Mining will be barred for 20 years on public lands near the Fort Belknap Indian Reservation in Montana after U.S. officials withdrew the land from future mining.

The Associated Press reported that more than $80 million has been spent on reclamation from past mining contamination at the Zortman-Landusky Mine site now administered by the Bureau of Land Management.

Canada-based mining company Pegasus Gold Inc. declared bankruptcy in 1998, leaving cleanup at the site to U.S. taxpayers.

The BLM has previously said the remaining clean up work could cost about $70 million and involve moving millions of tons of waste rock and treating hundreds of millions of gallons of water in coming decades.

Contaminated water from the shuttered mine site has flowed downstream to the Fort Belknap reservation and fouled its water. Treatment of mine water to prevent further contamination will continue indefinitely, the BLM said in announcing the Sept. 9 withdrawal.

About 5.4 square miles were withdrawn from mining in 2000. That action expired in 2020.

A proposal for a new withdrawal on the remainder of the land – about 1.4 square miles – is pending.

In July, state regulators proposed a $517,000 penalty for illegal mine exploration work in the Zortman-Landusky cleanup area by two individuals, Luke Ployhar and Owen Voigt, and two companies, Blue Arc and Legacy Mining. The fine has not been finalized and negotiations on a potential settlement with the men and companies are ongoing, said Montana Department of Environmental Quality spokesperson Moira Davin.