After permitted landfills close, they must be monitored and managed to protect the environment and human health. Precipitation can percolate through landfilled waste and create contaminated fluids (leachate), and the waste may continue to generate gases as the waste decomposes. Leachate and gases must be managed properly to avoid polluting groundwater or surface water or affecting nearby structures.
Minnesota rules do not describe a process or criteria for allowing landfills to exit postclosure care and move into the less stringent phase, called custodial care. A clear and consistent process is needed so landfill owners and operators know what to expect when planning closure. The evaluation should determine when a landfill poses no health or environmental threats and can safely exit the postclosure care period.
Permitted landfills in Minnesota have a four-phase lifecycle.
- Open/Active — When the landfill is open and receiving waste. Landfills must obtain an MPCA permit, and the permit application must include landfill closure and postclosure care plans. The plans must be approved and updated, as necessary, whenever the permit is reissued.
- Closure — When the landfill is at capacity or the owner chooses to no longer receive waste. The closure plan is implemented, and a cover is installed over the waste. The MPCA must certify the closure and document the postclosure care, monitoring, testing, and reporting requirements for the site in a closure document.
- Postclosure care — Begins when the MPCA certifies the closure and lasts a minimum of 20 years. The MPCA may modify the closure document to extend the postclosure care period. Requirements include:
- Maintaining the landfill cover
- Identifying and correcting erosion
- Continuing to operate the leachate or gas collections systems
- Monitoring and reporting of environmental data
- Prohibiting any use of the site that will disturb the integrity of the final cover
- Custodial care — The site owner must continue to maintain the site and protective systems.
New guidance for landfill operators
The MPCA is developing guidance for evaluating when closed landfills may exit the postclosure care phase and move into custodial care. The new guidance will:
- Establish criteria that is specific, consistent, and flexible to site specific conditions
- Detail the performance goals and data needs for each landfill system, including:
- Landfill cover
- Leachate collection
- Gas collection
- Environmental monitoring
- Create a consistent process so landfills can plan ahead and reach goals in a timely manner
MPCA will present draft guidance once it's been developed, and provide opportunities for stakeholder feedback.