RCRA Closure of Materials Disposal Area P, Los Alamos, New Mexico
Material Disposal Area P (MDA-P) is undergoing clean closure under the Resources Conservation and Recovery Act (RCRA) as regulated by the New Mexico Environmental Department. The MDA is located on the north-facing slope of Canyon de Valle, an ephemeral drainage in Technical Area 16 of the Laboratory. It was operated from 1950 to 1984 and received materials from the burning of high explosives (HE), HE-contaminated equipment and material, barium nitrate, construction debris from the D&D of Manhatten-era buildings, as well as empty drums and miscellaneous containers, trash and vehicles. The burning operations were conducted at facilities adjacent to, and south of the MDA. Disposal was conducted by pushing materials over the edge of the engineered slope, resulting in lateral accretion of the landfill and partial encroachment into the stream course. The closure will be conducted in two phases. Phase I, in progress, will be the complete removal of all landfill materials, decontamination of debris, treatment of contaminated soils, and offsite recycle and disposal as appropriate. Phase II will consist of verification sampling, a risk assessment for potential residual contamination, and a Closure Certification report. Phase I removal activities started with a series of test pits excavated in late-1997 to provide data on the southern extent of the landfill for haul road design and construction. Results of the test pits indicate that: 1) pieces of detonatable HE are present in the landfill that pose serious danger to personnel and equipment; and 2) the extent of barium contamination may exceed initial volume estimates by nearly an order of magnitude. To mitigate the dangers of a detonation, a computer-controlled, remotely-operated, 25 metric ton, hydraulic excavator has been assembled, tested and deployed to perform all initial excavation operations. Pieces of HE will be hand sorted from soils to remove the characteristic of reactivity, then field screened for barium, and staged for onsite treatment and stabilization, if required. Phase I is scheduled to be completed in mid-year FY99. Phase II will depend on budgetary constraints.