Key Terms

Aquifer refers to the underground layer of permeable materials (such as rocks, gravel, or sand) through which the groundwater flows.

Containment layer refers to a layer of the containment system. For example, the containment layers for a waste pile could include two layers of an impermeable lining and a concrete dike that surrounds it.

Containment system refers to a system of barriers installed to prevent a hazardous waste spill from being released into the environment (for example, tanks, liners, dikes, or berms).

Floodplains are areas, generally near streams or rivers, that may flood during periods of heavy rain, snow, or other precipitation.

Groundwater refers to the water held in the uppermost aquifer (closest to the surface). It is stored and flows around the rocks and other materials. The contamination of groundwater is one of the primary concerns of the RCRA law.

Incompatible wastes are combinations of wastes that are prone to reactions or ignitions when mixed together.

Leachate is the liquid that has percolated or drained through waste. Leachate includes any particles or other components suspended in the liquid.

Manifest system refers to a tracking mechanism using a manifest for each shipment of hazardous waste to ensure that it reaches its intended designation.

Migration of water refers to the movement of water as it travels underground in the aquifer.

Post-closure is the period of time, typically 30 years, for which the owner or operator of the closed facility must make financial and logistical arrangements for ongoing groundwater monitoring and facility maintenance.

Regulated unit is the RCRA term for solid waste management units that are used to treat hazardous waste. Examples of regulated units include containers, waste piles, and landfills.

Salt domes are dome-shaped formations within sedimentary (layered) rock. These domes are made up of minerals (primarily salt) that has been pushed upward into the rock layer. Salt domes often form pockets where petroleum and natural gases may collect.

Seismic faults are breaks in the Earth's surface where earthquake activity is more likely to take place. These breaks are called "seismic fault lines," or simply "fault lines."

TSDF is an acronym used in RCRA regulations that refers to transfer, storage, and disposal facilities that handle hazardous waste.

Unit-specific regulations are the RCRA regulations that apply to specific solid waste management regulated units. For example, unit-specific regulations include regulations for containers, tanks, waste piles, landfills, incinerators, and others.

To learn more about RCRA visit our RCRA Hazardous Waste Safety Online Training web page.