WC134 JanFeb 2024 - Magazine - Page 21
At the time of the breach, according to Mount Polley
mine records filed with Environment Canada, pond
holdings included 177 tonnes of lead, 326 tonnes of
nickel, 18,400 tonnes of copper, and more than 400
tonnes of naturally occurring arsenic.
Dr. Philip N. Owens
and 6,500 sand, gravel, and stone quarries supply a multitude
of minerals and metals and related commodities which feed
the global supply chain for goods as disparate as automobiles,
construction materials, smartphones, and household appliances.
If any region might reasonably stake claim as embodying Canada’s mining wealth, the Cariboo in B.C.’s central Interior would
certainly qualify. With strong alkalic porphyry copper-gold mineralization formed more than 200 million years ago during the
Jurassic-Triassic period, the Cariboo has long proven magnetic
for fortune hunters. Artisanal miners frequented area stream
beds as early as the mid-nineteenth century, but an airborne
study in 1964 led to decidedly focused exploration and multiple companies staking claims. Northeast of the city of Williams
Lake, Mount Polley emerged as a mineral-bearing entity in 1997
when Vancouver-based IMI Imperial Metals initiated open-pit
extraction, and the operation expanded gradually, with underground facilities added in 2010.
By Imperial Metals’ own financial accounting, 2013 was
relatively stable, with revenues down just slightly from 2012,
weakened in part by softening gold and copper prices, exchange
rates and the timing and quantity of concentrate shipments. At
Mount Polley, one of several mines the company owns in B.C.,
copper production increased from 33.8 million pounds in 2012
to 38.5 million pounds in 2013 while gold declined from 52,236
ounces to 45,823 ounces.
WAT E R C A N A D A . N E T
Disaster strikes home
Imperial Metals expressed optimism for 2014, forecasting modest
gains for both commodities, as well as for silver—a much smaller
factor at Mount Polley. However, activity at the mine took an
abrupt turn midway through that year. On August 4, the dam
containing Mount Polley’s waste collapsed, dispatching 25 billion
litres of water, tailings, and associated materials into adjacent
waterways which serve as sources of drinking water for area
residents and major spawning grounds for sockeye salmon and
other species.
Tailings generally consist of crushed rock and other compounds left over from extraction and processing, and at Mount
Polley these were stored in an enormous pond designed to hold
the waste in a watery slurry and, by means of a dam and other
WATER C AN ADA • JANUARY/ FEBRUARY 2024
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