The Montana Department of Environmental Quality estimates that cleaning up three coal ash ponds at the Colstrip power plant will cost as much as $700 million.
The numbers presented in a memo to the state House Energy Committee are the first estimates from the agency on the cost of cleaning up all three ponds that are fed by the power plant, which is slated for closure.
The Billings Gazette reports that the cleanup price could increase if additional steps are needed.
Energy Committee Chairman Dan Zolnikov, of Billings, says the biggest question is who will pay the cost.
Some of that burden will fall on utility customers.
DEQ says it holds $80 million to pay for approved portions of the cleanup in three pond areas.