One of the worst disasters that can happen at a producing mine is a tailings dam failure that spills millions of litres of tails into the surrounding watershed. But that is exactly what happened early in the morning of Aug. 4 at the Mount Polley gold-copper mine belonging to Imperial Metals of Vancouver.
The open pit Mount Polley mine and 20,000-t/d concentrator, located near Likely, BC, occupies more than 35,000 ha in the beautiful mountains of central British Columbia. It has provided hundreds of well-paying jobs from 1997 to 2001 and again beginning in 2005 without a major environmental mishap. Now it is on care and maintenance for the foreseeable future.
The failure of the dam was unanticipated.
Imperial said in an Aug. 5 news release: “The cause of the breach is unknown at this time. The dam is an independently engineered structure that operated within design limits and specifications. Monitoring instruments and onsite personnel had no indication of an impending breach. … While the damaged area is relatively small compared to the overall size of the dam, it is not known at this time how long it will take to restore operations.”
The bulk of the flow followed Hazeltine Creek. There are two debris areas: one on the south end of Polley Lake where the dam failed, and a second where Hazeltine Creek discharges into Quesnel Lake near Raft Creek. The aerial images of the affected watershed are frightening, and the immediate area of the tailings dam is devastated.
Reports of how much material escaped the tailings area vary. The CBC put the number at 5 billion litres. Imperial has not yet estimated the amount of water and tails that were discharged.
A water use ban affecting about 300 residents along nearby lakes, creeks and rivers is in effect. The local watershed is considered undrinkable and unsuitable for recreational uses. The debris flows are unstable and the Cariboo Regional District is warning people to stay away from them.
The failure of the dam will be investigated by multiple agencies including Imperial’s mine personnel, local authorities, provincial ministry officials, and the engineers of record. The extend of the breach and the impact of the released water and tailings on the surrounding area will be assessed. There will undoubtedly be fines levied and great outcry about the damage. And perhaps a means of preventing future dam failures will be devised and put in place.
Imperial Metals has always enjoyed a reputation as a good corporate citizen, and this unfortunate incident should not be used to slander that. This writer trusts that the company means what it says, that it is “…deeply concerned and working to mitigate immediate effects and understand the cause.”
Cleanup won’t happen overnight, just as the clock cannot be turned back to before the breach. Far better is for everyone involved to go forward with a certain amount of optimism and support Imperial’s efforts to mitigate the damage and investigate the cause.