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FROM CVRWQCB TEL: 916 255 3015 OCT. 9. 1998 12:15 PM P 5 <br /> 13336 East Highway 88 -3, <br /> 1"keford-0 San Joaquin County RAFT I October 1998 <br /> and an oder was noted on the boring log at 34 feet'bgs. Sail sartjples collected from boring B7, between <br /> and 60 feet bgs++c�antailtlsd eslavated concentrations of TPHg (to 45 feet bgs); and BTEC constituents <br /> (to 60 feet ). Below 70 feet bgs, <br /> sot!samples were analyzed for TCLP only. <br /> The elevated concentrations of TpHS, and BTEC constituents in the groundwatersRmplc warrant an <br /> inv"68010n to determine the lateral and vertical extent of'jroundIwater contamination. The groundwater <br /> investigationmust include drilling three soil borings to groundwater, and collecting discrete soil samples <br /> from the capillary fringe, and saturated zone in each boreiiote. Groundwater samples must be collected <br /> from eat borehole using a technology that will provide Samples repmesentative of chemical and <br /> hvctrogeologic conditions. This may be completed using the le <br /> . P g S m lProlteet or core Q.� <br /> arable tech <br /> a ldtesr Rtive to ruing an effective sampling technologytri rovide representative p itc�lcr `- <br /> .a ... —AvertP g � P p groundwater sarttlilt* <br /> cacti b ; <br /> borehole to a groundwater monitoring well,sand begin a groundwater samp.t:nnr -- <br /> in0rtitvring program. Soil and groundwater saris les must be`anal ze - <br /> P y d for `IPHg, IrJ"i"EX and the <br /> :*to�'�CL.P anayysis will be requited For these s} Iek. The oxygenate analysis is n; <br /> because tertiary-Butyl Alcohol (TBA) was detected at 96 RA-S iri the sail sample collected from boring <br /> B7 at 49 to SO feet bgs. <br /> Based on residual contaminant mass calculations provided Geooly, <br /> (4,4t�gallefns)of TPH and$9S..lello ! � � , appmximatcly 67.812-kilograms <br /> if grams(S8 gallons)of benzerie are estimated to remain in the soil at <br /> the site, If the requested groundwater samples ate non-detect for all contaminants, a fate and transport <br />' model mast be ruts to demonstrate that the residual conform 'tient mass will not adversely impact <br /> Tr ever, the groundwater samples are;irrtpactc+d by pettoleutn hydrocarbons, <br /> �iudiit+�c�rtW work mayberequired, <br /> The single groundwater grab sample collected from soil boring B7 on 1 July 1998 contained olcvated <br /> concentrations of TPHS, benzene and toluene. Mr. Goldman '!of CmGSOIV attributed the elovated <br /> concentrations of petroleum oonstituents to cross-contamination of!the bailer during its descent down the <br /> center of the augers, to leaching of contaminants to groundwater through <br /> tn vnewyArpt.ne^ .nf4►►"2lFiA.np,T..wy. ..�'s4.... L i k <br /> .e�:nit be,c6nfirt6d-or denied using the available data. <br /> Based on elevated concentrations of TFI , =�.:�_. M ;;::; r►iv viu�uvrn�u anrupirc, l am <br /> requ ating that three soil borings be. drilled to groundwater; Soil samples ane to be collected rm-e =' <br /> capillary fringe and smursted zone,and groundwater samples arc 10 ba collected from each boring using <br /> 4w.- hrrology that will provide samples representative of chemicall and hydrogcc4 <br /> site.Until groundwater conditions are assessed at tate site,site closure cannot be,c;onsidomd. <br />