The U.S. Army Corps of Engineers, St. Paul District, locked the last tow of the season for the St. Paul, Minn., area today, Nov. 20, because ice conditions on the Mississippi River are becoming difficult for vessels to navigate.

The 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.

The navigation season started April 16, when the Angela K reached St. Paul, Minn. The spring start was one for the record books with ice thicknesses in Lake Pepin, near Red Wing, Minn., reaching 32" in some locations. This season was also the second latest start to navigation in the district's history.

"Despite the late start and needing to close the 9-foot channel for 26 days in at least one location to perform emergency dredging after the June floods, the cargo tonnage is up more than 10 percent at the mainline locks from Hastings to Lock and Dam 10 in Guttenberg, Iowa," said Bryan Peterson, St. Paul District Mississippi River program manager. "Industries saved more than $300 million by using the navigation channel instead of overland shipping methods."

The corps will continue managing the river during the navigation closure in order to maintain the pools. All navigation tows will need to be south of Lock and Dam 5A, near Fountain City, Wisc., by Dec. 1 due to the corps closing the lock this winter to dewater it and perform maintenance on the infrastructure at the facility.

The Ginger Griffin New was the last tow of the 2013 season. She was locked through Nov. 27. The Becky Sue was the last lock of the 2014 season for the three Minneapolis locks, and she was locked through Nov. 15.