Disaster Strikes at Mount Polley Mine


On August 4, 2014, the tailings storage facility dyke collapsed at the Mount Polley gold and copper mine in British Columbia, Canada. The collapse released approximately 10.6 million cubic meters of water and 13.8 million cubic meters of tailings slurry. The amount of tailings released into the environment from this breach was approximately the size of New York’s Central Park. Imperial Metals Corporation owns the Mount Polley Mine and the mine is both an open pit and underground mining operation for copper and gold. The engineering company, Knight Piesold, designed and built the tailings storage facility throughout the 1990s.

Imperial Metals had many warning signs that not all was right with the tailings storage facility for the Mount Polley Mine. In 2010, an employee working at the tailings facility discovered a tension crack, but failed to report the crack to the engineering company. Two months later, Knight Piesold’s inspectors discovered the crack at the mine and recommended that the company perform a stability assessment to determine if the crack caused weakness in the dam wall. The crack was approximately 900 meters from the breach which occurred in August. However, it is not clear whether the tailings breached the storage facility because of the crack. Knight Piesold expressed other concerns regarding the Mount Polley Storage Facility. During its inspection in October, 2010, approximately 40 percent of the 92 instruments used to measure water pressure did not work. Also, the engineering company expressed concerns that the mining facility was operating over capacity. In response to these concerns, Mount Polley Mining Corporation, a wholly owned subsidiary of Imperial Metals, released a statement, on October 3, 2014, saying that it complied with the inspections and reports of the engineering company and no one raised any additional concerns.

In February, 2011, Knight Piesold refused to continue working with Imperial Metals at the Mount Polley Mine. Although there was no express reason why the engineering company stopped working at the storage facility, Knight Piesold, in a letter to Imperial Metals, indicated that the “overall tailings impoundment [were] getting large and [that it was] extremely important that [the tailings storage facility] be monitored, constructed and operated properly to prevent problems in the future.” In the letter, Knight Piesold refused to assume responsibility for further operations at the mine.

The breach of the tailings storage facility is one of the largest environmental disasters in mining history. Imperial Mines and the Canadian government will have to spend decades cleaning up the pollution from the tailings. Although the long-term effects of the breach are unclear, experts are speculating about the impact of the contamination of the tailings on the water, environment, society, and politics of Canada.

Environmental Impacts:

The damages from the breach at Mount Polley seem to be more physical in nature rather than chemical. The physical damages include the deposition of tailings, trees, and other debris in Polley Lake, Hazeltine Creek, and Quesnel Lake, which are all fresh water sources. These lakes and creek provide drinking water to local residents in the area surrounding the Mount Polley Mine.

When the tailings first breached the storage facility on August 4, 2014, the government of British Columbia imposed a drinking water ban. However, a week later on August 12, health officials and the British Columbian government mostly lifted the ban and stated that the fish in the area were safe to eat. The only areas where the government did not lift the ban was in areas that received drinking water from Polley Lake, which is adjacent to the tailings facility, Haseltine Creek, and a small portion of Quesnel Lake. On October 3, 2014, the Environmental Protection Division of the British Columbian government released a statement indicating that all the results for Quesnel Lake were below the drinking water guidelines with the exception of aluminum. Though the water had elevated levels of aluminum, according to Health Canada, there is no evidence that the elevated levels will cause adverse health effects.

Imperial Metals claims that there will not be much chemical damage to the surrounding landscape and water. Imperial Metals further asserts that water in the tailings pond was not toxic and was close to drinking water. According to Imperial Metals, much of the sediment released into the surrounding environment is composed of similar materials as the surrounding rocks formations. Further, the Imperial Metals owner and operator claims that the tailings are alkaline and not acid generating. Imperial Metals’ expert states that this means that the metals in the rock are less likely to be released due to acid erosion. The tailings that seep into the ground will cause contamination similar to that of glacial deposits of silt in the area. However there still may be long-term effects of leaving the tailings in the environment. Although the rocks will not erode as quickly because the tailings are not acid generating, eventually the tailings will start to weather and release metals into the environment.

Social and Political Impacts:

The breach of the mine has eroded the faith people have in the government of British Columbia because, in the last decade, the provincial government has heavily supported resource extraction. Politicians have developed close working relationships with the mining industry. For example, Imperial Metals has donated approximately $200,000 to the British Columbia majority party since 2005. Activists assert that the government’s relationship with extraction industries created a conflict of interest, which prevented inspectors from identifying and acting on the Mount Polley disaster potential.

Government inspections of mines have been cut in half since 2002. In 2010, the government’s geotechnical engineers only performed 3 inspections in British Columbia. The year before, in 2009, the engineers conducted 22 inspections. In 2011, engineers completed only 2 inspections. During 2010 and 2011, British Columbia’s engineers did not visit the Mount Polley Mine. However, inspectors did inspect the Mount Polley Mine tailings facility in September, 2013, and the engineers did not report any violations. It is too early for experts to discern whether there is a connection between the engineer’s missed inspections and the failure of the storage facility at Mount Polley Mine. However, the fact that the government did not diligently send geotechnical engineers to inspect mining sites calls into question the government’s ability to prevent a future disaster like Mount Polley.

Because of the tailings breach, the David Suzuki Foundation set-up a petition to institute a moratorium on new mines approvals. However, if British Columbia prevented new mines from opening, it could hurt a substantial part of its economy. Last year, mining accounted for more than 8 billion dollars in revenues and 10,000 jobs. Thus, because there is little information about what actually caused the Mount Polley Mine to collapse, it is premature to stop new mining operations altogether.

Next Steps:

The government, in order to regain the public’s trust, commissioned an independent engineering panel to assess and determine the reasons why the storage facility failed. The government appointed four geotechnical experts who have experience with tailings management facilities. Imperial Mines has set up community meetings with the surrounding residents immediately affected by the discharge of the tailings. The purpose of these meetings is to keep local residents apprised of what Imperial Metals plans to do during remediation and reclamation of the environment.

Imperial Metals has already developed plans to mitigate the effects of the tailing breach. However, these plans are theoretical and Imperial Metals has yet to implement such measures. The company plans to improve water quality in Quesnel Lake by providing water management structures. It plans to try to control the flows of the tailings and divert the tailings from Quesnel Lake into the Springer Pit, which is an open pit at the mine.

Further, despite the fact that the tailings are not acid generating, Imperial Metals will still have to continually test the water to ensure and reassure local residents that their drinking water has not been contaminated. If all of the damage is indeed physical, rather than chemical, Imperial Metals will have to reshape the landscape, reseed, and try to remove the tailings from the environment.


The long-term environmental and social effects of the tailings storage facility breach at the Mount Polley Mine are still unknown. It is also too early to estimate the total costs to Imperial Metals for environmental remediation and reclamation. However, Imperial Metals and the British Columbia government will have to work hard to regain the trust of the local residents and to develop an effective plan to address environmental damages caused by the release of the tailings into the surrounding terrain of the Mount Polley Mine. Although it is too early to estimate the costs of remediation and reclamation, Imperial Metals obtained $115 million in financing to cover environmental damage and mitigation alone.


The title picture features a map of the Mount Polley Mine site. This image is part of the public domain as it was created solely by NASA. NASA does not endorse this blog.


Letter from Knight Piesold Consulting, to Brian Kynoch, Mount Polley Mining Corp., (Feb. 10, 2011) (regarding Mount Polley Tailings Storage Facility Engineer of Record), available at http://www.knightpiesold.com/en/assets/File/VA11-00298_Complete.pdf.

Press Release, Mount Polley Mining Corp., Mount Polley Responds to Vancouver Sun Article Published on September 26, 2014 (Oct. 3, 2014), available at http://www.imperialmetals.com/i/pdf/10-03-14-mount-polley-responds-to-sept-26-vancouver-sun-article-oct-3.pdf.

Lyn Anglin, Getting a Better Understanding of the Mount Polley Tailings, Resource Works, http://www.resourceworks.com/getting-a-better-understanding-of-the-mount-polley-tailings.html (last visited Oct. 14, 2014).

Announcement on Mt. Polley Inquiry This Week, Bennett Says, The Townsman (Aug. 12, 2014), http://www.dailytownsman.com/breaking_news/270905121.html.

Chronology of Major Tailings Dam Failures, Wise Uranium Project, http://www.wise-uranium.org/mdaf.html (last updated Sep. 4, 2014).

Kenneth P. Green, Beware Hasty, Unwise Policy Decisions After Mount Polley, Huffington Post (Aug. 12, 2014), http://www.huffingtonpost.ca/kenneth-p-green/first-investigate-then-ac_b_5670031.html.

Gordon Hoekstra, Imperial Metals Says It Addressed 2010 Concerns at Mount Polley Mine, The Vancouver Sun (Oct. 5, 2014), http://www.vancouversun.com/Imperial+Metals+says+addressed+2010+concerns+Mount+Polley+mine/10264841/story.htm.

Gordon Hoekstra, Mount Polley Mine Tailings Spill Nearly 70 Percent Bigger Than First Estimated, The Vancouver Sun (Sep. 3, 2014), http://www.vancouversun.com/Mount+Polley+mine+tailings+spill+nearly+cent+bigger+than+first+estimated/10172302/story.html.

Justine Hunter, B.C. Didn’t Inspect Mount Polley Mine in 2010, 2011, The Globe and Mail (Oct. 14, 2014), http://www.theglobeandmail.com/news/british-columbia/bc-didnt-inspect-mount-polley-mine-in-2010-2011/article21084272/.

Independent Expert Engineering Review Launched Following Mount Polley Dam Breach, British Columbia Newsroom (Aug. 18, 2014), http://www.newsroom.gov.bc.ca/2014/08/independent-expert-engineering-review-launched-following-mount-polley-dam-breach.html.

Peter Moskowitz, Mount Polley Mine Spill: A Hazard of Canada’s Industry-Friendly Attitude?, The Guardian (Aug. 13, 2014), http://www.theguardian.com/environment/2014/aug/13/mount-polley-mine-spill-british-columbia-canada.

Anna Mehler Paperny, What’s in Imperial Metals’ Mount Polley Tailings? Should you be Worried?, Global News (Aug. 5, 2014), http://globalnews.ca/news/1493012/whats-in-imperial-metals-mount-polley-tailings-should-you-be-worried/.

Tailings Breach Information, Imperial Metals, http://www.imperialmetals.com/s/Mt_Polley_Update.asp?ReportID=671041 (last visited Oct. 14, 2014).