Utilizing Geophysics to Optimize Subsurface Targets for Exploration and Pore Pressure Monitoring at Little Bear Creek Dam

Piezometer installations at Little Bear Creek Dam were proposed by the Tennessee Valley Authority (TVA) based on the outcome of a Semi-Quantitative Risk Assessment (SQRA) that identified data gaps in the understanding of site hydrogeological conditions. To provide TVA with a better understanding of the karstic site, a surface geophysical investigation, subsurface exploration, and instrumentation installation program was performed. The surface geophysical investigation was conducted at the site to identify targets for subsurface exploration and piezometer installation. The subsurface exploration and instrumentation installation programs were critical components in enhancing the understanding of pore water pressures and seepage gradients within the earthen embankment, foundation soils, and bedrock. Nine vibrating-wire piezometers were installed in the main earthen embankment dam, seven of which were installed within standpipe piezometers. The results show that the integration of multiple geophysical methods can serve to maximize the value of subsurface explorations.