The state of Idaho and the Coeur d’Alene Tribe, with a boost from the U.S. Environmental Protection Agency, have released a sweeping management plan aimed at preserving the water quality of Lake Coeur d’Alene.

Silver mining and smelting up the Coeur d’Alene River in the past century washed an estimated 75 million tons of cadmium, lead, zinc, arsenic and other heavy metals into the river and then into the lake, where they settled on the bottom.

When the federal government declared the Silver Valley a Superfund site for cleanup, alarmed business leaders and politicians, fearing a tourist backlash, had the lake excluded from the designation. That triggered years of negotiations by the EPA, the state and the tribe on a plan to prevent additional pollution. The EPA served primarily as a mediator over the past two years in the negotiations.

The plan contains no new rules and regulations. Rather, it sets up a series of studies and monitoring operations to nail down the exact cause of pollution, and to propose solutions.

After a 30-day comment period, the plan may be amended and then a final version issued around September. (AP)