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y Mr Dann L Rouse Exxon Company,U S A June 22, 1999 Page 2 Ground Water Sampling Analytical Results ' Ground water samples collected from monitoring wells MW-1 through MW-8 on May 14, 1999, 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 Modified, 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 limits in the samples collected from monitoring wells MW-1 through MW-8, and VEW-3 Concentrations of MTBE by EPA Method 8020 Modified were reported in monitoring wells MW-1, MW-3 MW-4, MW-6 and MW-8 ranging from 8 97 micrograms per liter (µg/L) in MW-6 to 60 1 µg/]L in MW-3 ' Figure 4 presents dissolved concentrations of benzene, TPPH as gasoline, and MTBE in ground water for the May 14, 1999, sampling event Cumulative analytical results are summarized in Table 1, and a copy of the laboratory analytical report for the May 14, 1999 sampling event is presented in ' Enclosure B A copy of the field data sheets for the April sampling event is included in Enclosure C ' Discussion 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 We understand that as a result of soil conditions encountered within the tank basin, Southland has initiated a soil and ground water contamination investigation 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 ' Future Work Third quarter 1999 ground water sampling is scheduled for August 1999 ' A monitoring well installation and ground water sampling results report will be prepared and submitted during third quarter 1999 for monitoring wells MW-9 and MW-10 installed adjacent to monitoring ' wells MW-2 and MW-3, respectfully 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, Suite A Stockton, California 95201 Sacramento, California 95827-3098 r