On the morning of October 22, 2025, Teck Resources set out its third-quarter numbers, and in them a quieter story about how a mine grows its own walls. At its QB copper operation in British Columbia, output fell to 39,600 tonnes, because the crews who raise the tailings dam must sometimes stop the concentrator to let the earth settle. Behind that pause lies an old engineering dilemma: the sand meant to make the dam stable drains too slowly, so the work continues the harder way, one rock bench at a time. The company expects this constraint to ease from 2027, though the path there runs through a
Teck's Q3 Copper Output at QB Falls 12,900 Tonnes as Tailings Constraints Force Mill Downtime
One month of idle mill explains much of the quarter.
Mark
So the headline number is copper down 12,900 tonnes. What's actually behind it?
Mimi
The tailings dam. QB can't run the concentrator flat out because the tailings rise faster than the dam is being built, so Teck has to stop the mill. September was the worst: 20 days of downtime, 5,800 tonnes.
Mark
And the dam is slow because of sand?
Mimi
Yes. The plan is a sand wedge made of hydraulically placed sand. The sand meets spec, but ultra-fines make it drain slowly, so the wedge is delayed and crews keep building rock benches instead.
Luke
Worth flagging that the sand explanation is Teck's own. The release doesn't include independent verification of the cause.
Mark
What's being done about it?
Mimi
Modifying the cyclone facility to remove ultra-fines, and changing paddock design and how sand is placed and dried. Teck says test results were positive and some improvement has been seen.
Luke
But note the wording: positive test work, some improvement, further progress needed. No drainage figures are given, so we can't judge how close it is to design targets.
Mark
And the 2027 expectation?
Luke
That's a forward-looking statement. Teck says TMF development should stop constraining throughput from 2027, but it also expects more downtime in 2026. That's an expectation, not a result.
Mimi
The shiploader is separate. Repair is due in Q1 2026, and Teck says it isn't hurting production because concentrate is shipping through other ports.
Luke
Again, that's the company's assessment. The release doesn't say what the alternative arrangements cost.
El Pulso
- QB copper output dropped to 39,600 tonnes in the third quarter, down 12,900 tonnes from a year earlier, as the concentrator repeatedly stopped.
- September alone yielded just 5,800 tonnes after 20 idle days, a sharp reminder of how fragile the schedule has become.
- Ultra-fines in the sand are slowing drainage, stalling the sand wedge that was meant to keep the tailings dam steady.
- Teck is modifying its cyclone facility and adjusting sand placement, while a shiploader repair pushes shipments through alternative ports until the first quarter of 2026.
On the morning of October 22, 2025, Teck Resources set out its third-quarter numbers, and in them a quieter story about how a mine grows its own walls. At its QB copper operation in British Columbia, output fell to 39,600 tonnes, because the crews who raise the tailings dam must sometimes stop the concentrator to let the earth settle. Behind that pause lies an old engineering dilemma: the sand meant to make the dam stable drains too slowly, so the work continues the harder way, one rock bench at a time. The company expects this constraint to ease from 2027, though the path there runs through another year of interrupted production.
In September, Teck Resources' QB copper mine managed only 5,800 tonnes of copper. For twenty days the concentrator sat idle while crews raised the crest of the tailings dam, and that single month reveals much of what the company reported on October 22, 2025, in its unaudited third-quarter results.
For the full quarter QB produced 39,600 tonnes of copper, 12,900 tonnes fewer than a year earlier. Teck traces the shortfall to the pace of building its tailings management facility. The concentrator must sometimes shut down to control how quickly the tailings rise, and that downtime was heaviest this quarter. Molybdenum, at 480 tonnes, was held back by the same stoppages.
The root problem is sand. Teck intends to build a sand wedge from hydraulically placed sand, but ultra-fines make the material drain slowly, delaying the work. Until the wedge is ready, crews build rock benches by machine, and that means more downtime through 2025 and into 2026. The company says its 2026 guidance already accounts for it.
Teck is working on two fixes: stripping out ultra-fines with new cyclone technologies, and changing how sand is placed and dried. Some gains have appeared, but not yet enough to reach design targets. The company's stated priority is safe, uninterrupted production, and it expects tailings work to stop limiting throughput from 2027.
At the port, the QB shiploader is under repair and due back in the first quarter of 2026. Teck says shipments are moving through other arrangements and local sales have been maximized, so production should be unaffected. Nothing new was announced on guidance, which was revised on October 7. Investors will be watching whether the cyclone changes improve drainage and whether 2026 downtime stays within what guidance assumes.
In September, Teck Resources' QB copper mine produced just 5,800 tonnes of copper. The cause was 20 days in which the concentrator sat idle so crews could raise the crest of the tailings dam. That one month explains much of what the company reported on October 22, 2025, in its unaudited third-quarter results.
For the full quarter, QB produced 39,600 tonnes of copper, which is 12,900 tonnes less than in the same period a year earlier. Teck says the shortfall traces to the pace at which its tailings management facility, or TMF, is being built. The concentrator has to be shut down at times to manage how quickly the tailings rise, and the company says that downtime was heaviest in the third quarter. Molybdenum output was 480 tonnes as the molybdenum plant continued its ramp-up, and it too was held back by the same concentrator stoppages.
The underlying problem is sand. Teck's plan is to build a sand wedge from hydraulically placed sand, which would allow the TMF to operate in a steady state. The company says the sand it is producing meets design specifications. But ultra-fines in the material make it drain slowly, and that has delayed work on the wedge. Until the wedge is ready, crews must keep building rock benches mechanically to raise the dam crest. That work has meant extra downtime through 2025 and is expected to bring more in 2026. Teck says the 2026 annual production guidance for QB already reflects it.
Teck describes two initiatives advanced in the quarter. The first is removing ultra-fines. Test work with cyclone manufacturers and third-party experts has shown positive results in improving drainage, according to the company. As it previously disclosed, Teck is modifying the cyclone facility this quarter to add alternative technologies built to strip out the ultra-fine material. The second is refining how sand is placed: changes to paddock design, and to how sand is placed and dried, are being put in place to improve drainage efficiency. Teck says some improvement has been realized so far, but further progress is needed to reach design targets.
The company's priority, it says, is safe, unconstrained production by raising the dam crest. Its expectation is that from 2027 onward, TMF development should no longer limit throughput.
A separate problem is at the port. The shiploader at QB's port facility is under repair, and Teck expects it back in service in the first quarter of 2026. The company says the outage should not affect production, because concentrate has been moving through alternative port arrangements and shipments to local customers have been maximized.
On guidance, nothing new was announced with the quarterly results. On October 7, Teck completed its Comprehensive Operational Review and Updated Outlook, which revised production guidance for QB and Highland Valley Copper for 2025 through 2028, Red Dog for 2026 through 2028, and Trail for 2026. For 2025, QB is expected to produce 170,000 to 190,000 tonnes of copper and 1,700 to 2,500 tonnes of molybdenum. QB net cash unit costs for 2025 are expected to be between US$2.65 and US$3.00 per pound. Teck says that net cash unit cost is a non-GAAP measure.
On safety, the company reported a high-potential incident frequency rate of 0.06 for the nine months ended September 30, 2025. That is about 50 percent below the 2024 annual rate of 0.12.
Teck held an investor call on October 22 at 8:00 a.m. Pacific to discuss the results. The things to watch are whether the cyclone modifications improve sand drainage and whether the 2026 downtime stays within what guidance already assumes.
Citas Notables
Production at QB continues to be constrained by the pace of development of the tailings management facility, requiring concentrator downtime.— Teck Resources, Q3 2025 results release (paraphrased)
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