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production within the landfill. Methane content below this value indicates dilution by air drawn <br /> through the soil into the refuse caused by the negative pressure at the well. Maximizing LFG <br /> collection while minimizing air intrusion is the"balancing act"of operating an LFG migration <br /> control system. <br /> Results from LFG System Operation <br /> The effectiveness of the LFG System is indicated by the reduction of VOC detections in samples <br /> taken from MW-2 (Figure 4). The County expects VOC concentrations to reduce to <br /> non-detectable levels. <br /> There has been a noticeable decrease in both the total BTU collection rate and methane content <br /> of LFG at the flare station since operation began. The BTU content of collected LFG has <br /> declined from approximately 10.3 million BTU/hr to 7.04 million BTU/hr, a decrease of 32 <br /> percent(Figure 5). The methane content decreased from 37.2 percent to 32.4 percent in the same <br /> time period. <br /> Concurrently, combustible gas concentrations at the perimeter probes reduced from 60 percent to <br /> below 5 percent. This indicates that the negative pressure induced within the landfill by the LFG <br /> collection system has not only prevented further release of LFG into the vadose zone,but that <br /> this negative pressure has removed previously emitted LFG from the soil beneath the landfill. <br /> Progress of Corrective Action Measures 4 Harney Lane Sanitary Landfill <br /> Revised-August 22,2003 County of San Joaquin <br />