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<br /> {,1.28 April 1997 Y '. i.-_ ,,11, f R'1• ,.f
<br /> A6&,Project'No 6'0232
<br /> F Page 4 of 9 ;
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<br /> oil
<br /> Jurassic complex of igneous and inetamorpluc basement rock
<br /> 7: GROUND WATER DEPTH AN 'FLOW DIRECTION "" x
<br /> Review of Lines'of Equalb'th`of Water-Wells.Fall 1993 published by the"San Joaqurn'CountyS< r i.
<br /> Flood Control'and Water:Consezvation District suggests that the wer-'table surfa6e Beneath the site
<br /> I 'occurs at a depth of approximately 15 feet bsg'. The uppermost ground.water flows in a unconfined I ;51a;
<br /> f av0r.`With increasing dep'k the aquifer becomes semi-confined'
<br /> ',,due,ta the`presence of f ne-grimed
<br /> F 4 ' •
<br /> 5edimenfs. i
<br /> i.
<br /> -
<br /> ,, ;< Base _ 4 _
<br /> d-upon.informd6ji obtained-from� the:PHS,EHD; the prevailing ground'water flow.direct on-fin
<br /> - the area of-the 'site is generally toward the north ,However, ,groundwater mon.iforin& events
<br /> performed'at the site iri July and August 1996 'that aground water flow direction is
<br /> 'ei n rally ;
<br /> `toward the south.
<br /> ADDITIONAL SUBSURFACE INVESTIGATION '
<br /> 3.I. DRILLING AND SA1\ZPLING'' ..
<br /> 4n16•July I996 . .- ; , . ,. . `- , . • ,� - ' - � ; • 4.
<br /> e
<br /> on „soil'boring (MW-4) was adva.nced at the site to a depth ofapproximately 25.
<br /> feet b_sg utilizing'a CME-75 truck mounted'drill-rig equipped!with'eight-inch'diameter,'hollow stem
<br /> au ers Cuttings and `roseate enerated'durin drillin activities.were laced in ro erl` �ylabeled
<br /> g . Ig,l , g g' g p ; P. .P. ..Y `."':..
<br /> ' D:O:T. model 17H 55-gallon'. .!dhims'and were,stored on site �n an.area lacking.pu�lic access .The
<br /> location'of soil boring M'W=4 is depicted"oi Figure'-2.
<br /> Discrete soil samP les were collected at-five-fobfintervals be"'' ata de th.,of'S feet'bs
<br /> ,
<br /> g g• P g, utilizing
<br /> a Califorl id-split-spoon saliipler and:brass'sle'eves. The sampler'wa's driven by dropping'a 140-pound
<br /> r r
<br /> Iweight from a.lieight of 30 inches:The number'of blows required,to'advan' each 6= nch;leilgth of
<br /> the sampler.;(blovv counts) was recorded on boring Iogs by-an AGE-staffgeologist(Appendix B)
<br /> a
<br /> }.
<br /> Upon-sample retrieval,.•the,middlebrass,sleeve was removed from the.sampler Both ends of the r
<br /> r
<br /> sleeve were`cover-ed`With-TeIIon-sheets;capped'and sealed;with tape:.Each.sample was labeled with ;
<br /> E
<br /> the.f boring location,.;depth tame `date' and sampler's'in'itials. The samples were;placed in
<br /> If r` a chilled container and•transported,under chain of-'custody' toa.Castle''Analytical, Laboratory, a
<br /> California"state-certified';•laboratory.•.Selected soil.'samples -were 'analyzed for total-,petroleum.
<br /> hydrocarbons quantified as gasoline and diesel (TPH=g and TPH-d),''volatile aromatics (BTE&X) '
<br /> with'methyl-tertiary;butyl'ether(MTBE)in accordancewith'EPA Methods 8015M, $0.15M:and'8020.
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