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qVft DAMES & MOORE A PROFESSIONAL LIMITED PARTNERSHIP <br /> 1320 EAST SHAW AVENUE, SUITE 110, FRESNO, CALIFORNIA 93710,(209)222-7892 <br /> FAX(209)222-1937 <br /> SES'27 '89 H.C.H. iAl-HEALii' <br /> ',RVICRq <br /> September 15, 1989 <br /> Chevron U.S.A. Project No. 16000--165-03 <br /> P.O. Box 5004 <br /> San Ramon, California 95001 <br /> Attention: John Randall <br /> i <br /> RE: Proposed Remedial Action Plan <br /> Chevron Service Station #961/5 <br /> Highway 99 and Morada Lane 5 <br /> Stockton, California <br /> INTRODUCTION <br /> In accordance with your request, we have developed a proposed remedial <br /> action plan for removal of gasoline contaminated soil at the above-referenced <br /> subject property. The contaminated soils were disclosed during an investigation <br /> requested ty Chevron U.S.A. which .was conducted at the subject property by Dames <br /> & Moore. A report prepared for'- Chev'ron U.S.A. dated August 31., 1989 summarized <br /> the details of Dames & Moore's findings. <br /> PROJECT OVERVIEW <br /> In general, contamination of subsoiis-in the vicinity of previous dispenser <br /> island locations was observed to exist as disclosed by soil sampling and chemical <br /> analysis conducted at the time of ground water monitor..well installations at the <br /> subject property. <br /> The contamination noted in subsoils suggested residual gasoline <br /> contamination to an approximate depth of 20 feet below the existing grade at the <br /> previous dispenser island location which were drilled and sampled. The <br /> interpreted residual gasoline contamination ranged in concentration from 217.0 to <br /> 8228.34 parts per million total petroleum hydrocarbons, with-benzene <br /> concentrations in soil ranging from 1.41 to 23.18 parts per million in the <br /> surface grade to approximately 20 foot below grade depths at the locations <br /> drilled. <br /> Low levels of benzene, toluene, ethylbenzene, and xylenes (less than 1.0 <br /> part per million) were also observed in samples obtained from greater depths in <br /> the soil borings. Those concentrations of less than 1.0 part per million of those <br /> species were interpreted by Dames & Moore to be suggestive of vapor phase <br /> diffusion of volatilizing petroleum hydrocarbons from the noted residual <br /> contamination. <br /> OFFICES WORLDWIDE <br />