An Environmental Protection Agency study concluded that a proposed mine in southwest Alaska that has generated lobbying and congressional hearings over the agency's review process would hurt native tribes in the area as well as salmon stocks.

At issue is whether the EPA has the legal authority to deny developers of the Pebble Mine, a proposed copper and gold mine in Bristol Bay, Alaska, a key Clean Water Act permit even though no formal application is on file.

The EPA, with Pebble opponents such as commercial fishermen, native tribes and environmental organizations, says it has all the information it needs to conduct an assessment. The agency said it used mining scenarios devised by a contractor for developer Northern Dynasty.

The final environmental analysis for the mine will be used to inform a potential regulatory decision on whether to allow the mine to go forward -- though the EPA hasn't decided what it will do, said Dennis McLerran, the EPA regional administrator.

"We have made no decisions with respect to what comes next, or what authorities we might use going forward, or whether we will use any of those authorities any time soon," he said during a Wednesday media call.

The EPA said the mine's footprint would destroy between 24 and 94 miles of streams and two to eight square miles of wetlands that are vital habitats for Bristol Bay's sockeye salmon, which account for 46 percent of the global population. That would harm an ecosystem that generated $480 million in 2009, largely from commercial fishing.

The EPA also said the mine would disrupt native tribes, who requested the analysis and who have lived on a salmon-based subsistence way of life for 4,000 years.

Environmental groups cheered the decision and urged the EPA to deny a necessary Clean Water Act permit to build the mine.

“The study confirms the sentiment of local fishermen and communities who have long said that even under the best case scenario, Pebble Mine would destroy miles of irreplaceable salmon and wildlife habitat," the World Wildlife Fund said.

But industry organizations and some Republicans say ruling on the Clean Water Act permit would amount to a "pre-emptive" veto of the permit, as developer Northern Dynasty, operating under the Pebble Limited Partnership, hasn't formally filed an application.

They contend that the EPA is reviewing the mine based on hypothetical scenarios, warning that a ruling on the permit would cool investment along waterways while also inviting legal questions.

“EPA is setting a dangerous precedent by justifying its political prejudices on a flawed assessment based on hypotheticals,” said Sen. David Vitter, R-La., the top Republican on the Environment and Public Works Committee. “This is a very scary signal that the EPA is sending to businesses – that they are capable of and willing to kill a project before an application is even submitted.”

Republicans and the industry say the Pebble project could be a significant economic boon — an IHS study commissioned by Pebble LP said the mine would support roughly 16,000 jobs across the U.S. and add about $1.6 billion to gross domestic product annually during its five-year construction phase.

When asked whether the EPA analysis amounted to a closed-for-business sign, McLerran responded, "No, that is not what we're saying."

But John Shively, chief executive of Pebble LP, said, "The hypothetical mines developed by EPA in their first two drafts did not employ the most advanced engineering and mining practices, as will most certainly be used at Pebble."

To the point of potential coexistence between the mine and Bristol Bay's wildlife, McLerran said, "I think that the assessment speaks for itself."