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wells are used to evaluate improvements in groundwater quality as a result of previously
<br /> implemented corrective action measures.
<br /> ATC Associates, Inc. reported that corrective action monitoring well AMW-3 has been
<br /> abandoned.
<br /> Groundwater samples are scheduled to be analyzed quarterly for field parameters (groundwater
<br /> elevation, pH, specific conductance, temperature, and turbidity) and monitoring parameters
<br /> (arsenic, barium, bicarbonate, calcium, carbonate, chloride, gasoline-range petroleum
<br /> hydrocarbons, hexavalent chromium, magnesium, nitrate, oil and grease, potassium, sodium,
<br /> strontium, sulfate,TDS,and VOCs).
<br /> 2.1 Detection Monitoring
<br /> Groundwater samples were collected from the background well (AMW-2) and detection
<br /> monitoring wells (AMW-6, AMW-7, AMW-12,AMW-13, and AMW-14) during the first quarter
<br /> 2008 monitoring event. The field results provided by ATC Associates, Inc. and laboratory results
<br /> provided by BC Laboratories, Inc. for the first quarter 2008 detection monitoring sampling are
<br /> summarized on Table 2.2. The historical groundwater data for the detection monitoring wells are
<br /> presented in Appendix D. The data are graphed on time series concentration plots, included in
<br /> Appendix E. For VOCs, only those compounds that exhibited detections for the first quarter
<br /> 2008 monitoring event were plotted. The concentration limits presented on Table 2.2 were
<br /> calculated by Herst & Associates, Inc. from data collected through the first quarter 2008
<br /> monitoring event. The statistical analysis calculations for detection monitoring wells are included
<br /> in Appendix E. A copy of the statistical analysis methodology is included in Appendix C.
<br /> During the first quarter 2008 monitoring event,barium at AMW-13 and -14,bicarbonate at
<br /> AMW-13, and hexavalent chromium at AMW-6 and AMW-7 exceeded their respective
<br /> concentration limits. The first quarter 2008 barium concentration at AMW-13 (0.34 mg/L) is
<br /> comparable to concentrations observed at that well intermittently since November 2003, and is
<br /> well below the National Primary Drinking Water Standard (2 mg/L). The first quarter 2008
<br /> barium concentration at AMW-14 (0.25 mg/L) is comparable to concentrations observed at that
<br /> well intermittently since March 1996, and is well below the National Primary Drinking Water
<br /> Standard (2 mg/L). The first quarter 2008 bicarbonate concentration at AMW-13 (520 mg/L) is
<br /> comparable to concentrations observed at that well intermittently since November 2004. The first
<br /> quarter 2008 hexavalent chromium concentration at AMW-6 (0.0054 mg/L) is comparable to
<br /> concentrations observed at that well since February 1997, and is well below the National Primary
<br /> Drinking Water Standard for chromium(0.1 mg/L). The first quarter 2008 hexavalent chromium
<br /> concentration at AMW-7 (0.0054 mg/L) is comparable to concentrations observed at that well
<br /> intermittently since July 1995, and is well below the National Primary Drinking Water Standard
<br /> for chromium(0.1 mg/L).
<br /> During the first quarter 2008 monitoring event,no VOCs were detected above the laboratory PQL
<br /> in samples collected from detection monitoring well AMW-6, AMW-7 or AMW-12. 1,1-
<br /> Dichloroethane, cis-l,2-dichloroethene, dichlorodifluoromethane, tetrachloroethene,
<br /> trichloroethene, and trichlorofluoromethane were detected above the PQL at AMW-13 during the
<br /> first quarter 2008. Dichlorodifluoromethane, tetrachloroethene and trichloroethene were detected
<br /> above the PQL at AMW-14 during the first quarter 2008.
<br /> The first quarter 2008 concentration of 1,1-dichloroethane at AMW-13 (0.51 ug/L)is comparable
<br /> to concentrations observed at that well intermittently since March 1994. The first quarter 2008
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