AGRU America Inc. explores landfill closure regulations and requirements, highlighting landfill closure best practices from the perspective of a geosynthetics manufacturer.
Landfill containment is a complicated business. Regulations, leachate and gas production, elevated temperatures, chemical reactions, and liner degradation are considerations that engineers must analyze when designing a landfill containment system. Add to that the complexity of closure and post-closure care, and it becomes clear why new and better solutions are needed.
Landfill and landfill closure regulations
The U.S. Environmental Protection Agency (EPA) mandates the general landfill and landfill closure requirements in the United States. These requirements vary depending on state regulations based on local hydrogeologic characteristics, climate, and the leachate’s expected physical and chemical properties. New landfills must, at a minimum, follow the Resource and Conservation and Recovery Act (1976), which sets the minimum thickness for high-density polyethylene (HDPE) bottom liners to 60 mils (1.5 mm).
Landfill closures have other requirements that compel owners to install a final cover system to minimize infiltration of liquids and soil erosion. First, the permeability of the final cover must be “less than the underlying liner system, but no greater than 1 × 10-5 cm/sec.” This requirement is to help prevent liquids from infiltrating and pooling into the landfill, potentially creating a bathtub effect.
Additionally, the final cover system must:
- Have a permeability less than or equal to the permeability of any bottom liner system or natural subsoils present, or a permeability no greater than 1 × 10−5 cm/sec, whichever is less.
- Minimize infiltration through the closed municipal solid waste landfill using an infiltration layer that contains a minimum of 18 inches (457 mm) of earthen material. This requirement may vary by state.
- Minimize erosion of the final cover by using an erosion layer that contains a minimum of 6 inches (152 mm) of earthen material capable of sustaining native plant growth.
Landfill closure best practices
One of the most important steps when installing a new landfill or final cover system is selecting a manufacturer. The manufacturer must also adhere to best practices/industry norms, which exist after years of trial and error. These practices can ensure your project’s success and impact your bottom line.
Choose a manufacturer that will ship liners in larger rolls. Larger rolls reduce installation complexity by requiring fewer field welds, which reduces overall installation cost and positively impacts the project by creating fewer seams. Fewer seams in the liner also mean cost savings for construction quality control.
When selecting a manufacturer, choose one with a plant close to your landfill site. Manufacturers can have facilities in multiple regions across the United States, allowing you to benefit from reduced shipping costs. The shipping method is just as important as the point of origin. Buyers should also look for adequate protection of the shipment from UV exposure, which can help ensure longer service life for the liners. An astute manufacturer will also utilize robust roll cores to eliminate the possibility of crushed cores during shipment. Crushed cores are hindrances that can slow installations.
Finally, do not underestimate the value of good manufacturing processes and techniques. By choosing a manufacturer that utilizes the best production techniques for consistency, such as flat die extrusion, you can ensure the same high-quality performance throughout the entire length and width of the liner.