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AMW-2, which is upgradient from the landfill, is the designated background well. Monitoring
<br /> wells AMW-6, AMW-7, AMW-12, AMW-13, and AMW-14 are currently designated as
<br /> 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, and that corrective action monitoring well AMW-4 has been destroyed. Corrective
<br /> action monitoring well AMW-5R is a replacement for corrective action monitoring well AMW-5.
<br /> Corrective action monitoring well AMW-19BR is a replacement for corrective action monitoring
<br /> well AMW-19B. The analytical results from samples collected at the corrective action wells are
<br /> used to evaluate improvements in groundwater quality as a result of previously implemented
<br /> 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 2010 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 BC Labs for the first quarter 2010 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 2010 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 2010 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 /> During the first quarter 2010 monitoring event, barium at AMW-13 and AMW-14 exceeded its
<br /> concentration limit. The first quarter 2010 barium concentration at AMW-13 (0.26 mg/L) is
<br /> comparable to concentrations observed at that well since May 1995, and is well below the
<br /> National Primary Drinking Water Standard (2 mg/L). The first quarter 2010 barium
<br /> concentration at AMW-14 (0.26 mg/L) is comparable to concentrations observed at that well
<br /> since August 2006, and is well below the National Primary Drinking Water Standard(2 mg/L).
<br /> During the first quarter 2010 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. Tetrachloroethene and trichloroethene were detected above the RL at
<br /> AMW-13. Tetrachloroethene was detected above the RL at AMW-14.
<br /> The first quarter 2010 concentration of tetrachloroethene at AMW-13 (4.9 ug/L) is comparable to
<br /> historical concentrations observed at that well, and is below the National Primary Drinking Water
<br /> Standard (5 ug/L). The first quarter 2010 concentration of tetrachloroethene at AMW-14 (1.1
<br /> ug/L) is comparable to historical concentrations observed at that well, and is below the National
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