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EPA Regulations for Landfill Liners

Garbage ends up in landfills. As the garbage decomposes it creates a nasty byproduct called leachate, which is mixed and solid pieces of waste that are soluble and as such can leak from the landfill. For this reason, a specially designed liner is required for all landfills unless proven that harmful leachate will not leak out.

  1. Function of Landfill Liners

    • The EPA requires that a landfill liner prevent releases of leachate that exceed maximum contaminant levels (MCLs) for selected chemicals such as arsenic, endrin and lead. MCLs are standards set by the EPA to protect groundwater from contamination that poses risks to human health and the environment. The safe level for arsenic is .05 mg/liter.

    Liner Design

    • A landfill liner is constructed to prevent leachate from reaching soil and groundwater. Three levels of protection are implemented: two layers that trap and filter chemicals and a system of pipes that transports captured leachate for treatment.

    First Layer

    • The first layer of the liner is required to filter the immediate leaching chemicals. It is a 30-mil flexible membrane that can be molded to varying slopes of bowl-shaped landfills. The selected material must be appropriate for the types of chemicals that may leach from the landfill as determined by laboratory analysis. It is the first barrier of protection.

    Leachate Collection System

    • Placed below this membrane layer is a leachate collection system that is required to catch any pollutants that may have escaped through the flexible membrane layer above it. The pipes can be perforated on the top to capture soluble chemicals. Pumps are employed to move the leachate out of the landfill where it can be treated to safe levels.

    Lower Liner Layer

    • Below the collection piping system lies a 60-mil thick polyethylene membrane that has "direct and uniform contact" with a minimum of two feet of compacted soil with little hydraulic conductivity, meaning liquids do not drain easily. This is the final layer of protection against leachate reaching soil and groundwater. However, collection and treatment systems are also placed at the landfill perimeter not more than 150 meters from the landfill boundary.

    Other Liner Considerations

    • The EPA may require more stringent design criteria before issuing a construction permit. Site-specific conditions such as increased hydraulic conductivity of soil and the directional flow of groundwater may warrant stronger membranes and collection systems. Minimum requirements are more suitable for landfills located in areas with existing groundwater quality that has been contaminated by other sources or was not usable as a result of naturally occurring contamination, such as mineral-rich geology.

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