Resolving geomembrane specification conflicts

Q: We are having arguments about whether the thickness of our geomembrane meets the specification. Do you have any suggestions which can ease the process?

A: GSI offers a conflict resolution service under the GAI-LAP program. The challenge is to identify and resolve disagreements related to a particular geosynthetic test method backed up with data and facts. As one can readily imagine, some of the biggest arguments involve the measurement of thickness related to ASTM D5199, ASTM D5994 (core thickness of textured geomembrane) or D7499 (asperity height). This perceived, easily measured property is anything but. One needs to measure it with verified equipment which meets the specification of the test method. This includes the shape of the presser foot and the applied normal pressure. There is also a search protocol which needs to be followed and a reporting requirement of extreme and average values. In short, this most basic of physical properties highlights the detailed nature of geosynthetic testing. In addition, one cannot emphasize enough the importance of good specimen preparation. Specimens are cut out of samples that have been conditioned to the laboratory environment. Most samples have material variability, however, so it is very important to take “representative” specimens across the roll width.

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