A lake restoration project may call for using an impermeable liner material over the entire bottom and banks of the feature, or it may only require a few patches of liner installed in certain areas. Regardless of how much liner will be used in the project, the material chosen must meet a long list of criteria. Choosing the wrong liner material is often worse than simply leaving the liner out altogether, especially in natural lake restoration. The wrong liner could cause serious issues or work so poorly it’s basically a wasted cost. Make sure to use the right liners for every part of a lake restoration project with this guide to selecting the correct material.
Clay Composite Liners and Dispersed Products
Lake designers who are interested in building completely natural lake environments will often wrongfully recommend either clay composite liners (CCL) or dispersed bentonite clay products to seal the bottom. The idea is that these clay products swell up as they absorb water from the lake, locking together to form a barrier that can hold back water. Unfortunately, this isn’t necessarily true. Like natural layers of clay-based soil, these clay liners still allow water to seep through slowly. This is because the material is made of tiny particles that still feature gaps between them. Even CCL products that are based around a woven fabric let plenty of water through, especially as the clay particles wear away with time.
Impermeable Geomembranes vs Clay-based Liners
In contrast, impermeable liners like reinforced polyethylene (RPE) have practically no gaps between the particles of the polymer that comprise them. This means they’ll better control seepage and offer practically no water loss through the ground; something clay-based liners just can’t provide. Impermeable liners are also much easier to install, although they do require the draining of the lake. This allows you to get a good look at the surface you’re covering and ensure that the material actually conforms to every cavity and curve. When clay-based liners are tested in real life lakes, engineers often find problems with the material drifting over or settling through uneven areas. Flexible liners, that are reinforced, will stretch easily over small cavities and depressions to give a complete, leak-proof control that clay can’t compete with.
Why Concrete is a Poor Choice for Lake Restoration
Concrete is often thought of as the ultimate lining solution of a lake, especially along badly eroded banks. However, it’s not as impermeable as many people assume. That’s exactly why many buildings today now need waterproofing to keep water from being absorbed through the sponge-like concrete foundation. In the lake, a concrete liner allows water to slowly seep through. The pressure of the water forces it through tiny capillary openings in the material, allowing for a constant loss, that accelerates as the material inevitably develops many tiny cracks over time. No amount of constant concrete resealing will keep up with the development of new leaks. Only pairing a flexible liner with the concrete will make it a truly impermeable barrier at the bottom of a lake.
Flexibility for Covering Advanced Underwater Features
The exact amount of flexibility varies even for products sold as flexible geomembranes. One product may be thick and stiff, but still relatively flexible when compared to a material like concrete. Other materials like RPE are very flexible and easier to conform to curves and natural shapes. This is essential when you wish to preserve the existing character of a lake’s bottom or build new shaped areas for fish habitats. Shelves and overhangs that meet at different heights are valuable for many species of fish and plant life, but they’re also tricky to cover with a liner that isn’t highly flexible. A product like RPE is the best option because it combines superior flexibility with the strength usually only found in thicker and stiffer materials.
Burying Flexible Liners
Most lake restoration projects aim to restore or keep a waterway looking as natural as possible. There’s a common myth that a natural lake or pond can never contain any flexible liner materials because they must be installed in an exposed way. This is far from the truth. Flexible liners from BTL Liners are safe to bury under layers of gravel, sand, and soil. Installing plants, and developing natural habitats rich with healthy microorganisms, is perfectly compatible with a buried liner. Simply avoid deeply rooted or aggressive growing shrubs and trees and no other water plants should grow deep enough to penetrate the material. Of course, not all liners are designed to withstand the wear and tear of buried installation. Stick to a reinforced material like RPE to make sure that the weight of the covering material doesn’t stretch or tear the liner and create a leak.
Durability for Dredging and Hydro-raking
Lakes that undergo initial restoration processes will likely need them again in the future. Even if maintenance and care manage to keep the lake healthy for multiple decades between restoration efforts, eventually most waterways need some in-depth work to return it to its former state. Choosing a liner that won’t tear during dredging and hydro-raking processes allows you to better maintain the lake without having to constantly refresh the liner. These processes are somewhat hard on the bottom of the pond, but reinforced materials can withstand raking and dredging equipment when installed properly. Why replace the liner every time you have to remove sediment or weeds when there are liners available that can last 20 years or more?
Which Material is Best for a Fish and Plant Safe Pond?
Material selection is essential for most lakes and more than just durability and longevity should be considered. Almost all lakes host some kind of fish and plants since it’s simply impractical to keep a waterway that large free from all life. This means that the materials used in the lake must be chosen with compatibility in mind, since geomembranes in particular can leach out damaging chemicals.
PVC
Polyvinyl chloride is the material most commonly known for being unsafe for fish and plants. Also known as PVC, it’s only rarely available in formulations safe for both. This makes it hard to qualify for use in large outdoor projects like lake restoration where fish and animal exposure is unavoidable. PVC is also too prone to UV degradation to use for most exposed installations. Even though lakes tend to feature buried installation instead, there’s always a chance that the liner will become temporarily exposed due to the wearing effect of wind and water erosion. Choosing a UV resistant liner is always recommended, even for buried installation, so that these temporary exposures don’t create weak points in the material. Finally, PVC is also weak against tearing and puncturing in general, making it a poor choice for a project as large as a lake.
HDPE and LDPE
High density polyethylene (HDPE) and low-density polyethylene (LDPE) are two decent options for lining lakes that are both still far from ideal. HDPE is on the stiff side, which lends to durability and the ability to smooth out flat rather than developing folds. However, it is also hard to bend around sharp curves and conform to unusual features like overhanging banks. It’s simply impractical to handle on a large scale like lake lining. On the other end, LDPE is much more flexible and easier to conform to natural lakebed shapes. Yet, it lacks the durability and strength needed to qualify it for long-term use in a challenging environment like a large lake. It’s too likely to break down due to chemical or UV exposure, which is likely to happen at least occasionally in an open lake.
RPE
Reinforced polyethylene (RPE) is the best choice for almost all lake restoration projects that call for flexible liners. This material works equally well for covering the entire bottom of a lake or just the banks and outlet areas. It’s widely used in all industries for retention ponds and containment systems of all kinds, making it durable enough for lake use as well. There are many fish and plant-safe formulations available, ensuring there’s no need to choose between a tough or safe liner material. The reinforced design makes this material as strong as HDPE and EPDM without sacrificing flexibility by keeping it much thinner. All of these reasons, and more, make BTL Liners RPE formulations some of our bestselling lake liner products.
Still not sure which liner to choose or what makes a good lake liner? BTL Liners is happy to help you with specialized advice on your lake restoration project. Put our decades of industry experience to good use on your lake improvement plans by getting our custom recommendations on liner installation.
