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Mr Kyle Christie Project 0805-140 02 July 28, 1995 Page 2 RESNA began monitoring the groundwater in wells MW-1 through MW-4 on October 30, 1991 (RESNA, June 26, 1991, Report 30004-4) Wells MW-5 and MW-6 were added to the monitoring program in March 1993 and December 1993, respectively Dissolved hydrocarbons have been detected in monitoring wells MW-1 and MW-5 since monitoring began In March 1992, EA Engineering, Science and Technology (EA) observed removal of the oil-water separator/clanfier (EA, August 1992, Report 80633 01) EA collected one soil sample from beneath the former oil-water separator and one sample from the concrete Analytical results from the sod samples indicated that oil and grease (quantified as total oil and grease) was present Concentrations of volatile organic compounds, senuvolatiie organic compounds, and polychlorinated biphenyls were below detection limits Total metals were also below detection limits, with the exception of arsenic and barium, which were detected at concentrations of 0 0051 and 0 12 parts per million, respectively On March 2, 1992, RESNA conducted a vapor extraction test at the site (RESNA, June 15, 1992, Report 30004-5) Results of the test indicated that soul beneath the site can • be remediated by vapor extraction, and the evaluated radius of influence was 30 feet In May 1994, RESNA subrrutted a Problem Assessment Report (PAR [RESNA, May 11, 1994, Report No 30004-8]) to the San Joaquin County Public Health Services and the California Regional Water Quahty Control Board A Final Remediation Plan and subsequent remediation will be prepared and implemented in the future GROUNDWATER MONITORING, SECOND QUARTER 1995 EMCON was contracted by ARCO to monitor groundwater monitoring wells previously installed at the site Field work included measuring depths to water and collecting groundwater samples for subjective and laboratory analyses EMCON used these data to evaluate the direction and gradient of groundwater flow beneath the site On May 12, 1995, a technician from EMCON measured the depth to water and collected groundwater samples from monitoring wells MW-1 through MW-6 for subjective and laboratory analyses The sampling and analysis procedures used are presented in Attachment A The technician did not observe floating product or product sheen on samples collected from the wells (see Table 1) The surveyed elevations of the top of casing and the depth to groundwater measurements • (summarized in Table 1) were used to evaluate the potentiometric surface beneath the site On May 12, 1995, the direction of groundwater flow was toward the east with a gradient SACW\PJGM05\08051400 2SS-94\pas 4