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trichloroethene at AMW-14 (1.4 ug/L) is comparable to concentrations observed at that well
<br /> intermittently since March 1996, and is below the National Primary Drinking Water Standard (5
<br /> ug/L).
<br /> Historical data from the detection monitoring wells were analyzed for temporal trend using Sen's
<br /> Slope trend analysis. Graphs of the Sen's Slope analyses for detection monitoring wells are
<br /> included in Appendix E. The following inorganic constituents exhibited an increasing trend
<br /> according to the Sen's Slope analysis: barium at AMW-6 and AMW-14, bicarbonate at AMW-6,
<br /> AMW-7, AMW-12, and AMW-13, calcium at AMW-14, chloride at AMW-6 and AMW-7,
<br /> magnesium at AMW-14, nitrate at AMW-2, AMW-6, and AMW-7, potassium at AMW-14,
<br /> sodium at AMW-14, field specific conductance at AMW-2 and AMW-7, strontium at AMW-14,
<br /> sulfate at AMW-7, and TDS at AMW-7. None of the constituents that exhibited a statistically
<br /> significant increasing trend during the fourth quarter 2007 exceeded a concentration limit.
<br /> Although there were increasing trends for nitrate at AMW-6 and AMW-7 and field specific
<br /> conductance at AMW-7,background well AMW-2 also exhibited increasing trends for nitrate and
<br /> field specific conductance during the fourth quarter 2007 monitoring event.
<br /> Sen's Slope analysis identified decreasing trends in the following inorganic parameters: arsenic at
<br /> AMW-2 and AMW-6, calcium at AMW-12, chloride at AMW-12, magnesium at AMW-12,
<br /> nitrate at AMW-13, field specific conductance at AMW-14, strontium at AMW-12, TDS at
<br /> AMW-14,and field turbidity at AMW-2.
<br /> Of the organic constituents that were detected in detection monitoring wells during the fourth
<br /> quarter 2007 monitoring event, only cis-l,2-dichloroethene at AMW-13 exhibited an increasing
<br /> trend according to the Sen's Slope analysis. The fourth quarter 2007 concentration of cis-1,2-
<br /> dichloroethene at AMW-6 (0.60 ug/L) is well below the National Primary Drinking Water
<br /> Standard (70 ug/L). Trichloroethene at AMW-14 exhibited a statistically significant decreasing
<br /> trend according to the Sen's Slope analysis.
<br /> Piper diagrams of the first through fourth quarter 2007 results for the detection monitoring wells
<br /> are included in Appendix H. Hydrographs of the detection monitoring wells, illustrating historic
<br /> groundwater elevations, well screen elevations, and pump intake elevations, are included in
<br /> Appendix I.
<br /> 2.2 Corrective Action Monitoring
<br /> Groundwater samples were collected by ATC Associates, Inc. from the corrective action
<br /> monitoring wells (AMW-1, AMW4, AMW-5R, AMW-10, AMW-11, AMW-18, and AMW-19)
<br /> during the fourth quarter 2007 monitoring event. Corrective action monitoring well AMW-5R is
<br /> a replacement for corrective action monitoring well AMW-5. ATC Associates, Inc. reported that
<br /> corrective action monitoring well AMW-3 has been abandoned. The field and laboratory results
<br /> provided by BC Laboratories, Inc. for the fourth quarter 2007 corrective action sampling are
<br /> 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 /> 3
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