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Site History Jackpot Food Mart, 1434 W Yosemite Ave , Manteca, CA Time Oil Property No 04-167 groundwater in each well Analyses indicated the presence of 0 55 ppb xylenes in the sample collected from W3, however, no contaminants were detected in the remaining wells After the installation of the wells, a vapor extraction pilot test was performed on W1, W2, and W4 to evaluate the feasibility of in-situ remediation by vapor extraction The results of the study indicated that soil vapors can be easily extracted from the existing wells and that this technology appears appropriate for site remediation Based on the results of the site assessment and previous investigations, it appears that the extent of gasoline-impacted foil is well defined and remains limited to the area of the pump islands Although trace concentrations of xylenes were present in the groundwater sample collected from W4, the levels indicated were far below California's primary drinking water quality standards (1750 ppb for xylenes) A copy of Canonie Environmental's "Site Assessment Report, Underground Storage Tank Site, Time Oil Co , Jackpot Food Mart, Manteca, California" was forwarded to the PHS/EHD and CRWQCB on May 26, 1993. In their reply dated June 24, 1994, the PHS/EHD requested that additional borings be placed to determine the extent . of hydrocarbon-impacted soils and that the groundwater monitoring wells on the subject site be re-sampled Additional Site Investigation - December 1993 Based on data collected during a preliminary investigation (Canonie, April 1993) , additional site activities were conducted to further define the extent of hydrocarbon-impacted soils associated with the former tanks, and to determine if groundwater beneath the site had been impacted Prior to the implementation of field activities, SEACOR's workplan dated October 12, 1993 was submitted for agengcy review Verbal authorization to proceed with the proposed work was received from the PHS/EHD on November 27, 1993 On December 2, 1993, a drill rig was utilized to advance 4 soil borings in the vicinity of the former tanks During field activities, soils were found to consist of fine to medium sands to a depth of approximately 15 feet This strata was underlain by clay Because the previous investigation indicated that the clay unit may be acting as an aquitard, all borings were discontinued at a depth of 16 5 feet below ground surface to prevent possible impacts to groundwater beneath the site Soil samples collected from depths of 10 5 to 11 feet and 15 5 to 16 feet in each boring were submitted to an analytical laboratory and analyzed for gasoline and its constituents Analyses did not indicate hydrocarbons in any of the samples submitted for analysis • On December 2, 1993, the existing groundwater wells were developed and sampled Prior to purging, an easterly gradient was determined by measuring the depth to groundwater in each well (approximately 16 feet below ground surface) Analyses 3