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KEI-P89-1104 .R9 December 17 , 1992 Page 10 consistently shown non-detectable concentrations of TPH as gasoline and benzene in all of the wells since the inception of sampling on October 26, 1990 , with the exception of 220 ppb of TPH as gasoline and 76 ppb of benzene that were detected in well MW3 on the initial sampling date. In MW1 , concentrations of TPH as diesel have ranged from non-detectable to 290 ppb, and no TOG has been detected. Therefore, based upon the sample discussed above, it appears that no significant ground water contamination is present at the site The analytical results of the soil samples collected from the borings of EB1 through EB6 indicated low to predominantly non- detectable concentrations of TPH as gasoline, TPH as diesel , and benzene. The analytical results of the soil samples collected from the borings of EB3 through EB6 .indicated non-detectable concentra- tions of all EPA method 8010 constituents, except for tetrachloroe- thene, which was detected at concentrations ranging from 5 . 7 ppb to 55 ppb, and for 1, 2-dichloroethane, which was detected at a concentration of 6 . 1 ppb in sample EB4 ( 35) . In addition, no detectable concentrations of TPH as diesel, TPH as gasoline, or benzene were encountered during the installation of the four existing monitoring wells , with the exception of 0 . 088 ppm of benzene that was detected at 30 . 5 feet below grade in MW3 . Based on the analytical results of the soil samples collected from the seven exploratory borings, during the installation of the four monitoring wells, and during the removal of the existing under- ground tanks and lines in 1989 , it appears that the only area of significant soil contamination remaining at the site is located at the northern portion of the existing western pump island (at approximate depths between 17 and 30 . 5 feet below grade) . Based on the analytical results of the soil and ground water samples collected and evaluated to date, and no evidence of free product or sheen in any of the wells, KEI recommends the continua- tion of the current quarterly ground water monitoring and semi- annual sampling program of the existing wells, per KEI ' s proposal (KEI-P89-1104 .P5) dated December 10 , 1990 , and as modified in KEI ' s quarterly report (KEI-P89-1104 .QR4) dated February 3 , 1992 . The wells are tentatively scheduled to next be sampled in December of 1992 . Recommendations for altering or terminating the current ground water monitoring and sampling program will be made as warranted. DISTRIBUTION A copy of this report should be sent to Mr . Harlin Knoll of the SJCPHS, and to the Regional Water Quality Control Board, Central Valley Region