Identify one key regulatory requirement for hazardous waste landfills.

One key regulatory requirement for hazardous waste landfills is the necessity of a liner system designed to prevent leachate from contaminating soil and groundwater. This requirement is essential because hazardous waste can produce leachate—a contaminated liquid that results from rainwater or other liquids filtering through the waste material. If not properly contained, leachate can seep into the surrounding environment, posing significant risks to soil and water resources. The liner system typically consists of multiple layers of materials, often including clay and synthetic liners, which provide a barrier against the migration of contaminants.

Ensuring that hazardous waste landfills utilize a proper liner system is part of the regulatory framework established under the Resource Conservation and Recovery Act (RCRA) in the United States. This federal law mandates strict design and operational standards to protect human health and the environment from the dangers posed by hazardous waste. Therefore, the implementation of a liner system is critical in managing the potential risks associated with hazardous waste disposal.