Vancouver-headquartered base metals miner Trevali has announced positive feasibility study results for an expansion of the Rosh Pinah zinc/lead mine, in Namibia, affirming robust project economics, while reducing carbon intensity and water consumption.

The Rosh Pinah Expansion 2.0 (RP2.0) increased the project capital expenditure by nearly 20% to $111-million, from $93-million in the prefeasibility study of a year earlier.

The payback period increased to 4.6 years, but CEO Ricus Grimbeek stated on Tuesday that the study reaffirmed the project’s robust economics. The feasibility study calculated an aftertax net present value, using an 8% discount, of $156-million, free cash flow of $290-million and an internal rate of return of 58%.

The feasibility study incorporates a 15-year power purchase agreement with Emesco for the supply of solar power of about 30% of the required power and the addition of a water treatment plant in conjunction with the paste fill plant, which would reduce the water intensity from 1.54 m³/t to 0.65 m³/t.

“The RP2.0 project will modernise and expand the 50-year-old mine, increasing throughput by 86%, enabling the operation to increase production at a significantly lower operating cost, all while working more safely and reducing our environmental footprint,” said Grimbeek.

The study contemplates increasing the mill throughput from 0.7-million tonnes a year to 1.3-million tonnes a year.

Rosh Pinah will produce 135-million pounds a year of zinc at an average all-in sustaining cost of $0.67/lb. Yearly lead and silver production will total 23.7-million pounds and 303 000 oz, respectively.

Assuming a positive investment decision, detailed engineering and procurement of long-lead items would start in the fourth quarter and construction would start in mid-2022. Commercial production is expected by about mid-year 2024.