From August 1929 until July 1931, Hawley was assigned to the Nicaragua Canal Survey. The United States Interocean Canal Board had approved a two year long project to survey routes for a canal through Nicaragua to join the Atlantic and Pacific Oceans—to be larger than the Panama Canal. A group of 320 engineers and support personnel organized into a provisional engineer battalion—Hawley among them—surveyed multiple routes through the country. In the end the survey's final report found no route truly suitable for a canal at that time. After having fought against malarial bearing mosquitos and a virtual endemic of syphilis in the local population, Hawley was put to work during the March 1931 Nicaragua earthquake, where he and his medical detachment set up a treatment area and provided care for all who presented themselves, performing 10 major and 20 minor surgical procedures. Hawley himself treated the injured from the earthquake for 48 straight hours. For his service, he was one of four officers of the battalion awarded the Presidential Medal of Merit of Nicaragua. Among the other three officers receiving the award were the battalion commander, Lieutenant Colonel Daniel I. Sultan, the battalion executive officer, Major Charles P. Gross, and the A Company Commander, First Lieutenant Leslie R. Groves. All would later raise to positions of prominence in the Second World War. Members of the battalion were also awarded the Second Nicaraguan Campaign Medal for their service there. It was during his tour in Nicaragua that Hawley developed a number of relationships with other officers on the Survey which would serve him well during World War II, when many of them assumed key positions within the European Theater of Operations or the War Department during the war.