In May 2020, heavy flooding resulted in the catastrophic failure of the Edenville Dam embankment, sending a wall of water downstream in the Tittabawassee River and completely draining Wixom Lake. The breach wave quickly overwhelmed the downstream Sanford Dam, overtopping and failing the structure. Over 10,000 residents in Sanford, Midland, and Saginaw were evacuated. The independent forensic team charged with investigating the event released an interim report in September 2021. The conclusions of the report include a discussion of a relatively rare phenomenon in earthen dams. Let’s walk through the investigation to try and understand what happened.