Yukon Geological Survey publication metadata (English, HTML)

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Publisher-reported update

2026-08-26

This report is an account of our work testing the viability of floater dredging for placer gold in permafrost. Floater dredging is a method of mining which uses a hydraulic excavator to feed placer gravel to a floating gravel processing plant. We wanted to see if the digging face of a dredge pond dug in permafrost would thaw fast enough to supply gravel for a production-scale mining operation. We stripped the vegetation and muck from an area on a permafrost terrace above the Fortymile River. We dug a pit in the stripped area and pumped it full of water to form a pond in which to operate our floater dredge. Water from the pond seeped into the surrounding gravel, thawing as it penetrated. We confirmed that when frozen gravel is exposed to water, it thaws faster than when exposed to air. We experimented with various methods of accelerating the rate of thaw at the dredging cut face. We found that sloping the cut face at 30° to the vertical exposed more surface area to the thawing action of the water, without sacrificing digging efficiency of the excavator. We found that equipping the excavator with spade-type abrasion teeth gave the best combination of penetration, digging…

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