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r <br /> ( , CaVEPA <br /> mfr► ,.- CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD <br /> CENTRAL VALLEY REGION <br />` 3443 Kautlar Road,Suite A <br /> Sacramento,CA 95927.3099 <br /> Pt ene(916)2$3-3044 Pale WILOn,GOMMar <br /> FAX(M)255-3015 <br /> i <br /> 18 May 1998 <br /> Mr. Ronald Nunan <br /> 651 Gateway Boulevard 4790 <br /> South San Francisco,ICA 94080 <br /> REVIEW OF AMENDED WORKPLAN FOR AN ADDED SURSURIFACE ENVIRONMENTAL <br /> INVESTIGATION,TOWN AND COUNTRY,CHEVRON,13336 HWY 88,LOCKEFORD,sAN <br /> JOAQUIN COUNTY 1 <br /> k In response to your submittal of the 20 Marr:l� 1998 amended workplan for additional investigation at-the <br /> above site, Board and San Joaquin County EnvirorimeMal Heal6staff,aper reviewing this worltplan <br /> and the case Liles,have the following comments. Please incl�rde therri in your site work. <br /> li <br /> Page 2,paaigraphs L and 2 of the amended workplan state that a borchole,will be advanced to 40 feet <br /> below ground surface(Ft bgs),and extended to Lrirei►ter depths,it obvious contunination is still evident <br /> during the drilling and sampling process. The borchole will be s�uiipled From Zp to 4t] t1 bis In <br /> addition to ouilecting sail samples at S R intervals;samples Witt be collected at lithologic soil changes or <br /> where obvious staining is noted. Therefore,amin inium of five soil,samples will be Collected and <br /> unalytied for total petroleum hydrocarbons as gai Mune(TPF[-g),benzerve tolatene,cthylbenzene,and <br /> xylene(13'L VX)and methyl tertiary-butyfether(MTI38)'constituents and-Toxicity Ghiracteristle. <br /> r Leaching Procedure(1'C`LP) leachability. The goail is to establish a decreasing trend in benzene I <br /> concentrations with depth so that the deepest sample confirms anon-aetectabie concentration, <br /> f 1n the 15 July 1497 Workplan far a 8absurfave Grtvir'onmertfal 10esti rfrprl, Frank Gbldrnan, the <br /> consultant, states that the regional ground water depth.is 90 to 120 ft bgs..., Information from nearby situs <br /> shows ground wutcr is etwounterecl at opProxim3lely 75'11 bgs;so the depth to groundwater at this site is <br /> possibly 75 ft bgs. <br /> The goal of this investigation is to detcMi4w the vertical extent of contamination for all constituents in <br /> soil aad to verify the depth of ground water. if ground water is ixnpucted the lateral and vertical extent <br /> of contamination must be determined at this site', therefore:,the workplArl is approved, but t1w following <br /> changes need to be implemented during the inve'stigation. In additiort to-collecting soil samples at <br /> 40 ft bgs,as stated in the workplan,the collectiorr1and analysis of soil surnples Far TPI-1-g,BTEX, <br /> ` MTBE?and the othor oxygenates using LPA Method 8260 must continue as long as these contaniinarlts <br /> are detcete;d. if no contsumination is eleteuted at 40 ft bgs, nail sai.bples need to be ao11i�4ted and analyzed <br /> for petroleum constituents for the next to ft to veil'ify that contaminated soil is not present.;'This <br /> sampling is needed, because contamination meanders through the soil rather than being continuous like a <br /> plume in ground water. If any contamination is-40ccted between 40 to 50 ft bgs,then the boring.must <br /> R<!CyClad pr�rr �l yr ni�rifoa lr In p�reras'rxxl rahrFnre';llxr qunlliy of Califixrefa:f ru6er r�srxr[wauncf <br /> ewuwd their proper ul amnaR ural eff]el4iu iavj�w the herwal of pm-vj7!ttNi m1jP e'Feneralloru. <br /> Z! d Wd ST:Z 866T'81 'AUW STM SSS 916 :�81 HDOl'16f)J WG&iI <br /> L <br />