USACE RISK ASSESSMENTS AND GEOLOGIC EVALUATIONS AT BULL SHOALS DAM, MARION COUNTY, ARKANSAS

Bull Shoals Dam is a concrete gravity dam located on the White River in northern Arkansas that is owned and operated by the U.S. Army Corps of Engineers. Construction was completed in July 1951 for the purpose of flood management, hydropower generation and recreation. The dam is composed of 47 concrete gravity monoliths, each 13.6 m (45 ft) wide, having a maximum height of 78 m (258 ft), at total length of 688 m (2,256 ft) with water level controlled by a 17 Tainter gates that regulate water flowing into the spillway system. The dam impounds Bull Shoals Lake that has a total capacity of 7.1 km³ (5,408,000 acre-ft) and a catchment area of 15,630 km² (6,036 mi²).

A Quantitative Risk Assessment (QRA) has been performed on the dam. The risk analyses considered a hypothetical overtopping during an extreme Probable Maximum Flood (PMF) event. Computational Fluid Dynamics (CFD) modelling was performed to evaluate the bedrock impacts from the hypothetical overtopping flows. The foundation in this area is composed of dolomite with minor interbeds of chert and shale and very minor solutioning. The upper surface of the bedrock is weathered and fractured, making it potentially susceptible to scour and plucking during an overtopping event. The bedrock was characterized for scour potential by conducting surface geophysics and outcrop mapping. This talk will discuss geologic methods used to inform the risk assessment.