[en] As a result of past Department of Energy (DOE) weapons material production operations, Hanford now stores nuclear waste from processing facilities in underground tanks on the 200 area plateau. An agreement between the DOE, the Environmental Protection Agency (EPA), and the Washington state Department of Ecology (the Tri-Party Agreement, or TPA) establishes an enforceable schedule and a technical framework for recovering, processing, solidifying, and disposing of the Hanford tank wastes. The present plan includes retrieving the tank waste, pre-treating the waste to separate into low level and high level streams, and converting both streams to a glass waste form. The low level glass will represent by far the largest volume and lowest quantity of radioactivity (i.e., large volume of waste chemicals) of waste requiring disposal. The low level glass waste will be retrievably stored in sub-surface disposal vaults for several decades. Assuming the low level disposal system proves to be acceptable, the disposal site will be closed with the low level waste in place. If the disposal system is not acceptable, then the waste will be subject to possible retrieval followed by some other disposal solution. Westinghouse Hanford Company is also planning to emplace the waste so that it is retrievable for up to 50 years after completion of the tank waste processing