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Stormwater_Report.pdfWESTERN ENGINEERS & SURVEYORS SURVEYORS • ENGINEERS • LAND USE CONSULTANTS 9740 Evergreen Way - Everett, WA 98204 P: (425) 356-2700 F: (425) 356-2708 W: WESI.CO Targeted Stormwater Report For EVANS Short Plat 20020 — 83RD AVE W EDMONDS, WASHINGTON City of Edmonds Project # PLN2018. Issue Date: May 18, 2018 Revision Date: PREPARED BY: ERIC HAINES, E.I.T. REVIEWED BY: JESSE JARRELL, P.E. o5,lg-tS CLIENT(S): SIMON EVANS WESTERN ENGINEERS, INC. 20020 — 83' AVE W Job No. 17-1701-A EDMONDS, WA 98026 EVANS — 2 Lot S.P. 1. ATTACHMENT "A" DRAINAGE INFORMATION SUMMARY FORM Project Name: EVANS — 2 LOT S.P. Project Engineer: WESTERN ENGINEERS, INC. Project Applicant: SIMON EVANS EDMONDS, WA Project Total Area: 0.581 Acres Project Development Area: 0.265 Acre Number of Lots: 2 Summary Table Drainage Basin Information Individual Basin Designation A B C D On -site Development Area 0.265 ac. Type of Storage Proposed NIA DISPERSION Approximate Storage Volume NIA Soil types ALDERWOOD Type C WESTERN ENGINEERS, INC. PROJECT:17-1701-A EVANS — 2 Lot S.P. Minimum Requirement # 1: Stormwater Site Plan Executive SuniniaH y The proposed project is located at 20020 83RD AVE W in the City of Edmonds, within Snohomish County, Washington. More generally, the site is located in Section 19, Township 27 North, and Range 4 East of the Willamette Meridian in Edmonds, Washington. Please refer to the Vicinity Map attached in the next section. The project contains approximately 0.581 acres, which is covered by an existing house, concrete patio, shed, detached garage, and asphalt driveway. The preliminary proposal is to subdivide 0.581 acres into two housing lots with associated utilities. The existing ' house, patio, and the driveway on proposed Lot 2 will be retained, both proposed lots will access 83" Ave W via a proposed 12' wide paved shared driveway along the northern side of the property. The project is to be designed to the 2012 (With 2014 Updates) WADOE Stormwater Design Manual and City of Edmonds 2017 Stormwater Codes. Drainage management for new hardscape areas will primarily be provided by roof drain perforated pipe stub out trenches (T5.1 OC) and driveway dispersion (T5.12) BMPs. Disturbed vegetated areas will be amended per soil quality BMP T5.13. All utilities to be provided by existing services on 83'd Ave W fronting the site. Existinl! Conditions Summary The site is partially developed with an existing house, concrete patio, shed, detached garage and asphalt driveway on the western half of the. Existing on -site vegetation primarily consists of residential lawn with tree cover. The site generally slopes northwest to southeast at slopes ranging from 2% to 8%. From the Soil Conservation Service Map of Snohomish County, the site contains Alderwood Urban Land Complex type soils. Please refer to the soil map and descriptions attached later in this report. WESTERN ENGINEERS, INC. PROJECT: 17-170 1 -A EVANS — 2 Lot S.P. y .V F a G O cnrpmn.^.t TiHE BOWL P? OFS EDMONDS ands VICINITY MAP O P E R R I N V I L L E Lynndalc Park Costco Business �,. Picnic Shelter D Trader Joe's `je ` 5» Edmonds Lynn+r.00d r Comrn,_inity college y �t• O -- SEATTLE HEIGHTS C) Yost Park atztn st SW21 Ali, St SW rdmontl.; w000.-my High School T w , ,Owlish li a FrImond s Cntupwz ro ' WinCo Foods mil% n 9 Premcra Rlue Cras_, 2s00h SI sav Red Dragon Casin0.32r,ti, st ,t;, ZE ry 99 Ranch Market Q �•a s Esperance STGATE WE MAP TAKEN FROM GOOGLE MAPS WESTERN ENGINEERS & SURVEYORS SURVEYORS • ENGINEERS • LAND USE CONSULTANTS EVANS SHORT PLAT EDMONDS, WA 98026 SCALE: DATE: 04/04/18 CHECKED: JAJ 9740 Evergreen Way, Everett WA 98204 1" =—1,000' (425) 356-2700+ (425) 356-2708 (FAX) EMH JOB NUMBER: FILE NAME: westernengineers.com BY: 17-1701-A 171701A/VICINITYMAP WESTERN ENGINEERS, INC. PROJECT: 17-1701 -A EVANS — 2 Lot S.P. OFFSITE ANALYSIS Site reconnaissance was done by Eric Haines, E.I.T. of Western Engineers Inc. on April 03, 2018. Weather during the investigation was mostly cloudy with a temperature around 45 degrees. A: Upstream Analysis It appears from the topography of the site that upstream sheet flows may occur from lawn areas to the north and west. However, during the site visit, no evidence of any significant flows was observed. Any contributions to surface flows from off -site are expected to be minor and no other significant upstream flows appear to enter the property. B: Downstream Analysis Please refer to the Downstream Analysis Map attached in the next section for a detailed depiction of the downstream drainage course. The site is partially developed with an existing SFR, patio, shed, detached garage and driveway. The majority of the site slopes from northwest to southeast towards the storm system and sheet flows directly into an underground storm system on the west side of 83rd Avenue W (see photo 3). Intercepted flows enter a series of catch basins on the west side of 83rd Avenue W. Flows entering the catch basins are routed approximately 1025 feet south in a storm system along the west side of 83rd Ave were it enters into an open ditch system going through Pine Ridge Park(see photos 3 through 5). Access into the ditch system was not possible due to dense vegetation. No visible drainage problems were observed during the initial and follow-up field inspections. Refer to the following pages for Aerial and Downstream Map. Drainage Complaints There are no found drainage complaints for this site. WESTERN ENGINEERS, INC. PROJECT: 17-1701-A EVANS — 2 Lot S.P. BASIN AND AERIAL MAPS WESTERN ENGINEERS, INC. PROJECT:17-1701-A EVANS — 2 Lot S.P. AERIAL AND DOWNSTREAM MAP TAKEN FROM GOOGLE EARTH WE, ENGINEERS & SURVEYORS SURVEYORS •ENGNEERS•LAND USE CONSULTANTS 9740 Evergreen Way, Everett WA 98204 (425) 356-2700 (425) 356-2708 (FAX) westcrncnL'inccrs.com EVANS SHORT PLAT EDMONDS, WA 98026 SCALE: None DATE: 04/04/18 CHECKED: JAJ BY: EMH JOB NUMBER: FILE NAME: 17-1701-A I Aerial Map WESTERN ENGINEERS, INC. PROJECT:17-1701-A EVANS — 2 Lot S.P. DOWNSTREAM PHOTOGRAPHS WESTERN ENGINEERS, INC. PROJECT:17-1701-A EVANS — 2 Lot S.P. DOWNSTREAM PHOTOGRAPHS PHOTO 2: Figure to the Right: Looking easterly along the proposed driveway WESTERN ENGINEERS & SURVEYORS SURVEYORS • ENOWEERS • LAND USE CONSULTANTS PHOTO 1: Figure to the Left: Looking southeast from the existing driveway EVANS SHORT PLAT EDMONDS, WA 98026 9740 Evergreen Way, Everett WA 98204 SCALE: None DATE: 04/04/18 SHEET: 1 OF 3 (425) 356-2700 (425) 356-2708 (FAX) JOB NUMBER: FILE NAME: westernengineers.com BY: EMH 17-1701-A Downstream LDOC WESTERN ENGINEERS, INC. PROJECT: I7-1701-A EVANS — 2 Lot S.P. DOWNSTREAM PHOTOGRAPHS PHOTO 4: Figure to the Right: Looking south at a catch basin located along 83'd Ave W WESTERN . ENGINEERS & SURVEYORS SURVEYON$ - ENOMRS • LAND USE CONSULTANTS 9740 Evergreen Way, Everett WA 98204 (425) 356-2700 (425) 30-2708 (FAX) westernengineers.com PHOTO 3: Figure to the Left: Looking west at the manhole on the east side of the site EVANS PROPERTY EDMONDS, WA 98026 SCALE: None DATE: 4/04/18 SHEET: 2 OF 3 JOB NUMBER: FILE NAME: BY: EMH I 17-1701-A D.S.PHOTOS.DOC WESTERN ENGINEERS, INC. PROJECT: 17-1701-A EVANS — 2 Lot S.P. DOWNSTREAM PHOTOGRAPHS PHOTO 6: Figure to the Right: Direction of flow into Pine Ridge Park WESTERN ENGINEERS & SURVEYORS SURVEYORS • ENGINEERS - LAND USE CONSULTANTS 9740 Evergreen Way, Everett WA 98204 (425) 356-2700 (425) 39' -2708 (FAX) PHOTO 5: Figure to the Lcft: Looking north along 83'�d Ave W EVANS PROPERTY EDMONDS, WA 98026 SCALE: None DATE: 4/03/18 SHEET: 3 OF 3 JOB NUMBER: FILE NAME: BY: EMH 17-1701-A D.S.PHOTOS.DOC WESTERN ENGINEERS, INC. PROJECT: I 7-1701-A EVANS — 2 Lot S.P. Minimum Requirement # 2: SWPPP Narrative Element #1: Mark Clearing Limits Clearing limits have been shown on the Temporary Erosion and Sedimentation Control Plans. Element #2: Establish Construction Entrance A temporary construction entrance has been shown at the location of the proposed driveway that is to access 83`d Ave W. All vehicles shall be free of debris prior to leaving the site. Element # 3: Control Flow Rates Flow rates during construction are to be contained through the installation of silt fencing. Element # 4: Install Sediment Controls Sediment controls mainly consist of installing silt fencing along the western boundary of the clearing/construction limits. Element # 5: Stabilize Soils All soils disturbed during site grading will be stabilized by use of the most appropriate BMP method available. These consist of short-term and long-term solutions. Short-term methods consist of compaction of the soils by vibratory roller or bulldozer. Long-term methods consist of straw covering over the soils (this is in the case of the project becoming dormant for greater than 1 month). At this time no wintertime grading or construction activities will occur. During construction periods longer than 1 working week (7 days) where the soils are exposed and un- worked will use the proscribed methods in the Storm Water Management Manual for Western Washington to reduce sedimentation transported offsite. If winter grading is conducted, all exposed soils shall be covered within 2 days. Element # 6: Protect Slopes There are no known steep or significant slopes on -site; therefore, slope protection is not necessary. Element # 7: Protect Drain Inlets The off -site catch basins along the west side of 83rd Ave W will be provided sediment protection with catch basin inserts or equivalent. Element # 8: Stabilize Channels and Outlets Channels and drainage outlets are not needed around the proposed development area on site. No stabilization is necessary. Existing channels or drainage outlets located within 500-feet of the property of the property should be routinely inspected for debris that may dam and/or aid erosion. WESTERN ENGINEERS, INC. PROJECT:17-1701-A EVANS — 2 Lot S.P. Element # 9: Control Pollutants All pollutants from construction vehicles will be contained and disposed of in the approved manner consistent with state environmental policies. Any vehicle maintenance will be performed by authorized mechanics using drip pans and waste containment vessels. All pollutants will be disposed offsite at approved facilities. Element # 10: Control De -Watering De -watering of the site is not expected. If dewatering of the site is needed, all groundwater removed shall be retained and recharged into the ground after de - watering has been finalized. Element # 11: Maintain BMP's All Temporary Erosion and Sedimentation Control (TESC) devices and equipment will be inspected and maintained on a weekly basis if not sooner, based on storm events contributing to runoff. When construction is complete and the site is stabilized, any existing sediment will be removed and stabilized onsite. Element # 12: Manage the Project A general construction manager will manage the project for or by the owners. The construction manager shall maintain all of the above items in order to minimize sediment transport and turbid water leaving the site. His job will entail continual observation of the grading operations to ensure minimal effects to adjacent properties and offsite waterways. Element # 13: Protect Low Impact Development BMPs Proposed dispersion flow path areas and soil amendment areas will be protected from compaction when feasible. Minimal Requirement # 3: Water Pollution Source Control All proposed development is to consist of residential construction. No water pollution source control is needed. Minimum Requirement # 4: Preservation of Natural Drainage Systems and Outfalls, and provisions of off -site mitigation No changes to the existing drainage systems and outfalls are proposed with this development. Minimum Requirement #5 On -Site Storm Water Management The project results in less than 5,000 square feet of new/replaced hard surfaces and is considered a Category 2 project. Category 2 projects must evaluate Minimum Requirements 1 through 9 and select on -site stormwater BMPs according to List 2 for each proposed hard surface. Note that due to geometry, spacing between the property lines and the site consisting of an erosion hazard in the southeast portion of the site, WESTERN ENGINEERS, INC. PROJECT: 17-1701 -A EVANS — 2 Lot S.P. infiltration and dispersion BMPs are generally infeasible. Refer to List 2 below for appropriate BMP selection or infeasibility description: Lawn and landscaped areas: • Post -Construction Soil Quality and Depth in accordance with BMP T5.13 in Chapter 5 of Volume V. (To be used in disturbed vegetated areas) Roofs feasibility description: 1. Full Dispersion per BMP T5.30 or Downspout Full Infiltration per BMP T5.1 OA. i. Full Dispersion is infeasible due to insufficient flow path length and lack of native forest vegetation. Full Infiltration is infeasible due to lack of spacing between property line and proposed edge of house 2. Bioretention per Volume V, Chapter 7. i. Due to the fact that the entire site consists of inadequate soil depth for roof drain infiltration, bioretention facilities are infeasible. 3. Downspout Dispersion Systems in accordance with BMP T5.1 OB. i. Due to the fact that there is not enough space between the property line and the proposed edge of house, along with the fact that the southeastern portion of the site is considered an erosion hazard area, downspout dispersion is infeasible for roof runoff. 4. Perforated Stub Out Connections BMP T5.10C i. Perforated Stub Out has been selected for this project because it is a feasible option and all high priority options are infeasible. Other Hard Surfaces feasibility description: 1. Full Dispersion per BMP T5.30 i. As noted above, Full Dispersion is infeasible due to insufficient flow path length and lack of native forest vegetation. 2. Permeable Pavement per BMP T5.15 i. Due to the fact that the entire site consists of inadequate soil depth to provide adequate separation between pavement subgrade and the hardpan layer, permeable pavement is infeasible. 3. Biorention per Volume V, Chapter 7. i. Due to the fact that the entire site consists of inadequate soil depth for infiltration, bioretention facilities are infeasible. 4. Sheet Flow Dispersion in accordance with BMP T5.12 or BMP T5.11. i. Sheet Flow Dispersion BMP T5.12 has been selected for new shared driveway and individual driveway areas. Minimum Requirement # 6: Runoff Treatment Due to the site proposing less than 5,000 sf. of new pollution generating impervious surfaces, less than 3/ acres of forest to lawn conversion, and less than 2.5 acres of forest to pasture conversion, runoff treatment is not required. WESTERN ENGINEERS, INC. PROJECT: 17-170 1 -A EVANS — 2 Lot S.P. Minimum Requirement # 7: Flow Control ry Due to the site proposing less than 5,000 sf of new/replaced impervious surface, less than3/ acres of forest to lawn conversion, less than 2.5 acres of forest to pasture conversion, flow control is not required. Refer to the summary below for an overview of the hardscape calculations. Total Area of the Site Total Clearing Area = 25,327 sf. (0.581 Ac.) = 11,550 sf. (0.265 Ac.) Existing Site Before Clearing Impervious area: Existing SFR Roof = 2,347 sf. ± Existing Concrete Patio = 1,287 sf. ± Existing Driveway to Remain= 1,874 sf. + Existing Shed and Garage = 582 sf. ± Total = 6,090 sf. (0.140 Ac.) Pervious area: Existing Lawn Area = 19,237 sf. (0.442 Ac.) Prouosed Site Impervious area: Existing SFR Roof = 2,347 sf. ± Existing Concrete Patio = 1,287 sf. f Existing Driveway to'Remain= 1,874 sf. + Existing Shed and Garage = 582 sf. ± New Driveway Extension = 540 sf. ± New Lot 1 SFR Roof = 2,800 sf. ± New Lot 1 Parking Addition = 1,000 sf. + Total = 10,430 sf. (0.239 Ac.) New/Replaced Impervious Surface = 4,340 sf. Pervious area: Existing Lawn to Remain = 7,687 sf. (0.176 Ac.) Proposed Amended Lawn = 7,210 sf. (0.165 Ac.) WESTERN ENGINEERS, INC. PROJECT: 17-1701 -A EVANS — 2 Lot S.P. Minimum Requirement # 8: Wetland Protection There are no known wetlands on -site. Note that defined clearing limits, silt fencing, and large vegetated spaces shown on the LDA plan will protect any downstream wetlands or streams. Minimum Requirement # 9: Operation and Maintenance Manual BMP T5.13 Post -Construction Soil Quality and Depth Maintenance • Soil quality and depth should be established toward the end of construction and once established, should be protected from compaction, such as from large machinery use, and from erosion. • Soil should be planted and mulched after installation. • Plant debris or its equivalent should be left on the soil surface to replenish organic matter. WESTERN ENGINEERS, INC. PROJECT:17-1701-A EVANS — 2 Lot S.P. Table V-4.5.2(5) Maintenance Stanaaras - vaccn esasins Results Maintenance Defect Defect Conditions When Maintenance is Expected ComponentMain- p onent Needed tenance is performed No Trash or debris loc- Trash or debris which is located imme- ated imme- diately in front of the catch basin opening or diately in is blocking inletting capacity of the basin by front of catch more than 10%. basin or on Trash or debris (in the basin) that exceeds grate open- 60 percent of the sump depth as measured i ng. from the bottom of basin to invert of the low- No trash or est pipe into or out of the basin, but in no debris in the Trash & case less than a minimum of six inches catch basin. Debris clearance from the debris surface to the invert of the lowest pipe. Inlet and out- letpipes free Trash or debris in any inlet or outlet pipe of trash or blocking more than 1/3 of its height. debris. Dead animals or vegetation that could gen- No dead General erate odors that could cause complaints or animals or dangerous gases (e.g., methane). vegetation present within the catch basin. Sediment (in the basin) that exceeds 60 per- cent 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 No sediment Sediment less than a minimum of 6 inches clearance in the catch from the sediment surface to the invert of the basin lowest pipe. Structure Top slab has holes larger than 2 square Top slab is Damage to inches or cracks wider than 1 /4 inch. (Intent free of holes Frame and/or is to make sure no material is running into and cracks. Top Slab basin). Frame is sit 2014 Stormwater Management Manual for Western Washington Volume V - Chapter 4 - Page 838 WESTERN ENGINEERS, INC. PROJECT: I 7-1701-A EVANS — 2 Lot S.P. Table V-4.5.2(5) Maintenance Standards - Catch Basins (continued) Results Maintenance Defect Conditions When Maintenance is Expected When Main- Componenti Needed tenance is performed Frame not sitting flush on top slab, i.e., sep- ting flush on the riser rings aration of more than 3/4 inch of the frame or top slab from the top slab. Frame not securely and firmly attached attached. Basin Maintenance person judges that structure is replaced or unsound. repaired to Fractures or rac in Grout fillet has separated or cracked wider design stand- Basin Walls/ than 1/2 inch and longer than 1 foot at the ards. Bottom joint of any inletloutlet pipe or any evidence Pipe is of soil particles entering catch basin through regrouted cracks. and secure at basin wall. Basin Settlement/ If failure of basin has created a safety, func- replaced or repaired to Misalignment tion, or design problem. design stand- ards. No veget- Vegetation growing across and blocking ation block - more than 10% of the basin opening. ing opening to basin. Vegetation Vegetation growing in inlet/outletpipejoints No veget- that is more than six inches tail and less grown or root than six inches apart. growth present. Contamination See "Detention Ponds" (No. 1). No pollution and Pollution present. Cover is missing or only partially in place. Catch basin Cover Not in Any open catch basin requires main- cover is Catch Basin Place tenance. closed Cover Locking Mech-Mechanism cannot be opened by one main- Mechanism �anisrn Not tenance person with propertools. Bolts into opens with 2014 Stormwater Management Manual for Western Washington Volume V - Chapter 4 - Page 839 WESTERN ENGINEERS, INC. PROJECT:17-1701-A EVANS - 2 Lot S.P. Tnhla V.d_5.2(5) Maintenance Standards - Catch Basins (continued) Results Maintenance Defect Conditions When Maintenance is Expected When Main - Component Needed tenance is performed Working frame have less than 1/2 inch of thread. proper tools. One maintenance person cannot remove lid 'Cover can be Cover Difficult after applying normal lifting pressure. removed by to Remove (Intent is keep cover from sealing off access one main - tenance per - to maintenance.) son. Ladder meets design stand Ladder is unsafe due to missing rungs, not ards and Ladder Ladder Rungs securely attached to basin wall, mis- allows main - Unsafe alignment, rust, cracks, or sharp edges. tenance per- son safe access. Grate open - Grate opening Grate with opening wider than 7/8 inch. ing meets Unsafe design stand- ards. Metal Grates Trash and 'Trash and debris that is blocking more than Grate free of (If Applic- Debris :20% of grate surface inletting capacity. trash and debris. able) Grate is in Damaged or Grate missing or broken member(s) of the place and Missing. grate. meets design standards. WESTERN ENGINEERS, INC. PROJECT: 17-170 1 -A EVANS — 2 Lot S.P. Table V 4.5.2(7) Maintenance Standards - Energy Dissipaters Results Expec Maintenance Conditions When Maintenance is ed When Main Components Defect Needed tenance is Performed External: Missing or Only one layer of rock exists above nat Rock pad replaced to Moved ive soil in area five square feet or lar- design stand- Rock ger, or any exposure of native soil. ards. Rock Pad Rock pad Erosion Soil erosion in or adjacent to rock pad, replaced to design stand- ards. Pipe Pipe cleaned/ - Plugged Accumulated sediment that exceeds flushed so that with Sed- 20% of the design depth. it matches iment design. Not Dis- Visual evidence of water discharging Trench Dispersion Trench charging at concentrated points along trench (normal condition is a sheet flow of redesigned or Water Prop- water along trench). Intent is to prevent rebuilt to stand- erly erosion damage. ards. Perforations Over 1/2 of perforations in pipe are Perforated pipe cleaned or Plugged. plugged with debris and sediment. replaced. 2014 Stormwater Management Manual for Western Washington Volume V - Chapter 4 - Page 841 WESTERN ENGINEERS, INC. PROJECT:17-1701-A EVANS — 2 Lot S.P. Table V-4.5.2(7) Maintenance Standards - Energy Dissipaters (continued) Results Expec- Maintenance Defect Conditions When Maintenance is ,ted When Main Components Needed tenance is Performed Water Maintenance person observes or Flows Out ut receives credible report of water flow- Facility rebuilt Top of T ofibutor ing out during any storm less than the or redesigned trop design storm or its causing or appears to standards. Catch likely to cause damage. Basin. Receiving Water in receiving area is causing or No danger of Area Over- has potential of causing landslide prob landslides. Saturated lems. Internal: Worn or Damaged Structure dissipating flow deteriorates Structure post, to 1/2 of original size or any con- replaced to Manhole/Chamber Baffles, centrated worn spot exceeding one design stand - Side of square foot which would make struc- ards. ture unsound. Chamber Other See "Catch Basins" (No. 5). See "Catch Bas Defects ins" (No.5). WESTERN ENGINEERS, INC. PROJECT: 17-1701 -A EVANS — 2 Lot S.P. APPENDIX I Drainage Plan WESTERN ENGINEERS, INC. PROJECT: 17-1701-A ••2' lml WDE t�4a ROW SPRFADfIr, 6' YPl pM I� 1 -aru n • nvo WWA,�rcl® sar o [f 4W1 K % MU N41-20' LEG ROXPA]H � I••• rb/ M r••C -� X NDE 10. WWAM n. PAIN ix f�0 Wsrzo,' Pow � "`110a •� 4IDiN canRm�uloiP m p K2 sNJz DPr) O Oaf R W1 vrm.e wsa cwm D 410E GR 06PERSgN S1RIP 6 1Di NECD D Fdi to Q W.T ORNEWIY 9MPAC6 PAOVmFFD DRNE➢2' 0RA01N0 DDES ADT F6UL7 M CONCDnRATED T "/ f1f1M4 2' WIDE GPA4II SmP IB ® uama craw owa w.no4 twW R[W%YD TDR ALL ASP/W.i ANO/OR CDACREiE DRNEMHY 9AYAC6 NEW DRIVEWAY SECTION DETAIL NOT M SCA E ,.1oPAW,K --- �•--- �•,. �. Pam», tea+ TRENCH X-SECTION •ce•ma�w �--►• F•Y Iwr,/ iLF YroRAN�1GE MRu �6•rt- ➢1sf lrr.00 Y4 r Wia Y•t0 w-_ �"� PLAN VIEW OF ROOF m .. PERFORATED TIGHTUNE CONNECTION �� 1om y •Am 41' El5E1 W WIDTH 2D' fir - 2r rAm" w m —D' - 20' PAVEWEM WIDTH i� �I 2' M DI 12• AC PA'ADr' z' 's/e' me 4' 1 1/4' CSBC APPROVED SDBORAOE ACCESSEASLIMTDETAE. x2r ro s^•, r • 71: AREA Oi ORMWAY LINT 6 it 6 ro BE RZRElBEO m fY 11K, NE lni, SECJ9, T.M. R.4E, W. Cf1YOFEDAfONOS, WASYMMON 1 j 1 srxy mom t 1 IDYF11 ff-1164 t 1 t1pER ff.I21.2' 1 J 1 � APPROX l dx r v 1 Ssett O1 EX CB ' RIM=1' r IE 12' RCP(B)=AMOBW.ffi' I Lz I �I J,4.7 I BI fail E Omo :"ill EX S9MH RIM 103.89' IE IN(N)=392.39' IE CW(S)=392.N EX CB RIM=40197' IE 12' RCP(N)-399.62' IE 12RCP(S)=399.BJ' EVANS — 2 Lot S.P. APPENDIX II SOIL INFORMATION WESTERN ENGINEERS, INC. PROJECT: 17-1701 -A EVANS - 2 Lot S.P. USDA SOIL MAP m Snohomish County Area, Washington (WA661) Snohomish County Area, Washington (WA661) Map Acres percent Unit Map Unit Name In of A0I Symbol A0I 5 Alderwood-Urban 0.6 100.0% land complex, 2 to 8 percent slopes Totals for Area of 0.6 100.00/6 Interest USDA SOIL MAP LEGEND 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: 6 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 • Natural 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 WESTERN ENGINEERS, INC. PROJECT: 17-1701 -A EVANS — 2 Lot S.P. Frequency of flooding: None Frequency of ponding: None Available water storage in profile: Low (about 3.0 inches) Interpretive groups Land capability classification (irrigated): None specified Land capability classification (nonirrigated): 4s Hydrologic Soil Group: B Other vegetative classification: Limited Depth Soils (G002XN302WA) Minor Components Mckenna Percent of map unit: 2 percent Landform: Depressions Norma Percent of map unit: 2 percent Landform: Depressions Terric medisaprists • Percent of map unit: 2 percent • Landform: Depressions WESTERN ENGINEERS, INC. PROJECT:17-1701-A EVANS — 2 Lot S.P. APPENDIX III SOIL AMENDMENT WESTERN ENGINEERS, INC. PROJECT:17-1701-A