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.. ,.... ..<...$ (..J -`�" `.✓ \ �1 Y':mss, �j',� <br /> UTILIZATION OF LANDFILLS AS BUILDING SITES <br /> By: Robert P. Stearns , President , SCS Engineers <br /> Galen S. Petoyan , Project Engineer , SCS Engineers <br /> INTRODUCTION <br /> Development of completed- sanitary landfills as building <br /> sites requires anticipation and control of potential settlement <br /> problems and combustible gases resulting from consolidation ani <br /> decomposition of waste materials . <br /> Landfill gas (LFG) is produced as a result of anaerobic <br /> decomposition of organic waste materials placed in a landfill . <br /> The LFG is typically composed of approximately 50 to 60 percent <br /> methane , 40 to 50 percent carbon dioxide, and trace amounts of <br /> various other gases , including odorous compounds . Methane (CH, ) <br /> gas is odorless , colorless , and can he explosive when allowed Ea <br /> accumulate with air in enclosed areas and then exposed to an <br /> ignition source. LFG generated in landfills will vent verticall; <br /> through cover soils to the atmosphere , and can potentially mi - <br /> grate througgh subsurface soils several hundred feet laterally <br /> from a landfill site. <br /> Prospective developers of a former landfill are often un- <br /> aware of the difficulties that they may face with respect to LFG <br /> venting and migration , settlement and surface cracking , vegeta- <br /> tive stress, and leachate production . However, even when they <br /> fully realize the magnitude of these problems and the associated <br /> long-term costs , economics may be favorable for a more intensive <br /> development than pure open space or recreation . <br /> This paper will describe LFG control measures and control <br /> system operating experience at two former landfill sites which <br /> have been successfully developed in the City of Carson, Cali - <br /> fornia . SCS Engineers provided engineering services for systems <br /> Installed at both sites , and provides routine monitoring and <br /> maintenance services for the owners . <br /> Work began in 1975 to develop a six-screen drive-in theater, <br /> including projection , concession , and fee booth facilities atop a <br /> completed 24-acre , 50-ft-deep landfill site. The landfill had <br /> received an estimated 750,000 tons of household and commercial <br /> wastes between 1964 and 1971 (see Figure 1 ) . <br /> LFG control measures were required to protect on-site <br /> structures , theater employees and patrons , and to prevent off- <br /> site subsurface LFG migration . Facility construction began in <br /> 1980 and was completed in 1981. Continuous theatre operations <br /> have followed . <br /> LFG-66 <br />