on the following pages. RAMEngineering, Inc. Engineering and Drainage Report RAM No. 17-002 Johannessen Short Plat Lot 2 #10729 226t" St SW Page E-1 _- U 2 S CE NARID S ❑ Predeveloped WE rdinpy.-.j Run Scenario Basic Elernerks ®IM® ® .3Dafl]® f®iiz �E] ploEleirreots Cwrrrercid Toolbox Move Elanrerh Save xy I Load xy PROJECT REPORT Designate as Bypass for POC: "flow Groundwater vdTrerxhBed7 F Show Only Selected Available Impervious r ROADS/FIAT �Acres 10 r ROADS/MD. D r ROADS/STEEP 0 7v ROOF TOASIFLAi 119 r DRIVEWAYS TI AT r DRIVEWAYSIMOD 0 r DRIVEWAYSISTEEP 0 U SIDEWALKSAUT 014 r SIDEWALKS/MOD 0 F- SIDEWALKS/STEEP 0 7 PARKINGNLAT 0 r PARKINGNOD 0 r PARKINGATEEP r POND i Porova Pavernent WWHM2012 Project Name: Johannessen Lot 2 Site Name: Johannessen Site Address: Lot 2 City : Edmonds Report Date: 12/21/2020 MGS Regoin Puget East Data Start 1901/10/1 Data End : 2058/09/30 DOT Data Number: 03 Version Date: 2019/09/13 Version : 4.2.17 t3 Gravel Trench Bed 1 Mitigated Facility Name Downstream Connection Facility Type r' RecipitadanAppfedtoFaciy f vapaebuiAppfw+d to Fac fl Facility Dimensions Trench Length (p) Trench Bollom Widh (€t] Effective Total Depth (EI) 25 Top and hdtorn mope (HIV] Left Side Slope [HIV] Right Side Slope [H/V] I I Gravel Trench Bed_ 1 Outlet 1 outlet 2 outlet 3 -0--- __�]©� Gravel T(erv_WBed _DuickTrench ^Facility Dimension Dianram i Material Layers for Trench/Bed Layer 1 Thickness Ift) 2.5 Layer 1 poosity [0.1I A35 Layer 2 Thickness [Rj 0 Layer 2 porosity [0.1] Layer 3 Thickness [ftj 0 Layer 3 porosity [0.1] 0 Infiltration Yes Outlet Structure Date Riser Height (it) 25 :A Riser Diameter Inl Riser Type Notch Type Orilice Diameter Height Number [in] 00 1 Fp- F0_ J 2 F0___ F 3 10 --1 F0 TrenchVokme at Riser Head [ac t) 004 Measured Wtralion Rate (nhr) 18 Reduction Factor (ri'Fadvrj Shaw Trench Oven Table UseWetted SudaceAuea (srdew ] ND :� Initial Stage (ft) R Total Volume Ir0*ated [ac•ft] 69.532 Total Volume Through Facimy ac• t 69.535 Total Vdume Though Riser [ac•R) 0.003 Percent Infillrated 100 Size infiltration Trench Target%: Low Flow Threshold for POC 1 : 50 Percent of the 2 Year High Flow Threshold for POC 1: 50 year RAM Engineering, Inc. Engineering and Drainage Report RAM No. 17-002 Johannessen Short Plat Lot 2 #10729 2261h St SW Page E-2 PREDEVELOPED LAND USE Name : Basin 1 Bypass: No Groundwater: No Pervious Land Use acre A B, Forest, Steep .189 Pervious Total 0.189 Impervious Land Use acre Impervious Total 0 Basin Total 0.189 Element Flows To: Surface Interflow MITIGATED LAND USE Name : Basin 1 Bypass: No Groundwater: No Pervious Land Use acre Pervious Total 0 Impervious Land Use acre ROOF TOPS FLAT 0.119 DRIVEWAYS FLAT 0.056 SIDEWALKS FLAT 0.014 Impervious Total 0.189 Basin Total 0.189 Groundwater Element Flows To: Surface Interflow Groundwater Gravel Trench Bed 1 Gravel Trench Bed 1 RAM Engineering, Inc. Engineering and Drainage Report RAM No. 17-002 Johannessen Short Plat Lot 2 #10729 2261" St SW Page E-3 Name : Gravel Trench Bed 1 Bottom Length: 28.00 ft. Bottom Width: 7.00 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: 2.5 Pour Space of material for first layer: 0.35 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: 18 Infiltration safety factor: 1 Total Volume Infiltrated (ac-ft.): 69.532 Total Volume Through Riser (ac-ft.): 0.003 Total Volume Through Facility (ac-ft.): 69.535 Percent Infiltrated: 100 Total Precip Applied to Facility: 0 Total Evap From Facility: 0 Discharge Structure Riser Height: 2.5 ft. Riser Diameter: 8 in. Element Flows To: Outlet 1 Outlet 2 Gravel Trench Bed Hydraulic Table Stage(feet) Area(ac.) Volume(ac-ft.) Discharge(cfs) 0.0000 0.004 0.000 0.000 0.000 0.0278 0.004 0.000 0.000 0.081 0.0556 0.004 0.000 0.000 0.081 0.0833 0.004 0.000 0.000 0.081 0.1111 0.004 0.000 0.000 0.081 0.1389 0.004 0.000 0.000 0.081 0.1667 0.004 0.000 0.000 0.081 0.1944 0.004 0.000 0.000 0.081 0.2222 0.004 0.000 0.000 0.081 0.2500 0.004 0.000 0.000 0.081 0.2778 0.004 0.000 0.000 0.081 0.3056 0.004 0.000 0.000 0.081 0.3333 0.004 0.000 0.000 0.081 0.3611 0.004 0.000 0.000 0.081 0.3889 0.004 0.000 0.000 0.081 0.4167 0.004 0.000 0.000 0.081 0.4444 0.004 0.000 0.000 0.081 0.4722 0.004 0.000 0.000 0.081 0.5000 0.004 0.000 0.000 0.081 0.5278 0.004 0.000 0.000 0.081 0.5556 0.004 0.000 0.000 0.081 0.5833 0.004 0.000 0.000 0.081 0.6111 0.004 0.001 0.000 0.081 RAM Engineering, Inc. Engineering and Drainage Report RAM No. 17-002 Infilt (cfs) Johannessen Short Plat Lot 2 #10729 2261" St SW Page E-4 0.6389 0.004 0.001 0.000 0.081 0.6667 0.004 0.001 0.000 0.081 0.6944 0.004 0.001 0.000 0.081 0.7222 0.004 0.001 0.000 0.081 0.7500 0.004 0.001 0.000 0.081 0.7778 0.004 0.001 0.000 0.081 0.8056 0.004 0.001 0.000 0.081 0.8333 0.004 0.001 0.000 0.081 0.8611 0.004 0.001 0.000 0.081 0.8889 0.004 0.001 0.000 0.081 0.9167 0.004 0.001 0.000 0.081 0.9444 0.004 0.001 0.000 0.081 0.9722 0.004 0.001 0.000 0.081 1.0000 0.004 0.001 0.000 0.081 1.0278 0.004 0.001 0.000 0.081 1.0556 0.004 0.001 0.000 0.081 1.0833 0.004 0.001 0.000 0.081 1.1111 0.004 0.001 0.000 0.081 1.1389 0.004 0.001 0.000 0.081 1.1667 0.004 0.001 0.000 0.081 1.1944 0.004 0.001 0.000 0.081 1.2222 0.004 0.001 0.000 0.081 1.2500 0.004 0.002 0.000 0.081 1.2778 0.004 0.002 0.000 0.081 1.3056 0.004 0.002 0.000 0.081 1.3333 0.004 0.002 0.000 0.081 1.3611 0.004 0.002 0.000 0.081 1.3889 0.004 0.002 0.000 0.081 1.4167 0.004 0.002 0.000 0.081 1.4444 0.004 0.002 0.000 0.081 1.4722 0.004 0.002 0.000 0.081 1.5000 0.004 0.002 0.000 0.081 1.5278 0.004 0.002 0.000 0.081 1.5556 0.004 0.002 0.000 0.081 1.5833 0.004 0.002 0.000 0.081 1.6111 0.004 0.002 0.000 0.081 1.6389 0.004 0.002 0.000 0.081 1.6667 0.004 0.002 0.000 0.081 1.6944 0.004 0.002 0.000 0.081 1.7222 0.004 0.002 0.000 0.081 1.7500 0.004 0.002 0.000 0.081 1.7778 0.004 0.002 0.000 0.081 1.8056 0.004 0.002 0.000 0.081 1.8333 0.004 0.002 0.000 0.081 1.8611 0.004 0.002 0.000 0.081 1.8889 0.004 0.003 0.000 0.081 1.9167 0.004 0.003 0.000 0.081 1.9444 0.004 0.003 0.000 0.081 1.9722 0.004 0.003 0.000 0.081 2.0000 0.004 0.003 0.000 0.081 2.0278 0.004 0.003 0.000 0.081 2.0556 0.004 0.003 0.000 0.081 2.0833 0.004 0.003 0.000 0.081 2.1111 0.004 0.003 0.000 0.081 RAM Engineering, Inc. Engineering and Drainage Report RAM No. 17-002 Johannessen Short Plat Lot 2 #10729 2261" St SW Page E-5 2.1389 0.004 0.003 0.000 0.081 2.1667 0.004 0.003 0.000 0.081 2.1944 0.004 0.003 0.000 0.081 2.2222 0.004 0.003 0.000 0.081 2.2500 0.004 0.003 0.000 0.081 2.2778 0.004 0.003 0.000 0.081 2.3056 0.004 0.003 0.000 0.081 2.3333 0.004 0.003 0.000 0.081 2.3611 0.004 0.003 0.000 0.081 2.3889 0.004 0.003 0.000 0.081 2.4167 0.004 0.003 0.000 0.081 2.4444 0.004 0.003 0.000 0.081 2.4722 0.004 0.003 0.000 0.081 2.5000 0.004 0.003 0.000 0.081 ANALYSIS RESULTS Stream Protection Duration Predeveloped Landuse Totals for POC #1 Total Pervious Area:0.189 Total Impervious Area:O Mitigated Landuse Totals for POC #1 Total Pervious Area:O Total Impervious Area:0.189 Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.000094 5 year 0.000126 10 year 0.000143 25 year 0.00015 50 year 0.00015 100 year 0.000151 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0 5 year 0 10 year 0 25 year 0 50 year 0 100 year 0.003999 RAM Engineering, Inc. Engineering and Drainage Report RAM No. 17-002 Johannessen Short Plat Lot 2 #10729 2261" St SW Page E-6 Stream Protection Duration Annual Peaks for Predeveloped and Mitigated. Year Predeveloped Mitigated 1902 0.000 0.000 1903 0.000 0.000 1904 0.000 0.000 1905 0.000 0.000 1906 0.000 0.000 1907 0.000 0.000 1908 0.000 0.000 1909 0.000 0.000 1910 0.000 0.000 1911 0.000 0.000 1912 0.000 0.000 1913 0.000 0.000 1914 0.000 0.004 1915 0.000 0.000 1916 0.000 0.000 1917 0.000 0.000 1918 0.000 0.000 1919 0.000 0.000 1920 0.000 0.000 1921 0.000 0.000 1922 0.000 0.000 1923 0.000 0.000 1924 0.000 0.000 1925 0.000 0.000 1926 0.000 0.000 1927 0.000 0.000 1928 0.000 0.000 1929 0.000 0.000 1930 0.000 0.000 1931 0.000 0.000 1932 0.000 0.000 1933 0.000 0.000 1934 0.000 0.000 1935 0.000 0.000 1936 0.000 0.000 1937 0.000 0.000 1938 0.000 0.000 1939 0.000 0.000 1940 0.000 0.000 1941 0.000 0.000 1942 0.000 0.000 1943 0.000 0.000 1944 0.000 0.000 1945 0.000 0.000 1946 0.000 0.000 1947 0.000 0.000 1948 0.000 0.000 1949 0.000 0.000 1950 0.000 0.000 1951 0.000 0.000 1952 0.000 0.000 RAM Engineering, Inc. Engineering and Drainage Report RAM No. 17-002 POC #1 Johannessen Short Plat Lot 2 #10729 2261" St SW Page E-7 1953 0.000 0.000 1954 0.000 0.000 1955 0.000 0.000 1956 0.000 0.000 1957 0.000 0.000 1958 0.000 0.000 1959 0.000 0.000 1960 0.000 0.000 1961 0.000 0.000 1962 0.000 0.000 1963 0.000 0.000 1964 0.000 0.000 1965 0.000 0.000 1966 0.000 0.000 1967 0.000 0.000 1968 0.000 0.000 1969 0.000 0.000 1970 0.000 0.000 1971 0.000 0.000 1972 0.000 0.069 1973 0.000 0.000 1974 0.000 0.000 1975 0.000 0.000 1976 0.000 0.000 1977 0.000 0.000 1978 0.000 0.000 1979 0.000 0.000 1980 0.000 0.000 1981 0.000 0.000 1982 0.000 0.000 1983 0.000 0.000 1984 0.000 0.000 1985 0.000 0.000 1986 0.000 0.000 1987 0.000 0.000 1988 0.000 0.000 1989 0.000 0.000 1990 0.000 0.000 1991 0.000 0.000 1992 0.000 0.000 1993 0.000 0.000 1994 0.000 0.000 1995 0.000 0.000 1996 0.000 0.000 1997 0.000 0.000 1998 0.000 0.000 1999 0.000 0.000 2000 0.000 0.000 2001 0.000 0.000 2002 0.000 0.000 2003 0.000 0.000 2004 0.000 0.000 2005 0.000 0.000 2006 0.000 0.000 RAM Engineering, Inc. Engineering and Drainage Report RAM No. 17-002 Johannessen Short Plat Lot 2 #10729 2261" St SW Page E-8 2007 0.000 0.000 2008 0.000 0.000 2009 0.000 0.000 2010 0.000 0.000 2011 0.000 0.000 2012 0.000 0.000 2013 0.000 0.000 2014 0.000 0.000 2015 0.000 0.000 2016 0.000 0.000 2017 0.000 0.000 2018 0.000 0.000 2019 0.000 0.000 2020 0.000 0.000 2021 0.000 0.000 2022 0.000 0.000 2023 0.000 0.000 2024 0.000 0.000 2025 0.000 0.000 2026 0.000 0.000 2027 0.000 0.000 2028 0.000 0.000 2029 0.000 0.000 2030 0.000 0.000 2031 0.000 0.000 2032 0.000 0.000 2033 0.000 0.000 2034 0.000 0.000 2035 0.000 0.000 2036 0.000 0.000 2037 0.000 0.000 2038 0.000 0.000 2039 0.000 0.000 2040 0.000 0.000 2041 0.000 0.000 2042 0.000 0.000 2043 0.000 0.000 2044 0.000 0.000 2045 0.000 0.000 2046 0.000 0.000 2047 0.000 0.000 2048 0.000 0.000 2049 0.000 0.000 2050 0.000 0.000 2051 0.000 0.000 2052 0.000 0.000 2053 0.000 0.000 2054 0.000 0.000 2055 0.000 0.000 2056 0.000 0.000 2057 0.000 0.000 2058 0.000 0.000 RAM Engineering, Inc. Engineering and Drainage Report RAM No. 17-002 Johannessen Short Plat Lot 2 #10729 2261" St SW Page E-9 Stream Protection Duration Ranked Annual Peaks for Predeveloped and Mitigated. Rank Predeveloped Mitigated 1 0.0002 0.0686 2 0.0002 0.0041 3 0.0002 0.0000 4 0.0002 0.0000 5 0.0002 0.0000 6 0.0002 0.0000 7 0.0001 0.0000 8 0.0001 0.0000 9 0.0001 0.0000 10 0.0001 0.0000 11 0.0001 0.0000 12 0.0001 0.0000 13 0.0001 0.0000 14 0.0001 0.0000 15 0.0001 0.0000 16 0.0001 0.0000 17 0.0001 0.0000 18 0.0001 0.0000 19 0.0001 0.0000 20 0.0001 0.0000 21 0.0001 0.0000 22 0.0001 0.0000 23 0.0001 0.0000 24 0.0001 0.0000 25 0.0001 0.0000 26 0.0001 0.0000 27 0.0001 0.0000 28 0.0001 0.0000 29 0.0001 0.0000 30 0.0001 0.0000 31 0.0001 0.0000 32 0.0001 0.0000 33 0.0001 0.0000 34 0.0001 0.0000 35 0.0001 0.0000 36 0.0001 0.0000 37 0.0001 0.0000 38 0.0001 0.0000 39 0.0001 0.0000 40 0.0001 0.0000 41 0.0001 0.0000 42 0.0001 0.0000 43 0.0001 0.0000 44 0.0001 0.0000 45 0.0001 0.0000 46 0.0001 0.0000 47 0.0001 0.0000 48 0.0001 0.0000 49 0.0001 0.0000 50 0.0001 0.0000 51 0.0001 0.0000 RAM Engineering, Inc. Engineering and Drainage Report RAM No. 17-002 POC #1 Johannessen Short Plat Lot 2 #10729 2261" St SW Page E-10 52 0.0001 0.0000 53 0.0001 0.0000 54 0.0001 0.0000 55 0.0001 0.0000 56 0.0001 0.0000 57 0.0001 0.0000 58 0.0001 0.0000 59 0.0001 0.0000 60 0.0001 0.0000 61 0.0001 0.0000 62 0.0001 0.0000 63 0.0001 0.0000 64 0.0001 0.0000 65 0.0001 0.0000 66 0.0001 0.0000 67 0.0001 0.0000 68 0.0001 0.0000 69 0.0001 0.0000 70 0.0001 0.0000 71 0.0001 0.0000 72 0.0001 0.0000 73 0.0001 0.0000 74 0.0001 0.0000 75 0.0001 0.0000 76 0.0001 0.0000 77 0.0001 0.0000 78 0.0001 0.0000 79 0.0001 0.0000 80 0.0001 0.0000 81 0.0001 0.0000 82 0.0001 0.0000 83 0.0001 0.0000 84 0.0001 0.0000 85 0.0001 0.0000 86 0.0001 0.0000 87 0.0001 0.0000 88 0.0001 0.0000 89 0.0001 0.0000 90 0.0001 0.0000 91 0.0001 0.0000 92 0.0001 0.0000 93 0.0001 0.0000 94 0.0001 0.0000 95 0.0001 0.0000 96 0.0001 0.0000 97 0.0001 0.0000 98 0.0001 0.0000 99 0.0001 0.0000 100 0.0001 0.0000 101 0.0001 0.0000 102 0.0001 0.0000 103 0.0001 0.0000 104 0.0001 0.0000 105 0.0001 0.0000 RAM Engineering, Inc. Engineering and Drainage Report RAM No. 17-002 Johannessen Short Plat Lot 2 #10729 2261" St SW Page E-11 106 0.0001 0.0000 107 0.0001 0.0000 108 0.0001 0.0000 109 0.0001 0.0000 110 0.0001 0.0000 ill 0.0001 0.0000 112 0.0001 0.0000 113 0.0001 0.0000 114 0.0001 0.0000 115 0.0001 0.0000 116 0.0001 0.0000 117 0.0001 0.0000 118 0.0001 0.0000 119 0.0001 0.0000 120 0.0001 0.0000 121 0.0001 0.0000 122 0.0001 0.0000 123 0.0001 0.0000 124 0.0001 0.0000 125 0.0001 0.0000 126 0.0001 0.0000 127 0.0001 0.0000 128 0.0001 0.0000 129 0.0001 0.0000 130 0.0001 0.0000 131 0.0001 0.0000 132 0.0001 0.0000 133 0.0001 0.0000 134 0.0001 0.0000 135 0.0001 0.0000 136 0.0001 0.0000 137 0.0001 0.0000 138 0.0001 0.0000 139 0.0001 0.0000 140 0.0001 0.0000 141 0.0001 0.0000 142 0.0001 0.0000 143 0.0001 0.0000 144 0.0001 0.0000 145 0.0001 0.0000 146 0.0000 0.0000 147 0.0000 0.0000 148 0.0000 0.0000 149 0.0000 0.0000 150 0.0000 0.0000 151 0.0000 0.0000 152 0.0000 0.0000 153 0.0000 0.0000 154 0.0000 0.0000 155 0.0000 0.0000 156 0.0000 0.0000 157 0.0000 0.0000 RAM Engineering, Inc. Engineering and Drainage Report RAM No. 17-002 Johannessen Short Plat Lot 2 #10729 2261" St SW Page E-12 Stream Protection Duration POC #1 The Facility PASSED The Facility PASSED. Flow(cfs) Predev Mit Percentage Pass/Fail 0.0000 4583 6 0 Pass 0.0000 4419 6 0 Pass 0.0000 4275 6 0 Pass 0.0001 4119 6 0 Pass 0.0001 3987 6 0 Pass 0.0001 3868 6 0 Pass 0.0001 3713 6 0 Pass 0.0001 3584 6 0 Pass 0.0001 3433 6 0 Pass 0.0001 3315 6 0 Pass 0.0001 3197 6 0 Pass 0.0001 3045 6 0 Pass 0.0001 2964 6 0 Pass 0.0001 2859 6 0 Pass 0.0001 2749 6 0 Pass 0.0001 2683 6 0 Pass 0.0001 2604 6 0 Pass 0.0001 2524 6 0 Pass 0.0001 2443 6 0 Pass 0.0001 2362 6 0 Pass 0.0001 2274 6 0 Pass 0.0001 2206 6 0 Pass 0.0001 2117 6 0 Pass 0.0001 2052 6 0 Pass 0.0001 1982 6 0 Pass 0.0001 1820 6 0 Pass 0.0001 1749 6 0 Pass 0.0001 1681 6 0 Pass 0.0001 1609 6 0 Pass 0.0001 1528 6 0 Pass 0.0001 1455 6 0 Pass 0.0001 1364 6 0 Pass 0.0001 1321 6 0 Pass 0.0001 1264 6 0 Pass 0.0001 1200 6 0 Pass 0.0001 1169 6 0 Pass 0.0001 1121 6 0 Pass 0.0001 1080 6 0 Pass 0.0001 1039 6 0 Pass 0.0001 999 6 0 Pass 0.0001 951 6 0 Pass 0.0001 919 6 0 Pass 0.0001 883 6 0 Pass 0.0001 855 6 0 Pass 0.0001 831 6 0 Pass 0.0001 807 6 0 Pass 0.0001 782 6 0 Pass RAM Engineering, Inc. Engineering and Drainage Report RAM No. 17-002 Johannessen Short Plat Lot 2 #10729 2261" St SW Page E-13 0.0001 763 6 0 Pass 0.0001 740 6 0 Pass 0.0001 715 6 0 Pass 0.0001 634 6 0 Pass 0.0001 610 6 0 Pass 0.0001 592 6 1 Pass 0.0001 550 6 1 Pass 0.0001 507 6 1 Pass 0.0001 490 6 1 Pass 0.0001 481 6 1 Pass 0.0001 459 6 1 Pass 0.0001 439 6 1 Pass 0.0001 419 6 1 Pass 0.0001 401 6 1 Pass 0.0001 391 6 1 Pass 0.0001 373 6 1 Pass 0.0001 352 6 1 Pass 0.0001 340 6 1 Pass 0.0001 325 6 1 Pass 0.0001 312 6 1 Pass 0.0001 306 6 1 Pass 0.0001 301 6 1 Pass 0.0001 288 6 2 Pass 0.0001 269 6 2 Pass 0.0001 247 6 2 Pass 0.0001 242 6 2 Pass 0.0001 239 6 2 Pass 0.0001 232 6 2 Pass 0.0001 209 6 2 Pass 0.0001 189 6 3 Pass 0.0001 187 6 3 Pass 0.0001 185 6 3 Pass 0.0001 174 6 3 Pass 0.0001 163 6 3 Pass 0.0001 159 6 3 Pass 0.0001 140 6 4 Pass 0.0001 127 6 4 Pass 0.0001 125 6 4 Pass 0.0001 118 6 5 Pass 0.0001 116 6 5 Pass 0.0001 100 6 6 Pass 0.0001 96 6 6 Pass 0.0001 94 6 6 Pass 0.0001 80 6 7 Pass 0.0001 74 6 8 Pass 0.0001 63 6 9 Pass 0.0001 56 6 10 Pass 0.0001 52 6 11 Pass 0.0001 48 6 12 Pass 0.0001 42 6 14 Pass 0.0001 31 6 19 Pass 0.0001 26 6 23 Pass 0.0002 7 6 85 Pass RAM Engineering, Inc. Engineering and Drainage Report RAM No. 17-002 Johannessen Short Plat Lot 2 #10729 2261" St SW Page E-14 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 4 LID Report Poc i LID Technique Usedfor Total Vol ume Volume Infiltration CumulatNe Percent WaterQuaifty Percent Comment Treatment? Needs Through Volume Volume Volume Water Quality Treatment Facility (ac_N infiltration Infiltrated Treated (ac-ft) (ac-ft) Credit Gravel Trench Bed 1 POC 0 63.28 0 100.dd Total Volume Infiltrated 63.28 0.00 D.00 100.00 0.00 096 No Treat. Credit Compliance with LID Duration Standard 8% of 2-yr to 50% of Analysis 2-yr 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. 2005-2020; All Rights Reserved. RAM Engineering, Inc. Engineering and Drainage Report RAM No. 17-002 Johannessen Short Plat Lot 2 #10729 2261h St SW Page E-15 F. DRAINAGE BASIN DESCRIPTION: The site is located within the City of Edmonds Deer Creek watershed basin. The Deer Creek basin is an urban basin that collects stormwater runoff from primarily residential areas in the City Edmonds and ultimately discharges flows westerly to Puget Sound via the Deer Creek (see attached watershed map). Soils in the area consists of well -draining outwash soils that allows a majority of the stormwater to infiltrate into the ground. The road side ditch and shoulder area along 226t" St SW collect runoff from the road and then allows the runoff to infiltrate into the ground; the pipe/shoulder/shallow ditch systems along the frontage does not have a direct conveyance system that routes runoff to Deer Creek. It appears that if a significant rainfall event occurred the runoff would flow westerly (following the natural contours of the area) and then flow south down 108t" Ave W (N Deer Dr) towards Deer Creek; eventually discharge into Deer Creek about 900 ft south of the site. Deer Creek continues in a westerly direction and eventually discharges into the Puget Sound about 4,400 feet west of the site See attached watershed and downstream drainage facility map for the local downstream path. RAMEngineering, Inc. Engineering and Drainage Report RAM No. 17-002 Johannessen Short Plat Lot 2 #10729 226t" St SW Page F-1 F-2. Watershed Basin Map FIGURE B-1 CITY OF E❑MON❑S r WATERSHEDS �} Deer creek _ Perrf..rulr Edmonds Marsh - ►uier So d �' Edmonds way - Puget Sound P%ped Fx Fruhdaie - Sturm Creek I[M Good Hope Pund Siseriabareer R49i Leek - Southwest Edmonds A Wesley [reek ® Soutrwes= Edmonds a rM lake 6a1 br Tpf Sehto Geek -�} Lund', Gukh - $Ibor Park A Mrado+rdaleA Talbol Puk S h1teadm"It a Temtt Creek Northrtream 4Vntd+le Pond 6utfall Creek I.� 1-OOC 1 wacnu Geek aP]e \lK9 lea2=ft b Nrvey A W rryL �t amwa�6 nrafa a nwrcnreaalN axampMr Na v.O�sx rare.» emr A N d Meadowdale A ;---a MeadowdatA 6 Oueftll Creeky7ilthDuse Creek • �y , %�a� Gedl r t Ra00 f �H! dy �rrae Puget Sound n t To lbue Park -I :'Tathot Park 9 I, 1 Fruiidale I ; f ` F�wlhsircam �_ Goad Hope Pond f � al rl xrs,,.vsn � . PuE Sound Pj *des+f r -�xrw _^1 WIIWw Creek Deer Creek 56uthwres1 Fdmordf A sputhweM Edmonds 6 I— RAM Fngineering, Inc. Engineering and Drainage Report RAM No. 17-002 SheA Creek . s � I Wrtffate?andf Ha Hs Creek a s+ um g �7 z 'I Edmprtdt Way � : i - .- i �;d r __ laic Ba11k1gee Johannessen Short Plat Lot 2 #10729 2261h St SW Page F-2 F-3. Short Plat Downstream Drainage Facility Map (City of Edmonds GIS) a, �D kow re14 012-3 c. allo °ND ALGONQuN RD DEER CREEK i N DEER DR --jle +�•. crab. r. �:� ��cHVSE RAM =ngineering, Inc. Engineering and Drainage Report RAM No. 17-002 SITE I 'I- 1 y All P012.3s O . i -• oQ PDt2- ST sit; Johannessen Short Plat Lot 2 #10729 2261" St SW Page F-3 G. GRADING and EROSION CONTROL SUMMARY: The project will require grading to construct the proposed house and utilities (including the stormwater infiltration trench/dry well system). Standard erosion control measures are proposed to be used during construction. The primary erosion and sediment control BMP during construction will be proper soil stabilization methods. Exposed soils shall be stabilized by application of effective BMPs that protect the soil from the erosive forces of raindrops, flowing water, and wind. Applicable practices include, but not limited to, temporary and permanent seeding, sodding, mulching, plastic covering, erosion control fabrics, matting, soil application of polyacrylamide (pam), the early application of gravel base on areas to be paved, and dust control. The contractor shall select a soil stabilization method best suited for the particular situation. Stock piles must be stabilized and protected with sediment trapping measures. In addition, site containment of exposed soils shall be sustained by using silt fence barriers along the down -slope boundaries of the site's disturbance areas. See the site development plan for details. Soils: In accordance with the project's site specific geotechnical engineering study by Earth Solutions NW, LLC the on -site soils consist of poorly graded gravel with sand and poorly graded sand (Unified Soil Classification System: GP and SP) outwash deposits. The subject site is underlain by outwash (Qva) deposits; Everett series soils. Everett soils are well drained soil and are categorized as a hydrologic group A soil. Earth Solutions NW, LLC. Recommends a long-term design infiltration rate of 18.0 inches per hour. Full soils description is included in the project's site specific geotechnical engineering study by Earth Solutions NW, LLC. Construction Stormwater Pollution Prevention Plan (SWPPP): The following is a summary of the site's erosion control measures that evaluates the typical DOE 13 elements of a SWPPP: Element 1: Mark Clearing Limits: Clearing limits have been delineated on the engineering site development plans. Element 2: Establish Construction Access: A construction access has been delineated on the engineering site development plans. Element 3: Control Flow Rates: Due to the underlying outwash soils no flow control system (ie: temporary pond) is proposed. During construction silt fencing will provide attenuation of site runoff and upon project completion and stabilization (established lawns and landscape of exposed soils), the infiltration storm system will provide flow control. Element 4: Install Sediment Controls: Filter fabric fence has been delineated and detailed on the engineering site development plans. At a minimum, silt fence will be installed along the down gradient perimeter of the disturbed area that will receive sediment -laden runoff. Element 5: Stabilize Soils: Soils will be stabilized per the TESC notes listed on the engineering site development plans. RAMEngineering, Inc. Engineering and Drainage Report RAM No. 17-002 Johannessen Short Plat Lot 2 #10729 226t" St SW Page G-1 Element 6: Protect Slopes: Exposed slopes shall be stabilized per the TESC notes listed on the engineering site development plans. Element 7: Protect Drain Inlets: Drain inlet protection will be installed on all catch basins that will receive sediment -laden runoff. See the engineering site development plans for locations and detail. Element 8: Stabilize Channels and Outlets: This element is not applicable since there are no temporary channels or outlets proposed. Element 9: Control Pollutants: Pollutants shall be managed as described in the TESC notes listed on the engineering site development plans. Element 10: Control De -Watering: Highly turbid or contaminated de -watering water shall be handled separately from stormwater. The water from all de -watering systems for trench/dry wells and foundations shall be treated or disposed prior to discharging from the site. Element 11: Maintain BMPs: BMPs shall be maintained and removed at the end of the project as follows: i. All temporary and permanent erosion and sediment control BMPs shall be inspected, maintained and repaired in accordance with the Drainage Manual or as approved or required by the City to assure continued performance of their intended function in accordance with BMP specifications. ii. The applicant may remove temporary BMPs when they are no longer needed. iii. All temporary erosion and sediment control BMPs shall be removed within 30 days after construction is completed and the City has determined that the site is stabilized. Element 12: Manage the Project: The owner of the site is responsible for managing the installation and maintenance of the site BMPs. Element 13. Protect Low Impact Development BMPs: During construction the proposed infiltration trench/dry well systems areas shall be protected from sediment accumulation, sediment -laden runoff and soils, and compaction from construction equipment. Soils restoration and/or replacement may be needed if soils are compacted or contaminated with sediment. Conclusion: The final site development construction plans include specific grading and drainage improvement notes and details. With proper installation, maintenance and inspections of the proposed construction the project should have minimal impact to the surrounding environment. RAMEngineering, Inc. Engineering and Drainage Report RAM No. 17-002 Johannessen Short Plat Lot 2 #10729 226t" St SW Page G-2 G-1. Soils Map (City of Edmonds) RAM Engineering, Inc. Engineering and Drainage Report RAM No. 17-002 Johannessen Short Plat Lot 2 #10729 2261" St SW Page G-3 H. OPERATION AND MAINTENANCE GUIDELINES: These guidelines are intended to provide operation and maintenance instructions for the project's storm drainage control facilities. The owner is responsible for maintenance of storm drainage facilities within the property (private property owner system); the owner is not responsible for maintenance within the public right-of-way (City system). Private Property Owners: Private property owners are responsible for properly maintaining the stormwater infrastructure on their property to ensure it operates as designed. The City has developed an inspection program to ensure private property owners are properly maintaining their stormwater systems. City System: City crews perform maintenance activities on the entire storm drainage system, including inspection and cleaning of catch basins, street sweeping, emergency flooding response, creek maintenance, inspection and monitoring of private stormwater detention systems. Operation and Maintenance Requirements for private property owner system: This manual is not comprehensive; although it explains the intended operation of the various components of the drainage system, and suggests a routine of inspection and maintenance, it cannot anticipate every problem. Once a historical record of maintenance is established, it may be prudent to alter the routine. It is recommended that maintenance records be kept, and that the records be reviewed periodically. Concept of Operation: The drainage design is shown and described in the site development engineering plans and report. The approved site development plans and report should be retained by the owner and used as a reference to identify drainage facilities outlined in this manual. Conveyance Systems. The design objective in pipe sizing was to convey the large storm events without the water surface exceeding the ground elevation. Frequent overtopping of the pipe system in a particular area might indicate a downstream blockage. Overtopping of the drain systems at the catch -basins is an indication that maintenance is required. Stormwater Infiltration Trench/Dry Well System. The private onsite infiltration trench/dry well systems consist of excavated trench/pit filled with drain rock per the City Standard detail (Handout #E72 B, Figure A-3). The infiltration trench/dry well system has been designed to infiltrate most storm event; if an extraordinary event was to occur or multiple back to back large storm events occurred the upstream catch -basins may overtop and overflow into the street system. If regular overtopping of the catch basin is experienced the system shall be thoroughly cleaned and inspected. Over a period of time siltation of the infiltration bed can occur (especially if the system and upstream catch basin are not inspected and cleaned regularly) and replacement of the rock in the infiltration system may be required. RAMEngineering, Inc. Engineering and Drainage Report RAM No. 17-002 Johannessen Short Plat Lot 2 #10729 226t" St SW Page H-1 The following pages outline standard general maintenance criteria for the project's drainage facilities. For additional and updated maintenance information visit the Washington State Department of Ecology's web -site at: http://www.ecy.wa.gov/programs/wq/wghome.htmI MAINTENANCE REQUIREMENTS ECDC Section 18.30.090 requires privately -owned stormwater management facilities, such as LID BMPs be properly maintained. The owner of the property is the responsible party for such maintenance. The system must be kept in good working order. The entire system should be inspected once per year. An improperly maintained BMP may cause private property or street flooding. Contact the City Engineering Division for maintenance information. The City may make periodic inspections of BMPs to ensure they are operating properly. ECDC Section 18.30.100 contains the enforcement provisions the City can use to ensure the system is properly maintained. General Infiltration Maintenance Criteria Provision should be made for regular and perpetual maintenance of the infiltration basin/trench, including replacement and/or reconstruction of the any media that are relied upon for treatment purposes. Maintenance should be conducted when water remains in the basin or trench for more than 24 hours after the end of a rainfall event, or when overflows occur more frequently than planned. For example, off-line infiltration facilities should not have any overflows. Infiltration facilities designed to completely infiltrate all flows to meet flow control standards should not overflow. Removal of accumulated debris/sediment in the basin/trench should be conducted every 6 months or as needed to prevent clogging, or when water remains in the pond for greater than 24 hours after the end of a rainfall event. RAM -ngineering, In, Engineering and Drainage Report RAM No. 17-002 Johannessen Short Plat Lot 2 #10729 2261" St SW Page H-2 Appendix V-A: BMP Maintenance Tables Ecology intends the facility -specific maintenance standards contained in this section to be conditions for determining if maintenance actions are required as identified through inspection. Recognizing that Permittees have limited maintenance funds and time, Ecology does not require that a Permittee perform all these maintenance activities on all their stormwater BMPs. We leave the determination of importance of each maintenance activity and its priority within the stormwater program to the Permittee. We do expect, however, that sufficient maintenance will occur to ensure that the BMPs continue to operate as designed to protect ground and surface waters. Ecology doesn't intend that these measures identify the facility's required condition at all times between inspections. In other words, exceedance of these conditions at any time between inspections and/or maintenance does not automatically constitute a violation of these standards. However, based upon inspection observations, the Permittee shall adjust inspection and maintenance schedules to minimize the length of time that a facility is in a condition that requires a maintenance action. Table V-A.1: Maintenance Standards - Detention Ponds Maintenance Defect Conditions When Results Expected When Component Maintenance Is Needed Maintenance Is Performed Any trash and debris which exceed 1 cubic feet per 1,000 square feet. In general, there should be no visual evidence of Trash &Debris dumping. Trash and debris cleared from site If less than threshold all trash and debris will be removed as part of next scheduled maintenance. Any poisonous or nuisance vegetation which may constitute No danger of poisonous General a hazard to maintenance vegetation where maintenance personnel or the public. personnel or the public might normally be. (Coordinate with Poisonous Any evidence of noxious weeds local health department) Vegetation and as defined by State or local noxious weeds regulations. Complete eradication of noxious weeds may not be possible. (Apply requirements of adopted Compliance with State or local IPM policies for the use of eradication policies required herbicides). Contaminants and Any evidence of oil, gasoline, No contaminants or pollutants Pollution contaminants or other pollutants present. RAMEngineering, Inc. Engineering and Drainage Report RAM No. 17-002 Johannessen Short Plat Lot 2 #10729 2261h St SW Page H-3 Table V-A.1: Maintenance Standards - Detention Ponds Maintenance Defect Conditions When Results Expected When Component Maintenance Is Needed Maintenance Is Performed (Coordinate removal/cleanup with local water quality response agency). Any evidence of rodent holes if Rodents destroyed and dam or facility is acting as a dam or berm repaired. (Coordinate with Rodent Holes berm, or any evidence of water local health department; piping through dam or berm via coordinate with Ecology Dam rodent holes. Safety Office if pond exceeds 10 acre-feet.) Facility is returned to design function. Beaver Dams Dam results in change or function of the facility. (Coordinate trapping of beavers and removal of dams with appropriate permitting agencies) Insects destroyed or removed When insects such as wasps from site. Insects and hornets interfere with maintenance activities. Apply insecticides in compliance with adopted IPM policies Tree growth does not allow maintenance and inspection access or interferes with maintenance activity (i.e., slope mowing, silt removal, vactoring, Trees do not hinder or equipment movements). If maintenance activities. trees are not interfering with Harvested trees should be Tree Growth and access or maintenance, do not recycled into mulch or other Hazard Trees remove beneficial uses (e.g., alders for firewood). If dead, diseased, or dying trees are identified Remove hazard Trees (Use a certified Arborist to determine health of tree or removal requirements) Side Slopes of Pond Erosion Eroded damage over 2 inches Slopes should be stabilized deep where cause of damage is using appropriate erosion control measures ; e. .,rock RAMEngineering, Inc. Engineering and Drainage Report RAM No. 17-002 Johannessen Short Plat Lot 2 #10729 2261h St SW Page H-4 Table V-A.1: Maintenance Standards - Detention Ponds Maintenance Defect Conditions When Results Expected When Component Maintenance Is Needed Maintenance Is Performed still present or where there is reinforcement, planting of grass, potential for continued erosion. compaction. Any erosion observed on a If erosion is occurring on compacted berm embankment. compacted berms a licensed engineer in the state of Washington should be consulted to resolve source of erosion. Accumulated sediment that exceeds 10% of the designed Sediment cleaned out to Sediment pond depth unless otherwise designed pond shape and specified or affects inletting or depth; pond reseeded if Storage Area outletting condition of the necessary to control erosion. facility. Liner (if Applicable) Liner is visible and has more Liner repaired or replaced. Liner than three 1/4-inch holes in it. is fully covered. Any part of berm which has settled 4 inches lower than the design elevation If settlement is apparent, measure berm to determine amount of settlement Dike is built back to the design Settlements elevation. Settling can be an indication of more severe problems with the berm or outlet works. A licensed Ponds Berms engineer in the state of (Dikes) Washington should be consulted to determine the source of the settlement. Discernable water flow through pond berm. Ongoing erosion with potential for erosion to continue. Piping Piping eliminated. Erosion potential resolved. (Recommend a Goethechnical engineer be called in to inspect and evaluate condition and recommend repair of condition. RAMEngineering, Inc. Engineering and Drainage Report RAM No. 17-002 Johannessen Short Plat Lot 2 #10729 2261h St SW Page H-5 Table V-A.1: Maintenance Standards - Detention Ponds Maintenance Defect Conditions When Results Expected When Component Maintenance Is Needed Maintenance Is Performed Tree growth on emergency Trees should be removed. If root spillways creates blockage system is small (base less than problems and may cause failure 4 inches) the root system may of the berm due to uncontrolled be left in place. Otherwise the Tree Growth overtopping. roots should be removed and the berm restored. A licensed Tree growth on berms over 4 engineer in the state of feet in height may lead to piping Washington should be consulted Emergency through the berm which could for proper berm/spillway Overflow/ Spillway lead to failure of the berm. restoration. and Berms over 4 feet in height Discernable water flow through pond berm. Ongoing erosion with potential for erosion to continue. Piping Piping eliminated. Erosion potential resolved. (Recommend a Geotechnical engineer be called in to inspect and evaluate condition and recommend repair of condition. Only one layer of rock exists above native soil in area five square feet or larger, or any Emergency Emergency exposure of native soil at the Rocks and pad depth are Overflow/Spillway Overflow/Spillway top of out flow path of spillway. restored to design standards. (Rip -rap on inside slopes need not be replaced.) Erosion See "Side Slopes of Pond" Table V-A.2: Maintenance Standards - Infiltration Maintenance Defect Conditions When Maintenance Is Component I I Needed General Trash & Debris See Table V-A.1: Maintenance Standards - Detention Ponds RAMEngineering, Inc. Engineering and Drainage Report RAM No. 17-002 Results Expected When Maintenance Is Performed See Table V-A.1: Maintenance Standards - Detention Ponds Johannessen Short Plat Lot 2 #10729 2261h St SW Page H-6 Table V-A.2: Maintenance Standards - Infiltration Maintenance Conditions When Maintenance Is Results Expected Component Defect Needed When Maintenance Is Performed See Table V-A.1: Poisonous/Noxious See Table V-A.1: Maintenance Maintenance Vegetation Standards - Detention Ponds Standards - Detention Ponds See Table V-A.1: Contaminants and See Table V-A.1: Maintenance Maintenance Pollution Standards - Detention Ponds Standards - Detention Ponds See Table V-A.1: Rodent Holes See Table V-A.1: Maintenance Maintenance Standards - Detention Ponds Standards - Detention Ponds Water ponding in infiltration pond after rainfall ceases and appropriate time allowed for infiltration. Treatment basins should infiltrate Water Quality Design Storm Volume within 48 hours, and Sediment is removed empty within 24 hours after cessation of and/or facility is Storage Area Sediment most rain events. cleaned so that infiltration system works according to (A percolation test pit or test of facility design. 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). Filter Bags (if Filled with Sediment Sediment and debris fill bag more than Filter bag is replaced applicable) and Debris 1/2 full. or system is redesigned. By visual inspection, little or no water Gravel in rock filter is Rock Filters Sediment and Debris flows through filter during heavy rain replaced. storms. See Table V-A.1: Side Slopes of Erosion See Table V-A.1: Maintenance Maintenance Pond Standards - Detention Ponds Standards - Detention Ponds Emergency Tree Growth See Table V-A.1: Maintenance See Table V-A.1: Overflow Spillway Standards - Detention Ponds Maintenance RAMEngineering, Inc. Engineering and Drainage Report RAM No. 17-002 Johannessen Short Plat Lot 2 #10729 2261h St SW Page H-7 Table V-A.2: Maintenance Standards - Infiltration Maintenance Conditions When Maintenance Is Results Expected Component Defect Needed When Maintenance Is Performed and Berms over 4 Standards - Detention Ponds feet in height. See Table V-A.1: Piping See Table V-A.1: Maintenance Maintenance Standards - Detention Ponds Standards - Detention Ponds See Table V-A.1: Rock Missing See Table V-A.1: Maintenance Maintenance Standards - Detention Ponds Standards - Detention Ponds Emergency Overflow Spillway See Table V-A.1: Erosion See Table V-A.1: Maintenance Maintenance Standards - Detention Ponds Standards - Detention Ponds Pre -settling Ponds Facility or sump filled 6" or designed sediment trap depth of and Vaults with Sediment and/or sediment. Sediment is removed. debris Table V-A.S: Maintenance Standards - Catch Basins Maintenance Component Defect Conditions When Maintenance is Needed Results Expected When Maintenance is performed Trash or debris which is located immediately in No Trash or debris front of the catch basin opening or is blocking located immediately in inletting capacity of the basin by more than front of catch basin or 10%. on grate opening. General Trash & Debris Trash or debris in the basin that exceeds 60 ( ) No trash or debris in percent of the sump depth as measured from the catch basin. the bottom of basin to invert of the lowest pipe into or out of the basin, but in no case less than a minimum of six inches clearance from the Inlet and outlet pipes debris surface to the invert of the lowest pipe. free of trash or debris. RAMEngineering, Inc. Engineering and Drainage Report RAM No. 17-002 Johannessen Short Plat Lot 2 #10729 2261h St SW Page H-8 Table V-A.5: Maintenance Standards - Catch Basins Maintenance Results Expected Component Defect Conditions When Maintenance is Needed When Maintenance is performed Trash or debris in any inlet or outlet pipe No dead animals or blocking more than 1/3 of its height. vegetation present within the catch basin. Dead animals or vegetation that could generate odors that could cause complaints or dangerous gases (e.g., methane). 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 basin, but in no case less than No sediment in the Sediment a minimum of 6 inches clearance from the catch basin sediment surface to the invert of the lowest pipe. Top slab has holes larger than 2 square inches Top slab is free of or cracks wider than 1/4 inch. (Intent is to make holes and cracks. Structure Damage sure no material is running into basin). to Frame and/or Frame is sitting flush Top Slab Frame not sitting flush on top slab, i.e., on the riser rings or top separation of more than 3/4 inch of the frame slab and firmly from the top slab. Frame not securely attached attached. Maintenance person judges that structure is Basin replaced or unsound. repaired to design Fractures or standards. Cracks in Basin Grout fillet has separated or cracked wider than Walls/ Bottom 1/2 inch and longer than 1 foot at the joint of Pipe is and any inlet/outlet pipe or any evidence of soil t basin wall. secure at basin a particles entering catch basin through cracks. Settlement/ If failure of basin has created a safety, function, Basin replaced or repaired design Misalignment or design problem. standards. No vegetation blocking opening to basin. Vegetation Vegetation growing across and blocking more than 10 /o of the basin opening. No vegetation or root growth present. RAMEngineering, Inc. Engineering and Drainage Report RAM No. 17-002 Johannessen Short Plat Lot 2 #10729 2261h St SW Page H-9 Table V-A.S: Maintenance Standards - Catch Basins Maintenance Results Expected Component Defect Conditions When Maintenance is Needed When Maintenance is performed Vegetation growing in inlet/outlet pipe joints that is more than six inches tall and less than six inches apart. Contamination See Table V-A.1: Maintenance Standards - No pollution present. Detention Ponds and Pollution Cover/grate is in place, Cover Not in Cover is missing or only partially in place. Any meets design Place open catch basin requires maintenance. standards, and is secured Locking Mechanism cannot be opened by one Mechanism opens with Catch Basin Mechanism Not maintenance person with proper tools. Bolts proper tools. Cover Working into frame have less than 1/2 inch of thread. One maintenance person cannot remove lid after applying normal lifting pressure. Cover can be removed Cover Difficult to by one maintenance Remove (Intent is keep cover from sealing off access to person. maintenance.) Ladder is unsafe due to missing rungs, not Ladder meets design Ladder Ladder Rungs securely attached to basin wall, misalignment, standards and allows Unsafe rust, cracks, or sharp edges. maintenance person safe access. Grate opening Grate with opening wider than 7/8 inch. Grate opening meets Unsafe design standards. Trash and Debris Trash and debris that is blocking more than Grate free of trash and Metal Grates 20 /o of grate surface inletting capacity. debris. (If Applicable) Grate is in place, meets Damaged or Grate missing or broken member(s) of the the design standards, Missing. grate. and is installed and aligned with the flow path. RAMEngineering, Inc. Engineering and Drainage Report RAM No. 17-002 Johannessen Short Plat Lot 2 #10729 2261h St SW Page H-10 I. GEOTECHNICAL ENGINEERING REPORT Geotechnical Engineering Study. Prepared by: Earth Solutions NW, LLC Date: July 19, 2017 RAMEngineering, Inc. Engineering and Drainage Report RAM No. 17-002 Johannessen Short Plat Lot 2 #10729 2261h St SW Page 1-1 July 19, 2017 ES-5323 Ms. Kari Johannessen 10727 — 226th Street Southwest Edmonds, Washington 98002 Subject: Geotechnical Evaluation Johannessen Short Plat 10727 — 226t" Street Southwest Edmonds, Washington Reference: Lovell-Sauerland & Associates, Inc. Preliminary Development Plan, dated April 21, 2008 Earth I Solutions NWac Earth Solutions NW LLC • Geotechnical Engineering • Construction Monitoring • Environmental Sciences Department of Ecology (DOE) 2012 Stormwater Management Manual for Western Washington (SMMWM) Amended December 2014 United States Department of Agriculture Natural Resources Conservation Service Online Web Soil Survey (WSS) resource James P. Minard Geologic Map of the Edmonds East and Washington, 1983 Dear Ms. Johannessen: Part of the Edmonds West Quadrangles As requested, Earth Solutions NW, LLC (ESNW) has prepared this infiltration and geotechnical evaluation letter for the proposed development. Project Description The subject site located at 10727 — 226th Street Southwest in Edmonds, Washington, as illustrated on the Vicinity Map (Plate 1). The site consists of one residential tax parcel (Snohomish County parcel number 27032500310300) totaling approximately 2.35 acres of land area. The property is currently developed with a single-family residence and associated improvements located in the northwestern portion of the site; the remainder of the site consists primarily of yard areas and lightly forested land. -1805 - 136th Place N.E., Suite 201 • Bellevue, WA 98005 0 (425) 449-4704 • FAX (425) 449-4711 Ms. Kari Johannessen ES-5323 July 19, 2017 Page 2 Within the site, there is a knoll occupying the northwestern half of the site (existing residence). The ground drops off at about 8 to 38 percent grade to a low-lying, nearly level portion of the site. The subject site is bordered to the north, east, and west by residential structures and to the south by 2261" Street Southwest. Based on the site development plan provided to us, the existing single-family residential structure will remain and two new single-family residential structures will be constructed within the southern portion of the site. We anticipate grading activities will include cuts and fills to establish the planned building alignment. Based on the existing grades, we estimate cuts to establish building pad and foundation subgrade elevations will be on the order of five feet or less. However, grading plans were not available at the time this letter was prepared. Drywells will be incorporated into site designs as a means of stormwater management for new impervious surfaces. Site improvements will also include underground utility installations. At the time this letter was prepared, specific building load values were not available. However, we anticipate the proposed residential structure will consist of relatively lightly loaded wood framing supported on conventional foundations. Based on our experience with similar developments, we estimate wall loads on the order of one to two kips per lineal foot and slab - on -grade loading of 150 pounds per square foot (psf). If the above design assumptions are incorrect or change, ESNW should be contacted to review the recommendations in this evaluation. ESNW should review the final design to verify the geotechnical recommendations provided in this letter have been incorporated into the plans. Subsurface Conditions As part of this geotechnical evaluation, An ESNW representative observed, logged, and sampled two test pits on June 29, 2017, excavated at accessible locations within the proposed development area. The approximate locations of the test pits are depicted on Plate 2 (Test Pit Location Plan). Please refer to the test pit logs provided in Appendix A for a more detailed description of subsurface conditions. Representative soil samples collected at the test pit locations were analyzed in general accordance with the Unified Soil Classification System (USCS) and United States Department of Agriculture (USDA) methods and procedures. Topsoil and Fill Topsoil was observed extending to depths of approximately 4 to 6 inches below existing grades. The topsoil was characterized by dark brown color and fine organic material. Significant fill deposits were not encountered at the test pit locations during our fieldwork. Fill may be present, however, within proximity to existing structural improvements. Where fill is encountered during construction, ESNW should be consulted to evaluate the suitability for reuse as structural fill. Earth Solutions NW, LLC Ms. Kari Johannessen July 19, 2017 Native Soil ES-5323 Page 3 Underlying the topsoil, soil conditions at the test pit locations were observed to consist of poorly graded gravel with sand and poorly graded sand (USCS: GP and SP, respectively) outwash deposits. The native soil deposits were generally observed to be in a medium dense condition beginning at depths of approximately one to three feet below existing grades. Geologic Setting The referenced geologic map indicates the project location is underlain by Vashon advance outwash (Qva). The advance outwash is characterized primarily as sand and gravel deposit. The soil conditions observed at the test pit locations are generally consistent with the geologic mapping. Groundwater Groundwater was not encountered at the test pit locations at the time of our exploration. Perched seepage, however, may be encountered during site grading activities, particularly during the winter, spring, and early summer months. It is noted that groundwater seepage rates and elevations fluctuate depending on many factors, including precipitation duration and intensity, the time of year, and soil conditions. In general, groundwater flow rates are higher during the wetter, winter months. Based on subsurface conditions observed, we do not anticipate groundwater will impact the proposed infiltration facilities. Geotechnical Considerations Based on the results of our investigation, the proposed single-family structures can be supported on conventional spread and continuous footings bearing on undisturbed competent native soil, compacted native soil, or new structural fill. Based on the soil conditions encountered at the test sites, competent native soils suitable for support of foundations should be encountered beginning at depths of approximately one to three feet below existing grades. The soils encountered at the test pit locations generally have a low to moderate sensitivity to moisture based on the fines content of the soil. Compaction of the soil to the levels necessary for use as structural fill may be difficult during wet weather conditions. Where loose or unsuitable soil conditions are encountered at foundation subgrade elevations during site preparation activities, compaction of the soils to the specifications of structural fill, or overexcavation and replacement with granular structural fill will be necessary. Structural fill should consist of suitable granular soils compacted to 95 percent of Modified Proctor (ASTM D1557). Organic material exposed at foundation subgrade elevations must be removed and grades restored with structural fill. Earth Solutions NW, LLC Ms. Kari Johannessen ES-5323 July 19, 2017 Page 4 Provided the structures will be supported as described above, the following parameters can be used for design of the new foundations: • Allowable soil bearing capacity 2,500 psf Passive earth pressure 300 pcf (equivalent fluid) • Coefficient of friction 0.40 A one-third increase in the allowable soil bearing capacity can be assumed for short-term wind and seismic loading conditions. With structural loading as expected, total settlement in the range of one inch is anticipated, with differential settlement of about one-half inch. The majority of the settlements should occur during construction, as dead loads are applied. Seismic Considerations The 2015 IBC recognizes ASCE for seismic site class definitions. In accordance with Table 20.3-1 of ASCE, Minimum Design Loads for Buildings and Other Structures, Site Class D, should be used for design. In our opinion, the site is not susceptible to liquefaction. The native soil relative density and the absence of an established shallow groundwater table are the primary bases for this opinion. Drainage Surface grades must be designed to direct water away from the buildings. The grade adjacent to the buildings should be sloped away from the buildings at a gradient of at least 2 percent for a horizontal distance of at least four feet. In our opinion, perimeter footing drains should be installed at or below the invert of the building footings. ESNW can reevaluate the need for footing drains during construction, if requested. Infiltration Evaluation We understand stormwater will likely be managed by infiltration drywells located near the southern area of the subject site. The referenced 2014 Stormwater Management Manual for Western Washington (2014 SMMWW) was consulted, as required. As indicated in the Subsurface section of this letter, native soils encountered during our fieldwork were characterized primarily sand and gravel, outwash deposits. Based on the results of USDA textural analyses, the native soils were classified primarily as slightly to extremely gravelly sand with fines contents of about 0.1 to 0.9 percent (irrespective of gravel content). Earth Solutions NW, LLC Ms. Kari Johannessen ES-5323 July 19, 2017 Page 5 In -situ testing was completed in accordance with the Small-scale Pilot Infiltration Test (PIT) procedure, as outlined in Volume III, Chapter 3, Page 526 of the 2014 SMMWW. The testing was completed at depths of approximately four feet below existing grades at TP-1 and approximately four -and -one-half feet at TP-2. The testing was completed within the native sand and gravel outwash soils. The in -situ rate obtained during testing was 62 inches per hour at TP-1 and 55 inches per hour at TP- 2. Because the infiltration rate obtained from in -situ testing is considered to be a short-term rate, correction factors must be applied in order to determine a long-term design rate. The correction factors outlined below were used in accordance with Table III-3.3.1 of the 2014 SMMWW outlined in Volume III, Chapter 3, Page 529. The correction factors, along with the measured infiltration rate, were incorporated into the following equation: Ksat design = Ksat initial x CFI x CFt x CF,,,. • Measured (Ksat initial) 55 inches per hour • Site variability CF„ = 0.75 ■ Test method CFt = 0.5 ■ Degree of influent control CFm = 0.9 Long-term design infiltration rate (Ksat design) 18 inches per hour The design infiltration rate is applicable to facilities located in proximity to the infiltration test locations. Should revised locations be pursued, ESNW should be contacted to perform additional in -situ testing, as necessary. We recommend incorporating emergency overflow provisions in the facility designs. ESNW should be retained to observe the construction of infiltration facilities on the subject site in order to confirm soil conditions are as anticipated. Supplementary geotechnical recommendations may be provided at the time of construction, where necessary. Drywell Sizing Typical drywell sizing recommendations are based on the USDA classifications of the soils observed at the proposed bottom of facility. The referenced 2014 SMMWW provides sizing criteria for soils considered generally suitable for full infiltration (medium to coarse sands and gravels). Extremely gravelly sand was identified at the proposed bottom of facility locations. For sizing of roof runoff infiltration drywells, the site soils should be designed as course sands. In our opinion, the soils observed at the approximate bottom of facilities should be considered suitable for full infiltration applications. As stated in Volume II, Chapter 3, Page 454 of the DOE stormwater manual, drywells placed within coarse sands must have at least 360 cubic feet of gravel for every 1,000 square feet of tributary impervious surface. It is our opinion that an overflow should be incorporated into facility designs. Earth Solutions NW, LLC Ms. Kari Johannessen July 19, 2017 On -site Stormwater Management ES-5323 Page 6 Pursuant to City of Edmonds stormwater management requirements, implementation of on -site stormwater BMPs are required for proposed developments in accordance with specified thresholds, standards, and lists. The intent of BMP implementation is to infiltrate, disperse, and retain stormwater runoff on site to the extent feasible. We understand the proposed development intends to add over 5,000 square feet of new hard surface and therefore must comply with Minimum Requirements (MRs) 1 through 9, as outlined on Pages 42 through 70 of Volume I of the referenced stormwater manual. MR 5 concerns on -site stormwater management, and the viability of specific BMPs are to be evaluated for each type of proposed surface. The table below summarizes our evaluation of the required BMPs for MR 5, as outlined in the referenced stormwater manual, from a geotechnical standpoint. It is instructed in the referenced stormwater manual that BMPs are to be considered in the order listed (from top to bottom) for each surface type, and the first BMP that is determined to be viable should be used. For completeness, however, we have evaluated each listed BMP for the proposed surface types. AM Lawns and Landscaped Areas T5.13: Post -construction soil quality and depth (Volume V, Chapter 5) P,--r- T5.30: Full dispersion (Volume V, Chapter 5) T5.10A: Downspout full infiltration systems (Volume III, Chapter 3) T7.30: Bioretention (Volume V, Chapter 7) T5.14A: Rain Gardens (Volume V, Chapter 5) T5.10B: Downspout dispersion systems (Volume III, Chapter 3) T5.10C: Perforated stub -out connections (Volume III, Chapter 3) T5.30: Full dispersion (Volume V, Chapter 5) le? Yes or Infeasiibilitv Criteria None. No slopes greater than 33 percent are present. No The proposed project will not preserve at least 65 percent of the site. Based on results of the PIT, a design Yes infiltration rate of 18 in/hr can be considered for design. Based on results of the PIT, a design Yes infiltration rate of 18 in/hr can be considered for design. No Proper setbacks and vegetated flow paths are not available. Yes None. No T5.15: Permeable pavement (Volume V, Chapter 5) Yes T7.30: Bioretention (Volume V, Chapter 7) Yes T5.14A: Rain Gardens (Volume V, Chapter 5) T5.12: Sheet flow dispersion T5.11: Concentrated flow dispersion (Volume V, Chapter 5) No The proposed project will not preserve at least 65 percent of the site. Based on results of the PIT, a design infiltration rate of 18 in/hr can be considered for design. Based on results of the PIT, a design infiltration rate of 18 in/hr can be considered for design. Sheet flow dispersion and concentrated flow dispersion may be feasible, however, proper setbacks and vegetated flow paths may not be available. Earth Solutions NW, LLC Ms. Kari Johannessen July 19, 2017 Utility Support and Trench Backfill ES-5323 Page 7 In our opinion, the native soils anticipated to be exposed in utility excavations should generally be considered suitable for support of utilities. Organic or highly compressible soils encountered in the trench excavations should not be used for supporting utilities. The native soils should generally be suitable for use as structural trench backfill. Moisture conditioning of the soils will likely be necessary prior to use as structural backfill. Utility trench backfill should be placed and compacted to 95 percent of the modified proctor, or to the presiding jurisdiction specifications. Limitations The recommendations and conclusions provided in this geotechnical evaluation letter are professional opinions consistent with the level of care and skill that is typical of other members in the profession currently practicing under similar conditions in this area. A warranty is not expressed or implied. Variations in the soil and groundwater conditions observed at the test pit locations may exist, and may not become evident until construction. ESNW should reevaluate the conclusions in this geotechnical evaluation letter if variations are encountered. Should you require additional information, or have questions, please call. Sincerely, EARTH SOLUTIONS NW, LLC Adam Z. Shier, G.I.T. Staff Geologist Attachments: Plate 1 - Vicinity Map Plate 2 - Test Pit Location Plan Test Pit Logs Grain Size Distribution cc: Leif Helleren Construction, Inc. Attention: Mr. Leif Helleren (Email only) F; "cZ i NAL Henry T. Wright, P.E. Senior Project Engineer Earth Solutions NW, LLC iNd rN 'M Pon N rL W 3k 25 Eeiv J394 rL M —w:F!,? IS! 3— L 3N �4 hMW SV.C•X 35 3-: FL ST rL a X AF PL n X le H IIUAII r I )ki&ni��' LF1 yjyft:k JA, 2- NO mv- 9A. . PirwL a —:F y. Arp% FL a _% :� YA 3! .1-- rJ .75 Ile &w-7.r. 91 ZML i--Jw — K 5.57 Er 4w r 244GTK ST ;r T26.V" T, = N K R1II!&K.Tr`(W'fflYT"F F C C �53;,H , Y. sA LN 1 S�16 NjL IMIFY! NMI)h L M Jw 17% ip 1, sr-�! 'Vam7 it K. awn %mTnts r 11 H %r ■ UhD ti py M CA" Sf I OFMIT gym - I # H rH FP PJDjffi hM W, in .4& nil �Vls LL4 LU 9r. V— M % t4w PAGO -tf '4, 9 1� = MH Mill Iffn Air IN tip IwIST vCjrI1 a;L CAAI: ID sr A h ST 105FH 5T 114L U2 %R LI hvw IylI U, ME: OFri i'N Ney A IN, 'ME 1-r C lzin, %I L, .WFH� )r % mmyj 1 51 vini:E Rr %% I; M Reference: NORTH Snohomish County, Washington Map 474 Oil! By The Thomas Guide Rand McNally 32nd Edition 4 k: :z IF, 1z NOTE: This plate may contain areas of color. ESNW cannot be Drwn. MRS Date 07/19/2017 Proj. No. 5323 responsible for any subsequent misinterpretation of the information resulting from black & white reproductions of this plate. Checked AZS I Date July 2017 Plate 1 226TH STREET S.W. - — - - — - — - - — - - — - I I I I I I I I I I I I LEGEND TP-1 Approximate Location of — ■ — ESNW Test Pit, Proj. No ES-5323, June 2017 I LSubject Site __ Existing Building Proposed Building NORTH 0 30 60 120 1 "=60' Scale in Feet NOTE: The graphics shown on this plate are not intended for design purposes or precise scale measurements, but only to illustrate the approximate test locations relative to the approximate locations of existing and / or proposed site features. The information illustrated is largely based on data provided by the client at the time of our study. ESNW cannot be responsible for subsequent design changes or interpretation of the data by others. NOTE: This plate may contain areas of color. ESNW cannot be responsible for any subsequent misinterpretation of the information resulting from black & white reproductions of this plate. �coc ca a O a � � O U U N O J U) o-0 a o n E oLU �w Drwn. By M RS Checked By AZS Date 07/19/2017 Proj. No. 5323 Plate 2 Earth Solutions l VVLLC SOIL CLASSIFICATION CHART MAJOR DIVISIONS SYMBOLS TYPICAL GRAPH LETTER DESCRIPTIONS CLEAN Gw WELL -GRADED GRAVELS. GRAVEL - GRAVEL GRAVELS #►r MIXTURES, LITTLE OR NO AND FSAND INES GRAVELLY SOILS a ° ❑QO"C? POORLY -GRADED GRAVELS, (LITTLE OR NO FINES a o a o GP GRAVEL- SAND MIXTURES, LITTLE ❑ c0 OR NO FINES COARSE a GRAINED SOILS MORETHAN% GRAVELS WITH GM SILTY GRAVELS, GRAVEL - SAND - SE FINES �# a Q SILT MIXTURES FRACTION RETAINED ON NO. 4 SIEVE (APPREAMOUNT CI ABLECLAYEY GC GRAVELS, GRAVEL - SAND - FINES CLAY MIXTURES MORE THAN 50% SAND CLEAN SANDS Sw WELL -GRADED SANDS, GRAVELLY SANDS, LITTLE OR NO FINES OF MATERIAL IS AND LARGERTHAN SANDY NO.200 SIEVE SOILS SIZE (LITTLE OR NO FINES) SP POORLY -GRADED SANDS, GRAVELLY SAND, LITTLE OR NO FINES SANDS WITH FINES = SM SILTY SANDS, SAND -SILT MIXTURES MORE THAN 50% OF COARSE FRACTION PASSING ON NO. 4 SIEVE FINES) LE SC CLAYEY SANDS, SAND -CLAY AMOUNT OF M X URES INORGANIC SILTS AND VERY FINE ML SANDS, ROCK FLOUR, SILTY OR CLAYEY FINE SANDS OR CLAYEY SILTS WITH SLIGHT PLASTICITY r+�- INORGANIC CLAYS OF LOW TO MEDIUM PLASTICITY, GRAVELLY SILTS LIQUID LIMIT FINE AND GRAINED CLAYS LESS THAN 50 CLAYS, SANDY CLAYS, SILTY SOILS CLAYS, LEAN CLAYS OL ORGANIC SILTS AND ORGANIC — SILTY CLAYS OF LOW PLASTICITY MORE THAN S OF MATERIALL I MH INORGANIC SILTS, MICACEOUS OR DIATOMACEOUS SMALLER THANN FINE SAND OR NO.200 SIEVE SILTY SOILS SIZE SILTS AND IN CHLIQUID INORGANIC CLAYS OF HIGH GREATER THAN 50 EATER CLAYS PLASTICITY OH I ORGANIC CLAYS OF MEDIUM TO HIGH PLASTICITY, ORGANIC SILTS HIGHLY ORGANIC SOILS P�' PEAT, HUMUS, SWAMP SOILS WITH HIGH ORGANIC CONTENTS DUAL SYMBOLS are used to indicate borderline soil classifications. The discussion in the text of this report is necessary for a proper understanding of the nature of the material presented in the attached logs. Earth Solutions NW TEST PIT NUMBER TP-1 1805 - 136th Place N.E., Suite 201 Bellevue, Washington 98005 PAGE 1 OF 1 VAN Telephone: 425-449-4704 Fax: 425-449-4711 CLIENT Kari Johannessen PROJECT NAME Johannessen Short Plat PROJECT NUMBER ES-5323 PROJECT LOCATION Edmonds, Washington DATE STARTED 6/29/17 COMPLETED 6/29/17 GROUND ELEVATION TEST PIT SIZE EXCAVATION CONTRACTOR CLE GROUND WATER LEVELS: EXCAVATION METHOD AT TIME OF EXCAVATION --- LOGGED BY AZS CHECKED BY HTW AT END OF EXCAVATION ... NOTES Depth of Topsoil & Sod 4": soil AFTER EXCAVATION --- I W HW U _ W_ TESTS (6 ° O MATERIAL DESCRIPTION Qz 0 TPSL � ' 0.5 Dark brown, TOPSOIL Tan silty SAND with gravel, medium dense, moist MC = 6.60% SM MC = 3.20% 2 U Gray poorly graded GRAVEL with sand, medium dense, damp a �9 Op p a� MC = 3.00% Fines = 0.90% Qb [USDA Classification: extremely gravelly SAND] 5 GP O ° O� �b �a - - ° R4 Ob o [�� -becomes moist � � - MC = 11.70% 9.0 Test Pit terminated at 9.0 feet below existing grade. No groundwater encountered during excavation. No caving observed. Bottom of test pit at 9.0 feet. Earth Solutions NW TEST PIT NUMBER TP-2 1805 - 136th Place N.E., Suite 201 Bellevue, Washington 98005 PAGE 1 OF 1 Tax Telephone: 425-449-4704 Fax: 425-149-4711 CLIENT Kari Johannessen PROJECT NAME Johannessen Short Plat PROJECT NUMBER ES-5323 PROJECT LOCATION _ Edmonds, Washington DATE STARTED 6/29/17 COMPLETED 6/29/17 GROUND ELEVATION TEST PIT SIZE EXCAVATION CONTRACTOR CLE GROUND WATER LEVELS: EXCAVATION METHOD AT TIME OF EXCAVATION — LOGGED BY AZS CHECKED BY HTW AT END OF EXCAVATION -- NOTES Depth of Topsoil & Sod 6": grass AFTER EXCAVATION --- w U _ a �W TESTS U a 0 MATERIAL DESCRIPTION Q a= vd az = rn 0 TPSL .. 0.5 Dark brown TOPSOIL, roots Brown silty SAND with gravel, medium dense, moist - - MC = 7.60% SM MC = 2.80% 2.0 Gray poorly graded GRAVEL with sand, medium dense, damp ° Qv ° i7 O MC = 2.30% �O� [USDA Classification: extremely gravelly SAND] 5 Fines = 0.20% P ° C50 a D )Q a° 7.0 Gray poorly graded SAND, medium dense, moist - SP MC = 16.60% 9.0 [USDA Classification: slightly gravelly SAND] Fines = 0.10% Test pit terminated at 9.0 feet below existing grade. No groundwater encountered during excavation. No caving observed. Bottom of test pit at 9.0 feet. Ld 31�1 1 I INS �llil�ii iA millillin millillin llmmiiiiiiimmiiiiiii,s- lismillillismillillinm lins�ii lillin diil 1 I111 iiiiiiinm �m USDA: Gray Extremely Gravelly Sand. USCS: GP with Sand. TP-2 9.0oft. USDA: Gray Slightly Gravelly Sand. USCS: SP. 0 ■ Ft kM ENGINEERING, INC. Civil Engineering 1 Land Planning