In response to the findings and recommendations of the chief inspector of mines’ (CIM) investigation into the breach of tailings storage facility (TSF) at Mount Polley mine in August 2014, Bill Bennett, energy and mines minister for British Columbia, announced during mid-December that the government will introduce new regulations and requirements that will make the province a national and international leader in safety standards for TSFs.
The CIM report found, as did the independent expert panel in January, that the dam failed because the strength and location of a layer of clay underneath the dam was not taken into account in the design or in subsequent dam raises. The chief inspector also found other factors including the slope of the perimeter embankment, inadequate water management, insufficient beaches, and a sub-excavation at the outside toe of the dam exacerbated the collapse of the dam and the ensuing environmental damage.
While the breach would not have occurred had it not been for the undetected glaciolaucustrine layer of soils (UGLU), the consequences of the breach were made worse by the other factors. Although operations on the mine site were not in contravention of any regulation, the chief inspector found the mine failed to operate using best available practices.
“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,” Bennett said. “This is unacceptable. My commitment is to implement all recommendations, work with the MABC and MAC, the APEGBC and the CDA to ensure that risk of dam failure is reduced by better regulations, better policies and better professional guidelines.”
The chief inspector of mines investigation team conducted approximately 100 interviews and reviewed more than 100,000 pages of documents going back to 1989. This is the largest and most complex investigation and analysis ever done in British Columbia.
“We conducted a very thorough and in-depth examination of the Mount Polley Mining Corp.’s actions from its initial site investigations 26 years ago to present,” said Al Hoffman, chief inspector of mines for British Columba. “Through our investigation, we determined that while the mine did not contravene any existing regulatory requirements, its management and operational practices failed in a number of areas such as water management and misplaced confidence in the TSF design.”
The CIM made 19 recommendations in seven categories directed toward the mining operator, the mining industry, professional organizations and the government regulator to prevent such incidents in the future, and build a safer, more sustainable industry. The government will be working to implement all of the recommendations.
Other actions will be taken to strengthen the government’s compliance and enforcement of mining. Bennett plans to introduce legislation in 2016 to add administrative penalties under the Mines Act. Compliance and enforcement tools under the Mines Act are presently limited to shutting down a mine through the cancellation of a permit, issuance of stop-work orders or pursuing prosecutions. The proposed legislation would give ministry staff the power to issue penalties for noncompliance.
The chief inspector found that the mine and its engineers employed weak practices on the mine site and many recommendations go to new standards and guidelines to improve these practices. Weak practices, however, do not constitute a legal contravention of existing mining legislation. The CIM, with advice from the Ministry of Justice, did not find sufficient evidence that Mount Polley Mining Corporation contravened existing regulatory requirements. Based on these findings, the Chief Inspector of Mines determined there were no actions that would warrant a report to Crown Counsel pursuant to the Mines Act.
“My recommendations address these issues and will strengthen British Columbia’s regulatory framework and build a safer, more sustainable industry,” Hoffman said.
The British Columbia Conservation Officer Service (COS) is still conducting its investigation into the Mount Polley accident. The COS investigation is based on compliance with the Ministry of Environment legislation. It is possible that this investigation may find noncompliance that warrants a report to Crown Counsel.