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2017 Corrective Action Evaluation Report-Austin Road Unit Forward Landfill Evaluation Monitoring Program (EMP)/Corrective Action Program (CAP) wells that were completed downgradient of the ARU in 2011 were also used in the TVOC mass calculation. Tables 2 through 5 present a quarterly summary of the VOC groundwater monitoring results from the monitoring period, including the TVOC concentration for each well. Estimated (trace) detections of VOCs between the laboratory reporting limit (RL) and method detection limit (MDL) are also presented on Tables 2 through 5, but such trace detections are not included in the calculation of TVOC concentrations. Of note, suspected and/or confirmed field/laboratory contaminants for acetone and methyl ethyl ketone that were not repeated in subsequent sampling events were also not included in the TVOC calculations. In an August 19, 2005 letter, the RWQCB specified that future Annual Corrective Action Evaluation Reports shall include: • A discussion of the landfill cover, including any performance issues from the previous year; A summary and discussion of the previous year's monitoring data from the facility's landfill gas monitoring system and landfill gas extraction system; A comparison of the previous year's groundwater monitoring results to computer simulations originally presented in the August 6, 2001 Revised Engineering Feasibility Study, and • A discussion of the overall corrective action progress, including any proposed enhancements to the program. The RWQCB later incorporated these requirements and quarterly groundwater potentiometric maps into Section B.5 of the M&RP. These requirements are addressed in Sections 4, 5, 6, and 7, respectively, of this report. 1.0 TVOC MASS Isoconcentration maps of groundwater TVOC concentrations for the monitoring period are presented in Figures 1 through 4. Consistent with the Evaluation Procedures Report, these maps utilize a contour interval of 25 µg/L and do not include contouring for concentrations less than 1 µg/L. Of note, the isoconcentration maps presented herein included all of the ARU groundwater monitoring wells including the 18 EMP/CAP wells completed in 2011. For each quarter,the TVOC mass was estimated using the following procedures: • 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 pg/L and 50 µg/l- contours would be 37.5 ltg/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. Project No 5017.1030 1 2017 Corrective Action Evaluation Report-Austin Road Unit 2 Forward Landfill