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3.5.4 UP-GRADIENT WELLS <br /> Wells MW-9 and MW-19 are used to verify concentration trends up gradient of the site. <br /> With the exception of the periodic low-level TPHd detections in both wells and <br /> low-level MTBE detection in well MW-9, these wells do not contain petroleum <br /> constituents and are sampled annually. Both wells contained TPHg during the third <br /> quarter 2010 sampling event: 90 µg/l, in MW-19 (the laboratory noted that the analyte <br /> was present in the associated method blank) and 48 µg/L in MW-19 (detection is below <br /> the reporting limit and estimated). <br /> 3.5.5 DEEPER WATER-BEARING ZONE WELL <br /> Well DW-2 is used to verify concentration trends down gradient and within a deeper <br /> water-bearing zone. Historically,TPHd, TBA, and DIPE have been detected in this well, <br /> and current detections are within historical ranges for those constituents. <br /> 3.6 GWE SYSTEM PERFORMANCE <br /> Based on the groundwater analytical data collected from well MW-1, the GWE system <br /> removed approximately 3.3 pounds TPHg, 0.4 pounds benzene, and 2.7 pounds MTBE <br /> during the second half of 2010. <br /> As of December 20, 2010, approximately 11,543,933 gallons of groundwater have been <br /> extracted (Table 3). During the second half of 2010, approximately 16,543 gallons of <br /> groundwater were treated. The GWE system flow rates averaged 0.05 gallons per <br /> minute. <br /> 3.6.1 OPERATIONAL ISSUES <br /> There were no operational issues. <br /> 3.6.2 SYSTEM EFFECTIVENESS <br /> As discussed in previous reports, the relatively stable MTBE concentrations since <br /> August 2006 suggest that pumping from well MW-1 is ineffective. Several requests to <br /> 241729(28( 7 CONESTOGA-ROVERS&ASSOCIATES <br />