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2016 Corrective Action Evaluation Report - Austin Road Unit <br />Forward Landfill <br />the monitoring period. TVOC concentrations at shallow corrective action well AMW-19 <br />exceeded its TL of 4.04 pg/L during the fourth quarter 2015 (6.20 µg/L), first quarter 2016 <br />(17.00 pg/L), and second quarter 2016 (18.00 Itg/L); and the TVOC concentration at deep <br />corrective action well AMW-19BR exceeded its TL of 22.87 pg/L during the first quarter 2016 <br />(25.58 pg/L). These exceedances were the result of increasing tetrachloroethene (PCE) <br />concentrations. <br />4.0 CONDITION OF LANDFILL COVER <br />During the monitoring period, there were no significant problems reported with landfill cover <br />that resulted in exposed waste. Minor erosional issues were addressed by placement and <br />compaction of soil material. No leachate seeps were reported and no notices of violation <br />(NOVs) were issued to the facility for cover -related issues during the monitoring period. <br />5.0 LANDFILL GAS MONITORING RESULTS <br />At municipal solid waste (MSW) landfills, such as Forward Landfill, MSW is heterogeneous, and <br />therefore, patterns of LFG compounds and their concentrations can vary within the landfill. <br />Typically MSW LFG composition consists of methane, carbon dioxide, oxygen, nitrogen, and <br />non -methane organic compound (NMOL) concentrations. The NMOC concentrations in LFG are <br />a function of the types and age of waste in the landfill and the extent of the reactions that <br />produce various compounds from the anaerobic decomposition of waste. As demonstrated by <br />the results of the TO -15 testing, the NMOC concentrations in LFG vary across the landfill from <br />well to well. The concentrations varying from point to point with no distinct pattern is <br />consistent with the expectations for the heterogeneous environment of an MSW landfill. <br />The second semiannual 2016 TO -15 sampling event demonstrated that NMOCs were present in <br />the LFG extraction wells, consistent with expectations for an MSW landfill. In the event of an <br />uncontrolled release, there is the potential for LFG to impact the unsaturated zone; however, <br />perimeter LFG probes have been installed in accordance with Title 27 of the California Code of <br />Regulations and demonstrate continued compliance with the requirements. In addition, the <br />combined LFG collection system, the Ameresco landfill gas -to -energy plant and the Forward <br />LFG flaring system are operating at 75% of full capacity and in compliance with regulations. The <br />LFG collection and combustion system is upgraded on a routine basis to optimize LFG collection. <br />The potential for LFG impacts on the unsaturated zone are therefore being mitigated through <br />source control measures. If it is determined that additional mitigation is needed, or if impacts <br />are observed, the LFG collection system can be increased to extract additional LFG. In <br />conclusion, the existing system is optimized to maintain continued compliance with both State <br />and Federal Air standards, but if site conditions change, or impacts are observed, the current <br />system has back up capacity to maintain compliance and continue or increase source control <br />measures, as needed. The gas collection and control system at the Forward Landfill complex <br />includes 194 extraction wells, a flare for thermal destruction (Flare A-2), a backup flare (Flare A- <br />1), and a methane gas recovery facility that generates electricity. <br />isProject No. 2016.0007 1 2016 Corrective Action Evaluation Report - Austin Road Unit 4 <br />Forward Landfill <br />