ARCHIVED REPORTS_2009_13 - Laserfiche WebLink

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designated as detection monitoring wells. Monitoring wells AMW-1, AMW-3, AMW-4, AMW- 5R, AMW-10, AMW-11, AMW-18, and AMW-19 are designated as corrective action monitoring wells. Corrective action monitoring well AMW-5R is a replacement for corrective action monitoring well AMW-5. The analytical results from samples collected at the corrective action wells are used to evaluate improvements in groundwater quality as a result of previously implemented corrective action measures. ATC Associates, Inc. reported that corrective action monitoring well AMW-3 has been abandoned. Groundwater samples are scheduled to be analyzed quarterly for field parameters (groundwater elevation, pH, specific conductance, temperature, and turbidity) and monitoring parameters (arsenic, barium, bicarbonate, calcium, carbonate, chloride, gasoline-range petroleum hydrocarbons, hexavalent chromium, magnesium, nitrate, oil and grease, potassium, sodium, strontium, sulfate,TDS, and VOCs). 2.1 Detection Monitoring Groundwater samples were collected from the background well (AMW-2) and detection monitoring wells (AMW-6, AMW-7, AMW-12, AMW-13, and AMW-14) during the second quarter 2009 monitoring event. The field results provided by ATC Associates, Inc. and laboratory results provided by BC Laboratories, Inc. for the second quarter 2009 detection monitoring sampling event are summarized on Table 2.2. The historical groundwater data for the detection monitoring wells are presented in Appendix D. The data are graphed on time series concentration plots, presented in Appendix E. For VOCs, only those compounds that exhibited detections for the second quarter 2009 monitoring event were plotted. The concentration limits presented on Table 2.2 were calculated by Herst & Associates, Inc. from data collected through the second quarter 2009 monitoring event. The statistical analysis calculations for detection monitoring wells are included in Appendix E. Information on the development of the concentration limits can be found in the Fourth Quarter/Annual 1999 Monitoring Report, Austin Road Landfill, prepared by CH2M Hill in January 2000. A copy of the statistical analysis methodology is presented in Appendix C. During the second quarter 2009 monitoring event, barium at AMW-13 and hexavalent chromium at AMW-7 exceeded their respective concentration limits. The second quarter 2009 barium concentration at AMW-13 (0.26 mg/L) is comparable to concentrations observed at that well consistently since May 1995, and is well below the National Primary Drinking Water Standard(2 mg/L). The second quarter 2009 hexavalent chromium concentration at AMW-7 (0.0055 mg/L) is comparable to concentrations observed at that well intermittently since July 1995, and is well below the National Primary Drinking Water Standard for chromium(0.1 mg/L). During the second quarter 2009 monitoring event, no VOCs were detected above the laboratory PQL in samples collected from detection monitoring wells AMW-2, AMW-7, or AMW-12. Tetrachloroethene was detected above the PQL at AMW-6. Tetrachloroethene and trichloroethene were detected above the PQL at AMW-13. Tetrachloroethene was detected above the PQL at AMW-14. The second quarter 2009 concentration of tetrachloroethene at AMW-6 (0.71 ug/L) is comparable to concentrations observed at that well intermittently since September 1996, and is below the National Primary Drinking Water Standard (5 ug/L). The second quarter 2009 concentration of tetrachloroethene at AMW-13 (3.6 ug/L) is comparable to concentrations observed at that well 2