A ‘dangerous game’ at Mount Polley preceded disaster, according to senior engineer (Vancouver Sun)
The ill-fated tailings dam at Imperial Metals’ Mount Polley mine was an improvised work in progress, built higher every year to hold back the growing volumes of water behind it....
... "... it could have failed by over-topping, which it almost did in May 2014. Or it could have failed by internal erosion, for which some evidence was discovered.
“Clearly, multiple failure modes were in progress, and they differed mainly in how far they had progressed down their respective failure pathways.”
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.
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