Where is the water in the Berkeley Pit coming from?
The water is naturally occurring groundwater. It started flowing back into the area in 1982 when the central pump station in the Kelley Mine was turned off. For nearly a century before 1982, groundwater under the Butte Hill had been constantly pumped to the surface to allow for underground and open pit mining. This pumping created a vast cone-shaped area underground that was kept unnaturally dry. The bottom of the Berkeley Pit lies near the bottom of this dry area. When the pumping stopped, the Pit started working like a big sink, drawing water toward it from all directions.
