More to tailings dam debacle than Victoria allows us to see
Mount Polley report: What’s in the 150 pages of material withheld by the government?
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.
Without such a beach, the engineering firm warned, “the tailings dam is effectively being operated as a water-retaining dam” — something it was never designed to be.
But as the panel went on to record, “during the ensuing months this chronic water surplus problem would become acute.” Then in May of last year, the water, boosted higher by torrential rains and a heavy spring run-off, almost over-topped the dam.
A second, no less telling set of exclusions from the documentary record deals with that neardisaster, which happened just 10 weeks before the dam breached.
Among the dozen and a half documents removed from the record is a two-page email from Heather Narynski, senior technical inspector for the mines ministry, to George Warnock, manager of geotechnical engineering in the ministry’s Prince George office.
It was filed on May 27, just two days after a representative of the mining company (whose name was redacted from the documents) reported water seeping over the dam core at a low area of the embankment.
The topic of the email was “Mount Polley tailings storage facility dam freeboard” — the latter being the technical term for the gap between the top of the tailings pond (including wave height) and the top of the dam.
Contents withheld by government directive. But on the 28th, Dmitri Ostritchenko, geotechnical engineer with AMEC, the engineering firm of record on the dam, reported that the freeboard at the dam was for all intents and purposes “zero.”
That estimation, quoted here Tuesday, is taken from one of the few documents regarding the late May episode to make it through the government sieve. It also recorded the on-site engineer’s concern that the company was continuing to dump tailings into the pond, despite the almost total lack of freeboard.
Withheld from the record is an eight-page letter from Ostritchenko to the ministry’s Narynski, dated the end of May and detailing the effort to stabilize the dam.
Also withheld from the record was the final report from BGC, detailing the firm’s recommendations for stabilizing the dam in the long term, including a proposal to add a supporting buttress in the midst of the section that failed.
Alas, it was delivered in late July, just days before the breach.
In short, it would appear that the government tried to exclude as much material as possible from the documentary record regarding the implications of the ever-rising tide of water behind the ever-rising tailings dam.
Perhaps there’s also a connection to the search warrant executed Wednesday at the parent company of the Mount Polley mine.
But at the very least, the exclusions suggest there is more to be learned about this debacle than what is on the record to date.
A full inventory of the more than 100 documents removed from the record by government directive has been compiled by Will Koop, co-ordinator for the B.C. Tap Water Alliance. The list is posted at www.bctwa.org, website for the alliance.