TEXTILES.ORG
Q: I need to make sure of what the minimum area is for a fusion-welded HDPE geomembrane patch with a 60-mil (1.5-mm) thickness that should be fusion welded instead of extrusion welded. Also, when does one need to replace a panel that is damaged (i.e., the percent of damage allowed to be repaired)?
Thank you for your time!
A: The U.S. Environmental Protection Agency (EPA) Technical Guidance Document suggests that a patch should extend 4 inches (100 mm) beyond damage that has been blunted. This means if there is a 12-inch (300-mm) slit in the geomembrane, the ends should have circles punched in them and then the patch area would be 160 square inches (0.1 m2) or 20 inches (500 mm) long × 8 inches (200 mm) wide.
For punctures, patches are rounded and have a minimum diameter of 8 inches (200 mm). The installers will have to get permission from QA/QC inspectors or the site engineer to repair damages with an extrusion bead only—not with a fusion-welded HDPE geomembrane patch.
Your question of “when do we need to replace a damaged panel?” is a common one. I have not seen a percent damage number in specifications allowed for repair per panel. I have seen numbers like no more than 10–15 repairs in any 10,000 square feet (929 m2) of geomembrane area. If there are more instances of damage than the prescribed number, panels are cut out and replaced.
Unfortunately, there is no International Association of Geosynthetic Installers (IAGI) or ASTM International guidance in this regard. The European standard, EN 1848-2:2001 “Flexible Sheets for Waterproofing—Determination of Length, Width, Straightness and Flatness,” is also silent in this context.