About 200 miles southwest of Anchorage, Alaska’s largest city, lies 40,000 square miles of wild tundra and wetlands. Crisscrossed by rivers and dotted with lakes, the upper Bristol Bay watershed is reachable only by plane, and as a consequence, it remains virtually pristine. Its many waterways support subsistence hunters, fishing tourism, and a diverse array of wildlife. Along with grizzly bears and bald eagles, the area boasts the world’s most productive salmon run, where an incredible 30 million to 50 million fish return every summer to spawn. With its $1.5 billion sustainable commercial fishery, Bristol Bay supplies half of all sockeye salmon on the global market.

Sounds like the wrong kind of place for a highly polluting mine, right? But foreign companies have been eyeing the gold and copper deposits under Bristol Bay’s watershed and scheming to build a massive mine there for more than a decade. NRDC and a broad coalition of Alaska natives, sportsmen, conservationists, jewelers, and other concerned citizens have been fighting to keep Bristol Bay wild and productive—and they’ve been winning.

Exploratory drilling at Pebble Mine first came about in 2002, when Northern Dynasty Minerals, a small Canadian company, proposed the project on 186 square miles of Alaska state land for which it held the mineral rights. Lacking mining experience of its own, Northern Dynasty sought help. So three of the world’s largest companies—Anglo American, Mitsubishi, and Rio Tinto—quickly jumped on board, all eager for a piece of the estimated $350 billion worth of precious metals beneath the landscape. Joining forces as the Pebble Limited Partnership, the four companies started planning what could be, at two miles wide and 2,000 feet deep, the largest open-pit mine in North America.

Why so big? Due to the region’s remote location and the low-grade quality of its minerals, making a buck wasn’t going to come easy. To extract just one pound of ore, the miners would have to sift through 99 pounds of rock. Pebble Mine would be worth the investment only if it were made as big as possible, turning a terrible idea into something even worse.

The chemicals used to separate the gold and copper deposits from the rest of the rock would create an unimaginable amount of toxic waste. Earthen dams as tall as 740 feet would be required to contain about 10 billion tons of mine tailings and keep it from the surrounding environment—in perpetuity. It’s no secret that dams leak, especially in wet and earthquake-prone regions like Bristol Bay. According to the U.S. Environmental Protection Agency, the mine would have the potential to destroy 94 miles of streams and 5,350 acres of wetlands, ponds, and lakes. It would also remove an extra 35 billion gallons of water from salmon habitat every year.

And that’s only the mine itself. The necessary infrastructure—roads, a major power plant, and a new deep-water port (adjacent to Cook Inlet, where belugas are currently fighting for survival) would also take their toll, bringing noise, water, and air pollution to the extended region and laying a solid foundation for other mining companies to move right in and set up shop. There are no two ways about it: Pebble Mine would destroy Bristol Bay’s wild salmon fishery and devastate the livelihoods of the people and communities that depend on it.

“It’s just the worst place in the world to build a mine like this,” says Taryn Kiekow Heimer, a senior policy analyst for NRDC’s Marine Mammal Protection project. “When you tell people about the resources, the salmon, the incredibly rich indigenous culture that relies on the fish up there—it’s not just an environmental battle; it’s a human rights battle.”

Although local and statewide opposition to Pebble Mine is strong—more than 80 percent and 62 percent, respectively—the state of Alaska, renowned for its pro-development perspective, has thrown its support behind the $6 billion project. That fact, however, has hardly daunted the coalition of native Alaskan tribes, commercial and sport fishermen, environmental groups (including NRDC and its members), and others who are fighting a relentless—and wildly successful—campaign to persuade the Pebble Partnership to abandon its plans for Bristol Bay. After facing years of coalition advocacy—including petitioning, attending shareholder meetings, and advertising in major publications like the New York Times and The London Financial Times—Pebble’s three major investors fled the project. Mitsubishi bowed out in 2011, Anglo American left in 2013, and Rio Tinto divested in 2014, donating all its shares in Northern Dynasty Minerals to two Alaskan charitable foundations.

While the coalition went after the money behind Pebble Mine, it also targeted the permitting process for the project, calling on the EPA to use its authority under the Clean Water Act to protect Bristol Bay. (Section 404(c) of the act allows the EPA to prohibit, restrict, or deny permits if a project would have an “unacceptable adverse impact” on the environment.) That strategy worked, too. The agency went above and beyond the call of the petition, undertaking a four-year scientific study that was peer-reviewed twice and revised three times in response to public comments. As the coalition expected, the agency found that “the infrastructure necessary to mine the Pebble deposit jeopardizes the long‐term health and sustainability of the Bristol Bay ecosystem” in its July 2014 “proposed determination” under Section 404(c).

“The uniqueness of the watershed, the need for pristine water to support salmon, and the potential [development] of North America’s largest open-pit mine warrants a closer look,” said EPA Administrator Gina McCarthy at the time. Northern Dynasty Minerals, now the sole member of the once formidable Pebble Limited Partnership, responded aggressively by filing three lawsuits, one of which has put the EPA’s review on temporary hold. So after a decade of reckless plans to rip apart Bristol Bay’s ecosystem, the Pebble Mine project is hanging on by a thread. But the coalition remains vigilant.

“People mistakenly believe that with all the great successes we’ve had in this campaign, the project is dead—and it’s not,” Heimer says. “We keep putting nails in the coffin, but not quite enough to kill the zombie inside.” Stay tuned.