SPOKANE - The massive cleanup of a century's worth of mining pollution in Idaho's Silver Valley would be cut nearly in half under a proposal Wednesday by the U.S. Environmental Protection Agency.

The EPA released a plan that calls for cutting the cost of the Superfund cleanup from $1.3 billion to about $740 million. The timeframe would be cut from more than 50 years to between 20 and 30 years.

The changes are partially the result of a huge outcry from Silver Valley residents and Idaho politicians. Opponents contend much of the cleanup work is unnecessary, and federal restrictions and the stigma of a Superfund designation have stymied economic growth in the depressed region.

"We had a lot of input from local people concerned about the large scope and cost and timeframe," said Dan Opalski, director of the EPA's regional office of cleanup.

In fact, most of the nearly 7,000 public comments received by EPA about the original cleanup plan, one of the largest in the nation, called for doing less work and getting the job done faster, Opalski said. On Tuesday, the Idaho Legislature debated and then tabled a resolution calling on EPA to finish the work in five years.

But local environmentalists are disappointed the EPA is proposing to do less work in the narrow mountain about 50 miles east of Spokane.

The Coeur d'Alene River Basin is one of the nation's largest Superfund sites, with heavy metals like arsenic and lead poisoning land, streams, wildlife and humans. The wastes washed into waterways and moved downstream.

"It is unfortunate that the EPA caved in to pressure from Idaho and sliced the cleanup nearly in half," said Mike Petersen of The Lands Council. "The legacy of heavy metals contamination will continue, however, and Lake Coeur d'Alene and the Spokane River will have poorer water quality than under the original plan."

Petersen said opponents are ignoring the fact that the cleanup is bringing hundreds of jobs to the sparsely populated valley.

The EPA's original plan to clean up the upper basin was released in 2010. The agency hoped to finalize the new plan this spring and begin the work.

A lawsuit calling for the cleanup was originally brought in 1991 by the Coeur d'Alene Indian Tribe against several mining companies. Agreements have since been reached with several mining companies that had historic operations in valley, creating a trust fund of about $800 million to pay for the work.

Much cleanup work has already occurred around Kellogg, where the pollution was making people sick. Before that work, the Silver Valley was so saturated with pollution that it stripped the hillsides of vegetation and poisoned the blood of children, causing physical and emotional problems that continue.

Opalski said the original plan called for cleanup at 342 mine sites, but the revised plan would clean up 197 sites. He said the cutbacks mean that when the work is done, the area might not qualify to have the Superfund designation removed.

The work may be enough, or it might fall short of EPA requirements, he said.

Among the changes from the original plan, the EPA is dropping a $300 million project to install a plastic liner along portions of the South Fork of the Coeur d'Alene River; active mine sites would be removed from the cleanup; numerous remote mine and mill sites that were found to contain little pollution or did not pose much public risk will be removed from cleanup.