WABASHA, Minn. – U.S. Army Corps of Engineers, St. Paul District employees Al VanGuilder, left, survey technician, and Bill Chelmowski, marine machinery mechanic, use an airboat to measure ice on Lake Pepin, near Wabasha, Minn., Feb. 13, during the first Mississippi River ice surveys of the year. The district conducts the annual ice surveys to help the navigation industry determine when it is safe to break through the ice. Lake Pepin, located on the Mississippi River between Red Wing and Wabasha, Minn., is used as the benchmark because the ice melts slower in this area due to the lake width and the slower current.