A lot of attention is paid to leachate control and management at a landfill, and for good reason. Each cell can produce thousands to millions of gallons of wastewater. However, storm water needs just as much attention since it has the potential to become leachate if not handled correctly. Planning for storm water management is the first step to leachate control, regardless of the type of waste or the exact design of the cell. Yet, storm water is often assumed to be far easier than leachate to handle just because it’s not hazardous. Due to a number of factors, storm water containment at a landfill site can be more difficult than expected. Make sure your rain covers are up to these challenges.
Varying Volume
Storm water is even harder to predict in volume than internally generated leachate. Even looking at historical rainfall records stretching back for 100 years can only give you a vague idea of how much water the site might receive in one hour or one day. Without accurate predictions, it’s all too easy to choose a cover that is too thin or non-reinforced and therefore unable to handle heavy rainfall. Flooding conditions shouldn’t overwhelm a rain cover since it’s supposed to shed over the surface anyway, but it can damage weaker materials or cause them to slide out of place. Durable geomembranes are recommended to handle the heaviest rainfall, which can occur even in otherwise arid regions during unusual storm patterns.
Surface Area
The sheer surface area of a landfill’s cell top makes it challenging to keep completely covered. Spreading a single geomembrane out over the entire surface may take a lot of work, but it’s the only way to ensure there’s as little leachate generated as possible. Trying to overlap multiple loose layers of material will only result in runoff leaking under some of the edges. Yet, large landfill cell design makes it challenging to physically expand the cover large enough to keep the rain out. Reinforced geomembrane materials are a good idea for large cell covers since the material has better lay flat characteristics to help smooth out small wrinkles and creases with less work.
Separation from Leachate
Allowing rainwater to mingle with leachate may seem like a natural solution to the issue of dealing with large volumes during storms. Unfortunately, this still creates problems even if the storm water is added without percolating through the mound. First, it greatly increases the total volume of waste that must be held in ponds or other storage spaces. Without mixing with leachate, storm water is usually safe for direct discharge into the surrounding environment. Second, it also allows for reuse of the storm water if it’s needed. Clean water supplies are useful for dust control, waste treatment, and fire control around the landfill, but the water needs to stay clean for these purposes and can’t be mixed with leachates in the process.
Height and Wind
As the pile slowly grows over time, its height can leave it towering over the surrounding landscape. Some working faces on modern landfill cells can reach 300 feet or more in elevation before capping. This means that liners spread across the heights of these mounds must withstand extra wind and plenty of UV exposure as well. If the cell is mounded at the end to maximize filling while stabilizing the fill, keeping covers from sliding off the surface can be tricky. Flexible geomembranes will cling tightly to the surface, reducing wind lifting even as the working face grows in height.
Availability of Cover Material
Not all cover materials are even available or feasible for all landfills to access. Storm water management requires six inches or more of soil in order to give the water time to run off before it penetrates to the compacted trash layer. A thinner cover layer may work for insects or odor while leaving rainwater susceptible to becoming leachate. Yet, not all landfills have enough soil available in the area to truck in the material needed to apply six inches of dirt every single day. Geomembranes are available in almost every part of the world, and the reusable nature eliminates the need to constantly find new sources of dirt for the traditional daily cover routine.
With the right rain cover, both temporary and permanent storm water containment is easier than expected at a landfill. Complete your cell design with the cover materials that last from BTL Liners.
