It's probably the biggest fight in recent history between environmentalists and the natural-resources industry. And if you've ever eaten salmon, you might have a stake in the outcome.

June 30 marked the deadline for filing public comments with the Environmental Protection Agency on the development of a project known as Pebble Mine in southwest Alaska's Bristol Bay region. As of last week, more than 500,000 comments had been recorded.

On one side of the fight is the largest undeveloped copper deposit (along with plenty of gold and molybdenum) in the world. Estimates vary on how valuable the minerals are, but they might be worth as much as $300 billion. A group of companies lead by London-based Anglo American Plc wants to develop the mine over the next several decades. It undoubtedly would be an economic boon to an area with a dearth of good jobs and yield billions of dollars over the mine's lifespan in taxes for Alaska's treasury.

On the other side is the most productive salmon fishery in the world and a region that, with about 7,500 residents, is one of the most pristine in the world. The commercial and recreational fishery generates as much as $500 million a year for the state economy and provides subsistence living for many of the tribal members in the area.

The mining group, which describes the EPA's evaluations of the project as flawed and biased, says it can develop the mine and leave the salmon fishery intact. Opponents say this isn't plausible even under the best circumstances, meaning no industrial accidents.

Because the ore is of relatively low grade, huge amounts of material would have to be extracted. Developing the mine, which would encompass an area two-thirds the size of Manhattan, would obliterate dozens of miles of salmon-spawning streams and rivers that overlay the deposit and flow into Bristol Bay, where millions of salmon gather and are harvested every year. Billions of tons of waste material, mostly minerals that produce sulfuric acid and other toxins upon contact with air and water, would be stored in gigantic lakes filling two valleys behind man-made dams, some of them 700-feet high and several miles long. Copper, which would be dissolved by the acid, is among the most lethal substances for salmon. Even microscopic amounts are believed to disrupt the ability of a salmon to return to its natal stream to reproduce.

The EPA says the mine waste probably would have to sit there for decades or centuries, possibly "in perpetuity." This poses any number of problems. For one, the EPA has concluded that mining is the most-polluting industry there is. And it may not be realistic to think the mining group will spend the money needed to maintain the waste impoundments once the mine closes.

Then there are earthquakes: The project is in an active seismic zone about 125 miles from the fault that caused a quake in 1964 that was the second-largest ever recorded. Opponents say another quake of that scale and subsequent dam collapse might make the catastrophic Exxon Valdez crude oil spill in Prince William Sound look benign.

Lining up in favor of the mine is most of Alaska's political leadership, not to mention industry groups that include backers such as the conservative Koch family. (One notable exception was deceased Republican Senator Ted Stevens, an ardent advocate of resource extraction in Alaska.)

In most polls, residents of Bristol Bay and the rest of the state oppose the project -- as do the fishing industry and environmental groups. Most of the world's big jewelry chains have pledged not to sell gold from the mine.

Legislative efforts to stop the mine have stalled and tend to get bogged down in debates about the constitutional issue of "taking" property without appropriate compensation.

And so it all comes down to what the EPA decides in a final report to be issued later this year after sifting through all those the public comments. By invoking the federal Clean Water Act, the agency probably has the tools to stop the mine and possibly withstand the inevitable legal challenge.

But should it? It might depend on which you think is more valuable -- salmon or copper.

(James Greiff is a member of Bloomberg View's editorial board. Follow him on Twitter.)