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i Harding Lawson Associates December 20, 1994 256661 ' San Joaquin County Mr Harlin Knoll Page 6 ' highest concentrations were reported in sample WS-1 located adjacent to and downgradient of the Site A UST excavation (Plate 2) Toluene and xylene were also reported Sample WS-2 at concentrations of 12 ug/1 and 39 ug/l, respectively 1 The groundwater sample collected from the Site A well MW-A1 located approximately 45 feet downgradient of the UST excavation was reported as not containing TPHg and BTEX above the method reporting hints Site B ' Detectable concentrations of TVHC were reported in soil gas samples SG-2 (77,000 ug/1) and SG-5 (0 5 ug/1) (Table 1) SG-2 was located adjacent and downgradient of the former UST while SG-5 was located approximately 45 feet northeast and downgradient of the former UST location (Plate 3) BTEX ' were detected only in sample SG-2, however the concentration of benzene could not be quantified due to interference on the chromatogram The groundwater sample collected from monitoring well MW-B1 was reported to contain 7 1 mg/1 ' TPHg, 2,200 ug/l benzene, 600 ug/l toluene, 440 ug/1 ethylbenzene and 1,100 ug/1 xylenes (Table 2) Organic lead was not detected above the method reporting limit Fuel Oil Bunker BTEX was not reported in the two soil samples collected from below the bunker TPHd varied from. 4,100 mg/kg to 7,100 mg/kg and TRPH varied from 520 mg/kg to 1,800 mg/kg The higher concentrations of TPHd and TRPH were reported for the sample collected from the south end of the bunker CONCLUSIONS Groundwater data collected on October 19, 1994 indicates that groundwater at the facility flows to the 1 northeast at a gradient of 0 001 to 0 003 Site specific or local groundwater flow regimes have not been determined Based on the data collected during this investigation, groundwater approximately 45 feet downgradient of the Site A excavation does not appear to be impacted by petroleum hydrocarbons Soils in this vicinity may be impacted as evidenced by PID measurements and odor Groundwater in the vicinity of the former Site B UST has been impacted by TPHg and BTEX Benzene was reported in the groundwater sample from MW-B1 at 2,200 ug/1 The maximum contaminant level (MCL) for benzene established for the benefit of human health and welfare by both state and federal agencies is 0 5 ug/1 Organic lead was not detected in groundwater from the Site B monitoring well Soils below both ends of the bunker appear to be impacted by petroleum hydrocarbons quantified as TPHd and TRPH