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I i Former Canteen Facility September 17, 2002 Quarterly Groundwater Monitoring Report Pam I • TPH(g) was detected in monitor wells MW-3A and MW-13 at concentrations of 90 and 180,000 pg/l, respectively + MTBE was detected in 1\4W-3, MW-3A, MW-313, MW-11 and MW-13 at concentrations ranging from 4 1 µg/l to 780 µg/l The CAMCL for MTBE is 13 I µg/l, exceeded in MW-3, MW-3A,MW-11, and MW-13 • 1,2-DCA was detected at a concentration of 15 µg/L in MW-11, which exceeds the CAMCL of 0 5 pg/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 August 2002 to evaluate the current concentrations of petroleum hydrocarbons of Site groundwater monitoring wells Based on the results, AES-RS has developed the following conclusions I • Monitor wells MW-3, MW-3A, MW-313, MW-11, and MW-13 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-RS 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 O CES��