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detection monitoring wells. Monitoring wells AMW-1, AMW-3, AMW-4, AMW-5R, AMW-10,
<br />AMW-11, AMW-18, AMW-19, and AMW-19BR are designated as corrective action monitoring
<br />wells. Del -Tech has reported that corrective action monitoring well AMW-3 has been
<br />abandoned. Corrective action monitoring well AMW-5R is a replacement for corrective action
<br />monitoring well AMW-5. Corrective action monitoring well AMW-19BR is a replacement for
<br />corrective action monitoring well AMW-1913. The analytical results from samples collected at
<br />the corrective action wells are used to evaluate improvements in groundwater quality as a result
<br />of previously implemented corrective action measures.
<br />Groundwater samples are scheduled to be analyzed quarterly for field parameters (groundwater
<br />elevation, p, 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 Monitorilfl-
<br />During the third 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 third 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 third quarter 2012 monitoring event
<br />were plotted. The concentration limits presented on Table 2.2 were calculated by Herst &
<br />Associates, Inc. from data collected through the third 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 third quarter 2012: barium at AMW-12, AMW-13, and AMW-14; chloride at
<br />AMW-12 and AMW-14; hexavalent chromium at AMW-7; and field temperature at AMW-7 and
<br />AMW-14.
<br />During the third 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-7, or
<br />AMW-12. Tetrachloroethene was detected above the laboratory RL at AMW-6.
<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-7, and AMW-13; calcium at AMW-7 and AMW-14; chloride at AMW-6, AMW-7 and
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