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CONCLUSIONS <br /> The monitoring results show that methane concentrations exceed 5% in the probes along the north end <br /> of the landfill this quarter. It appears that gas levels have dropped slightly since last summer. However, <br /> the levels are still above regulatory limits. <br /> Since normal operation of the landfill gas system does not consistently control gas migration, it is <br /> necessary to modify the system in an attempt to reduce perimeter gas levels to below 5%. The county <br /> is in the process of purchasing a larger motor for one of the blowers. By increasing the horsepower of <br /> the motor, the blower will produce more vacuum to be applied to the field. We believe that vacuum <br /> shortage is a major reason for the lack of migration control. The areas of gas migration are <br /> concentrated on the north end of the landfill, where vacuum is lowest. We have been directing all <br /> available vacuum to the north end by closing off vacuum to all wells on the south half of the site. We <br /> have done everything we can do with the existing equipment. Therefore, modifying equipment to <br /> provide more vacuum is a corrective action measure that can be performed with a minimal expenditure. <br /> We would like to perform this change and have some time to evaluate its effectiveness. The motor will <br /> be installed within the next month. At this time it does not appear that the gas is a health threat because <br /> methane has not been detected in the labor camp structures. <br /> Monitoring will continue with the next monitoring event in October 1999. Further monitoring will help <br /> determine if the gas control system is working more efficiently. <br /> S:\WES\HL\GAS\3rdQU99G.wpd <br /> 5 <br />