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18 February 1997 AGE-NC Project No 95-0104 ' Page 3 of 22 ' 2 4 REGIONAL AND LOCAL GROUND WATER A map titled I ares of EEqual Depth of Water Wells-Fall 1993, published by the San Joaquin County ' Flood Control and Water Conservation District shows that the water-table surface beneath the site occurs between 70 and 80 feet bsg The uppermost ground water flows in an unconfined aquifer With depth, the aquifer becomes semi-confined due to the presence of interbedded layers of fine- grained sediments Review of local ground water data collected from quarterly ground water monitoring events at the ' site suggests that the local ground water flow direction fluctuates seasonally between the northeast and southeast Ground water is presently at approximately 70 feet bsg and has a northeastern flow direction Previous ground water monitoring data suggests that ground water depth has fluctuated ' between 60 and 90 feet bsg at the site ' 2 5 DOMES"I IC AND MUNICIPAL WELL SURVEY One domestic water well is Iocated approxirriately one hundred-fifty to two hundred feet south (downgradient) of the former UST area Ground water samples collected from the domestic well in April 1993 contained substantial nalogenated volatile organic compounds As d result, use of the ' domestic water well was discontinued in April 1993 In July 1996, the well was sealed and capped under a San loaquin County permit ' Drinking water near the site is currently supplied by the City of Stockton municipal wells California Water Service Company (Cal Water) maintains a municipal well and tank approximately 2,000 feet north of the site between East Waterloo Road and Clierokce Road No other municipal wells ' maintained by the City of Stockton or Cal Water are located within 2,000 feet of the tate Fir st encountered ground water is not used for drinking or irrigation ' 30 SOII. VAPOR EXTRACTION PILOT TEST ' 3 1 SOIL VAPOR EXTRACTION SYSTEM On 6 March 1995, an 8-hour soil vapor extraction test (pilot test) was conducted This pilot test was performed to pi ovide vapor extraction data for feasibility analysis of the remediation method and for proper design of the remediation system ' The test was conducted using a vapor extraction system (VES), VACLEEN 1000G, manufactured by Environmental Techniques The VES consists of a positive-displacement blower, driven by an Iinternal combustion.(IC) engine The inlet of the VES was connected to soil vapor extraction (SVE)