Performance of the Boone Dam during Reservoir Filling following Remediation

ABSTRACT ONLY - Following observations indicative of active internal erosion in 2014, the Tennessee Valley Authority (TVA) lowered the reservoir at the Boone Hydroelectric Plant in order to reduce dam safety risks until permanent improvements could be implemented. Following investigations in 2014 and early 2015, the TVA adopted a composite seepage barrier remedial solution, the construction of which was completed in early 2021. The composite seepage barrier was composed of low-mobility grouting (LMG), high-mobility grouting (HMG), and a concrete cutoff wall constructed by secant pile construction. TVA began refilling the reservoir in March 2021 for the first time since restricting reservoir levels following the events described above in 2014. The objective of this paper is to document some of the lessons learned collected from the execution of project from 2016 through 2021 and to describe the performance of the embankment dam during reservoir filling. The paper is organized to (i) summarize the tools that were used to reduce seepage beneath the embankment dam, (ii) describe their efficiency at reducing seepage as interpreted by the extensive instrumentation program at the site; and (iii) highlight the overall response and performance of the dam during each phase of the project.