Dredging Up A Dredge In The Yukon
When we embarked on what was possibly a harebrained, 406 km-long vacation canoe trip along the Yukon River in Northern Canada, I wasn’t particularly expecting to encounter a conservation site.
I was wrong: Our final destination on the Yukon River was Dawson City, the site of the Klondike gold rush in 1896. By 1898 the city had swelled to 40,000 people. Now there are now about 1000 inhabitants left and many abandoned turn-of-the-century buildings still left to restore.
But actually the most impressive conservation site was that of Dredge No. 4, a lackluster name for a colossal machine built in 1912 to sift gold out of the gravel, using the same principle as the folks who panned for the precious metal in streams–albeit at a rather larger scale.
The monster Dredge No. 4 is 8 stories high and 2/3 the area of a football field.
Since gold is 19 times heavier than water, the easiest way to separate gold from gravel is to dig up some ground, put it in a bowl of any size, shake everything back and forth in water and wait for the gold to sink to the very bottom of the wet mixture by means of gravity. Then you pour off the water and swipe off the top layer of gravel and presto there’s your gold nugget at the bottom of the bowl (or in my case, a single, barely visible flake of gold that garnered a rather sympathetic look from the teacher when I took a brief gold panning course).
Anyway, Dredge No. 4 was built on a creek, in whose water it would shake around the gravel the dredge had picked up in a rotating series of 450 liter buckets (120 gallon). The design effectively allowed the dredge to dig some 17 meters below water level, sift through the gold and gravel before moving forward along the creek to dig up some more.
The leftover gravel and water then got shunted out the back. As you can image, the Yukon’s pristine outdoors didn’t fare as well* as the dredge owners, who raked in as much as 800 ounces of gold in a single day. (At today’s gold price, that would amount to pulling $1.36 million dollars of gold in a day.)
According my Parks Canada handout, it was “the largest wooden hull, bucket-line dredge in North America.” That’s probably why the Canadian government eventually decided it was a cultural artifact worth preserving. Especially since the dredge, after retiring in 1959, began sinking deeper into the creek until it eventually got frozen there.
In the early 1990s the dredge was initially excavated, refloated and relocated to higher ground in order to protect it. According to the Parks Canada staff, there are now plans afoot to restore the interior, which is an absolutely amazing example of mega machinery.
I’m not much of an engineering freak, but I seriously nerded-out on the gigantic rusty gears and pulleys inside. So, if you end up in Dawson City, Yukon, with some hours to burn, make sure you check out Dredge No. 4.
*Although this kind of gold mining–called placer mining–does churn up alot of ground, it only requires gravity to extract gold. Current Canadian regulations require placer miners to replace the gravel they churn up and cover it with topsoil so regrowth can occur.
Many consider placer mining to be less environmentally problematic than hard rock gold mining which requires cyanine and mercury to remove gold from hard quartz rock. With the skyrocketing gold prices, several mining companies are trying to set up hard rock mines in the Yukon, since much of the gold easily available from placer mining has already been scooped up.