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San Joaquin County Environmental Checklist Issues associated with LFG are listed below. ■ Subsurface migration of combustible gas across property boundaries and into onsite structures. ■ Potential for groundwater contamination by VOCs. ■ Emissions of VOCs into the atmosphere. ■ Odor control. Subsurface migration of combustible LFG,and the safety of onsite habitable structures, is monitored in accordance with the Methane Monitoring Program and CCR Title 27, Section 20919. To monitor subsurface migration,the County has installed seven monitoring probes along the perimeter of the landfill facility. These wells are near the landfill property boundary and consist of triple- completion wells to monitor at shallow,intermediate,and deep zones. To verify that onsite structures do not contain combustible gas,onsite structures are monitored with a hand-held combustible gas detector. The landfill facility is presently in compliance. VOC detections in groundwater are sporadic and inconsistent,often due to the low detection limits for these compounds and the potential for trace concentrations of contamination in the laboratory environment. However,LFG has apparently affected groundwater for a short time in the past. In July 2002, one VOC (reactive organic gas)was confirmed at one groundwater monitoring • well. No other VOCs have been detected since that time,except for sporadic trace detections. The County intends to install a LFG collection and treatment system in 2006 to control LFG migration and alleviate possible concerns for groundwater impacts. The WDRs issued by the Central Valley Water Board also require monitoring the soil within the landfill for VOCs. Four additional wells,along with the perimeter migration monitoring wells,are monitored to satisfy that requirement. VOCs were found at many of the soil gas wells;however,the presence of VOCs in the soil gas does not appear to impair the waters of the State. Consequently,releases of LFG as a result of this project would be considered less than significant,and no additional mitigation would be required. The NCRC&SL is subject to CFR Part 40,which limits the emissions of VOCs to 55 tons per year. Recent estimates,based on samples of LFG taken at the landfill facility,indicate that the VOC emissions are approximately one-half this limit;therefore,present air quality regulations do not require an LFG collection and treatment system. However,the installation of an LFG collection and treatment system will greatly reduce the VOC emissions,decreasing them farther below the regulatory limit. As the refuse in the landfill increases,the potential to emit VOCs will gradually increase;however,the LFG collection and treatment system would be expanded in accordance with air quality regulations into new refuse placement areas, Notice of Preparation for the June 2006 North County Recycling Center and Sanitary Landfill 2_20 Jas os307.os Permit Revision