Along with Lucius Clay, Casey was sent to the Philippines in 1937 to advise the government there on hydropower and flood control. They worked with Meralco and other power companies in the Philippines, and conducted a series of surveys, including a detailed one of the Agno River. After Clay returned to the United States, Casey developed plans for the Caliraya Dam, a hydroelectric project with an estimated cost of $5 million. Along with Lieutenant Colonel Dwight D. Eisenhower, the chief of staff to Major General Douglas MacArthur, the Military Advisor to the Commonwealth Government of the Philippines, and Mr. Rodriquez of the National Power Corporation, Casey presented the project to President Manuel Quezon, who approved it. After over twenty years as a company grade officer, Casey was promoted to major on 1 February 1940.