This report presents the results of a specific site assessment of the dam safety of the Fly Ash Pond and Bottom Ash Pond coal combustion waste impoundments at the Arizona Public Service (APS) Cholla Power Plant in Joseph City, Arizona. The assessments were completed on September 2, 2009. These impoundments were assessed because their failure may result in significant economic loss, environmental damage, disruption of lifeline facilities or loss of life (significant or high hazard according to U.S. Environmental Protection Agency (EPA) classification). The specific site assessment was performed with reference to Federal Emergency Management Agency (FEMA) guidelines for dam safety, which includes other federal agency guidelines and regulations (such as U.S. Army Corps of Engineers and U.S. Bureau of Reclamation) for specific issues, and defaults to state requirements where not specifically addressed by federal guidance or if the state requirements were more stringent.