Mechanical gas vent

DETAILED DESCRIPTION Landfill construction projects, for both new facilities and partial closures of active sites, have evolved from what we commonly referred to as "dumps" to high tech facilities.
This is largely due in part to environmental concerns to protect our groundwater supplies from contamination from rainwater runoff, known as leachate.
In 1991, Subtitle D of the Resource Conservation and Recovery Act (RCRA) mandated regulations--minimum criteria--for new municipal solid waste landfills and lateral expansions of existing units.
Many aspects of the regulations also apply to existing landfills.
Landfill design technology has developed rapidly since the late 1970s and early 1980s.
The two key elements driving modern landfill design are geosynthetics and environmental regulations.
Subtitle D regulations require after an active landfill no longer accepts waste, a final cover must be installed.
The final cover consists of an infiltration prevention layer and an erosion layer.
The infiltration prevention layer is made up of a minimum of 18" of soil with a permeability less than or equal to the liner system in the base of the landfill cell, but no greater than 1.
times.
10.
sup.
-5 cm/sec.
The erosion layer must be at least 6" of soil that can sustain native plant growth.
Typically, a synthetic liner is placed over the top of the full landfill cell to prevent water infiltration into the landfill, thereby, reducing leachate and the associated costs involved with treatment and handling.
During the installation of the final cover and subsequent synthetic liner, problems with the liner "ballooning" as a result of trapped landfill gases have caused considerable problems for contractors, engineers, and owners of landfills.
This condition is usually a result of eroded areas due to rain during installation of cover soil over the liner, also a requirement of Subtitle D.
The ballooned areas must be dealt with on an ongoing basis by the contractor.
If the balloon is allowed to continue to grow unchecked, the previously welded synthetic liner seams may be severely stretched beyond the material's maximum elasticity