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� N�S� <br /> ICanteen Facility September 28,2001 <br /> Q_u_aderly Groiandwater Monitoring Rgport pqCFp 4 <br /> TPH(g) was detected in monitor wells MW-3, MW-3A, MW-3D, MW-13, and <br /> MW-13B at concentrations ranging from 78 to 150,000 µg/l <br /> MTBE was detected in MW-3, MW-3A, MW-31), MW-11 and MW-13 at <br /> concentrations ranging from 8 0 µg11 to 1600 µg/1 The CAMCL for MTBE is 13 <br /> pg/l, exceeded in MW-3, MW-3A and MW-13 <br /> • 1,2-DCA was detected at a concentration of 12 0 µglL in MW-11, which exceeds <br /> the CAMCL of 0 5 µg/L <br /> Historical groundwater analytical results are summarized on Table 2 Figures 3 and 4 illustrate <br /> I the isoconcentration contours for benzene and TPH(g) concentrations, respectively, in the <br /> shallow aquifer wells Figures 5 and 6 illustrate the isoconcentration contours for benzene and <br /> TPH(g) concentrations, respectively, in the one deep aquifer well (MW-13B) The field notes <br /> and laboratory reports for this quarterly monitoring event are attached as Appendix A <br /> INVESTIGATION SUMMARY and CONCLUSIONS <br /> Sampling and analysis was performed in August 2001 to evaluate the current concentrations of <br /> petroleum hydrocarbons of on-Site groundwater Based on the results, AES has developed the <br /> following conclusions <br /> Monitor wells MW-3, MW-3A, MW-31), MW-11, MW-13, and MW-13B had <br /> detectable concentrations exceeding the CAMCL concentrations of at least one of the <br /> following constituents benzene, toluene, ethylbenzene, xylenes, MTBE, and 1,2- <br /> DCA <br /> • Groundwater impacts appear to be generally confined onsite, although the only <br /> detectable 1,2-DCA concentrations are centered offsite on MW-11 The majority of <br /> the groundwater impacts are centered on the MW-3 and MW-13 series wells <br /> I <br />