Mount Polley Tailings Dam Breach Reports & Investigations

Several reports have been published related to various aspects of the August 2014 tailings pond failure at Mount Polley mine in British Columbia. Additional investigations are still underway, from the Canadian government as well as from mine owner Imperial Metals.*

Report Title/Date



Report on Mount Polley Tailings Storage Facility Breach – January 2015

This report by an independent expert review panel analyzes the cause of the August 4, 2014 tailings breach at Mount Polley mine in British Columbia. Experts found that the design was ultimately the cause, and made several recommendations to improve the review process for both existing and future tailings facilities.

“If the inventory of active tailings dams in the province remains unchanged, and performance in the future reflects that in the past, then on average there will be two failures every 10 years and six every 30. In the face of these prospects, the Panel firmly rejects any notion that business as usual can continue.”

The impact of a catastrophic mine tailings impoundment spill into one of North America’s largest fjord lakes: Quesnel Lake, British Columbia, Canada – May 2015


Researchers from the University of Northern British Columbia, University of British Columbia and Fisheries and Oceans Canada document observations of changes in Quesnel Lake and Quesnel River for two months following the August 4, 2014 Mount Polley tailings facility breach.

“The nature of waste materials now present in Quesnel Lake presents a potential hazard to the metal content of aquatic food webs and the growth, survival, and behavior of important fish species.”

Uncertainty Upstream: Potential Threats from Tailings Facility Failures in Northern British Columbia – June 2015


BC First Nations Energy and Mining Council produced a summary of potential threats that may occur in northern British Columbia and Southeast Alaska due to future tailings facility failures. The report includes information on 35 tailings ponds on 48 watersheds, and notes that 3,275km of waterways are immediately downstream from these ponds. Authors call for a higher priority in protecting the environment and ensuring monetary protections are in place for communities in the event they are impacted by tailings failures.

“Nor can we as indigenous peoples afford to watch from the sidelines as others make decisions that will affect our communities, lands, and resources, both today and in the future.”

Post-event Environmental Impact Assessment Report: Key Findings – June 2015


Golder Associates was commissioned by the Mount Polley Mining Corporation to produce this report on post-breach effects as part of its Restoration and Remediation Strategy. It is open for public comment until September 2, 2015. It includes information on physical, chemical and biological impacts as well as descriptions of restoration efforts. There is a 73-page report summary and a 5,405-page full report. 

“This work was conducted in accordance with established scientific methods and protocols to meet or exceed regulatory requirements, such that it would be highly unlikely that potential short term impacts would be missed. However, this work is also considered to be preliminary, as the results of some longer term tests were not available at the time of writing this report.”

Review of the Mount Polley Mine Tailings Pond Failure and Public Interest Disclosure by Public Bodies – July 2015


Elizabeth Denham, Information and Privacy Commissioner for BC: After complaints that the BC government did not let the public know about information it had regarding problems at Mount Polley before its August 2014 tailings breach, Denham has analyzed and reinterpreted existing public disclosure law. “Urgent circumstances are no longer required to trigger proactive disclosure where there is a clear public interest in disclosure of the information,” wrote Denham. Furthermore, she has asked pertinent government agencies to reveal information they have on the Mount Polley breach if it is in the public interest to do so.

“I have been concerned about the proper interpretation of the public interest disclosure requirement for a number of years and chose this investigation as the appropriate opportunity to clarify its interpretation.”

Chief Inspector of Mines Investigation Report on Mount Polley – December 2015


Canada’s Chief Inspector of Mines, Al Hoffman, led an investigation into the Mount Polley incident that became the largest, most complex investigation and analysis ever conducted in British Columbia. (100 interviews, more than 100,000 pages of documents reviewed.) The report includes 19 recommendations directed toward mining companies, the mining industry, mining professionals and regulators. After the report was released, Hoffman noted that mine owner Imperial Metals will not be charged in the incident, as there were “no non-compliances we could find.” He also said that there would be no fines, since B.C.’s mining laws do not allow for administrative penalties.

“We’ve learned from this investigation that in the case of Mount Polley, the allowable margin of risk around the design, construction and management of the tailings storage facility was too narrow to allow for an unknown factor, the layer of unstable soils below the dam embankment. We’ve also learned that weak practices on the mine site increased the risk of dam failure and exacerbated environmental consequences from the beach.” – Bill Bennett, Minister of Energy and Mines


An Audit of Compliance and Enforcement of the Mining Sector – May 2016


British Columbia’s Auditor General was already conducting an audit of mines in BC when the Mount Polley breach occurred. The audit goal was to determine whether the regulatory compliance and enforcement activities of the Ministry of Energy and Mines (MEM) and the Ministry of Environment (MoE), pertaining to mining, were protecting the province from significant environmental risks. They found “almost every one of our expectations for a robust compliance and enforcement program within the MEM and the MoE were not met.” As a result, the Auditor General recommended restructuring the MEM to remove mining compliance and enforcement tasks from its oversight. “We noted the same issues in the Mount Polley file as we did throughout the audit – that is, too few resources, infrequent inspections, and lack of enforcement. We found major gaps in resources, planning and tools. As a result, monitoring and inspections of mines were inadequate to ensure mine operators complied with requirements. The ministries have not publicly disclosed the limitations with their compliance and enforcement programs, increasing environmental risks, and government’s ability to protect the environment.”

The British Columbia Conservation Officer Service (COS) investigation – forthcoming

The COS investigation is based on compliance with Canada’s Ministry of Environment legislation. It could result in charges or fines.


*This table was updated on July 9, 2015 to include an additional report commissioned by Mount Polley Mining Company. It was updated on May 5, 2015 to include reports by Canada’s Chief Inspector of Mines and British Columbia’s Auditor General.