Hazardous Waste Land Disposal Units (LDUs)
Land Disposal Restrictions Program
EPA's Land Disposal Restrictions (LDR) Program works to minimize potential environmental threats resulting from land disposal of hazardous waste. The LDR Program achieves this mission by establishing hazardous waste protocol and treatment requirements that make waste safe for land disposal.
EPA Study: Industrial Surface Impoundment in the United States (March 2001, EPA 530-R-01-005)
Land Disposal Restrictions for Hazardous Wastes: A Snapshot of the Program (PDF) (4 pp, 339K) - This brochure provides an brief overview of hazardous waste land disposal and provides a brief introduction to the LDR requirements.
Land Disposal Restrictions: Summary of Requirements (PDF) (119 pp, 905K) - This document provides a summary of the requirements of the LDR Program under 40 CFR Part 268. The document is organized in a question-answer format to clarify and explain how the regulations work.
Subtitle C of the Resource Conservation Recovery Act (RCRA) creates a cradle-to-grave management system for hazardous waste to ensure proper treatment, storage, and disposal in a manner protective of human health and the environment.
Under RCRA Section 3004(a), Congress authorized EPA to promulgate regulations establishing design and operating requirements for land disposal units (LDUs). The requirements are intended to minimize pollution resulting from the disposal of hazardous waste in or on the land.
- Surface impoundment
- Waste pile
- Land treatment unit
- Injection well
- Salt dome formation
- Salt bed formation
- Underground mine
- Underground cave
Specific regulations have been developed for four types of land disposal units under Subtitle C of RCRA (40 CFR Parts 264/265). These units include:
Landfills are excavated or engineered sites where non-liquid hazardous waste is deposited for final disposal and covered. These units are selected and designed to minimize the chance of release of hazardous waste into the environment. Design standards for hazardous waste landfills require a double liner; double leachate collection and removal systems (LCRS); leak detection system; run on, runoff, and wind dispersal controls; construction quality assurance (CQA) program. Liquid wastes may not be placed in a hazardous waste landfill. Operators must also comply with inspection, monitoring, and release response requirements. Since landfills are permanent disposal sites and are closed with waste in place, closure and post-closure care requirements include installing and maintaining a final cover, continuing operation of the LCRS until leachate is no longer detected, maintaining and monitoring the leak detection system, maintaining ground water monitoring, preventing storm water run on and runoff, and installing and protecting surveyed benchmarks. (See 40 CFR Parts 264/265, Subpart N)
Surface Impoundments are natural topographic depressions, man-made excavations, or diked areas formed primarily of earthen materials used for temporary storage or treatment of liquid hazardous waste. Examples include holding, storage, settling, aeration pits, ponds, and lagoons. Hazardous waste surface impoundments are required to be constructed with a double liner system, a leachate collection and removal systems (LCRS), and a leak detection system. To ensure proper installation and construction, regulations require the unit to have and follow a construction construction quality assurance (CQA) program. The regulations also outline monitoring, inspection, response action, and closure requirements. (See 40 CFR Parts 264/265, Subpart K)
Waste Piles are non-containerized piles of solid, non-liquid hazardous waste that are used for temporary storage or treatment. In addition to the standard double liner and leachate collection and removal systems (LCRS), waste piles are required to have a second LCRS above the top liner. Waste piles must also have run on and runoff controls, be managed to prevent wind dispersal of waste, and are subject to inspection, monitoring, and release response requirements. When closing a waste pile, all waste residue and contaminated soils and equipment must be removed or decontaminated. (See 40 CFR Parts 264/265, Subpart L)
Land Treatment Units use naturally occurring soil microbes and sunlight to treat hazardous waste. This is accomplished by applying the hazardous waste directly on the soil surface or incorporating it into the upper layers of the soil in order to degrade, transform, or immobilize the hazardous constituents. Land treatment units rely upon the physical, chemical, and biological processes occurring in the topsoil layers to contain the waste. Because of this, the units are not required to have liner systems or an leachate collection and removal systems (LCRS). Before hazardous waste can be placed in a land treatment unit, operators must complete a treatment demonstration to demonstrate the unit's effectiveness and ability to treat the hazardous waste. Once operational, operators must monitor the unit (unsaturated zone monitoring) to ensure that all hazardous constituents are being treated adequately. Unit closure consists primarily of placing a vegetative cover over the unit and certifying that hazardous constituent levels in the treatment zone do not exceed background levels. (See 40 CFR Parts 264/265, Subpart M)
The remaining types of land disposal units are categorized as miscellaneous units:
Injection Wells are regulated primarily under the Safe Drinking Water Act and the Underground Injection Control (UIC) Program. (See 40 CFR Part 265 Subpart R or Part 264 Subpart X)
Salt Dome Formations, Salt Bed Formations, Underground Mines, and Underground Caves are geologic repositories. Because these units vary greatly, they are subject to environmental performance standards, not prescribed technology-based standards (e.g., liners, leachate collection systems, leak detection systems). The standards require that these miscellaneous units must be located, designed, constructed, operated, maintained, and closed in a manner that ensures the protection of human health and the environment. (See 40 CFR Part 264 Subpart XMiscellaneous Units)