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Taking issue with recommendations

April 1st, 2008 / By: / From Our Readers

The “Kam Kotia Project Case Study” in the February/March 2008 issue of Geosynthetics magazine starts off with interesting descriptions of the project design, geosynthetic testing, and construction.

However, the summary and recommendations section provides misleading statements. The author writes, “As per the GRI’s White Paper of April 2005: Do not use GCLs with needlepunched nonwoven geotextiles on both sides unless one of the geotextiles is scrim-reinforced.”

This GRI White Paper is taken totally out of context and does not apply to all GCL applications. The GRI White Paper #5 (April 2005) titled “In-Situ Separation of GCL Panels Beneath Exposed Geomembranes” referred to several cases over nearly 20 years where GCL was overlaid by a geomembrane and exposed to the environment for a period of 2 months to 5 years. The rare type of GCL panel separation described is not envisioned to occur for the more common situation, such as Kam Kotia Mine, where timely soil cover is placed over the GM/GCL composite liner.

Also, the use of a scrim-reinforced nonwoven is only 1 of 6 recommendations for exposed geomembrane applications. It should be noted that prominent geotechnical engineers utilize needlepunched GCLs with nonwoven geotextiles on both sides without any scrim reinforcement, even in exposed geomembrane applications.

In such cases they apply one of the other recommendations of the GRI White Paper #5; that is, they perform testing and increase the overlaps accordingly (Thiel et al., “Practical Guidelines for Specifying GCL Overlaps–Accounting for Shrinkage in the Field,” GFR, Vol. 23, No. 8).

Jim Olsta, P.E., Technical Manager, CETCO, Arlington Heights, IL.

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