A gold dredge in the river (or lake?), Oroville, California, ca.1930

Photograph of a gold dredge in the river (or lake?), Oroville, California, ca.1930. The gold dredging barge is about two stories tall. Machineries attached to the barge consist of a system of pulleys, conveyor belts and cables. Ladders provide access to the different levels of the barge. Piles of rocks cover the shores (at right).; "This district is in southwestern Butte County. It is mainly a dredging field that extends from just west of the city of Oroville southwest along the Feather River to a point about five miles due east of Biggs. The field is one to two miles wide and nine miles long. History. Shallow placers were mined here during the gold rush. The area was settled in 1849: Oroville originally was known as Ophir City, but the name was changed in 1855. Around 1895, W. P. Hammon and others tested the area to determine the feasibility of mining on a large scale. They introduced bucket-line dredging in 1898, the first in California. The field was highly productive from 1903 to 1916; in 1908 there were 35 dredges and 12 dredging companies active in the field. Output later declined, but dredging was done again from 1936 to 1942 and 1945 to 1952. The dredge field is now an important source of sand and gravel. The total Output from dredging is estimated to be about 1,964,000 ounces of gold." -- W.B. Clark.; "In certain cases, placer material is most economically excavated with a shore-mounted dragline or backhoe and a floating (barge-mounted) concentrating plant. (The digging equipment may also be mounted on a separate barge or on the same barge as the plant.) Material is dug from the sides and bottom of the mining pond and deposited into the washing plant's hopper. Oversized material is rejected by screening and placed in waste piles, while the undersized material is distributed to a gravity-separation system consisting of riffled sluices, jigs, or similar equipment. After treatment, as much waste as possible is returned to the pond, but, owing to swell, some waste may be deposited outside of the pond area. The pond moves along with the mining front. The backhoe technique has the advantages of powerful digging and good control." -- Encyclopedia Britannica.