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Project No. AU25.1274 | PCPCMP Foothill Sanitary Landfill 7 <br />September 2025 <br />The first phase of an LFG control system was installed in 2006, which included nine vertical LFG <br />wells and the flare station. This initial system has been expanded and currently consists of 39 <br />vertical extraction wells and 17 horizontal collectors. Additional horizontal collectors and vertical <br />wells will be added as the landfill is developed. The configuration and extent of the final landfill <br />gas system is shown on Figure 6. <br />It is assumed that all LFG system components are installed in projects prior to the closure project <br />and that no construction costs for the LFG system will be incurred during closure. Costs for <br />operation and maintenance of the LFG collection system in the post-closure maintenance period <br />are included in post-closure maintenance costs. <br />Landfill gas condensate generated by the LFG collection system will be handled as leachate in <br />accordance with the Waste Discharge Requirements. <br />2.5.4 LFG Treatment <br />Collected gas will be combusted as fuel for electrical generators or in one or more flare stations <br />in accordance with the applicable SJVAPCD permits and regulations. <br />LFG collected from the field is transported to the site’s landfill-gas-to-energy plant (operated by <br />Ameresco Inc.) to generate power. The flare station is maintained as a back-up in the event the <br />LFGTE plant becomes non-operational; in which case the LFG is burned in the flare in accordance <br />with the Permit to Operate issued by the SJVAPCD. <br />Presently, the LFG treatment equipment is located within the future landfill footprint. The <br />treatment facilities will be moved in coordination with increasing the size of the facility to process <br />increasing LFG. This movement is not part of closure construction, and is not included in the cost <br />of closure. <br />2.5.5 Leachate Control <br />Leachate from present and future modules will be collected in leachate collection and recovery <br />systems installed with the modules (JTD Figure 18), and returned to lined modules in accordance <br />with the Waste Discharge Requirements. As the landfill approaches closure, placement of the <br />final cover and the overall thickness and absorptive capacity of the waste mass will cause less <br />leachate to be generated. At this time, it is anticipated that leachate will be pumped from sumps <br />using automatic, level sensing pumps and discharged through flow meters to onsite temporary <br />storage or returned to lined landfill modules in accordance with the WDRs. <br />It is also anticipated that the absorption capacity of the relatively dry refuse placed at the FSL, <br />and the uptake of water in the production of landfill gas, will allow for the return of leachate over <br />the lined modules for many years after closure. Inadequacy of those mechanisms, if it occurs, <br />would be indicated by the inability of the leachate pumps to remove leachate from the leachate <br />sumps to maintain less than 1 foot of liquid head over the liner. Monitoring of the leachate pumps <br />and sumps will indicate that this condition is developing. If this occurs, leachate generated after