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Mr Dann L Rouse Exxon Company, U S A November 5, 1998 Page 2 Ground Water Sampling Analytical Results Ground water samples collected from monitoring wells MW-1 through MW-8 on October S, 1998, were submitted to Sequoia Analytical for analysis of benzene, toluene, ethylbenzene, and total xylenes (BTEX) and methyl tertiary butyl ether (MTBE)by EPA Method 8020, and total purgeable petroleum hydrocarbons (TPPH) as gasoline by EPA Method 8015 Modified Concentrations of BTEX and TPPH as gasoline were less than the laboratory reporting linuts in the samples collected Concentrations of MTBE by EPA Method 8020 were reported in monitoring wells MW-1 through MW-6 and MW-8 ranging from 6 pel, (MW-2) to 53 µg (MW-3) Figure 4 presents dissolved concentrations of MTBE in ground water Cumulative analytical results are summarized in Table 1, and a copy of the laboratory analytical report for the October 5, 1998, sampling event is presented in Enclosure B Future Work Fourth quarter 1998 ground water sampling is scheduled for December 1998 Due to a rise in the water table over the past to years, the monitoring well screens are submerged In order to obtain ground water samples from the water table, Delta proposes to overdrill and replace on-site monitoring wells MW-1, MW-2, MW-3, and MW-7 with wells screened across the water table In December 1998, a work plan will be prepared and submitted Based on ground water measurements collected since monitoring activities began at the site in August 1991, flow direction has been historically towards the northeast with some seasonal variances towards the east The Southland property located west of the former Exxon service station has recently removed and replaced its underground storage tanks (UST's) We understand that as a result of soil conditions encountered within the tank basin, Southland has initiated a soil and ground water contanunation investigation Delta will be conducting a regulatory agency file review of that site in November 1998 Remarks/Signatures The interpretations contained in this report represent our professional opinions, and are based in part, on information supplied by the client These opinions are based on currently available information and are arrived at in accordance with currently accepted hydrogeologic and engineering practices at this time and location Other than this, no warranty is implied or intended Delta recommends that a copy of this report be forwarded to Mr Mike Infurna Ms Elizabeth Thayer San Joaquin County Environmental Health California Regional Water Quality Control Board, Division, Public Health Services Central Valley Region Post Office Box 2009 3442 Routier Road Stockton, California 95201 Sacramento, California 95827-3098