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i <br />• <br /> Canteen Facility January 11, 2042 <br /> QuarLerly Groundwater Momtoring Revort Pape 4 <br /> • TPH(g) was detected in monitor wells MW-3, MW-3A, MW-13, and MW-13A at <br /> concentrations ranging from 94 to 160,000 µg/1 <br /> • MTBE was detected in MW-3, MW-3A, MW-11 and MW-13 at concentrations <br /> ranging from 29 µg/1 to 1,500 µg/1 The CAMCL for MTBE is 13 µg11, exceeded <br /> Iin MW-3, MW-3 A, MW-11, and MW-13 <br /> • 1,2-DCA was detected at a concentration of 15 µg/L in MW-11, which exceeds <br /> I the CAMCL of 0 5 gg/L <br />' Historical groundwater analytical results are summarized on Table 2 Figures 3 and 4 illustrate <br /> the isoconcentration contours for benzene and TPH(g) concentrations, respectively, in the shallow <br /> aquifer wells Figures 5 and 6 illustrate the isoconcentration contours for benzene and TPH(g) <br />' concentrations, respectively, in the one deep aquifer well (MW-13B) The field notes and <br /> laboratory reports for this quarterly monitoring event are attached as Appendix A <br />'• INVESTIGATION SUMMARY and CONCLUSIONS <br />' Sampling and analysis was performed in November 2001 to evaluate the current concentrations of <br /> petroleum hydrocarbons of Site groundwater monitoring wells Based on the results, AES has <br /> developed the following conclusions <br />' <br /> Monitor wells MW-3 MW-11, and MW-13 had detectable concentrations <br /> MW-3A, <br /> exceeding the CAMCL concentrations of at least one of the following constituents <br />' benzene, toluene, ethylbenzene, xylenes, MTBE, and 1,2-DCA <br /> • Groundwater impacts appear to be generally confined onsite, although the only <br />' detectable 1,2-DCA concentrations are centered offsite on monitor well MW-11 The <br /> majority of the groundwater impacts are centered on the MW-3 and MW-13 series <br />' wells <br />' RECOMMENDATIONS <br /> AES recommends the following for the Canteen Facility <br />' Continue quarterly groundwater monitoring and reporting, including measurement of <br /> • depth to groundwater in each well, evaluating monitor well status, preparation of a <br /> potentiometric surface contour map containing the calculated gradient and <br /> a <br />' SLICES tiZ <br />