Name of the Project
Castle Mountain Phase 2 expansion.

Location
San Bernardino County, California, in the US.

Project Owner/s
Equinox Gold.

Project Description
Castle Mountain achieved Phase 1 commercial production in November 2020, with expected production of 30 000 oz/y to 40 000 oz/y of gold.

The current operation comprises a run-of-mine (RoM) heap-leach facility placing 12 700 t/d of ore on the leach pad.

Phase 2 is expected to extend the total mine life to more than 20 years.

The March 2021 feasibility study envisages a conventional off-road truck-and-shovel openpit mining operation. The proposed project includes the expansion of RoM heap leaching and the mill­ing of higher-grade ore, increasing production to an average of 218 000 oz/y for 14 years fol­lowed by leach-pad rinsing to recover residual gold.

The expansion will include a 45 350t/d RoM heap-leach facility and a new 3 200 t/d milling and leach/carbon-in-leach (CIL) plant for higher-grade ore. The existing openpits will ultimately amalgamate to become the Main pit that, with the South Domes pit, will provide Phase 2 ore.

The mine plan outlines nine phases of openpit mining from five pit areas – JSLA (three phases), Jumbo, Oro Belle, East Ridge (two phases) and South Domes (two phases) – starting with JSLA backfill and advancing north, and then to South Domes to complete the operation. The mining sequence of the phases allows for the backfilling of waste as the pit reaches final limits.

The Phase 2 mine production schedule will deliver 213.4-million tonnes of ore grading 0.41 g/t gold to the RoM heap leach and 16.1-million tonnes of ore grading 2.3 g/t gold to the mill.

Waste tonnage totalling 581.7-million tonnes will be placed in the waste rock dumps.

The Phase 2 heap-leach facility will comprise an enlarged heap-leach pad, an additional event pond, additional larger solution handling pumps and an additional carbon-in-column plant.

The new mill facility will comprise a two-stage crushing facility, conveyors, ball mill circuit, gravity concentration, leach and CIL tanks, thickeners, filters and a reagent handling area. Loaded carbon will be processed in a desorp­tion, electrowinning and refinery plant.

Additional infrastructure for Phase 2 includes water supply wells, pumps and distribution systems, installation of an electrical transmission line along a previous corridor, an electrical substation, a filtered tailings storage facility, an extension of two waste-rock dumps, a truck shop, and various site improvements and upgrades to meet the expanded project needs.

Potential Job Creation
Phase 2 is expected to provide more than 400 jobs during construction and operations.

Net Present Value/Internal Rate of Return
The Phase 2 project has an after-tax net present value, at a 5% discount rate, of $640-million and an internal rate of return of 18%.

Capital Expenditure
Total initial capital costs are estimated at $389-million, excluding $121-million for a leased mining fleet, or a total of $510-million if the fleet is bought upfront.

Planned Start/End Date
Not stated.

Latest Developments
None stated.

Key Contracts, Suppliers and Consultants
None stated.

Contact Details for Project Information
Equinox Gold, tel +1604558 0560 or email info@equinoxgold.com.