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• Xylenes were detected in monitor wells MW-3, MW-9, MW-13, and MW-13A at concentrations ranging from 1 S to 13,000 µg/l The CAMCL for xylenes is 1,750 ' µg/L, which was exceeded only in MW-13 The concentration increased in MW- 3, MW-9, and decreased in MW-13 and MW-13A ' • TPH(g) was detected in monitor wells MW-3, MW-3A, MW-3D, MW-13 and MW-13A at concentrations ranging from 64 to 120,000 µg/1 ' • MTBE was detected in MW-3, MW-3A, MW-3D, MW-11 and MW-13 at concentrations ranging from 2 6 µg/1 to 630 µg/1 The CAMCL for MTBE is 13 ' µg/1 The concentrations in MW-3, MW-3A, and MW-13 exceed this CAMCL The concentration of MTBE increased in monitor wells MW-3, MW-3A, MW-3D and MW-11 and decreased in MW-13 1 • 1,2-DCA was detected at a concentration of 5 9 �Lg/L in MW-11, which exceeds the CAMCL of 0 5 µg/L The concentration was a decrease since the December ' 2000 sampling event Historical groundwater analytical results are summarized on Table 2 Figures 3 and 4 illustrate the isoconcentration contours for benzene and TPH(g) concentrations, respectively, at screen intervals from 39 to 47 feet below ground surface (bgs) Figures 5 and 6 illustrate the isoconcentration contours for benzene and TPH(g) concentrations, ' respectively, at screen intervals from 63 to 76 feet bgs ' INVESTIGATION SUMMARY and CONCLUSIONS Sampling and analysis was performed in March 2001 to evaluate the current concentrations of ' petroleum hydrocarbons of on-Site groundwater Based on the results, AES has developed the following conclusions ' Monitor wells MW-3, MW-3A, MW-13 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 The majority of the groundwater impacts are centered on the MW-3 and MW-13 series wells 1 Canteen Facility April 13, 2001 Quarterly Groundwater Monitoring Report Page 4