Mount Polley review panel reveal cause of spill

The ‘Globe and Mail’ claims oversight played a role

By Angela Espinoza, News Editor

An independent report released on January 30 declared the 2014 Mount Polley mine spill to be the result of previously overlooked structural issues to the dam holding back the mine’s contaminated water, or “tailings.”

Tailings are used to collect leftover remnants of extracted ores—in the Mount Polley case, such as gold and copper—to prevent toxins from leaking out and polluting the environment.

The tailings pond collapsed on August 4, 2014, releasing several billion gallons of polluted water into nearby lakes and rivers leading into Likely, BC. The leak also resulted in announcements asking locals to avoid non-bottled drinking water roughly “250 miles northeast of Vancouver,” as reported by Bloomberg.

The report was prepared by an expert review panel of three “distinguished geotechnical experts,” and took place between August 2014 and January 2015, according to a press release by the review panel. The report was released to the Ministry of Energy, as well as the T’exelc First Nation and Xat’sull First Nation groups, and the press release states investigative data collecting, lab testing, and numerous interviews were used during the process.

In the report, it is noted that the collapse was due in part to a design flaw that caused the dam to be affected by outside environmental effects such as “sub-glacial” and “pre-glacial” weathering. The flaw was a crack, which filled with a layer of glaciolacustrine (deposits of dirt and rock from glaciers) that resulted in the dam deteriorating from the inside over time.

The report also stated that construction, which caused a “steep slope,” near the mine ultimately triggered the collapse, and that had the area remained flat, the dam would have lasted longer.

Seven recommendations for reviewing and updating similar mines in the future are also laid out in the report. The recommendations include improving “corporate governance,” strengthening “current regulatory operations,” and improving “professional practice” and “dam safety guidelines,” with all having their own lists of criteria.

But while the official report stated human error was not to blame for the dam’s collapse, a timeline dating back to 1997 (up to 2014) by the Globe and Mail outlines several times in which stability of all of Mount Polley’s tailings at the time were a concern as glaciolacustrine was recurrent in the area. The specific issue of glaciolacustrine buildup was reportedly brought forward to then-engineering consultant Knight Piésold between 2005 and 2006, whom the Globe and Mail reports said the glaciolacustrine “would not affect dam stability.”

The Globe and Mail also revealed numerous investigations over several years found glaciolacustrine to be a potential concern, and that improvements to the Mount Polley tailing’s pond were planned prior to its collapse last August.