A geomembrane system is a complete set of liners designed to work together to contain any kind of solid or liquid waste. This system may include an integrated or loose floating cover to prevent evaporation and gas emissions, or the system may remain open to the air to encourage evaporation instead. Designing a complete geomembrane system requires the engineer to consider everything from how the seams are sealed to what edging materials are used to anchor the liner.
Seam Sealing Methods
Each material available for fabricating geomembrane systems offers multiple installation methods to choose from based on your design. Fusion welding, a method using a heated wedge to press two layers of material together until they melt, is a good option for RPP, RPE, and both HDPE and LDPE materials. It’s the preferred method for most installations due to the speed and reliability of the process. This is followed by extrusion fillet welding in which a heated resin is layered between the two layers of material and then pressed until it cools. It also works for HDPE, LDPE, RPP, and RPE liners as well as PVC. It’s highly durable and reliable but takes longer and requires more materials than fusion welding. Finally, seam tapes are available for all types of geomembranes, but they’re not recommended. This material takes a long time to apply by hand and offers the weakest seal of all three methods.
Sealing Geomembranes Around Penetrations
When designing a complex wastewater treatment system or biogas digester, it’s impossible to completely avoid penetrations that pass through the geomembrane. This is also common with materials installed as waterproof barriers on green roofs when vents and electrical connections must pass through the surface. Taking care to observe the following tips while cutting and capping penetrations through geomembranes will prevent leaks and reduce maintenance around these areas.
- Don’t cut the material until it’s in place and ready for the covering boot or cap to go in place immediately. Pre-cut perforations tend to stretch and tear during installation, making them harder to cover and seal.
- Test all penetrations with non-destructive methods like electrical resistance or vacuum pressure to verify a proper seal before fluids are added.
- Find angled pipe boots and connectors to ensure the protective cover always sits flush and fits tightly against the geomembrane surface.
- Secure geomembrane in place with sandbags and other temporary ballast when cutting large penetrations so that wind doesn’t lift the material and stretch or tear it.
