Kilgore gold exploration project area

If they’re approved, Excellon's gold exploration plans would add 10 miles of temporary roads and for drilling 130 holes. Additionally, 3 more drillholes would be bored to about 1,300 feet deep to examine core material.

A Centennial Mountains gold exploration proposal that had been halted due to uncertainty about impacts to an imperiled native trout population is reemerging before the Caribou-Targhee National Forest.

A proposal the forest is considering is largely the same as one that was slowed by U.S. District Court Judge Lynn Winmill in late 2019, although the former proponent, Otis Gold Corporation, has since been bought up by Toronto-based Excellon Resources.

The plans would give Excellon 3 to 5 years to drill and explore for gold on 22 scattered acres within a 19-square-mile zone about 6 miles north of Kilgore, Idaho, which is 60 miles north of Idaho Falls.

After the court ruling, the Caribou-Targhee could have completed a supplement to its earlier analysis — an environmental assessment — to address Winmill’s concerns about impacts to a small population of Yellowstone cutthroat trout, which have been nearly extirpated from the Henry’s Fork headwaters.

“But because things change and it would be a couple of years before we got the new proposal, we went ahead and did a completely new EA,” Caribou-Targhee geologist and project leader Diane Wheeler told the Jackson Hole Daily.

That environmental assessment, a draft, is now open to public comment, though the deadline for submissions is today, Feb. 11.

Confusingly, much of the new science explaining how Excellon’s exploration plans will or won’t affect cutthroat trout in the watershed is not included in the new draft assessment. It’s being withheld for now, Wheeler explained, in anticipation of pending public comments that could change the analysis, and also because of a federal mandate that agencies shorten National Environmental Policy Act analyses.

“All the resources are analyzed, but the specialist reports will not get finalized until the final EA is out,” Wheeler said. “And the reason for that is because we don’t want anybody running around with these draft reports when they may change after we get scoping done.”

However, the environmental advocacy groups whose litigation slowed the Kilgore gold exploration in the first place have acquired the specialist reports through the Freedom of Information Act.

“The data is pretty light,” said Kathy Rinaldi, Idaho conservation coordinator at the Greater Yellowstone Coalition.

The Greater Yellowstone Coalition and Idaho Conservation League also challenged the Caribou-Targhee on concerns over grizzly bear migration, whitebark pine and Columbia spotted frogs, but Winmill ruled in the forest’s favor on those issues.

The primary on-the-ground change Excellon is proposing to address the court’s cutthroat trout concerns is to draw water from off the national forest and out of Beaver Creek, instead of out of Corral Creek, which has retained some of the only cutthroat remaining in the region. The diversion, typically, would be 18 gallons per minute and about 5 acre-feet per year.

“We simply just don’t know the impacts,” Rinaldi said, “so they’re just trying to stay away from it.”

Kilgore exploration project manager Phil Bandy’s take is that updated plans are responsive to the court’s concerns. The EA includes a number of “design features” intended to limit impacts, such as requiring that a Forest Service hydrologist or fisheries biologist examine wherever water is drafted from.

“We’re confident that it addresses all the concerns that were stated by Judge Winmill,” Bandy said, “and that it will be approved and we can move forward.”

If they’re approved, the exploration plans would add 10 miles of temporary roads and allow Excellon to drill 130 holes. Additionally, 3 more drillholes would be bored to about 1,300 feet deep to examine core material. Operations would run 24 hours a day, spanning July 15 to Dec. 15.

Previously, Otis Gold Corp. estimated that the Kilgore Project area contains 825,000 ounces of gold — $1.52 billion worth, at least at the current spot price. What the exploration determines will dictate how Excellon would go about accessing that gold, either via a surface or underground mine.

If that mine proposal were to come out years down the road, the Caribou-Targhee would be tasked with completing a more-intensive environmental impact statement.

Contact Mike Koshmrl at 732-7067 or

Mike has reported on the Greater Yellowstone Ecosystem's wildlife, wildlands and the agencies that manage them since 2012. A native Minnesotan, he arrived in the West to study environmental journalism at the University of Colorado.

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