The U.S. Army Corps of Engineers, St. Paul District, locked the last tow of the season for the St. Paul, Minn., area Nov. 20, because ice conditions on the Mississippi River are becoming difficult for vessels to navigate. The Motor Vessel Mary K Cavarra was locked through Lock and Dam 2, near Hastings, Minn., with four barges. Traditionally, the last tow heading south of Lock and Dam 2 has marked the unofficial end of the navigation season for the Twin Cities portion of the St. Paul District.