Leachate ponds often look deceptively simple. If they’re designed to hold relatively diluted leachate, they may even appear like a natural pond with healthy vegetation around the edges. However, they must be lined properly to protect the environment and serve their purpose as a waste disposal unit. Without proper lining, the slow loss of water through the soil will only risk long-term damage that costs thousands of dollars to remediate. Choose a geomembrane you can trust as a liner for leachate ponds and other parts of the waste containment system with these tips.
Seepage
Seepage sounds innocuous enough because it’s simply the word that describes the movement of water through the soil. Even the most tightly packed, compacted clay still has invisible gaps between the particles of soil. As gravity pulls on the water resting against the soil, it will eventually travel down through the material and seek out a lower place to gather. This is how underground water deposits form and recharge, but you don’t want landfill leachate becoming part of that water cycle. Flexible polymer materials are the best way to combat seepage in all types of soil because they conform to the natural curves of the ground while offering a high level of impermeability.
Groundwater Supply
Landfills are often built near housing communities, businesses, and even industrial areas to limit transportation costs for heavy waste. Even if they were sited far from past development to isolate hazardous waste, residential areas often spread to surround once rural waste facilities. This means that the groundwater supply under a landfill is often tapped and used as an important supply for drinking water, irrigation, or industrial processes. Contaminating that water supply with chemicals or heavy metals could lead to costly fines if you impact surrounding homes and businesses. This still applies even if it occurs many years after the landfill is closed, making leachate control essential for decades afterward.
Structural vs Lining Materials
Don’t mistake materials added to leachate pond designs for structural support as the impermeable liner intended for seepage and leak control. Concrete and asphalt are two materials commonly used to stabilize the banks, in particular, and reinforce berms installed around the edges of a landfill for secondary containment. However, neither one of them offers the impermeability to truly control where the leachate ends up. They may also react with various compounds and salts in the leachate mixture to become more porous as time goes by. As long as an appropriate and impermeable geomembrane is installed underneath, there’s no need to be concerned that this will trigger leaking.
Impermeability
Speaking of impermeability, it’s hard to find an absolutely impermeable material because almost all materials eventually allow some amount of water through its surface. However, non-woven polymer geomembranes like the RPE liners from BTL Liners are some of the most impermeable materials still practical to install in the field. They can hold water back for decades without losing a drop as long as they’re kept intact and installed correctly in the first place. These liners meet or exceed requirements for most leachate ponds since they’re eventually pumped out or evaporated to the point where they can be filled and capped in place. With the right amount of impermeability for the liner of the leachate pond, owners can rest assured that there’s no leaking or seeping going on as the years pass.
Choosing the Right Liner Material
Of course, not all geomembranes offer the same benefits when used as a liner for a wastewater pond. Leachate ponds in particular are tricky to match with a liner because of the difficulty of predicting the exact mixture of chemicals and compounds that might react with the materials. Choosing the wrong material, or even just the wrong type of liner reinforcement method, could lead to serious failures that release thousands of gallons of concentrated wastewater. With leachate already being far more concentrated than most sewage, it’s worth taking the time to make the right choice. Here are some of your options, listed from worst to best.
- EPDM (ethylene propylene diene terpolymer): This liner is referred to as rubber roofing membrane, but it’s also commonly repurposed for pond lining. As this description suggests, it’s far from ideal for lining a pond. The thickness that gives it durability as a roofing material also makes it heavy, stiff, and hard to conform to the shape of a leachate pond. It’s also likely to react to chemicals and heavy metals in the wastewater supply, leading to a shortened lifespan for the liner. Don’t install EPDM materials in leachate ponds unless they’re being used as an underlayment or cushion rather than a primary liner.
- PVC (polyvinyl chloride): PVC is one of the most popular pond liner materials among both industrial and small-scale projects. However, it’s still not a good choice for most demanding projects, including leachate ponds. The exposed design called for by most engineers, for easy cleaning and maintenance, is hard on PVC pond liners and tends to lead to leaking early on in the lifespan of the leachate pond. PVC is also reactive with some chemicals and doesn’t always respond well to the weight of compacted trash pressing down on it, making it a poor choice for leachate collection systems in general. Save PVC for pipes, tubes, and other parts of the sump transfer system rather than for lining large scale structures like ponds and collection basins.
- HDPE and LDPE (high- and low-density polyethylene): Both HDPE and LDPE geomembranes can be suitable for landfill collection systems, but they’re not necessarily the very best choice either. LDPE is more flexible and lighter but suffers from reduced strength and tear resistance when compared to other choices. HDPE is stiffer and stronger and trades that for reduced flexibility and extra difficulty during installation. If you’ve already settled on a polyethylene liner product to take advantage of the chemical and UV resistance, consider upgrading from either of these two options to a reinforced polyethylene material.
- RPE (reinforced polyethylene): For the best control of leachates and long-lasting ponds, choose reinforced polyethylene. The reinforced design offers the best tear and puncture resistance, reducing the chances of a leak over the lifespan of the leachate pond. Even aggressive tree roots and shifting trash can’t threaten this kind of tough liner material. It’s also easier to install than other materials, combining both flexibility and the stiffness needed to keep from slipping off smooth basin sides. Few materials are as easy to install in ponds of any kind as RPE, speeding up the construction of new leachate ponds when they’re needed in a hurry.
If you still need advice on what to do about lining your leachate ponds, turn to our expert team here at BTL Liners. Our team can connect you with the liners you need to build secure and easy to maintain leachate collection systems, from the first layer of material under the landfill cells to the furthest evaporation pond. Let us pair you with the right product depending on whether you plan to use exposed or buried installation methods. We also carry reinforced materials ideal for landfill covering and capping, making us a one-stop shop for your leachate containment needs.
