Abstract:
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 to mitigate long-term dam safety risks. The
remediation is composed of specialty geotechnical construction techniques deep below the ground
surface with the intention to significantly reduce or eliminate the risk of internal erosion through the
embankment and its foundation. 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. The objective of this paper is to provide a case history for the performance of an
embankment dam on a karst foundation undergoing preventative and remedial grouting as part of the
construction of a composite seepage barrier. The paper is organized to (i) introduce the project
background, objectives, and geologic setting; (ii) summarize the tools that were used to reduce seepage
beneath the embankment dam, (iii) describe the foundation response through as interpreted by the
extensive instrumentation program at the site; (iv) highlight the overall response and performance of
the dam during the respective phases of grouting.