Whether or not the collapsed tailings pond dam at Mount Polley could have been avoided has become a matter of debate here in the Columbia Valley.
In a written exchange, Columbia River-Revelstoke MLA Norm Macdonald and former BC Liberal candidate Doug Clovechok have accused each other of spreading misinformation for the benefit of their respective political parties.
“The BC Liberals said the failure was completely unpredictable. That is not true,” Macdonald stated in his bi-weekly MLA Report that was published in January 28th issue of The Valley Echo. “This government’s sloppiness made this failure completely predictable.”
In a response issued Saturday, February 7th, Clovechock argued that Macdonald’s claims are “completely untrue and are completely refuted by the conclusions found by an independent panel that investigated the incident.”
In a rebuttal, Macdonald quotes Vaughn Palmer of the Vancouver Sun, who read the panel’s report in its entirety: “Mount Polley was not a story of one flaw that went undetected for years with nothing to be done about it. Rather, it was characterized by a pattern of dubious behaviour, margins of safety that skirted the edge of the cliff, little thought of worst-case scenarios, all factors in a disaster waiting to happen.”
Roughly 150 pages of the panel’s findings have been withheld to prevent interference with ongoing investigations, according to the provincial government.
From what was publicly released of the report, the panelists found a number of contributing factors, but state that a flawed design of the tailings pond was a leading contribution, having been situated above a layer of earth weaker than previously thought. The panelists say the straw that broke the camel’s back was the construction of a steep downstream rockfill zone. The construction of the rockfill zone was on a slope with a grade steep enough to cause the breach, according to a press release.
The press release goes on to suggest that current inspection practices were not able to adequately detect the hazard.
“Inspections of the tailings storage facility would not have prevented failure. Regulatory staff are well qualified to perform their responsibilities and they performed as expected.”
“Basically the weight of the dam was too much for the weak materials in the foundation to bear,” said U.S. consulting engineer Steven Vick, one of the three experts.
The report concludes that the concrete-like glacial till material in the base of the dam wasn’t understood in enough detail when the dam was designed and built in 1997. Later raising of the dam to hold more water and tailings weakened the base layer and led to the failure.
Vick said the additions to the dam were built with a steeper slope than the original dam, and plans to buttress the area were delayed until it was too late.
Seven recommendations were made through the report, which Minister of Energy and Mines Bill Bennett said the province will fully implement.
Two more investigations of the mine failure are pending. Bennett said the Chief Inspector of Mines is likely to release his report by this summer, and the Conservation Officer Service will also report when its investigation is complete.
Bennett said the government is willing to see the Mount Polley mine reopen, but the other investigations must be complete first. The parent company Imperial Metals has applied to use an existing pit to store tailings and resume operations without using the original tailings pond again.
~With files from Tom Fletcher