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Home My WebLink AboutLUA-06-138_Misc!;! • ~ " ., " cl ~ ,, ~ ,. t " _, ' 5 ~ ~ . ~ " • ; ! 3 j l i J ! ~ l 1 ~ i j ] ~ ! 1 ,, tHi 'ii'-'''' ·1-'"' f'j~~i'l-1 --~·"""',:."'i,"'"' c, c, :2~==~'"'::::!~:!:::,l,i) ~~ fl • i_ l " i I }l~l i,, j l;.'1 '~; " ,., -_. " {''''"ilf' ''· ~,,"J!:f,:..:i. ~l~ :-,.:.._:;":}!7..:;_.j.,.:d";~ . ..., .r: -~----__ ·· I jj• ] l = . , I --. --11 I i· G. ,,r---,-,"'""" ., t !M-i---t~ ~ I { f>l,----,--J,,..IO<I"' I~ • 1 • f l t' , l .H 1-1 ~'.,: ' 3 ;1 J Ci ' 1' l 1 1 t • I t ' t~ ' I I. . !!!ii~ I&.!',, i~ ill Siiti::llil!Ii· ' • 0€VELOPMENT PlANN#IJG CITY OF RENTON OCT 2 6 2007 RECEIVED ~= '" &! HIGHLAND SQUARE TOWN HOMES 343 Union Avenue NE Renton, Washington TECHNICAL INFORMATION REPORT October 20, 2006 Prepared for: KD Properties-Pham, LLC Attn: Johnathan Kurth 1201 Monster Road SW Suite 320 Renton, Washington 98057 (425) 228-5959 office (425) 226-9227 fax Submitted by: Offe Engineers, PLLC Attn: Darrell Offe, P. E. 13932 SE 159t11 Place Renton, Washington 98058-7832 (425) 260-3412 office (425) 988-0292 fax Project Description The purpose of this report is to present a preliminary drainage and downstream review for the proposed Highland Square Town Home 30-unit project in accordance with the City of Renton requirements. The project is located at 343 Union Avenue NE within the City limits of Renton. The Highland Square Town Home project is a proposal to create 30 multi-family residential units on the existing property comprising of 1.61 acres. The project is currently consist of an existing "Thrift Store" and paved parking lot. The existing impervious surfaces were created during the construction of the "Prairie Market" building in February 1970. The existing King County Tax Parcel number is 162305-9098. The existing "Thrift Store" has been abandoned and the parking lot gated off to access. The parcel is bounded to the West by a large apartment complex; to the north and east by retail; and to the south by a newer residential (multi-family) project called "3rd and Union Townhomes". Review of Resources Critical Drainage Area Map • Maplewood Creek/ Cedar River / Lake Washington Watershed Flood plain/floodway (FEMA) Maps • There is no mapped floodplain in the immediate area per the available FEMA map. Sensitive Areas • Wetlands -There are no known wetlands located on the project. • Streams and 100 Year Flood Plains -There are no streams or floodplains on or near the project. • Erosion Hazard Areas -There are no landslide hazard areas on this project. • Landslide Hazard Areas -There are no designated sensitive slopes on or adjoining the property. • Seismic Hazard Areas -The area is not mapped as a seismic hazard area. • Coal Mine Hazard Areas -The property does not appear to be located within a designed coalmine hazard area. -2 - C:\Offe Engineers\! PROJECTS\Davis Group\H1ghland Square\Coorespondence\Level One\storrn report.doc U.S. Department of Agriculture, King County Soils Survey • The underlining soils have been classified by Cornerstone Geotechnical as Glacial n11. Flow Control Application • Since the existing impervious surface was created before January 201, the project is exempt from storm water detention if less than 5,000 square feet is added. The entire project is currently covered with impervious surface from the construction of the "Prairie Market" in 1970. The proposed project would create 0.30 aces of pervious (landscaping/yards) and 1.31 acres of impervious (pavement, driveways, sidewalks). The existing site consists of 0.16 acres of pervious and 1.45 acres of impervious. Therefore the proposed project would DECREASE the amount of impervious surface (no net increase) and no storm water detention is proposed. Water Quality Application • The proposed project DOES NOT trigger the threshold for water quality requirements under the 2005 Manual. Landslide Hazard Drainage Area Map • The site is not located in a landslide hazard drainage area. Field Inspection Offe Engineers has visited the site on several occasions. The most resent visit occurred the morning of October 23, 2006. The site was still paved and the building still standing. The site drains from west to east into the storm system within Union Ave. NE. The existing storm conveyance within Union Ave. flows north towards the intersection of NE 4t11 Street and Union Ave NE. At the time of this site visit, construction activities were occurring at this intersection, which did not allow for viewing of the existing storm system. Based upon plans from the City of Renton files, the storm conveyance flows east within a storm pipe (size not visually verified) approximately 600 feet to a point where the storm system outfalls to the south into Maplewood Creek. Review of the 8 Core Requirements and 5 Special Requirements of the 2005 King County Surface Water Design Manual Offe Engineers has reviewed the Core and Special Requirements in Chapter 1 of the King County Surface Water Design Manual, and addresses each of the requirements as follows: Core Requirement No. 1 -Discharge at Natural Location The project will discharge into the existing storm system within Union Avenue NE. Core Requirement No. 2 -Offsite Analysis The property appears to be an isolated parcel below Union Avenue NE with no water flowing onto the parcel. The surrounding properties are developed and contain the storm water within their projects. The elevation of Union Ave NE is below the site. -3 - C:\Offe Engineers\! PROJECTS\Davis Group\Highland Square\Coorespondence\Level One\storm report.doc Core Requirement No. 3 -Flow Control EXEMPT Core Requirement No. 4 -Conveyance System The onsite conveyance system will be sized to convey the 25 year storm event as required by the 205 Manual; this analysis will be provided as part of the design documents. Core Requirement No. 5 -Erosion and Sediment Control A Temporary Erosion and Sediment Control Plan implementing the Best Management Practices will be designed as part of the final engineering plans for the project in accordance with City of Renton requirements. Core Requirement No. 6 -Maintenance and Operations The Maintenance and Operations Manual for the Highland Square will be included in the Final Storm Drainage Report as part of the final engineering design for the project. Core Requirement No. 7-Financial Guarantees and Liability The Financial Guarantees and Liabilities will be required prior to the project being finalized by the City of Renton. Core Requirement No. 8-Water Quality EXEMPT Special Requirement No. 1 -Adopted Area-Specific Requirements The project is located within the Cedar River Basin Plan. Special Requirement No. 2 -Floodplain/Floodway Delineation This requirement does not apply. Special Requirement No. 3 -Flood Protection Facilities This requirement does not apply. Special Requirement No. 4 -Source Controls This requirement does not apply. Special Requirement No. 5 -Oil Control This requirement does not apply. -4 - C:\Offe Engineer.;\l PROJECTS\Davis Group\Highland Square\Coorespondence\Level One\storm report.doc Appendix A Figures 1. Vicinity Map 2. Existing Topography 3. Proposed Site Plan 4. Drainage System Table 5. Photo Key Map 6. Photos 7. Previous Construction Plans -5 - C:\Offe Engineers\! PROJECTS\Davis Group\Highland Square\Coorespondence\Level One\storm report.doc 1. Vicinity Map w z uJ > 1 0 <!' z 0 z =i NE 4TH\,! ST uJ > <( PROJECT L--r-• 6 LOCATION NE 3RD COURT 5 12TH w z w > <( _J _J <( > =i 0 r.N""E~2~N=D PL ACE w z ST SE 1 PL r---'--__ , w > <( "O C N .,- NE 10TH ST w z w > <( :a, <( =i 0 0 I VICINITY MAP w ~1'----r----r-----.l SE 116th ST w z w > <( w _J z SE 128TH s 2. Existing Topography -----,------,-----; V -N - ~'+==4*===-1 ~ \COMA AVE. NE ·" ' 0 ! i g ' z ~'Pi 7 -._J -f-- m { a • . (Jl ---+-''-"'1-,hOM A PL. NE N '-" .j> ~~, ~~~ i~~, ~ 'I. ., '-.,. " • .. I, / I/ f?. .. \ ... \ .... ""' /.1/'I'/'/ ./// /////////// //,!_,-////////. .. ., t .. \ ' r.; .: ., ,. .. •• \ .. • (FIASISCt~ . .... \. · ... A_• .... ~· -: ....,._. . . . 11.•, '• '.\ ' I •, • •• • • \ \ \ \ UNION AVE. N.E. \ 3. Proposed Site Plan r---------------~ I I\ If,-' .. r .c; z '"---- 4. Drainage System Table Basin: Cedar River Symbol Drainage Component Type, Name, and Size see map Type: sheet flow, swale, stream, channel, pipe, pond; Size: diameter, surface area A Pipe Flow B Pipe Flow C Pipe Flow - D Open Channel-pipe OFF-SITE ANALYSIS DRAINAGE SYSTEM TABLE SURFACE WATER DESIGN MANUAL, CORE REQUIREMENT #2 HIGHLAND SQUARE Subbasin Name: Mapkwood Creek Basin Subbasin Number: Drainage Slope Distance Existing Potential Observations of field Component from site Problems Problems inspector, resource Descriotion :lischarae reviewer, or resident drainage basin, vegetation, % Y. ml = 1,320 ft. constrictions, under capacity, ponding, tributary area, likelihood of problem. cover, depth, type of sensitive overtopping, flooding, habitat or organism overflow pathways, potential impacts area, volume destruction, scouring, bank sloughing, sedimentation, incision, other erosion 12" concrete pipe flowing 1% 330' None None None observed North towards intersection of 4" and Union. Along NE 4" Street Not 240' None apparent NIA Not viewable headin2 east viewable Flow over open pasture 1% 220' None None None observed into Soos Creek -Heavy ! Veeetation at Soos Creek ; Beginning of Maplewood 2% I 530' - - No problem None None observed at time of site visit Creek -heavy vegetation ! appear at outlet of -no water within Maplewood Channel is located on storm pipe -or Creek Ribera Short Plat project visible along the Which City of Renton has channel currently under a permit downstream with Tom Foster c:\offe engineers\) projects\davis group\highland square\coorespondence\Jevel one\drainage system table.doc 5. Photo Key Map w z NE l+-TH ST ~ NE 2ND PL. PHOTO KEY MAP 6. Photos I / .. · l ~d ~\ I~ \ •.\ 7. Previous Construction Plans 632..09 PR~_IR!~ MARKET 6~2-17 NE. 4th ~! 1 1- . "' JACK L. SHERMAN ·>"-N. SEWER 1 'l~J-56 I <10RM 545.2':l 1 125 TL. S7 ' D ' ---------io1 -- _fl.: WALLS :JAN. SEWER :JTORM 2.Q_l 0 • $ 518.36 623.18 TL. 83 " • SAN. SEWER -~1 1069.11 STORM " 1,28!1.32. TL.26 0 :;) ~ I I j~ I m·i i • w ~' ~ ' I ; ' : i ;! l&ll j ·: I >' ., i} I ~· ~j \ai - ' ' i ' i \ ! I i1 1 I l w z w > <[ z 0 z ::) .Mi N ~ 0 " i • e 0 ~ ST ~I MOBJ.L OIL SAN. S£WER-t,go7.l3 160 '-l~R_Y T. fl\,JGGL_g;_S 0 • >;'- < ~::,-"-' .. l-·-, _/ . .-< •,_/ $;!!!; ,::;,::22 \)'·/ -----SAN, $EWER STOFIM _.. ..--.. _ _,,, -<~·-t-~i~,~L(/ /) \ \\ :-~. '<---\, __ ,) t\'t-_...> ,.-...... i ' HENRY T. RUGGLES SAN. SEWER t.819.6!1 STORM 98!1.41 GARY C:, MORITZ SAN. SEWER -*-647.9S STORM 778.U .::,..-' '- -1'-. (,, -'LI!... ~-~:"." ; _,v• ,, S-152. CITY OF RENTON DEPARTMENT .L ......... _. LATE -COMERS AGREEMENT SAJ,,:ITARY a STORM SEWERS-UNION A.'>IE. tH.:. SOUTH OF N.E:. 4TH STRECT W--------· -..., l_, I j D~!!l[G"IED d D ... ~~ \ ~ILi: N<>-~-i ill r~i':-.b,t· Of' :;:.,cl!.!;:[.! Ty£<;:-F.t.t./<;_!;,_ ______ ~ i: l<IG, <>,;;I>.. C.1TY OF ~Q;J o.i•»G o::,,.\>n,1ANC.Ec ill LJ>-lE. & PR.OV10( 5°•1o' C.<S,. ""l_l~j ' ",ST ~0 -- 1,,-, -'-(.".1', T rz." 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(UNION AVCNUE:.) fNGfNEfRS ANAlYST5 . I~ 31.~i ,o' "W"\ ~S.WI-,.\. L ~~-GUCE ~.3G'le'> N Tl'..IJC"'-"1 ill E'tTA!kl'1Ll.G. W"'LL \lo"• \"-o·· RE:.NT01"-l f"..~N\ Cf-..:1 'NA'S 1-.IN.STON 0 'N N E. R. : S ti Y C:O. 1801 \...J 34 n.. St.ATTL'E , WASHII-JGYOf.J 1911 IIT AVENUE SEATTLE. WASH. '11101 _______ _c_:_:.:._,,,_L. __________________ _ 1-,,1 A J. 0 y l I A-1 PLOT PLAN FLOOR PLAf",f . -----·----. -· - A-2 A-3 ELEVATION.S, .SCWEDULE5, 4 MISC. DETAJLS --··--------------------·---·--···--------- FOUNDATIOt--J PLAN 5-1 5-2 "'\,VALL ELEVAT!ON5 4, DETAILS _ 5-.3 [ ~~OF ~:.-~=;;:~-G PLAN M-2 ! PLUMBING, 1--!EATING, ,4: VENT!L.L\TION ---·t------------·------------- E -1 i PARKING LOT UGI-IT /NG --+--~--------·-----·---4 LEGEND E -21; LIGµTJNG f=::>LAN ----------------------·----------·--·-- E-3 i RECEPT.ACLE <f: PO".VER PLAN -------------------------·-·- E--4 RI.SER DIAGRAM) SCHEDuLe5, ETC #-· /ct.·<;~,<\. ,. t...;-;·x·;;.. L-. ~ . ·,,:; .·1'\ _,·>:: ~ . ·;rt{;;t;, , --l .,J/L-D«i-,,~-' . ' -. ::~J:) ... PLOT PLAN P7 F3, ·fFJS ~j ,oo ~~ i I ...l',!.'Di.O R<l>J'-1 --, 1 I 1~-1 T-.li,; ,; 'w ,a· 1~. I :;,; ,r. "" :I" 1ls !_ I I U) "5 ~ ·-~. ~ 0 -2 ::c 0.. z ?-~ c:: 0 = E-t- ;::i z ca 0 E---en z 0 -0.. ~ ~ ~ c..., 'u '" M li ~z !li Oo 5E ~ !~ ;>-t z ~<&/ E-t r.:x::i liQ. -i:i:: ~g u ~t '§ E I ~ ·c °' ~ I 2~ 0" 'l l1i~i l,;:-1-~ ' N I -," : ::I i -'•i :e :, Q,~ Q 0 u.: _, > ~ ....:, a.~,in::E:.C I< .! I I I I GRAPHIC SCALE 2U O !C 20 ---=-=::::l ( IN rEE:'I' ) 1 inch -~o rt. I ------~,-.. --·:1-:Tu-·· --_,_- Z ll!J .l:: :JI J-(/) :r:1~~ -~- ~!tn~ ----: \- I I I --, ~ \ ' " . ~ ·., ....)._H· -\ ~ I e ( """""""'"' J.: ' ..,....--tz-:i ~:~o___;;.:~~o--o --o~~ o---o---0 ---~-----------/ I ~ I 0---0--0-~2~ • I L r---·:--:-· .-:,··_ -f':2:-2tr--o --o ---o ---" --o ---o . o~o HANO , ~, --, -~=ta-r ;=:r-I =ii I I - 1 -=-i-1 -_Li?-11[_-- 0 - ' in "' :lj I I I I BLDG-K ;" 1-;------'c=== -,~ ~- --i--- "' 0 "' ~ z PLACE/REPLACE EXISTING CURB, GUfTER AND SIDEWALK. PER arr sms. AS NECESSARY TO PLACE/REPLACE STORM UNE. SAWCIJT AND PAVEMENT PATCHING PER DETAILS ON SHEEr 6. ... ,,_ __ ··.i•.•.-. --11 I BLDd-G I I I aLDd-E I BLDl-o I I I n I I I II ! II I lrl BLD(t-1-1 I I L acdc-c I _d , --·, a,co-c I . -. I---Le"·. I :"' -' I_ ,\ • I ____ I i~--r_L.-= F1--1 -11" .· Ji ~!i\tt~ ,-~-~ · -.. ~1· -~ I -I ·97 JL'I I C\_," ~ --·. ----~-X~-----• -~. L _ l:~ 1 i -'~04 ~ ..:._ ::__ -----~ ~ --=-w --t --• -N 'T.E ,_" 3rd ...f_T. -. ---. g C -.--, J = SAIVC'JT AND PAVEMENT PATCHING PER DETAILS ON SHEET 6. ' ' 'i :::_;,~ I I k;! ~I ,I f;!\i ~- ' ~I :;:,:,I s, I ll I .i I j __ , l I I I I ' ~ .. :~ -'~·-~-~-=------·--·-_1=::::.c_=-=--;=---~ -1 ::i 1.;!; (/] ~ I I -------; ---~--W-308308 W,398304 S-BUILT SET tn/0£11.:::noJJ: :n f;r,:c LC CATION' MS:D O'!l :;:·~-:-~~.,c,:.:~-~-.:;o;_ ,.,:-.-;;/J. LOCt,TICN W.Y VAP:{. ) ! 1111 "'--I --~--~= I I I I I CHC::CKED FOR COMPLIANCE TO CITY STANDARDS RECOMMENDED F~!.'p~~,L..L.- 1 CONl'l;(.',( TI'J1."!"TICo LOCATIONS. £L~.:•.r.r,:i:.. ~~; T~C,, -\l'D 1.S-l",:J::.T CO!?.MDITS P.E.l'LEc.n,JG MATE:t!AL~ ACl.J,'L ! \:.-.:.:., L>~·:U:;G c:m1.rr;u:CTIQN.hCCuit~TI:LY i:;r;:~CT~ c::.-:.··.·: ·,,: .:;_,"l c;,:,.::,::-:~;c.; Aj ~~.~r.7'.iez?fwe'.:1Df,~ MYC:,•.~.--;; . ::.;:; :!:.i DALEY-MORROW-POBLETE. INC. 7;;~ ~-=' • ;., C·; ... ~ fl Appendix B Technical Information Worksheet -6 - C:\Offe Engineers\! PROJECTS\Davis Group\Highland Square\Coorespondence\Level One\stornn report.doc City of Renton TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 1 PROJECT OWNER AND PROJECT ENGINEER f------------------- Project Owner: KO Properties-Pham,LLC Address: 1201 Monster Road SW SUite 320 Renton, WA 98057 Phone: { 425) 228-5959 attn: Johnathan Kurth Project Engineer: Darrell Offe, P.E. Company: Offe Engineers, PLLC Address/Phone: 13932 SE 159th Place Renton,YIA 98058-7832 ,__ _____ (>e4:.::2=.S)L2::C6c.::Oc...·:c.34-'-'1=-=2=------- Part 2 PROJECT LOCATION AND DESCRIPTION Project Name: Highland Square Town Homes Location Township: 23 North Range: 5 East Section: 16 l __ _ Part 3 TYPE OF PERMIT APPLICATION 1 D Subdivision r~rt 4 OTHER REVIEWS AND PE_R_M_IT_s ___ _, I 1 ·: DFW HPA D Shoreline Management I ~ Short Subdivision 1gLJ Grading i . I Commercial I ,-: u Other ________ _ : COE 404 [] Rockery DOE Dam Safety [I Structural Vaults F EMA Floodplain i I Other i : 1 COE Wetlands ! ________________________ ____, Part 5 SITE COMMUNITY AND DRAINAGE BASIN - Community North Renton Drainage Basin Maplewood Creek / Cedar River / Lake Washington J Part 6 SITE CHARACTERISTICS D River D Stream D Critical Stream Reach D Depressions/Swales D Lake D Steep Slopes Part 7 SOILS Soil Type Slopes Glacial Till, ___ _ 0 -100/o 0 Additional Sheets Attached Part 8 DEVELOPMENT LIMITATIONS REFERENCE [l Ch. 4 -Downstream Analysis ' '.·, I 1 _1 [, iO D D 0 Additional Sheets Attached Part 9 ESC REQUIREMENTS MINIMUM ESC REQUIREMENTS DURING CONSTRUCTION D Sedimentation Facilities D Stabilized Constmctiori Entrance D Perimeter Runoff Control D Clearing and Grading Restrictions D Cover Practices D Construction Sequence D Other D Floodplain--------- 0 Wetlands ________ _ 0 Seeps/Springs D High Groundwater Table 0 Groundwater Recharge .,/) ~ Other ft,k( l Z °ti!__ Erosion Potential Erosive Velcoties No LIMITATION/SITE CONSTRAINT -, MINIMUM ESC REQUIREMENTS AFTER CONSTRUCTION D Stabilize Exposed Surface D Remove and Restore Temporary ESC Facilities D Clean and Remove All Silt and Debris D Ensure Operation of Permanent Facilities D Flag Limits of SAO and open space preservation areas D Other Part 10 SURFACE WATER SYSTEM D Grass Lined D Tank D Infiltration Method of Analysis D Vault D Depression ~ Channel Pipe System D Energy Dissapator D Flow Dispersal Compensation/Mitigati D Open Channel on of Eliminated Site D Wetland D Waiver Storage D Dry Pond D Stream D Regional D Wet Pond Detention Brief Description of System Operation: catch basins within access road discharging into the existing storm system within Union Avenue NE. Facility Related Site Limitations Reference Facility Limitation Part 11 STRUCTURAL ANALYSIS D Cast in Place Vault r] Retaining Wall U Rockery > 4' High I Structural on Steep Slope Other !_ __ I Part12 EASEMENTS/TRACTS i 11 Drainage Easement [_ ! Access Easement [-I Native Growth Protection Easement Tract L---Other Part 13 SIGNATURE OF PROFESSIONAL ENGINEER I or a civil engineer under my supervision has visited the site. Actual site conditions as observed were incorporated into this worksheet and the attachments. To the best of my knowledge the information provided here is accurate. i _;_;,.-- Si ned/Date I J Appendix C Geotechnical Report Page 7 c:\offe engineers\! projects\davis group\highland square\coorespondence\level one\storm report.doc PREPARED FOR DAVIS REAL ESTATE GROUP ' September 27, 2006 yle R. Campbell, · Principal GEOTECHNICAL ENGINEERING STUDY PROPOSED HIGHLANDS SQUARE TOWNHOME DEVELOPMENT 343 UNION AVENUE SOUTHEAST RE...,TON, WASHINGTON ES-0625 Earth Solutions NW, LLC 2881-152nc1 Avenue Northeast, Redmond, Washington 98052 Ph: 425-284-3300 Fax; 425-284-2855 Toll Free: 866-336-8710 . ····-----.. . .--'.'.\ . .,.. ·-~ . i..l. <{'·;, t• i .'j:· ,. 'r! ··._.~ ~, .: .. > >:· : ·!,,- -.r f.· ::·. -,. 1: -~: 1, ---,:_ Reference: King County Map 656 .-[:. .. a- .·; ,,_ " ·-? -L ::! r:n::,¢ ;•,>"t" :. ,. ... -~ ' ::--.- ...... -· (j.J;''_-r,,- By Thomas Brothers Maps Dated 2007 :,.., 11,,av _;.:,.( __ _ ·t=-· .·:c .,..,, . ,; ... NOTE: This plate may contain areas of color. ESNW cannot be responsible for any subsequenl misinterpretation of the infonn ation resu~ng from black & while reproductions of this plate. ·;!\· .:::. -· -···· ·' .I ..... ' ,. ·-~~~---g;:: 1-·.;:.·; «ll!,,".SJ:.::. .... ' ,:,r::-·· ·- , I I, .·,; ' ··:..:.>: r -'.:\~~.);::-/;- :.: ... :.·_,·// Vicinity Map Highlands Square Townhomes Renton, Washington Drwn. GLS Date09/27/2006 Proj. No. 0625 Checked KRC Date Sept. 2006 Plate 1 ,, 1 ! v////////'.d ITP-1 -•-I 1 •. LEGEND TP-1-r-Approximate Location of ESNW Test Pit, Proj. No. ES-0625, Sept. 2006 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 I 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. TP-41 -r- ITP-2 -•-I : n,:, TP-31 -•-I wJ u:i z 0 z :J 1"=100' • Test Pit Location Plan Highlands Square Townhomes Renton, Washington NOTE: This plate may contain areas of coklr. ESNW cannot be Drwn. GLS Date 09/27/2006 Proj. No. 0625 responsible for any subsequent misinterpretation of the information resutting from black & white reproductions of this plate. Checked KRC Date Sept. 2006 Plate 2 l___ ____ _ TABLE OF CONTENTS ES-0625 PAGE INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 General........................................................................... 1 Project Description .... ... .. . ... ... ... .. . . .. ... ... ...... ... ... .. .... ... ... ... . 2 Surface............................................................................ 2 Subsurface....................................................................... 2 Groundwater..................................................................... 3 DISCUSSION AND RECOMMENDATIONS ....................................... 3 General........... .. .. . . . . . . . . . .. .. . . . . . .. .. . .. . . .. . .. . .. .. . . . . . . . .. . .. . . . . . . . . . .. . 3 Site Preparation and Earthwork................................... .. . .. .. . 4 Excavations and Slopes . . . .. . . . .. .. .. . . .. .. .. . .. .. . .. .. . .. . . .. .. . . . . .. . 5 Utility Trench Backfill ............. ___ ...... _ ......................... _....... 5 Pavement Sections ........................................................ .. Foundations.................................. .. ... .. .. . . . .. .. . . .. .. .. .... .. Slab-on-Grade Floors............ . ...................... _ ........ . Retaining Walls. .. . .. .. . .. . . .. . . .. . . . . . .. .. .. . . . .. .. . .. . .. .. _ Drainage .......................................................................... . Rockeries and Modular Block Walls ................................... . Seismic Considerations ...................................................... .. 6 6 7 7 8 8 8 LIMITATIONS........................................................................ .. .. . 9 Additional Services............................................................ 9 GRAPHICS PLATE 1 PLATE 2 PLATE3 PLATE4 APPENDICES Appendix A Appendix B TABLE OF CONTENTS Cont'd ES-0625 VICINITY MAP TEST PIT LOCATION PLAN RETAINING WALL DRAINAGE DETAIL FOOTING DRAIN DETAIL Subsurface Exploration Test Pit Logs Laboratory Test Results Sieve Analysis Results September 27, 2006 ES-0625 Davis Real Estate Group 1201 Monster Road Southwest, Suite 320 Renton, Washington 98055 Attention: Mr. Jonathan Kurth Dear Mr. Kurth: Earth Solutions NW, LLC (ESNW) is pleased to present this report titled "Geotechnical Engineering Study, Proposed Highlands Square Townhome Development, 343 Union Avenue Southeast, Renton, Washington". Based on the conditions encountered during our fieldwork, the majority of the site is underlain by native soils consisting of medium dense to very dense silty sand with gravel and silty sand glacial till deposits. Fill was encountered in the upper one and one-half feet in test pit TP-1, and consisted primarily of medium dense silty sand with gravel and contained trace amounts of organic debris. In our opinion, the proposed townhome development is feasible from a geotechnical standpoint. The proposed structures can be supported on conventional foundations bearing on competent native soils or structural fill, as appropriate Where loose or unsuitable soil conditions are exposed at foundation subgrade elevations, such as the fill soils encountered in the western portion of the site, compaction of the soils to the specifications of structural fill, or overexcavation and replacement with structural fill, may be necessary. The suitability of the existing fill soils can be further evaluated during construction. The opportunity to be of service to you is appreciated. If you have any questions regarding the content of this geotechnical engineerir,g study, please call. Sincerely, EARTH SOLUTIONS NW, LLC Kyle R Campbell, P.E. Principal General GEOTECHNICAL ENGINEERING STUDY PROPOSED HIGHLANDS SQUARE TOWNHOMED DEVELOPMENT 343 UNION AVENUE SOUTHEAST RENTON, WASHINGTON ES-0625 INTRODUCTION This geotechnical engineering study was prepared for the proposed townhome development to be constructed at 343 Union Avenue Southeast in Renton, Washington. The purpose of this study was to review the project information provided to us, perform subsurface exploration at the subject site and prepare geotechnical recommendations for the proposed development. Our scope of services for completing this geotechnical engineering study included the following: • Excavating a series of test pits across accessible areas of the site and providing a characterization of the soil and groundwater conditions; • Providing recommendations for site grading, drainage, structural fill requirements, and other project-specific geotechnical recommendations; • Providing recommendations regarding soil bearing capacity, subgrade preparation, and recommendations for foundation support; • Providing an assessment of the suitability of site soils for use as structural fill, and; • Other pertinent geotechnical recommendations, as appropriate. The following documents were reviewed as part of preparing this geotechnical engineering study: • Composite Geologic Map of King County, Washington, Booth et al, 2006; • King County Soil Conservation Survey (SCS); • Boundary and Topography Survey, prepared by Kenneth R. Anderson and Associates, dated 09/11/06, and; • Preliminary Site Plan/Project Qata, Sheet SP1, prepared by Gerry Slick Design Group, dated 06/20/2006. Earth Solutions tm, LLC Davis Real Estate Group September 27, 2006 Prolect Description ES-0625 Page 2 We understand the subject site will be redeveloped with a 30-unit townhome development and associated infrastructure improvements. Grading will likely be minimal, with cuts and fills of less than about six feet required to achieve design footing elevations. We do not anticipate any below-grade levels associated with this development. At the time this report was prepared, specific building load values were not available. However, based on our experience with similar developments, we anticipate wall loads on the order of 2 to 4 kips per lineal foot column loads on the order of 250 kips, and slab-on-grade loading of approximately 150 psf. We anticipate stormwater generated from new development will be discharge into an existing franchise utility. If the above design estimates are incorrect or change, ESNW should be contacted to review the recommendations in this report. ESNW should review the final design to verify that our geotechnical recommendations have been incorporated. Surface The site is located along the west sid~ of Union Avenue Southeast, just south of Northeast 4lh Street in the Renton Highlands neighborhood of Renton, Washington (see Plate 1, Vicinity Map). The subject property is roughly rectangular in shape, and is bordered to the north by an existing retail building, to the south by a new residential development, to the east by Union Avenue Northeast and to the west by a parking lot and developed parcel. The approximate limits of the property are illustrated on the Test Pit Location Plan (Plate 2). The subject property is currently developed with a single-story retail store which will be removed in order to accommodate the proposed development. Asphalt pavement covers the remainder of the site, except for isolated areas of landscaping. Topography across the site is relatively level, and descends approximately ten feet to the east to meet the existing right-of- way elevation. Subsurface Four test pits were excavated at accessible areas of the subject site for purposes of assessing soil . conditions, and for. p1.1rpQseit of characterizing and classifying the site soils. Access restraints and the extenh:>f existing development largely controlled the location and number of our test sites. Please refer to the test pit logs provided in Appendix A for a more detailed description of the subsurface conditions. Earth Solutions NW, LLC Davis Real Estate Group September 27, 2006 ES-0625 Page 3 Asphalt pavement was encountered a.t the surface of all of our test pit locations. The asphalt was approximately two inches in thickness, and was underlain by about two inches of gravel base material. Fill was encountered at test site TP-1. The fill consisted primarily of medium dense silty sand with gravel (Unified Soil Classification SM) extending to a depth of approximately one and one- half feet below existing grade, and contained trace amounts of organic debris. Underlying the fill and in the remainder of the test sites, we encountered native soils consisting primarily of medium dense to very dense silty sand with gravel (SM) glacial till deposits. The referenced geologic map of the area identifies glacial till (Qvt) deposits throughout the site and surrounding area. The glacial till soils consist primarily of a non-sorted mixture of silt, sand and gravel in a compact condition at depth. Review of the King County Soil Survey (SCS) identifies Alderwood series (AgC) glacial till soils at the site and surrounding properties. The soil conditions encountered during our fieldwork generally correlate with the geologic and soil map designations. Based on the geologic mapping information and the soil conditions encountered during our fieldwork, we interpret the soils at the site to represent glacial till deposits. Groundwater Groundwater seepage was not encountered during the time of our field exploration (September 22, 2006). Due to the generally limited extent and depth of the building excavations anticipated for this project, we do not anticipate excessive seepage will be encountered in the site excavations, or that groundwater seepage will create significant difficulties during construction, except possibly in deeper utility excavations. However, it is important to note that groundwater seepage rates and elevations fluctuate depending on many factors, including precipitation duration and intensity, the time of year, and soil conditions. In general, groundwater flow rates are higher during the wetter, winter months. DISCUSSION AND RECOMMENDATIONS General Based on the results of our study, construction of the proposed townhome development is feasible from a geotechnical standpoint. The primary geotechnical considerations associated with the proposecj development include _ site grading and_ earthwork, foundation support, structural fill placement, teiifporary excavations and sliitabiiity of the on-site soils for use as structural fill. Earth Solutions NW, LLC Davis Real Estate Group September 27, 2006 ES-0625 Page4 Based on the results of our study, ttae proposed townhome structures can be supported on conventional spread and continuous foundations bearing on competent native soils or structural fill, as appropriate. We anticipate that competent native soil suitable for support of foundations will generally be encountered at depths of between two to four below existing grades. Where loose or unsuitable soil conditions are exposed at foundation subgrade elevations, compaction of the soils to the specifications of structural fill, or overexcavation and replacement with structural fill may be necessary. In our opinion, the soils generated from cuts throughout the site should generally be suitable for use as structural fill. The silty sand soils encountered at the majority of the exploration sites will generally exhibit good soil strength when compacted to structural fill specifications. Recommendations for structural fill placement are discussed in the Site Preparation and Earthwork section of this study. This study has been prepared for the exclusive use of Davis Real Estate Group, and their representatives. No warranty, expressed or implied, is made. This study has been prepared in a manner consistent with the level of care and skill ordinarily exercised by other members of the profession currently practicing under similar conditions in this area. Site Preparation and Earthwork With respect to earthwork, the primary considerations at this site are related to fill placement and compaction, temporary excavatic,ns, suitability of the native soils for use as structural fill, and appropriate erosion control measures. From a geotechnical standpoint, the soils encountered at the test sites are genmally suitable for use as structural fill. In our opinion, the site soils anticipated to be exposed during site excavations would exhibit a moderate to high sensitivity to moisture. The soils encountered at the test sites were generally in a moist condition at the time of the exploration (September 2006). Soils encountered during site excavations that are excessively over the optimum moisture content may require moisture conditioning prior to placement and compaction. During periods of dry weather, the on-site soils should generally be suitable for use as structural fill provided the moisture content is at or near the optimum level at the time of placement. If the on-site soils cannot be successfully compacted, the use of an imported soil may be necessary. Imported soil intended for use as struttural fill should consist of a well graded granular soil with a maximum aggregate size of four inclies, and a moisture content that is at or near the optimum level. During wet weather conditionE;, imported soil intended for use as structural fill should consist of a well.graded granular soil with a fines content of five percent or less defined as the percent passing the #200 sieve, based on the minus three-quarter inch fraction. Structural fill is defined as compacted soil placed in foundation, slab-on-grade, and roadway areas. Fills placed to construct permanent slopes and throughout retaining wall and utility trench backfill areas are also considered structural fill. Soils placed in structural areas should be compacted to a relative compaction of 90 percent, based on the maximum dry density as determined by the Modified Proctor Method (ASTM D-1557) and placed in maximum 12 inch lifts. In pavement areas, the upper 12 inches of the structural fill should be compacted to a relative compaction of at least 95 percent. Earth Solutions NW, LLC Davis Real Estate Group September 27, 2006 ' ES-0625 Page 5 Temporary erosion control measures should include, at a minimum, silt fencing placed along the development perimeter of the corstruction site. As appropriate, temporary construction entrances should consist of at least six inches of quarry spalls to help minimize off-site soil tracking and to help provide a stable temporary road base. Mulching of exposed earth surfaces, and other measures for controlling drainage and erosion during construction should be considered, as appropriate. Excavations and Slopes The Federal and state Occupation Safety and Health Administration (OSHAMIISHA) classifies soils in terms of minimum safe slope inclinations. Based on the soil conditions encountered during our fieldwork, the fill and weathered till soils observed in the upper approximately two to four feet at our test sites would be classified by OSHAMIISHA as Type C. Temporary slopes over four feet in height in Type C soils should be sloped at an inclination of 1.5H:1V, or flatter. If appropriate slopes cannot be achieved, temporary shoring should be used to stabilize the excavations. The unweathered glacial till soils encountered below about four feet would be classified by OSHAMIISHA as Type A. Temporary slopes over four feet in height in Type A soils should be sloped at an inclination of 0.75H:1V or flatter, respectively. Permanent slopes should maintain a gradient of 2H:1V, or flatter, and should be planted with an appropriate species of vegetation to enhance stability and to minimize erosion. The geotechnical engineer should observe temporary and permanent slopes to verify that the inclination is appropriate, and to provide additional slope grading recommendations, as necessary. Utility Trench Backfill Based on the subsurface conditions encountered at the test sites, the native soils should be suitable for support of utilities. Organic or highly compressible soils encountered in the trench excavations should not be used for supporting utilities. In general, the native soils observed at the test sites should generally be suitable for use as structural backfill in the utility trench excavations, provided the soil is at or near the optimum moisture content at the time of placement and compaction. Moisture conditioning of the soils may be necessary at some locations prior to use as structural fill. Utility trench backfill should be placed and compacted to the specifications of structural fill provided in this report, or to the applicable specifications of the city or county jurisdictions, as appropriate . . -· ,-. ·-·· ., •,-,. .. _- Earth Solutions NW, LLC Davis Real Estate Group September 27, 2006 Pavement Sections ES-0625 Page 6 The performance of site pavements is largely related to the condition of the underlying subgrade. To ensure adequate pavement performance, the subgrade should be in a firm and unyielding condition when subjected to proofrolling with a loaded dump truck. Structural fill in pavement areas should be compacted to the specifications detailed in the Site Preparation and Earthwork section of this report. It is possible that soft, wet, or otherwise unsuitable subgrade areas may still exist after base grading activities. Areas of unsuitable or yielding subgrade will require remedial measures such as overexcavation and thicker crushed rock or structural fill sections prior to pavement. For relatively lightly loaded pavements subjected to automobiles and occasional truck traffic, the following pavement sections can be considered: • Two inches of asphalt concrete (AC) placed over four inches of crushed rock base (CRB), or; • Two inches of AC placed over three inches of asphalt treated base (ATS). The AC, ATB and CRB materials should conform to WSDOT specifications. Heavier truck-traffic areas generally require thicker pavement sections depending on site usage, pavement life expectancy, and site traffic. The geotechnical engineer should provide appropriate pavement section design recommendations for truck traffic areas and right-of-way improvements, as necessary. Additionally, the City of Renton Road Standards may supersede the recommendations provided in this report. Foundations The proposed townhome structures can be supported on conventional spread and continuous foundations bearing on competent native soils or structural fill, as appropriate. We anticipate that competent native soil suitable for support of foundations will generally be encountered at depths of between two to four feet below existing grades. Where loose or unsuitable soil conditions are exposed at foundation subgrade elevations, compaction of the soils to the specifications of structural fill, or overexcavation and replacement with structural fill may be necessary. Assuming the foundations are sup~orted _ on competent, undisturbed native soils or suitable · structural fill, the folloWing para·m~Hers should be usea for foundation design: Earth Solutions NW, LLC Davis Real Estate Group September 27, 2006 • Allowable Soil Bearing Capacity • Friction • Passive Resistance • Total Settlement • Differential Settlement 3,500 psf 0.40 350 pcf (equivalent fluid) 1 inch 0.5 inches ES-0625 Page 7 For short term wind and seismic loading, a one-third increase in the allowable soil bearing capacity can be assumed. A factor-of-safety of 1.5 has been applied to the friction and passive resistance values. Slab-On-Grade Floors Slab-on-grade floors for the proposed buildings should be supported on a firm and unyielding subgrade consisting of competent native soil or structural fill. Unstable or yielding areas of the 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 five percent or less (percent passing the #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. Retaining Walls Retaining walls should be designed to resist earth pressures and any applicable surcharge loads. For design, the following parameters can be assumed for retaining wall design: • Active Earth Pressure (Yielding Wall) • At-Rest Earth Pressure (Restrained Wall) • Traffic Surcharge (Passenger Vehicles) • Passive Resistance,, · • ,.,.. , .• • Coefficient of Friction 35 pcf (equivalent fluid) 50 pcf 70 psf (rectangular distribution) -350 pcf (equivalent fluid) 0.40 Earth Solutions NW, LLC Davis Real Estate Group September 27, 2006 ES-0625 Page8 Additional surcharge loading from foundations, sloped backfill, or other loading should be included in the retaining wall design, as appropriate. Drainage should be provided behind retaining walls such that hydrostatic pressures do not develop. If drainage is not provided, hydrostatic pressures should be included in the wall design, as appropriate. The geotechnical engineer should review retaining wall designs to verify that appropriate earth pressure values have been incorporated into design, and to provide additional recommendations, as necessary. 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. The upper one foot of the wall backfill can consist of a less permeable (surface seal) soil, if desired. A rigid, perforated drain pipe should be placed along the base of the wall, and connected to an appropriate discharge location. We have provided a typical retaining wall drainage detail on Plate 3 of this report. Drainage Groundwater seepage was not observed in any of the test sites at the time of our fieldwork (September 2006). However, the presence of groundwater seepage should be expected at the dense till contact in the winter and spring months. In the event groundwater seepage is encountered, temporary measures to control seepage and surface water runoff during construction would likely involve interceptor trenches and sumps, as necessary. In our opinion, perimeter drains should be installed at or near the invert of the building footings. A typical footing drain detail is provided on Plate 4 of this report. Rockeries and Modular Block Walls In our opinion, the use of rockeries or modular block walls at this site is feasible from a geotechnical standpoint. Rockeries or modular block walls over four feet in exposed height will require an engineered design. ESNW can provide engineered rockery and modular block wall designs, upon request. At a minimum, ESNW should review the final wall locations and heights, as necessary. Seismic Considerations The 2003 International Building Code specifies several soil profiles that are used as a basis for seismic design of structures. Based on the soil conditions observed at the test sites, Site Class C, from table 1615.1.1, should be used for design. In our opiril6r{ liqOefacfion' SLfsceptifiility at this site ls low. Th.a relative density of the site soils and the absence of a uniform, shallow groundwater table is the primary basis for this designation. Earth Solutions NW, LLC Davis Real Estate Group September 27, 2006 LIMITATIONS ES-0625 Page9 The recommendations and conclusions provided in this geotechnical engineering study 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 geotechnical engineering study if variations are encountered. Additional Services ESNW should have an opportunity to review the final design with respect to the geotechnical recommendations provided in this report. ESNW should also be retained to provide testing and consultation services during construction. Earth Solutions NW. LLC 18" Min . .. 0 o o on oo o ·oO •o oO 6_ 0 o ,;;,, o 0 o0°,;,, A 0 0 o oc<) • o o O V a 00 0 D O 0 a 1} o o o _.. 0 o oo OoOoo 8 0 o 0 ooo00oOoO 0 DO O 0 OooO O 000° O O o. 00 q, 0: 0 0 0°0 o oo o 0 o 0 • d' 0 0 0 0 0 ,.,,Ooo oQo D Do O OOOOO 0 0 oo O -0 0 CJ 0 ooo 00 0 o Q O D i c,.; 0 0 <> 0 0 0 0 0 00 0 0 0 0 a -o O o 0 & 0 0 0 °~ Cl:,. 0 C\i. 0 o:ooa Q9no 0 Dv O :e."' o<>o O O O O D o ...,.oO 6o 0 DQ Cl O O n_ 0 ° o 0 00-,r 0 o O o O 0:, 0 D Q t9 ~o 0 8 o O OoOa o 0':, o 0 0 0 0 Structural Fill NOTES: ' Perforated Drain Pipe (Surround In Drain Rock) • Free Draining Backfill should consist of soil having less than 5 percent fines. Percent passing #4 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" Drain Rock. LEGEND: [ill] ~~~:U::J!tother 0°0 0 . o 'l:> 0 Free Draining Structural Backfill • • • 1 inch Drain Rock SCHEMATIC ONLY -NOTTO SCALE NOT A CONSTRUCTION DRAWING RETAINING WALL DRAINAGE DETAIL Highlands Square Townhomes Renton, Washington Drwn. GLS Date09/27/2006 Proj. No. 0625 Checked KRC Date Sept. 2006 Plate 3 Slope ... ;.: .. 2" (Min.) Perforated Rigid Drain Pipe (Surround with 1" Rock) NOTES: • Do NOT tie roof downspouts to Footing Drain. • Surface Seal to consist of 12" of less permeable, suitable soil. Slope away from buHding. LEGEND: Surface Seal; native so~ or other low permeability material. 1" Drain Rock SCHEMATIC ONLY-NOT OT SCALE NOT A CONSTRUCTION DRAWING FOOTING DRAIN DETAIL Highlands Square Townhomes Renton, Washington Drwn. GLS Date09/27/2006 Proj. No. 0625 Checked KRC Date Sept 2006 Plate 4 APPENDIX A SUBSURFACE EXPLORATION ES-0625 The subsurface conditions at the site were explored by excavating a total of four test pits using a trackhoe and operator contracted by ESNW. The approximate test pit locations are illustrated on Plate 2 of this report. The test pit logs are provided in this Appendix. The subsurface exploration was completed in September 2006. Earth Solutions NW, LLC Earth Solutions NWLLc SOIL CLASSIFICATION CHART MAJOR DIVISIONS LETTER TYPICAL DESCRIPTIONS COARSE GRAINED SOILS MORE THAN 50% OFMATERW.IS 1.ARGERTHAN NO. 200 SIEVE SIZE FINE GRAINED SOILS MORE THAN !IO% OP MATERW. IS . SMI\LI.EIUHAN IIO. 2llO SIEVE SIZE GRAVEL AND GRAVELLY SOILS MORE lHAN 50% OF COARSE FRACT10N RETAINED ON NO. 4 SIEVE SANO ANO SANDY SOILS CLEAN GRAVELS GRAVELS WITH FINES (APPRECIABLE AMOUNT OF ANES) CLEAN SANDS (UTTtE OR NO ANES) SANDS WITH MORETHAN50% FINES OF COARSE FRACTION PASSING ON NO. 4 SIE\IE (APPRECIABLE SILTS ANO CLAYS SILTS AND CLAYS AMOUNT OF FrNES) UQUIDLIMIT LESS THAN 50 LIQUID LIMIT GREATER THAN 50 HIGHLY ORGANIC SOILS GW GP GM GC SW SP SM SC ML CL OL MH CH OH PT WBJ.-GRADED GRAVELS, GRAVEL· SAND MIXTURES, UTTI.E OR NO FINES POORLY-GRADED GRAVELS, GRAVEL-SAND MIXT\JRES, UTil.E OR NO FINES SILTY GRAVELS, GRAVEL• SAND. SILT MIXTURES CLAYEY GRAVELS, GRAVEL· SANO· Cl.AV MIXT\JReS WELL-GRADED SANOS, GRAVELL V SANOS. urnE OR NO FINES POORLV-GRADEO SANOS, GRAVELLY SAND, Lrm.E OR NO FINES SLTY SANDS, SAND • SILT MIXTURES CLAYEY SANOS, SANO -CLAY MIXTURES INORGANIC SILTS AND VERY FJNE SANDS. ROCK FLOUR, SIL TY OR CLAYEY FINE SANDS OR ClAYEY SJLTS wmt SLIGHT PLASTICITY INOR6'NIC CLAYS OF LOW TO MEDIUM PlASTICITY, GRAVELLY CLAYS. SANDY CLAYS, SILTY CLAYS, LEAN CLAYS ORGANIC SIL TS NII> ORGANJC Su.TY ClAYS OP LOW PLASTICITY · INORGANJC SILTS, MICACEOUS OR DIATOMACEOUS FINE SAND OR SLTVSOILS IIIORGANICCLAYSOFHIGH PIASTICITY ORGANIC CLAYS OF MEDJUM TO HIGH Pl.ASTICITY. ORGANIC SILTS PEAT. HUMUS, SWPJIIP SOILS WITH HIGH ORGANIC CONITENTS DUAL SYMBOLS are used to indicate borderline soil classifications. The discussion in the te)d of this report is necessary for a proper understanding of the nature of the material presented In the attached logs. • Earth Solutions l'M/, LLC TEST PIT NUMBER TP-1 2881 152nd Avenue N.E. Redmond, WA 98052 PAGE 1 OF 1 Telephone: 4252843300 Fax: 4252842855 CLIENT Qll!!I BHIIY GrouR PROJECT NAME H!!lhland l?guare Townhomas PROJECT NUIEER 0625 PROJECT LOCATION Renton, Washlncnon DAlESTARTB> 9/22/06 COIIPI.EIED 9122106 GROUND ELEVATION 410ft 11:ST PIT SIZE EXCAVATION CONTRACTOR AlklnsExcavatina GROUND WATER LEVELS: EXCAVATION IIIE1HOD AT TlliE OF EXCAVATION LOGGFOB'f ll§B CHECKEDB'f SSR AT END OF EXCAVATION NOTES r Asohalt Pavement, z· GJ8V81 Base AFTER EXCAVATION UI ~o: .,; 0 fg ~1 TESTS t.j !§ MATERIAL DESCRIPTION "' C O.:::, ::;j !z C) D m Brown silly SAND, medium dense, moist (Fm) SM ~ . 1.5 -lraoe otganics, lrace gravel ,408.5 •. ' Reddish brown siNy SAND, medium -· moist .-.. SM '• ~-..trace gravel and organics ·--· MC= 13.00% -. . . ~ :: ~.-3.5 406.5 ... Gray silty SAND with gravel, dense, moist . ·-:: .... _L MC=8.60% Fines = 16.40% ., :· .. .. .. -... . .. SM .... • . · . -. . ' __ ·. ·.·· ... -.. • ---decrease in gravel content :_:_ :-: .. ,....1!L MC s 11.00% .. • 10.0 400.0 Tesl pt tenninated at 10.0 -below existing grade. No groundwater encountered during excavation. Bottom of-pit et 10.0 feel .•. ! • Earth Solutions NW, LLC TEST PIT NUMBER TP-2 2881152nd Avenue N.E. Redmond, WA 98052 PAGE 1 OF 1 Telepllone: 4252843300 Fax: 42521142855 CLIENT 12~1! B!!!!!ll Gn>UR PROJECT NAME Highland Sauare Townmu PROJECT NUIIIIER M?S PROJECT LOCATION Rento!l, Washlnaton DATE STARTED 9J22/06 COMPLET1:D 9/22106 GROUND ELEVATIOH 408ft TEST PIT SIZE EXCAVATION CONTRACTOR Al!sl!!I Excava~ng GROUND WATER LEIIELS: EXCAVATION IE1llOO ATTIME OF EXCAVATION LOGGED BY SSR CIECKEDBY $SR AT END OF EXCAVATION MOTEi 2" i\!l!!J!!lt PaVffll~ 2" Gravel Base AFTER EXCAVATION w a.. Q fg ~ffi .; ~!I TESTS <.j !§ MATERIAL DESCRIPTION (I) 0 ii :j (!) 0 •. ; . Brown silty SAND with gravel, medium dense, moist -:·:=.:.: e -:::~{· r -. ·. :. • : r ~ -:_::..,· { . ;. :• . -becomes dense . : .- --MC=S.30% :_:_ :: -:= .. . . SM :. :'. ;. · . .... e -.. ·:. -slightly cemented ·-;_· .. _L ... . . .. . . .. :: ~-.;: .. --.· .• .. ·_: 7.0 401.0 -MC= 10.70% Test ptt terminated at 7.0 feet below existing grade. No groundwater encountered during excavation. Bottom of test pit at 7. 0 feet. ; . r .. - => !z 0 I ~ i t iii ~ w z w "' • Earth Solutions NW, LLC TEST PIT NUMBER TP..J 2881 152nd Avenue N.E. -and, WA 98052 PAGE 1 OF 1 Telephone: 4252843300 Fax: 4252842855 CLIENT Clavls Reallv Grou~ PROJECTNME H!ghland §guan, Townhomes PROJECT ..-ER 0625 PROJECT LOCATION Renton, Washl!!lllon Di\lESTARTED 9/22/06 CCN'l.El1:D 9/22/06 GROUND B.EVATION 402!! TEST PIT SIZE EXCAVATION CONTRACTOR Aikins Excavating GROUND WATER LEI/ELS: EXCAVATION METHOD ATTIIE OF EXCAVATION LOGGEDBY S!?R CtECKEDBY SSR AT END OF EXCAVATION NOTES 2" Asoahtt Pavement 2" Gravel Base AFTER EXCAVATION ~ !,l fe ~ 15 <Ii ;1 TESTS 0 "'8 MA.lERIAL DESCRIPTION w-<Ii i--Q :, C) n ··:: .:: Brown silty SAND wllh gravel, medium -sa. moist -:·::.:.: • .• r . ···:· -:-.. ~ . : ~: -becomes dense ._ ·. :-. . ; ~ MC=8.00% . ~ ·.· ~ . Fines = 23.00% . · . . . -.. SM :_ :. r •. ~ ~: -.. ·. :-. . - :_:·--- _L_ ·.[.· :-. . · ··:.· ·-·· -.. -.. . .. 7.0 395.0 MC=9.90% Test pit tenninated at 7.0 feet bekm existing grade. No groundwater encountered duriJ19 excavation. Bottom of test p~ at 7.0 feet. i § .:_·,. - !i i i i f: iii ~ ; APPENDIX B LABORATORY TEST RESULTS ES-0625 Earth Solutions NW, LLC ' ,. • EMh SolutiOns J>N>I, LLC GRAIN SIZE DISTRIBUTION 2881152nd Avenue N.E. Redmond, WA 96052 Telephone: (425)284-3300 Fax: (425)284-2855 CL.JENT Davis Rea~ PROJECTIIAM: H!ghlands §guare PROJECT NUMBER !;5-625 PROJECT LOCATION B!!!!l2D U.S. SIEVE OPENING IN l~S I U.S. SIEVE N,__ERS I HYDROMETER 6 4 3 2 1.5 1 112318 3 • 6 810 1416 20 30 40 50 60 100140200 100 I I ~ r l" lT : I I 95 \ : 90 \ 85 : .._ '\ ~~ ' 80 : N : \ "' 75 '\ \ : 70 \, \ : !i: 65 "' !.2 60 ~ ~ 55 ' 0:: . w 50 : • z ii'. l : !;; 45 ' w : \ 0 40 0:: : ~ \ 35 1---f----\ \i 30 \ '1ttl 25 20 I "\ . 15 10 5 : 0 100 10 I 0.1 O.o1 0.001 GRAIN SIZE IN MIWMETERS COBBLES GRAVEL I SANO SILT OR CLAY coarse I fine I coarse medum I fine Specimen Identification Classification LL PL Pl Cc Cu !! • TP-01 5.0ft. Ught bro'Ml silty SAND with gravel, SM § Ill TP~ 3.0ft. Gray silty SAND, SM b ... TP-04 " 4.0ft. Gray silty SAND with oravel, SM ~ ~ Ii= Specimen Identification 0100 060 030 010 %Gravel %Sand %Sill %Clay " ~-TP-41 5.0ft. 19 1.076 0.197 19.5 64.0 16A 1111 TP~ 3.0ft. 19 0.532 0.134 13.2 63.6 23.0 !!I"' TP-04 4.0ft. 19 0.47 0.142 16.6 61.5 21.9 .. z ~ 4 COPIES REPORT DISTRIBUTION ES-0625 Davis Real Estate Group 1201 Monster Road Southwest, Suite 320 Renton, Washington 98055 Attention: Mr. Johnathan Kurth Earth Solutions NW, LLC PREPARED FOR DAVI~ REAL ESTATE GROUP September 27, 2006 yle R. Campbell, · Principal GEOTECHNICAL ENGINEERING STUDY PROPOSED HIGHLANDS SQUARE TOWNHOME DEVELOPMENT 343 UNION AVENUE SOUTHEAST REt.JTON, WASHINGTON ES-0625 Earth Solutions NW, LLC 2881 -152nd Avenue Northeast, Redmond, Washington 98052 Ph: 425-284-3300 Fax: 425-284-2855 Toll Free: 866-336-8710 TABLE OF CONTENTS ES-0625 PAGE INTRODUCTION ............ ... ...... ......... ...... ............... ...... ......... ..... 1 General .. .. .. .. .. .. . ... .. .. . . ... .. . . .. .. . .. .. .. ... .. .. .. ... . .. .. .... .. . ... .. ...... 1 Project Description .... .... . . ... . .. ... .. . ... ... ... ......... ... ... ... .......... 2 Surface............................................................................ 2 Subsurface....................................................................... 2 Groundwater..................................................................... 3 DISCUSSION AND RECOMMENDATIONS... . .. . . . .. .. .. . . . .. . .. . .. .. . . .. .. . 3 General........... .. . .. . .. . . . . . .. .. . . . . .. .. .. . .. .. . . .. . .. . .. . . . . . . . .. .. . . .. . . .. .. .. 3 Site Preparation and Earthwork........................................... 4 Excavations and Slopes . .. .. .. .. . . . . .. .. .. .. .. .. . .. .. . .. .. . .. .. .. .. . . . .. .. . 5 Utility Trench Backfill... . .. .. . .. .. . . . .. . . . .. .. .. . .. .. .. . .. . . . .. . .. . .. . .. . .. . 5 Pavement Sections........................ . . . .. . .. .. .. . . . . . .. . . .. . . . . .. .. . . .. 6 Foundations .................................. _........ .... ...... . .. .. . ...... . .. 6 Slab-on-Grade Floors ............ _........ .. . .. . .. . .. . .. . .. . . .. .. . .. .. .. . . . . .. 7 Retaining Walls................... . ... . .. ... ... ... ... ... ... ...... ... .. ..... ... . 7 Drainage........................................................................... 8 Rockeries and Modular Block Walls . .. . . . . .. . .. .. . .. . .. . .. . .. . .. . .. . . . . 8 Seismic Considerations............... .. .. .. .. . .. .. .. .. .. . . .. .. .. . .. .. .. . . .. . .. 8 LIMITATIONS ....................................................................... 9 Additional Services............................................................ 9 GRAPHICS PLATE 1 PLATE 2 PLATE 3 PLATE 4 APPENDICES Appendix A Appendix B TABLE OF CONTENTS Cont'd ES-0625 VICINITY MAP TEST PIT LOCATION PLAN RETAINING WALL DRAINAGE DETAIL FOOTING DRAIN DETAIL Subsurface Exploration Test Pit Logs Laboratory Test Results Sieve Analysis Results September 27, 2006 ES-0625 Davis Real Estate Group 1201 Monster Road Southwest, Suite 320 Renton, Washington 98055 Attention: Mr. Jonathan Kurth Dear Mr. Kurth: Earth Solutions NW, LLC (ESNW) is pleased to present this report titled "Geotechnical Engineering Study, Proposed Highlands Square Townhome Development, 343 Union Avenue Southeast, Renton, Washington". Based on the conditions encountered during our fieldwork, the majority of the site is underlain by native soils consisting of medium dense to very dense silty sand with gravel and silty sand glacial till deposits. Fill was encountered in the upper one and one-half feet in test pit TP-1, and consisted primarily of medium dense silty sand with gravel and contained trace amounts of organic debris. In our opinion, the proposed townhome development is feasible from a geotechnical standpoint. The proposed structures can be supported on conventional foundations bearing on competent native soils or structural fill, as appropriate. Where loose or unsuitable soil conditions are exposed at foundation subgrade elevations, such as the fill soils encountered in the western portion of the site, compaction of the soils to the specifications of structural fill, or overexcavation and replacement with structural fill, may be necessary. The suitability of the existing fill soils can be further evaluated during construction. The opportunity to be of service to you is appreciated. If you have any questions regarding the content of this geotechnical engineering study, please call. Sincerely, EARTH SOLUTIONS NW, LLC Kyle R. Campbell, P.E. Principal General GEOTECHNICAL ENGINEERING STUDY PROPOSED HIGHLANDS SQUARE TOWNHOMED DEVELOPMENT 343 UNION AVENUE SOUTHEAST RENTON, WASHINGTON ES-0625 INTRODUCTION This geotechnical engineering study was prepared for the proposed townhome development to be constructed at 343 Union Avenue Southeast in Renton, Washington. The purpose of this study was to review the project information provided to us, perform subsurface exploration at the subject site and prepare geotechnical recommendations for the proposed development. Our scope of services for completing this geotechnical engineering study included the following: • Excavating a series of test pits across accessible areas of the site and providing a characterization of the soil and groundwater conditions; • Providing recommendations for site grading, drainage, structural fill requirements, and other project-specific geotechnical recommendations; • Providing recommendations regarding soil bearing capacity, subgrade preparation, and recommendations for foundation support; • Providing an assessment of the suitability of site soils for use as structural fill, and; • Other pertinent geotechnical recommendations, as appropriate. The following documents were revie·Ned as part of preparing this geotechnical engineering study: • Composite Geologic Map of King County, Washington, Booth et al, 2006; • King County Soil Conservation Survey (SCS); • Boundary and Topography Survey, prepared by Kenneth R. Anderson and Associates, dated 09/11/06, and; • Preliminary Site Plan/Project [)ata, Sheet SP1, prepared by Gerry Slick Design Group, dated 06/20/2006. Earth Solutions NW, LLC Davis Real Estate Group September 27, 2006 Project Description ES-0625 Page2 We understand the subject site will be redeveloped with a 30-unit townhome development and associated infrastructure improvements. Grading will likely be minimal, with cuts and fills of less than about six feet required to achieve design footing elevations. We do not anticipate any below-grade levels associated with this development. At the time this report was prepared, specific building load values were not available. However, based on our experience with similar developments, we anticipate wall loads on the order of 2 to 4 kips per lineal foot column loads on the order of 250 kips, and slab-on-grade loading of approximately 150 psf. We anticipate stormwater generated from new development will be discharge into an existing franchise utility. If the above design estimates are incorrect or change, ESNW should be contacted to review the recommendations in this report. ESNW should review the final design to verify that our geotechnical recommendations have been incorporated. Surface The site is located along the west sid~ of Union Avenue Southeast, just south of Northeast 4th Street in the Renton Highlands neighborhood of Renton, Washington (see Plate 1, Vicinity Map). The subject property is roughly rectangular in shape, and is bordered to the north by an existing retail building, to the south by a new residential development, to the east by Union Avenue Northeast and to the west by a parking lot and developed parcel. The approximate limits of the property are illustrated on the Test Pit Location Plan (Plate 2). The subject property is currently developed with a single-story retail store which will be removed in order to accommodate the proposed development. Asphalt pavement covers the remainder of the site, except for isolated areas of landscaping. Topography across the site is relatively level, and descends approximately ten feet to the east to meet the existing right-of. way elevation. Subsurface Four test pits were excavated at accessible areas of the subject site for purposes of assessing soil conditions, and for purposes of characterizing and classifying the site soils. Access restraints and the extent of existing development largely controlled the location and number of our test sites. Please refer to the test pit logs provided in Appendix A for a more detailed description of the subsurface conditions. Earth Solutions NW, LLC Davis Real Estate Group September 27, 2006 ES-0625 Page 3 Asphalt pavement was encountered at the surface of all of our test pit locations. The asphalt was approximately two inches in thickness, and was underlain by about two inches of gravel base material. Fill was encountered at test site TP-1. The fill consisted primarily of medium dense silty sand with gravel (Unified Soil Classification SM) extending to a depth of approximately one and one- half feet below existing grade, and contained trace amounts of organic debris. Underlying the fill and in the remainder of the test sites, we encountered native soils consisting primarily of medium dense to very dense silty sand with gravel (SM) glacial till deposits. The referenced geologic map of the area identifies glacial till (Qvt) deposits throughout the site and surrounding area. The glacial till soils consist primarily of a non-sorted mixture of silt, sand and gravel in a compact condition at depth. Review of the King County Soil Survey (SCS) identifies Alderwood series (AgC) glacial till soils at the site and surrounding properties. The soil conditions encountered during our fieldwork generally correlate with the geologic and soil map designations. Based on the geologic mapping information and the soil conditions encountered during our fieldwork, we interpret the soils at the site to represent glacial till deposits. Groundwater Groundwater seepage was not encountered during the time of our field exploration (September 22, 2006). Due to the generally limited extent and depth of the building excavations anticipated for this project, we do not anticipate excessive seepage will be encountered in the site excavations, or that groundwater seepage will create significant difficulties during construction, except possibly in deeper utility excavations. However, it is important to note that groundwater seepage rates and elevations fluctuate depending on many factors, including precipitation duration and intensity, the time of year, and soil conditions. In general, groundwater flow rates are higher during the wetter, winter months. DISCUSSION AND RECOMMENDATIONS General Based on the results of our study, construction of the proposed townhome development is feasible from a geotechnical standpoint. The primary geotechnical considerations associated with the proposed development include site grading and earthwork, foundation support, structural fill placement, temporary excavations and suitability of the on-site soils for use as structural fill. Earth Solutions NW. LLC Davis Real Estate Group September 27, 2006 ES-0625 Page4 Based on the results of our study, the proposed townhome structures can be supported on conventional spread and continuous foundations bearing on competent native soils or structural fill, as appropriate. We anticipate that competent native soil suitable for support of foundations will generally be encountered at depths of between two to four below existing grades. Where loose or unsuitable soil conditions are exposed at foundation subgrade elevations, compaction of the soils to the specifications of structural fill, or overexcavation and replacement with structural fill may be necessary. In our opinion, the soils generated from cuts throughout the site should generally be suitable for use as structural fill. The silty sand soils encountered at the majority of the exploration sites will generally exhibit good soil strength when compacted to structural fill specifications. Recommendations for structural fill placement are discussed in the Site Preparation and Earthwork section of this study. This study has been prepared for the exclusive use of Davis Real Estate Group, and their representatives. No warranty, expressed or implied, is made. This study has been prepared in a manner consistent with the level of care and skill ordinarily exercised by other members of the profession currently practicing under similar conditions in this area. Site Preparation and Earthwork With respect to earthwork, the primary considerations at this site are related to fill placement and compaction, temporary excavatic,ns, suitability of the native soils for use as structural fill, and appropriate erosion control measures. From a geotechnical standpoint, the soils encountered at the test sites are gene,rally suitable for use as structural fill. In our opinion, the site soils anticipated to be exposed during site excavations would exhibit a moderate to high sensitivity to moisture. The soils encountered at the test sites were generally in a moist condition at the time of the exploration (September 2006). Soils encountered during site excavations that are excessively over the optimum moisture content may require moisture conditioning prior to placement and compaction. During periods of dry weather, the on-site soils should generally be suitable for use as structural fill provided the moisture content is at or near the optimum level at the time of placement. If the on-site soils cannot be successfully compacted, the use of an imported soil may be necessary. Imported soil intended for use as strudural fill should consist of a well graded granular soil with a maximum aggregate size of four inclies, and a moisture content that is at or near the optimum level. During wet weather condition::., imported soil intended for use as structural fill should consist of a well graded granular soil with a fines content of five percent or less defined as the percent passing the #200 sieve, based on the minus three-quarter inch fraction. Structural fill is defined as compacted soil placed in foundation, slab-on-grade, and roadway areas. Fills placed to construct permanent slopes and throughout retaining wall and utility trench backfill areas are also considered structural fill. Soils placed in structural areas should be compacted to a relative compaction of 90 percent, based on the maximum dry density as determined by the Modified Proctor Method (ASTM D-1557) and placed in maximum 12 inch lifts. In pavement areas, the upper 12 inches of the structural fill should be compacted to a relative compaction of at least 95 percent. Earth Solutions NW, LLC Davis Real Estate Group September 27, 2006 ES-0625 Page 5 Temporary erosion control measures should include, at a minimum, silt fencing placed along the development perimeter of the co.nstruction site. As appropriate, temporary construction entrances should consist of at least ~ix inches of quarry spalls to help minimize off-site soil tracking and to help provide a stable temporary road base. Mulching of exposed earth surfaces, and other measures for controlling drainage and erosion during construction should be considered, as appropriate. Excavations and Slopes The Federal and state Occupation Safety and Health Administration (OSHA/WISHA) classifies soils in terms of minimum safe slope inclinations. Based on the soil conditions encountered during our fieldwork, the fill and weathered till soils observed in the upper approximately two to four feet at our test sites would be classified by OSHA/WISHA as Type C. Temporary slopes over four feet in height in Type C soils should be sloped at an inclination of 1.5H:1V, or flatter. If appropriate slopes cannot be achieved, temporary shoring should be used to stabilize the excavations. The unweathered glacial till soils encountered below about four feet would be classified by OSHA/WISHA as Type A Temporary slopes over four feet in height in Type A soils should be sloped at an inclination of 0.75H: 1V or flatter, respectively. Permanent slopes should maintain a gradient of 2H:1V, or flatter, and should be planted with an appropriate species of vegetation to enhance stability and to minimize erosion. The geotechnical engineer should observe temporary and permanent slopes to verify that the inclination is appropriate, and to provide additional slope grading recommendations, as necessary. Utility Trench Backfill Based on the subsurface conditions encountered at the test sites, the native soils should be suitable for support of utilities. Organic or highly compressible soils encountered in the trench excavations should not be used for supporting utilities. In general, the native soils observed at the test sites should generally be suitable for use as structural backfill in the utility trench excavations, provided the soil is at or near the optimum moisture content at the time of placement and compaction. Moisture conditioning of the soils may be necessary at some locations prior to use as structural fill. Utility trench backfill should be placed and compacted to the specifications of structural fill provided in this report, or to the applicable specifications of the city or county jurisdictions, as appropriate. Eart'n Solutions NW, UC Davis Real Estate Group September 27, 2006 Pavement Sections ES-0625 Page 6 The performance of site pavements is largely related to the condition of the underlying subgrade. To ensure adequate pavernent performance, the subgrade should be in a firm and unyielding condition when subjected to proofrolling with a loaded dump truck. Structural fill in pavement areas should be compacted to the specifications detailed in the Site Preparation and Earthwork section of this report. It is possible that soft, wet, or otherwise unsuitable subgrade areas may still exist after base grading activities. Areas of unsuitable or yielding subgrade will require remedial measures such as overexcavation and thicker crushed rock or structural fill sections prior to pavement. For relatively lightly loaded pavements subjected to automobiles and occasional truck traffic, the following pavement sections can be considered: • Two inches of asphalt concrete (AC) placed over four inches of crushed rock base (CRB), or; • Two inches of AC placed over three inches of asphalt treated base (ATB). The AC, ATB and CRB materials should conform to WSDOT specifications. Heavier truck-traffic areas generally require thicker pavement sections depending on site usage, pavement life expectancy, and site traffic. The geotechnical engineer should provide appropriate pavement section design recommendations for truck traffic areas and right-of-way improvements, as necessary. Additionally, the City of Renton Road Standards may supersede the recommendations provided in this report. Foundations The proposed townhome structures can be supported on conventional spread and continuous foundations bearing on competent native soils or structural fill, as appropriate. We anticipate that competent native soil suitable for support of foundations will generally be encountered at depths of between two to four feet below existing grades. Where loose or unsuitable soil conditions are exposed at foundation subgrade elevations, compaction of the soils to the specifications of structural fill, or overexcavation and replacement with structural fill may be necessary. Assuming the foundations are suppc:.rted on competent, undisturbed native soils or suitable structural fill, the following parameters should be used for foundation design: Earth Solutions NW, LLC Davis Real Estate Group September 27, 2006 • Allowable Soil Bearing Capacity • Friction • Passive Resistance • Total Settlement • Differential Settlement 3,500 psf 0.40 350 pcf (equivalent fluid) 1 inch 0.5 inches ES-0625 Page 7 For short term wind and seismic loading, a one-third increase in the allowable soil bearing capacity can be assumed. A factor-of-safety of 1.5 has been applied to the friction and passive resistance values. Slab-On-Grade Floors Slab-on-grade floors for the proposed buildings should be supported on a firm and unyielding subgrade consisting of competent native soil or structural fill. Unstable or yielding areas of the 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 five percent or less (percent passing the #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. Retaining Walls Retaining walls should be designed to resist earth pressures and any applicable surcharge loads. For design, the following parameters can be assumed for retaining wall design: • Active Earth Pressure (Yielding Wall) • At-Rest Earth Pressure (Restrained Wall) • Traffic Surcharge (Passenger Vehicles) • Passive Resistance • Coefficient of Friction 35 pcf (equivalent fluid) 50 pcf 70 psf (rectangular distribution) 350 pcf (equivalent fluid) 0.40 Earth Solutions NW, LLC Davis Real Estate Group September 27, 2006 ES-0625 Page 8 Additional surcharge loading from foundations, sloped backfill, or other loading should be included in the retaining wall design, as appropriate. Drainage should be provided behind retaining walls such that hydrostatic pressures do not develop. If drainage is not provided, hydrostatic pressures should be included in the wall design, as appropriate. The geotechnical engineer should review retaining wall designs to verify that appropriate earth pressure values have been incorporated into design, and to provide additional recommendations, as necessary. 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. The upper one foot of the wall backfill can consist of a less permeable (surface seal) soil, if desired. A rigid, perforated drain pipe should be placed along the base of the wall, and connected to an appropriate discharge location. We have provided a typical retaining wall drainage detail on Plate 3 of this report. Drainage Groundwater seepage was not observed in any of the test sites at the time of our fieldwork (September 2006). However, the presence of groundwater seepage should be expected at the dense till contact in the winter and spring months. In the event groundwater seepage is encountered, temporary measures to control seepage and surface water runoff during construction would likely involve interceptor trenches and sumps, as necessary. In our opinion, perimeter drains should be installed at or near the invert of the building footings. A typical footing drain detail is provided on Plate 4 of this report. Rockeries and Modular Block Walls In our opinion, the use of rockeries or modular block walls at this site is feasible from a geotechnical standpoint. Rockeries or modular block walls over four feet in exposed height will require an engineered design. ESNW can provide engineered rockery and modular block wall designs, upon request. At a minimum, ESNW should review the final wall locations and heights, as necessary. Seismic Considerations The 2003 International Building Code specifies several soil profiles that are used as a basis for seismic design of structures. Based on the soil conditions observed at the test sites, Site Class C, from table 1615.1.1, should be used for design. In our opinion, liquefaction susceptibility at this site is low. The relative density of the site soils and the absence of a uniform, shallow groundwater table is the primary basis for this designation. Earth Solutions NW, LLC Davis Real Estate Group September 27, 2006 LIMITATIONS ES-0625 Page 9 The recommendations and conclusions provided in this geotechnical engineering study 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 geotechnical engineering study if variations are encountered. Additional Services ESNW should have an opportunity to review the final design with respect to the geotechnical recommendations provided in this report. ESNW should also be retained to provide testing and consultation services during construction. Earth Solutions f',fW, LLC 111 111 I II 18"Min. . . . . . ..... . . . . . ..... . . . . . . . . . . ..... . . . . . ..... . . . . ' ..... . . . . . ..... 0 o O oo oOO •O G o Do Cl o o oO o .., 0 <> 0 o o? • o o Oo o o 0 ° 0 -0 0 .. OoOoo O O <> oooOOoOO 0 Cl O O 0 OooO O QooO o O 0 0 co Q. o g oo<>0 0 oOooooO • d' 0 ,.. 0 .. o 0 0 o Q o 0 o o Do O 00000 o o oQ O o O Q A o Q o o V 00 O o 0 o O 0 Cle a ., ., 0 o .. o o .. o o O B a 0 0 0 (\. 60 0 ooQ 0 Q~ o "':o o o O o ng O Oo o ,t,"' C.,: 00 000 a oQ o O o o Q_ 0 ° o 0 00-& 0 o O a O Oi:, 0 o Q ,9 ~a 9 o O Oo""o 0° o 0 • • structural Fill NOTES: ' Perforated Drain Pipe (Surround In Drain Rock) • Free Draining Backfill should consist of soil having less than 5 percent fines. Percent passing #4 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" Drain Rock. LEGEND: ~ Surface Seal; Native Soil or other Ll.sJ Low Permeability Material Free Draining Structural Backfill 1 inch Drain Rock SCHEMATIC ONLY -NOT TO SCALE NOT A CONSTRUCTION DRAWING RETAINING WALL DRAINAGE DETAIL Highlands Square Townhomes Renton, Washington Drwn. GLS Oate0912712006 Proj. No. 0625 Checked KRC Date Sept. 2006 Plate 3 Slope . . . . . . ...... . . . . . . . . . . . . . . . . . . . . . . . . ...... . . . . . . . . . . . . . . . . . . -t .. •'• ' :-· 2" (Min.) Perforated Rigid Drain Pipe 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. 1" Drain Rock (Surround with 1" Rock) SCHEMATIC ONLY -NOT OT SCALE NOT A CONSTRUCTION DRAWING FOOTING DRAIN DETAIL Highlands Square Townhomes Renton, Washington Drwn. GLS Date 09/27/2006 Proj. No. 0625 Checked KRC Date Sept. 2006 Plate 4 APPENDIX A SUBSURFACE EXPLORATION ES-0625 The subsurface conditions at the site were explored by excavating a total of four test pits using a trackhoe and operator contracted by ESNW. The approximate test pit locations are illustrated on Plate 2 of this report. The test pit logs are provided in this Appendix. The subsurface exploration was completed in September 2006. Earth So!utions NW, LLC Earth Solutions NWLLc SOIL CLASSIFICATION CHART MAJOR DIVISIONS SYMBOLS GRAPH LETTER TYPICAL DESCRIPTIONS COARSE GRAINED SOILS MORE THAN 50% OF MATERIAL IS LARGER THAN NO. 200 SIEVE SIZE FINE GRAINED SOILS MORE THAN 50% OF MATERIAL IS SMALLER THAN NO. 200 SIEVE SIZE GRAVEL AND GRAVELLY SOILS MORE THAN 50% OF COARSE FRACTION RETAINED ON NO. 4SIEVE SAND AND SANDY SOILS CLEAN GRAVELS (LITTLE OR NO FINES) GRAVELS WITH FINES (APPRECIABLE AMOUNT OFFINES) CLEAN SANDS (LITTLE OR NO FINES) SANDS WITH MORETHAN50% FINES OFCOAASE FRACTION PASSING ON NO. 4' SIE\11; (APPRECIABLE SILTS AND CLAYS SILTS AND CLAYS AMOUNT Of FINES} LIQUID LIMIT LESS THAN 50 LIQUID UMrT GREATER THAN 50 HIGHLY ORGANIC SOILS GW GP GM GC SW SP SM SC ML CL OL MH CH OH PT WEU.-GRACED GRAVElS, GRAVEL· SANO M1XTURES, LITTLE OR NO FINES POORLY.GRADED GRAVELS, GRAVEL· SAND MlxnJRES, LITII.E OR NO FINES SIL TY GRAVELS, GRAVEL • SANO - SILT MDITTJRES CLAYEY GRAVELS, GRAVEL· SANO· CLAY MDITTJRES WELL-GRADED SANDS, GRAVELLY SANOS, LITTI.E OR NO FINES l'OORLY-GAAOEO SANOS, GRAVELLY SANO, LITTLE OR NO FINES SILTY SANDS, SAND -SILT MDITTJRES Cl.AVEY SANDS, SAND-CLAY MIXTURES LNORGANIC SILTSANOVER.Y FINE SANOS, ROCK FLOUR, SIL TY OR CLAYEY FINE SANOS OR CLAYEY SILTS WITH SLIGHT PLASTICITY INORGANIC CLAYS OF LOW TO 1.11:0IIN Pl,ASTICITY, GRAVEU Y ClAYS, SANDY ClAYS. SILTY CLAYS, LEAN CLAYS ORGANIC SILTS ANO ORGANIC SILTY CLAYS OF LOW PLASTICfTY INORGANIC SILTS, MICACEOUS OR DIATOMACEOUS FINE SANO OR SILTY SOILS INOR<JANIC CLAYS OF HIGH PLASTICITY ORGANIC ct.AYS OF ~DIUM TO HIGH PI.ASTlCITY, ORGANIC SILTS PeA.T, HUMUS, SWAMP SOILS WITH HIGH ORGANIC CONTENTS DUAL SYMBOLS are used to indicate borderline soil classifications. The discussion in the text of this report is necessary for a proper understanding of the nature of the material presented in the attached logs. • Earth Solutions NW, LLC TEST PIT NUMBER TP-1 2881 152nd Avenue N.E. PAGE 1 OF 1 Redmond, WA 98052 Telephone: 4252843300 Fax: 4252842855 CLIENT Davis Rea~ Grou~ PROJECT NAME H!Qhland §guare Townhomes PROJECT NUMBER 0625 PROJECT LOCATION Renton, Washi!!Qlon DATc STARTE) 9122106 COMPLETE) 9122106 GROUND ELEVATION 410 ft TcST PIT SIZE EXCAVATION CONTRACTOR Aikins Excavating GROUND WAlcR LEVELS: EXCAVATION IIIETl10D AT TIME OF EXCAVATION LOGGED BY SSR CHECKED BY SSR AT EtlD OF EXCAVATION NOTcS 2· Asohalt Pavement, 2" Gravel Base AFTER EXCAVATION - w Q. ,2 :,: ~ ffi <Ji li: 12' ~ .. q :,: Cl w-IL::; TESTS "' ~g MATERIAL DESCRIPTION a t~ :; <!) 0 SMm Brown silty SAND, medium dense. moist {fill) -trace organics, trace gravel 1.5 408.5 .. ·-. Reddish brown silty SAND, medium dense, moist -- SM .. ---..trace gravel and organics .. --MC= 13.00% .. -.. .. . 3.5 406.5 ~ . : ;: Gray silty SAND with gravel, dense, moist . ---.... • ___§__ MC=8.60% ·. ;. :-. Fines = 16.40% ,, '' -:: .. . ------. '.' •' . •, .. SM .. ·' • -. :· ( '· ·. :, . .... /: ---.-decrease in gravel content ·-.. ·. ~-,, . •.,• c . . . .. . -.. ~ MC= 11.90% .. :_ :-: 10.0 400.0 Test prt terminated at 10.0 feet below existing grade. No groundwater encountered during excavation. Bottom of 1est pit at 10.0 feet • Earth Solutions NW, LLC TEST PIT NUMBER TP-2 2881152nd Avenue N.E. PAGE 1 OF 1 Redmond. WA 98052 Telephone: 4252843300 Fax: 4252842855 CLIENT Oa~s Re~!b'. Grou~ PROJECT NAIE H!ghland Sguare Townhomes PROJECT NUMBER 0625 PROJECT LOCATION Renton Washinaton DA1ESTAR1ED 912V06 COMPLETED 9/22106 GROUND ELEVATION 408~ TEST PIT SIZE EXCAVATION CONTRACTOR Aikins Excavating GROUND WAlER LEVEl.S: EXCAVATION IETHOD AT TIME OF EXCAVATION LOGGED BY SSR CHECKED BY SSR AT END OF EXCAVA1IOH NOTES 2" Asohalt Pavement, 2" Gravel Base AFTER EXCAVATION w "-!.l fir /: ffi oi ::! !!I TESTS ti il:8 MATERIAL DESCRIPTION .... -oi ~---' Cl ti :; C) 0 ·-·· Brown silty SAND with gravel, medium dense, moist ·.· . .' . .. L -... .. .--·· . . -· . .. L --. .. .. , . -. -Oecomes dense . . . .. L . MC= B.30% •.,• ·. ;. · .. SM ·-·· -· L . .... .. ·. :-. -slightly cemented .. •.•• i-L ·. -. ;. :•, .-.. . ... . -·. .. -· .. . . L -MC= 10.70% 7.0 401.0 Test pit tenninated at 7.0 feet below existing grade. No groundwater encountered during exca\lation. Bottom ortest p~ at 7.0 feet. • Earth Solutions NW, LLC TEST PIT NUMBER TP-3 2881 152nd Avenue N.E. PAGE 1 OF 1 Redmood, WA 9B052 Telephone: 4252843300 Fax: 4252842855 CLIENT Davis Rea!!J! Grou~ PROJECTNME Hjghland Sguare Townhomea PROJECT NUMBER 0625 PROJECT LOCATION Renton 1 Washi!:!mon DATE STARTED 9/22/06 COMPI.ET8J 9/22/06 GROUND ELEVATION 402 ft TEST PIT SIZE EXCAVATION CONTRACTOR Aikins Excavating GROllNll WA '!ER LEVELS: EXCAVATION IIIE1HOD AT TIME OF EXCAVATION - LOGGED BY SSR CHECKED BY SSR AT ENO OF EXCAVATION NOTES 2" As~ahlt Pavement 1 2" Gravel Base AFTER EXCAVATION w 11. ~g l': ffi ~ Q wm TESTS (,) "'8 MATERIAL DESCRIPTION t::E ~ i-' 0 i~ :, (!) 0 .. ~· Brown silty SANO wtth gravel, medium dense, moisl .... . . . ... ,· .. .. . -. ·. _-. •, -becomes dense MC=8.00% ·-:· . Fines= 23.00% .. .. SM ... .· '·: . . . . . · _L . : . .' .. -···.· ... .. _.-. .-· .. • MC= 9.90% .. ·_: 7.0 39!5.0 Test pit tenninated at 7.0 feet below existing grade. No groundwater encountel9d durlng excavation. Bottom of test ptt at 7.0 feet. • Earth Solutions NW, LLC TEST PIT NUMBER TP-4 2881 152nd Avenue N.E. PAGE 1 OF t Redmond, WA 98052 Telephone: 4252843300 Fax: 4252842855 CLIENT Davis Rea~ GrouQ PROJECT NAIIE Hjghland Sguare Townhomes PROJECT NUMBER 0625 PROJECT LOCATION Renton 1 Washiogton DATE STARTED 9122/06 COMPL£TED 9122/06 GROUND ELEVATION 405ft TEST PIT SIZE EXCAVATION CONTRACTOR Aikins Excavating GROUND WATER LEVELS: EXCAVATION METllOD AT TIME OF EXCAVATION LOGGEDBY SSR CHECKEDBY SSR AT END OF EXCAVATION NOTES Z' Asohalt Pavement, 2" Gravel Base AFTER EXCAVATION - w I ~a'. oi <..) li:e ~ttl <.i :i: t!) TESTS o..o MATERIAL DESCRIPTION w-0..2 "' ~--' 0 !~ ::i t!) n .. Brown silty SAND with gravel, medium dense, moist •' -. . . . • . •, . SM ·becomes dense MC= 7.10% Fines=. 21.90% .• .. .. .......L .. " .. .. . 6.5 398.5 MC=7.70% Test pit terminated at 6.5 feet below existing grade. No ground\Nater encountered during excavation. Bottom of test ptt at 6.5 feet. APPENDIXB LABORATORY TEST RESULTS ES-0625 Earth Solutions MN, LLC ' .,. • Eanh Solutions NW, LLC GRAIN SIZE DISTRIBUTION 2881152nd Avenue N.E. Redmond, WA 98052 Telephone: (425)284-3300 Fax: (425) 284-2855 CLIENT Davis Rea~ PROJECT NAME Hghlands §guare PROJECT NUMBER ES-625 PROJECT LOCATION Renton U.S. SIEVE OPENING IN INCHES I U.S. SIEVE NUMBERS I HYDROMETER 6 4 3 2 'P.6 1 IA 1123/B 3 4 6 610 1416 2<I 30 40 50 60 1D0140200 100 I I ~ I I I I I I 95 \ 90 \ ~ 85 ·::~ ~ 80 \N ~ 75 " \ 70 f\ ~ 65 ··-· -·--,_ :,: " 60 ~ >-55 ' ., "' w 50 "' ii: \ ,_ 45 \ \ "' w 0 40 .. --"' ~ \ 35 \ ~ 30 \\ 25 \= 20 15 10 5 ···~ 0 100 10 1 0.1 0.01 0.001 GRAIN SIZE IN MILLIMETERS COBBLES GRAVEL I SAND SILT OR CLAY coarse fine I coarse medium I fine Specimen Identification Classification LL PL Pl Cc Cu • Tl'-01 5.0ft. Ught brown silty SAND with gravel, SM Ill Tl'-03 3.0ft. Gray silty SAND, SM 4 Tl'-04 4.0ft. Gray silty SAND with gravel, SM .. Specimen ldenbfication 0100 D60 030 D10 %Gravel %Sand %Silt %Clay • TP-01 5.0ft. 19 1.076 0.197 19.5 64.0 16.4 Ill TP-03 3.0ft. 19 0.532 0.134 13.2 63.8 23.0 4 TP-04 4.0ft. 19 OA7 0.142 16.6 61.5 21.9 ' . 4COPIES REPORT DISTRIBUTION ES-0625 Davis Real Estate Group 1201 Monster Road Southwest, Suite 320 Renton, Washington 98055 Attention: Mr. Johnathan Kurth Earth Solutions NW, LLC