The committee, made up of dam owners, residents living downstream of dams, consulting engineers, and government employees, has been advising DNRC in drafting new rules for spillways. These proposed rules would be applied to privately owned dams as well as dams owned by cities, counties, and the State of Montana. They will not be applied to federally owned dams, dams on federal property, and hydropower dams since the federal government regulates these dams.
Spillways are an important element of any dam.
During a flood, water will overtop a dam if the spillway is not adequately sized. For earth-filled dams, overtopping most often leads to complete dam failure and can result in a loss of life as well as significant property damage. Overtopping of concrete dams can also lead to failure, but not unless the level of water over the dam is significantly higher. For complete safety, a spillway needs to convey the maximum flood that could ever occur. Therefore, the size of spillway required for each dam, under the proposed standards, will depend on the number of people living below the dam.