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I Former Canteen Facility January 13,2005 Quarterly 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 indicates that there is a southwesterly hydraulic gradient across the Site of approximately 0 001 feet/foot Figure 2 illustrates Ithe groundwater contours and gradient for tins 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 IGroundwater Anal ical 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 Site monitor wells indicated the following• • • Benzene was detected in the groundwater samples from monitor wells MW-313 and MW-13A at concentrations of 3 3 and 0 54 µg/1, respectively The CAMCL for benzene is 10 µg/1, exceeded in MW-3D • Toluene was detected in monitor well MW-13A at a concentration of 1 5 µg11 The CAMCL for toluene is 150 µg11 + Ethylbenzene was detected in monitor wells MW-3D and MW-13A at concentrations of 4 2 and 0 89 µg/l, respectively The CAMCL for ethylbenzene is 700 µg/1 I • Total xylenes were detected in monitor wells MW-31) and MW-13A at concentrations of 0 72 µg/1 and 3 5 µg/1, respectively The CAMCL for total xylenes is 1,750 µg/L • TPH(g) was detected in each monitor well, however, only MW-3's concentration was not considered an estimate by the laboratory The concentration in MW-3 was 120 1,ig/1 There is no established CAMCL for this constituent f • MTBE was detected in monitor wells MW-3, MW-3A, MW-3D, and MW-11 at concentrations of 85, 210, 5 4, and 22 µg/1, respectively The CAMCL for MTBE is 13 µg/l, exceeded in MW-3, MW-3A, and MW-I 1