Barge traffic on a 200-mile stretch of the Mississippi River between St. Louis and Cairo, Ill., is about to be shut down because of low water levels caused by several months of drought. To address shippers' concerns, the Army Corps of Engineers accelerated the removal of rock formations that obstruct the navigation channel and released some water from upstream. The rock project is temporarily affecting river traffic: Boats are allowed through only eight hours a day. Since Dec. 17, he says, more than 300 boats and 2,800 barges have passed through that area. "All things being considered, this is a huge success story," says Coast Guard spokesman Lt. Colin Fogarty.