SITE INFORMATION AND CORRESPONDENCE

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• MW -6: Central site near source area - This well is co -located with MW -10 and MW -7 in the center of the site. It monitors the downgradient tip of the former main VOC source area. The well continues to show fluctuating concentrations of TCE and 1,1-DCE above MCLS. Groundwater flow in this vicinity is completely intercepted by pumping from GW -4 and GW -7. • MW -5R MW -15 MW -16 and MW -17: Offsite southeast stable concentrations - These wells monitor the former offsite southeast migration pathway that is now intercepted and controlled by pumping at GW -7. VOC concentrations at MW -5R dropped to ND abruptly after GW -7 began pumping in March 2006. When all pumps were off during August 2008, a slight rebound occurred in the concentration of TCE but concentrations returned to ND when extraction was re -started. MW -15 was installed in 2004. After three years of sampling the concentration trends appear to be stable. The concentration of l,l-DCE has a slight downward trend which indicates that pumping at GW -7 is influencing concentrations at MW -15. MW -16 and MW -17 were first sampled in January 2008. Both wells have been sampled 7 times and have flat concentration trends. Due to their downgradient distance, it may take several years for the beneficial effect of pumping at GW -7 to begin to reduce the groundwater concentrations at these wells. Quarterly water level measurements indicate a continuing southeastward gradient. • MW -7 and MW -10: Centrally located ND in deeper zones - VOCs were detected in MW -7 only in May 2000, when trace concentrations of TCE (0.51 µg/L) and PCE (0.64 µg/L) were detected. In nine years since that occurrence, no VOCs have been detected in this well. MW -7 is co -located with MW -10 which monitors the intermediate depth zone above the intake for MW -7. MW - 10 has also shown only trace concentrations of VOCs in 11 years of monitoring, never had any detections above the project Water Quality Objectives, and no detections in the last 3'/z years. MW -7 and MW -10 are proposed to be retained as sentry wells against deeper migration of the plume core area with annual and semiannual sampling, respectively. • MW -13 and MW -14• ND offsite monitoring wells — It is proposed to reduce the sampling frequency from semiannual to annual for two offsite wells that have continued to exhibit no detections of VOCs or low concentrations of VOCs with a decreasing trend, but are considered necessary to sample for verification of plume migration control (MW -13 and MW -14). MW -13 has been sampled since June 1998 with only a single detection of TCE (1.5 µg/L) in January 2000 and sporadic detections of trace concentrations of chloroform (maximum 0.64 µg/L) prior to 2002. This well will be retained as a sentry well near the site perimeter. MW -14 has been sampled since November 1998. Prior to 2002 this well had detections of TCE with a decreasing trend and several detections of 1,1-DCE below 1 pg/L. In the 7'/2 years the results have been ND except for detections less than the WQO (< 0.8 pg/L) in 2006. Page 3 of 6