Los Alamos National Laboratory

Los Alamos National Laboratory

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Material Disposal Areas

Material Disposal Areas, also known as MDAs, are sites where material was disposed of below the ground surface in excavated pits, trenches, or shafts.


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Material Disposal Areas at LANL

The following are descriptions and status updates of each MDA at LANL. To view a current fact sheet on the MDAs, click on LA-UR-13-25837 (pdf).


MDA A is a Hazard Category 2 nuclear facility comprised of a 1.25-acre, fenced, and radiologically controlled area situated on the eastern end of Delta Prime Mesa. Delta Prime Mesa is bounded by Delta Prime Canyon to the north and Los Alamos Canyon to the south.

MDA A is currently inactive and undergoing corrective action.


MDA B was the Laboratory's oldest waste disposal site. Used from 1944–1948, MDA B consisted of trenches where equipment, clothing, and other waste—contaminated with hazardous chemicals or radioactive material—were buried in a landfill. 

In a project funded by the American Recovery and Reinvestment Act, LANL safely excavated the site inside sturdy metal structures resembling airplane hangars. The excavation of the landfill was completed in September 2011. The total amount of soil and debris excavated from the six-acre site totaled more than 45,000 cubic yards. The excavated areas were backfilled with clean soil, and the materials from the site were shipped to licensed, permanent disposal facilities.


MDA C is a Hazard Category 2 nuclear facility comprised of an 11.8-acre, fenced, and radiologically controlled area situated on a mesa at the head of Ten Site Canyon. The site consists of 7 pits and 108 shafts, with depths ranging from 10 to 25 feet below the original ground surface.

Historically, MDA C was used for the disposal of solids and liquids including uncontaminated classified wastes, hazardous chemicals, and radionuclides.


MDA G is a decommissioned (i.e., removed from service) subsurface site for disposition of low-level waste, certain radioactively contaminated infectious waste, asbestos-contaminated material, and polychlorinated biphenyls.

The site, located on Mesita del Buey, consists of inactive subsurface units that include 32 pits, 194 shafts, and 4 trenches with depths ranging from 10 to 65 feet below the original ground surface.


MDA H is a 70 ft by 200 ft (0.3-acre) fenced area located within TA-54 on Mesita del Buey, a small mesa that lies between Pajarito Canyon and Cañada del Buey. MDA H consists of nine inactive vertical disposal shafts arranged in a line approximately 15 feet inside the southern fence.

From May 1960 until August 1986, MDA H was the Laboratory’s primary disposal area for classified, solid waste. Disposal of solid waste materials at MDA H was restricted to items or materials that were determined by authorized personnel to be both classified and no longer required for their intended use. Liquids were prohibited from disposal.

VOCs and tritium are monitored in subsurface pore gas at MDA H and are reported on in periodic reports. TA-54 monitoring network wells, including those specific to MDA H, will continue to be sampled on a quarterly basis, consistent with the annual Interim Facility-Wide Groundwater Monitoring Plan.


MDA L is located at TA-54 in the east-central portion of the Laboratory on Mesita del Buey, within an
1,100 ft by 3,000 ft (2.5-acre) fenced area known as Area L. MDA L is a decommissioned site.


MDA T is located within TA-21 and is categorized as a nuclear hazard category HC 2 facility. The site includes four absorption beds that received treated radioactive liquid waste, 64 buried shafts used for the disposal of cement-treated radioactive mixtures, and the Retrievable Waste Storage Area used for the storage of cement-treated radioactive mixtures.

The site also includes two industrial wastewater treatment plants and associated subsurface piping and structures. Information on radioactive materials and radionuclides, including the results of sampling and analysis of radioactive constituents, is voluntarily provided to NMED.


MDA U consists of four inactive solid waste management units. In 2005, field investigations were conducted to finalize surface and subsurface chemical and geotechnical characterization of MDA U in accordance NMED-approved MDA U investigation work plan.

NMED concurred that the requirements of the March 1, 2005, Compliance Order on Consent had been satisfied and issued Certificates of Corrective Action Complete with Controls for solid waste management units 21-017(a), 21-017(b), and 21-017(c).

The first control is that the land use at these sites remains industrial. The second control is the prohibition of construction of any structures at MDA U. The Laboratory plans to request the removal of solid waste management units 21-017(a), 21 017(b), and 21-017(c) from its Hazardous Waste Facility Permit in its next request for permit modification.


MDA V is categorized as a radiological facility. It consists of three historic wastewater absorption beds that received effluent from the DP Site radioactive laundry facility from 1945 to 1963, two surface debris disposal sites, and a former septic system and outfall from the laundry facility.

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