Base and precious metals miner Copper Mountain has lowered its production guidance for the year, following a “disappointing” third quarter.

The company, which operates the Copper Mountain mine, in British Columbia, expects copper production to be in the range of 55-million to 60-million pounds, compared with the prior guidance of 65-million to 75-million pounds.

The revised estimate reflects a week of unplanned downtime for repairs to the primary crusher last month.

“Our third quarter clearly did not meet our expectations. Lower grade and lower mill throughput impacted our copper output. We experienced a grade reduction as most of the ore processed in the third quarter came from the lower-grade North pit as opposed to the planned Phase 4 of the Main pit. Our higher-grade Main pit Phase 4 ore release lagged due to spotty ore continuity in the upper benches of that pushback.

“In the second half of September, we advanced mining to consistently large zones of continuous higher-grade ore in Phase 4. We expect that result to continue throughout the fourth quarter and solidify into higher-grade ore production through 2023.

“The North pit ore impacted recoveries due to the higher oxide content in the upper benches of pioneering that pit.

“We also encountered a SAG mill steel grinding ball quality issue, forcing reduced milling rates for about a month. The balls were breaking apart in the mill, significantly affecting throughput during August and into September. Overall, a disappointing quarter and nine months of 2022,” said president and CEO Gil Clausen.

Copper Mountain said that production in the fourth quarter would increase as the company was mining higher grade ore from Phase 4 of the Main pit.  When mining in the Phase 4 area, Copper Mountain has been experiencing grades of about 0.28% copper, and has achieved the design capacity of 45 000 t/d, milling up to 53 000 t/d in October, as well as higher copper recoveries.

The higher-grade Phase 4 ore is expected to be the main source of ore in the fourth quarter of 2022 and in 2023, with grades expected to average 0.27% and 0.33%, respectively.

Production in the fourth quarter is forecast to be the strongest quarter in 2022 and is expected to be 15-million to 20-million pounds of copper.

Copper Mountain expects all-in costs (AIC) to improve in the fourth quarter of 2022 to between $2.90/lb and $3.10/lb because of increased production, minimal sustaining capital costs and minimal to no deferred stripping. In addition, several non-recurring expenses are now complete.

Further, the company has completed all plant improvement projects and therefore expects development capital to also be minimal in the fourth quarter of 2022. AIC for the full year 2022 is thus expected to be between $4.25/lb and $4.50/lb which compares with a prior guidance of between $2.75/lb  and $3.25/lb.