U.S. environmental regulators said containing toxic waste at a former aluminum smelter in Columbia Falls remains the best plan to protect the environment and human health.
A community group has pushed the U.S. Environmental Protection Agency (EPA) to remove all contaminated soil from the site.
The EPA responded in a letter saying that removing waste from the Columbia Falls Aluminum Company superfund site would expose workers to hazards like cyanide gas.
Officials said it would take up to five years and thousands of trucks and trains to transport contaminated soil 500 miles to a certified landfill in Oregon.
They said that would expose other communities along the way.
The EPA said hauling the waste away would cost between $624 million to $1.4 billion.
The agency prefers to pour an underground concrete wall to contain the waste at the CFAC site. That plan will cost nearly $60 million.