Flexible liners are the best option for agricultural drainage systems and similar designs. But not all flexible polymer-based liners offer the same combination of benefits and damage resistance. Installing the wrong liner material in a drainage system can result in leaks, loose or lost material, and the need to re-line the canals and channels after just a few months or years. Using the right liner will protect the entire drainage system from erosion and erosion for decades at a time with minimal maintenance.
Choosing a Liner Material
There are five main options when searching for flexible liners designed for canal and pond use. These materials are:
- Multi-layered reinforced polyethylene (RPE), the best choice due to its combination of durability, chemical resistance, thinner material without sacrificing tear resistance, and ease of installation.
- Polyvinyl chloride (PVC), a highly flexible material that can’t handle the chemical compounds found in most waste waters and the UV exposure common to drainage systems.
- High density polyethylene (HDPE), which offers some durability and chemical resistance, but which is best when combined with LDPE into an RPE liner product.
- Low density polyethylene (LDPE), a material that isn’t quite as durable as needed for drainage canals and channels unless it’s included in an RPE combination.
- EDPM rubber, a thick and hard to shape material that is rarely used for commercial projects like agricultural and mining drainage systems.
Multi-layered RPE liners from BTL Liners are tear resistant, allowing you to install them over rocky and rough soils without fear of damage. Other flexible liners must be much thicker and stiffer to resist this kind of abrasion damage, making installation difficult and increasing the chances of the liner pulling away from the soil. RPE is flexible enough to seal tightly to the soil of any ditch or channel, ensuring a smooth surface that speeds water along to its destination.
Installing the Liners
Consider the extra work involved in the installation of many liners before choosing a material. Some products aren’t offered in custom fabrication lengths from the manufacturer. RPE is easily cut and seamed at the factory in long continuous rolls for covering narrow drainage ditches and canals. This minimizes the seam sealing work at the site, ensuring fewer leaks and speeding up installation. Other materials are also slow to install because of stiffness and lack of flexibility. Most drainage ditches and trenches are narrow and feature nearly vertical sides, two installation challenges for some liner products. Liners made from RPE can stretch and bend around the shape of each part of the drainage system for a custom fit with less work.
Exposed vs Covered Installation
Some products are only meant for fully covered installation, which isn’t always practical or possible in a drainage system. The smooth surface of an exposed flexible liner is one of its main benefits when dealing with runoff and waste water that may leave behind solids or debris. Adding a layer of gravel or sand to protect the liner from damaging UV rays can trap even more debris, complicating the maintenance of the drainage system and encouraging clogs. RPE liners can handle exposed installation and even last decades despite the gradual effects of daily sun exposure.
Maintaining the Ditches and Canals
Just like with any pond or other artificial water feature, debris will gather in the bottom of an open canal or ditch and slowly reduce its volume and flow speed. This changes the parameters of water treatment ponds further down in the system, potentially increasing or reducing their effectiveness. Occasional maintenance is necessary to keep the drainage system clean and running smoothly.
If there are trees located around the open parts of the drainage system, you’ll need to remove leaves two to three times in the fall to ensure large clogs of material don’t build up in the canals. Any fallen branches and similar debris also need to be removed with rakes or nets. Check for algae growth and aquatic weeds that can clog transitions and dry wells at least once in the spring and again in the summer. Warm temperatures, sun exposure, and high nutrient levels in the agricultural or livestock runoff water will all trigger troublesome growth. Add algaecide and herbicide chemicals or remove manually with water rakes and pole saws used for pruning. Be careful not to damage the liner when detaching rooted water plants clinging to substrate or muck.
Muck and sludge that forms at the bottom of any drainage canal or pond will need removal on at least an annual basis for most systems. If there’s rapid flow due to a generous amount of slope, the channels and canals at least may self clean and need no real dredging or sweeping year after year. Ponds and pits are another storage. Even subsurface discharge systems generally need deep cleaning to remove solids at least once every two to five years, depending on the size of the system and the kind of waste water you’re handling. Sludge slows down the transfer of water between parts of the drainage system and can clog filters, screens, and even entire ditches eventually. Keep it under control by installing silt screens around the banks and lining all the channels and canals you can to prevent erosion.
Testing for Leaks
Flexible liner materials like multi-layered RPE are easily tested to determine where leaks are occurring in a drainage system. Since most drainage systems are easier to dry up than a pond or lake, you can use the full range of testing options to locate leaks. Vacuum penetration tests involve placing a high-powered suction device over the seams in the material. If there’s a leak, the air pressure will change and register on the equipment. Electrical tests are also available that pick up on water that’s traveled through the liner material and into the soil below. It’s much harder to use these kinds of leak detection methods on other liner materials like stainless steel and concrete.
