Brandon Olson, U.S. Army Corps of Engineers, St. Paul District survey technician, drills into the ice on Lake Pepin, near Red Wing, Minnesota. The Corps takes ice measurements on Lake Pepin annually to forecast the navigational outlook. Lake Pepin’s ice thickness is measured because it’s the widest naturally occurring part of the Mississippi River. The lake’s ice is the last major barrier for vessels reaching the head of the navigation channel in St. Paul, Minnesota.