This is a section of an article from waste360.com.
The Landfill Gas (LFG) collection wellfield consists of two major integrated components: vertical wells and horizontal trenches for LFG collection; and main LFG header piping and branch piping connections to wells, trenches and leachate system cleanouts.
Good LFG well performance starts with proper design. This includes the proper number and spacing of collection wells and trenches, adequate size and depth of well boreholes, proper packing and sealing around the well screens and solid casings.
The wellhead should be completed with fittings that allow easy and direct access into the well casing, a flow adjustment valve and multiple points for gas measurements. Provide some extra flexible tube connecting the wellhead to the header to allow for differential settlement. There must be reasonable and safe access for personnel to each wellhead for routine monitoring and maintenance.
The main LFG header piping and branch connecting piping are responsible for distributing the vacuum produced by the BFS out to all collection devices. The piping also must carry some condensed LFG liquid to collection points. Thus, it must be designed conservatively and with an eye toward changes that occur over the life of the landfill that can potentially reduce its capacity.
The main header should form a closed loop, if possible, to more evenly disperse the vacuum and reduce overall vacuum loss. The pipe diameters should be judicious to allow for higher-than-predicted gas flow and/or vacuum and possible future well-field expansion. Pipe runs should include adequate slope to account for consolidation and uneven settlement of the waste over time and still allow for continual flow of condensed liquid. A design with undersized pipe and inadequate pipe slope can result in continual problems with lower-than-expected system performance.
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