One of the essential elements of infrastructure in the U.S. is the river lock. Most locks close off a 600- to 1,200-foot stretch of river and raise and lower the water in the sealed-off chamber. Towboats and barges enter and exit the locks to travel between sections of river that are at different levels. The U.S. has 242 locks in operation on 12,000 miles of navigable waterways. In 2013, $216 billion in freight moved along them, including the Mississippi, Ohio, and Illinois rivers. Moving oil, coal, soybeans, and cement by barge is much cheaper than by rail or highway: Without the locks, such low-cost shipping would be nearly impossible.
The locks are in dire need of repair and replacement. Mechanized gates get stuck, and chunks of concrete are falling off walls battered by barges. In October 2011 a 280-foot section of wall by the Lockport Lock in Illinois crumbled into the water. In 2013 the Algiers Lock in Louisiana was shut down for four months to repair an underwater part that failed. The shutdown cost businesses $146 million in lost revenue and the expenses of rerouting cargo along other waterways. Some of the hydraulic motors powering the locks were installed in the 1930s. Many of the older locks with 600-foot-long chambers are too small to accommodate the towboat and its typical 15-barge load: The boats have to split up the barges and make two trips through the small locks.