U.S. Air Force members of the 90th Civil Engineer Squadron operate an excavator equipped with a hydraulic hammer, left, to break up concrete for removal by another excavator to modify a hole in the concrete in preparation for patching at the North Dakota Air National Guard Regional Training Site, Fargo, N.D., Sept. 29, 2021. The Fargo civil engineer training site is one of four in the Air National Guard. The students are using heavy equipment and materials to patch simulated bomb impact craters to a concrete training runway using a new Rapid Airfield Damage Recovery (RADR) system for the first time at the Fargo site. (U.S. Air National Guard photo by Chief Master Sgt. David H. Lipp)