The U.S. Army Corps of Engineers Vicksburg District Mat Sinking Unit departs Monday from the Port of Vicksburg with a barge carrying employees’ cars being floated alongside. During the season that ends in February, workers will place 384,088 articulated concrete mattress squares in more than 30 locations along the lower Mississippi River in the Corps’ attempt to shield the riverbank from erosion and sloughing. The unit will work as far north as Cairo, Ill., and as far south as Tropical Bend, La. The longer-than-normal season will include repairs to sites damaged during the historic 2011 flood.