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1 � <br /> rc GROUNDWATER CONDITIONS <br /> 1 The following sections summarize the local groundwater gradient and the groundwater analytical <br /> results <br /> 1 Groundwater Gradient <br /> Interpretation of the monitor well gauging data indicates that there is a south - <br /> 1 southwesterly hydraulic gradient across the Site of approximately 0 003 feet/foot Figure <br /> 2 illustrates the groundwater contours and gradient for this gauging event The gradient <br /> appears to be consistent with past gauging events The drop in water levels is a result of <br /> 1 cyclical fluctuations in the weather and the proximity of the site to the Stockton Diverting <br /> Canal, located approximately 1000 feet to the northeast The historical groundwater <br /> ' elevations are summarized on Table 1 <br /> Groundwater Analytical Results <br /> 1 Groundwater analytical results are compared to the California Department of Health <br /> Services Drinking Water Standard Maximum Contaminant Levels (CAMCL) Analysis of <br /> the seventeen groundwater samples obtained from the on-Site monitor wells indicated the <br /> following <br /> ' • Benzene was detected in groundwater samples from monitor wells MW-3, MW- <br /> 13, and MW-13A at concentrations ranging from 1 b to 12,000 µg/l, each <br /> exceeding the CAMCL for benzene of 1 0 µg/1 The benzene concentrations in <br /> ' MW-3 have increased However, the concentrations have decreased in MW-13 <br /> and MW-13A since December 2000 <br /> 1 • Toluene was detected in monitor wells MW-3, MW-3A, MW-3D, MW-13, MW- <br /> 13A and MW-13B at concentrations ranging from 0 7 to 18,000 µg/1 The <br /> 1 CAMCL for toluene is 150 µg/l, which was exceeded only in MW-13 <br /> Concentrations of toluene increased in MW-3, and decreased in MW-3A, MW-3D, <br /> MW-13 and MW-13A, and MW-1313 <br /> 1 • Ethylbenzene was detected in monitor wells MW-3, MW-3D, and MW-13 at <br /> concentrations ranging from 1 0 to 2,700 µg/1 The CAMCL for ethylbenzene is <br /> ' 700 pg/l, which was exceeded only in MW-13 The concentration increased in <br /> MW-3, MW-3D, and remained the same in MW-13 <br /> 1 <br /> Canteen Facility April 13, 2001 <br /> Quarterly Groundwater Monitoring Report Page 3 <br /> 1 <br />