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i GROUNDWATER MONITORING REPORT USA PETROLEUM - STOCKTON #110 JANUARY, 1995 3.0 SUMMARY AND CONCLUSIONS a 1 3 1 Results of Groundwater Laboratory Analyses ' Detectable levels of petroleum hydrocarbons as gasoline were reported in monitoring wells MW-2-P and MW-3-P at 430 parts per billion (ppb) and 930 ppb, respectively No;detected levels of petroleum hydrocarbons as diesel were reported in any of the wells BTEX compounds were all below the detection limit of 0 5 ppb in MW-1-P Benzene values ranged from 0 79 ppb in MW-3-P to 26 ppb in MW-2-P Toluene was detected at 19 ppb in MW-2- P and 4 6 in MW-3-P Only MW-2-P had any detectable levels of ethylbenzene The reported concentration in MW-2-P was 7 5 Total xylenes ranged from 12 ppb in 14W-3-P to 1 7 ppb in MW-2-P No detectable levels of total lead were detected in MW-1-P and MW-2- ' P Total lead was detected at a concentration of 3 7 ppb in MW-3-P Groundwater(laboratory results for September, 1992, September, 1993, March, August, and December, 1994 are summarized in Table III, certified laboratory reports and COC documents for the most recent ' sampling event are included in Appendix D 3.2 Groundwater Conditions Recent groundwater data collected at the site indicate groundwater occurring at depths ranging ' from 73 48-feet to 72 81-feet bgs The groundwater elevation ranges from a high of 46 59-feet below MSL to a low of 48 03-feet below MSL Groundwater is flowing to the ' north-northeast with a hydraulic gradient of approximately 0 012 or about 1 28-feet per 100- feet Several graphic presentations of the flow beneath the site are presented on Figures 3 through 10 The field data and subsequent flow direction calculations suggests that the groundwater below ' the site generally flows east but has fluctuated slightly north and south several times�dunng the year 5007 B 3 1