In the same week that some anglers received coveted lottery permits to float Montana’s iconic Smith River—a bucket list experience for many trout anglers—environmental groups filed a lawsuit to prevent mining exploration near its headwaters.

Outfitters and sportsmen’s groups have expressed concern since January 2014, when the Montana Department of Environmental Quality (DEQ) approved a permit for Canadian mining company Tintina Alaska Exploration Inc. to sample for copper by excavating on the banks of Sheep Creek, the most important trout spawning tributary and a major source of water to the Smith during low summer flows. “If a mine dewaters the Smith, it will be a big deal for recreationists and agriculture,” said Mark Aagenes, Montana Trout Unlimited Conservation Director and a former Smith River fishing guide.

The Great Falls Tribune reports that a lawsuit was filed on March 14 by the Montana Environmental Information Center and Earthworks against the DEQ and Tintina. According to the article, the lawsuit alleges “the final analysis presented by DEQ did not adequately assess the full range of environmental impacts associated with the proposed exploration activities, including impacts to water quality, stream flows, and fisheries.”

The Black Butte Mine Project permit would allow for an exploration tunnel under public and private lands that would run a mile deep and 36 feet in diameter, to sample approximately 10,000 tons of rock. According to the Helena Independent Record, Tintina has drilled hundreds of core samples showing “that the Black Butte Copper mine is the third highest grade copper deposit in development in North America.” A Montana Environmental Information Center study has also shown “that the rock in which the copper is intertwined has high sulfide levels,” which could lead to acid mine runoff.

TU’s Aagenes says that water rights holders should be concerned. “We’ve heard the line before: ‘This mine will be different.’ In some places it may be fine to gamble, but not on the Smith.”

Sarah Grigg has worked in many wildlife-related roles within the Greater Yellowstone ecosystem, from grizzly bear researcher with Idaho Fish & Game to ranch manager for The Nature Conservancy. Her writing has appeared in The Drake, TROUT, and Red Flag Magazine.