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APPROVED STM_BLD2023-0433+Storm_Drainage_Report+4.6.2023_2.59.21_PM+3468243840 Daley Street Single Family Residence 840 Daley Street Edmonds, WA 98020 BLD 2023 - Stormwater Site Plan Report Prepared for: Peter and Jia Tang Date: April 4, 2023 OF AS l� �Q \36508W� IONn1. -4-/3/202S Prepared by: Rob Long, PE RAM Fnginininring, Inr, 19109 3611 Ave W, Suite 103, Lynnwood WA 98036 (425) 678-6960 RAMengineeringinc.com Job No. 23-002 840 Daley Street Single Family Residence Introduction: This summary report provides site design information for a single-family residence at 840 Daley Street. This report includes stormwater analysis to support permit review and approval. The property is located on the south side of Daley Street (west of 9t" Ave W), in the southwest 1/4 of Section 24, Township 27N, Range 3E, W.M. Site Address: 840 Daley Street Edmonds, WA 98020 Tax Parcel Number: 00450700300002 Applicant: Peter and Jia Tang 648 Bell Street Edmonds, WA 98020 Phone: 206-372-2584 TABLE OF CONTENTS SECTION PAGES A. Project Overview.............................................................................................................................. 5 B. Existing Conditions Summary........................................................................................................... 1 C. Developed Site Hydrology................................................................................................................ 5 D. Soils Reports................................................................................................................................... 20 E. Construction SWPPPP Requirements................................................................................................ 2 F. Operation and Maintenance Guidelines............................................................................................ 5 R.4MEngineering, Inc. RAM No. 23-002 840 Daley Street SFR Stormwater Site Plan Report Page A. PROJECT OVERVIEW: This report provides engineering information for the proposed construction of a single family residence on a 0.19 acre parcel; the project is located on the south side of Daley Street (west of 91h Ave W) in the City of Edmonds. The applicant, Peter and Jia Tang proposes to remove the existing residence and all existing hard surface to construct a new single family residence with an attached accessory dwelling unit (ADU) on the project site. This report provides the evaluation for the new single family residential development. Summary of Minimum Requirements for Category 1 Project: Minimum Requirement #1 — Preparation of Stormwater Site Plan. The proposed site development consists of disturbing the entire 0.19 acres site with the removal of all existing improvements onsite. The project will create/replace about 4,244 sf of hard surface area; thus, the project is classified as a Category 1 project per the City's classification system. Per ECDC 18.30, Category 1 projects must comply with Minimum Requirements No. 1 through No. 5. The civil site development plans and this report have been prepared to address the projects impacts. Minimum Requirement #2 — Construction Stormwater Pollution Prevention (SWPPP). A construction Stormwater Pollution Prevention Plan (SWPPP) has been 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 E. The total site disturbance area (0.19 ac) of the project will not exceed one acre, thus a formal Notice of Intent application for NPDES coverage will not be made to the Department of Ecology. 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. RAMEngineering, Inc. RAM No. 23-002 840 Daley Street SFR Stormwater Site Plan Report Page A-1 Minimum Requirement #4 —Preservation of Natural Drainage Systems and Outfalls. The natural flow path and outfall of the site that generally slopes northerly is to the municipal separate storm sewer system (MS4) within Daley Street. Daley Street is full sloped to the north and stormwater is collected along the north gutter line and the stormwater pipe and catch basin along the north side of Daley Street. The project will discharge to the existing MS4 within Daley Street and therefore maintain the site's natural outfall. Additional discussion of the downstream path is included in Section C below. Minimum Requirement #5 — Onsite Stormwater Management. The proposed project is a category 1 project, thus is subject to the City's on -site stormwater management BMPs found in "List No. 1" in the City's code. A site -specific geotechnical evaluation of the site's soils and nearby slope areas (offsite to the west) demonstrates that infiltration is a not a viable option for stormwater management onsite. The project geotechnical evaluation recommends infiltration not be used due to reasonable concerns about erosion and slope failure of nearby slopes. Existing slopes about 75 feet west of the subject site have been classified as "erosion hazard" slopes. Additionally, adequately flow length paths are not available for any dispersion type BMP. Only post construction soil amendment and BMP detention pipe are proposed for onsite stormwater BMP. A summary table of the project Stormwater Management BMPs are provided below. RAMEngineering, Inc. RAM No. 23-002 840 Daley Street SFR Stormwater Site Plan Report Page A-2 MR#5 Stormwater Management BMP List No. 1 Evaluation Lawn and landscaped areas: BMP Viable Limitations / Infeasibility Criteria BMP T5.13: Post -Construction Soil Quality and Depth Limitation: Considered infeasible on slopes greater than 33 (Volume V, Chapter 11) Yes percent are present., BMP T5.13 shall be applied to the site post construction. Roofs: BMP T5.30: Full Dispersion Infeasibility: A viable vegetated flow path 50 or 100 feet (Volume V, Chapter 3) No and less than 20% is not achievable onsite. Infeasibility: The project geotechnical evaluation BMP T5.10A: Downspout Full Infiltration Systems recommends infiltration not be used due to reasonable (Volume V, Chapter 4) No concerns about erosion and slope failure of nearby slopes. Existing slopes about 75 feet west of the subject site have been classified as "erosion hazard" slopes. Infeasibility: The project geotechnical evaluation BMP T5.14 Rain Gardens recommends infiltration not be used due to reasonable (Volume V, Chapter 11) or No concerns about erosion and slope failure of nearby slopes. BMP Bioretention Existing slopes about 75 feet west of the subject site have (Vollumeame V, Chapter 7) been classified as "erosion hazard" slopes. BMP T5.106: Downspout Dispersion Systems Infeasibility: A viable vegetated flow path 50 or 100 feet (Volume V, Chapter 4) No and less than 20% is not achievable onsite. Detention Vaults or Pipes A detention vault/pipe is viable and proposed to meet (Edmonds Stormwater Addendum) Yes Minimum Requirement No. 5. Infeasibility: The project geotechnical evaluation BMP T5.10C: Perforated Stub -out recommends infiltration not be used due to reasonable (Volume V, Chapter 4) No concerns about erosion and slope failure of nearby slopes. Existing slopes about 75 feet west of the subject site have been classified as "erosion hazard" slopes. Other Hard Surfaces: BMP T5.30: Full Dispersion Infeasibility: A viable vegetated flow path 50 or 100 feet (Volume V, Chapter 3) No and less than 20% is not achievable onsite. BMP T5.10A: Full Infiltration Infeasibility: The project geotechnical evaluation (Volume V, Chapter 4) recommends infiltration not be used due to reasonable BMP T5.15: Permeable Pavement No concerns about erosion and slope failure of nearby slopes. (Volume V, Chapter 5) Existing slopes about 75 feet west of the subject site have been classified as "erosion hazard" slopes. BMP T5.14 Rain Gardens Infeasibility: The project geotechnical evaluation (Volume V, Chapter 11) or recommends infiltration not be used due to reasonable No concerns about erosion and slope failure of nearby slopes. BMP T7.30: Bioretention Existing slopes about 75 feet west of the subject site have (Volume V, Chapter 7) been classified as "erosion hazard" slopes. BMP T5.12: Sheet Flow Dispersion Infeasibility: A viable vegetated flow path 50 or 100 feet (Volume V, Chapter 3) No and less than 20% is not achievable onsite. Detention Vaults or Pipes A detention vault/pipe is viable and proposed to meet (Edmonds Stormwater Addendum) Yes Minimum Requirement No. 5. RAMEngineering, Inc. RAM No. 23-002 840 Daley Street SFR Stormwater Site Plan Report Page A-3 Parcel (Vicinity) Map: QUARTER SECTION I TOWNSHIP IN W.B.L. I RANGE E.W.M. 7 —'- SW 24 27 3 A�.... �._e..e..M.e.er Centerline ------- Lot Block Lr Section -- City mts I � � I Gov Lot Subdiv — ROW Quarter -- Tax Acct • '," W '�� ..'.... ` /inch 200(eer Major Water— Other Lot------- Vac ROW - - -- 16th----- Easement: :........... A prndurlrflhr Av.e=.nr4 Off— Jlap•ohreAon Vr••b Jl. JYJJ ,Snohomish C—My. N'ashin8lnn - ^. Minor Water Other Subdiv — Vac Lot NW-24-27-03 77 4 7 18 2 EDMONDS 2 S 6 10 x 7ro7 ry� 8 77 W Nz Mt/-245 CREEK' IDE ! ALOH 7565 s 26', O6 ( OS W' 07 lb "s 5 18 -D6S wiroa i�i ,I, - GLEN- SF 2 2 B 2-223 ` -208 7 'S 2 2 209 2-071LEN K SITE .. 6� 3 rConoo 2-2`' 2-225 2-251 09 +� �pv 11 _I9aas P -07-76 2 207 10.°. r �as�0r ?6 — I6ls�i si I- i f G s 0 a, r Sm I a �� o g5ac �Si n12 - 111011116 ... G t. 'PIIIIIII 9 Iff, N NN oil 19 11111 IN op rNab ill E COMMODORE C0400 (9546) CONDO CH MBRE cY Ire,el P e`Tp o+CONDOMINIUM 3 (8%9) RAN Engineering, Inc. RAM No. 23-002 NW-25-27-03 -----.---- WAU 840 Daley Street SFR Stormwater Site Plan Report Page A-4 Site Plan: CS 1 TMRE 148 ORA VANED ORATE N-1080O62 RW 17 B 25050 - - 10'1 E 164J0 (1N_E) DRIVEWAY I, IE 184.J0 (OUT-W) DRIVEWAY z- --- --- ----.--._i._- i_,- -.-.s --- -- --- _-_ --- EXSSCO EX 10 CONC STORM RIM i]i t7 —SD —SD--.-5O-- SO -- SO-- —SD--—SD ----SD.— --SO-- SO SD - I I ; rmA B_µ____µ___—µµ—W� SAW 3 I LWE n)—_�, 3 UDUTY TRENGII PER a, S. DWG N0. A T CU-400 @ DU-4ro (SEE SHEET DT-01 @ � Ex B' Pl2 SEWE5 DALEY S / I � PATCHING/0WRLAY N07E WS SHEET) _- HG I i l REPLACE CURB AS NECESSARY PER CYTY�— ��----SS--- 6 SO E-1677 I I I Sm DID Na M-520 (SEE SHEET OT-01 6' S5 Tf1P-161.0E I @ CONSMCRON NO1 TARS SHEET). I SfPARA DON-6. ]' I INSTALL CONC M"AY ; CR i i APPROACH PER OTY STD I GAS IE-17_16 I I 172.7 FL M NO. M-`� 6" S° TOP-11.0' I ; 1727 MC (SEE SIEEi DT-Oq � SEPARADON-f.0' I. I 172..9 a 11.5 I r I ; 1729 TBC I7J5 C IBC. ; __ ______ 17.17t FL -_-_- _-----_-- -_--_- A i < - _ -- -_ _ ------ t --- 4A 4 Pl t7 4 CONC DRIVEWAY I N-IOS59.56 fC -_ - I E 1N/0550 I 17Z8�_ _____I76- - - RBI 17400 l �' 4.1E 172.W (W-E) I 174.0 - 4-E 172.00 (OUT--S*) N 89593E Wc_74.,9SY c �� .� ts.+ TT11.�r. ,.'�yyyS..- ' AN DRAW SOU° LOCKNG LID c NOS IPRO OHANNEI. DRA/N N-1053262 - I 1 OM E OFTA N SHY RWf72 0 Mu IIS JO � 1 �4•�;L�* L� i 1 REE DETAu cw SHY Or-OzJ 6' IE 171.71 (IN S) A B' IE 17L 72 (OUT E) �i J4'-J6' AIL S O O S r- ' T h { DRY UDUIES f yk (SEE DETAIL SHEET 01-01) ' ^yL �h� 6" PVC ROOF @ FOODNG °RAIN �O CONNECDgI O I.Ox M/N •` I f110M WA1FR NETER ro Hd/SE 1 ' - I 1 WE TO BE W TKIED WILS N WATER UNE) 1------2°_ese SOLO 2 \ Y OF EDMID CITY \ LOT 12 , 6 PM N-IOb.T&61 � C'OIfRED ,. '. � I VOL. 2, P EE-MIOM .66] (I Pam, 175.0 FC 175.0 FG MOO4' lE 171.B7. (W-S) A(� GARAGE 1 -' 1 6' E 1".B7(I .N-SE) 'I � i N-IOSJSJ9 / FF I75.00 1 F=fOMSBS e' E rn.e7 (our-N) I I I RW r7s1D ce2 III 6- E 172.00 OUT-N*) TYPE SMIC I ! SOL. IMCra4 LOT 13 _ SOLID G DD 4 PVC F 49 M LOCKING LID �) 1 i DRAW O1.o<MW -10-11 I0062 W RIM 175, 0 / gillI PROPOSED HOUSE 4" IE 171.90 (IN -NE) < - 3 N MAIN FF 175. 56 /£ 169.10 (IN-W) ff 6' IE /69.20 iD1YOONOS BLK 81 igl •� I �) Ii :. 2/1 PO. 39 =1 III I I I III 1 I'n SSW IE 172, R �I ______PADO______.. I i� II ap Y� I CPAAM li ;I I 1`Of „I WDCOl I4 I s PVC @ HOUSE PVC GARAGE SERucE o _ I 17 118 III 3 h E=IOM265 �_ 2.01 MIN III F+ MARE iiw (W-E) 5 '�' 175.18 FG III IP 4' E 7240 (OUT--N) P I ns 1E M g G COVERED -- - 1 = (j j O19-LNCTNL-6'SAMTARv - - PORCH DC /. CLEANOUT 0 PROPERTY UNEPER )-- - (SEEdSPEET DTTY S7D °NG -0Y)N0.'55-200 WA K 1�7&Q (S2X_72 f)BIE JZ'�r LAAMMPHOIE C V MIDI 1/e 2F BSBL - - - - - - L f7b47: - 1 a LATERA LCONMA OF EA15T SERER 8 3 I LATRAL (CONTRAC1d1 ro VERIFY 4" PVC > Y CHANNEL DRAW LOCADON PMOR ro CGNsiRUC M) N-1047a6J I7S 00 SERER IAERAL TO BE TVD BY ME E- 101232 SAPRO CHANNEL ppROI£D EQUAL DRAIN OR dTr OF EOMONOS SENER DEPARTMENT M OVERAWE /F LWE 4' E I7J00 lW-E) ISFE DETAK LW SHr Or-o1J / I CAN BE RE-USM IF DE UNE Is 4" E n1D0 (OUT-I{9 /. 1 DAMAGED 00? NOT A 6' UNE FROM F) 1 DE MAW TO DE PRO WTY LW& J ME SENER LATERAL SHALL BE SSLD 1 $ 76Bf I I REPLACED E 166.PE;.:'''---L------ I -----L GRA t'FL DRVEwar -----K8936J�-E__ZA9P� ------ ,A.;. ._.< ^^- j _ '_ - - - - --_- FX.B"CONC.SEMER ALLEY GRAVEL . .- SS ALLEY ----SS--.--SS----SS—_— SS —.—_—SS-- -------------- ---- CITY OF EDMbNOS BLK 81 LOT 30 LOT 29 VOL. 2, IPG. 39 LOT 28 RAN Engineering, Inc. RAM No. 23-002 840 Daley Street SFR Stormwater Site Plan Report Page A-5 B. EXISTING CONDITIONS SUMMARY Existing Conditions. The total site consists of 8,201 sf (0.19 acres) and is currently occupied by an existing single-family residence, in -ground pool, and detached garage. The site's existing garage is access via an alley along the south boundary of the subject site. The existing house is surrounded by grass lawn and landscape areas. The site is surrounded by single family residences to the west, south and east; and Daley Street along the north boundary of the site (see aerial photo below). The site generally slopes in the northerly direction at a relatively flat to moderate slopes with only 4 feet of drop across the site (from south to north). No define drainage courses are found on -site and stormwater runoff would sheet flow northerly. No stream or wetlands are located onsite; Shell Creek is located about 250 feet southwest of the site. Additional discussion of the local drainage basin and downstream path is discussed in Section C of this report. Soils: In accordance with the project's site -specific geotechnical engineering evaluation by Earth Solutions NW, LLC the on -site soils consist of poorly graded sand with and without silt (USCS: SP-SM and SP) advance outwash deposits. The subject site are generally consistent with Alderwood-Everett series soil. Full soils description is included in the project's site specific geotechnical engineering study by Earth Solutions NW, LLC. Aerial Photo (City of Edmonds GIS, 2020 photo) RAMEngineering, Inc. RAM No. 23-002 840 Daley Street SFR Stormwater Site Plan Report Page B-1 C. DEVELOPED SITE HYDROLOGY: Developed Conditions. The proposed project includes the construction of a single family residence with an attached accessory dwelling unit, and associated driveway and utilities. All existing structures and impervious (hard) surface onsite will be removed/replaced with the site development; landscaping and grass lawn around the new residence will stabilize the site upon building construction. The project proposes to create and/or replace 4,244 sf of hard surface with the complete site development, all existing hard surface will be removed with the project site development. The following is a summary of the proposed new/replaced hard surface areas: Total Hard Surface to Mitigated = 4,244 sf (0.0974 ac) Roof Area = 3,160 sf Walkway/Patio Area = 271 sf Driveway Area = 813 sf Total Pervious Surface (Lawn/Landscape) = 4,077 sf (0.0936 ac) Lot Lawn/Landscape Area = 4,077 sf In accordance with the Edmonds City Code (18.30) Category 1 projects shall meet MR#5 (see discussion in Section A above) and provide on -site stormwater management. To meet these criteria, the proposed hard surfaces of the site shall implement BMPs from "List No. 1" or meet the LID performance standard. As discussed above in the MR#5 evaluation above in Section A, and individual lot stormwater BMP detention pipe (Edmonds Storm water Addendum Section 6.3) will be utilized to manage the project's new/replaced hard surfaces. BMP T5.13: Post -Construction Soil Quality and Depth will be applied to the disturbed pervious areas of the site development. The total proposed new replaced hard surface of 4,244 sf will be mitigated with an individual lot detention pipe systems. The onsite detention pipe systems have been sized in accordance with the Edmonds Storm water Addendum simplified sizing approach, below is a summary of the system: Detention Pipe Sizing Calculations: ■ Hard Surface = 4,244 sf ■ Required 36" Detention Pipe = 33.95 ft (0.008 x 4,244 sf)l ■ Provided 36" Detention Pipe = 34 ft 1. Per Edmonds Stormwater Addendum simplified sizing approach Section 6.3.1. RAMEngineering, Inc. RAM No. 23-002 840 Daley Street SFR Stormwater Site Plan Report Page C-1 OLI SOLID LOCKING LID EL.1 LOCKING 4+LID EL. 175.30f EMERGENCY OVERFLOW 1 i 6" PVC 8" IE 171.72 FDE 36CPEP R£S7RICTOR 01 Aft TEN7/ON TANK 6" PVC lE 169.20 2'-8" CPEP S7UB CONNEC7ION ® 0.5% 3'-8" CPEP S7UB 2 CB TYPE I CONNECTION ® 0.5% PVC CAP ON BOTTOM "+ WITH 0.5" ORIFICE (SEE FLOW CONTROL STRUCTURE DETAIL SD-301 ON 7HIS SHEET) CB 48" - TYPE 1I DETENTION SYSTEM DETAIL DETENTION SYSTEM SIZING 36" DETENTION PIPE REQUIRED 4,244 X 0.008 = 33.95 LF REO D (34 LF 36" PIPE PROPOSED) (PER EDMONDS STORMWA7ER ADDENDUM 6.3.1) 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 attached City of Edmonds Standard Detail SD-642 criteria for BMP T5.13: Post -Construction Soil Quality and Depth. RAMEngineering, Inc. RAM No. 23-002 840 Daley Street SFR Stormwater Site Plan Report Page C-2 UNDISTURBED NATIVE VEGETATION UNDISTURBED NATIVE SOIL 2" ORGANIC MULCH 3" OF COMPOST INCORPORATED INTO 5" OF SITE SOIL (TOTAL AMENDED DEPTH OF 9.5", FOR A SETTLED DEPTH OF 8") SUBSOIL SCARIFIED 4" BELOW COMPOST AMENDED LAYER (12" BELOW SOIL SURFACE) 2" ORGANIC MULCH 6" IMPORTED TOPSOIL MIX (COMPACTED DEPTH) SUBSOIL IS SCARIFIED 6" BELOW IMPORTED TOPSOIL MIX UNDISTURBED PLANTS (SEE NOTE 1) UNDISTURBED TURF (LAWN) AREAS (SEE NOTE 1) m OPTION 1 — NO DISTURBANCE PLANTING BEDS TURF (LAWN) AREAS 11�LflJ�fl�I�fl�IIfl�Lh�I�fl��fl�I�fl� m 8" UNDISTURBED TURF/LAWN/LANDSCAPE UNDISTURBED NATIVE SOIL STEEP SLOPE NOTE: AMENDED SOILS SHOULD NOT BE INSTALLED ON FINISHED SLOPES EXCEEDING 33%. AREAS EXCEEDING 33% SHALL BE STABILIZED PER THE ENGINEER/GEOTECH OF RECORD. 3RASS: SEED OR SOD 1.75" OF COMPOST INCORPORATED INTO 6.25" OF SITE SOIL (TOTAL 4MENDED DEPTH OF 9.5", FOR A SETTLED DEPTH OF 8") SUBSOIL SCARIFIED 4" BELOW COMPOST AMENDED LAYER ,12" BELOW SOIL SURFACE) OPTION 2 — AMEND IN PLACE OR STOCKPILE AND AMEND GENERAL NOTES: PLANTING BEDS TURF (LAWN) AREAS 1. AREAS OF NO DISTURBANCE SHALL BE FENCED AND EXISTING GRASS: SEED VEGETATION AND SOIL SHALL BE OR SOD PROTECTED FROM CONSTRUCTION 1 I'1f1 �I1-1 I1 11-1 11 I IMPACTS. I L 11L 1 I 1=1 III I I I M III 11=1 11=1 11=1 11=1 I I I —I —I 1=1 I=1 I I—III=1 1=1 I IEl 11=1 11=1 11=1 11=1 I I III-1I I� �I I I —I �I I1=1 III —I I I� I1=1I I� I1=1I1=1I 2. TO MEASURE SETTLED DEPTH, II=11FI1 11=III—III—III—III II —III —III —III —III 6" IMPORTED WATER SOIL SUFFICIENTLY TO , TOPSOIL MIX FULLY SATURATE WITHOUT III II II —III —III II III II — III—;ITE III II COMPACTED CAUSING EROSION. III= �- I— �TEI III 111=1 I —I I I I I I III-1I DEPTH) III-III-II=III-11F111=1 6" III=111 I -11 =11 3. COMPOST SHALL MEET SPEC. III, _I- _� =1� VA'�-1-� II- 11 'm1 1=fj�j -I \ REQUIREMENTS IN THE 2017 IIFj�\�j_IIN '1-' SUBSOIL IS EDMONDS STORMWATER \j II SCARIFIED 6" ADDENDUM (CHECKLIST 7). BELOW 4. COMPACTION OF TOPSOIL (WHERE IMPORTED REQUIRED) TO BE TO 85% (MAX) 12' \ \/\ TOPSOIL MIX OF THE MAXIMUM DRY DENSITY OPTION 3 — IMPORT TOPSOIL PER MODIFIED PROCTOR TEST (ASTM D 1557). OF EDMONDS POST CONSTRUCTION SOIL QUALITY AND DEPTH REVISION DATE APRIL 2021 T PUBLIC WORKS STANDARD DEPARTMENT DETAIL Fs t �g9� APPROVED BY: R. ENGLISH S D - 642 R.4MEngineering, Inc. 840 Daley Street SFR RAM No. 23-002 Stormwater Site Plan Report Page C-3 Offsite Basin Analysis. The site is located in the Shell Creek watershed basin. The Shell Creek basin is an urban basin that collects stormwater runoff from primarily residential areas in the City Edmonds and ultimately discharges flows north/northwesterly to Puget Sound via the Shell Creek/Shell Creek By-pass (see attached watershed map). The subject site slopes north and sheet flows site runoff to the municipal separate storm sewer system (MS4) within Daley Street. Daley Street is full sloped to the north and stormwater is collected along the north gutter line and the stormwater pipe and catch basin (MS4) along the north side of Daley Street. The MS4 flows westerly down Daley Street right-of-way to the base of the adjacent sloped area and then turns north up 8t" Ave N, about 350 feet from the site. The MS4 stormwater pipe system does not discharge directly into the Shell Creek stream; the stormwater runoff stays within a piped system that by-passes Shell Creek. The Shell Creek By-pass system was installed in 1990 to reduce stream bank erosion and provide additional conveyance capacity for the Shell Creek basin. The Shell Creek By-pass system travels in a north/northwesterly direction until it eventually discharges into the Puget Sound about 0.87 miles from the site. See the Downstream Drainage Facility Map and Watershed Basin Map, delineating the downstream path to the discharge point to Shell Creek By-pass, attached below. Downstream Drainage Facility Map (City of Edmonds GIS) PUGET SOUND - DISCHARGE 0.87 MILES FROM THE SITE 9 n 9 •��'� 4 na tea, �� :m �o • Cep / • e b �� J Pa i / - o SITE a - g o O 0 L RAMEngineering, Inc. RAM No. 23-002 840 Daley Street SFR Stormwater Site Plan Report Page C-4 Watershed Basin Map FIGURE B - 1 N CITY OF EDMONDS , ° WATERSHEDSu �```h ad I I _ I _ Deer Creek_jIPerrinville Edmonds MarshPuget Sound Meadowdale A'r--� Edmonds Way - Puget Sound Piped Moadowdale B Fruitdale -Shell Creek Good Hope Pond Shellabarger fiam st s j Halls Creek r—' Southwest Edmonds A Hindley Creek Southwest Edmonds B � Out£ II Creekstilthouse Creek Lake Ballinger Stilthouse Creek Lund's Gulch _ Talbot Park A YamotPa �� L i MeadowdaleA Talbot Park B i �-�Meadowdale8 � Terrace Creek �� Terrace Creek Northstream Westgate Pond L. Outfall Creek Willow Creek O LOW LOOo a,000 6.000 g,Wo ! - �- d P 'nville rear Pug ounce m - o� Sin=2,000ft �. Talbot Park m Ibbi Park B o; Li No warranty a arty sart, including —,q, fitness, or —han Wity - a—p mthis product. March 30, 2010 Y. N lFrultdale - 3 A I I u, m SITE-"r—`"' tnr — I , 196tM1 St 6W . orthstream I _ _oath St SW j I i * 600d Hope Pond i 206th 6t 6W I Puget Sound Pli ----zoecn St SW i' Edmonds Marsh__ a a°°°d°' -v t Shell -----/'-rr t -c ShelGlfargeF� // i\ m vm I_ 3 i 2zams w �-- ill'w Creekfi 2210, St SW Deer Creek j ----- -7 �.� 23— St SW Wach.: nad---- i Edmonds Way =� Southwest Edmonds A ` Lake Ballinger Q EI :aoth st SW ____-_______,N zostn'st/zoom stsw--- RAN Engineering, Inc. RAM No. 23-002 840 Daley Street SFR Stormwater Site Plan Report Page C-5 D. SOILS REPORTS: 1. Geotechnical Evaluation Letter Prepared by: Earth Solutions NW, LLC Date: March 28, 2023 Pages: 19 MAN =ngineering, Inc. RAM No. 23-002 840 Daley Street SFR Stormwater Site Plan Report Page D-1 March 28, 2023 ES-9040 PNT Group, LLC 5603 — 230t" Street Southwest Mountlake Terrace, Washington 98043 Attention: Mr. Peter Tang Subject: Geotechnical Evaluation Proposed Single -Family Residence 840 Daley Street Edmonds, Washington Reference: Pacific Coast Surveys, Inc. Topographic Survey, dated January 31, 2023 Tang Residence Option "B" Earth Solutions NW«C Earth Solutions NW LLC Geotechnical Engineering, Construction Observation/Testing and Environmental Services James P. Minard Geologic Map of the Edmonds East and Part of the Edmonds West Quadrangles Washington, 1983 United States Department of Agriculture (USDA) Web Soil Survey (WSS) Department of Ecology Stormwater Management Manual for Western Washington Amended December 2014 City of Edmonds Edmonds Stormwater Addendum, dated June 30, 2022 Edmonds City Code Chapter 18.30 (Stormwater Management) Chapter 23.80 (Geologically Hazard Areas) Dear Mr. Tang: As requested, Earth Solutions NW, LLC (ESNW) has prepared this geotechnical evaluation for the proposed single-family residence. As part of our scope of services, we completed a subsurface exploration, laboratory and engineering analyses, and prepared this written report with our findings and recommendations for the proposed project. Based on our evaluation, the proposed project is feasible from a geotechnical standpoint. 15365 N.E. 90th Street, Suite 100 • Redmond, WA 98052 • (425) 449-4704 0 FAX (425) 449-4711 PNT Group, LLC March 28, 2023 Protect Description ES-9040 Page 2 The subject site is at 840 Daley Street in Edmonds, Washington, as illustrated on the attached Vicinity Map (Plate 1). The site consists of one tax parcel (Snohomish County parcel number 00434208101000). The site is currently developed with a single-family residence and associated improvements. The site topography gently descends to the west; a steep slope area is located approximately 50 to 75 feet west of the subject site. We understand the subject site will be redeveloped with a new single-family residence and associated improvements. Grading activities will likely include cuts of up to about four feet to establish the planned building alignments. Site improvements will also include underground utility installations. We understand the proposed residential structure will consist of relatively lightly loaded wood framing supported on conventional foundations. Based on experience with similar projects, we anticipate wall loads will be on the order of 1 to 2 kips per linear foot, isolated footing loads will be less than 20 kips, and we anticipate 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 report. ESNW should review the final design to verify the geotechnical recommendations provided in this report have been incorporated into the plans. Subsurface Conditions As part of this geotechnical evaluation, an ESNW representative observed, logged, and sampled three hand auger borings on January 31, 2023, advanced at accessible locations within the proposed development area, using hand tools and a half -inch diameter steel T-probe to probe the subgrade of the test holes. The approximate locations of the hand auger borings are depicted on the Hand Auger Boring Location Plan (Plate 2). Please refer to the hand auger boring logs provided as an attachment to this report 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 USDA methods and procedures. Topsoil Topsoil was observed extending to depths of approximately four to six inches below the existing ground surface (bgs). The topsoil was characterized by dark brown color and fine organic material. Native Soil Underlying the topsoil, native soil at the test pit locations was observed to consist of poorly graded sand with and without silt (USCS: SP-SM and SP, respectively). Overall soil relative density generally increased with depth, becoming medium dense to dense at about one to two and one- half feet bgs. Earth Solutions NW. LLC PNT Group, LLC March 28, 2023 Geologic Setting ES-9040 Page 3 The referenced geologic map resource identifies Vashon advance outwash deposits (Qva) across the site and transitional bed deposits (Qtb) downslope of the site to the west, near the toe of the adjacent steep slope area. As reported on the geologic map resource, advance outwash is characterized as mostly clean and well -stratified sand with some pebbles. Transitional bed deposits are glacial and nonglacial deposits that occur beneath the Vashon advance outwash and consist mostly of clay, silt, and fine to very fine sand. The referenced WSS identifies Alderwood-urban land complex as the primary soil unit underlying the subject site with Alderwood-Everett gravelly sandy loam mapped to the southwest of the site. Based on our field observations, native soils on the subject site are generally consistent with Alderwood-Everett series soil. Groundwater Groundwater seepage was not observed at the hand auger boring locations during the fieldwork (January 2023). However, zones of groundwater seepage may be present deeper, particularly near the contact with the deeper transitional bed deposits. Groundwater seepage rates and elevations fluctuate depending on many factors, including precipitation duration and intensity, the time of year, and soil conditions. Geologically Hazardous Areas Assessment As part of this geotechnical evaluation, the referenced chapter of the ECC was reviewed. Based on our investigation and review, the following topics related to development plans and site conditions are addressed: Erosion Hazard Areas — ECC 23.80.020.A. With respect to erosion hazard areas, section 23.80.020 of the ECC defines erosion hazards as "at least those areas identified by the U.S. Department of Agriculture's Natural Resources Conservation Service as having a `moderate to severe', `severe', or `very severe' rill and inter -rill erosion hazard. Erosion hazard areas are also those areas impacted by shoreland and/or stream bank erosion. Within the city of Edmonds, erosion hazard areas include: 1. Those areas of the city of Edmonds containing soils that may experience severe to very severe erosion hazard. This group of soils includes, but is not limited to, the following when they occur on slopes of 15 percent or greater: a. Alderwood soils (15 to 25 percent slopes); b. Alderwood/Everett series (25 to 70 percent slopes), and; c. Everett series (15 to 25 percent slopes). Earth Solutions NW. LLC PNT Group, LLC March 28, 2023 ES-9040 Page 4 2. Coastal and stream erosion areas which are subject to the impacts from lateral erosion related to moving water such as stream channel migration and shoreline retreat; 3. Any area with slopes of 15 percent or greater and impermeable soils interbedded with granular soils and springs or ground water seepage, and; 4. Areas with significant visible evidence of ground water seepage, and which also include existing landslide deposits regardless of slope." Based on the ECC definition, the site does not contain any erosion hazard areas; the steep slope area approximately 50 to 75 feet west of the subject site would classify as an erosion hazard. Landslide Hazard Areas — ECC 23.80.020.113. With respect to landslide hazard areas, section 23.80.020 of the ECC defines landslide hazard areas as areas potentially subject to landslides based on a combination of geologic, topographic, and hydrologic factors. They include areas susceptible because of any combination of soil, slope gradient, slope aspect, structure, hydrology, or other factors. Within the city of Edmonds, landslide hazard areas specifically include: 1. Areas of ancient or historic failures in Edmonds which include all areas within the earth subsidence and landslide hazard area as identified in the 1979 report of Robert Lowe Associates and amended by the 1985 report of GeoEngineers, Inc., and further discussed in the 2007 report by Landau Associates; 2. Coastal areas mapped as class U (unstable), UOS (unstable old slides) and URS (unstable recent slides) in the Department of Ecology Washington coastal atlas; 3. Areas designated as quaternary slumps, earthflows, mudflows, or landslides on maps published by the United States Geological Survey or Washington State Department of Natural Resources; 4. Any slope of 40 percent or steeper that exceeds a vertical height of 10 feet over a 25-foot horizontal run. Except for rockeries that have been engineered and approved by the engineer as having been built according to the engineered design, all other modified slopes (including slopes where there are breaks in slopes) meeting overall average steepness and height criteria should be considered potential landslide hazard areas; 5. Any slope with all three of the following characteristics: a. Slopes steeper than 15 percent; b. Hillsides intersecting geologic contacts with relatively permeable sediment overlying a relatively impermeable sediment, and; c. Springs or ground water seepage. Earth Solutions NW. LLC PNT Group, LLC March 28, 2023 ES-9040 Page 5 6. Any area potentially unstable as a result of rapid stream incision or stream bank erosion; 7. Any area located on an alluvial fan, presently subject to, or potentially subject to, inundation by debris flow or deposition of stream -transported sediments, and; 8. Any slopes that have been modified by past development activity that still meet the slope criteria. Based on the ECC definition, the site does not contain any landslide hazard areas; the steep slope area approximately 50 to 75 feet west of the subject site appears to classify as landslide hazard area. Temporary Excavations For temporary cuts taller than four feet, we recommend sloping or benching the cuts with a 1 H:1 V gradient. Steeper inclinations can be evaluated by ESNW during construction based on exposed soil conditions. Structural Fill Structural fill is defined as compacted soil placed in foundation, slab -on -grade, roadway, permanent slope, retaining wall, and utility trench backfill areas. Structural fill placed and compacted during site grading activities should meet the following specifications and guidelines: • Structural fill material • Moisture content • Relative compaction • Loose lift thickness (maximum) Granular soil* At or slightly above optimum** 95 percent (Modified Proctor) 12 inches Existing soil may not be suitable for use as structural fill unless at (or slightly above) the optimum moisture content at the time of placement and compaction. ** Soil shall not be placed dry of optimum and should be evaluated by ESNW during construction. With respect to underground utility installations and backfill, local jurisdictions may dictate the soil type(s) and compaction requirements. Unsuitable material or debris must be removed from structural areas if encountered. Earth Solutions NW. LLC PNT Group, LLC ES-9040 March 28, 2023 Page 6 Foundations The proposed structure can be supported on conventional spread and continuous footings bearing on undisturbed, competent native soil, compacted native soil, or new structural fill. Competent native soils, suitable for support of the foundation, should be encountered beginning at depths of approximately one to two and one-half feet bgs. 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. Compaction of the soil to the levels necessary for use as structural fill may be difficult during wet weather conditions. Organic material exposed at foundation subgrade elevations must be removed and grades restored with structural fill. Provided the structure 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 The passive earth pressure and coefficient of friction values include a safety factor of 1.5. 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. Slab -on -Grade Floors Slab -on -grade floors for the proposed residential structure should be supported on a well - compacted, firm, and unyielding subgrade. Where feasible, native soils exposed at the slab -on - grade subgrade level can likely be compacted in -situ to the specifications described in this section. Unstable or yielding areas of subgrade should be recompacted, or overexcavated and replaced with suitable structural fill, prior to construction of the slab. A capillary break consisting of a minimum of four inches of free -draining crushed rock or gravel should be placed below the slab. The free -draining material should have a fines content of 5 percent or less (where the fines content is defined as the percent passing the Number 200 sieve, based on the minus three -quarter -inch fraction). In areas where slab moisture is undesirable, installation of a vapor barrier below the slab should be considered. If a vapor barrier is utilized, it should be a material specifically designed for use as a vapor barrier and should be installed in accordance with manufacturer specifications. Earth Solutions NW. LLC PNT Group, LLC March 28, 2023 Retaining Walls ES-9040 Page 7 Retaining walls must be designed to resist earth pressures and applicable surcharge loads. The following parameters may be used for design: • Active earth pressure (unrestrained condition) • At -rest earth pressure (restrained condition) • Traffic surcharge (passenger vehicles) • Passive earth pressure • Coefficient of friction • Seismic surcharge Where applicable. ** Where H equals the retained height (in feet). 35 pcf (equivalent fluid) 55 pcf 70 psf (rectangular distribution)* 300 pcf (equivalent fluid) M1 8H psf** A factor -of -safety of 1.5 has been applied to the passive earth pressure and coefficient of friction values provided in this section. The above design parameters are based on a level backfill condition and level grade at the wall toe. Revised design values will be necessary if sloping grades are to be used above or below retaining walls. Additional surcharge loading from adjacent foundations, sloped backfill, or other relevant loads should be included in the retaining wall design. Retaining walls should be backfilled with free -draining material that extends along the height of the wall and a distance of at least 18 inches behind the wall. In lieu of 18 inches of a free draining material, a drainage mat can be considered. ESNW should evaluate the suitability of drainage mat application during construction. The upper 12 inches of the wall backfill may consist of a less permeable soil, if desired. A perforated drainpipe should be placed along the base of the wall and connected to an approved discharge location. A typical retaining wall drainage detail is provided on Plate 3. If drainage is not provided, hydrostatic pressures should be included in the wall design. Seismic Design The 2018 International Building Code (2018 IBC) recognizes the most recent edition of the Minimum Design Loads for Buildings and Other Structures manual (ASCE 7-16) for seismic design, specifically with respect to earthquake loads. Based on the soil conditions encountered at the test locations, the Site Class D is recommended for seismic design per the 2018 IBC. Earth Solutions NW. LLC PNT Group, LLC March 28, 2023 Liquefaction ES-9040 Page 8 Liquefaction is a phenomenon where saturated and loose cohesionless soil suddenly loses internal strength and behaves as a fluid. This behavior is in response to increased pore water pressures resulting from an earthquake or another intense ground shaking. In our opinion, site susceptibility to liquefaction may be considered low. The depth of the regional groundwater table and the relative density of the native soil were the primary bases for this opinion. Drainage Zones of perched groundwater seepage should be anticipated in site excavations depending on the time of year grading operations take place. Temporary measures to control surface water runoff and groundwater during construction would likely involve passive elements such as interceptor trenches and sumps. ESNW should be consulted during preliminary grading to identify areas of seepage and to provide recommendations to reduce the potential for instability related to seepage effects. Finish grades should be designed to direct surface water away from structures and slopes. Grades adjacent to structures and slopes should be sloped away at a gradient of at least 2 percent for a horizontal distance of up to 10 feet or the maximum allowed by adjacent structures. In our opinion, foundation drains should be installed along building perimeter footings. A typical footing drain detail is provided on Plate 4. Infiltration and LID Evaluation As indicated in the Subsurface Conditions section, native soils encountered during our fieldwork were characterized primarily as sand. While native sand soil may exhibit a moderate to good infiltration capacity, we do not recommend infiltrating site runoff due to the proximity to the steep slope area to the west of the site. Based on topography and geologic mapping, attempted infiltration would move laterally along the deeper fine-grained and pose a risk to stability of the nearby steep slope area. 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. The table below summarizes our evaluation of low impact development methods, 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. Earth Solutions NW. LLC PNT Group, LLC March 28, 2023 ES-9040 Page 9 BMP Viable? Limitations or Infeasibility Criteria Lawns and Landscaped Areas T5.13: Post -construction soil quality Yes None. and depth (Volume V, Chapter 5) Roofs T5.30: Full dispersion (Volume V, Maybe* Limitation: Adequate vegetative flow paths may not be Chapter 5) available. T5.10A: Downspout full infiltration NO Infeasibility: Not recommended due to adjacent steep slope systems (Volume III, Chapter 3) area and risk of causing instability. Roofs Bioretention (Volume V, Chapter 7) No Infeasibility: Not recommended due to adjacent steep slope area and risk of causing instability. T5.10B: Downspout dispersion Maybe* Limitation: Adequate vegetative flow paths may not be systems (Volume III, Chapter 3) available. T5.10C: Perforated stub -out NO Infeasibility: Not recommended due to adjacent steep slope connections (Volume III, Chapter 3) area and risk of causing instability. T5.30: Full dispersion (Volume V, Maybe* Limitation: Adequate vegetative flow paths may not be Chapter 5) available. T5.15: Permeable pavement NO Infeasibility: Not recommended due to adjacent steep slope (Volume V, Chapter 5) area and risk of causing instability. Bioretention (Volume V, Chapter 7) No Infeasibility: Not recommended due to adjacent steep slope area and risk of causing instability. T5.12: Sheet flow dispersion Limitation: Adequate vegetative flow paths may not be T5.11: Concentrated flow dispersion Maybe* available. (Volume V, Chapter 5) * Viability to be determined by storm designer. Limitations This geotechnical evaluation report has been prepared for the exclusive use of Mr. Peter Tang and his representatives. The recommendations and conclusions provided in this report 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 sites may exist and may not become evident until construction. ESNW should reevaluate the conclusions in this report if variations are encountered. Earth Solutions NW. LLC PNT Group, LLC March 28, 2023 Additional Services ES-9040 Page 10 ESNW should be retained to provide additional geotechnical services in association with this project, including testing and consulting services during construction. ESNW should have an opportunity to review final project plans with respect to geotechnical recommendations provided in this letter. We trust this letter meets your current needs. Should you have questions, or if any additional information is required, please call. Sincerely, EARTH SOLUTIONS NW, LLC 03/28/2023 Henry T. Wright, P.E. Associate Principal Engineer Attachments: Plate 1 — Vicinity Map Plate 2 — Hand Auger Boring Location Plan Plate 3 — Retaining Wall Drainage Detail Plate 4 — Footing Drain Detail Hand Auger Boring Logs Grain Size Distribution cc: RAM Engineering, Inc. Attention: Mr. Rob Long, P.E. (Email only) Earth Solutions NW. LLC 192nd Street Southwes rvo rysr °� i i"'inle C' > seam Lane F,t .t Po9er[ane ,y ,off Puget Drme __ Qugei Dri(,P 19.6th S[r ACC s Melody Lane Moplewood�� to Hill ParkD lbz Hinmey Lane CViewland way 0 �lIl. .._... _... _... _... _... _...—._.� .'_ - Cas ersStreet_ �d D yVista Place Lt B(aCRett's - - - P°_� Along street Z a 202nd Street So V Landing__---- ` Carol waY5J a' y o w C n < Glen Street SITE ZGlen Street Glen Street O > Fa�o7 Daley Street oDaley street , < Daley Street ass \Edmonds // rePr C Sprague Street Sprague Street z e` d -_- Edmonds, WA 524 Edmonds Street Fier irralc� Bell Street VMin[et � ek ,- Edmonds ace Main.SteeMain Street - Edmonds _ --Ma,;�, Dayton Street Dayton Street a .w Maple Way ... x �2� N < Maple Street I MIaple Street & Yost Park o Alder street T l S3 Ct- Wain 't Street dn DndstreEt - --_--=_-_Ed_ dHolly Drive I y oaa Mm--Oo_rngyCedar Street -p ^A CJ 7M--- Howell Way D Spruce Street _ - «N spruce street B owdo n --_- Edmonds ' Hemlock Wayo waY s pinesreet _ City Pork w < [southwest Edmonds > Laurel Street 21 Sm S" t pine Street\\ `n pine�5free[ _m Pine Street 216th Street Southwest 216[1 Street Southwes[ 2171h Street southwest Fir StreetQT o u R w Bella Coola Road Elm Street (F Elm Street m Southwest_ Woo `_ -- a d\ — — - -220t11_Street _ dWay = C. - - No,, WA 104 pae °i %We •T r1 oa(an oaa Kulshan Roan \\ N ^ P 3 224[h Street Southwest Yp,,.nquipg \ - tSth sre r Reference: NORTH Earth 1 Solutions C Snohomish County, Washington Observation/Testing00! Open StreetMap.org 40 Vicinity Map Tang Residence Edmonds, Washington Drawn MRS Date 02/23/2023 Proj. No. 9040 NOTE: This plate may contain areas of color. ESNW cannot be responsible for any subsequent misinterpretation of the information Checked KTK Date Feb. 2023 Plate 1 resulting from black & white reproductions of this plate. DALEY STREET 174 r----- — cc , HA 1--��176 --�-- 17a1— • — — • IHAl2 I I I •HA-3 00 -' ---�-- --- I- 176 E SPRAGUE LEGEND HA-1I Approximate Location of • — ESNW Hand Auger Boring, Proj. No. ES-9040, Jan. 2023 Subject Site Existing Building 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. NORTH 0 50 100 200 1 "=100' � � Scale in Feet Hand Auger Boring Location Plan Tang Residence Edmonds, Washington NOTE: This plate may contain areas of color. ESNW cannot be Drawn MRS Date 02/23/2023 Pro' No. 9040 responsible for any subsequent misinterpretation of the information 1 resulting from black & white reproductions of this plate. Checked KTK Date Feb. 2023 Plate 2 18" Min. 0 o o 0 o o o o- a o � o � o o° o 0 o 00 o oo , o oo4)oo o o °o�0 0 0 0 °o 0 00 0 0 o0 0 %. o o � o 0 00.0 00 60 pO 0 0 o O 00 0o. o000 O �o 0 00 000 0000 0o -0 o 0 0 o o 0 00 00°0o 0o o 0 0 0 o o �' o 00 0 00° 0 000000000000 0 0 0 00 � o 0 ao o � oa o 0 og o o.000 oo oo o o g O O 0 o O O O '0 O o O 'o O o 0000 0 o o 0 o 0 0 0 0 ,o o .Oo o o00 O o o o O 0o 0 Oo 0 0 0 -, o0o O e o 0 0000 o Oo 0 o .0 o �� NOTES: • Free -draining Backfill should consist of soil having less than 5 percent fines. Percent passing No. 4 sieve should be 25 to 75 percent. • Sheet Drain may be feasible in lieu of Free -draining Backfill, per ESNW recommendations. • Drain Pipe should consist of perforated, rigid PVC Pipe surrounded with 1-inch Drain Rock. LEGEND: ffiFree -draining Structural Backfill o 1-inch Drain Rock Structural Fill Perforated Rigid Drain Pipe (Surround in Drain Rock) SCHEMATIC ONLY - NOT TO SCALE NOT A CONSTRUCTION DRAWING Retaining Wall Drainage Detail Tang Residence Edmonds, Washington Drawn MRS Date 02/23/2023 Proj. No. 9040 Checked KTK Date Feb.2023 Plate 3 Perforated Rigid Drain Pipe (Surround in Drain Rock) NOTES: • Do NOT tie roof downspouts to Footing Drain. • Surface Seal to consist of 12" of less permeable, suitable soil. Slope away from building. LEGEND: Surface Seal: native soil or other low -permeability material B.* - _- - - _... " - " 1-inch Drain Rock SCHEMATIC ONLY - NOT TO SCALE NOT A CONSTRUCTION DRAWING Earth Solutions NW uc Footing Drain Detail Tang Residence Edmonds, Washington Drawn MRS Date 02/23/2023 Proj. No. 9040 Checked KTK Date Feb.2023 Plate 4 W I ,1� �� Well -graded gravel with Moisture Content Symbols m CU > GW or without sand, little to 0 c no fines Dry - Absence of moisture, dusty, dry to Cement grout U U j L 11 the touch ATD = At time surface seal 0 O o o of drilling g Bentonite o p o01 00(lo Poorly graded gravel with Damp Perceptible moisture, likely below chips o Z v UU o 0 0 0 GP or without sand, little to optimum MC Static water i LO C o Q�oQ no fines level (date) eall Co ° Moist - Damp but no visible water, likely o a) H a) at/near optimum MC - Filter pack with 65 0 a) tav, 0 0 uD op o GM Silty gravel with or without Wet - Water visible but not free draining, blank casing section o 0 2 � O Q 0 sand likely above optimum MC Screened casing o or Hydrotip with U) ° 0 .0 o Saturated/Water Bearing - Visible free filter pack o U) 0 � Clayey gravel with or water, typically below groundwater table End cap O -0-0 � ° L L LL C7 ^ GC without sand Terms Describing Relative Density and Consistency _ 0 co Z Coarse -Grained Soils: Test Symbols & Units Well -graded sand with u� O SW or without gravel, little to = Density SPT blows/foot Fines Fines Content ( ) oo N o c IL o°o°o°o°o°o °°°°°°°°°°° no fines Very Loose < 4 O LO U ._ U (n o MC =Moisture Content (%) Loose 4 to 9 ':: ca � 0 to , •:: •..:•.;: , . Poorly graded sand with DD = Dr Density cf Medium Dense 10 to 29 Y Y (P ) a)o v Sp or without gravel, little to o Z no fines Dense 30 to 49 Str = Shear Strength (tsf) 0 a)Very Dense _> 50 O U) PID = Photoionization Detector (ppm) co a� '.:' . SM Silty sand with or without o Lo c c :;: .::'•:. ;.. gravel Fine -Grained Soils: OC = Organic Content (%) e . •;. Consistency SPT blows/foot CEC = Cation Exchange Capacity (meq/100 g) : Very Soft < 2 � � SC Clayey sand with or LL = Liquid Limit (%) Soft 2 to 3 ^ without gravel Medium Stiff 4 to 7 PL = Plastic Limit (%) (%) Stiff 8 to 14 PI = Plasticity IndexLO CD Silt with or without sand IVIL or gravel; sandy or Very Stiff 15 to 29 gravelly silt Hard _> 30 0 0 0 U 0 F/// Clay of low to medium Y Component Definitions > a)—.1 plasticity; plasticity; lean clay with cn M t. or without sand or gravel; Descriptive Term Size Range and Sieve Number 00 cn E sandy or gravelly lean clay Boulders Larger than 12" — — _ � rn . — J U .5 Cobbles 3" to 12" �o _ OL Organic clay or silt of Zo — low plasticity Gravel 3" to No. 4 (4.75 mm) -0 to J �_ — Coarse Gravel 3" to 3/4" Fine Gravel 3/4" to No. 4 (4.75 mm) Elastic silt with or without d Sand No. 4 (4.75 mm) to No. 200 (0.075 mm) 0 0 o MH sand or gravel; sandy or Coarse Sand No. 4 (4.75 mm) to No. 10 (2.00 mm) c O (n g gravelly elastic silt Medium Sand No. 10 (2.00 mm) to No. 40 (0.425 mm) IL 2 >, - Fine Sand No. 40 (0.425 mm) to No. 200 (0.075 mm) 0 °o U O Clay of high plasticity; Silt and Clay Smaller than No. 200 (0.075 mm) o -0 LO CH fat clay with or without Modifier Definitions o E sand or gravel; sandy or J gravelly fat clay —_ Percentage by fn Weight (Approx.) Modifier CY OH Organic clay or silt of medium to high plasticity < 5 Trace (sand, silt, clay, gravel) 5 to 14 Slightly (sandy, silty, clayey, gravelly) o> ca o PT Peat, muck, and other 15 to 29 Sandy, silty, clayey, gravelly = �U) — = highly organic soils Q _> 30 Very (sandy, silty, clayey, gravelly) Classifications of soils in this geotechnical report and as shown on the exploration logs are based on visual — field and/or laboratory observations, which include density/consistency, moisture condition, grain size, and ii FILL Made Ground plasticity estimates, and should not be construed to imply field or laboratory testing unless presented herein. Visual -manual and/or laboratory classification methods of ASTM D2487 and D2488 were used as an identification guide for the Unified Soil Classification System. Earth Solutions NW L�c Earth Solutions NWLLC Geotechnical Engineering, Construction Observation/Testing and Environmental Services EXPLORATION LOG KEY r Earth Solutions NW, LLC 15365 N.E. 90th Street, Suite 100 Redmond, Washington 98052 Telephone: 425-449-4704 Fax: 425-449-4711 BORING NUMBER HA-1 PAGE 1 OF 1 PROJECT NUMBER ES-9040 PROJECT NAME Tang Residence DATE STARTED 1/31/23 COMPLETED 1/31/23 GROUND ELEVATION DRILLING CONTRACTOR ESNW Rep LATITUDE 47.81363 LONGITUDE-122.36824 LOGGED BY KTK CHECKED BY HTW GROUND WATER LEVEL: NOTES S7 AT TIME OF DRILLING SURFACE CONDITIONS Grass AFTER DRILLING _ wJ p 0.0 w ~Lu CO d7 Q Z TESTS _ 0_ O fy 0 MATERIAL DESCRIPTION TPSL .`=: `. 0.3 Dark brown TOPSOIL - Dark brown poorly graded SAND with silt, medium dense, moist to wet -becomes brown SP_ -probed 8" MC = 11.5 _ Fines = 8.9 SM [USDA Classification: gravelly SAND] 2.5 -becomes tan, medium dense to dense, moist -probed 4" MC = 7.1 3.5 Hand auger boring terminated at 3.5 feet below existing grade. No groundwater encountered during excavation. No caving observed. LIMITATIONS: Ground elevation (if listed) is approximate; the test location was not surveyed. Coordinates are approximate and based on the WGS84 datum. Do not rely on this test log as a standalone document. Refer to the text of the geotechnical report for a complete understanding of subsurface conditions. r Earth Solutions NW, LLC 15365 N.E. 90th Street, Suite 100 Redmond, Washington 98052 Telephone: 425-449-4704 Fax: 425-449-4711 BORING NUMBER HA-2 PAGE 1 OF 1 PROJECT NUMBER ES-9040 PROJECT NAME Tang Residence DATE STARTED 1/31/23 COMPLETED 1/31/23 GROUND ELEVATION DRILLING CONTRACTOR ESNW Rep LATITUDE 47.8136 LONGITUDE-122.36802 LOGGED BY KTK CHECKED BY HTW GROUND WATER LEVEL: NOTES S7 AT TIME OF DRILLING SURFACE CONDITIONS Grass AFTER DRILLING w _ w ~Lu Uj CO TESTS _ O J Q Q z 0 0.5 SM MC = 7.2 SP 2.5 SM MC = 7.0 3.5 MATERIAL DESCRIPTION Dark brown TOPSOIL (Fill) Dark brown poorly graded SAND with silt, loose, moist Brown poorly graded SAND with silt, medium dense, moist -probed 8" Test pit terminated at 3.5 feet below existing grade. No groundwater encountered during excavation. No caving observed. LIMITATIONS: Ground elevation (if listed) is approximate; the test location was not surveyed. Coordinates are approximate and based on the WGS84 datum. Do not rely on this test log as a standalone document. Refer to the text of the geotechnical report for a complete understanding of subsurface conditions. r Earth Solutions NW, LLC 15365 N.E. 90th Street, Suite 100 Redmond, Washington 98052 Telephone: 425-449-4704 Fax: 425-449-4711 BORING NUMBER HA-3 PAGE 1 OF 1 PROJECT NUMBER ES-9040 PROJECT NAME Tang Residence DATE STARTED 1/31/23 COMPLETED 1/31/23 GROUND ELEVATION DRILLING CONTRACTOR ESNW Rep LATITUDE 47.81344 LONGITUDE-122.36808 LOGGED BY KTK CHECKED BY HTW GROUND WATER LEVEL: NOTES S7 AT TIME OF DRILLING SURFACE CONDITIONS Grass AFTER DRILLING _ wJ p 0.0 w ~Lu CO d7 Q Z TESTS _ Q O fy 0 MATERIAL DESCRIPTION TPSL .'—. Dark brown TOPSOIL 0.5 Brown poorly graded SAND with silt, loose, moist SP- _ SM -probed 4" 2.5 MC = 6.3 2 5 Tan poorly graded SAND, medium dense to dense, moist SP [USDA Classification: gravelly SAND] MC = 5.9 3.5 Fines = 1.9 Hand auger boring terminated at 3.5 feet below existing grade. No groundwater encountered during excavation. No caving observed. LIMITATIONS: Ground elevation (if listed) is approximate; the test location was not surveyed. Coordinates are approximate and based on the WGS84 datum. Do not rely on this test log as a standalone document. Refer to the text of the geotechnical report for a complete understanding of subsurface conditions. Earth Solutions NW, LLC GRAIN SIZE DISTRIBUTION 15365 N.E. 90th Street, Suite 100 WWI Redmond, Washington 98052 Telephone: 425-449-4704 Fax: 425-449-4711 PROJECT NUMBER ES-9040 PROJECT NAME Tang Residence U.S. SIEVE OPENING IN INCHES U.S. SIEVE NUMBERS I HYDROMETER 6 4 3 2 1 1 /23/8 3 4 6 810 1416 20 30 40 50 60 100140 200 100 95 90 85 80 75 70 65 H cD 60 w � 55 m w 50 z LL 45 z w 40 w a 35 30 25 20 15 10 5 0 100 10 1 0.1 0.01 0.001 GRAIN SIZE IN MILLIMETERS COBBLES GRAVEL SAND SILT OR CLAY coarse fine coarse medium fine E. CONSTRUCTION SWPPP REQUIREMENTS: The project will require grading to construct the proposed building and utilities (including the stormwater control facilities). 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, 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. Stockpiles 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. 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: During construction silt fencing will provide attenuation of site runoff and upon project completion and stabilization (established lawns and landscape of exposed soils). 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. 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. RAMEngineering, Inc. RAM No. 23-002 840 Daley Street SFR Stormwater Site Plan Report Page E-1 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 trenches 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: No LID stormwater BMPs are proposed. Conclusion: The total site disturbance area (0.19 ac.) 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. 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. RAM No. 23-002 840 Daley Street SFR Stormwater Site Plan Report Page E-2 F. 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 owner is 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. 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. The onsite detention tank system, control structure, junction catch basins, and onsite conveyance pipes are to be privately maintained by the project residence. Maintenance shall include the removal of sediment from the detention tank system, using a vactor truck or equally effective method. Regular inspections of the control structure within the catch basin shall be conducted to detect if non -routine maintenance is required due to sediment or debris blocking or clogging the fixed orifice or standpipe inlet. Regular sediment removal from the catch basins with a vactor truck or equally effective method shall be conducted as determined by regular inspections. Regular inspection and maintenance of the storm filter should occur according to the attached maintenance tables from the Washington State Department of Ecology Stormwater Manual (2019- Volume V). Semi-annual inspections shall be conducted to ensure proper operations of the drainage system. The inspections should occur prior to the winter rain season (Oct/Nov), leaving sufficient time to correct any detected maintenance problems, and at the end of the season (April/May) to determine the effect of the season's runoff. Once a historical basis is developed the frequency of inspection may be modified as necessary. Sediment can build up inside control structures and catch basins, blocking or restricting flow to the inlet. To prevent this problem, these structures should be routinely cleaned. Regular inspections of control structures should be conducted to detect the need for non -routine cleanout. 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. RAMEngineering, Inc. RAM No. 23-002 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. 840 Daley Street SFR Stormwater Site Plan Report Page F-1 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.3: Maintenance Standards - Closed Detention Systems (Tanks/Vaults) Maintenance Results Expected Component Defect Conditions When Maintenance is Needed When Maintenance is Performed Plugged Air Vents One-half of the cross section of a vent is blocked at Vents open and any point or the vent is damaged. functioning. Accumulated sediment depth exceeds 10% of the diameter of the storage area for 1/2 length of storage vault or any point depth exceeds 15% of All sediment and debris Debris and Sediment diameter. removed from storage (Example: 72-inch storage tank would require area. cleaning when sediment reaches depth of 7 inches for more than 1/2 length of tank.) Storage Area Any openings or voids allowing material to be Joints Between transported into facility. All joint between Tank/Pipe Section (Will require engineering analysis to determine tank/pipe sections are sealed. structural stability). Tank Pipe Bent Out of Any part of tank/pipe is bent out of shape more than Tank/pipe repaired or Shape 10% of its design shape. (Review required by replaced to design. engineer to determine structural stability). Cracks wider than 1/2-inch and any evidence of soil Vault replaced or particles entering the structure through the cracks, repaired to design Vault Structure Includes or maintenance/inspection personnel determines specifications and is Cracks in Wall, Bottom, that the vault is not structurally sound. structurally sound. Damage to Frame and/or Top Slab Cracks wider than 1/2-inch at the joint of any No cracks more than inlet/outlet pipe or any evidence of soil particles 1/4-inch wide at the joint entering the vault through the walls. of the inlet/outlet pipe. RAMEngineering, Inc. RAM No. 23-002 840 Daley Street SFR Stormwater Site Plan Report Page F-2 Table V-A.3: Maintenance Standards - Closed Detention Systems (Tanks/Vaults) Maintenance Results Expected Component Defect Conditions When Maintenance is Needed When Maintenance is Performed Cover Not in Place Cover is missing or only partially in place. Any open Manhole is closed. manhole requires maintenance. Mechanism cannot be opened by one maintenance Locking Mechanism Not person with proper tools. Bolts into frame have less Mechanism opens with Manhole Working than 1/2 inch of thread (may not apply to self-locking proper tools. lids). Cover Difficult to One maintenance person cannot remove lid after Cover can be removed Remove applying normal lifting pressure. Intent is to keep and reinstalled by one cover from sealing off access to maintenance. maintenance person. Ladder is unsafe due to missing rungs, Ladder meets design Ladder Rungs Unsafe misalignment, not securely attached to structure standards. Allows maintenance person wall, rust, or cracks. safe access. See Table V-A.5: See Table V-A.5: Maintenance Standards -Catch See Table V-A.5: Catch Basins Maintenance Standards Basins Maintenance Standards Catch Basins Catch Basins Table V-A.4: Maintenance Standards - Control Structure/Flow Restrictor Maintenance Defect Condition When Maintenance Results Expected When Component is Needed Maintenance is Performed Trash and Debris (Includes Material exceeds 25% of sump Control structure orifice is not Sediment) depth or 1 foot below orifice blocked. All trash and debris plate. removed. Structure is not securely attached to manhole wall. Structure securely attached to wall and outlet pipe. General Structure is not in upright position (allow up to 10% from Structure in correct position. plumb). Structural Damage Connections to outlet pipe are Connections to outlet pipe are watertight; structure repaired or not watertight and show signs of replaced and works as designed. rust. Structure has no holes other than Any holes - other than designed designed holes. holes - in the structure. Cleanout gate is not watertight Gate is watertight and works as or is missing. designed. Gate cannot be moved up and Gate moves up and down easily down by one maintenance and is watertight. Cleanout Gate Damaged or Missing person. Chain/rod leading to gate is Chain is in place and works as missing or damaged. designed. Gate is rusted over 50% of its Gate is repaired or replaced to surface area. meet design standards. Control device is not working Plate is in place and works as Orifice Plate Damaged or Missing properly due to missing, out of designed. place, or bent orifice plate. Obstructions Any trash, debris, sediment, or Plate is free of all obstructions and vegetation blocking the plate. works as designed. RAMEngineering, Inc. RAM No. 23-002 840 Daley Street SFR Stormwater Site Plan Report Page F-3 Table V-A.4: Maintenance Standards - Control Structure/Flow Restrictor Maintenance Defect Condition When Maintenance Results Expected When Component is Needed Maintenance is Performed Any trash or debris blocking (or Pipe is free of all obstructions and Overflow Pipe Obstructions having the potential of blocking) the overflow pipe. works as designed. See Table V-A.3: Maintenance See Table V-A.3: Maintenance See Table V-A.3: Maintenance Manhole Standards - Closed Detention Standards - Closed Detention Standards - Closed Detention Systems (Tanks/Vaults) Systems (Tanks/Vaults) Systems (Tanks/Vaults) Catch Basin See Table V-A.5: Maintenance See Table V-A.5: Maintenance See Table V-A.5: Maintenance Standards - Catch Basins Standards - Catch Basins Standards - Catch Basins Table V-A.S: Maintenance Standards - Catch Basins Maintenance Results Expected When Component Defect Conditions When Maintenance is Needed Maintenance is performed Trash or debris which is located immediately in front of the catch basin opening or is blocking inletting capacity of the basin by more than 10%. No Trash or debris located immediately in Trash or debris (in the basin) that exceeds 60 percent of front of catch basin or on the sump depth as measured from the bottom of basin grate opening. to invert of the lowest pipe into or out of the basin, but in no case less than a minimum of six inches clearance No trash or debris in the Trash & Debris from the debris surface to the invert of the lowest pipe. catch basin. Trash or debris in any inlet or outlet pipe blocking more Inlet and outlet pipes free than 1/3 of its height. of trash or debris. Dead animals or vegetation that could generate odors No dead animals or that could cause complaints or dangerous gases (e.g., vegetation present within methane). the catch basin. General 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 No sediment in the catch Sediment case less than a minimum of 6 inches clearance from basin the sediment surface to the invert of the lowest pipe. Top slab has holes larger than 2 square inches or Top slab is free of holes cracks wider than 1/4 inch. (Intent is to make sure no and cracks. Structure Damage material is running into basin). to Frame and/or Top Slab Frame not sitting flush on top slab, i.e., separation of Frame is sitting flush on more than 3/4 inch of the frame from the top slab. Frame the riser rings or top slab and firmly attached. not securely attached Maintenance person judges that structure is unsound. Basin replaced or Fractures or Grout fillet has separated or cracked wider than 1/2 inch repaired to design standards. Cracks in Basin and longer than 1 foot at the joint of any inlet/outlet pipe Walls/ Bottom or any evidence of soil particles entering catch basin Pipe is regrouted and through cracks. secure at basin wall. RAMEngineering, Inc. RAM No. 23-002 840 Daley Street SFR Stormwater Site Plan Report Page F-4 Table V-A.S: Maintenance Standards - Catch Basins Maintenance Results Expected When Component Defect Conditions When Maintenance is Needed Maintenance is performed Settlement/ If failure of basin has created a safety, function, or Basin replaced or repaired to design Misalignment design problem. standards. Vegetation growing across and blocking more than 10% No vegetation blocking of the basin opening. opening to basin. Vegetation Vegetation growing in inlet/outlet pipe joints that is more No vegetation or root than six inches tall and less than six inches apart. growth present. Contamination and See Table V-A.1: Maintenance Standards -Detention No pollution present. Ponds Pollution Cover Not in Place Cover is missing or only partially in place. Any open Cover/grate is in place, meets design standards, catch basin requires maintenance. and is secured Locking Mechanism cannot be opened by one maintenance Mechanism opens with Catch Basin Mechanism Not person with proper tools. Bolts into frame have less than proper tools. Cover Working 1/2 inch of thread. One maintenance person cannot remove lid after Cover Difficult to applying normal lifting pressure. Cover can be removed by Remove (Intent is keep cover from sealing off access to one maintenance person. maintenance.) Ladder Rungs Ladder is unsafe due to missing rungs, not securely Ladder meets design standards and allows Ladder Unsafe attached to basin wall, misalignment, rust, cracks, or maintenance person safe sharp edges. 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 20% of Grate free of trash and Metal Grates (If grate surface inletting capacity. debris. Applicable) Grate is in place, meets Damaged or Grate missing or broken member(s) of the grate. the design standards, and Missing. is installed and aligned with the flow path. Washington State Department of Ecology 2019 Stormwater Management Manual for Western Washington (2019 SWMMWW) Publication No.19-10-021 RAMEngineering, Inc. RAM No. 23-002 840 Daley Street SFR Stormwater Site Plan Report Page F-5 ENGINEERING, INC. Civil Engineering /Land Planning