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r � <br /> neither sampled in the 4Q99 nor in the1Q00 sampling event, thus, no additional <br /> sampling data has been obtained for this well since the "Draft 1999 Annual <br /> Monitoring Report." It should be noted that the nearest downgradient <br /> monitoring well, LM072A, is over 1800 ft. downgradient from the PCE plume <br /> identified in the area of LM059A. The Report provides no evaluation on the <br /> potential need for additional monitoring wells downgradient from LM059A. <br /> Although, the quarterly monitoring report may not be the appropriate vehicle <br /> to address this concern, the potential need for additional monitoring wells <br /> downgradient from LM059A should be evaluated. <br /> Dieldrin has been detected fairly consistently above the 0.05 µg/L <br /> Aquifer Cleanup Level (ACL) in wells LM003AA and LM015AA of the Upper Horizon <br /> (including the 1Q00 event) . However, even the Army's visually-estimated <br /> capture zone around LM015AA (as shown in the 4Q99 report) does not appear <br /> adequate to contain the northwest movement of Dieldrin in the Upper Horizon. <br /> Table 6.4-1 in the "Draft 1999 Annual Monitoring Report" states that dieldrin <br /> will be sampled quarterly at LM003 once a dieldrin extraction well is <br /> installed at SWMU 2/3. For clarity and to facilitate the review process, a <br /> discussion should be included in the Report regarding the rationale for the <br /> dieldrin sampling frequency at wells LM003 and LM015AA. Although, the <br /> quarterly monitoring report may not be the appropriate vehicle to address this <br /> concern, the sampling frequency for wells LM003 and LM015AA should be <br /> evaluated. <br /> Dieldrin was again detected above the 0.05 µg/L ACL in extraction wells <br /> EW003 (0.11 /cg/L) and EW004AU (0.074 Ag/L) , which are proposed to be taken <br /> offline. As was noted in TechLaw's review of the 4Q99 report and the 1999 <br /> annual monitoring report, the Report does not evaluate possible downgradient <br /> movement of Dieldrin-contaminated groundwater from EW003 and EW004AU in the <br /> event these extraction wells are taken offline. Although, the quarterly <br /> monitoring report may not be the appropriate vehicle to address this concern, <br /> the possible downgradient movement of Dieldrin-contaminated groundwater from <br /> EW003 and EW004AU in the event these extraction wells are taken offline should <br /> be evaluated. <br /> It should be noted, that the Report includes a table (Table 3-7) that <br /> presents a summary of sample concentrations from wells for which the <br /> analytical results differed by some measure from the previous analytical <br /> result (i.e. , either the new sample concentration is greater than two times <br /> the previous sample concentration and the new result is greater than the <br /> aquifer cleanup level (ACL) or background concentration, or the new sample <br /> concentration is ten times greater than the previous sample concentration and <br /> the new result is less than ACL or background) . It is unclear how the criteria <br /> for inclusion in this table were established. <br /> 2 <br />