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FROM : CVRWQCB TEL: 916 255 3015 MP-. 18. 1998 2:37 PM P 2 <br /> ` s CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD Cal/EPA <br /> CENTRAL VALLEY REGION <br /> 3443 Routier Road,Suite A <br /> Sacramento,CA 95627-3096 <br /> Phone(916)255.3000 <br /> PAX(916)255-3015 retewiluaa,(1ovGnzor <br /> 18 May 1998 <br /> r <br /> Mr. Ronald Nunan <br /> 651 Gateway Boulevard#790 <br /> South San Francisco,CA 94080 <br /> } <br /> + REVIEW OF AMENDED WORKPLAN FOR AN ADDED SUBSURFACE ENVIRONMENTAL <br /> INVESTIGATION,TOWN AND COUNTRY C'1 . VRON, 14336 IIWY 88,LOC.K1CFUlE�,SAN <br /> JOAQUIN COUNTY. � <br /> a In response to your submittal of the 20 March 1998 amended workplan for additional investigation at the <br /> above site,Board and.San Joaquin County environmental Health staff,after reviewing this workplan <br /> and the case files,have the following commcnts. Please include them in your site work. �� I <br /> J <br /> Page 2,paragraphs I and 2 of the amended workplawstate that a borehole will be advanced to"40 feet <br /> below ground surface(fl bgs),and extended to greater depths,if obvious contamination is still evident, <br /> during the drilling and sampling process. The borehole will he gambled.from 20 to 40 fl bgs. In <br /> addition to collecting soil samples~at 5 ft intervals,samples will be collected at litliologic soil changes or <br /> where obvious staining is noted. Therefore,'a minimurn of five soil"samples will be collected and <br /> analyzed for total petroleum hydrocarbons as gasoline(1"ISN-g}, benzene,toluene, e1hylbenzene,and <br /> Xylene(BTLX)and methyl tertiary-butyl ether(MTBB)constituents and'Toxicity Characteristic <br /> Leaching Procedure(TCLP)leachability. The goal is,to establish a in; trend in heniene <br /> 'i concentrations with depth so that the deepest sample confirms a non=detectable concentration. <br /> k In the 15 July 3 997 Workplan for a Subsurface Environmental Investigation, Frank Goldman,the <br /> consultant,states that the regional ground water dept is 90<tn:120 ft bgs. Information from nearby sites <br /> 1 shows ground water is encountered at approximately 75 ft bgs; so the depth to ground water at this site is <br /> possibly 75 A bgs. F� 100 <br /> The goal of this investigation is to determine the veMi'cal extent of contamination for all constituents in <br /> soil and to verify the depth of ground water. if ground water is impacted,the lateral and vertical extent <br /> c of contamination roust be determined at this site. Thercforc,the workplan is approved,but the following <br /> I changes need to be implemented during the investigation. In addition to'!collecting soil samples at <br /> 40 ft bgs,as stated in the workplan,the collection and analysis of soil samples for TP14-g,BTFX, <br /> MTBE and the other oxygenates using EPA Method 8260 must continue as long as these contaminants <br /> are detected. If no contamination is detected at 40 R bgs,soil samples need to be collected and analyzed <br /> for petroleum constituents for the next 0 ft overify that contaminated soil isnot present. This <br /> sampling is needed,because contamination meanders-4hroubh the soil rather than being continuous like a <br /> plume in ground water. If any contamination is detected between 40`.to 50 ft bgs,then the boring must <br /> Rrcycled Paper Umo-mission 1t ivinw-wrw and enhaacr the qualify of C:al(fornla r wtwft+r msowrvv.and <br /> rnwu,e+helrl►rowr allocation and r(ffclrnl xar fol•Me heneik of prrarnl and f shirr gown inns. <br /> Aj <br />