Despite the risks of leachate, it’s an unavoidable part of any landfill. Storing any kind of waste will result in leachate creation, even if there’s no organic waste mixed in to release water as it decomposes. Designing landfill cells correctly from the start is the key to managing leachate and redirecting it to a safer storage area. Leachate ponds can only receive the wastewater produced by a landfill if there’s a complete collection system to consolidate it. By considering every part of the cell design, from the liner at the base to the rain cover at the top, it’s possible to limit leachate production and control where every gallon of it ends up.
Original Landfill Designs
The earliest landfills were attempts to deal with localized dumping habits that were leaving residential areas full of waste. While directing all the municipal waste of early cities to a single dumping point was an initial improvement, soon operators began to see the negative effects of unmanaged dumps. Piling the mixed trash on the surface of the ground caused rainwater to quickly trickle through the loose material and run off to the surrounding area. Digging pits and compacting modern trash cells results in more control of the leachate, but it’s not enough on its own. Modern landfill cells have many other features that help them stand out over the old-fashioned open tipping design.
Enclosed Cells
Creating enclosed cells was the greatest improvement in landfill design to keep leachate design. Cells are simply units of storage space set aside for holding a specific amount of waste. They’re smaller than open ground dumps since they’re designed to be compacted each day. Compaction keeps the waste as tightly packed as possible, which reduces the risk of it blowing away, saves space, and reduces water infiltration. Open landfills were hard to impossible to compact because waste would simply slide out to the sides. Thus, cells feature excavation and sloped sides to contain both solid and liquid waste. Yet, a cell excavated into the ground isn’t contained or sanitary until it has a leachate collection system installed.
Collection Systems
When it comes to protecting the environment, leachate collection systems are as important as the final rain cover installed over the top. Some amount of liquid is inevitable, and it must have somewhere to collect, so it can be redirected to leachate storage ponds and other devices. Collection systems generally consist of multiple layers of permeable geotextiles, porous materials like gravel, and perforated pipes that actually collect the liquid. A final impermeable liner layer must be placed below to prevent leachate from escaping if it flows past the rest of the system. Proper grading ensures that all liquid that settles against this bottom liner still eventually flows out to the leachate pond. While an extensive collection system can handle a large amount of leachate during peak flow, it still has a limit to the amount. That’s why even the most advanced leachate collection systems have to be backed up with rain covers, both on a temporary and permanent basis.
Impermeable Liners
Without an impermeable barrier at the very bottom of the landfill cell, it can’t contain leachate on a long-term basis. No amount of rain cover material can entirely control leachate production. This is because the liquid is produced internally through decomposition as well as externally from storm water. While a cover may be enough to keep storm water out of a landfill cell, it won’t do anything to contain leachate produced within. Only an impermeable liner material like RPE can complete the base of a collection system, making it essential to pair with every landfill rain cover.
Daily Cover Routines
One of the most important features of the modern landfill cell is the daily cover routine. At the end of each day, trash is deposited, compacted with heavy equipment and covered. Many facilities only use a thick layer of soil; a cover material that has many limitations. This material is dusty, hard to locate, and expensive to transport in large volumes. Using a flexible geomembrane is a far better choice for daily cover. Flexible, polymer materials can be reused day after day, conform to the surface to control wind lifting and odors, and offer better seepage control than soil alone.
Why Limit Exposure?
Covering fresh trash, from a day’s worth of dumping, does more than just help control leachate. It’s also essential for keeping odors from becoming a nuisance around the site. Many landfills also manage fire risk by covering the freshest trash so it can’t generate heat in the sun. Not only does a temporary daily cover keep trash from blowing off of the working surface, but it also keeps insects out so they can’t lay eggs and carry disease. By keeping insects away, you also reduce the chance of wildlife or birds being attracted to the waste. Finally, limiting exposure to the trash with a durable rain cover helps protect the workers responsible for inspecting and compacting it each day.
Don’t let old-fashioned landfill methods threaten groundwater or soil health around the facility. Modern landfill design may require both liners and rain covers, but they’re both available from BTL Liners. Choose our durable geomembrane products to keep the cell as leak-proof as possible for long-term leachate containment.
