The Environmental Protection Agency is warning that plans for a massive mine in the hills above Bristol Bay in Alaska — home of the biggest sockeye salmon fishery in the world — could have devastating consequences for rivers and streams and wipe out habitat for fish.

A study that represents the federal government’s first significant scientific assessment of the proposed Pebble mine site concludes that extracting billions of pounds of gold, copper and molybdenum from the region could result in the direct loss of up to 87 miles of streams and nearly seven square miles of wetlands.

“We conclude that, at a minimum, mining at this scale would cause the loss of spawning and rearing habitat for multiple species of anadromous and resident fish,” according to the EPA watershed assessment released Friday. And that’s even without the failure of one of the massive tailings dams the agency said could be as high as the Washington Monument.