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�./ 4t, Owwon Chevron APR # 6 t3 �� Chevron U.S.A.Products Company ENTAL VICALTl-i 2410 Camino Ramon PERM T/.0�0VISan Ramon,CA 94583 April 13, 1993 Marketing Department Phone 510 842 9500 Ms. Mary Ways San Joaquin County Environmental Health Department P.O. Box 2009 Stockton, CA 95201 Re: Former Chevron Station#9-7780 3246 East Fremont Street, Stockton, CA 95205 Attached work plan for soil and groundwater assessment(GTI, 3117193) Dear Ms. Meays: Enclosed is a work plan dated March 17, 1993 which was prepared by Chevron's consultant, Groundwater Technology, Inc. (GTI), to describe the proposed activities associated with further onsite soil and groundwater investigation. In addition to the soil and groundwater assessment, GTI also describes the onsite activities recommended to investigate the possible remains of a former septic tank. As requested by the San Joaquin County Public Health Services (SJCPHS) in their letter dated January 11, 1993, the following information is provided as a discussion and evaluation of all the historic documentation relating to soil and groundwater contamination at various locations and depths at the subject site: The removal of all underground storage tanks (UST's) occurred January 30, 1987. In their report (Field Sampling At Chevron Service Station # 7780, 212187), Blaine Tech describes the soil sampling and analytical results from beneath each UST. Soil samples collected beneath the three fuel storage tanks were analyzed for TPH and BTEX constituents using modified EPA methods 8015 and 8020. TPH constituents were reported as gas using a method detection limit (MDL) of 1.0 ppm. The MDL in place for the mod. 8020 method varied for each constituent. One soil sample collected beneath the former waste oil UST was analyzed for TPH (reported as waste oil), BTEX, PCB's, and halogenated volatile hydrocarbons. The analysis methods were mod. 8015, mod. 8020, and 8010, respectively. The method detection limit in place for the 8010 analysis is not known. In the fuel UST complex detectable levels of hydrocarbons were measured in soil samples collected from beneath the 5,000 gallon unleaded and 2,000 gallon supreme tanks. Samples collected at depths of 14.5 and 18.0 feet below ground surface (bgs) beneath the unleaded tank ranged from 280 to 1100 ppm TPHGas and 19 to 12 ppm benzene. Beneath the supreme tank soil samples were taken at 14.0 and 18.0 feet bgs. TPHGas concentrations ranged between 5300 to 0.6 ppm and benzene concentrations ranged between 2.0 and 0.043 ppm. No detectable concentrations of hydrocarbons were measured in the soil sample collected at 14.5 feet bgs beneath the 6,000 gallon regular tank.