 He was then assigned to the HHC 130th Engineer Battalion at Vega Baja, Puerto Rico where he served as Utilities Maintenance Technician.On August 3, 1976, he was promoted to the rank of First Lieutenant and assigned as Engineering Officer for the same Battalion.From January 1977 to August 1979, Díaz Colón served with Company D 130th Engineer Battalion at Carolina, Puerto Rico in the positions of Engineer Platoon Leader and Company Executive Officer.