Assignment
To design a 100-million-ton expansion to the existing Bruno Creek Tailings Impoundment at a molybdenum mine located in  seismically active Custer County, Idaho.  At the start of the Phase 8 expansion project, the existing tailings dam height of 550 feet made it the second tallest centerline-raise cycloned sand dam in the world.  It will reach nearly 750 feet following the Phase 8 expansion.

Our Role
The results of the alternatives evaluation required partial realignment of the dam crest at the left abutment, resulting in a short length of the dam being constructed over an existing tailings beach.  Further, the Phase 8 design incorporated steepening of the downstream dam slope from 3H:1V to 2.75H:1V, as well as construction of a 40-foot raise on the existing Rock Toe Dam. The project met regulatory requirements, achieving a permit from the Idaho Department of Water Resources (IDWR) in early 2008.