Copper Mountain Mining Corporation has announced a new life of mine plan, which includes a proposed mill expansion to 65,000 t per day, for its 75%-owned Copper Mountain mine, located in southern British Columbia. The new life of mine plan increases Copper Mountain’s after-tax NPV by over 60% to $1 billion, on higher annual production and lower costs, when compared to the previously published 2019 Technical Report. The ’65ktpd Expansion’ builds upon the 45,000 t/d mill expansion currently underway.

“The 65ktpd Expansion, which moves the Copper Mountain mine to about a billion dollars of asset value, clearly underscores the mine’s quality, and our team’s ability to potentially grow reserves and value further,” stated Gil Clausen, Copper Mountain’s President and CEO. “This mill expansion study builds upon the growth projects that are already underway and illustrates the immense potential that the Copper Mountain Mine provides. In two years, we have more than doubled the mine life, grown the mine’s productive capacity, increased net asset value and significantly decreased cash costs. Following the completion of this 2020 Technical Report, we will further refine the capital estimates of this project in preparation for a development decision.”

Clausen added, “All of the deposits at the Copper Mountain Mine remain open and have significant exploration potential to add to our reserve and resource. We are steadily working to unlock the unrealised value and low risk growth potential at the Copper Mountain mine and we expect to fund this production growth with the mine’s internal cash flow.”

The Copper Mountain mill flowsheet is currently a conventional two-stage crushing, SAG, pebble crusher, ball milling, and sulphide flotation circuit design. The current capacity supports 40,000 t per day of ore processing.  The 45ktpd Expansion that is currently underway will add a third ball mill in parallel with the two existing ball mills.  The 65ktpd Expansion Plan includes the installation of a High Pressure Grinding Roll (HPGR) circuit utilising a Metso Outotec HRC3000, the addition of a fourth ball mill, a regrind Metso Outotec Vertimill, additional rougher and cleaner flotation circuit capacity, and electrical system upgrades. The existing SAG mill will be retired. The fourth ball mill, a 22 ft by 38 ft mill, will be installed adjacent to the third ball mill within the existing building. With the addition of the fourth ball mill, the ball milling line will comprise four mills operating in parallel. Two identical 24 ft x 30 ft mills, and two identical 22 ft x 38 ft mills. This work will allow for increased throughput and a grind size P80 of 165 µm.  The 65ktpd Expansion Technical Report assumes construction to be completed at the end of 2023 for commissioning in the beginning of 2024.

The existing MKII 60–89 primary crusher is fitted with a 600 kW motor and operates at 2,200 t/oph. The primary crusher is planned to be upgraded from the MKII to MKIII format ahead of the 65ktpd project. This will allow for a 1,000 kW motor, supporting the new duty point of 3,385 t/oph.

The 65ktpd Expansion is a planned plant-wide improvement that increases throughput in addition to:

• Reducing operating costs using newer but proven technologies and equipment;
• Reducing energy consumption through more efficient grinding unit operations;
• Improving flotation performance with substantially more capacity at the rougher and cleaner stages; and
• De-bottleneck concentrate dewatering, allowing for more flexibility at high tonnage during high head grade periods.

The 65ktpd Expansion will not require any additional mining fleet, as the existing fleet already produces sufficient ore supply to feed the concentrator at the planned milling rates.

A new building erected at the northeast corner of the existing concentrator will house a second rougher flotation circuit comprising a single bank of five 300 m3 Metso Outotec TankCells. The additional flotation capacity will allow for 26 minutes of residence time. The demolished existing regrind mill will be replaced by a more efficient Metso Outotec Vertimill VTM4500 stirred mill. This will also be in the new building along with new tank cells. Rougher concentrate from all rougher flotation lines will report by gravity to this circuit, where it will be reduced to a P80 of 25 μm.

The existing cleaner circuit will be expanded at the first cleaner and cleaner scavenger stage. A bank of four Woodgrove Technologies DFR cells will be installed as first cleaners in parallel with the two existing 3.7 m x 12.0 m flotation columns. Concentrate from the first cleaner stage will report to the existing DFR second cleaner bank of three cells (newly installed in 2020). The target final concentrate grade will be 28%. Tails from the first cleaner stage will report to the existing bank of five 70 m3 mechanical tank cells, and a new bank of six DFR cells operating in parallel. Concentrate from all cells at the cleaner-scavenger stage will report by gravity to the regrind circuit. DFR cells were selected in these cases due to their ability to minimise footprint, and the demonstrated unit recoveries achieved with the 2020 installation.

The mine life is estimated to be 21 years, including three years of processing stockpiled ore. The production plan is based on Mineral Reserves only and does not include any other Mineral Resource categories. The company believes that the potential exists to increase life of mine production further by converting Resources to Reserves as well as increasing resources through further exploration.

Total ore mined is expected to be 400 Mt and total waste mined is expected to be 671 Mt, with a strip ratio of 1.68. Using average recoveries of 85.4% for copper, 66.1% for gold and 66.2% for silver, total production is expected to be 2 billion pounds of copper, 978,000 oz of gold and 6.7 Moz of silver.

The initial capital cost required to increase throughput to 65,000 t/d is estimated to be approximately $123 million, plus a $25 million contingency for a total of $148 million. This includes the installation of the HPGR circuit, fourth ball mill, regrind circuit, verti-mill, additional rougher and cleaner flotation circuits and electrical system upgrades.

Total life of mine expansionary capital, including the capital for the 45,000 t/d mill expansion planned for 2021 and the integration of New Ingerbelle, is estimated to be $204 million. Total sustaining capital for the life of mine is estimated to be $255 million. The majority of sustaining capital is related to the replacement of mobile mining equipment.

Total LOM operating unit costs are estimated to be $7.60 per tonne milled, which includes mining cost per tonne milled of $3.70, milling cost per tonne milled of $3.63 and G&A per tonne milled of $0.26.  Mining cost per tonne mined is estimated to be $1.55.  Unit milling costs are estimated to be 25% lower for the 65ktpd Expansion compared to the current 45,0000 t/d mill expansion as a result of a higher milling rate and lower operating cost of the HPGR circuit, as compared to the existing SAG mill. The above costs result in an average C1 cash cost per pound of copper of $1.19 for the first ten years and $1.21 over the life of mine, net of by-product credits.