The bridge schedule will affect ship and boat traffic. Written By: News Tribune | × The Duluth fireworks explode over the Duluth/Superior harbor behind the Aerial Lift Bridge in celebration of the Fourth of July in 2008. (File / Clint Austin / News Tribune) The Aerial Lift Bridge and the Minnesota Slip Bridge in the Duluth harbor will both remain in the lowered position and closed to water traffic for a large part of the evening on Sunday. The city of Duluth announced the bridges will stay lowered in order to accommodate the large crowds that are expected to gather for Fourth Fest and the fireworks display Sunday evening.