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<br /> <br />Foothill Sanitary Landfill Page 46 of 53 San Joaquin County DPW - Solid Waste <br />Joint Technical Document Revised 6/09/2020 <br /> <br /> <br />7.12. Subsurface Gas Migration Control Plan <br />Foothill Landfill has a Perimeter Landfill Gas (LFG) Migration Monitoring Network consisting of <br />25 LFG migration monitoring wells installed in accordance with Title 27 Section 20925 to <br />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 />objective. <br /> <br />The site’s perimeter LFG migration monitoring network is monitored monthly in accordance with <br />the sites approved LFG migration monitoring plan (Appendix C). A monitoring report is <br />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: <br /> <br />a) The LEA will be notified by telephone or via email regarding the detection of <br />excessive LFG concentrations. <br /> <br />b) A note about the excessive LFG detection will be placed on the perimeter <br />monitoring log book. <br /> <br />c) A letter will be mailed to the LEA within seven (7) days after detection with the <br />following information: <br /> <br />• A brief description about problem and the extent. <br />• Monitoring results. <br />• Description about the site’s LFG collection and control system adjustment to <br />mitigate LFG migration around the problem area of the site.