SWANA releases report on landfill final cover systems

A recent report issued by the Silver Spring, Maryland-based Solid Waste Association of North America's (SWANA) Applied Research Foundation (ARF) documents the benefits of two alternatives to the conventional final cover systems prescribed in U.S. Environmental Protection Agency (EPA) nonhazardous waste landfill regulations.

In response to growing concerns with the performance of prescribed final cover systems installed within one year after final waste placement, the 23 subscribers of SWANA’s ARF Disposal Research Group supported and participated in a study to evaluate cover systems that, though not prescribed in federal municipal solid waste landfill regulations, have been permitted as final cover systems.

“Our research focused on two systems – exposed geomembrane covers and engineered turf covers – that appear to offer significant potential to address the concerns subscribers identified,” says SWANA’s ARF Director, Jeremy O’Brien, P.E. “These identified concerns include the effect of landfill settlement on the final cover integrity during the post-closure care (PCC) period, loss of landfill airspace to cover soil, veneer slope stability, soil erosion, and the continual need to mow and maintain the cover vegetation.”

Exposed geomembrane cover (EGC) systems do not install the vegetative, topsoil, infiltration, and drainage layer components otherwise found in the EPA’s prescribed final cover systems.

Engineered turf cover (ETC) systems utilize an engineered turf layer to cover and protect the underlying geomembrane from UV radiation and oxidation and use a sand ballast to mitigate wind and landfill gas pressure issues.

The ARF report emphasized the evaluation of the service life of the cover systems in comparison to a 30-year post-closure care period and the estimated 450-year service life of the EPA-prescribed final closure system. Laboratory and field testing results discussed in the report found service lives ranging from about 100 years for the EGC to about 200 years for the ETC. 

“The report indicates both alternatives have real potential to meet and even exceed federal closure requirements while also offering landfills flexibility to better address specific, on-site issues and optimize their approach,” adds O’Brien.

Additional findings and considerations are documented in the full report, "Alternative Final Cover Systems and Regulatory Post-Closure Care," which is available here.

To learn more about SWANA’s Applied Research Foundation, visit swana.org/research.