ARCHIVED REPORTS_SEMI-ANNUAL GROUNDWATER MONITORING REPORT AUGUST 2010

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ameO detected concentrations are near laboratory reporting limits (typically within a factor of two for organics or five for inorganics). For the August 2010 groundwater monitoring event, AMEC Geomatrix collected one duplicate groundwater sample from each Facility, one from well LPW-3 (sample identification LP-D- 082510) and one from well FCW-2 (sample identification FC-D-082610). The RPD for the analytes is not calculated when reported concentrations are within a factor of two (organics) or five (inorganics) of the laboratory reporting limits, when no analytes are detected above the reporting limits in one of the samples in the pair, or when no analytes are detected above the reporting limits in both samples in the pair. For the results that did not meet these criteria, the RPD was calculated for the analytes that were detected in the primary and duplicate samples using the following equation: RPD-2 x result-duplicate X 100 result+duplicate The calculated RPDs are applicable only when the sample values are greater than or equal to two (organics) or rive (inorganics) times the respective analytical reporting limit. For the sample duplicate pairs with values greater than or equal to two (organics) or five (inorganics) times the reporting limit, the precision goal is a calculated RPD less than 30%. For the primary and duplicate sample results that are less than two or five times the respective analytical reporting limit, the precision goal is met when the absolute difference between the results is less than the reporting limit. The calculated RPD and/or absolute difference for primary and duplicate sample pairs met these requirements. Laboratory data accuracy was assessed based on percent recoveries from spiked samples, expressed as a percent of the true or known concentration of the assessed constituent. The average percent recoveries (%R) and/or RPDs for the laboratory control sample/laboratory control sample duplicate (LCS/LCSD), MS/MSD, and surrogate standards analyzed by the laboratory for the applicable methods are within acceptance limits established under EPA SW846 and are summarized in the APPL, Inc., laboratory reports (Appendix B). The method blank, LCS/LCSD, and MS/MSD sample recoveries were within acceptable limits. No analytes were detected in the laboratory method blanks. Detection limits for total and dissolved Cr and dissolved Cr VI were reported for both the reporting limits (RLs) and method detection limits (MDLs). There were two detections of Cr (primary and duplicate groundwater samples from well LPW-3) and one detection of dissolved Cr (groundwater sample from well FCW-1) reported between the RL and MDL during this sampling event. As such, the analytical laboratory flagged the results as estimated ("J" flag). AMEC Geomatrix, Inc. PA10626.000.0\Docs\Semi-Annua1 Groundwater Monitoring&Sampling\Semi-Annual 1-10 10