The shipping season is ending early on the upper reaches of the Mississippi River because ice is making navigation difficult. The U.S. Army Corps of Engineers says the towboat Mary K Cavarra passed through Lock and Dam 2 near Hastings, Minn, on Thursday. Hastings is about 31 miles southeast of Minneapolis. “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,” said the Corps. The season usually runs until early December in the Twin Cities. The navigation season opened this year on April 16, the second-latest start for river traffic due to the harsh 2013-14 winter.