Witches Brew at Berkeley Pit

November 20, 2009



Photographer: Judy A Mosby
Summary Author: Judy A Mosby

Until 1955, copper mining in Butte, Montana was underground, dotting the surrounding landscape with old mining head frames. In 1955, the Anaconda Copper Mining Company began open surface excavation on the Berkeley Pit (shown above). Open mining is more profitable than underground efforts. Berkeley Pit is named after one of the earlier underground mines, which it would eventually swallow along with many other mines and several residential neighborhoods, including the beloved Columbia Gardens. In 1982, active mining ceased, and the pumps required to remove water from the pit were turned off. Since then water levels have risen, filling the large cauldron with what's believed to be the largest brew of contaminated water in the world. Berkeley Pit, now a sink that collects some 40 billion gallons of contaminated runoff, is a Superfund Site. Main contaminates include iron, zinc and copper. The valuable copper is mined out of the water. The chemistry of the water changes so rapidly at different levels that there's a marked chemocline. In essence, there are two layers of water in the pit with the top layer being more acidic. Only once, during a landslide in 1998, are the layers believed to have mixed. n 2006, a viewing platform was opened to the public which has unexpectedly proven to be a very active tourist attraction (bottom photo). Photos taken on July 4, 2009. 

Photo details: Nikon D70 camera; bottom photo taken with a 10.5 Nikon fisheye lens.

Berkeley Pit Coordinates: 46°01′02.38″N, 112°30′36.60″W