When aiming to mimic a natural environment for rapid growth of valuable fish or plants, it’s tempting to choose natural pond lining materials over flexible plastic liners. Natural liners made of clay soil or bentonite are often advertised as being better for water quality, but they have other issues that make them a less than ideal choice. Clay liners are definitely not ideal when building a commercial pond for holding wastewater or chemicals for processing. Find out why flexible plastic liners outperform natural options like clay in most situations.
Less Permeable Materials
On a technical level, it’s practically impossible to achieve complete impermeability in your pond. However, flexible pond liners offer the highest level of impermeability in a real-world application. They’re far more waterproof than any natural liner materials, offering better seepage control to prevent both the loss and addition of water. Clay liners only have a limited impermeability which drops as the material ages and develops leaks. Since quality, flexible liners can last decades without developing leaks, there’s far less water lost over the lifespan of the pond.
Bentonite and other clay materials naturally settle over time since they’re blended with the soil. You’ll need to add new clay lining material anywhere from every two to 10 years, depending on the amount you add and the biological activity in your pond. Flexible liners can last decades when properly covered and maintained. The additional cost of replacing natural liner materials every few years quickly makes them more expensive in the long run than flexible geomembranes. Clay can be added without draining the pond, but this is often a time-consuming process that can take days to weeks to clear the water again. Replacing a flexible membrane does requiring the draining of the pond, but installation can be completed in hours for small ponds and allows for immediate refilling.
Clay liners are notorious for developing random leaks at various points after installation. Some leaks begin immediately after the pond is first filled, while others take years to develop. Since tracing these leaks to a specific crack or thin layer of clay is nearly impossible, it’s very tricky to seal the source of water loss. This leads to soil destabilization and sinkholes in loose soils. Most pond owners with natural clay liners must dump the same amount of clay they originally used to attempt to establish a new layer. Bentonite, in particular, is often marketed as a self-healing material that plugs its own leaks, but that’s only true when there’s nearly three feet of clay applied evenly to every underwater surface. This amount of clay not only comes with a hefty price, it also generates plenty of transportation fees.
Easier Cleaning and Dredging
It’s difficult to dredge or clean a naturally lined pond because there is no distinct separation between the liner and the soil below. In fact, it’s necessary to mix the clay with the native soil of the pond’s underwater surfaces in order to create a tight seal that stops water loss. When removing leaf litter and other debris that’s broken down into sludge at the bottom of the pond, it’s all too easy to scrape away the clay liner as well. Accidentally breaking the liner leads to leaks that are hard to find and seal. Flexible liners are much more damage resistant and easier to clean when necessary, making them a better choice for fishponds and evaporation ponds alike.
Better Bank Stabilization
Clay liners generally only cover the soil below the surface of the water due to both the cost of the material and its installation requirements. When the material isn’t exposed to water, it doesn’t expand properly and bind with the soil. This means that the banks of a naturally lined pond are more susceptible to erosion and damage from water lapping at the shores. Flexible pond liners are run over the apron and banks of the pond, creating a single plane that protects every surface from soil loss. This prevents the pond from filling up with sediment and protects against bank collapses.
You can still install layers of minerals, clay, gravel, or dirt over geomembranes to create natural pond bottom environments without risking seepage or water loss. Don’t rely on natural pond liners alone since they require more maintenance and provide less reliability than materials from BTL Liners.