While geomembranes may make the best liner for all short-term and permanent storage situations, they’re far from the only option. Other options for lining storage tanks and ponds include:
- Clay: Natural and bentonite clay both seal tightly enough to create a semi-permeable barrier that slows down the flow of moisture out of the pond or tank. However, clay liners take a lot of work to apply and require routine replacement every few years.
- Liquid polymer sprays: While some projects involve the installation of this barrier during installation, most products are designed to help seal leaks in existing containers and ponds. It’s a very expensive way to seal a large area and doesn’t tend to last even a fraction as long as a geomembrane.
- Coated concrete: Combining roll or spray-on liquid polymers and concrete barriers increases the impermeability and durability of a liner. Yet this kind of installation requires far more maintenance and tends to cost more upfront to install than a geomembrane product.
- Bare concrete: With no coating or sealant on the surface, bare concrete tends to slowly wick moisture through itself thanks to tiny pores and capillary action. It’s also hard to seal for leaks without completely draining the pond or storage container.
- Solid metal: Whether shipped to the site or manufacturer on-site with sheet metal and welding equipment, solid metal storage tanks are a highly durable option. Unfortunately, they’re also highly expensive and require additional coating for corrosion protection both inside and out.
- Fiberglass: Tanks molded from fiberglass are chemical resistant and durable, but they’re only available in limited sizes. Tanks that can hold the equivalent of a multiple acre pond are so expensive and hard to transport that they’re hard to find in many markets.
If you have a pond or tank that is already lined with or constructed from one of these other methods, you may still be able to install a geomembrane over any existing surface. This can stop leaks without requiring you to chase down each individual break in the surface. However, some clay and damaged concrete liners may need removal before geomembranes go in for full adhesion to the surface. Uneven and missing clay or concrete leads to gaps that let water or air accumulate behind the liner, forming a bladder or bubble. Proper surface preparation ensures strong liner adhesion across the entire pond or tank.
Preventing Lifting and Floating Liners
While you want geomembrane covers to float on the surface of the water, it’s definitely not something you want from your liners. Liners that detach from the soil are caused by a rising water table, gas production as plant material breaks down under the surface, or leaks that allow water to seep under the material. Rising water tables and gas production are both easily avoided by creating channels for gases and liquids to escape around the edges of the liner. Leaks take a little more effort to find and repair, but they shouldn’t return seasonally like both of the other causes of floating liners. Thankfully, leaks are very uncommon if a high-quality liner is implemented. Wind lifting generally only occurs around exposed edges or during installation, so make sure there’s plenty of protective ballast covering any exposed material where wind could get underneath and lift.
Meeting EPA Requirements for Potable Water Storage
Storing potable water is highly challenging because each day brings dozens of new ways for water to become contaminated or fail at some step of sanitization. In order to meet all of the regulations set by the Environmental Protection Agency (EPA) and state departments, you’ll need a geomembrane that is NSF 61 approved. This standard set by NSF International regulates the materials used for all equipment that processes or stores potable water. These requirements also obviously apply to any floating covers or baffles that make contact with the water, so it’s best to choose the same geomembrane for all of these purposes.
Finding Leaks in Existing Geomembrane Liners
Geomembranes offer more opportunities for finding leaks in the liner layer than other materials like clay and concrete. Some methods, such as electrical integrity or dye testing, don’t even require draining the pond or tank before the tests begin. Electrical tests in particular are widely used on large storage areas because it’s possible to detect leaks in any part of the liner, not just at the existing seams. If a crack or puncture occurs in middle of a solid sheet of geomembrane, the electrical integrity test will still find it.
Other methods work best immediately after installation or repair service, such as vacuum testing. Adding a colored polymer flocculent to the water can both identify and close up a small leak at the same time as the water pressure of any leaks pull the material to their locations. You should follow up these temporary treatments with a permanent patch to maintain the integrity of the liner. Only some of these products are safe for fish, plants, and potable water, so don’t add anything to the water without checking it’s approved for your particular system. Air lance testing is a final option, although it requires you to drain all the fluid from the tank or pond first. An air nozzle is applied to each seam to see if the material lifts up at all, which indicates air is penetrating through the geomembrane via a leak.
