You’ll need to consider all of your options when choosing a liner for a new or existing canal. Each canal has different needs depending on the soil conditions, size, wall angle and total flow and discharge. While geomembranes, like the products from BTL Liners, are the best choice for the majority of irrigation and power generation canals, additional lining options may work well in conjunction with them for even greater durability and leak protection.
Geomembrane
A durable and plant-safe geomembrane is the optimal liner for irrigation canals. Materials rated as plant-safe by ASTM standards won’t leach out any chemicals or other contaminants that could affect the health of crops. Reinforced polyethylene (RPE) is the best of the geomembranes for canal uses, but the combination low density polyethylene (LDPE) and high-density polyethylene (HDPE) materials can also work well for some designs. BTL Liners offers both kinds of geomembrane products, and more, to help you meet the exact specifications of the project’s geoengineering studies and designs.
Greater Resistance to Winter Damage
Since geomembranes are generally quite flexible, they’re less likely to crack or rip due to the freezing and thawing cycles that can damage clay, cement, concrete, and any mortar-based liners. HDPE and PVC products don’t always offer as much freeze damage protection as RPE, but they can still work in warmer climates.
Light Weight for Easy Installation
There’s no need for large concrete pumping trucks, heavy equipment to lift pre-cast sections in place, or extensive pressure spraying systems when using a geomembrane as your primary liner. The material is light weight and easy to carry in by hand or with relatively small equipment. Installers can spread it quickly for fast installation as well.
Lower Cost
Geomembrane products generally cost only a fraction of the price of concrete liners, mortared bricks or slabs of stone. If there is a limited budget for manufacturing new canals or repairing old ones, choosing a geomembrane product makes the most of allocated funds.
Easy Replacement When Needed
Finally, geomembranes are easy to lift and remove if they eventually need replacement. Some products are also fit to install directly over similar materials without removing the old layer.
Concrete
Concrete is one of the most popular materials for lining canals, especially large ones, of all types. However, it also tends to be the most expensive option and requires a lengthy installation process. It’s also prone to some forms of damage in certain environments. With careful design, concrete lining can be much more durable when coupled with underlayment. Adding a geomembrane as an underlayment is a great way to extend the life of any concrete canal liner. With a solid and impermeable barrier between the concrete and the soil, reactive minerals can’t cause reactions in the concrete that weaken it dramatically.
Without a geomembrane either below the surface or added later as a top layer, concrete still tends to lose a surprising amount of canal water through seepage. This is because concrete is relatively porous and seeps water out through capillary action. Concrete can be sealed, but these sealants aren’t always plant-safe for irrigation purposes. Geomembranes don’t suffer from this problem and won’t break down rapidly due to chemical exposure like pesticide or fertilizer run-off in drainage canals.
The four types of concrete liners used for canals include:
- Cast in situ lining: The most common method for lining concrete canals is to pour the liquid concrete into molds along the sides of the canal and let it flow to the bottom. This requires an extensive curing process of a few weeks before water can enter the canal, and the concrete may need spraying or heating to cure properly without cracking.
- Shotcrete lining: To get a thinner and even layer of concrete that is still strong enough to resist cracking, shotcrete is an ideal process for canal lining. Powdered cement mix is mixed with a spray of water through a special high-pressure tool to blast a perfectly blended concrete product at any surface, horizontal or vertical. Walls are quickly coated evenly, but small mistakes and missed areas can cause leaks from the beginning. This method also requires special equipment and trained operators that aren’t available in all areas.
- Precast concrete lining: For faster installation and no curing time, look for pre-cast sections of concrete that are simply lowered into place and mortared together for a watertight seal. These precast liners still derive the same benefits as the other installations from a geomembrane underlayment. Even those they’re pre-cast and reinforced internally, it’s still possible for shifting soil or rising water to damage the concrete sections. They also tend to cost more than poured installations, but the speed of installation may make up for the cost.
- Cement mortar lining: Cement mortar is only occasionally used on its own to line smaller canals. Most mortar liners feature brick or stone slabs and simply anchor the materials in place and seal them. Mortar liners pair just as well with geomembranes as any other concrete options.
Soil Cement
For a lower cost sealing option, that still offers some of the benefits of pure concrete or cement, it’s possible to mix soil left over from excavation with a thin cement mixture to create soil cement or soilcrete. Soil cement is sprayed onto surfaces like shotcrete, but the soil gives the surface a slightly rougher surface that further lowers the velocity of the canal to reduce total capacity. Cement and concrete are smoother, but they come with a higher cost. Only some soil cement mixtures will stick to geomembranes, but bonding geotextiles between the layers can increase adherence.
Clay
One of the oldest materials used for sealing canals, and preventing seepage, is thick and binding clay. Clay only controls seepage to a certain extent, without the other benefits of concrete or geomembranes. Weeds can still grow through most clay layers and the material can drift over time with the pressure of constant water flow. Applying an appropriate clay product to the canal surface is a process known as puddling. It is easy to leave some areas too thin and still experience significant seepage. However, it can be an affordable option if there’s clay available on-site. It’s not usually compatible with geomembranes, but clay can be used as a ballast for liners that need to remain covered for UV protection and lift resistance.
Rammed earth
Another old-fashioned method for sealing canals, that is still occasionally used today, is known as gleying or rammed earth. By trampling and pounding the right kind of soil, with enough stable clay in it, a mostly sealed surface emerges with no additional material needed. This occurs because the individual soil particles are forced closer together and packed in so the pores between them are much smaller. Water has a much harder time seeping through, but a significant amount of liquid is still lost. Rammed earth canals are easily updated with geomembranes from BTL Liners.
Brick and Boulder
Large cast concrete or clay bricks, shaped slabs of stone, and similar interlocking materials are also an option for covering the walls and bottom of the canal. These materials are much heavier and harder to move than geomembranes, but they also work great as permanent ballasts to significantly extend the already long life of geomembranes. Mortar is required to seal and anchor the large pieces of material, and small cracks can form behind and under bricks and stones where they’re hard to find for sealing.
