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AMW-7, and AMW-13, calcium at AMW-7 and AMW-14, chloride at AMW-6 and AMW-7,
<br /> magnesium at AMW-7 and AMW-14, nitrate at AMW-2, AMW-6, and AMW-7, potassium at
<br /> AMW-14, sodium at AMW-14, field specific conductance at AMW-2 and AMW-7, strontium at
<br /> AMW-6 and AMW-14, sulfate at AMW-7, and TDS at AMW-7. Only one constituent exhibited
<br /> a statistically significant increasing trend during the first quarter 2009 and also exceeded its
<br /> concentration limit: dissolved barium at AMW-14.
<br /> Sen's Slope analysis identified decreasing trends in the following inorganic parameters: arsenic at
<br /> AMW-2, calcium at AMW-12, chloride at AMW-12, magnesium at AMW-12, nitrate at AMW-
<br /> 13,potassium at AMW-12, strontium at AMW-12,and field turbidity at AMW-2 and AMW-14.
<br /> Of the organic constituents that were detected in detection monitoring wells during the first
<br /> quarter 2009 monitoring event, only one exhibited a significant increasing trend according to the
<br /> Sen's Slope analysis: cis-l,2-dichloroethene at AMW-13. One organic constituent detected in a
<br /> detection monitoring well during the first quarter 2009 exhibited a significant decreasing trend:
<br /> dichlorodifluoromethane at AMW-14.
<br /> 2.2 Corrective Action Monitoring
<br /> Groundwater samples were collected by ATC Associates, Inc. from the corrective action
<br /> monitoring wells (AMW-1, AMW-4, AMW-5R, AMW-10, AMW-11, AMW-18, and AMW-19)
<br /> during the first quarter 2009 monitoring event. Corrective action monitoring well AMW-5R is a
<br /> replacement for corrective action monitoring well AMW-5. The field results provided by ATC
<br /> Associates,Inc.and laboratory results provided by BC Laboratories, Inc. for the first quarter 2009
<br /> corrective action sampling are summarized on Table 2.3.
<br /> VOCs have been consistently detected in samples from corrective action monitoring wells AMW-
<br /> 1, AMW-4, AMW-10, and AMW-11. AMW-5/5R, AMW-18, and AMW-19 have previously
<br /> exhibited sporadic VOC detections.
<br /> The historical groundwater data for the corrective action monitoring wells are presented in
<br /> Appendix F. The data are graphed on time series concentration plots, included in Appendix G.
<br /> For VOCs, only those VOCs that exhibited detections for the first quarter 2009 monitoring event
<br /> were plotted.
<br /> Historical data from the corrective action monitoring wells from March 1994 to the present were
<br /> analyzed for temporal trend using Sen's Slope trend analysis. Graphs of the Sen's Slope analyses
<br /> for corrective action monitoring wells are included in Appendix G. Table 2.4 summarizes the
<br /> results of the corrective action monitoring well trend analysis. The following inorganic
<br /> constituents exhibited an increasing trend according to the Sen's Slope analysis:barium at AMW-
<br /> 1 and AMW-5R,bicarbonate at AMW-1, AMW-5R, and AMW-18, chloride at AMW-5R,nitrate
<br /> at AMW-4 and AMW-5R, pH at MW-5R, sodium at AMW-5R, field specific conductance at
<br /> AMW-1 and AMW-5R, strontium at AMW-18, sulfate at AMW-5R and AMW-10, TDS at
<br /> AMW-5R,and field turbidity at AMW-5R,AMW-10,and AMW-19.
<br /> The first quarter 2009 concentration of barium at AMW-1 (0.28 mg/L) is comparable to
<br /> concentrations observed at that well intermittently since February 2004, and is well below the
<br /> National Primary Drinking Water Standard (2 mg/L). The first quarter 2009 concentration of
<br /> barium at AMW-5R (0.33 mg/L) is comparable to concentrations observed at that well since
<br /> August 2003,and is well below the National Primary Drinking Water Standard(2 mg/L).
<br /> 3
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