Berkeley Pit Viewing Stand

The Berkeley Pit is a former open-pit copper mine on the east side of Butte, about a mile long, half a mile wide and up to roughly 1,780 feet deep. The Anaconda Company began digging it in 1955, and its later operator, Atlantic Richfield (ARCO), closed it in April 1982. As the pit grew in the 1950s to 1970s it swallowed whole neighbourhoods, including Meaderville, McQueen and Finntown. When the underground pumps were switched off, groundwater began to fill it, and today it holds about 900 feet of acidic water with a pH of around 4.1 to 4.5, carrying dissolved copper, arsenic, cadmium, zinc and sulphuric acid. It is part of the Superfund cleanup along the upper Clark Fork River.

The viewing stand is a platform on the south-west rim. You reach it through a short, dimly lit tunnel from the small building at the entrance, which has a gift shop and restrooms. From the platform you look across the pit lake to the terraced walls and, beyond, to historic headframes and active mine workings. Interpretive panels explain the mining history and the water problem.

The water is the story most visitors come for. It rose at about a foot a month after pumping stopped, and a treatment plant built for $19 million has operated since October 2019 to keep the level below a protective threshold. Birds are the other story. In the 1990s researchers recovered 342 snow goose carcasses from the pit, and in November 2016 tens of thousands of snow geese landed on the water and three to four thousand of them died. Today noise machines, propane cannons, lasers and drones are used to keep flocks off the lake.

The stand is seasonal. The PitWatch website lists it as open daily from 10 am to 5 pm, May to October, weather permitting, and tours can be arranged from March to November by appointment, with at least a week's notice. Visitors have reported closures outside the posted times, so call 406-723-3177 before a special trip, especially late in October. There is a small admission fee; reported amounts have ranged from $2 to $5, so bring cash. A visit takes 30 minutes to an hour.