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McLaughlin Natural Reserve

LAND USE - THE GOLD MINE

 

Homestake Mining Company is a San Francisco-based company that specializes in gold. It was founded in 1877 by George Hearst to exploit a rich discovery in Lead, South Dakota. In 1927, the company's fortunes were faltering badly until a young Harvard- and Berkeley-trained geologist, Donald McLaughlin, persuaded the company to investigate a new lode at its Lead mine. His risky prediction proved successful, and McLaughlin became company president in 1944; later he became Professor and Dean of Engineering at UC Berkeley and served as a UC Regent. The company now operates in Canada, Argentina, Australia and elsewhere. In 1985, the year of McLaughlin's death, the company named its new Napa-Yolo-Lake County mine in his honor. The reserve takes its name from him and his wife Sylvia, a philanthropist and activist.

Hot springs gold deposits are often very low in concentration; the McLaughlin ore body averaged only 0.10 ounce per ton of ore. However, during the 1970's, two factors increased the feasibility of mining such deposits: advances in technology, such as earth moving equipment and cyanide-based processing, and President Nixon's termination of the convertibility of dollars into gold, which sent the price to over $700 an ounce. James Anderson, head of explorations at Homestake, began exploring possibilities in the hot springs deposits of Napa and Lake counties. He persuaded geologist Donald Gustafson to conduct preliminary testing near Knoxville and Wilbur Hot Springs. Eventually, 55 miles of exploration holes were drilled in the Knoxville area. (As Anderson told interviewer Eleanor Swent) "My whole view of the world was economic discovery, not just discovery of something you couldn't do anything with, and the whole thing was geared on a risk/reward ratio. I was convinced that I could find economic mines."

Even after deciding to proceed with the new project, Homestake spent five years and $285 million before gold extraction began. Land was acquired, environmental surveys were performed, and a new public road was constructed from Lower Lake to the mine. A grand total of 327 permits were required from the three counties, three regional air quality districts, and regional and state water districts affected by the mine. At the ribbon-cutting ceremony, these permits were piled together in a tower of paper eight feet high.

Opposition to the mine was raised by a group of farmers from the Capay Valley in Yolo County, led by UC Davis English professor turned almond farmer Will Baker. They worried that the creation of Davis Creek Reservoir, by flooding the site of the old Reid mine, would increase mercury contamination in Cache Creek. They were also concerned that blasting in the pit would send dust and asbestos particles into the air and harm crops and health. They argued that the proposed mine violated the Williamson Act, under which the land had been set aside for agriculture and open space in return for tax breaks; Homestake was granted a controversial exemption from this act.

The Capay farmers were unable to prevent the mine, but their opposition had lasting effects. (As Baker told Eleanor Swent) "Someday some historian is ... going to look through that and they're going to say, Well, not everybody signed on to this thing; here's a couple of wackos off here saying, Wait a minute, you guys. Do we have to have every gold mine? ... Of course the bulldozers are going to run over them, but at some point the historian will say, Well, there was some opposition." To win approval for its plans, Homestake agreed to employ the most progressive design ever used at a gold mine.

In its permit applications, Homestake spelled out a massive program for the reclamation of disturbed areas. The company also agreed to clean up contamination from the previous century of mercury mining, and to monitor air quality, water quality, wildlife, rare plants, aquatic ecology and revegetated areas. The company continues to submit annual environmental monitoring reports covering all of these activities. Finally, the company reassured local residents by promising that after it closed, the mine site would become a field station for environmental studies, rather than an abandoned wasteland like most closed mines. Much of this environmental package was designed by a former Sonoma County planner, Raymond Krauss, who was the mine's environmental manager from 1982 until 1998.

Manhattan Mine

Mine Loader with sight-seeing reserve staff, 2003.

The design of the mine itself is unusually environmentally sound in several ways. The waste rock ("overburden") lying above the ore body was placed on impermeable bedrock, to trap the acidic waters that are created when sulfur-rich rock is exposed to air and water. This acid mine drainage is captured in settling ponds at the base of the piles, and disposed by pumping into the pit. The rock piles were covered with topsoil and revegetated. The ore is crushed in the grinding mill near the pit, mixed into a slurry using water from Davis Creek Resevoir, and piped 8 km to the processing mill. The processing mill was placed in this distant location because the small valley formerly called Quarry Valley had impermeable bedrock. At the processing mill, gold is recovered in a contained, aqueous cyanide process. Until 1997, autoclaves the size of train cars were used in a high pressure oxidation process designed to immobilize heavy metals, eliminate acid formation and reduce the concentration of cyanide in the tailings. Cyanide degrades rapidly, and in 15 years of weekly monitoring, no dead wildlife have been found in or around the tailings pond.

Mining in the open pit ceased in 1997, as did the use of the expensive autoclaves, and the work force dropped from 350 to 100. The mill will continue to process the stockpiled ore until 2002, and reclamation of the disturbed areas will also continue. The 200 meter (640 foot) deep open pit will remain, but its sides will be smoothed and revegetated. After 2002, the company will tear down and remove the processing mill and nearly all of the buildings.

Before the McLaughlin mine, nearby Lower Lake was one of the most economically depressed towns in California. The arrival of the mine changed the area significantly as Homestake provided jobs and donated money for new schools, hospitals and a community college. The impending closure of the mine will slow the economy of Lower Lake, and Morgan Valley will revert to being a quieter place, though its new roads, phones and electricity will remain.