Mississippi River barge traffic near Burlington, Iowa, remained backed up on Thursday after lock 18 in Gulfport, Illinois, reopened Wednesday afternoon after a day-long shutdown, river officials said. Lock 18 was closed Tuesday morning when a breakaway barge caused two loaded barges to sink near the lock and left six other barges adrift at the dam. "We've got two barges still floating in the dam and two sunk, with the salvage unit on the way to clear it out. But we've been up and running since noon yesterday," said Frank Robbins, lock master at Gulfport, which is about 60 miles south of Davenport, Iowa. But river traffic was still feeling the effects of the shutdown on Thursday morning, as 5 northbound barge tows and 9 southbound tows were backed up outside lock 18.