Case Studies in Construction Quality Control/Quality Assurance Methods for Seepage Cutoff Walls

Cutoff walls are a type of seepage barrier that has become a standard construction method for reducing seepage and mitigating against internal erosion associated with embankment dams and levees. Innovation by specialty contractors over the last 20 years has resulted in advancements in production rates, achievable wall depths, and feasibility of construction in difficult foundation conditions. Evolving construction techniques, many proprietary, include improvements in excavation equipment, materials, and backfill placement techniques. The advancements in cutoff wall construction have led to demand for equally innovative technologies for construction quality control and quality assurance (CQC/CQA). This paper will present case studies of cutoff wall construction at Boone Dam (owned by the Tennessee Valley Authority) and the Herbert Hoover Dike (owned by the United States Army Corps of Engineers) with specific applications of current best practices for CQC/CQA monitoring, verification of cutoff wall construction, and a discussion of lessons learned on each project.