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Former Canteen Facility April 14,2005 Quggerly Groundwater Momtonn Re ort Pa e 4 • MTBE was detected in morutor wells MW-3, MW-3A, MW-3D, MW-13, and MW- 11 at concentrations of 44; 130, 9, 76, and 39 µg/l, respectively The CAMCL for MTBE is 13 µg/1,exceeded in MW-3, MW-3A, MW-13, and MW-11 • 1,2-DCA was detected at a concentration of 78 µg/L in MW-11, which exceeds the CAMCL of 0 5 l,g/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 GROUNDWATER INVESTIGATION SUMMARY and CONCLUSIONS Sampling and analysis was performed in March 2005 to evaluate the current concentrations of petroleum hydrocarbons of Site groundwater monitoring wells Based on the results, Delta has developed the following conclusions I . • Monitor wells MW-3, MW-3A, MW-3D, MW-11, and MW-13 had detectable concentrations exceeding the CAMCL action level concentrations of at least one of the following constituents benzene, ethylbenzene, xylenes, TBA, MTBE, and 1,2- DCA • Groundwater impacts appear to be generally confined onsite The only detectable 1,2- DCA concentrations are located offsite in monitor well MW-11 Well MW-11 also has detectable concentrations of MTBE and TPH(g), although the laboratory flagged the result as estimated. The majority of the groundwater impacts are centered on the MW-3 and MW-13 series wells REMEDIATION SYSTEM OPERATION and MAINTENANCE Delta installed an approved soil and groundwater ediation system at the site during the period from February 23 to March 23, 2004 (Figure 7 The remediation system consisted of air sparging (AS) in conjunction with soil vapor extraction (SVE) The SVE system was put into operation on March 24, 2004 Vacuum for the SVE system has been provided by a trailer- mounted internal combustion engine (ICE) unit In addition to the vacuum for the system, the ICE unit also destroys hydrocarbon vapors that are recovered from the subsurface SVE SYSTEM OPERATIONS • SVE operations continued with only wells VE-1 and VE-3 For the majority of the quarter, these two wells continued to produce enough hydrocarbon vapors for efficient ICE unit power Operation and maintenance (O&M) activities for the AS-SVE remediation system were I