Tanner is a privately owned dam located in Sheep Ranch, Calaveras County, California, and is regulated by the California Department of Water Resources for safety and inspection. Completed in 1959, Tanner serves primarily for water supply, with additional purposes including irrigation and recreation. The dam is an earth-type structure standing at a height of 35 feet and has a storage capacity of 124 acre-feet, with a drainage area of 2.52 square miles along Cowell Creek.

Despite its satisfactory condition assessment as of September 2017, Tanner has been classified with a high hazard potential, indicating potential risks associated with its operations. The dam's last inspection was conducted in April 2020, with a frequency of one inspection per year. While emergency action plans and risk assessment information are not currently available for Tanner, the dam remains a critical component of the water infrastructure in the area, providing essential water resources for the surrounding community. As a water resource and climate enthusiast, Tanner presents an intriguing case study for understanding the management and maintenance of dams in California's diverse landscape.