Pursuant to a congressional request, GAO reviewed the status of Department of Energy (DOE) efforts to characterize single-shell tank wastes at its Hanford, Washington site, focusing on impediments such as: (1) technological limitations; and (2) safety considerations.

GAO found that: (1) due to the number of unresolved issues, DOE was unlikely to complete the first-phase characterization of the single-shell tank wastes by the 1998 deadline; (2) due to several unanticipated events during the initial characterization phase, the contractor lacked sufficient information to develop a revised waste characterization plan by the November 1990 deadline; (3) although 16 core samples were retrieved by April 1990, the contractor only reviewed and approved 8 data packages in time to support revising the characterization plan; (4) the diversion of single-shell tank resources, such as personnel and the only tank sampling truck, to address higher priority double-shell tank safety issues in February 1991 would delay the scheduled May 1991 sampling of two single-shell tanks until September 1991 and could affect other future samplings; (5) if the revised plan increased the amount of required sampling, the tri-party agreement between Washington, DOE, and the Environmental Protection Agency could be affected in terms of milestone dates and program costs; (6) its analysis of the variance in samples analyzed to date and the statements of DOE and contractor officials supported the view that two samples would not provide an adequate basis for making informed decisions; (7) due to the number of uncertainties, the Washington State Department of Ecology and DOE believed it would take 2 to 3 years to develop a revised waste characterization plan for sampling the balance of the single-shell tanks; and (8) DOE was conducting studies to resolve safety problems associated with potentially explosive wastes.