Staff Sgt. David Overstreet, 28th Civil Engineer Squadron water fuels systems maintenance, checks proper pressure levels on a high expansion foam system at the Petroleum Oil Liquids Control Facility on Ellsworth Air Force Base, S.D., Dec. 19, 2012. Monthly maintenance checks to the system ensure proper operation in the event an emergency. (U.S. Air Force photo by Airman 1st Class Anania Tekurio/Released)