Associated Press - September 8, 2008 4:44 PM ET

BOISE, Idaho (AP) - The U.S. Forest Service approved a plan to remove hazardous sediment from a defunct 43-year-old phosphate mine that's sent selenium-tainted water into the Blackfoot River and wiped out Yellowstone cutthroat trout in at least 1 of its tributaries.

Canadian fertilizer giant Agrium will spend $446,000 to restore sediment retention ponds, among other measures, as part of initial steps to address problems at its North Maybe Mine near Soda Springs.

Agrium has struggled with selenium before.

Just miles away, selenium-poisoned water from 1 of the company's other southeastern Idaho mines forced several horses to be euthanized in the 1990s.

Now, selenium from the North Maybe Mine is blamed for killing wild trout in East Mill Creek and for polluting stretches of the Blackfoot River downstream.

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