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Former Canteen Facility January 14, 2003 Quarterly Groundwater Monitoring Report Page 4 • TPH(g) was detected in monitor wells MW-3, MW-3A, MW-3D, and MW-ll at concentrations ranging from 71 to 170 µg11 MTBE was detected in MW-3, MW-3A, MW-3D, and MW-11 at concentrations of 110, 340, 11, and 27 dig/l, respectively The CAMCL for MTBE is 13 µg/l, exceeded in MW-3, MW-3A, and MW-11 • 1,2-DCA was detected at a concentration of 98 µg/L in MW-11, which exceeds the CAMCL of 0 5 µg/L Historical groundwater analytical results are summarized on Table 2 Figures 3 and 4 illustrate the isoconcentration contours for benzene and TPH(g) concentrations, respectively, in the shallow aquifer wells Figures 5 and 6 illustrate the concentrations for benzene and TPH(g), respectively, in the one deep aquifer well (MW-13B) The field notes and laboratory reports for this quarterly monitoring event are attached as Appendix A INVESTIGATION SUMMARY and CONCLUSIONS Sampling and analysis was performed in November 2003 to evaluate the current concentrations of petroleum hydrocarbons of Site groundwater monitoring wells Based on the results, AES has developed the following conclusions • Monitor wells MW-3, MW-3A, MW-3D, MW-11, and MW-13A had detectable concentrations exceeding the CAMCL concentrations of at least one of the following constituents benzene, toluene, ethylbenzene, xylenes, MTBE, and 1,2-DCA • Groundwater impacts appear to be generally confined onsite, although the only detectable 1,2-DCA concentrations are centered offsite on monitor well MW-11 The majority of the groundwater impacts are centered on the MW-3 and MW-13 series wells RECOMMENDATIONS AES recommends the following for the Former Canteen Facility • Continue groundwater monitoring and reporting, including measurement of depth to groundwater in each well, evaluating monitor well status, preparation of a potentiometric surface contour map containing the calculated gradient and • approximate rate of groundwater movement, and preparation of isoconcentration contour maps for benzene and TPH(g) at the two different screened aquifer depths