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MHT.CM.1tftl`y c- )J13 M-"'II`Elr+. HUMIN IYu.IIJ I'._-V11 <br /> AUG,;:05' 971TUE) 16:45 UNOCAL C` ;IORTH RB TEI,c510 177 <br /> • June 13, 1997 <br /> page 2 <br /> gasoline and 12 pounds ofbenzene have been removed horn the sal <br /> by a sores vapor w action(SVE) system. <br /> • The groundwater plume is small and stable in size. No metbyi-tart <br /> butyl edie r(MtBE) has been detxted in any g oundwaw sample. No <br /> sepwatc�phaw hydrocarbon (SPM has ever lawn obser4ad in any weD. <br /> ?'he dosex public water wp*well is IoWwl appnmimately 800 to <br /> 1,000 fiat cinsmp-a cm ofthe gir- <br /> • Residual hydrooubeans in the so=rts at daptbr,of grmter than 26 feet <br /> below ground surface(bSs)aro unlikely to pew a vapor migration <br /> threat to the surface. <br /> Unocal has submitted several requoM tar me closure to Sen Joaquin County . <br /> Envh meatW Health Division(SJCE D), The lamest request from Unocal dead <br /> February 7, 1397 is presented ss Attachment 13 along with SIMM's responsa In each <br /> case:� SJCE M has requested additional data prior to considering site closure. <br /> BACKGROUND <br /> Site DcK ption (i.x., Lb.� The farmer Unocal Service Station 2259 was loco" at <br /> 1665 Pack Avem,+e, Stoc�-ton, Cautbrwa(Am;rinrir.irt C, Flom C-1). The swvtce <br /> stolon originally included two dispenser islands, two$asofte USTs, and one waste oil <br /> tank Mwurc C-2). The site was demolished in February 1968. Alf product dionbution <br /> Piping and U'STs were removed_ The site now exists as a vw&nt lot, <br /> GeolvgicfHydrogeoleoi Setting(i.f The site is underlain by primarily+s=ilt mid c* <br /> to the depth pcplvred (60feet). Geologic an%-sccdom are presented on FiSwe C-s, <br /> Data from site mordto:rkrg ovell.4 have defined a general groundwater flow to the etm.4 and <br /> northeast. The latest poteiitiiomehic rnap(February 14, 1997)is presented as <br /> Figure C-4. Depth to grotmdwater was approximately 30 feet in 1958 when site <br /> assessment was initiated. Groundwater levels subw pently deal'uied ranching depths <br /> BMW than 30 f6q in ]990 through 1902, Severe! vmUs wen dry. As of 1996 m <br /> Present, groundwater levck We returned to initial depths of appy dmataly 3Q to 35 feet <br /> bgs. <br /> Wster-Supply Wells (x.f,). A well survey performed by AppUM Cyw s treport <br /> . dated Dem"ber 12, 1990)found that troch watersupply weA9 are located within 1 m9e <br /> nfther site(Atchrnern D). The ffr)gowbg is mkaa fr,om the App>;e d Chosywems report; <br /> "Ground-water resaumes within the Easnrn Sar►Joaquin County <br /> Basin are iaie flWvoly dev):10ped fur iir:gatfort, dove Wc, industrial, <br /> rmmicipal. and stock use. The;locations of municipal water supply <br /> wells near the site ope=ra bod by Cvlifornis Water Service ofStodmn. <br /> 91�rddulleyiSlLBoe7C <br />