Callahan Lake in Sawyer, Wisconsin, is a privately owned reservoir with a primary purpose of recreation. The dam at Callahan Lake is a gravity type structure with a height of 15 feet and a hydraulic height of 3.1 feet. Completed in 1938, the dam has a storage capacity of 6,300 acre-feet and a surface area of 586 acres. The lake is situated on the North Fork Chief River and is regulated by the Wisconsin Department of Natural Resources.

Despite being classified as low hazard potential, Callahan Lake poses a very high risk due to its location and structural characteristics. The last inspection of the dam took place in December 1996, with an inspection frequency of 10 years. The condition assessment of the dam is currently not rated, indicating a need for further evaluation and maintenance. Emergency action plans and inundation maps for the reservoir have not been prepared, highlighting potential gaps in emergency preparedness.

Water resource and climate enthusiasts interested in Callahan Lake will find a unique recreational spot with historical significance. The dam's construction in 1938 and subsequent modifications in 1954 contribute to the rich environmental and engineering heritage of the region. With its controlled spillway and low hazard potential, Callahan Lake presents both opportunities for recreational activities and challenges for ensuring its safety and sustainability in the face of potential risks and emergencies.