$800 million to go toward toxic cleanup

"As recently as five years ago, this site dumped the equivalent of 150 tanker cars full of toxic metals into the Sacramento River each day during winter storms," said Felicia Marcus, a regional administrator for the Environmental Protection Agency.

The cleanup has cost more than $200 million so far.

The site near Redding, about 170 miles north of Sacramento, was an active copper mine for more than 100 years and contains miles of tunnels, said Tom Bloomfield, an EPA attorney. The tunnels expose iron sulfate in the pyrite deposit below the mountain to water and the oxygen in the air, forming sulfuric acid.

The funding will ensure that 95 percent of the water coming from the defunct mine will be treated before it reaches the Sacramento River system, EPA officials said.

The treatment plant costs about $4.5 million a year to run and will have to be operated "in perpetuity," said Winston Hickox, head of the California EPA.

The site probably will never be completely cleaned, Hickox said, adding the best solution is to capture and treat the runoff before it reaches the river.

The water that flows out of the mine is extremely acidic, with a pH level of 0.5. The closest previous measurements were in volcanic lakes, where the acidity formed naturally, scientists say.

Scientists say the pollution problems were compounded by a microbe that thrives in the highly acidic conditions. The microbe, discovered earlier this year, speeds up the dissolution of iron in the water.

The Iron Mountain Mine is one of about 1,200 sites in the federal Superfund program, which aims to force businesses to pay to clean up pollution they created or contributed to.

The mine made the list in 1983, when it was owned by Stauffer Chemical Co. Stauffer was absorbed by the French company Rhone Poulenc, which in turn merged in 1999 with a German company, Hoechst, to form Aventis, one of the world's largest chemical, pharmaceutical and biotechnology companies.

Aventis, based in France, agreed to pay $160 million now for an insurance policy that will pay up to $300 million in cleanup costs over the next 30 years if it is needed, plus a final $514 million payment in 2030.

In addition, the company has agreed to drop efforts to recover $150 million it already has spent on cleanup since 1989, Bloomfield said.

The agreement releases the company from future liability, he said.