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designated as detection monitoring wells. Monitoring wells AMW-I, 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-19B. 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 fourth 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 fourth 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 />Ank.
<br />exhibited detections at detection monitoring wells during the fourth 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 fourth 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 fourth quarter 2012: barium at AMW-12, AMW-13, and AMW-14; chloride at
<br />AMW-12 and AMW-14; hexavalent chromium at AMW-6 and AMW-7; and field temperature at
<br />AMW-7.
<br />During the fourth 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 was detected at the laboratory RL and
<br />tetrachloroethene and trichloroethene were detected above the laboratory RL at AMW-13.
<br />Tetrachloroethene was detected above the 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-6, AMW-7, and AMW-13; calcium at AMW-7 and AMW-14; chloride at AMW-6,
<br />N
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