Protective Water Level
What is the Protective Water Level?
Previously known as the critical water level, the protective level for the Berkeley Pit is 5,410 feet above sea level. The protective level represents a level that is just below the lowest level in Butte’s groundwater system, the stream bottom of Silver Bow Creek.
Below the protective level, water in the Berkeley Pit remains part of a closed-loop water system. It virtually cannot leave this closed-loop system if it stays below the protective level. For more information about the closed-loop system and the science behind understanding it, please see the Water page.
The protective water level has a 50-foot buffer zone before contamination is possible, making the actual contamination level 5,460 feet above sea level.
As ordered by the United States Environmental Protection Agency (EPA) and the Montana Department of Environmental Quality (DEQ) in the 1994 Record of Decision for the Superfund unit that the Berkeley Pit is part of, the water in the Berkeley Pit must be kept below the protective level. Montana Resources and the Atlantic Richfield Company are the responsible parties for keeping the water below this level. For more information on Superfund and Protective Water Level, please see the Superfund page.
Before water reaches the protective level, it will be pumped and treated by Montana Resources and the Atlantic Richfield Company. For information about water treatment, please see the Water Treatment Page.
Who established the protective water level?
The protective water level was set by the U.S. EPA and Montana DEQ in 1994 Record of Decision. For more information on this decision, please see the Superfund page.