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• Matrix Spike/Matrix Spike Duplicate (MS/MSD) Sample Performance • Field Duplicate Comparison • Detection Limits Summary of Findings: All samples were analyzed according to the accompanying chains of custody and all analytical holding times were met with one exception. Hexavalent chromium was analyzed outside of the 24 hour recommended holding time in 30 samples. Samples with hexavalent chromium detected were qualified as estimated (J); samples with no detectable hexavalent chromium concentrations were qualified as estimated non-detects (UJ) at the method detection limit. QC data were reviewed for laboratory and instrument precision and accuracy from LCS/LCSD recoveries and relative percent differences (RPDs) and MS/MSD sample recoveries and RPDs. All quality control elements were found to be within acceptable limits with the following exceptions: • The MS/MSD percent recoveries associated with the analysis of MW-2 were greater than the upper control limit for sulfate; the result was qualified as estimated (J) in the parent sample. • The MS/MSD percent recoveries and RPD associated with the analysis of MW-323 were not meaningful for sulfate. The concentration of sulfate in the parent sample was greater than four times the concentration used for the spike. Therefore, the criteria were not evaluated. • The MS/MSD percent recoveries and RPD associated with the analysis of TW-15 and MW-9 were not meaningful for manganese. The concentration of manganese in the parent samples was greater than four times the concentration used for the spike. Therefore, the criteria were not evaluated. Field sampling precision was also evaluated by using the calculated RPD between results reported for the field duplicate pairs, which are listed above. All RPD results were found to be within the acceptable limits for precision for all methods with the following exception: • The field duplicate pair MW-303 and MW-303 (Duplicate) had one RPD that was greater than the control limit for chromium; chromium was qualified as estimated (J) in the parent sample. No target analytes were detected in any method blank or field QC samples with the following exceptions: • Equipment Rinse and Field Blank, collected on April 24, 2012, were associated with the analysis of one sample and had TOC detected at 0.7 and 0.5 mg/L, respectively. EW-1 had TOC detected at a concentration that was greater than the reporting limit, but less than five times the blank concentration, and was qualified as estimated (J). • Equipment Rinse and Field Blank, collected on April 25, 2012, were associated with the analysis of four samples and had TOC detected at 1.0 and 0.8 mg/L, respectively, and TDS detected at 8.0 mg/L in both. TDS was detected in the associated samples at concentrations that were greater than five times the blank concentration and were not qualified. TOC was detected in four samples at concentrations that were greater than the reporting limit, but less than five times the blank concentration, and were qualified as estimated (J) in all four samples. • Equipment Rinse and Field Blank, collected on April 30, 2012, were associated with the analysis of four samples and had TDS detected at 6.0 and 8.0 mg/L, respectively, and TOC detected at 0.9 mg/L in both. TDS was detected in the associated samples at concentrations that were greater than five times the blank concentration and were not qualified. TOC was detected in Page 2of6