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iProject Quarterly Update Report December 10, 1992 Southland Store No 20680, 9110 Thornton Road, Stockton, CA 3 22 Groundwater Sampling and Analyses Laboratory analytical data for samples collected from groundwater monitoring wells MWA and MW-18 during the previous quarterly sampling on June 29, 1992, indicated total petroleum hydrocarbon-as-gasoline (TPH-G) concentrations of 48 ppb and 19 ppb, respectively Groundwater monitoring wells MWA and MW-18 were re-sampled on July 30, 1992, to confirm the presence of dissolved hydrocarbons and to evaluate the possibility of a sampling error during sample collection on June 29, 1992 A water well bailer was lost down monitoring well MW-9 during sampling performed in March 1992 The bailer was retrieved and the monitoring well was sampled on July 30, 1992 Monitoring wells MW-13, MW-15ABC, MW-16, MW-17ABC, and MW-18 through MW-20 were sampled on September 30, 1992 The status of monitoring wells not sampled on September 30, 1992, is summarized in Table 2 Samples were collected according to Groundwater Technology's Standard Operating Procedures (SOPs), copies of which are included in Appendix A Groundwater sampling was conducted by first purging water from each well using a polyvinyl chloride (PVC) bailer Each well was purged by hand I• bailing, removing at least 4 well volumes of water, or purged until dry The groundwater was then allowed to recover to at least 80 percent of the original static water level before sampling The ' groundwater samples were collected using an Environmental Protection Agency (EPA)-approved Teflon® sampler All samples were collected in laboratory-supplied containers, preserved, labeled, ' and stored on ice Samples were transported under chain-of-custody protocol to a California- certified laboratory, GTEL Environmental Laboratories, Inc (GTEL) in Concord, California Each sample was analyzed for BTEX and TPH-G using modified EPA Methods 5030/8020/8015 The analytical report for the groundwater sample collected from monitoring well MWA 8 on July 30, 1992, indicated that TPH-G and benzene concentrations were below MDLs Analyses of groundwater samples collected from monitoring wells MW-1 and MW-9 on July 30, 1992, reported TPH-G concentrations of 18 parts per billion (ppb) and 60 ppb, respectively Benzene was detected only in the groundwater sample collected from well MW-9 at a concentration of 0 5 ppb Analyses of the samples collected from groundwater monitoring wells MWA 3, MW-115ABC, MW-16, MWA 7ABC, and MWA 8 through MW-20 on September 30, 1992, verified that BTEX and TPH-G concentrations were below MDLs in all samples I IR1211A1 RH GROUNDWATER TECHNOLOGY, INC