Meet the Toxic Sand Vacuum | The Dredge in Torch Lake, Michigan

Please Note: The text below is a modified transcript of the above video. For the best experience, I recommend watching and/or listening to the video if possible.

Hey, there! On my various filming trips around the Keweenaw Peninsula, I have repeatedly driven past this thing. It's a big, old, rusty... currently very creepy-looking piece of machinery sunk into Torch Lake, and the time finally came: I had to learn the story.

I wanted to know what this thing was, what it did, and how it got here — and as usual, the answers to those questions were way more interesting than what I was expecting! And this time, they were also just a little bit sobering.

So, here's what I learned.

So, what we're looking at here is officially called Quincy Dredge Number 2. The first time I heard about this thing, and the first time I saw it, I assumed that maybe it was built in — I dunno — the 1950s or '60s, somewhere around that time period?

Well, turns out, it was built in 1914. So... there is a 107-year-old rusty piece of equipment sitting in the lake.

The dredge was originally built for the Calumet and Hecla Mining Company, and then in the 1950s, it was sold over to the folks at the Quincy Mining Company. And both of those were huge copper mining organizations up in Michigan's Keweenaw Peninsula.

Regardless of who owned it and when, though, this behemoth had one main job: pull sand out of Torch Lake.

So, back in the day — let's call it the mid-to-late-1800s. So, back then, when rock was pulled out of a copper mine, it went through a few rounds of processing. The rock was broken into smaller and smaller pieces, and the goal was just to separate the rocks with a lot of copper from the rocks with little to no copper. Eventually, you reached a point where the rock with copper was sent off for more processing, and the rock with little to no copper... well, they just threw it away.

And by, uh, "threw it away," I mean they took it... and they threw it in the nearest body of water.

There's actually a huge history of copper mining in the Keweenaw, and that's something I'm planning to get into in a mini-series later, which is super exciting. But for now, this rock that they pulled out of the mines and crushed, and... threw into the lake... that stuff was called stamp sand.

The ruins of the Quincy Stamp Mill, where they used to make stamp sand.

Stamp sand can be different colors, depending on what kind of rock was crushed up to make it, but here, the stamp sand looks like this. It is this sort of, like, coarse, red, just... gravelly stuff.

Now, if taking a bunch of rock from a mine and throwing it into a lake sounds like a terrible idea for the environment... I mean, you are correct. This stamp sand might not have a phenomenal amount of copper in it, but it still does have other metals in it and just other... gunk... you really don't wanna be putting into a lake.

In fact, here, the situation was bad enough, and so much stamp sand was dumped into this body of water, that Torch Lake has been a Superfund Site with the Environmental Protection Agency for decades. It's a little bit lower on their priority list right now, but the key is that this place was extremely polluted for years.

Like, to give you a sense of the scale, there's this stat floating around online that says that at one point, 20% of the volume of Torch Lake was stamp sand. Now, that stat isn't quite right — according to some research from the 1990s, it's more like, um... 50%... of the volume of the lake was stamp sand.

These days, the lake is safe for recreation, but it's really not a phenomenal community for the plants and animals that are trying to live here.

That said, the environmental situation at Torch Lake is complicated, and there are, like, 200-page reports written on this. So on that note... this is a video about a dredge.

So, around the start of the 1910s or so, two things started happening in the Michigan copper mining world: The first thing was that people were still underground in the mineshafts digging for copper, but the return on investment was, like, kind of starting to go down. They really weren't finding as much copper as they wanted to.

And the second thing is that people were coming up with ways to process smaller and smaller amounts of copper — to pull metal out of what would've previously just been waste rock.

And eventually, these copper mining companies started putting two and two together. They looked around and went, "Huh. We have dumped literally millions of tons of stamp sand into Torch Lake. If we could take that sound and process it with these new methods... We could keep makin' that copper money."

And that is where the dredge comes in.

Quincy Dredge No. 1 (courtesy of the Michigan Tech Archives)

Now, early on in this video, I called this dredge Quincy Dredge Number 2. And there was a Quincy Dredge Number One. It just currently lives at the bottom of the lake. (That feels like foreshadowing somehow.)

When it comes to this dredge, Dredge Number Two, how it worked was actually pretty simple. The dredge had two pumps powered by two motors, and it juts sucked sand off the bottom of the lake. It passed the sand through a sort of, like, mesh filter just to get rid of any trash, and then the water was largely pumped off the sides of the dredge, and the sand was transported to shore via a pipeline floated on a bunch of pontoons.

The digging arm went 100 feet under the lake, and this thing could pull up 10,000 tons of sand per day.

Now, when it comes to actually getting the copper out of that sand… well, that’s where some clever engineering came in at reclamation plants.

The first thing that happened here is that the sand was put into ball mills. These were big, horizontal drums with a bunch of steel balls in them, and when they were turned on, everything spun around, and the steel balls ground up the sand into something with kind of the consistency of flour.

After that, the flour was sorted, and then the copper-containing flour was moved into another chamber.

Here, they mixed up the rock with a kind of salt called xanthate, and this is where I think it starts to get really cool. When they mixed everything up like this, one end of the xanthate molecule stuck to the copper. And then, this mixture was pumped into yet another chamber — and this chamber contained a foamy, bubble mixture of water and also pine oil.

So, you've got this copper, and you've got this xanthate molecule, but here's the thing: The xanthate tail is hydrophobic. In other words, it really doesn't want anything to do with water; it would much rather interact with some kind of oil instead.

You might see where this is going.

What happened in these chambers was that all of the xanthate tails gravitated toward the bubbles of pine oil. And then, when the bubbles rose to the surface, it dragged all of the xanthate, and dragged all of the copper up to the top of the tank. So at that point, all you had to do was skim the copper off the top of the mixture, and then send it off to be filtered and dried and eventually melted down into copper bars.

Besides the fact that this method is just so simple and so elegant and so clever, one thing that really gets me is that when people first started doing this, they didn't actually know why it worked — they just knew that it did.

As part of researching this video, I was reading this old paper from 1932, and it was just like, "Yeah. People know that copper flotation is effective, but um... nobody has really figured out the mechanism for why yet."

Even if they didn't know why it worked, though, this was still shockingly effective. I couldn't find a stat for how much copper the Quincy Mine was able to reclaim, but using a similar method, the Calumet and Hecla Mine — so, the original owners of the dredge — they were able to reclaim 423 million pounds of copper between, like, 1915 and the 1950s or so.

So as part of this story, Quincy Dredge Number Two was pretty effective and pretty helpful and pretty incredible... until it wasn't. In 1967, the dredge was chilling in the lake in the winter because it wasn't being used, and um, something happened, and it started to sink.

The problem is — I mean, at this point, it's 1967. Copper prices are pretty low, historically, the Quincy Mine is on its way out, and they didn't really feel the need to recover the dredge or... do anything with it, really.

In the end, they just opted to leave it in the lake. So today, there it sits, a thousand-ton tribute to the copper industry.

I mean, I'm not gonna say that I'm glad that there is a 107-year-old piece of rusty machinery in the lake, or that people dumped stamp sand into Torch Lake for decades. One thing I can say, though, is that even though parts of this story can be a little bit sobering at times, I thought this was super fascinating.