EPA critical of state air pollution permit for proposed Stibnite Gold Project

29th of Aug 2023

Construction and operation of the proposed Stibnite Gold Project under the terms set forth in an air pollution permit issued by the Idaho Department of Environmental Quality (IDEQ) would not comply with the federal Clean Air Act. That message was made clear in an August 10 letter from Casey Sixkiller, Regional Administrator for the Environmental Protection Agency (EPA), to IDEQ.

“The Agency’s interest is ensuring that the Stibnite Gold Project is properly permitted and complies with the Clean Air Act to ensure the protection of human health and the environment,” Sixkiller wrote.

Perpetua Resources (formerly Midas Gold) proposes a massive gold mine in the headwaters of the East Fork of the South Fork Salmon River adjacent to the Frank Church–River of No Return Wilderness Area. The area within and surrounding the proposed mine is part of the aboriginal homelands of the Nez Perce Tribe who have reserved the right to fish, hunt, gather, and pasture at traditional places in their 1855 Treaty with the United States.

The proposed mining activities would result in large quantities of dust or particulate matter being emitted into the air, which can cause serious health problems. The rocks, soils, and dust at Stibnite are also known to be very high in arsenic, a human carcinogen known to cause developmental effects, diabetes, pulmonary disease, and cardiovascular disease.

In its letter, EPA raise three primary concerns with the IDEQ air pollution permit:

  1. The permit’s emission limits are not adequate to limit the Stibnite Gold Project’s potential to emit below the Prevention of Significant Deterioration permitting threshold; thus, construction of the Stibnite Gold Project would constitute construction of a major stationary source without a Prevention of Significant Deterioration permit;
  2. The permit’s emission limits are not adequate to protect the particulate matter National Ambient Air Quality Standard; and
  3. IDEQ’s delineation between the Stibnite Gold Project boundary and the ambient air—where the National Ambient Air Quality Standards apply—is not adequately supported.

Advocates for the West is currently challenging the air pollution permit. We represent the Nez Perce Tribe and Idaho Conservation League in the appeal, which was filed together with Save the South Fork Salmon.

Read the EPA Letter