ARCHIVED REPORTS_2007_18 - Laserfiche WebLink

Home Browse Search

intermittently since March 1996. The second quarter 2007 concentration of trichloroethene at AMW-14 (1.1 ug/L) is comparable to concentrations observed at that well intermittently since March 1996,and is below the National Primary Drinking Water Standard(5 ug/L). Historical data from the detection monitoring wells were analyzed for temporal trend using Sen's Slope trend analysis. Graphs of the Sen's Slope analyses for detection monitoring wells are included in Appendix E. The following inorganic constituents exhibited an increasing trend according to the Sen's Slope analysis: barium at AMW-6, bicarbonate at AMW-6, AMW-7, AMW-12, and AMW-13, calcium at AMW-14, chloride at AMW-6 and AMW-7, magnesium at AMW-14, nitrate at AMW-2, AMW-6, and AMW-7, potassium at AMW-14, sodium at AMW- 14, field specific conductance at AMW-2 and AMW-7, strontium at AMW-14, and total dissolved solids (TDS) at AMW-7. None of the constituents that exhibited a statistically significant increasing trend during the second quarter 2007 exceeded a concentration limit. Although there were increasing trends for nitrate at AMW-6 and AMW-7 and field specific conductance at AMW-7,background well AMW-2 also exhibited increasing trends for nitrate and field specific conductance during the second quarter 2007 monitoring event. Sen's Slope analysis identified decreasing trends in the following inorganic parameters: arsenic at AMW-2, calcium at AMW-12, chloride at AMW-12 and AMW-14, magnesium at AMW-12, nitrate at AMW-13, potassium at AMW-13, field specific conductance at AMW-14, strontium at AMW-12, sulfate at AMW-6, total dissolved solids (TDS) at AMW-14, and field turbidity at AMW-2. Of the organic constituents that were detected above the laboratory PQL in detection monitoring wells during the second quarter 2007 monitoring event, none exhibited an increasing trend according to the Sen's Slope analysis. Tetrachloroethene and trichloroethene at AMW-14 exhibited statistically significant decreasing trends according to the Sen's Slope analysis. 2.2 Corrective Action Monitoring Groundwater samples were collected by ATC Associates, Inc. from the corrective action monitoring wells (AMW-1, AMW-4, AMW-10, AMW-11, AMW-18, AMW-19) during the second quarter 2007 monitoring event. ATC Associates, Inc. reported that corrective action monitoring well AMW-3 has been abandoned, and that corrective action monitoring well AMW- 5 could not be sampled during the second quarter 2007 due to a nonfunctional pump lodged in the well. The field and laboratory results provided by BC Laboratories, Inc. for the second quarter 2007 corrective action sampling are summarized on Table 2.3. VOCs have been consistently detected in samples from corrective action monitoring wells AMW- 1, AMW-4, AMW-10, and AMW-11. AMW-5, AMW-18, and AMW-19 have previously exhibited sporadic VOC detections. No VOCs have been detected in samples from AMW-3 since 1990. The historical groundwater data for the corrective action monitoring wells are presented in Appendix F. The data are graphed on time series concentration plots, included in Appendix G. For VOCs, only those VOCs that exhibited detections for the second quarter 2007 monitoring event were plotted. Historical data from the corrective action monitoring wells from March 1994 to the present were analyzed for temporal trend using Sen's Slope trend analysis. Graphs of the Sen's Slope analyses for corrective action monitoring wells are included in Appendix G. Table 2.4 summarizes the 3