The current state of practice in the design of landfill gas management systems depends heavily on the use of computer models to estimate gas collection rates and to size the required piping. Several of the models used to estimate gas collection rates to allow the user a limited degree of flexibility in defining input parameters. However, there is relatively little data available to guide the user in the selection of input values. Since each landfill is unique and dynamic, field work (pump testing) or site-specific operating data should be used to calibrate gas production models. When budget or schedule do not permit pump testing during design, engineers often input data which will result in "conservative" output. Although such conservative designs provide workable systems, the result is often reduced operating flexibility and increased cost to the owner. This case study compares operating data from a landfill gas management system in the City of Glendale, Arizona to the input and output of the gas collection model used to design the system. An arid climate site was chosen for the case study because very little pump testing or comparative analysis has been performed for arid climate landfills. Such sites are traditionally thought to produce little landfill gas due to the lack of added moisture from precipitation. Similarly, the relatively high average temperatures experienced in arid climates are thought to result in relatively little condensate. The results of this case study indicate that arid climate landfills can produce quantities of gas and condensate rivaling landfills in much more humid climates. Currently, an average of 1,300,000 cubic feet of landfill gas and 200 gallons of condensate are being collected by the system each day. The condensate is being incinerated in the flare. Operating data indicates that the composition of the refuse is influencing the gas generation rate, and the design of the gas collection system is influencing the amount of condensate being collected.
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