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Corral Hollow Landfill - 2 - 8 January 2023 established offsite and concentrations of TCFM are low-level in well MW-9A, further delineation of the shallow aquifer is not being proposed at this time. The installation of one proposed deep aquifer well is an appropriate step to evaluate the deep zone aquifer. Most recent TCFM concentrations reported in deep well MW-12 are below the PQL and are not detected in offsite wells MW-10A or-11A. However, the EMP does not provide a contingency plan to step out if after installation and initial groundwater sampling of the new well, TCFM concentrations continue to be detected. To meet the requirements of the EMP, the Discharger may have to step out from the proposed deep well to delineate the TCFM plume further downgradient. This will be determined once the well has been installed, developed, and sampled. In addition, the Discharger is proposing to conduct an evaluation of existing LFG extraction wells and flare header station by collecting LFG samples and analyze those samples by TO-15. Collection of LFG samples from specific extraction wells are being conducted to support an analysis of different LFG removal systems such as, activated carbon treatment. An activated carbon treatment system is being considered due to low quality, low volume of LFG produced and lack of continuous operation of the current LFG flare system. According to the Discharger, an activated carbon treatment system can run continuously without methane. Regardless, the method of destroying landfill gases via thermal destruction or carbon absorption will need concurrence from the local Air District. Until the change occurs, the existing system performance should be continuously optimized to comply with item 2c of the CDO . The Discharger has proposed to prepare an Engineered Feasibility Study (EFS) in accordance with Title 27, section 20430 by 5 February 2024. Well Installation Work Plan The Discharger has proposed to install one deep aquifer monitoring well approximately 500 feet downgradient (southeast) of well MW-12. The proposed well will be drilled using a sonic drill rig. The borehole will be 12-inches in diameter to a depth between 370 and 380 feet below ground surface (bgs). The well casing will consist of 4-inch diameter schedule 80 polyvinyl chloride (PVC) casing with 20-feet of 0.020-inch factory slotted well screen. The well will be completed at the surface with a five foot by five foot cement pad and bollards. San Joaquin Environmental Health will oversee the well construction. This well will be installed to delineate the TCFM concentrations found in well MW-12. By 5 February 2024 the Discharger shall submit their proposed Engineered Feasibility Study (EFS) in accordance with Title 27, section 20430. The EFS and recommendations to enhance LFG recovery will be supported by the findings of the proposed well installation and sampling, and the additional LFG sampling program. If the proposed well installation and sampling indicate that further delineation of the deep zone is warranted, then a work plan shall be submitted within 45 days following the receipt and evaluation of the laboratory analytical results. If initial groundwater sampling indicates TCFM or other VOCs are delineated, then the newly installed well shall be monitored and sampled in accordance with the Monitoring and Reporting Program (MRP) established under the current WDRs. In addition, the EFS shall propose warranted changes or enhancements to the LFG system to address persistent LFG detected in the groundwater monitoring wells.