Compressional- (P-) wave seismic refraction data were acquired in December 2018 and July 2019 along fourteen profiles within the spillway of Success Dam in Porterville, California. A new concrete ogee weir is planned for construction within the existing spillway, and the P-wave seismic velocity models will be used to inform further geotechnical investigations, including siting new geologic borings, and the advanced engineering design phases in terms of rock rippability and relative rock hardness/competency. Data acquisition, processing, and modeling were conducted collaboratively between the U.S. Geological Survey (USGS) and U.S. Army Corps of Engineers (USACE) Sacramento District. Data were acquired with Geometrics Geodes seismographs and 40-Hertz (Hz) P-wave geophones. Acquisition geometries were nominally 96 or 144 live channels with 3- or 6-feet (ft) geophone spacing and a nominal shot spacing of 12 ft with additional off-end shots to increase the maximum depth of investigation. Sources included 16-pound (lb) and 20-lb sledgehammer and plate and a 100-lb truck-mounted accelerated weight drop (AWD) source and selected based on vehicle accessibility and logistical constraints.