RIVERDALE, N.D. (AP) — The U.S. Army Corps of Engineers has opened the spillway gates on Garrison Dam for only the second time in more than six decades.

Opening the gates had been reserved for emergencies, when the Lake Sakakawea reservoir on the Missouri River could hold no more water. They were opened for the first time during the high water year of 2011.

The Corps opened them again Monday, to test their ability to help with incremental lake level adjustments. Officials also tested repairs made after the flooding seven years ago.