ARCHIVED REPORTS_2010_12 - Laserfiche WebLink

Home Browse Search

and TDS at AMW-6 and AMW-7. Carbonate at AMW-2 exhibited an apparent increasing trend according to the Mann-Kendall/Sen's Slope analysis,but this trend is due to a historical increase in the laboratory PQL. There was only one constituent that exhibited a statistically significant increasing trend during the second quarter 2010 and also exceeded a concentration limit: barium at AMW-14. As described above, the second quarter 2010 barium concentration at AMW-14 (0.25 mg/L) is comparable to concentrations observed at that well since August 2006, and is well below the National Primary Drinking Water Standard(2 mg/L). Mann-Kendall / Sen's Slope analysis identified decreasing trends in the following inorganic parameters: arsenic at AMW-2, barium at AMW-4 and AMW-12, bicarbonate at AMW4, calcium at AMW4 and AMW-12, chloride at AMW-4 and AMW-12,magnesium at AMW-4 and AMW-12, nitrate at AMW-13, field pH at AMW-2, potassium at AMW-12, strontium at AMW- 12, and field turbidity at AMW-2 and AMW-14. None of the VOCs that were detected in detection monitoring wells during the second quarter 2010 monitoring event exhibited a significant increasing trend according to the Mann-Kendall / Sen's Slope analysis. One VOC that was detected in a detection monitoring well during the second quarter 2010 exhibited a significant decreasing trend: trichloroethene at AMW-14. 1,2- Dichloropropane and dichlorodifluoromethane at AMW-14 exhibited apparent decreasing trends according to the Mann-Kendall/Sen's Slope analysis, but this trend is due to historical decreases in the laboratory PQLs. 2.2 Corrective Action Monitoring During the second quarter 2010 monitoring event,Del-Tech collected groundwater samples from corrective action monitoring wells (AMW-1, AMW-5R, AMW-10, AMW-11, AMW-18, AMW- 19, and AMW-1913R). Corrective action monitoring well AMW-5R is a replacement for corrective action monitoring well AMW-5. Corrective action monitoring well AMW-19BR is a replacement for corrective action monitoring well AMW-19B. The field results provided by Del- Tech and laboratory results provided by BC Laboratories, Inc. for the second quarter 2010 corrective action monitoring event are summarized on Table 2.3. The historical groundwater data for the corrective action monitoring wells are presented in Appendix F. Times series concentration plots of historical groundwater data for the detection monitoring wells are presented in Appendix G. For VOCs, only those compounds that exhibited detections at corrective action monitoring wells during the second quarter 2010 monitoring event were plotted. VOCs have been consistently detected in samples from corrective action monitoring wells AMW- 1,AMW-4,AMW-10, and AMW-11. Wells AMW-5/5R,AMW-18,AMW-19,and AMW-19BR have previously exhibited sporadic VOC detections. Historical data from the corrective action monitoring wells from March 1994 to the present were analyzed for temporal trends using Mann-Kendall / Sen's Slope trend analysis. Graphs and summary tables of the Sen's Slope analyses for corrective action monitoring wells are presented in Appendix G. Table 2.4 summarizes the results of the corrective action monitoring well trend analysis. The following inorganic constituents exhibited an increasing trend according to the Mann-Kendall/ Sen's Slope analysis: barium at AMW-1 and AMW-5R, bicarbonate at AMW-1, AMW-5R, and AMW-18, chloride at AMW-5R, nitrate at AMW-4 and AMW-5R, field pH at AMW-5R, sodium at AMW-5R, field specific conductance at AMW-1 and AMW-5R, strontium at AMW-18, sulfate at AMW-5R and AMW-10, TDS at AMW-5R, and field turbidity at AMW- 3