It’s not enough to avoid general purpose tarps and stick to geomembranes to find the right landfill cover. Material selection is particularly important for permanent covers for landfills, but it’s also valuable for choosing a temporary cover that lasts beyond just a few months of use. Temporary rain cover use is particularly hard on many materials, but even permanent cover installation can wear out the wrong type of geomembrane. It’s not always easy to detect leaks in a rain cover material until leachate problems have begun. Instead of trying to inspect the materials constantly for signs of leaks, try these suggestions for choosing the right landfill rain cover from the start.
The Limitations of Soil
Soil is the most commonly used cover material. In some areas, it may be sufficient on its own to stop leachate development from storm water. However, soil is highly limited as a cover material, especially for temporary use. First, it’s simply impractical at many sites to supply a constant and steady stream of loose and workable soil. Some sites are too wet and produce mud that is hard to spread, while others just don’t have soil on site. Trucking in purchased soil quickly costs more than investing in reusable cover materials and the equipment to apply and remove them. Second, soil is also a very dusty cover material. With dust already being a major air pollution problem at many landfills, adding more to the air isn’t always a good idea. Finally, soil covers only somewhat stop the penetration of storm water through to the compacted trash below. It’s a fairly permeable material, even with compaction and the addition of stiffening agents. Geomembranes are simply better at stopping the flow of water and conforming to the surface without leaving any gaps open for water.
Why Geomembranes Work Best
Geomembranes are close to impermeable, making them much better at holding water back. When it comes to protecting the working face from rain on the landfill, soil simply can’t handle heavy storms. Erosion is common even before the soil is added, but compaction isn’t enough to keep natural soils from washing away during a storm. Even if the material stays in place, water quickly seeps through the porous surface when given enough time. Some water will run off, but much of it is likely to seep through and become leachate. Geomembranes are flexible enough to cover every inch of the landfill surface, holding back the water no matter where it falls or pools.
Choosing a Geomembrane Material
Most geomembrane materials work well as liners but perform less reliably as covers. This is because they’re weak to UV exposure, a particular problem for temporary rain covers used on a daily basis. The same material that works best for buried and permanent installation, RPE, also happens to work well for temporary and portable rain covers as well.
- RPE (Reinforced polyethylene): Polyethylene, in general, is a good material for covering surfaces like landfill cells because it’s highly flexible and offers plenty of UV resistance. But it’s not the most resistant to damage against daily wear and tear from folding or rolling. RPE is the best choice to overcome that form of damage by relying on the extra durability offered by the reinforced design. Thanks to good chemical resistance and extra tear and puncture resistance, this material can handle months and years of daily cover use without needing repairs. It’s also tough and flexible enough for use in automated cover systems, reducing the need for manual labor to load and unload the rolls.
- HDPE (High density polyethylene): HDPE, in particular, is a poor polyethylene choice for cover material due to its propensity to crack when flexed on a regular basis. It has a stiffer profile that lends it durability and puncture resistance that would be helpful, but that stiffness also causes it to develop stress lines and fractures over time. Even carefully rolling the material can’t keep it from becoming worn from daily use. While it can work as a buried permanent cover or liner material for landfills, it’s definitely not appropriate for use as a temporary daily cover.
- LDPE (Low density polyethylene): While HDPE tends to be a little too stiff to make a good landfill rain cover material, LDPE suffers from the opposite problem. It’s more flexible and conforms better to uneven surfaces like compacted trash, but at the expense of durability and tear resistance. It’s prone to puncturing when used over a rough surface, especially for temporary cover use where it’ll be dragged or stretched out over and over again. Even reinforced LDPE doesn’t offer as much durability as RPE, making it likely to need regular repairs and replacement that drives up the total cost.
- EPDM (Ethylene propylene diene monomer rubber): This thick rubber material is still sometimes used for lining landfills, but only rarely. It’s simply too thick, heavy, and hard to fold or roll to use for cover material for most cell designs. There are also issues with low puncture or crack resistance despite the thickness of the material. It is flexible, but only to a certain point due to the density of the rubber. It may be recommended as a cushion or underlayment material for a cover and rarely as the final top layer itself.
- PVC (Polyvinyl chloride): PVC is still commonly used for lining landfills, but it’s too fragile and prone to tearing to use for temporary rain covers. It’s beginning to fall out of favor as a buried permanent landfill cover for the same reasons. It doesn’t offer as much UV damage resistance as RPE, making it a much more short-lived material for daily cover. Thicker PVC tends to suffer from stiffness issues that make it hard to get a good fit without wind lifting up the edges. Unless RPE materials aren’t available for some reason, avoid PVC for landfill rain covers.
Considering Reinforced Designs
Not all geomembranes are reinforced. Reinforcement is an optional feature that is highly recommended. It helps both temporary and permanent rain covers last longer and better resist tearing. Woven scrim materials are embedded inside the layers of polyethylene material to create a stronger, tougher geomembrane. This material resists stretching better, is less likely to slide down a slope, and avoids wrinkling without losing much flexibility in return. Reinforced materials are particularly recommended for daily covers since they can be much lighter in weight than non-reinforced materials, without sacrificing durability and strength. This makes the daily routine of covering and uncovering the working face much easier on the crew and equipment alike.
With this information, selecting the right landfill cover material should be easier than ever. Still left with some questions about choosing the right geomembrane for your waste management project? Talk with our team here at BTL Liners. Let us put our 40 years of industry experience to good use, by helping you select the right liner and cover materials for all of your needs.
