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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, 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 first quarter 2011 monitoring event, Del-Tech collected groundwater samples from the
<br /> 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 TestAmerica for the first quarter 2011 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 first quarter 2011 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 first quarter 2011 monitoring event. The
<br /> statistical analysis calculations for detection monitoring wells are presented in Appendix E.
<br /> Information on the development of the concentration limits can be found in the Fourth
<br /> Quarter/Annual 1999 Monitoring Report, Austin Road Landfill, prepared by CH2M Hill in
<br /> January 2000. A copy of the statistical analysis methodology is presented in Appendix C.
<br /> As presented on Table 2.2, the following constituents exceeded their respective concentration
<br /> limits during the first quarter 2011: barium at AMW-13 and AMW-14. The hexavalent
<br /> chromium concentrations at AMW-7 (0.0054 mg/L), AMW-12 (0.0081 mg/L), and AMW-14
<br /> (0.0081 mg/L) exceeded the concentration limit of 0.004865 mg/L, but the observed
<br /> concentrations are trace(estimated)values below the laboratory RL.
<br /> During the first quarter 2011 monitoring event, no VOCs were detected above the laboratory RL
<br /> in samples collected from detection monitoring wells AMW-2, AMW-6, AMW-7, or AMW-12.
<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.
<br /> Mann-Kendall / Sen's Slope analysis identified significant increasing statistical trends in 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 and AMW-7,
<br /> hexavalent chromium at AMW-14, magnesium at AMW-7 and AMW-14, nitrate at AMW-2,
<br /> AMW-6, AMW-7, and AMW-14, potassium at AMW-14, sodium at AMW-14, field specific
<br /> conductance at AMW-2, AMW-6, and AMW-7, strontium at AMW-6 and AMW-14, sulfate at
<br /> AMW-7 and AMW-14, and TDS at AMW-6 and AMW-7. Carbonate at AMW-2,AMW-12, and
<br /> AMW-13 exhibited apparent increasing trends according to the Mann-Kendall / Sen's Slope
<br /> analysis,but these trends are due to a historical increase in the laboratory RL.
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