Mccoy Flat is a privately owned Earth dam located in Susanville, California, along the Susan River. Built in 1891, this dam serves primarily for irrigation and water supply purposes, with a storage capacity of 17,290 acre-feet and a maximum height of 21 feet. The dam has a low hazard potential and was last inspected in September 2020, with a satisfactory condition assessment reported in September 2017.

Managed by the California Department of Water Resources (DWR) under the Safety of Dams program, Mccoy Flat is regulated, permitted, and inspected by the state agency to ensure its safety and compliance with regulations. Situated in Lassen County, this dam plays a crucial role in water management and supply for the surrounding area. Despite its age, Mccoy Flat continues to function effectively, providing essential water resources for agriculture and local communities.

With a beautiful surface area of 1,800 acres and a drainage area of 110 acres, Mccoy Flat is not only a vital infrastructure for water supply but also a scenic spot for water resource and climate enthusiasts to appreciate. The dam's historical significance, coupled with its functional importance, makes it an intriguing site for those interested in the intersection of water management, climate resilience, and infrastructure development in California.