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Site visit: Perpetua Resources’ Stibnite gold project in Idaho named preferred alternative – US Forest Service

Yellow Pine pit at the Stibnite Gold project in Idaho. Image: Amanda Stutt.

The road from Yellow Pine, a historical trade center with a population less than 50 within the Stibnite Mining District to Perpetua Resources’ Stibnite gold project, remains unchanged since the US government commissioned mining operations there to produce tungsten and antimony for the war effort in the 1940s.

A critical and strategic mineral, antimony is one of the reasons that the US government, and entities during World War 2 and the Korean War aligned at Perpetua’s current project location.

Mining continued throughout the end of the Korean War, in a manner prior to the onset of more stringent environmental regulations. Mined since the 1890’s, by the 1990s, the site was left a mess  – and 37 miles of upgrades are needed on the road. 

Known as Midas Gold until last year, Perpetua (Nasdaq, TSX: PPTA) moved its headquarters from Vancouver to Idaho, where it is restoring the historic brownfield site. 

The results of an independent feasibility study envision the project becoming one of the largest and highest-grade open-pit gold mines in the United States with over 4 million ounces of gold in reserve – and the country’s only primary producer of antimony. 

Blowout Creek at the Gold Stibnite project. Image: Amanda Stutt.

According to Perpetua’s January 2021 feasibility study, the project has total proven and probable mineral reserves of 104.6 million tonnes (Mt) grading 1.43 grams per tonne gold.

The mineral reserves include 14.2 Mt of high-antimony ore grading 0.42% antimony. The average annual metal production during the first four years of operation is expected to be approximately 463,000 troy ounces of gold and 18.4 million pounds of antimony per year.

This summer, Perpetua gained momentum on its legacy cleanup, bringing on IMCO Construction as a partner to begin water quality improvements in the Stibnite mining district. 

Water quality at the site was degraded by elevated levels of arsenic and antimony from millions of tonnes of unconstrained tailings and other mine waste left behind by previous operators over the last 100 years.

Perpetua has permission from the Environmental Protection Agency and the United States Department of Agriculture to conduct time critical early action cleanup activities.

The Yellow Pine pit is the crown jewel – and will be mined first.  Environmental remediation needed is where the east fork of the south fork of a salmon river flows into the abandoned mining pit, where Chinook salmon and Bull trout migrate up the river – meaning miles of critical habitat.

The project has been designed, in the first years of construction, to fix that source of sedimentation that is degrading habitat and water quality. 

Work onsite to fulfill obligations under the ASAOC clean up agreement with the EPA and USDA. Image: Amanda Stutt.

Onsite, work is underway to fulfill the company’s obligations under the ASAOC clean up agreement with the EPA and USDA.

Also included in the plan is to re-route the river into a re-designed fish passageway to ensure the adults can get up the river, and the juveniles can get down. 

The project will open 8-13 miles of river habitat.

The US Forest Service released in October the Supplemental Draft Environmental Impact Statement (SDEIS) for the project.

This a major milestone in the advancement of the project and provides clarity for the remainder of the National Environmental Policy Act (NEPA) process, the company said. 

This month, Perpetua’s modified mine plan was identified as the preferred alternative due to improvements in water quality and temperature and site access benefits. 

The US Forest Service identified Perpetua’s project as the preferred alternative because plan incorporates water management and closure activities to reduce the duration of long-term water treatment requirements, includes measures to manage stream temperatures, and reduces potential impacts associated with access, transportation and hazardous materials on alternative access routes to the project site.

It also concluded the preferred alternative would reasonably accomplish the purpose and need for consideration of approval of the Stibnite gold project, while giving consideration to environmental, economic and technical factors. Under NEPA, a “Preferred Alternative” is identified by a Federal agency in a DEIS to let the public know which action the agency is leaning toward selecting as final.

The Stibnite gold project has a 15-year reserve life with a payback period of less than 3 years and an internal rate of return over 20% at the base case assumption of $1,600 per ounce gold price.

Construction at the site, said CEO Laurel Sayer, is targeted to begin in 2024.

On November 17, Perpetua is holding an investor webinar to update on permitting progress and the SDEIS. Registration is here.