The Supreme Court is delving into a case that could decide whether hard-rock mine operators legally may pump metal waste directly into lakes and rivers rather than man-made settlement ponds.

In 2007 an appellate court ruled that the Army Corps of Engineers lacked authority under the Clean Water Act to issue a permit to an Alaska company to pump 4.5 million tons of rock waste into a lake near Juneau.

During oral arguments on Jan. 12 before the high court, attorneys for environmental group Earthjustice argued the Environmental Protection Agency has tougher requirements governing mining waste than does the Corps. Mining company Coeur Alaska said the agencies did extensive analysis before deciding to issue the permit.