I was trying to work out why they needed dredges and buckets for placer mining. Apparently it goes like this.
Alaska Gold Company's gold placer mining operation is located near Nome, Alaska.
Placer gold consists of gold particles concentrated in sand, gravel, or other detrital material.
The gold has been eroded from the land mass by the sea, redistributed by surf action in beach deposits, and then covered by later deposits of gravel, sand, and clay. These gravel deposits are permanently frozen and rest on limestone bedrock.
The frozen gravel must be thawed prior to dredging. This is accomplished by forcing water into the ground through pipes that extend to the bedrock. Thawing precedes dredging operations by at least one year so that an adequate quantity of gravel is available for dredging at all times.
The gold is mined by floating dredges. Buckets attached to a continuous belt scoop the gold-bearing gravel and carry it upward at the bow end of the dredge. The gravel is then dumped into a hopper from which it passes through a screen. Waste gravel is discharged from the stern by a conveyor belt on to a barge that collects waste gravel for sale. The gold travels through the screen and is then recovered by a mercury amalgam in riffled sluices. The amalgam is later heated to separate the gold from the mercury. The gold is then shipped to a refiner who further processes it to remove impurities and returns it to the company.