The “clean-up” represents the culmination of months, and even years, of work to extract gold from the frozen Yukon muck. The most highly organized of them all were those aboard the dredges of the Yukon Consolidated Gold Corporation, or YCGC.
I met John King the summer of 1993. John had once been the superintendent of the Gold Room at Bear Creek, the headquarters of the YCGC, which was the large dredging company mining in the Klondike.
John had a remarkable recall of his work, which included regularly cleaning up the gold on the company’s fleet of dredges, and refining it into ingots for export. During a series of conversations with him, and from material that he subsequently sent to me, it was possible to obtain a picture of how a dredge clean-up was undertaken.
The bucket line on a dredge consisted of a continuous chain of steel buckets that cut into the gravels and carried the material into the processing plant inside the 5,000 tonne machine. On Dredge No. 4, each of these buckets could hold a half cubic metre, or 800 kilograms, of gravel.
Over 17 tonnes of material were excavated each minute. That’s the amount of gravel that could be handled by three men in an entire day! The material dredged in a single day could amount to 24,000 tonnes, or the hand work of 4,320 men.
The gravel was dumped into a hopper and washed onto a gigantic sloped rotating drum called a trommel, with more than 22,000 litres of water per minute. That is the equivalent of flushing a toilet 1,000 times.
The agitation of the revolving drum, combined with the huge volume of water, washed the gravel clean. The cleaned rocks were then dumped on a conveyor belt at the lower end of the trommel, carried up the “stacker” and deposited away from the dredge.
The gold-bearing material that was washed from the rocks and boulders fell through circular holes drilled in the rotating drum and into a bin below it called a distributor. From the distributor, this material was washed over a series of sloping sluice tables on either side of the trommel.
The gold, being 19 times heavier than water, quickly settled out and most of it was captured in the first two metres of the sluice run, which consisted of sheets of expanded metal riffles locked in place over coconut matting, beneath which lay a sheet of canvas cloth. Farther down the sluice run were “Hungarian” riffles made of angle iron, and farther yet, were much larger wooden riffles covered with strips of rubber.
By the time the silt and fine gravel had washed over these various riffles, most of the gold had been captured.
Once a week, two men from the Gold Room would arrive at the dredge, which was shut down for the purpose of the clean-up. One dredge was processed in the morning and another in the afternoon.
These men would enter the sluice tables, which were screened in and locked at all times. The regular clean-ups focussed on the portions of the sluice system where most of the gold was captured. The clean-up crew removed the expanded metal riffles at the upper end of the uppermost sluices, and any riffles below these, where gold was visible.
Coconut mats were removed from under expanded metal riffles in the bottom of the sluice boxes, along with the piece of canvas that underlay each mat. In Dredge No. 4, the mats in the first seven sluice runs of the sluice table were removed.
Each mat was folded by bringing the four corners together, and the canvas beneath was wrapped around it to ensure that no gold would fall out, and they were moved to large “clean-up boxes,” located on each side of the main deck below the sluice tables.
New mats and riffles were immediately laid down in the sluices. The mats were covered with expanded metal screens and locked in place so that the dredge could start digging again. In the seasonal dredging operations of the Klondike region, down time was kept to a minimum.
Meanwhile, the Gold Room team placed the mats in the “clean-up boxes” on the main deck, which were filled with water. The mats were thoroughly washed, flipped up and down and turned over several times to remove everything trapped in them.
The water was drained from the “clean-up box,” over another small sluice, or “long tom,” to recover any stray gold. This sluice was only 35 centimetres wide, and held two coconut mats, wire screen, and ten little riffles. The material washed out of the mats was scraped into one of the upper corners of the “clean-up box.”
Using a serrated, long-handled scraper, one of the team worked this material as it was flushed with water. More sand and other particulates were washed out of the gold, until all that remained was a concentrated mixture of gold and black sand. This material was scooped up and placed into a cylindrical metal canister which was then padlocked. For security, a numbered metal seal was affixed to the hasp.
The mats in the long tom were also packaged up and taken, along with the canister, to the Gold Room at Bear Creek for processing. From the 168,000 tonnes of material that was excavated every week, the residue of gold could be carried off the dredge in one or two canisters.
Every second week, the dredge would be brought to a halt for a general clean-up. This would last for an entire morning. The four-man dredge crew assisted for this clean-up, during which all the coconut mats and metal riffles in the upper part of the sluice runs were taken up.
The material that had been captured in the distributor was siphoned off through pipes at the bottom that fed into a third “clean-up box” positioned directly beneath the trommel on the main deck. Gravel was also cleaned out of a sluice run placed under the hopper into which the bucket line dumped its payload. This sluice was known as the “save-all.”
All the material from the riffles was washed out in the same manner, and the concentrate from this cleanup was placed in sacks and taken to Bear Creek. Material from the different parts of the dredge, the “save-all,” the distributor and the sluice table was marked and kept separate so that statistics could be kept for the recovery from all the different parts of the system.
Once a month, during a “total clean-up,” all the metal and wooden riffles on the sluice tables were removed. The material trapped beneath was shovelled into canvas bags and taken to the Gold Room.
There, all the planning, ground preparation, power distribution, preparatory work and dredgery was reduced to a collection of heavy gold ingots, so small by comparison with all of the material moved and processed leading up to this moment.
Michael Gates is a Yukon historian and sometimes adventurer based in Whitehorse. His latest book, Dalton’s Gold Rush Trail, is available in Yukon stores. You can contact him
at msgates@northwestel.net