(Isaac Babcock/AP) - A large-scale mining operation in Alaska’s Bristol Bay watershed is now a major political issue. (Isaac Babcock/AP) - A large-scale mining operation in Alaska’s Bristol Bay watershed is now a major political issue.

In a sign of the growing political importance of the fight over whether to permit Alaska's Pebble Mine, Environmental Protection Agency administrator Gina McCarthy said in an interview she may make a personal visit to see where the controversial project would operate.

Six tribes have joined forces with environmentalists and fishing operators have been lobbying the Obama administration to block to proposed mining operation in the Bristol Bay watershed, a remote area that is home to nearly half of the world’s sockeye salmon. The tribes have asked the EPA to invoke its powers under the Clean Water Act to block the mine on the grounds that it would harm the region’s waterways, fish and wildlife, while two companies building the mine, Anglo American and Northern Dynasty, have launched their own campaign aimed at keep the agency out of the decision.

"Any act that EPA would take would be carefully considered," McCarthy said. "There are significant natural resources in that area, along with significant economic resources. We’ve got to get that balance right."

Both sides have enlisted the help of advocacy groups and consultants to make their case in Washington. Mine opponents, which include environmental groups such as Trout Unlimited, have hired former Obama aides Tommy Vietor, Jon Favreau and Paul Tewes to orchestrate a pubic relations campaign, while the mining companies have hired the Livingston Group and gotten support from the Competitive Enterprise Institute.