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Former Canteen Facility September 17,2002 Ouarterly Groundwater Monitoring Report Page 3 GROUNDWATER CONDITIONS The following summarizes the local groundwater gradient and the groundwater analytical results Groundwater Gradient Interpretation of the monitor well gauging data for this quarter indicates that there may be a groundwater divide over the former tankpit area with a southwest to east hydraulic gradient across the Site of approximately 0 002 ft/ft Figure 2 illustrates the groundwater contours and gradient for this gauging event The groundwater divide is not consistent with past gauging events The change to water levels is a result of cyclical fluctuations in the weather and the proximity of the site to the Stockton Diverting Canal, located approximately 1000 feet to the northeast The historical groundwater elevations are summarized on Table 1 • Groundwater Analytical Results Groundwater analytical results are compared to the California Department of Health Services Drinking Water Standard Maximum Contaminant Levels (CAMCL) Analysis of the groundwater samples obtained from the seven Site monitor wells indicated the following • Benzene was detected in groundwater samples from monitor wells MW-13, MW- 13A, and MW-13B at concentrations of 19,000, 0 73, and 0 61 deg/l, respectively The groundwater sample taken from monitor well MW-13 exceeded the CAMCL for benzene of 10 µg/l • Toluene was detected in monitor wells MW-3A, MW-3D, MW-13, MW-13A, and MW-13B at concentrations ranging from 2 0 to 28,000 µg/1 The CAMCL for toluene is 150 4g/l, exceeded only in MW-13 • Ethylbenzene was detected in monitor wells MW-13 and MW-13A at concentrations of 4,400 and 0 79 µg/1, respectively The CAMCL for ethylbenzene is 700 µg/l, exceeded only in MW-13 • Total xylenes were detected in monitor wells MW-3D, MW-13, MW-13A, and MW-13D at concentrations ranging from 0 99 to 22,000 µg/l The CAMCL for xylenes is 1,750 µg/L, exceeded only in MW-13 %1GU� a EKES,