There is another effort to exchange federal land for environmentally sensitive land in eastern Arizona.

Senators John McCain and Jeff Flake introduced a bill yesterday that would swap federal land with similar sized parcels owned by the Resolution Copper Company. They say it will bring in billions of dollars.

But Arizona Congressman Raul Grijalva stresses it's impossible to know how much these federal lands are really worth before they are mined.

"So the land exchange, in terms of quantity of land, might seem appropriate, but I guarantee you that the value is far, far from equal," he said. "The taxpayers are going to take a hit on this."

Grijalva says the question of value isn't just a monetary issue. He explains that the federal lands in question hold a special significance to many in Arizona, from lovers of the outdoors to tribal leaders.