Electromagnetic induction (EMI) data, Jim Woodruff Lock and Dam, Chattahoochee, Florida, March 2018

Surface electrical resistivity tomography (ERT), electromagnetic induction (EMI), and self-potential (SP) data were acquired March 9 - 20, 2018 by the U.S. Geological Survey, in collaboration with the U.S. Army Corps of Engineers, at the Jim Woodruff Lock and Dam near Chattahoochee, Florida. Frequency-domain electromagnetic induction data were acquired along approximately 9 line-kilometers with the Geophex GEM-2 system to map variations in structure up to about 10 m in depth. This data release includes the raw and processed frequency-dependent in-phase and quadrature data. They are provided as digital data, and data fields are defined in the data dictionary (https://www.sciencebase.gov/catalog/item/5e101094e4b0b207aa163768). Jim Woodruff Lock and Dam is located on the Apalachicola River just south of the confluence of the Flint and Chattahoochee Rivers along the Florida-Georgia border. Construction was completed in 1954 and impounds Lake Seminole. The dam has a long history of excessive seepage along the right abutment and below the fixed-crest spillway. Several karst features have been mapped over the years including sinkholes, both on land and along the lake bottom, and disappearing and reappearing streams. Such features were excavated and grouted during construction. Despite years of investigation of the dam foundation, there remains uncertainty on the flowpaths of water below the fixed-crest spillway and along the adjacent right abutment. REFERENCE Abraham, J.D., Deszcz-Pan, M., Fitterman, D.V., and Burton, B.L., 2006, Use of a handheld broadband EM induction system for deriving resistivity depth images, in 19th Annual Symposium on the Application of Geophysics to Engineering and Environmental Problems, Seattle, Washington, April 2–6, 2006, 18 p.