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V ICanteen Facility September 28, 2001 Qu=erly Grotindwater MonitS2ring Report Palze GROUNDWATER NDITI N The following summarizes the local groundwater gradient and the groundwater analytical results IGroundwater Gradient Interpretation of the monitor well gauging data indicates that there is a south - Isouthwesterly hydraulic gradient across the Site of approximately 0 0012 feet/foot Figure 2 illustrates the groundwater contours and gradient for this gauging event The gradient appears to be consistent with past gauging events The change in 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 Result Groundwater analytical results are compared to the California Department of Health Services Drinking Water Standard Maximum Contaminant Levels (CAMCL) Analysis of the seventeen groundwater samples obtained from the on-Site monitor wells indicated the following ' • Benzene was detected in groundwater samples from monitor wells MW-31), MW-13, MW-13A and MW-13B at concentrations ranging from 0 81 to 19,000 µg11 Groundwater samples taken from monitor wells MW-31), MW-13, and MW-13B exceeded the CAMCL for benzene of 1 0 µg/l • Toluene was detected in monitor wells MW-3, MW-3A, MW-3D, MW-7, MW- 13, MW-13A and MW-13B at concentrations ranging from 0 60 to 27,000 µg/l The CAMCL for toluene is 150 µg/l, exceeded only in MW-13 ' • Ethylbenzene was detected in monitor wells MW-31), MW-13, MW-13A, and MW-13B at concentrations ranging from 0 54 to 3,100 µg/l The CAMCL for ' ethylbenzene is 700 µg11, exceeded only in MW-13 • Total xylenes were detected in monitor wells MW-3D, MW-13, MW-13A, and ' MW-13B at concentrations ranging from 2 8 to 17,000 µg11 The CAMCL for xylenes is 1,750 µg/L, exceeded only in MW-13 1