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x164 Gold( I ! Suite 200 DeftRancho Cordovh CSA 9567{}6021 ' Environmental U S A Consultants,Inc 9161638 2086 r-AX 9IUIV108 UJVJ February 22, 2000 1 ' Mr Darin L Rouse ExxonMobil Corporation 2300 Clayton Road, Suite 1250 ' Concord, California 94520 Subject Quarterly Ground Water Monitoring Report Fourth Quarter 1999 Former Exxon Service Station No 7-3708 2705 Country Club Boulevard Stockton, California Delta Project No D093-809 ' Dear Mr Rouse Delta Environmental Consultants, Inc (Delta) has been authorized by Exxon Company, U S A (Exxon) to prepare a report summarizing quarterly ground water monitoring conducted by Blaine Tech Services at the above mentioned site which is currently an U S A Petroleum Station This report presents the 1 results of quarterly ground water monitoring and sampling conducted on November 23, 1999 Work conducted at the site by Blaine Tech Services was performed in accordance with the field methods and procedures described in Lnclosure A ' Work Performed ' On November 23, 1999, depth to ground water was measured in monitoring wells MW-1 and MW-4 through MW-10 The site ground water monitoring well casings were surveyed to mean sea level by Morow Surveying, a licensed land surveyor The depth to water measurements were used to construct a ground water elevation contour map which is included as Figure l Monitoring wells MW-2 and MW-3 were not measured Based on the ground water elevation contours illustrated in Figure 1, ground water flow at the site was generally to the northeast with a hydraulic gradient of approximately 0 005 Cumulative ground water measurements are presented in Table 1 Ground water samples were collected from monitoring wells MW-1 and MW-4 through MW-10 on November 23, 1999 Monitoring wells MW-2 and MW-3 were not sampled The samples were submitted to Southern Petroleum Laboratories (a California-certified laboratory) for analysis of benzene, toluene, ethylbenzene, and total xylenes, and methyl tertiary butyl ether (MTBE) using EPA Method 8021B and total purgeable petroleum hydrocarbons (TPPH) as gasoline using EPA Method ' 8015 Modified A map illustrating concentrations of benzene, TPPH as gasoline and MTBE for the November 23, 1999, sampling event is included as Figure 2 Cumulative ground water analytical results are summarized in Table 1 Copies of the field data sheets are presented in Enclosure B A copy of the laboratory analytical report with chain-of-custody documentation for the November 23, 1999 sampling event is presented in Enclosure C Providing a Competitive edge