ARCHIVED REPORTS_2017_3 - Laserfiche WebLink

Home Browse Search

2016 Corrective Action Evaluation Report - Austin Road Unit Forward Landfill The TVOC mass between each pair of isoconcentration contours was first estimated by multiplying the average TVOC concentration between those contours by the assumed aquifer thickness and porosity. (For example, the average TVOC concentration between the 25 µg/L and 50 µg/L contours would be 37.5 µg/L.) Consistent with the Evaluation Procedures Report, the aquifer thickness was assumed to be 40 feet and the aquifer porosity was assumed to be 0.25. The TVOC masses corresponding to all contour pairs on a given quarter's isoconcentration map were then summed to estimate the total, plume -wide TVOC mass for that quarter. Tables 6 through 9 summarize the quarterly TVOC mass estimation calculations for the monitoring period; the historical TVOC masses for the facility are summarized on Table 11; and the corresponding quarterly groundwater potentiometric maps are presented in Appendix A. The TVOC mass for each quarter was compared to the TVOC mass TL of 789.5 kg. During the monitoring period, the calculated quarterly TVOC mass did not exceed the TL. 2.0 TVOC MASS TREND The estimated TVOC masses for the past four quarters were reviewed for increasing trends. TVOC mass has not increased for four consecutive quarters at any time in the past year. As discussed in Section 1.0, the TVOC mass calculations performed for this monitoring period also included the 18 EMP/CAP wells that were not included in previous annual reports. As a result, the quarterly TVOC mass calculations summarized in Table 11 are significantly greater than in previous Annual Corrective Action Evaluation Reports. In order to evaluate if any significant change has occurred in the TVOC concentrations and/or TVOC mass, analytical data from the second quarter 2014 using the additional 18 EMP/CAP wells, was compared to the results calculated during the current monitoring period. A comparison of the isoconcentration map for groundwater TVOC concentrations during the second quarter 2014 (Figure 5) with the current results (Figures 1 through 4) depicts a similar VOC plume geometry, and the TVOC mass calculation of 196.3 kg (Table 10) is within the range of values calculated during the current monitoring period (Table 11). Of note, the second quarter 2014 was the first monitoring event that the additional 18 EMP/CAP wells were sampled. 3.0 INDIVIDUAL WELL TVOC CONCENTRATIONS The TVOC concentrations observed at individual wells for the past four quarters are presented on Tables 2 through 5 and summarized on Table 12. A time series charts for TVOC mass and individual well TVOC concentrations, and a historical database summary are presented in Appendix B. The individual TVOC concentrations for each quarter were compared to the established TVOC concentration TLs. As shown on Table 12, there were four individual well TL exceedances during ® Project No. 2016.0007 12016 Corrective Action Evaluation Report - Austin Road Unit 3 Forward Landfill