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I Project Quarterly Update Report May 11, 1992 Southland, 9110 Thorrrton Road, Stockton, Caldomla 5 I ■ No detectable TPH-as-gasollne concentrations in the samples from any of the morntonng wells, pumping wells, or nearby domestic wells from January 1991 through March 1992, except monitoring well MW-1, ■ No detectable benzene, toluene, ethylbenzene, or xylenes in samples collected from the same wells from April 1991 through March 1992, except for domestic well 9172 during August and September 1991, and monEtonng well MWA In March 1992 Southland has submitted correspondence to the San Joaquin County Department of Health Irequesting that the groundwater treatment system be put in dormant status, with reactivation criteria based on changes in water quality data 4.0 SUMMARY Monitoring data has documented an increase in the groundwater elevation of approximately 1 02 feet during this reporting period The average depth to water in March 1992 was 45 74 feet below surface grade, compared to a depth of approximately 20 feet below surface grade in June 1986 The groundwater flow direction remained in an easterly direction at an average gradient of approximately 0 002 during the three month reporting period I On March 30, 1992, a total of nine monitoring wells (three wells and two three-well clusters) and two pumping wells were sampled and analyzed for BTEX and TPH-as-gasoline Analytical results reported no detectable concentrations for any constituents analyzed in any of the samples, except Imonitoring weIIJMW-1 Analytical results of the sample from this well reported low coneentration—sq TPH-as-gasoline, benzene, toluene, and xylenes of 19 ppb, 0 5 ppb, 6 0 ppb and 0 9 ppbl respectNely iA select group of nearby domestic wells were sampled three times during the quarter and analyzed for BTEX and TPH-as-gasoline The analytical results for the samples from the domestic wells Ireported no detectable BTEX or TPH-as-gasoline concentrations in any of the samples A review of the laboratory analytical results collected to date shows that decreases in BTEX and ' TPH-as-gasoline concentrations have occurred over the duration of the project to the current nondetectable levels In all monitoring and domestic wells except MWA, as reported above The -- _ — LL - — co� ncentrations_reported from the March 1992—992--s—ample from MWA are below drinking water levels It is apparent that the combined efforts of separate-phase product removal, groundwater extraction, GROUNDWATER _, T TECHNOLOGY, INC