Permit invalid for proposed Stibnite Gold Mine over arsenic air pollution concerns

The Idaho Board of Environmental Quality issued a decision invalidating Perpetua Resources’ air pollution permit for the proposed Stibnite Gold Mine in Valley County. Blasting and hauling operations at the proposed mine would emit massive amounts of arsenic-laden dust. The Board found that the Department of Environmental Quality (DEQ) failed to follow Idaho air pollution rules designed to protect people from exposure to toxic and carcinogenic pollutants when it issued a permit to Perpetua.

In the May 9 written decision, the Board faulted DEQ for employing each of three unreasonable methods to mask the full risk of arsenic exposure caused by the proposed Stibnite Gold Mine. The Board ruled in favor of DEQ and Perpetua on other issues.

“Arsenic is a toxic pollutant and a carcinogen,” said Bryan Hurlbutt, Staff Attorney at Advocates for the West. “The Board’s decision sends a strong message. Perpetua cannot bend the rules and disregard the risks from its proposed mine.”

In reaction, Will Tiedemann, a regulatory conservation associate with the Idaho Conservation League, explained, “DEQ incorrectly viewed the mine’s carcinogenic effects of arsenic from a long-term perspective only. Instead, Idaho’s rules require the public to be protected from arsenic on a year by year basis. DEQ’s flawed arsenic emissions analysis is kind of like taking the amount of arsenic a facility could emit each year over 70 years and then allowing that same amount to be emitted in just 16 years.”

The Board decision remands Perpetua’s air pollution permit, sending it back to an administrative hearing officer to reconsider arsenic emission and cancer risks from the proposed mine. Any party can seek reconsideration before the Board or challenge the Board’s decision in state court.

Background

The Idaho Conservation League and the Nez Perce Tribe, represented by Advocates for the West, together with Save the South Fork Salmon, appealed the permit in 2022 after DEQ dismissed repeated concerns during the permitting process.

The Board of Environmental Quality first announced the decision at a May 1 meeting. Speaking on behalf of the Board, member Dr. J. Randy MacMillan stated, “DEQ created a misleading risk analysis that greatly underestimates the actual cancer risk.”

DEQ was the first agency to issue any permit of note for the Stibnite Gold Mine. Perpetua is still seeking approvals from the Forest Service and other state and federal agencies. The proposed mine would consist of three open-pits, a massive waste rock dump site, and an extensive network of roads and other infrastructure in the remote headwaters of the East Fork of the South Fork of the Salmon River.