Hat Rapids, located in Tomahawk, Wisconsin, is a gravity dam on the Wisconsin River that serves primarily for hydroelectric power generation and recreational purposes. Built in 1923 by the designers MEAD & SEASTONE, this dam stands at a height of 30 feet and has a storage capacity of 4750 acre-feet. With a controlled spillway and five Tainter radial gates, Hat Rapids has a significant hazard potential and is under the regulation of the Federal Energy Regulatory Commission.

The dam has a structural height of 29 feet, a hydraulic height of 20 feet, and a length of 1004 feet, covering a surface area of 640 acres within a drainage area of 1143 square miles. It has a maximum discharge capacity of 12900 cubic feet per second and is situated in a picturesque location in Oneida County. Despite its age, the dam's risk assessment is rated as very high (1), making it a critical structure that requires regular inspections and emergency preparedness measures.

Although not state-regulated, Hat Rapids is subject to federal oversight by the FERC, which handles its inspections and enforcement activities. The dam has seen no recent modifications and is supported by a soil foundation. With its historical significance and vital role in water resource management and energy production, Hat Rapids stands as a testament to engineering ingenuity and the enduring impact of hydroelectric infrastructure on the surrounding environment.