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41 <br /> Chevron <br /> ,17 'FloCr�.� <br /> atfron <br /> Ch <br /> F <br /> t7 <br /> Chevron Products Company <br /> August 12, 1997 6001 Bollinger Canyon Road <br /> Building L <br /> San Ramon,CA 94583 <br /> P.O.Box 6004 <br /> Mr.Harlin Knoil San Ramon,CA 94583-0904 <br /> San Joaquin County Public Health Services Marketing—Sales West <br /> 304 E. Weber Ave., Third Floor Phone 510 842-9500 <br /> Stockton, CA 95102 <br /> Re: Chevron Station 4 9-2033, 508 W. Charter WU, Stockton, CA <br /> Attached:UST Closure and Limited Overexcavation Sampling Report (Touchstone, 8/7/97) <br /> Attached!Uniform Hazardous Waste Manifests(#'s. 96430826--95784406,407,411,95894474,84) <br /> Dear Mr. Knoll: <br /> Please find attacMd a report dated August 7, 1997, that was prepared by Chevron's consultant, <br /> Touchstone Devel6pnients(Touchstone),to describe the field activities, sampling procedures and results <br /> that were associated with the removal of service station facilities during September through November, <br /> 1996. <br /> On September 6, 1f996,all liquid UST contents and rinsate were removed and properly disposed of. The <br /> removal of all subsurface equipment was performed on September 9, 1996. Touchstone was onsite to <br /> perform couiptian6e soil sampling beneath the removed UST's, product piping, hoists. and a tube bay <br /> floor sump. All saImpling was witnessed by Mr. Eric Trevena, of your agency. Copies of the hazardous <br /> waste manifests documenting the proper disposal of subsurface equipment and liquids removed from the <br /> subject site are allached for your reference. <br /> The analytical results obtained from compliance soil sampling revealed the presence of motor fuel <br /> contamination beneath the fuel UST complex,dispenser islands, and hydraulic hoist areas. Based on these <br /> information, soil remediation by overexcavation was performed according to Touchstone's Corrective <br /> Action Plan dated August 30. 1996. The results of soil sampling at the limits of the overexcavation <br /> indicated residual levels of TPHGas up to 160 ppm in one location (sample OXB2 @ 10'). The residual <br /> detections of benzbiie ranged between non-detect and 0.07 ppm. The highest concentration(27 ppm)of <br /> residual MTBE was measured at 19' from beneath the former fuel UST complex. The combined results of <br /> all remedial excavafioii sampling serve to define the full extent of TPHGas/BTEX contamination in soil. <br /> The full extent of MTBE contamination in soil appears to be defined except, for vertically within the <br /> former fuel UST coinplex, It is felt that the overexcavation activities were successful in removing all <br /> significant soured of groundwater contamination. <br /> 1� <br /> Touchstone's report also discusses the sampling and onsite remediation of soil stockpiles that were <br /> generated during 0 verexcavatidn activities. With the exception of approximately 150 cubic yards, all soil <br /> stockpiled at the subject site was successfully reinediated and reused as excavation backfill material. The <br /> remaining 150 cubic yards was transported to BF1 Vasco Road Landfill in Livermore., California for <br /> proper disposal. <br /> IG <br /> I it <br /> 4 <br />