Mount Polley Dam Collapse
Mount Polley tailings dam collapse
Tailings dam located at mount Polley Mine
Gold and copper mine in British Columbia
Open pit mine 2 pits
Operated by mount Polley mining corporation
Operations began in 1997 and closed in 2019
20,113 hectare area
Collapse occurred 04 August 2014
The event
Mount Polley mine, B.C. Canada is a Gold and Copper mine that has been in operation since 1997, with 2 open pit mines where material is excavated. Throughout this time a large amount of mine waste has been generated and inorder to prevent this material entering the wider environment tailings dams were used, in this case a 4 km^2 tailings dam. Over the operational period of the mine an excessive amount of tailings and supernatant were loaded into the dam. On the 4th August 2014 the excessive load within the tailings dam led to a breach releasing 24 million m^3 of water containing a slurry of materials including potentially toxic metals into the wider environment. The breach flowed into Polley Lake raising the water level by 1.5 metres, where it continued to be transported through the interconnected fluvial network of the region, through Hazeltine Creek before Quesnel Lake and finally Cariboo River. As the mixture of tailings and supernatant flowed throughout the region it carried with it a mixture of trees, mud and debris that were picked up during the movement of the contaminated material throughout the region. With damage to 9 km of the banks of Hazeltine Creek as the spill emptied throughout the region, dumping most of the material into Quesnel Lake. Since the breach $71 million (CAN) has been spent on rehabilitation work. However, as of 2021 no charges have been brought.
Remediation Efforts
Remediation and reconstruction have been underway at the site since 2014. Since this time investigations have been conducted into the impact of the dam failure on human health, safety and the impact to local ecosystems. Simultaneously the removal of the tailings from the wider environment, bank reconstruction, habitat repairs and vegetation replanting has taken place. The investigations during the remediation noted that there were elevated levels of selenium, arsenic and other metals that are consistent with historical records from environmental monitoring. Following this the environmental damage had been determined to be primarily physical in nature, with the destruction of local ecosystems and shoreline, rather the initial threat of chemical contamination from the tailings. With fears of further environmental damage from the tailings, such as acid mine drainage, being put at ease as the composition of minerals in the local volcanic geology acting as a neutralising agent. As such, the tailing have been classified as environmentally inert posing no environmental issue.
Aftermath
Negligent behaviour
Complaints have been made about potential negligent behaviour being a factor in the tailings dam collapse, with official inspection reports for the Mount Polley tailings dam being withheld since 2010, prompting protests from First Nations people.
On 18 August 2014, the British Columbia government ordered an independent engineering investigation into the pond breach and a third-party review of all 2014 dam safety inspections for every permitted mine's tailings pond in the province.
Following the event, on 18 august 2014 the government of British Columbia ordered an independent investigation into the engineering of every tailing pond within the province, in an effort to prevent another disaster and to understand why this collapse occurred. This report found that the tailing dam collapse at Mount Polley occurred due to the presence of a layer of glacial till underlying the structure that had previously been unaccounted for by mount Polley mine’s original engineering contractor. In 2010 The engineering firm reported broken piezometers and a 10 metre crack in the structure of the dam, with efforts being made to address these issues.
As of 2018 three of the engineers who worked on the tailings dam were charged with either negligence or unprofessional conduct by their respective professional associations. With the final report outlining that the tailings dam collapse due to the negligent operation of the dam as a result of overfilling beyond design despite multiple warnings. This is further combined with a previous breach months prior and other design flaws.
Fallout from the disaster
As of 2021 no charges for environmental damage have been presented with no word on any timing for an official decision, leading to environmental law experts in Canada stating that they can not rule out the potential for no charges being issued for the country's worst spill in the last 50 years. This came in the wake of the 3 year deadline for the filing of environmental charges under Provincial law passing in 2017 as well as a further 5 year deadline passing in 2019. Following a 4 year investigation by a team from Environment Canada, Fisheries, Oceans Canada and B.C. Conservation officer service recommendations of charges were delivered in early April 2019. However, federal prosecution service on the case as well as federal environmental ministries have refused to make further comments on the case.