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15515 72ND.pdfDETERMINATION OF NONSIGNIFICANCE Description of proposal Construction of single family residence in an environmentally sensitive area Proponent Rick Kent Location of proposal, including street address, if any. 15515 - 72nd Ave. West. Edmonds. Lead agency Edmonds Planning Department The -lead agency for this proposal has determined that it does not have a prob- able significant adverse impact on the environment. An environmental impact statement (EIS) is not required under RCW 43.21C.030(2)(c). This decision was made after review of a completed environmental checklist and other information on file with the lead agency. This information is available to the public on request. There is no comment period for this DNS. E7 This DNS is issued under 197-11-340(2); the lead agency will not act on this proposal for 15 days from the date below. Comments must be submitted by Resp.msible official Duane Bowman y Tanner Assistant City P ; Position/title Phone 771-3202, ext. 254' Address 250 Fifth Avenue North, Edmonds, W 98020 October 25 1985 Date 9 Signature You may appeal this determination of nonsignificance{ to James Driscoll, Hearing Examiner at 250 Fifth Avenue N., Edmonds, WA 98020�` no later than November 8, 1985 i by filing a written appeal EE 4 You should be prepared to make specific factual objections. Contact > Duane Bowman to read or ask about the procedures for SEPA appeals There is no agency appeal. =t f I r el CITY OF EDMONDS PROJECT NAME ENVIRONMENTAL ASSESSMENT DATE SUBMITTED /_ r The information on this form will be used to determine the effect of your action upon the environment of the City of Edmonds. Please answer each question as thoroughly as possible. 1. LAND • sift. Area S ,�,; ,.; ?� -16 Soils Type f' ,:> loo��- ,�r 7icc Limitations Description of topography (a sloe)nn 1' o% Adel- c ao- -°,s �. `long NOTE: If grading or filling will Grading: Estimated cubic yards 300 CL, exceed 500 cubic yards a grading and filling plan must be sub - Filling: Estimated cubic yards _ mitted with the application. Estimated area to be paved (including buildings)_��y� Estimated area in open space (pervious surface) Appunv 19 8o© 2. WATER Streax, - Estimated flow (cubic feet per second) Will stream be altered? If yes, to what degree? Other water bodies? VoQ Impact on storm drainageO,,,L„ 10 TnP,' ni'b,RUMethod of handling runoff&Furs 7W1y1,,�,cr, nr Adjacent to shorelines zone? A10 Within 200 feet of MHH14? �f/p 3. VEGETATIO'; Type and approximate number of trees / Doud FIR Minimum diameter of trees to remain y " % of trees to be removed Ground coveryor✓E % to be removed O Proposed landscaping, if any S-1,4aro( /� sior,yr+�, ° }�RrnAnrN.i.�rcy (qav/✓ 1��er�% %-6,j5 C,ho So, ,// tPe,S )Z Mr/ eari^re i fir �v %Zatl1 4. EXISTING LAND USE WITHIN 300 FEET RADIUS OF PROPOSED DEVELOPMENT: Single Multi - Vacant Family Family Commercial Other North South East West 5. CIRCULATION Estimated increase in auto trips daily Availability of public transportation w2 Oars reAO. 6. AREA OF IMPACT Neighborhood,Regional i- r> a'i- �,-.t, +v rca>• , 7. EFFECT ON AIR QUALITY 00A) LE,_ S. CHANGES IN NOISE GENERATION ,UoT SrGu 1F1CA,vT BUtLDING h_y ENVIRONMENTAL CHECKLIST ; Piuliosv of 6140.It4►._ Tlie Stutc f=nvironn'wi. i:il Policy:Act.(SLPA), cliapler 43 'IC f:CV+�,:regttirc stll.govLrnmcntaI agencies to consider the„envirowncnial a proposal before making decisions.. An en :cunmental •impact statement (EIS) must be prcpartsd for all proposals with probable significant adverse impacts oil lhr duality oGthe environment, .The purpose of Chia chcclatst.is to provide information to -help you and the agency identify impacts from yourproposaf:(and to reduce or avoid impacts ('turn thepropasal;-if it can be done) and to help. the agency decide whethdran=E1S is requtretJ Insiri,clions for Applicants: This crivironnacntul checklist asks you to describe some basic information about your, proposal Governmental, agen Gies :use .this checklist' to determine. whether the envirnntnental unptctt of:.y.pur proposal are significant, requtnng' preparation of an EIS Answer the.quations briefly; with the most.`"precise information known or,gi,ve the best de- scription you: can. l'ou mull answer.each question. accurately and carefully, to the bestof your knowledge. In most cases, you. should 3 be able to answer the questions from your own observations or project plans without the need to hire. cxpe.rts. f you I really do not know the answer, or if a question does not apply to your: proposal, write "do not know" or: "does not ep ply Complete answers .In the questions ❑o", may avoid unnecessary delays later. ' Some questions ask about.. governmental regulations, such as zoning, shoreline, and landmark designations Answer these. questions if you can. of you have problems, the governmental agencies'can assist you 'i The checklist ciuestions:apply to all parts of your proposal, even if..yOu plan'to do them oyer a period. of time or on diffdrent parcels ofaand. Attach any tlddiiinnal' inforiiiation hat ++'il1 help describe your proposal or its environmental effects The agency to which you submii this checklist naafi' ask you to t:kplain your answers .or provide additional in- formation reasonably related to determining if there may be significant adverse impact. i . Use of checklist for nonprojeci proposals: Complete this checklist for nonprojecl proposals, even though questions may. be ansviered does not apply." ]n An (. Drrton, comlilett. the SUPPI:EMENTAt. SHEM, roit NONPROIECT ACTIONS (part D) Igor nonproject`aciions, the references in the checlaist to the words "project," epp.icant"Nand property or site should 'be, read as "Proposal," "proposer," and "affected'- geographic area,"res ectivel A HAct GROUNDqa 1. Name of proposed: project, if applicable: Kea rl t nil e . Fq 1 ': name of applicant: %L LKEN j 3: Address and phone number of ,applicant and. contact person: j�'et,-t l p 6 2oot'h PI, SW.. . 5803 6 I A. Date checklist prepared: JOA. p, l j S.:Agcncy requesting checklist: t 'O1lUNvS 1&UILoi4 ANNju6 TJTp'j 6; Proposed timing or schedule (including phasing, if applicable): I CpT�STRucTlotJ To Con mruor j p' o f O cToBE i To %1✓ 60rlP1.7 ri D ur;� o i-jAtzc H /5$6 7. Do you have any plans for future additions, expansion, or further activity related to or conncctt.d etlh this proposal'► if yes, explain. Nap 4 ' BUtLDIN6 r t OCT 23:1985 :, , f , -A L t - 1p TO IIE 176AII'1 ! TfQ Ill APPLICANT. �f iA41 11'AL tfj Ai AT O FOR AGENCl° IfSC,UNLI x `�T[ c N1�hitt general types of soils are found qn the s'itc for exam le,'`cl❑ y, sand i P ) gravel, pe.►! : t� muc} )'? II you Lno„ the clnsstftcafion of 09J Iutrnl sotls,.spccif� "(hem and not any prime, farrnl:ind, vet-y Aeasa S ua'Y (,LA-iai f.)pit-i N, 0 r; �OAGEKEN.T T /4i. $O1c>�c ;3! a d. Arc her surface indications of,history of unsinblc.soils in the, iittli►ediate vicinity? lF so, describe $ , OF %%�.fDOW:�Y1L�s �}R�i. C�'06C2 �Olut d%1$SDatAf%5. iI�SS�siT/f/�U � SEIOE ?OT�"�PAL fA) . SGEROUN1uG, � � � $oc1Np, /v`` 4 f +$R� 5' / GI tC Dwk D P ae T J bAILy faTtr PF.S.T f R77pU -' OF T.Ial,S S)T); PAS /A►D14�}7"�0.7DM�67'Lc17 flr�� ;7Htt7W A>ZQ WR'S OESrgNA7[Za hs .p�iy Sa G�lAUcr iuSY.FS',. :'7ut?!�� NxVCJ /3Fi:AJ wpAA7LrO e: Descrttic the purpose, type, and apprnxlmatc quantities of tiny. fllling..o(gr►ding-pro- S w e Roa,!;p raw posed. lndica.ie'source :of fill: RAZ►I Appl-ox 300 1 A4 f' COuld cruston occur ►s ti result of clearing, construction, or use': If so ge.ri . erdily, d6 cri e. A•ND vpMltilHA-Le :..rvG�Y►rlxxDgJi t,DLoGisr W11.�.,,r pSfRv,ED'. g.: About: whit percent of. the site will -be covered with 'impervious surfaces after, pro�ccl construction (for..eznples atipilait'or buildings)? d J. KEITH CROSS, P.E. Geotechnical Engineering Consultant (206) 822-2725 6020 111th Place N.E., Kirkland, Washington 98033 July 15, 1985 Rick Kent 1706 200th Place SW Lynnwood, WA 98036 Site Subsurface Exploration and Geotechnical Engineering Studies, Northeast Corner of 156th Street SW and 72nd Avenue W, Edmonds, Washington Project No. 9056-001 This letter is prepared to present the results of a site subsurface exploration study conducted for a proposed residence and and geotechnical engineering adjoining residential properties at the above noted location. Our current study follows a preliminary site slope stability evaluation, which was summarized in our letter of May 30, 1985. We understand that a proposed residence will be located on the center lot of the 3 lot parcel and that, at Present, specific design and siting details have not been finalized. We understand that a general design concept involving a single-family dwelling utilizing a daylight basement set at or near existing grade is currently planned. Beyond minor excavation for the basement area, we understand that regrading of the property is not anticipated. Authorization was provided by Rick Kent to conduct a study to evaluate geotechnical development considerations for this site. Our evaluations included slope conditions and relative stability, establishing geotechnical design criteria and related development considerations. The scope of our work included observation of the excavation of backhoe exploration pits, evaluation of subsurface conditions related to the proposed development and the preparation of this report. Site Conditions and Subsurface Explcrations The subsurface conditions at this site were explored by excavating five (5) backhoe exploration pits at the approximate locations shown on the attached site location map, Figure 1. The exploration pits ranged in depth from 4.5 to 9.3 feet below existing grade. Records of soils and subgrade conditions . l Letter to Rick Kent Re: Site Subsurface Exploration and Geotechnical Evaluation Studies, NE Corner of 156th St.,SW and 72nd Ave.,W Edmonds, WA Project No. 9056-001 July 15, 1985 Page 2 encountered in each pit were maintained and are summarized on the attached logs of exploration pits. Locations and elevations of the exploration pits were established using tape, compass and hand level measurements and should be considered accurate to that extent. Site elevations are referenced to our interpolation of the City of Edmonds 1" = 200', 5-foot contour topographic datum. For the purposes of this study, the elevation of the manhole cover located in the roadway (72nd Ave W), west of the southwest corner of the central lot, was assumed to be 292 feet. Our site plan (Figure 1) is based on the property boundary survey information developed by Reid, Middleton & Associates, Inc. The rectangular shaped parcel is bounded on the west by 72nd Avenue West, on the south by 156th Street SW, on the east by residential property and on the north by undeveloped land. The northernmost portion of the parcel lies over the steep, north facing slope which forms the south flank of Lunds Gulch. This major east -west trending slope feature forms the northern terminus of the Meadowdale upland. The property currently supports a growth of moderate sized evergreen and deciduous trees in the south and north (steep slope area) and a dense low brush cover in the central area. Rotted old growth (?) stumps and dead falls occur over much of the property. Our initial site reconnaissance notes indicated the potential. for fill soils along the steep slope margin. Based on our exploratory pit information, evidence of such grade modification is not observed in this area. The property (and most probably the upper elevations of the gross slope feature) is underlain by a sequence of a very dense sandy glacial drift and lodgement till soils. In the area of EP-1, the sandy drift is found to underly and to be interbedded with the very dense glacial till material. In the area of EP-4 and 5, the glacial till is found to underlie the dense sandy drift. In the area of EP-2 and 3, the sandy drift is not observed. In that area (the southeast portion of the north lot), the dense basal till is overlain by about 1.5' of medium dense gravelly sands. These materials are interpreted y C#' ,tti F. Letter to Rick Kent' 'Re: Site Subsurface Exploration and Geotechnical Evaluation Studies, NE Corner of 156th St.,SW and 72nd Ave.,W Edmonds, WA Project No. 9056-001 July 15, 1985 Page 3 as a fluvial (stream laid) material and are most probably related to the as recession of the latest glacial ice mass to cover the area (about 13,000 years before present). The uppermost foot of native soils noted in our study consist of an accumulation of forest duff, root mass and loose to j moderately dense, brown to reddish brown, silty fine sand with a varying I, gravel content and occasional cobbles and boulders. i Aside from the occurrence discussed in our report of May 30, 1985, ground water was not observed in our explorations. Concluding Opinions General: The findings of the geotechnical explorations conducted indicate that the site is generally suitable for residential development. Site development may involve excavation efforts for basement areas. These activities may iinvolve cutting into most of the site soils encountered in our exploratory I pits. We would expect that while a very dense condition may exist for.some of the subgrade soils, conventional excavating equipment should be appropriate in construction activities. Considering the dense in -tact character of the encountered soil types and the general appearance of the major slope feature, we are of the opinion that the likelihood of slope failure is small. The risk assessment criteria developed by City of Edmonds Engineering Department for the slope feature in this area (i.e. 5% over a 25 year period) would seem reasonable, if not somewhat conservative for this property. A 25' ' setback from the steep slope margin would seem appropriate for structures in the northern lot area. Foundation type, design and specific risk allowance could be taken into account in reevaluating the setback distance for future development. Filling within the setback zone should not be attempted. We suggest that a vegetation ground cover (either native or landscaped) be maintained within the parcel, so as to reduce erosion potential. <G i 5 Letter to Rick Kent Re: Site Subsurface Exploration and Geotechnical Evaluation Studies, NE Corner of 156th St.,SW and 72nd Ave.,W Edmonds, WA Project No. 9056-001 July 15, 1985 Page 4 Site Grading: Filling within the setback area should be avoided unless specifically evaluated and monitored by a geotechnical engineer. Grading and excavations on the site should preferentially be performed during the dry season as the soils are moisture sensitive due to their fine grained content. Even small increases in water content could create difficulties in trafficability, workability and compactibility. j Foundations: The following recommendations are directed primarily at the proposed Kent development, which we understand will be sited within the center lot of the subject parcel. However, these recommendations are expected to be generally applicable to the other areas outside the setback from the top of slope. The dense naturally occurring subgrade soils should prove suitable for support of building foundations and floor slabs. An allowable net bearing pressure of 6000 psf would be suitable for shallow spread footing foundations planed in the dense sandy drift or glacial till soils. A bearing pressure value of 2500 psf would be appropriate for shallow footings founded in the moderately dense, undisturbed recessional sands and gravels or ground moraine soils. Observed soil conditions, including soils descriptions and depth to bearing materials are contained in the attached exploratory pit logs and in Table 1, "Exploratory Pit Summary". Foundations should be placed 18 inches below the lowest adjacent grade and should have minimum dimensions as specified by the City of Edmonds or U.B.C. criteria. Settlement of such footings is expected to be less than one inch, but could vary depending upon construction techniques. To reduce potential construction related settlements, the bottom of the footing excavation should be hand cleaned of all loosened or softened soils prior to placing the concrete for the footings. Basement walls should be designed to resist lateral equivalent fluid pressures of 40 pounds per cubic foot (pcf) if backfilled per the guidelines shown on the attached Subdrain and Backfill Scheme.. �..., ..i ..1. a. ., ....... ..r ...,...lfr 1 :C.3„L-1d, �y.cY>,..Li.i ,'✓.��rt:..:.. Letter to Rick Kent Re: Site Subsurface Exploration and Geotechnical Evaluation Studies, NE Corner of 156th St.,SW and 72nd Ave.,W Edmonds, WA Pro,iect No. 9056-001 July 15, 1985 Page 5 The glacial soils on the site appear to be relatively impermeable and could develop a bathtub effect in the basement if subsurface drainage is not provided. Recommendations for peripheral footing drain systems are shown on the attached Subdrain and Backfill Scheme. The use of a drainage sand and gravel blanket placed below the floor slab will assist in dampness control. A minimum of 6 inches of drainage sand and gravel is recommended. Roof drainage should be collected in downspouts and directed away from the house. A collector system for these drains with tight -line discharge into an appropriate disposal area is recommended. If storm water discharge is directed over the slope into Lunds Gulch, an energy dissipating, erosion protection and water disposal system should be used downslope from the discharge point. We suggest a rip -rap blanket extending at least 40 feet down the steep slope from -the discharge point. Materials to be employed in the energy dissipating blanket should consist of a fractured spall (4 to 8 inch) sized quarry rock product. Uncontrolled discharge over the steep slope area should be avoided as accelerated erosion and potential instability of the slope area could result. Limitations: The observations, opinions and recommendations contained in this report are based on the interpretations of the site conditions as they presently exist and the understanding of the proposed development. These interpretations assume that the subsurface conditions encountered in the explorations are representative of the total site conditions. If, during construction, subsurface conditions different from those encountered are observed or appear to be found, an immediate review of these conditions and the recommendations provided should be conducted. This report was prepared for the exclusive use of Rick Kent and his agents for the referenced project. The work performed in this study was limited to the scope of work previously outlined and is believed to be in accordance with generally accepted geotechnical practice. No other warranty, expressed or implied, is made. I �QY��X�Lz!...��ha�?��a.�✓���'�a{i,53_, ar f, �. .. "�"... Asa= �'�.ar'`�.w�ou �. �.:.�'�c,?'�]k��Y.,dc`�%q�t�3�'•.:°3 ._,.,i^Fa�',�e5�,(` Letter to Rick Kent Re: Site Subsurface Exploration and Geotechnical'c5 Evaluation Studies, NE Corner of 156th St.,SW and 72nd Ave.,W Edmonds, WA Project No. 9056-001fas July 15, 1985 Page 6 Should you have any y questions or require further assistance, please call. Yours very truly, Y'EI TH �`so �yOf ^AS� C�O� 0 Keith Cross, P.E. a Walter L. Bicket Geological Services, Inc. �, v:u�iE• ' v Engineering Geology Consultant to t°O°•���'`�� J. Keith Cross, P.E. attachments; t Rick Kent Site {yt`3r Edmonds, WA Project No. 9056-001 July 15, 1985 _ TABLE I r: EXPLORATION PIT DATA SUMMARY Exploratory Topsoil/ Bearing Ground,.Water:: Exploratory Pit Root Mat Fill Soils Seepage Pit No. Elev. (ft) Depth (ft) Depth (ft) D,epth (ft) .Depth .(ft),. 1 291 1.0 - 1.0 none 2. 288 1..0/2.2 - 2.2 none 3 288 1.7/3.0, - 2.5 none 4 302 1.0 - 1.0 none 5 298 1.0 1.0(?)` 1:5 none ps i pkt Rick Kent Site 1 3A, Edmonds, WA, ,a Project No. 9056-001` s: July 15, 1985 EP-1 0.0' - 1.0' 1.0' - 2.0' 2.0' - 9.3' EP-2 0.0' - 1.0' j. 1.0' 2.2' 2.2' - 4.5' EP-3 0.0' - 1.7' 1.7' 3.2' 3.2' - 5.3' EXPLORATORY PIT LOGS x Elevation: 291 Duff, heavy root mass and loose to medium dense, brown, silty fine sand with some gravels, damp, ground moraine soils Very dense, grey, glacial till (fine sand/silt matrix), dampdi t; r. Very dense, grey, gravelly, fine to medium sand, damp, poorly sorted, occasional boulders to 14", includes thin seams of glacial till, advance sands T.D. at 9.3' Elevation: 288 Duff, heavy root mass and loose, brown, silty sandy topsoil, dry to damp Medium dense,'brown, gravelly, medium sand, minor silt, damp, recessional sands and gravels Very dense, grey, glacial till (fine sand/silt matrix), damp T.D. at 4.5' Elevation: 288 Duff, very heavy root mass and loose brown, silty, fine sandy. topsoil, damp, ground moraine soils Medium dense, brown, gravelly, medium to fine sand, damp, trace of silt, cobbles to 6", recessional sands and gravels Very dense, grey, glacial till (fine sand/silt matrix), damp T.D. at 5.3' EP-4 0.0' - 1.0' 1.0' - 2.0' 2.0' - 4.3' 4.3' - 4.6' EP-5 0.0' - 1.0' 1.0' - 2.6' 2.6' - 4.8' 4.8' - 5.5' EXPLORATORY PIT LOGS cont'd. Elevation: 302 Duff, root mass and loose, reddish brown, sandy silty topsoil, damp, gravels and boulders to 24", ground moraine soils Dense, tan to grey brown, gravelly, silty, fine to medium: sand, damp, poorly sorted, weathered till in zones? glacial _. drift Dense, to very dense, grey, gravelly medium sand, damp, minor silt, rounded gravels to 4", advance sands Very dense, grey, glacial till (fine sand/silt matrix), damp T.D. at 4.6' Elevation: 298 Duff, fine root mass and loose, brown sandy silt, damp, trace. of burnt wood and charcoal fragments, possibly modified ground Medium dense, reddish brown, gravelly, silty fine sand, damp, poorly sorted, some cobbles, ground moraine soils Very dense, grey brown, gravelly, silty fine to medium sand, damp, glacial till seams in lower elevations, grades to till Very dense, grey glacial till (fine sand/silt matrix), damp T.D. at 5.5' SLOPE OUTSIDE GRADE AWAY FROM STRUCTURE FOR DRAINAGE PAVEMENT OR 18 INCHES MIN. TAMPED TOPSOIL OR IMPERVIOUS SOIL / S min. ��l GENERAL FILL = s o.• WEEP HOLES SUBDRAIN PIPE not to scale a A TA T n SUBDRAIN _PIPE "—If inimum Dia. Perforated Or Slotted Concrete, Metal, Asbestos -Cement Or Plastic Pipe. Tight Jointed, Sloped To Drain (4"/100' min, slope), With Clean -Outs. Slotted Pipe-- 1/8" Max. Width Slots Perforated Pipe-- 3/16" to 3/8" Holes Slots Or Perforations Preferentially In Lower Half Of Pipe With Lower Quarter Segment Solid For Water Flow. DRAINAGE SAND & GRAVEL -- — — — — — — — — — — -- To Meet Washington State Specifications Or The Following Gradation. EXTERIOR RETAINING WALL DAMP PROOFING VAPOR BARRIER CONCRETE SAND--, 'o: •.e;.��� lei e.•,'v..�;; ....e,. DRAINAGE SAND $ GRAVEL NOTES 1. Drainage Sand & Gravel Beneath Floor Slab Should Be Connected Hydraulically To Subdrain Pipe. Use Of 2" Dia. Weep Holes Is One Applicable Method. 2. Subdrain Pipe Should Be Bedded With A Minimum Of 6" Of Drainage Sand & Gravel Surrounding The Pipe. 3. Backfill Within 18" Of Wall Should Be Compacted With Hand -Operated Equipment. Heavy Equipment Should Not Be Used For. Backfill, As Such Operation Could Increase Lateral Earth Pressures And Possibly Damage The Wall. Sieve Size Passing By Weight 1-1/2" 100 4. All Backfill Should Be Placed In 3/4" 70-90 Layers Not Exceeding 6" Loose 1/4" 30-60 Thickness And Densely Compacted. No. 8 20-50 Beneath Paved Or Sidewalk Areas, No. 30 8-30 Compact To At Least 95% Modified No. 50 3-12 Proctor Maximum Density (ASTM: No. 200 0-1. 2 D 1557, Method C). Otherwise (by wet sieving) (non -plastic) Compact To 90% Minimum. SUBDRAIN � BACKFILL BASEMENT WALLS WITH INTERIOR SCHEME SLAB ON GRADE SLOPE OUTSIDE GRADE AWAY FROM STRUCTURE FOR DRAINAGE io - PAVEMENT OR -• "•. •'• i 10 INCHES MIN. % �,o'•' e ° o. OF TAMPED TOPSOIL OR IMPERVIOUS SOIL DRAINAGE a.•,,••. a '' SAND & GRAVEL .•o .v ° SPREAD OR' '6•'• . ;e CONTINUOUS WEEP HOLES SUBDRAIN PIPE :Q,•. a a FOOTING SUBDRAIN PIPE 4" Minimum Dia• Perforated Or Slotted Concrete, Metal, Asbestos -Cement Or Plastic Pipe. Tight Jointed, Sloped To Drain (4" / 100' min, slope), With Clean -Outs. Slotted Pipe-- 1/8" Max. Width Slots Perforated Pipe-- 3/16" to 3/8" Holes Slots Or Perforations Preferentially In Lower Half Of Pi e With Lowe NOTES 1. Drainage Sand & Gravel Inside Stem Walls Should Be Connected Hydraulically To Subdrain Pipe. , Use Of 2" Dia. Weep Holes Is One Applicable Method. 2. Subdrain Pipe Should Be Bedded With A Minimum Of 2" Of Drainage Sand & Gravel Surrounding The Pipe • Quarter Segment Sold For Water Flow. 3. Backfill Within 18" Of Wall Should Be Compacted With Hand -Operated DRAINAGE_____ & GRAVEL Equipment. Heavy Equipment Should To Meet Washington State Specifications Not Be Used For Backfill, As Such Or The Following Gradation. Operation Could Increase Lateral Earth Pressures And Possibly _Sieve Size Passing By Wei ht Damage The Wall. 1-1r2" 100 3/411 4. All Backfill Should Be Placed In /4" 30-90 Layers Not Exceeding 6" Loose No. 8 20-60 Thickness And Densely Compacted. No. 30 8-30 Beneath Paved Or Sidewalk Areas, No. 50 3-12 Compact To At Least 9576 Modified No. 200 0-1. 2 Proctor Maximum Density (ASTM: (by wet sieving) (non -plastic) D1557, Method C). OtherwiseCompact To 907o Minimum. SUBDRAIN & BACKFILL SCHEME SHALLOW FOOTINGS & STEM WALLS F I g u re