US-focused gold miner i-80 Gold said on Friday that it had received all required permits and that it had started construction at its Archimedes underground project on the Ruby Hill property in Nevada.

The approvals from the Nevada Division of Environmental Protection and the US Bureau of Land Management allowed the company to begin underground mining above the 5 100 ft elevation, consistent with previously approved openpit permits.

Development work would initially focus on surface infrastructure, with underground development to mid-2027 including two portals, the main haulage decline, ventilation raises, exploration bays and supporting facilities.

“The receipt of permits and commencement of construction at Archimedes marks a major milestone for i-80 Gold as we advance Phase 1 of our growth strategy in Nevada. Phase 1 is expected to increase annual gold output from less than 50 000 oz to a target range of 150 000 oz to 200 000 oz of gold by 2028,” said president and CEO Richard Young.

Young added that exploration upside at Archimedes could extend the current ten-year mine life, with infill drilling of both the upper and lower zones now being accelerated to support a feasibility study expected in the first quarter of 2027.

Archimedes is the company’s second planned underground mine, located 180 km from the wholly owned Lone Tree autoclave and carbon-in-leach processing facility. Material mined from the project is expected to be toll-treated at a third-party autoclave from late 2026, with processing transitioning to Lone Tree once that facility is commissioned in 2028.

According to the March 2025 preliminary economic assessment, Archimedes carries an after-tax net present value of $644-million at a 5% discount rate and an internal rate of return of 81%, based on a gold price of $3 000/oz. The study outlined average production of about 100 000 oz/y at an all-in sustaining cost of $1 877/oz, an initial capital requirement of $47-million and total life-of-mine costs of $106-million.

The deposit currently hosts 436 000 oz of gold in the indicated resource category grading 7.6 g/t and 988 000 oz in inferred resources grading 7.3 g/t. The lower Ruby Deeps zone remains open to the north and south.

The accelerated infill programme, expected to cost between $10-million and $25-million, will comprise more than 175 holes for 60 000 m of core. Work will feed into the feasibility study and updated resource model, which will also incorporate ongoing metallurgical testwork.

Archimedes is central to i-80 Gold’s three-phase plan to lift production in Nevada to 600 000 oz/y in the early 2030s. Phase 1 covers the ramp-up of Granite Creek underground, construction of Archimedes, and the refurbishment and commissioning of Lone Tree.