In September 1929 Casey was assigned to the Rivers and Harbors Section of the Office of the Chief of Engineers in Washington, DC. This job involved reviewing the project studies, plans and specifications of all river and harbor projects throughout the United States, including flood control and hydroelectric power projects. He also had responsibility for correspondence with U.S. senators and congressmen. During this time he co-designed and patented the Kingman-Casey Floating Mooring Bit for navigation locks. He was promoted to the substantive rank of captain on 1 May 1933.