Tailoring Cutoff Wall Installation Techniques to the Task

The deep foundations industry offers various cutoff and barrier wall techniques, each suited to specific  conditions. This paper presents four case studies illustrating how these techniques can be adapted or combined for  optimal results in dam and levee rehabilitation. At Herbert Hoover Dike, a performance-based approach allowed for  multiple systems, with the contractor using cutter soil mixing and targeted pretreatment based on subsurface  conditions. At the East St. Louis project, a 142-foot-deep panel wall was installed with the single-phase method.  The Rosshaupten Dam project involved a 230-foot-deep plastic concrete diaphragm wall installed while the  reservoir remained impounded; a pretreatment through overburden and rock grouting mitigated trench stability risks.  At Center Hill Dam, the contractor constructed an up to 300-foot-deep barrier wall, using mostly a panel-only  method, and used secant and panel techniques for the encasement wall to mitigate slurry loss risks.