From Good to Great: The Evolution of Cutoff Wall Quality Control and Verification Techniques

The last three decades have brought tremendous improvements to quality control (QC) procedures for construction and post-construction verification of deep cutoff walls installed in active high-hazard dams. Developments have been made in every aspect of the construction processes, including drilling/excavation, cleaning of inter-element joints, preparation and placement of backfill materials, verification of the constructed product, and data collection, representation, and monitoring of dam instrumentation.

Today, client expectations of wall verticality, continuity, and homogeneity have reached heights that would have been thought unattainable just a few years ago. To meet the demanding expectations, sophisticated QC methods have been developed to verify the tolerances project specifications impose. Thus, in addition to using existing QC verification methods, new tools and methods have been developed that integrate outstanding technological hardware and software advances to significantly increase the ability to measure more features of the work and improve the accuracy and reliability of these measurements. To illustrate this evolution, this article examines the state of practice as applied at several major dam cutoff project: Beaver Dam, AR (1992-1994), Walter F. George, AL (2000-2002), Wolf Creek Dam, KY (2008-2014), and Bolivar Dam, OH (2014-2016).