Editor’s Note: The article, “GMA speaks up during EPA coal ash hearing,” prompted the following comment and response.
What about selenium and coal ash?
From: Dennis Lemly
Posted: Sept. 13, 2010
Your cited data source does not measure selenium in the leachate from the coal ash disposal site, or any other for that matter. It does state that the leachate rate is 300-600% greater for the coal ash site than other waste types, which suggests that post-closure data is critical to evaluate the performance of what you are proposing in the context of EPA’s new rule—i.e., that composite liners will protect people and the environment.
Yet, you have no post-closure data for the coal waste site. How can you accurately project performance for your liner system in a coal-ash application when you: (1) have no post-closure data and (2) have no selenium measurements at all?
Understand that I am a proponent of liners … they are a step in the right direction. But what you have presented is not convincing or conclusive with respect to coal ash and selenium. I hope you have more substantial data that will be forthcoming soon.
RE: What about selenium and coal ash?
From: Boyd Ramsey, GSE Lining Technology
Posted: Sept. 14, 2010
The performance of liner systems is typically not—in fact, almost never—evaluated against specific agents (i.e., selenium).
The interaction of geosynthetic liner materials to an extremely wide range of chemicals is well-known and understood. There is one general class of chemical (very low molecular weight halogenated hydrocarbons) where there are measurable interaction differences between the chemical and the geosynthetic material, depending on the specific nature of the chemical.
For all other general classifications of chemical interactions, the performances of the geosynthetics are relatively uniform. Thus, testing is not done for a specific chemical.
In fact, it is thought that mixtures of a wide range of chemical components present a more difficult performance standard for geosynthetic barriers. That is why, during the early use of geosynthetics, a large number of tests were conducted using leachate from waste containment facilities, which contained a broad range of chemical constituents.
These tests, identified under the name EPA 9090, have successfully demonstrated the inertness to a broad range of chemicals that has allowed geosynthetic materials such as high-density polyethylene to contain materials effectively for decades.
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