Chilean regulator, workers flagged risk at Teck's Quebrada Blanca dam

SANTIAGO, Dec 9 - Chilean authorities in August raised concerns over a large crack and leaks at Teck's flagship Quebrada Blanca copper mine and criticized the miner for not immediately reporting the issues, according to documents reviewed by Reuters.

The crack and leaks were alarming enough to lead some workers to ask mining regulator Sernageomin to investigate potential safety risks, according to five complaints between July 28 and August 8.

The mine has had problems since ‍2024 at its ​tailings dam - an embankment that stores mine waste - causing Teck to cut production guidance at Quebrada Blanca.

In response to questions from Reuters, ‍Teck said the tailings dam is stable and safe, and construction is proceeding.

"There was never any risk to the safety or integrity of the facility or to employees," Teck added.

The documents, obtained from Sernageomin through a public records request, also show that ​Teck responded to the ​regulator that it had fixed the issues and informed workers they were not at risk.

Workers' concerns initially related to leaking in late July.

On July 28, a worker wrote to Sernageomin that there were leaks on the dam wall.

Sernageomin's inspection on August 1 was in part triggered by that complaint, as well as another complaint over lack of proper personal protective gear, the agency said in a report of its findings.

The ‍worker complaints continued in the following days - including, starting August 3, concerns about a large fissure along the top of the wall.

"There is a serious problem with the tailings dam wall and the information from ​the company is not very clear," said one complaint. 

Another person wrote to Sernageomin: "Teck personnel ignore everything ⁠that's happening and just don't want to stop producing ... I beg you to go to the workplace."

Sernageomin inspections on August 1 and 2 identified a crack running 240 meters (790 ft) horizontally across the top, or crest, of the main dam wall, leaving an 18-centimeter gap. It also found pools of water at the base of the wall, and rebuked Teck for not swiftly reporting the issues.

"The company must immediately or promptly notify the service of any incidents," it said in its inspection report, signed by both ​Sernageomin and Teck representatives.

In a follow-up report dated August 5, Sernageomin said: "This service is concerned about what was observed in the field regarding operational findings on the deposit wall, specifically the water seepage and cracks on the crest."

Since early August, Teck has sent ‌weekly monitoring reports to Sernageomin, according to the documents reviewed by Reuters.

In its reports, letters ​and presentations to Sernageomin, as well as minutes of weekly meetings with regulator representatives, Teck said it had held drills for structural collapse scenarios and was preparing an analysis of the root causes of the crack and leaks.

Teck told Reuters the cracks that appeared in late July were not unusual for this type of dam construction and were quickly repaired. Around that time, it also resolved a pipeline leak that it said had "resulted in water discharge."

"Work is continuing as planned on the facility to enable full ramp-up of QB," Teck said.

Analysts view the issues at Quebrada Blanca as a key part of what prompted Teck to seek a merger with rival Anglo American, which will allow for shared operations with the neighboring Collahuasi mine. Anglo American has said it supports Teck's strategy for Quebrada Blanca and has experience from similar tailings dam problems in the past at its Quellaveco mine in Peru.

Teck shareholders are expected ‍to vote on the deal on Tuesday.

Failure to get output on track in the next couple of years could weigh on the merged company's valuation, analysts say.  

Teck has not discussed the Sernageomin inspection, ​or the crack and leaks, in its financial disclosures. It has, however, addressed why certain core problems at the tailings dam forced the miner to slash Quebrada Blanca's production targets and commit to spending $420 million next year on improvements.

Safety standards for tailings have ​come under increased scrutiny worldwide after the 2019 collapse of the Brumadinho tailings dam in Brazil that killed 270 people. 

Tailings experts consulted by Reuters said ‌cracks and leaks can be red flags for dam stability, requiring consistent monitoring and identification of the root cause.

"They are like symptoms at the doctor's office. They may indicate some underlying, major sickness or disease if not addressed," said Rennie Kaunda, a mining engineering professor at the Colorado School of Mines. REUTERS