Copper miner Antofagasta on Wednesday lowered its full-year guidance to between 640 000 t and 660 000 t, citing the pipeline incident at Los Pelambres and the continued uncertainty about water availability.

Copper production in the first six months of the year dropped by 25.7% year-on-year to 268 600 t, the London-listed company reported.

Throughput at Los Pelambres was 36.2% lower than in the first half of 2021 and the grades at Centinela Concentrates were 35.4% lower.

Second-quarter output fell by 6.5% quarter-on-quarter to 129 800 t. The concentrate pipeline incident at Los Pelambres reduced production by about 23 000 t in the quarter.

Operation of the pipeline resumed by the end of the quarter and 12 000 t of copper concentrates are stockpiled at the concentrator to be moved to the port by October.

Gold production for the quarter decreased by 7.8% to 35 400 oz and molybdenum output was 2 000 t.

Net cash costs were $1.90/lb in the second quarter and $1.82/lb for the first half of the year, compared with $1.75/lb in the previous quarter and $1.14/lb in the first half of 2021.

“Reduced production levels and higher costs compared to last year reflect the expected impact of the drought and the temporary closure of the concentrate pipeline at Los Pelambres in June, as well as lower grades at Centinela Concentrate,” said CEO Ivan Arriagada.

Looking at the second half, he said Antofagasta expected production to increase quarter-on-quarter as throughput recovered at Los Pelambres with increased water availability, the grade improved at Centinela and as the copper in concentrate, stockpiled at Los Pelambres’ concentrator plant, was moved to the port.

“The significant decline in the copper price since the beginning of June has reinforced our commitment to control costs, particularly during this period of higher input prices and general inflation,” said Arriagada.

The lower copper output, coupled with the high current levels of inflation, was partially offset by the weakening of the Chilean peso and Antofagasta now estimates full-year net cash cost guidance at $1.65/lb.