Exposed geomembrane cover

I am evaluating the feasibility of constructing an exposed geomembrane cover on a coal combustion residuals (CCR) fly ash impoundment. The evaluation includes scenarios of: (1) allowing surface water to shed and (2) intentionally impounding water.

In reviewing the available literature, I came across your article “Traditional vs. exposed geomembrane landfill covers” (Geosynthetics, October/November 2012). My three questions:

• The article mentions an ongoing laboratory lifetime prediction study. GRI White Paper #6 “Geomembrane lifetime prediction: Unexposed and exposed conditions” available on the Geosynthetic Institute website was updated in February 2011. Is a future update of GRI White Paper #6 imminent?
• The article mentions the 2009 GSI study regarding state regulatory agency acceptance of exposed geomembrane covers. I am evaluating the coal belt region (Pennsylvania, Ohio, West Virginia, etc.) Can you point me in the right direction as far as determining if exposed geomembrane covers have been permitted and installed on solid waste, CCR, or similar disposal facilities?
• Are you aware if there is an update on state regulatory agency acceptance of exposed geomembranes since the 2009 GSI survey?

Robert | Pennsylvania

Robert,

For an exposed GM cover I would recommend your option (1) of shedding the water to the down gradient perimeter of the site. That said, the exposed durability is conservatively stated in the 2012 Geosynthetics article. We now have much better data and the times are
20-40% longer. They are in an internal report and were made public during a GSI webinar on Dec. 9, 2015. Look at this on our website.

Your question on state acceptance is in our White Paper #17 on post-closure care of landfills, also on our website. We have nothing more recent in this regard.

Bob Koerner | GMA Techline