Documents missing, unanswered questions on Mount Polley dam breach – by Vaughn Palmer (Vancouver Sun – February 3, 2015)

What’s in the 150 pages of material withheld by the B.C. government?

VICTORIA — When a trio of engineering experts reported their findings on the failure of the Mount Polley tailings dam last week, they warned that not every document assembled by their panel could be released.

Some 100 of 850 documents were withheld on directions from the ministry of mines and the ministry of environment, which were still conducting their own investigations into the disaster.

Not wanting to compromise ongoing investigations was one reason, protection of privacy the other. But the result prevented publication, for now anyway, of the supporting documentation for the most telling findings in the report.

Still, one can make assumptions about the contents of the withheld documents by working backwards from the meagre details provided, coupled with the brief passages quoted in the panel report.

The government ordered the exclusion of most of the documents produced by BGC Engineering, the firm that was hired by the mine operator in 2013 to preside over the next raising of the dam to keep ahead of the rising water level in the tailings pond.

The withheld material, some 150 pages in all, was mostly directed to Luke Moger, project engineer, mining operations for the Mount Polley Mining Corporation. Much of the material was written by Daryl Dufault and Todd Martin, both senior geotechnical engineers at BGC. Martin, one notes with irony, also teaches a course in “Tailings Management 101.”

For according to the panel’s summary of the material in the excluded documents, the firm presided over a shift to a “more conservative approach” to raising the tailings dam.

“The outlook was not good,” wrote the panel, summarizing the firm’s recommendations to the mine operator. “BGC made explicit the connection between the structural limitations of the dam and the ever-growing volumes of surplus water it was being called upon to contain.”

As early as June 2013, BGC was urging the establishment of a continuous barrier of tailings — known as a “beach” — to prevent the rising tide of water from eroding the earthen embankment of the dam itself.

“An above-water tailings beach separating the core from the water pond constitutes a fundamental design element of the dam,” wrote the engineers in one of the few passages of their correspondence to make it into the panel report.

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