The Supreme Court on Monday upheld a U.S. government permit to dump rock waste from a gold mine in Alaska into a nearby lake, even though all its fish would be killed.
By a 6-3 vote, the justices said a federal appeals court wrongly blocked the permit on environmental grounds.
Environmentalists fear that the ruling could set a precedent for how mining waste is disposed in American lakes, streams and rivers.
"If a mining company can turn Lower Slate Lake in Alaska into a lifeless waste dump, other polluters with solids in their wastewater can potentially do the same to any water body in America," said Earthjustice President Trip Van Noppen said in a statement.
The Army Corps of Engineers in 2005 issued Coeur d'Alene Mines Corp. a permit to put 4.5 million tons of mine tailings into the lake over a decade. The proposed Kensington mine would be north of Juneau, the state capital.
Under the plan, tailings — waste left after metals are extracted from ore — would be dumped into Lower Slate Lake.
Environmentalists sued to halt the practice, saying dumping the mine tailings in the lake would kill fish. The 9th U.S. Circuit Court of Appeals in San Francisco blocked the permit, saying the dumping is barred by stringent Environmental Protection Agency requirements under the Clean Water Act of 1972.
Inside Tongass National Forest
The Corps of Engineers, not the federal Environmental Protection Agency, has the authority to permit the slurry discharge, and the Corps acted in accordance with the law in issuing the discharge permit to Coeur, Justice Anthony Kennedy wrote for the Supreme Court majority.
The deposits would have raised the height of 23-acre Lower Slate Lake by 50 feet, so the company proposed building a 90-foot-high dam at the site in the scenic Tongass National Forest.
Idaho-based Coeur, one of the world's largest silver producers, argued that depositing tailings in the lake was the most practical and environmentally sound option. It has said it hopes the mine will produce 100,000 ounces of gold a year.
Both Coeur and the state of Alaska appealed to the Supreme Court. The federal government supported their appeals.
Environmentalists argued that modern mines have never been allowed to dump tailings into lakes, and the appeals court ruling confirmed a rule of law in place for more than 30 years.
Writing for the six-member court majority, Kennedy said deference must be given to the reasonable decision by the Corps of Engineers.
Justices John Paul Stevens, Ruth Bader Ginsburg and David Souter dissented.
Activists now hope that President Barack Obama or Congress will repeal a Bush-era rule that they say allowed weakened the Clean Water Act and allowed the Corps to issue the permit.