Environmental groups and Northwest Arctic village residents are contesting a key federal permit needed for the state's largest mine to continue operating.

The Red Dog Mine operator said it might have to suspend production later this year if the permitting dispute -- involving water pollution discharges at the mine -- isn't resolved this spring.

Stopping production at the zinc, lead and silver mine near Kotzebue would have implications for Native firms, local governments and employees relying on Red Dog dollars. The mine is running out of ore in its main pit and needs federal permission to begin excavating a second pit that could keep the mine going for another 20 years.

Red Dog has struggled with its water discharges ever since starting up two decades ago. The mine has routinely violated some criteria within its federal water pollution discharge permit, resulting in fines and lawsuits. The new permit would legalize the discharges that have been problematic.

Federal and state regulators say it's OK to relax the older permit because the mine's pollution discharges are not harmful and fish populations downstream of Red Dog have actually increased because the discharges contain a smaller percentage of harmful pollutants than the natural flow of water before the mine was built. The new permit would not increase the amount of pollution from the mine, they say.

But the groups appealing the U.S. Environmental Protection Agency permit contend that recent research shows the mine's discharges could harm spawning grayling. And, they say, it's illegal for the EPA to relax the mine's previous permit.

The EPA issued the revised permit last month. On Tuesday, lawyers filed a permit appeal on behalf of the Kivalina and Point Hope tribal councils, the Northern Alaska Environmental Center, Alaska Community Action on Toxics and five village residents. An EPA administrative appeals board in Washington, D.C., will take the appeal.

The mine operator, Vancouver, British Columbia-based Teck Resources, said it might have to suspend production in October if the appeal isn't resolved by May.

Once production stops, it would take 18 months to fully ramp up the mine again, said Karl Hanneman, Teck's director for corporate affairs in Alaska.

Vicki Clark, an attorney for some of the groups disputing the permit, said it isn't their intent to shut down the mine.

"The agencies took a long time (on the permit) and that has created a timing situation that none of us wanted," said Clark, with the Anchorage-based environmental law firm Trustees For Alaska.

She said that the villages are unhappy with the pollution discharges and would like to work with Teck on technical fixes that could allay their concerns.

At least nine organizations in the Northwest Arctic have passed resolutions in support of new permits to allow Red Dog's expansion, including the Northwest Arctic Borough and tribal governments in Noorvik, Kiana, Kotzebue and Deering.

NANA Regional Corp., which owns the land that Red Dog sits on, says it is disappointed by the appeal. Rosie Barr, NANA's resources manager, said the appeal is "a direct threat to the social, cultural, environmental and economic benefits our shareholders receive from the mine."

The mine employees roughly 300 NANA shareholders and is the major source of private tax dollars in the region.

The mine's revised water permit was scheduled to go into effect on March 1.

Even if the dispute over water discharges is resolved, the company still needs to obtain a wetlands permit from the Army Corps of Engineers before it can begin excavation in the new ore deposit.