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A high-velocity jet stream is created within the jet tube producing a powerful vacuum. The dredge operates when a volume of water is pumped through a tapered orifice (jet), by a specially designed water pump. Running a Gold Dredging Operation in Alaskaįor a more complete understanding of this subject, we recommend you read any one of a variety of books and movies available through Amazon’s Gold Dredging Section. Normally, the smaller size dredges from two to three inches in size are equipped with single sluice boxes, as their primary function is portability and compactness. Another advantage of the surface dredge is it can easily be operated with or without diving equipment. The sluice box can either rest on the bank, or float on the surface of the water. The material is pumped to the surface through a suction hose into an efficient sluice box that is designed for recovering extremely fine particles of fine gold. The surface dredge floats on the surface of the water or sits on the nearby shore. Various sizes of suction dredges are used, varying from those “recreational” models with a small 11⁄2 inch intake hose to large, heavy dredges with 8-inch and 10-inch intake hoses, driven by powerful engines, and capable of processing large amounts of material in a single day. Suction dredging is a popular form of recovering gold from the numerous placer streams in Alaska. Today most dredging is done with surface suction dredges either operated from shore or on a small boat. You can see the piles of gravel from these early mining operations still today around Fairbanks and Dawson City. The buckets scoop up the gravel and dump it into sluice boxes inside the floating dredge, water is then pumped in to separate the gold from the gravel, and the worthless gravel is then dumped out the back. Although they seem complex, their concept is quite simple. Many changes and additions were made to make them suitable for working on the frozen ground of Alaska, but the technology changed little for the 80 years they were in use. The bucket-line dredges that changed the character of gold mining in Alaska and the Yukon were invented in New Zealand.