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2.0 Groundwater Monitoring
<br /> Groundwater samples were collected by Bryan A. Stirrat & Associates during the third quarter
<br /> 2006 monitoring event from the detection monitoring and corrective action wells at the site.
<br /> Monitoring well AMW-2, which is upgradient from the landfill, is the designated background
<br /> well. Monitoring wells AMW-6, AMW-7, AMW-12, AMW-13, and AMW-14 are currently
<br /> designated as detection monitoring wells. Monitoring wells AMW-1, AMW-3, AMW-4, AMW-
<br /> 5, AMW-10, AMW-11, and AMW-19 are designated as corrective action monitoring. The
<br /> analytical results from samples collected at the corrective action wells are used to evaluate
<br /> improvements in groundwater quality as a result of previously implemented corrective action
<br /> measures.
<br /> Bryan A. Stirrat reported that corrective action monitoring well MW-3 has been destroyed, and
<br /> that corrective action monitoring well MW-5 could not be sampled during the third quarter 2006
<br /> due to a nonfunctional pump lodged in the well.
<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 /> Groundwater samples were collected from the background well ( -2) and detection
<br /> monitoring wells (AMW-6, AMW-7, AMW-12, AMW-13, and AMW-14) during the third
<br /> quarter 2006 monitoring event. The field and laboratory results provided by BC Laboratories,
<br /> Inc. for the third quarter 2006 detection monitoring sampling are summarized on Table 2.2. The
<br /> historical groundwater data for the detection monitoring wells are presented in Appendix D. The
<br /> data are graphed on time series concentration plots, included in Appendix E. For VOCs, only
<br /> those compounds that exhibited detections for the third quarter 2006 monitoring event were
<br /> plotted. The concentration limits presented on Table 2.2 were calculated by Herst & Associates,
<br /> Inc. from data collected through the third quarter 2006 monitoring event. The statistical analysis
<br /> calculations for detection monitoring wells are included in Appendix E. A copy of the statistical
<br /> analysis methodology is included in Appendix C.
<br /> During the third quarter 2006 monitoring event, barium at AMW-13, carbonate at AMW-7,
<br /> hexavalent chromium at AMW-7, field pH at AMW-7,AMW-12, and AMW-14, and turbidity at
<br /> AMW-14 exceeded their respective concentration limits. The third quarter 2006 barium
<br /> concentration at AMW-13 (0.25 mg/L) is comparable to concentrations observed at that well
<br /> since May 1995,and is well below the National Primary Drinking Water Standard(2 mg/L). The
<br /> third quarter 2006 carbonate concentration at AMW-7 (17 mg/L) is comparable to concentrations
<br /> observed at that well intermittently since August 1993. The third quarter 2006 hexavalent
<br /> chromium concentration at AMW-7 (0.006 mg/L) is comparable to concentrations observed at
<br /> that well intermittently since February 1997. The third quarter 2006 pH value at AMW-7 (8.5) is
<br /> comparable to or lower than values observed at that well intermittently since August 1991. The
<br /> third quarter 2006 pH value at AMW-12 (8.4) is higher than values previously observed at that
<br /> well. The third quarter 2006 pH value at AMW-14 (8.5) is higher than values previously
<br /> observed at that well. The third quarter 2006 field turbidity value at AMW-14 (190 NTUs) is
<br /> higher than values previously observed at that well.
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