The U.S. Environmental Protection Agency has signed off on a key scientific report that says a potential giant Alaskan copper and gold mine poses serious environmental and ecological threats. Environmentalists hailed the EPA document while industry blasted it.

Players in the long, fierce debate saw the report, released Wednesday, as a key milestone.

The report comes before the potential filing of permits in 2014 by Northern Dynasty Minerals Ltd. (TSX:NDM), the sole project developer after partner Anglo American PLC (LON:AAL) abandoned Pebble late last year.

Half of the world’s sockeye salmon is at stake, alongside thousands of jobs and billions in profitable mining deposits.

Here are brief key sections from the report and its executive summary, along with reactions from supporters and critics of the mine. The report focuses on the Nushagak and Kvichak River water systems, two subsystems within Alaska’s larger Bristol Bay region, inhabited by 31 native Alaskan tribes.

From the Report

Up to 94 miles of salmon streams and 5,350 acres of wetlands, ponds, and lakes would be destroyed, by EPA estimates, thanks to the mine footprint. Up to 33 more miles of salmon streams would experience changes to ecosystem structure, too.

“Under routine operations, EPA estimates adverse direct and indirect effects on fish in 13 to 51 miles of streams,” reads the executive summary, citing normal wastewater treatment activities. That doesn’t account for accidents or failures of culverts, pipelines or dams, which could have “catastrophic” consequences.

The EPA also emphasized public participation. The agency received 890,000 comments on the second draft in 2013, and held public meetings in Alaska and Seattle that were attended by about 2,000 people. Public awareness and opinion about the mine is strong.

“Alaska Native tribes in the watershed … have maintained a salmon-based culture and subsistence-based way of life for at least 4,000 years,” reads the report. “The predominant Alaska Native cultures present in the Nushagak and Kvichak River watersheds … are two of the last intact, sustainable, salmon-based cultures in the world. In contrast, other Pacific Northwest salmon-based cultures are severely threatened by development, degraded natural resources, and declining salmon resources.”

Still, the report points out that sentiment among Alaskan natives is divided and highlights the relatively sparse population in the area. Within the two most impacted watersheds, there were only 4,337 people in 2010. A few Alaskan native villages are “seriously considering” the opportunities offered up by large-scale mining, according to the report.

As for the post-mining phase: “Because mine wastes would be persistent, this period could continue for centuries and potentially in perpetuity.”

In fairness to the developers: “The assessment also does not include a cost-benefit analysis and does not compare mining to other ongoing commercial activities such as commercial fishing.”

Nonetheless, the report adds: “The Bristol Bay watershed’s ecological resources generated nearly $480 million in direct economic expenditures and sales in 2009 and provided employment for over 14,000 full and part-time workers.”

In comparison, the Pebble deposit could generate revenue of $300 billion to $500 billion over the mine’s life, alongside 2,000 temporary construction jobs and 1,000 mining jobs. That’s far lower than estimates from a developer-funded study, which concluded that the mine could support more than 16,000 jobs.

In all events, though, the EPA emphasizes that the scientific assessment, though it seems bearish on the project, doesn't reflect a regulatory or policy position.

But it’s hard to believe that the report isn’t a strong voice against the mine, given that the assessment is deemed a “conservative estimate” and already details considerable risks. EPA chief Gina McCarthy has shown more interest in the Pebble controversy than her predecessor, some say, and major developments are expected to occur under her watch.

Reactions

Anchorage attorney Geoff Parker, who has opposed the mine on behalf of Alaskan tribes, told IBTimes that a revised Appendix J in the report indicates that the EPA may move toward a veto of the project under the Section 404C Clean Water Act.

That appendix “is on compensatory mitigation of unavoidable impacts, and unavoidable impacts are an excellent basis for using 404C,” he told IBTimes. “It’s the only part of the assessment that I’ve spotted that almost doubled in length. Everything else remained really similar.”

John Shively, who leads the corporate Pebble Partnership backing the mine, though, criticized the scientific review as rushed, resulting in flawed studies.

“The EPA has studied much smaller areas than Bristol Bay and taken considerably longer and committed considerably more resources to complete them,” he wrote in a statement Thursday. He added that the partnership has already spent several years and $600 million on its own studies, which could involve greater mitigation than the EPA projects.

“It is both a poorly conceived and poorly executed study, and it cannot serve as the scientific basis for any decisions concerning Pebble,” he said. “This report should not be used as the basis for any type of agency decision regarding Pebble.”

Notably, the review took over three years, collected over a million public comments, and involved multiple public hearings. The EPA also defended its use of “rigorous and independent expert peer review.”

Mine developer Northern Dynasty added that it expected a separate permitting process, handled by the U.S. Army Corps of Engineers, would provide a more rigorous and fair scientific review of the project. It called the third and final draft of the report a “flawed analysis,” much like the previous two drafts.

Mining industry nonprofit American Resources Policy Network also told IBTimes that the regulatory decisions shouldn’t be based on the EPA report, since this violates the due process built into the National Environmental Policy Act (NEPA).

But environmental activists and Bristol Bay’s fishermen seem happy with the report.

“Like Bristol Bay’s salmon tributaries, the science is now crystal clear: Pebble Mine cannot coexist with our amazing fishery,” wrote Commercial Fishermen for Bristol Bay representative Brett Veerhusen in an email to IBTimes. “The Obama Administration and EPA must use its authority under the Clean Water Act so salmon aren’t traded for gold and copper.”

The Natural Resources Defense Council also called the report a “scientific indictment.”

“The watershed assessment is objective, clear and grounded in sound science. It was conducted over several years and confirms what the residents of the region have long understood: that large scale mining in this place would pose an unacceptable risk,” wrote NRDC attorney Joel Reynolds in a statement. “The time for study is over. It’s now up to EPA to take regulatory action to stop the Pebble Mine.”