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designated as detection monitoring wells. Monitoring wells AMW-1, AMW-3, AMWA, AMVV- .
<br />5, AMW-10, and AMW-11 are designated as corrective action monitoring. The analytical results
<br />from samples collected at the corrective action wells are used to evaluate improvements in
<br />groundwater quality as a result of previously implemented corrective action measures.
<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 second
<br />quarter 2006 monitoring event. Bryan A. Stirrat did not report a field turbidity result for
<br />monitoring well AMW-12 during the second quarter 2006. The field and laboratory results
<br />provided by BC Laboratories, Inc. for the second quarter 2006 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 second quarter
<br />2006 monitoring event were plotted. The concentration limits presented on Table 2.2 were
<br />calculated by Herst & Associates, Inc. from data collected through the second quarter 2006
<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 second quarter 2006 monitoring event, barium at AMW-13, bicarbonate at AMW-13,
<br />hexavalent chromium at AMW-6, AMW-7, and AMW-13, and field temperature at AMW-6 and
<br />AMW-7 exceeded their respective concentration limits. The second quarter 2006 barium
<br />concentration at AMW-13 (0.27 mg/L) is comparable to concentrations observed at that well
<br />since May 1995, and is well below the National Primary Drinking Water Standard (2 mg/L). The
<br />second quarter 2006 bicarbonate concentration at AMW-13 (530 mg/L) is comparable to
<br />concentrations observed at that well intermittently since February 2004. The second quarter 2006
<br />hexavalent chromium concentration at AMW-6 (0.0057 mg/L) is comparable to concentrations
<br />observed at that well intermittently since February 1997. The second quarter 2006 hexavalent
<br />chromium concentration at AMW-7 (0.0079 mg/L) is comparable to concentrations observed at
<br />that well intermittently since August 2003. The second quarter 2006 hexavalent chromium
<br />concentration at AMW-13 (0.007 mg/L) is higher than concentrations previously observed at that
<br />well. The second quarter 2006 field temperature values at AMW-6 (23 °C) and AMW-7 (24 °C)
<br />are comparable to values observed at those wells intermittently since June 1996.
<br />During the second quarter 2006 monitoring event, no VOCs were detected above the laboratory
<br />PQL in samples collected from detection monitoring wells AMW-2, AMW-6, or AMW-7. 1,2-
<br />Dichloropropane, dichlorodifluoromethane, tetrachloroethene, and trichloroethene were detected
<br />above the PQL at AMW-12 during the second quarter 2006. cis-1,2-Dichloroethene,
<br />dichlorodifluoromethane, tetrachloroethene, and trichloroethene were detected above the PQL at
<br />AMW-13 during the second quarter 2006 monitoring event. 1,2-Dichloropropane,
<br />dichlorodifluoromethane, tetrachloroethene, and trichloroethene were detected above the PQL at
<br />AMW-14 during the second quarter 2006 monitoring event.
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