| The transportable suction dredge, like the power sluice, has revolutionized gold prospecting for the small time prospector. Dredging has been used for quite some time, but only recently have dredges been made small enough to be transportable by the prospecting community. Using a suction dredge, prospectors can remove materials from once unobtainable locations, such as the material directly on (and under) the bottom of a river. There are three basic types of dredges: Surface, Submersible, and Lift. I'm only going to write about the surface dredge as it remains the most popular among gold prospectors. |  |
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What is a suction dredge? A suction dredge "sucks" materials from the river bottom using a suction system. Materials are then deposited onto a sluice, pushed down the sluice by the flow of water, and exit out the "output" end of the sluice box. A prospector using a surface suction dredge is practically vacuuming underwater. |
| What is a surface dredge? A surface dredge is a dredge that floats on the surface of water. Pontoons (floats) keep the sluice box and engine/pump combination on the surface. Materials are then pumped (or "sucked") to the surface in large suction hose. The materials and the accompanying water exit the hose and enter the sluice box system. The dredge sluice operates similiar to that of the hand sluice and the power sluice (box with riffles and matting). The sluice derives its gold-grabbing ability by using the flow of water and the currents established by the riffles. |
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Not all surface dredging occurs under water. In many places, prospectors dredge the shallow portions of a river and can rest their dredge on the bank, a sand bar, or in shallow water. This is an effective method when gathering materials on or near exposed bedrock entering the river. Many times, exposed bedrock creates natural riffles in the river, thus trapping heavy materials close to the surface. |
| Sizes of Surface Dredges There are many different sizes of surface dredges available to the prospector. Most manufacturers rate their dredges by the inner diameter suction hose tip (in inches) and the powerplant (in horsepower). One person can operate 2" dredges all the way up to a 5" dredge. Some prospectors prefer to use two people when dredging (one for safety) and recommend that you have a safety person when diving with any sized dredge. Six inch dredges and larger typically require two people as they are more difficult to maneuver due to their size and weight. |
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I spoke with one dredge manufacturer at length on the phone, and this particular company tests their dredge capacity using concrete mix with no rocks. They said for accurate "in river" estimates, take their listed capacity and cut it in half (and that would be a "best case" scenario): 2" Dredge, up to 2 yards p/hour 2 1/2" Dredge, up to 5 yards p/hour 3" Dredge, up to 8 yards p/hour 4" Dredge, up to 12 yards p/hour 5" Dredge, up to 15 yards p/hour 6" Dredge, up to 20 yards p/hour 8" Dredge, up to 25 yards p/hour |
| As listed above, surface dredges come in many sizes and capacities. Advances in technology have made even the smallest dredge quite potent. One of the largest areas of concern for the individual prospector looking to purchase a dredge is NOT how much dredge can one handle, it's actually based on the location he/she will be dredging. Can you drive right up to the river? Will you be requierd to "pack-in" your dredge over a considerable distance? I have a 5" Dredge that weighs over 400 lbs assembled. Even though the dredge can be easily taken apart, moving the dredge around out of water is NO JOKE. Once it's in the water, it stays in the water. Of course, if you are not alone, you can tackle moving a dredge more easily. |  |
