Landfill containment is a complicated business. Regulations, leachate and gas production, elevated temperatures, chemical reactions, and liner degradation are considerations that engineers must make 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. This is the first of a series on landfill closure best practices.
This article explores landfill closure regulations and requirements, highlights best practices from the perspective of a geosynthetics manufacturer, and describes innovative landfill containment solutions by AGRU.
Landfill and landfill closures regulations
The 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 minimum, follow the EPA’s Resource and Conservation and Recovery Act, which sets the minimum thickness for high-density polyethylene (HDPE) bottom liners to 60 mils (1).
Landfill closures have other requirements that require 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 1.0 x 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 (2):
- 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 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 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 or 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 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.
Are you looking for a geosynthetics manufacturer with innovative landfill containment solutions? Consider AGRU.
Innovative landfill containment solutions by AGRU
AGRU has been in the business of manufacturing plastic products and geosynthetics for more than 70 years. As the Plastics Experts, AGRU emphasizes the development of robust solutions that combine a variety of plastic technologies and technical expertise. Three recent AGRU innovations include FrictionSpike, CleanSeam, and Conductive Liner.
FrictionSpike is a first-in-class, patented multi-tiered geomembrane solution that enables engineers to increase slope angles, maximize containment air space, and increase Factor of Safety. Owners can use FrictionSpike for landfills, mines, and regions with exceptional interface shear strength requirements to meet project stability conditions and unlock new capabilities and designs.
CleanSeam is a protective strip on HDPE liners that installers can peel away to dramatically reduce the time required to prepare the liner’s welding zones.
Conductive Liner is a coextruded geomembrane that contains a carbon layer that conducts an electrical charge, which is a requirement for Construction Quality Assurance Testing using ASTM D7240. These product innovations exemplify how AGRU has remained at the forefront of the geosynthetics industry. By choosing AGRU, you can access an expansive catalog of high-quality products. AGRU also offers customer service and technical feedback, including detailed drop-in specifications that your engineer can use in planning a design.
At AGRU, we strive to manufacture the highest quality HDPE and LLDPE liners, meeting or exceeding GRI GM13/17 test values. Additionally, AGRU HDPE and LLDPE liners are rolled on 23’ wide plastic cores to ensure ease of installation by requiring fewer welds. Are you planning the installation of a new landfill or considering a closure? Reach out to an AGRU representative for guidance and assistance in choosing the best solutions for your job.
- “Part 258 Subpart D – Criteria for Municipal Solid Waste Landfills.” Electronic Code of Federal Regulations. Accessed online 23 March 2022. https://www.ecfr.gov/current/title-40/chapter-I/subchapter-I/part-258.
- “Part 258 Subpart F – Criteria for Municipal Solid Waste Landfills.” Electronic Code of Federal Regulations. Accessed online 23 March 2022. https://www.ecfr.gov/current/title-40/chapter-I/subchapter-I/part-258/subpart-F.