Hartzell is a significant earth dam located in Atascadero, California, along the Santa Rita Creek. Built in 1965, this privately-owned structure serves multiple purposes including irrigation, recreation, and water supply with a storage capacity of 300 acre-feet. With a height of 50 feet and a hydraulic height of 42 feet, Hartzell plays a crucial role in water resource management in the region.

Managed and regulated by the California Department of Water Resources (DWR) under the Safety of Dams program, Hartzell is inspected regularly to ensure its structural integrity and safety. The dam has been assessed to be in satisfactory condition as of September 2017, with a significant hazard potential due to its location and purpose. Despite its age, Hartzell continues to meet the water supply needs of the area and provides essential support for irrigation and recreational activities.

With a drainage area of 3.85 square miles and a surface area of 30 acres, Hartzell is a vital component of the water infrastructure in San Luis Obispo County. The dam's proximity to Atascadero and its role in the local ecosystem make it a key focus for water resource and climate enthusiasts interested in understanding the dynamics of water supply and management in California.