ARCHIVED REPORTS_2009_14 - Laserfiche WebLink

Home Browse Search

New Historical Intrawell Maximum Values During the third quarter 2009 monitoring event, the arsenic concentration measured in well MW-16 (0.0037 mg/L)nominally exceeded the previous maximum value of 0.0036 mg/L. No other historical Intrawell maximum values were exceeded during the current monitoring period. Concentration Limit Thresholds Data obtained during the third quarter 2009 monitoring period were compared to concentration limits (CLs) as specified in the RPCMP for the Forward Landfill. Given the fact that the original CL have never been updated and were calculated using data collected prior to 1994, CLs were recalculated using data collected between February 2003 and August 2008. CLs were calculated by Herst&Associates using upper tolerance limits and are included in Appendix D. Excluding suspected field/laboratory contaminants, only one CL was exceeded for arsenic in the sample collected from well MW-19 during the current monitoring period. In accordance with the RPCMP guidelines, arsenic,bicarbonate, hexavalent chromium, nitrate as nitrogen, and sulfate, are not considered impact constituents, and therefore,retesting for arsenic is not required. 2.1.5 Vadose Zone Monitoring The current vadose-zone monitoring network at the Forward Unit consists of 17 lysimeters. The lysimeter locations are shown on Figure 2-1. Each accessible lysimeter was inspected and vacuums were reset to approximately—10 to—25 inches of mercury on August 13, 2009. On September 10, 2009, the lysimeters were again checked and positive pressure was applied to evacuate the accumulated sample. As recorded in the field notes for lysimeters (Appendix C) and summarized on Table 2-5, lysimeters W-2 and LY-BGl had a sufficient volume of soil-pore liquid for sample collection. However, due to the limited sample volumes, lysimeter samples were only analyzed for select inorganic constituents and/or VOCs. As shown in Table 2-6, one VOC (bromoform)was detected above the PQL in the lysimeter samples collected during the third quarter 2009 monitoring period. 2.1.6 Surface Water Monitoring Site run-on and run-off control facilities are designed to effectively channel surface water to site stormwater/sedimentation ponds. According to the Operations Manager,no surface water was discharged from the facility during the reporting period. During the third quarter 2009, surface-water monitoring stations FSW-1 and FSW-2 were sampled on August 10, 2009. Table 2-4 summarizes the current analytical results of surface water samples collected at the Forward Unit. No VOCs were detected in the surface water samples collected from the Forward Unit during the third quarter 2009 monitoring period. D:\2009_001" _3W.aoc 6 Geologic Associates