A North Dakota Air National Guard CH-47 Chinook helicopter drops several one-ton sandbags onto the spillway of the Clausen Springs Dam near Kathryn, N.D., April 15, 2009. A North Dakota Air National Guard CH-47 Chinook helicopter drops several one-ton sandbags onto the spillway of the Clausen Springs Dam near Kathryn, N.D., April 15, 2009. SHARE: Download: Full Size (5.54 MB) Tags: Photo Essays Credit: VIRIN: 907560-T-DAQ97-491.jpg Photo Gallery