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designated as detection monitoring wells. Monitoring wells AMW-1, AMW-3, AMW-4, AMW-
<br /> 5R, AMW-10, AMW-11, AMW-18, AMW-19, and AMW-19BR are designated as corrective
<br /> action monitoring wells. Del-Tech has reported that corrective action monitoring well AMW-3
<br /> has been abandoned. Corrective action monitoring well AMW-5R is a replacement for corrective
<br /> action monitoring well AMW-5. Corrective action monitoring well AMW-19BR is a
<br /> replacement for corrective action monitoring well AMW-1913. The analytical results from
<br /> 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 /> During the second quarter 2012 monitoring event, Del-Tech collected groundwater samples from
<br /> the background well (AMW-2) and detection monitoring wells (AMW-6, AMW-7, AMW-12,
<br /> AMW-13, and AMW-14). The field results provided by Del-Tech and laboratory results
<br /> provided by BC Labs for the second quarter 2012 groundwater detection monitoring event are
<br /> summarized on Table 2.2. The historical groundwater data for the detection monitoring wells are
<br /> presented in Appendix D. Times series concentration plots of historical groundwater data for the
<br /> detection monitoring wells are presented in Appendix E. For VOCs, only those compounds that
<br /> exhibited detections at detection monitoring wells during the second quarter 2012 monitoring
<br /> event were plotted. The concentration limits presented on Table 2.2 were calculated by Herst &
<br /> Associates, Inc. from data collected through the second quarter 2012 monitoring event. The
<br /> statistical analysis calculations for detection monitoring wells are presented in Appendix E.
<br /> As presented on Table 2.2, the following constituents exceeded their respective concentration
<br /> limits during the second quarter 2012: barium at AMW-13 and AMW-14; chloride at AMW-14;
<br /> and field temperature at AMW-6.
<br /> During the second quarter 2012 monitoring event, no VOCs were detected above the laboratory
<br /> reporting limit (RL) in samples collected from detection monitoring wells AMW-2, AMW-6,
<br /> AMW-7, or AMW-12. Dichlorodifluoromethane, tetrachloroethane, and trichloroethene were
<br /> detected above the laboratory RL at AMW-13. Tetrachloroethene was detected above the
<br /> laboratory RL at AMW-14.
<br /> Historical data from the detection monitoring wells were analyzed for temporal trends using
<br /> Mann-Kendall / Sen's Slope trend analysis. Graphs and summary tables of the Mann-Kendall /
<br /> Sen's Slope analyses for detection monitoring wells are presented in Appendix E. For
<br /> constituents whose historical data consist primarily of non-detects (carbonate alkalinity, oil and
<br /> grease, volatile petroleum hydrocarbons, and VOCs), trend evaluation was performed on data
<br /> from the earliest detection through the present. Wells with no historical detections for a
<br /> constituent were not evaluated for trends.
<br /> Mann-Kendall / Sen's Slope analysis identified significant increasing statistical trends for the
<br /> following inorganic constituents: barium AMW-6 and AMW-14; bicarbonate alkalinity at AMW-
<br /> 2, AMW-7, and AMW-13; calcium at AMW-7 and AMW-14; chloride at AMW-6, AMW-7 and
<br /> AMW-14; hexavalent chromium at AMW-14; magnesium at AMW-6, AMW-7, and AMW-14;
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