Structural Diaphragm Walls at the Red Rock Hydroelectric Project

The Red Rock Hydroelectric Project is currently under construction at the existing U.S. Army Corps of Engineers Red Rock Dam on the Des Moines River near Pella, Iowa. A reinforced concrete diaphragm wall constructed of large T-shaped panels was required to form the intake approach channel for the project. In the permanent condition, the wall will be a 69-foot-high cantilever with total depth of 130 feet, including the soil and rock socket, to retain the upstream slope of the existing embankment dam. The diaphragm wall will also be utilized for excavation support during construction of the intake structure and upstream penstocks. An additional diaphragm wall was constructed along the crest of the dam to form a cutoff wall. Both diaphragm walls are critical elements for maintaining dam safety during construction and throughout the life of the project. Therefore, quality control during excavation and construction was paramount.