Lee attended the Army War College from September 1931 to June 1932, and then was Assistant Commandant of the Army Industrial College until January 1934. He was promoted to lieutenant colonel again on 1 December 1933. He was seconded to the Civil Works Administration until May 1934, when he became District Engineer of the Washington District, in charge of Potomac River watershed, northwestern Chesapeake Bay and the Washington, DC, water supply. He was then District Engineer of the Philadelphia District until April 1938, when he was made Division Engineer of the North Pacific Division, based in Portland, Oregon. He was promoted to colonel again on 1 June 1938.