MERCURY WARS
Hydraulic mine operations, French Corral MD, Nevada Co. CA. Source: Nevada County Historical Society.
from large reservoirs through hundreds of miles of ditches, flumes and canals to each mining operation.
While it has been argued that 19th century mine operators were not aware of the environmental consequences of their activities, historical evidence proves otherwise. For example, at Foresthill Divide the owner of one hydraulic mine admit- ted in a letter that “if the local farmers could see the turbid conditions on the Middle Fork of the American River that we are creating from discharge of hydraulic mine tailings into the river they would be furious.”
Judge Lorenzo Sawyer’s Decision of 1884 ended traditional hydraulic mining and caused the California legislature to enact the nation’s first environmental law. Its purpose was to prevent further environmental devastation along five rivers and their associated watersheds—namely the Feather, Yuba, Bear, American and Consumnes river systems.
Initially, few mine owners complied with the newly imposed regulations. Hydraulic mining operations were frequently conducted during the winter season, when water was plentiful and the streams naturally carried more siltation. This made compliance inspection by state monitors more problematic. During the summer and fall seasons some owners chose to conduct outlawed activities at night to allow more time for the turbid water discharged into local streams and rivers to clear up.
In response to the 1884 Sawyer decision, mine owners formed a formidable group known as the Hydraulic Miners Association, which eventually succeeded in getting hydraulic mining reinstated nine years later. The Caminetti Act of 1893 was a political compromise that authorized construc- tion of dams designed to retain hydraulic mine tailings. The California Debris Commission was formed to monitor hydrau- lic mine operations and mine tailings, and each mine operator was charged a fee for tailings storage.
For various reasons such dams failed to solve the problem and their reservoirs ended up being entirely used for water storage and recreational purposes. Most notable of these dams and associated reservoirs are Englebright and the Bullards Bar Dam on the Yuba River, and the Combie and Camp Far West Dams on the Bear River. The administrative duties of
Hydraulic mine. Sluicebox gold recovery system. Photo depicts sluicebox with “undercurrent” design. Historic sluicebox systems discharged significant amount of mine tailings into streams and rivers on a daily basis. Source: CA State Library.
the California Debris Commission were later taken over by the federal Army Corps of Engineers.
Over the last 15 years, an interdisciplinary, interagency team headed by the U.S. Geological Survey (USGS) has been evaluating the effects of hydraulic mining and mercury con- tamination on the environment in the Northern Sierra Nevada region. The net results of these careful scientific investigations, has been the documentation of numerous adverse environ- mental impacts caused by mercury contamination, both to Sierra watersheds and downstream, into the San Francisco Bay-Delta environments.
The investigation reveals that the real culprits, which had gone largely unnoticed were sulfate-reducing bacteria that are nearly invisible to the naked eye. These ancient bacteria can digest metallic elements and compounds. This taxonomic group of bacteria is thought to have evolved soon after the Earth was formed nearly 4.6 billion years ago. Sulfate- reducing bacteria require no oxygen and presently thrive in environments that are anaerobic (devoid of oxygen). They are thought to have been instrumental in producing the Earth’s oxygen-rich atmosphere by metabolization of sulfate-rich rocks.
In the Sierra Nevada region, colonies have been found living in sluice tunnels and blocked pit lakes, and in the river-bottom sediments of streams, rivers, and reservoirs. The bacterial colonies convert inorganic elemental mercury to an organic form called methyl mercury, that is soluble in water and easily accumulates in the living tissues of all organisms in the food chain. This process is called biomagnification. Top predators in the aquatic and terrestrial food chain are adversely affected, including fish, birds and humans.
Since mercury is classified as a neurotoxin, pregnant women, fetuses, women of child-bearing age and children under six years of age are thought to be most at risk when consuming certain species of fish that dwell in the Sierra-Bay Delta region.
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