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<br /> <br />Foothill Sanitary Landfill Page 45 of 52 San Joaquin County DPW - Solid Waste <br />Joint Technical Document Revised 12/04/2025 <br /> <br />Regulations and the Permit to Operate (Appendix A). This measurement indicates that surface <br />emissions are within the regulatory limits. <br /> <br />Surface emissions are controlled by the LFG collection and treatment system (Figure <br />15). This system consists of thirty-four vertical wells and eighteen horizontal collectors, each of <br />which is provided with an adjustment valve, sampling port, and temperature gauge. The LFG <br />collection rate at each well is adjusted based on the methane content at each well. The vacuum <br />is increased or decreased to maintain the methane content within a prescribed range. <br /> <br />LFG collected from the field is transported to the site’s landfill-gas-to-energy plant <br />(operated by Ameresco Inc.) to generate power. Excess LFG is destroyed by the low Nox flare. <br />The flare station also functions as a back-up in the event the LFGTE plant becomes non- <br />operational; in which case the LFG is burned in the flare in accordance with the Permit to <br />Operate issued by the AQMD. <br /> <br />7.12. Subsurface Gas Migration Control Plan <br />Foothill Landfill has a Perimeter Landfill Gas (LFG) Migration Monitoring Network <br />consisting of 25 LFG migration monitoring wells installed in accordance with Title 27 Section <br />20925 to monitor subsurface LFG migration at the site (Figure 16). These wells are the point of <br />compliance for monitoring subsurface LFG migration, especially methane to be below 5% in <br />accordance with Section 20921. The site’s LFG perimeter migration monitoring wells were <br />installed in 2009 after approval from all regulating agencies (Appendix C). A LFG collection and <br />control system was installed in 2006 to control LFG migration within the site as one of its <br />objectives. <br /> <br />The site’s perimeter LFG migration monitoring network is monitored monthly in <br />accordance with the sites approved LFG migration monitoring plan (Appendix C). A monitoring <br />report is submitted to the LEA afterwards. Currently the site is in full compliance. <br /> <br />When excess LFG concentrations have been detected in any of the site’s perimeter LFG <br />migration monitoring well, the following steps will be followed in accordance with Title 27 <br />Section 20937: