n 1947 ACM initiated the Kelley Greater Butte Project, a major block-caving operation directed from a new concrete-lined shaft in Dublin Gulch, to be known as the Kelley shaft. Block-caving constituted a non-selective underground mining technique developed for low-grade copper ores. Upon completion in 1947, the Kelley became the most productive hoisting shaft in America, capable of bringing four times more ore to the surface than either the Badger or Mountain Con, previously Butte's most productive hoisting operations. Daily production levels eventually reached 15,000 tons.
The Kelley was the last underground mine to operate in Butte, ceasing operations in 1981. Deep in the Kelley Mine at the 3,900-foot level, the pumps used to dewater the underground mines and the Berkeley Pit ran until April 23, 1982. Without pumping, the Berkeley began to fill with water from both surface runoff and groundwater. Due to both the natural geochemistry of the area and mining activities, the water is highly acidic and contains high concentrations of dissolved heavy metals.
The Kelley mine is still used to monitor groundwater levels in the vicinity of the Berkeley Pit.
Ref. [url]http://wikimapia.org/10236809/old-Kelley-Mine-headframe-and-buildings[/url]