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LOW, J <br /> Chevron <br /> !� Chevron <br /> Chevron U.S.A.Products Company <br /> 2410 Camino Ramon <br /> March 21, 1994 San Ramon,CA 94583 <br /> P.O.Box 5004 <br /> San Ramon,CA 94583-0804 <br /> Ms. Mary Meays <br /> Marketing Department San Joaquin County Environmental Health Phone 510 eaz 9500 <br /> P.O. Box 2009 <br /> Stockton, CA 95201 <br /> yh <br /> Re: Former Chevron Station#9-1918.45 Fast Harding Way, Stockton, CA <br /> Attached Additional Assessment Report(GTI,3/14/94) N) <br /> Dear Ms. Meays: N <br /> o <br /> Attached is a report dated March 14, 1994, which was prepared by Chevron's consultant, = <br /> Groundwater Technology Inc. (GTI), to describe the installation and sampling of three soil borings <br /> and two groundwater monitoring wells at the subject site. The attached report also describes <br /> results of groundwater sampling and monitoring performed on January 26, 1994. <br /> The intent of soil borings SB-1, SB-2, and SB-3 was to evaluate the effectiveness of soil <br /> remediation in the vicinity of the former underground storage tank complex. Soil analytical results <br /> from all three borings indicate that benzene has been remediated below detection limits at these <br /> locations. Residual levels of TPHGas measured at SB-2 and SB-3 revealed less volatile <br /> hydrocarbon constituents not completely remediated by vapor extraction wells V-4 and V-3, <br /> respectively. <br /> Two groundwater monitoring wells were installed during this investigation. Well MW-2R was <br /> drilled as a replacement well for MW-2, which has been dry since June, 1990. Monitoring well <br /> MW-14 was installed to define the downgradient extent of the dissolved hydrocarbon plume. No <br /> detectable concentrations of hydrocarbons were measured in soil samples collected from these two <br /> wells. <br /> During the drilling of MW-2R, an unknown underground storage tank was discovered. This tank <br /> was removed and soil samples were collected on March 18, 1993. The pending analytical results <br /> will be evaluated as part of the ongoing site investigation. <br /> GTI performed groundwater monitoring at the subject site on January 26, 1994. The measured <br /> direction of groundwater flow was toward the east-northeast. Groundwater samples were collected <br /> from seven of the fourteen site-related wells. Detectable concentrations of dissolved hydrocarbons <br /> were measured in wells MW-11, MW-13, and MW-14. Detections of dissolved hydrocarbons at <br /> wells MW-11 and MW-13 were consistent with previous measurements however, the detection at <br /> MW-14 represents a single sampling event and will be verified next quarter. <br />