COEUR d'ALENE - It was thought that mine-waste cleanup of the Coeur d'Alene River's upper basin must be almost wrapped up before lower basin work could safely begin.

With limited data, cleanup program managers determined that starting in the lower basin before that time would create a significant risk of lead recontamination.

Problem is, the upper basin cleanup actions could take 30 years.

"Based on more recent data, our current understanding is that of all the lead that appears at Harrison at the mouth of the Coeur d'Alene River, only about 10 percent comes from the sediments in the upper basin," said Bill Adams, Coeur d'Alene team leader for the U.S. Environmental Protection Agency.

This better understanding opens the door for cleanup managers to begin taking action - in selected areas of the lower basin - long before the end of the upper-basin cleanup. And that can happen without significant risk of recontamination from lead from the upper basin, Adams said this week.

The exact timing and location of actions in the lower basin will ultimately depend on modeling the EPA is doing to better understand the fate and transport of metals in the system.

"This modeling will also help us determine which wetlands and lateral lakes are still at risk of recontamination from lead in the lower river bed," Adams said.

The modeling is scheduled to be completed by 2016, which is when the EPA can better identify specific locations and actions that can be taken.

There also is a change of thinking when it comes to whether dredging the Coeur d'Alene River will be necessary or not, Adams said.

"What we've learned is a lot of material is pretty far down in the system, closer to (Lake Coeur d'Alene)," Adams said. "A large percentage of material is already in the lake."

In the next year, a great deal more will be learned about how the sediment containing mine waste is moving down through the system, said Rick Albright, director of the office of environmental cleanup for the EPA's regional office in Seattle.

"There's been a lot of data collection," Albright said.

Recent sampling of the river bed has given scientists a better understanding about where the material is at, and in what quantities, in the system.

Data modeling should be able to answer a lot of questions, Albright said.

Questions like: Are there areas that can be safely cleaned up? Would there be value in spending money on some dredging?

Adams and Albright said dredging would burn through a lot of cleanup dollars.

"Is it important to get that last 4 percent that's in the river out of the river, or maybe you just let it go on to the lake, and then maybe you just cap it when it's in the lake?" Adams said.

Additionally, any dredging in the lower reaches of the river system would be very disruptive to the abundant wildlife, Adams said.

That said, there are still some hotspots in the lower reaches where there are large volumes of waste accumulations.

"So the question becomes: Is it important to go after those specific areas because they may recontaminate some of these lateral lakes," Adams said.

Dredging the river from top to bottom would not likely be worth the expense, Adams said.

"I think the money could be spent in other areas where we could actually see greater improvements than doing something like that," Adams said.

The Coeur d'Alene Trust, set up following a settlement with the mining and smeltering company Asarco, currently has a balance of $523 million for cleanup projects. The initial balance was $433, but it's grown through investments.

Hecla Mining Co. announced Thursday it had fulfilled its Coeur d'Alene River Basin environmental settlement financial obligations, paying the final $41 million. The company has paid a total of $264 million in the settlement, said Mike Westerlund, a Hecla spokesman.

Hecla's settlement was with the U.S. Department of Justice, the Coeur d'Alene Tribe and the state of Idaho.

Of that total, the EPA received approximately $184 million, with the balance going to the state and the tribe.