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The Kennedy Mine was one of the large-scale gold mines that worked the “Mother Lode” deposits in the Sierra foothills of Northern California. It’s a kilometer and a half north of Jackson, off of Highway 49 that links many of the historic towns and ruins from the 19th century gold rush era.
First developed in 1860, the mine’s successful commercial operation ran from 1886 through 1942. In its heyday it was the deepest mine in the United States, with a main shaft that descended over 1,800 meters. Today it’s a historical site featuring the distinctive wooden tailing wheels that have become local landmarks.
Gold mining in California was an environmental disaster. It involved crushing large quantities of ore dug from underground or stripped from the surface, and then washing it with lots of water (or sometimes toxic mercury) to separate the heavy gold from the lighter rock.
Contrary to popular belief, most of the “Mother Lode” wasn’t exactly loaded with gold. The Kennedy Mine is estimated to have extracted slightly less than 16 grams of gold per tonne of ore, a typical ratio for California mines. That one operation generated some 342,000 tonnes annually of tailings, the crushed rock residue left over after extracting the gold.
Mines originally dumped their tailings into the nearest river or creek, polluting farms and endangering navigation. By the beginning of the 20th century, extensive litigation and an early federal environmental law forced mining companies to stop their dumping.
Under the new law, tailings now had to be “impounded” in a landfill. That created a problem for the Kennedy Mine. The nearest practical place to impound the tailings was nearly a kilometer away, and behind two hills.
The Kennedy Mine’s engineers devised a unique solution to that problem in 1912. They built four elevator wheels, each 18 meters across and made of redwood. Along the outer circumference of each wheel were 208 buckets that filled with a sludgy mixture of crushed rock and water. A wheel lifted the tailings in the buckets about 12 meters, and then emptied the buckets into flumes that led to the next wheel. This mechanical bucket brigade carried the tailings over the hills to the impound pit. Operating around the clock, the wheels could move 937 tonnes of waste daily.
The wheels were originally enclosed in corrugated iron sheds. When war regulations effectively shut down all gold mining in 1942, the mine’s owners dismantled the sheds for scrap metal. They left the wheels intact but exposed to the elements. Since then, two of the wheels have rotted and collapsed into “artistic” piles of wood and metal hardware. The other two are preserved in a state of “arrested decay.”
The owners decided not to reopen the mine after the war, as the main shaft and the other 80 kilometers of underground tunnels had become flooded with water. A San Francisco teacher bought the former mine’s 62-hectare site at a liquidation sale in 1961. She lived in a house on the mine grounds until she died in 1994. Her will specified that the mine’s remains be preserved as a historical site.
Indian Grinding Rock State Historic Park is another nearby attraction, 13 kilometers east of Jackson. The park gets its name from a large limestone outcropping into which Miwok Indians dug 1,185 mortar holes. (Yes, someone actually counted them.) They used the holes and stone pestles to grind their staple food, acorns from the abundant valley oak trees. The Miwok called the rock Chaw’se, which means grinding rock.