WC137 JulyAug 2024 - Magazine - Page 28
MINING
The Aftermath of a Closed Mine
There are often challenges and disagreements, including
what to do with tailings and other mining wastes that can
potentially affect water systems, when a mine closes.
O
Saul
Chernos
is a freelance
writer for Water
Canada.
28
NE MIGHT EXPECT a mine’s closure to
mark the end of its storyline. The final chapter
to exploration and discovery, development,
and production and, given the finite nature of
resources and finances, the proverbial curtain
call. However, even as production winds down, there’s
a postscript: the site’s aftermath. With environmental
awareness and oversight increasing, extractors face fundamental, often challenging questions about what to
do with leftover residues and other waste. Closed and
abandoned mines can be epic sagas in the truest sense
because reclamation and monitoring can, in worst-case
scenarios, linger in perpetuity.
In principle, the goals of remediating and reclaiming shuttered mine sites aren’t too different from
dealing with old or abandoned industrial properties.
Charles Dumaresq, vice-president of science and environmental management with the Mining Association
of Canada, said the idea is to return mine sites to a
natural state and manage risks to the extent possible.
“A lot depends on the kind of mine,” said Dumaresq. “But typically, the infrastructure associated with
mining and ore processing is going to be removed. A
lot of the equipment will be sold. They’ll demolish the
buildings and do remediation around the site where
the ore processing facility was. Things like that.”
While it’s straightforward enough to renew areas
occupied by buildings, remediating and reclaiming
areas where mining has occurred is more complex.
Once equipment has been removed from an underground operation, crews let the mine flood naturally,
understanding that the water will keep oxygen from
interacting with exposed minerals and metals and
thus prevent any harmful content, if it exists, from
leaching into the surrounding environment. Openpit mines also collect water, and work is sometimes
done to reengineer these as small, functioning
ponds and lakes. “Some good examples include the
diamond mines in the Northwest Territories,” said
Dumaresq, describing small, newly constructed shal-
WATER C AN ADA • JULY/AUGUS T 2024
low-water habitats, complete with shoals, that will
eventually accommodate fish.
Still, there are challenges and disagreements,
including what to do with tailings and other mining
wastes that might potentially affect water systems,
wildlife, and people living nearby. Much of what’s
done depends on the materials involved.
“Surveillance, monitoring, and maintenance could
go on for years, decades, even in perpetuity, depending on the risk profile of the tailings facility,” said
Dumaresq. “Some sites will need decades worth of
continued water treatment. Other sites will develop
a soil cover and begin to revegetate the tailings. If
there’s no chemical risk and the tailings facility is
physically stable, it can eventually be in a position
where very little maintenance or surveillance is
required.”
The Mount Polley copper, gold, and silver mine
in central British Columbia (Water Canada, “10
Years Later,” January/February 2024,) illustrates the
potential complexities of containing wastes in situ,
albeit in this case ostensibly nestled at the bottom of
a very deep lake. In many respects, Mount Polley is
an extreme and atypical example because the mine
was in full production when the dam of its outdoor
tailings pond failed in 2014, dispatching a slurry containing copper, nickel, lead, and arsenic into adjacent
waterways leading to Quesnel Lake. Mount Polley
Mining Corporation (MPMC) has since repaired
the tailings facility, resumed extraction and, with
regulatory approval, now discharges treated wastewater into Quesnel Lake through a pipe and diffuser.
However, the presence of the original spilled tailings
and the current use of the lake to accommodate newly treated mine wastewater have faced scrutiny, with
area residents reporting algae blooms and an overall
deterioration in water quality. Even though the lake
water meets Canadian drinking water standards,
many residents are opting for bottled water because
they simply don’t trust the lake’s potability.
WAT E R C A N A D A . N E T
Getty Images
BY SAUL CHERNOS
