From 1922 to 1926, Casey was the officer in charge of the Engineer Unit of the Reserve Officers Training Corps (ROTC) at the University of Kansas in Lawrence, Kansas, reverting to his substantive rank of first lieutenant on 27 November 1922. He again returned to Camp Humpreys in 1926 to attend the Company Officers Course. In 1927, Casey received his first civil works assignment, as assistant District Engineer at the Pittsburgh District. Casey took over the task of preparing a voluminous report on flood control. The Corps of Engineers was criticized by the Pittsburgh Flood Control Commission for over-engineering, in planning for a "flood that had never happened and never would happen", and the report was shelved. However, in 1936 the flood did happen. The report was then dusted off and its recommendations were adopted. The Flood Control Act of 1936 assigned responsibility for flood control to the Corps of Engineers and other Federal agencies. Casey was also responsible for construction at Deadman Island Lock and Dam (now called the Dashields Lock and Dam) on the Ohio River.