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Purging the geosynthetics system of dated test methods and specs

News | June 1, 2010 | By:

In May 1998, Maryann Gorman wrote a commentary in ASTM Standardization News entitled “How Specifications Live Forever.”

She began the article by explaining how standard gauge railroad track spacing in North America is 4ft-8.5in. (1.4351m). It seems that this precise dimension dates from Roman times because “the Imperial chariots were made to be just wide enough to accommodate the back-ends of two war horses.”

From a geosynthetics perspective, let’s work between agencies (ASTM and EPA) in that there is currently a series of ASTM standards that are intended to replace the EPA 9090 method for determining chemical compatibility of geomembranes to various candidate liquids. In fact, more than 15 years ago, Bob Landreth (long retired from EPA) requested that we develop an alternative standard since EPA was not in the standards setting and distribution business.

The current series of incubation practices and subsequent test methods follows. It is comprehensive and much more than the original approach. Let us all use this sequence of ASTM standards and please stop requesting EPA 9090.

In a somewhat similar vein of between agency test methods, the Federal Test Method 101C for evaluating puncture resistance of geomembranes is another antiquated test method. The closest ASTM replacement is D4833 which uses a beveled 5/16-in. (7.94-mm) probe instead of a tapered point. This was intentionally done since the tapered FTM point underestimates scrim reinforced geomembranes by having the probe simply sliding between sets of adjacent yarns. To our knowledge, current geomembrane specifications all use ASTM D4833. Let’s stop with the FTM 101C requirement.

Completely within ASTM Committee D35 on Geosynthetics, there are many meaningful test method changes that the industry either does not know about or is reluctant to adopt. Some of them are as follows:

  • The old geomembrane ply adhesion tests (D413 and F904) have been upgraded and replaced by D7005.
  • The old geomembrane dogbone tension test (D638) has been upgraded and replaced by D6693.
  • The very old HDPE geomembrane stress crack test of D1693 has been completely replaced by D5397.
  • The old shear and peel tests of geomembrane seams (D4437 and D4545) have been replaced by D6214 (for PVC) and D6392 (for olefins).
  • The coated fabric test methods embodied in D751 are completely passé as is D3088 for PVC.

Regarding laboratory weathering devices for geosynthetics, the industry’s current choice is either the Xenon Arc (ASTM D4355) or the Ultraviolet Fluorescent (ASTM D7238). Following is a comparison table of approximate initial and maintenance costs of these contrasting incubation devices. In determining end-of-life testing, the choice is obvious to us. That said, the entrenched status of the Xenon Arc method is difficult to purge from user specifications.

Picking on specifications rather than test methods, we cannot neglect commentary on NSF #54. This series of specifications for 16 different geomembranes began in ca. 1980 and was last published in 1995 by the National Sanitation Foundation, now NSF International. Shortly thereafter they simply stopped all geomembrane specification activity, including distribution of the document itself. Even further, some of the geomembranes addressed in NSF #54 are not available and many others have been developed and are commercially available. Yet, we continue to see reference made to NSF #54 Specifications. It is time to stop using NSF #54 because there are viable generic specifications available for use for the majority of commercially available geomembranes.

We are sure you have some “golden oldies” of your own, but thought we would get these several items off of our chests. Thanks for listening in this regard.

Bob Koerner, Ph.D., P.E., NAE, is the director of Geosynthetic Institute (GSI) and is a member of Geosynthetics magazine’s Editorial Advisory Committee. GSI: +1 610 522 8440.

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