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HORIZON ENVIRONMEVAL .INC. <br /> Specialists in Site Assessment,Remedial Testing,Design and Operation <br /> 53tA��` cf, E;�ilt' <br /> March 23, 1998 <br /> Mr. Jeffery Wong <br /> San Joaquin County Environmental Health Department <br /> 304 East Weber Street, Third Floor <br /> P.O. Box 388 <br /> Stockton, California 95201 <br /> Subject: Transmittal of PAR and Closure Request <br /> Former Discovery Chevrolet, 1615 11th Street, Tracy, California. <br /> Mr. Wong: <br /> At the request of our client, Horizon Environmental Inc. (Horizon) is transmitting to you the <br /> Problem Assessment Report (PAR) for the above referenced-site. In addition, on behalf of <br /> our client, we request that this site be considered a low risk site and as such granted closure. <br /> Conclusions in the report prepared for the State Water Quality Control Board (SWQCB) by <br /> the Lawrence Livermore National Laboratory (LLNL) entitled Recommendations to <br /> Drove the Cleanup Process for California's Leaking Undereround Fuel Tanks, indicated <br /> that intrinsic bioremediation processes may be degrading hydrocarbons sufficiently to limit <br /> the length migration potential of petroleum hydrocarbons in subsurface soils and <br /> groundwater. In our professional opinion, these processes are occurring at this site. <br /> Data collected to date has indicated that the petroleum hydrocarbons in soil are limited to the <br /> area around the former gasoline UST cavity at depths greater than 5 feet below surface grade <br /> (bsg). Groundwater data collected indicates that the petroleum hydrocarbons in groundwater <br /> are naturally attenuating with time and have not migrated over 100 feet downgradient of the <br /> former source area. In addition, data collected indicates that MtBE and the other fuel <br /> oxygenates are not present at this site at concentrations that warrant further investigation. <br /> Mass balance data indicates that less than 40 gallons of gasoline are present in the <br /> subsurface. <br /> We recommend this site be closed based on the following: <br /> • The source of the petroleum hydrocarbon discharge (the gasoline USTs and product line) <br /> have been removed and the petroleum hydrocarbons in soil beneath this site are limited <br /> to a relatively small area around the former gasoline cavity at depths greater than 5 feet <br /> below surface grade. <br /> 5011 Golden Foothill Parkway,Suite 7 • EI Dorado Hills,CA 95762 • (916)939-2170 • FAX(916)939-2172 <br /> P.O.Box 5283 • Bakersfield,CA 93388 • (805)589-8389 • FAX(805)589-1456 <br />