HELENA, Mont. (AP) — Environmental regulators are moving toward permitting a copper mine in central Montana along a tributary of one of the state’s most popular recreational rivers after finding the mining company would be able to mitigate any harm to groundwater, creeks and the Smith River.

The Department of Environmental Quality issued its thorough environmental review Friday that says Tintina Montana would have to mitigate the potential for mining activity to reduce the flow of Coon Creek near the proposed Black Butte Copper Mine near White Sulphur Springs.

“When Tintina pumps groundwater out of the mine, our analysis shows that surface water will be depleted, and it’s critical that those depletions are replaced by another water supply so that existing water users are protected,” said John Tubbs, director of the Department of Natural Resources and Conservation.

The DNRC has preliminarily granted a permit for Tintina to store spring runoff in a reservoir to release into streams later. It has also given the preliminary OK for area ranches to sell some of their existing irrigation rights to Tintina to supplement stream flows or recharge the aquifer, Tubbs said.

The DEQ’s “preferred alternative” also calls for Tintina to backfill mined areas to prevent any new paths for groundwater to flow.

The Final Environmental Impact Statement is not a final decision, but will help the DEQ make decisions on hard rock mining, air quality and water discharge permits sought by Tintina. The agency cannot issue its Record of Decision until at least 15 days after the publication of the final EIS, said Rebecca Harbage, public policy director for the DEQ.

The proposed underground mine is on private land and would extract 15.3 million tons (13.8 million metric tons) of copper-laden rock and waste over 15 years — roughly 440 tons (400 million metric tons) of copper-rich concentrate a day. It is located near Sheep Creek, a waterway that feeds into the Smith River some 19 miles (31 kilometers) away.

Proponents say the mine would be an economic boon to the area, but conservation groups argue the mining operation would pollute and de-water the Smith River and harm its blue ribbon trout fishery. Trout Unlimited released a statement Friday opposing the final EIS.