The $115 billion forecast of the future costs to clean up the Department of Energy’s Hanford site in Washington is likely low, an advisory body has said.

Reactor building demolition at Hanford. Source: DOEIn a letter sent to the DOE Friday, the Hanford Advisory Board said the estimate presented in the 2011 Hanford Lifecycle Scope, Schedule and Cost Report omits the costs of some cleanup tasks and uses low-end cost estimates for many others, the Tri-City Herald reported.

The Hanford facility produced plutonium for the military until 1987, and its decommissioning has involved the removal of reactors and the cleanup of buried waste. According to the DOE, the project employs 11,000 workers. The lifecycle report, required under an agreement DOE reached with the state of Washington and the Environmental Protection Agency to extend cleanup deadlines, tallies costs until 2060, when cleanup is expected to be complete, and maintenance of landfills for 30 years after that.

The advisory board wrote that the estimate does not include costs associated with further cleanup along the adjacent Columbia River, removal of waste in unlined trenches and mitigating soil contamination from underground tanks. In future reports, which are required yearly by law, the panel recommended further information on the costs of delaying or expediting elements of the project.