WEBVTT
Kind: captions
Language: en

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- This is Giant Mine
in the Northwest Territories of Canada.

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There are kilometres of tunnels
under this rock,

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and chambers the size of city blocks
that have been hollowed out.

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In the 20th century, more
than 200,000 tonnes of gold

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were extracted from the
rock underneath here.

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At current prices, that is somewhere north
of US $8 billion worth of gold.

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There is a problem, though.

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That mining also created
more than 200,000 tonnes

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of toxic arsenic trioxide dust.

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That's enough to kill everyone
on Earth several times over.

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Over the decades, the vast
majority of it was stored

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in the empty, abandoned chambers
left behind after mining,

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although some of it did get
out into the environment.

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The mine closed in 2004.

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When the gold ran out, the
mining company went bankrupt

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and left the mess for the
government to clean up.

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Arsenic trioxide has no scent, no taste,
and it dissolves in water.

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Oh, and we're right next to Yellowknife,
the capital of the Northwest Territories,

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and next to the 10th
largest lake in the world.

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- There's 237,000 tonnes
of arsenic trioxide,

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and they're currently stored
in 14 underground chambers.

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The plan is to freeze the chambers.

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We're freezing the rock
around the arsenic.

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See, arsenic trioxide is a fine powder.

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So it will form a shell.

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And eventually, it will freeze in
and it will become a block over time.

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And that prevents water from
getting in and getting out

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and keeps the arsenic trioxide contained.

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So each chamber, of course,
is differently shaped.

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Some are regular shaped.

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Some are very rectangular shaped.

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So we want to freeze 10 metres
beyond all boundaries of the chambers,

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both on the horizontal
and the vertical.

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We're going to freeze
at least to -5°C.

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The way we're going to
freeze it, we're going to use

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a technology called
thermosiphon technology,

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and it's basically a technology that uses

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the ambient air temperature, the cold air,

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using a long tube filed
with carbon dioxide.

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The carbon dioxide, when it's a gas,
it rises up to the top of the tube.

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And then if the air outside is colder,

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it will dissipate its heat,
turn to a liquid,

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and with gravity, will drop back
down to the bottom of the tube.

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And there, it can warm up, take
the heat out of the ground,

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and it just continually cycles,
extracting heat from the ground.

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Since we're in Yellowknife,
north of 60° latitude,

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it's colder above ground
than it is below ground

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for the majority of the year.

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- Freezing the arsenic
doesn't make it less toxic,

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but it does make it
impossible for any water

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to seep in and then carry the arsenic out.

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And that was the mining
company's original solution

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using the natural permafrost here.

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And it might have worked, if they
hadn't mined the rock above it,

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exposed the permafrost
layer to the elements,

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and started to melt it.

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Freezing should work,

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but there are skeptics,
and they do have a point.

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Freezing requires constant upkeep.

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This dust is arguably worse
than radioactive waste.

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There is no half-life here.
It won't decay over time.

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The dust will be just as deadly
in 10,000, 100,000 or a million years.

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- So right now, there's
nothing on the horizon.

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The freezing was deemed the best
technology for the arsenic trioxide.

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So we will be funding
research indefinitely

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until a different solution arises.

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We have frozen one of the chambers.

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We did what we call a
freeze optimization study.

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We chose one of the chambers.
We installed the thermosiphons,

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but we also installed some
freezing pipes filled with glycol

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to do what we call an active freeze,

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which will be very
similar to a hockey rink.

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So based on that study, we
determined that we could use

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the passive technology, which
is just the thermosiphons

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with the carbon dioxide.

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It just wasn't quite as fast,
so it's gonna take a little bit longer,

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but the trade-offs are such
that we don't need to use power

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and it's a lower maintenance
over the longer term.

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So the remaining chambers will be frozen
when we start the remediation project.

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It could be as early as summer of 2020,

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but more optimistically, 2021.

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Our last estimate for
the cost of the project

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was 934 million, including
the care and maintenance phase

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that we're in right now,
remediation that we'll go into

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in a few years, and then the
long term care and maintenance.

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This project has gotten
approval for 100 years.

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- These days, countries
in the developed world

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have regulations that
mean mining companies

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shouldn't be able to do this.

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We have environmental impact
studies and long-term plans,

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and we have public scrutiny
of pretty much everything.

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But we still have to fix
the mistakes of the past

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and make sure that
today's mining companies

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can't just walk away from their legacies.

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Thanks to everyone at the
Giant Mine Remediation Project.

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Pull down the description
for links about them

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and about some of the history
that I couldn't fit into this video.