Hydraulic mining
Encyclopedia : H : HY : HYD : Hydraulic mining
Hydraulic mining, or hydraulicking, is a form of mining that employs water under pressure to dislodge rock material or move sediment. This form of mining was used in the region around Nevada City, California, c. 1853 to exploit gold-bearing upland paleogravels. Previously hydraulicking had been invented by the Romans to find gold using high-pressure water jets from a tank situated from 400-800 feet above the ground. In contrast, ground sluicing, which uses water at atmospheric pressures under the force of gravity alone, has been utilized for more than a thousand years.
In California, hydraulic mining often applied water under very high pressures developed by bringing water from high Sierra locations for long distances along ridge crests to holding ponds several hundred feet above the surface to be mined. Insofar as California hydraulic mining exploited primarily river gravels, it was one form of placer mining; that is, working of alluvium (river sediments).
Process
Early placer miners in California discovered that the more earth they could process, the more gold they were likely to find. Instead of working with pans, sluice boxes, long toms, and rockers, miners collaborated to find ways to process larger quantities of earth more rapidly. Hydraulic mining became the largest-scale, and most devastating, form of placer mining. Water was redirected into an ever-narrowing channel, through a large canvas hose, and out a giant iron nozzle, or monitor. The extremely high pressure stream was used to wash entire hillsides through enormous sluices. By the early 1860s, while hydraulic mining was at its height, small-scale placer mining was a thing of the past. The vast majority of lone prospectors could not sustain themselves, and the mining industry was taken over by large companies, most of which found hard rock gold mining (or quartz mining) more profitable. By the mid-1880s, it is estimated that 11 million ounces of gold (worth approximately US$7.5 billion at mid-2006 prices) had been recovered by hydraulic mining in the California Gold Rush.Environmental effects
While generating millions of dollars in tax revenues for the state and supporting a large population of miners in the mountains, hydraulic mining had a devastating effect on riparian environments and agricultural systems in California. Millions of tons of earth and water were delivered to mountain streams that fed rivers flowing into the Sacramento Valley. Once the rivers reached the relatively flat valley, the water slowed, the rivers widened, and the sediment was deposited in the floodplains and river beds causing them to rise, shift to new channels, and overflow their banks, causing major flooding, especially during the periods of Spring runoff.Cities and towns in the Sacramento Valley experienced an increasing number of devastating floods, while the rising riverbeds made navigation on the rivers increasingly difficult. Perhaps no other city experienced the boon and the bane of gold mining, as did Marysville. Situated at the confluence of the Yuba and Feather rivers, Marysville was the final "jumping off" point for miners heading to the foothills to seek their fortune. Steamboats from San Francisco, carrying miners and supplies, navigated up the Sacramento River, then the Feather River to Marysville where they would unload their passengers and cargo. Marysville eventually constructed a complex levee system to protect the city from floods and sediment. Hydraulic mining greatly excerbated the problem of flooding in Marysville and shoaled the waters of the Feather River so severely that few steamboats could navigate from Sacramento to the Marysville docks.
Legal ramifications
Vast areas of farmland in the Sacremento Valley were deeply buried by the mining sediment. Frequently devastated by flood waters, farmers demanded an end to hydraulic mining. In the most renown legal fight of farmers against miners, the farmers sued the hydraulic mining operations and the landmark case of Edwards Woodruff v. North Bloomfield Gravel Mining Company made its way to the United States District Court in San Francisco where Judge Lorenzo Sawyer decided in favor of the farmers in 1884, declaring that hydraulic mining was “a public and private nuisance” and enjoining its operation in areas tributary to navigable streams and rivers. Hydraulic mining was recommenced after 1893 when Congress passed the Camminetti Act which allowed such mining if sediment detention structures were constructed. This led to a number of operations above brush dams and log crib dams. Most of the water-delivery infrastructure had been destroyed by an 1891 flood, so this later stage of mining was carried on at a much smaller scale in California.Beyond California
Although often associated with California due to its adoption and widespread use there, the technology was exported widely to Alaska, Montana, the southeastern USA, British Columbia (Canada), and overseas. For example, it was employed in extensively in Dahlonega, Georgia and continues to be used in developing nations, often with devastating environmental consequences.References
- Hydraulic Mining in California: A Tarnished Legacy, by Powell Greenland, 2001
- Battling the Inland Sea: American Political Culture, Public Policy, and the Sacramento Valley: 1850-1986., U.Calif Press; 395pp.
- Gold vs. Grain: The Hydraulic Mining Controversy in California's Sacramento Valley, by Robert L. Kelley, 1959
External links
- [Hydraulic Gold Mining in California's Sierra Nevada Mountains (at the Central Pacific Railroad Photographic History Museum)]
- [The Evolution of Gold Mining]
From Wikipedia, the Free Encyclopedia. Original article here. Support Wikipedia by contributing or donating.
All text is available under the terms of the GNU Free Documentation License See Wikipedia Copyrights for details.