Berkeley Pit is a rather infamous tourist attraction located in Butte, Montana. It was originally the site of a copper mine owned and operated by Anaconda Copper, and years later by the Atlantic Richfield Company. The pit itself measures in at an astounding size of 7,000 feet long, 1,600 feet deep, and 5,600 feet wide.
Within its first year of operation, an approximate 17,000 tons of ore were extracted from the pit per day. It was fully operational from the time it was first opened in 1955 until its official closure in 1982. At the time of its closure, the customary water pumps located at the bottom of the pit were removed subsequently. As a result, it wasn't long before the pit itself filled with an estimated 30 billion gallons of groundwater that seeped in from surrounding aquifers. However, this seepage would soon prove to be the root of a rather disturbing problem.
The water within Berkeley Pit has been found to be extremely toxic as a result of its seepage through and absorption of some of the highly toxic metals and substances to be found within the surrounding soil. These highly dangerous and poisonous substances include zinc, cadmium, sulphuric acid, and arsenic. Furthermore, the dissolved oxygen within the water causes many of the natural minerals and metals within the surrounding rocks to break down, releasing dangerous acids as a result. The estimated pH level of the water in Berkeley Pit is about 2.5 making it more acidic than beer, coffee, vinegar and even acid rain. The water in the pit is even rumored to be responsible for the deaths of 342 snow geese that landed on it in 1995.
Obviously, the presence of such a situation poses major concern for the safety of the surrounding environment, as well as a threat to the purity of the associated groundwater. If left completely to its own devices, it's possible for the toxic pit water to begin seeping into the groundwater supply with disastrous consequences.
As a result, the pit has been on the receiving end of a fairly extensive effort to clean it up and get the toxicity problem under control once and for all and is today considered one of the largest "Superfund'' sites in the country. One of the most recent developments on this front was the construction of a treatment plant on nearby Horseshoe Bend. The plant not only diverts and treats water originating from the Horseshoe Bend flow, but it is expected to be able to further combat the toxicity problems within the pit as a collective in the future as well.
Currently, Berkeley Pit is open to the public from March to November as a popular tourist attraction. For a small admission fee, visitors are allowed access to a viewing platform located above the pit the better to observe the infamous toxic location in person. There is also a Berkeley Pit gift shop located on the premises for the convenience of visitors.