Polymer-Enhanced GCL for Wet Process Ash Impoundment

Polymer-Enhanced GCL for a Wet Process Ash ImpoundmentBy GSE Environmental – An innovative geosynthetic clay liner (GCL) was used for the containment of wet process ash at a 3,520 MW facility in the Southeastern United States. The wet process ash project involved roughly 1,000,000 ft.2 of GSE Bentoliner CAR (Coal Ash Resistant) GCL.

The facility owner wanted an impoundment design that would conform to any potential rulings from the US Environmental Protection Agency (EPA) on coal ash management. The lining system needed to achieve the highest possible levels of containment with the greatest margin of safety.

For a GCL to be included, none of its additives could be toxic or promote microbial growth in the surrounding soils and water table.

The composite lining system involved the coal ash resistant GCL, a 60-mil textured high-density polyethylene (HDPE) geomembrane, and a drainage geocomposite. The GCL offered an ideal secondary component to the design, with enhanced performance in the presence of wet process ash leachate. It provided optimal containment in comparison with a native clay layer.

CONTAINING WET PROCESS ASH

The coal ash resistant GCL is a specifically formulated, polymer-enhanced geosynthetic clay liner with granular sodium bentonite encapsulated between two geotextiles.  It is intended for containment of the potentially high ionic strength leachates in coal combustion waste applications. The polymer enhancement of the bentonite delivers outstanding performance under extreme conditions and chemical attack, making it ideal for lining systems with wet process ash or dry ash storage.

This geosynthetic is unique in that high ionic solutions with elevated levels of calcium and sodium have historically been a “no-man’s land” for bentonite-based products. The innovation in GSE Bentoliner CAR gives the rapidly growing coal ash containment sector the type of long-term GCL support utilized in other barrier applications.

For more information on GCL, coal ash resistant geosynthetics, and related projects and engineering services, visit www.gseworld.com.

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