The U.S. Environmental Protection Agency has taken a step toward curbing discharges associated with a planned open-pit gold and copper mine near Bristol Bay, Alaska.

Proponents of the proposed $6-billion to $8-billion Pebble Mine project, which would be one of the world's largest of its type, say the action is just the latest in a series of EPA efforts to prevent the mine from being developed.

An EPA regional office on July 18, citing the Clean Water Act, proposed restricting all mining-related discharges of dredged or fill material that would harm local streams, wetlands, lakes or ponds. EPA's proposal is open for public comment through Sept. 19.

Environmental groups welcomed EPA's action, but critics say the agency is attempting to veto the project preemptively.

The House Transportation and Infrastructure Committee on July 16 approved a bill that would bar EPA from denying or vetoing Clean Water permits before the Corps of Engineers completes its review.