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From Wikipedia, the free encyclopedia
The Sumpter Valley Gold Dredge is a historic gold dredge located in Sumpter, Oregon, United States. The dredge is now listed as an Oregon State Heritage Area. The dredge was built during the gold rush that consumed most of the western states throughout the mid-19th century. Gold was discovered in Sumpter in 1862, but the advent of using a large machine to perform placer mining in Sumpter Valley did not occur until 1912. Three dredges were built between 1912 and 1934.
A gold dredge works by having large buckets that pull the gold-bearing earth up into its machinery to be processed, keeping the gold and spewing the waste (known as “tailings”) out the back by way of a stacker. Built on a shallow hull, these dredges did not need a lot of water to operate, as they moved their pond of water with them.
The internal mechanics were not very sophisticated—they duplicated, on a larger scale, many of the devices used by placer mining throughout the gold rush, such as the gold pan and the sluice box. In essence, the dirt that was dug by the large electrically powered buckets was sifted and sorted, and the remainder was washed over a series of riffles allowing the gold to settle and be trapped. The primary advantages that made the dredge more efficient than other methods were the volume of earth it could process and having its own water supply. The dredge that was built in Sumpter Valley could dig over 20 buckets per minute, consuming more than seven yards of earth each minute.
Three dredges worked the valley from 1913 to 1954, after placer and lode mining had become unprofitable. Sumpter No. 3 was built substantially from parts of the first dredge, which had been idle for 10 years. Between them, the dredges traveled more than 8 miles, extracting $10 to 12 million worth of gold. Still, it cost more to run than the gold could pay for. The last dredge closed in 1954, more than $100,000 in debt. In its lifetime this dredge made 4.5 million dollars at $35.00 per troy ounce. That’s 128,571.43 troy ounces which, compared to a more recent value of $1400.00 per ounce, would equal $180,000,002.00.