A recent study by the Federal Transit Administration concludes that the nation’s largest transit agencies need at least $50 billion to bring their assets into a state of good repair and another $6 billion would be needed annually for normal maintenance. The Rail Modernization Study, completed in April at the request of Sen. Richard Durbin (D-Ill.) and 11 other senators, examined capital needs of the seven biggest U.S. rail transit agencies. It looked at older systems in New York, Boston, Chicago and Philadelphia, as well as newer systems in San Francisco, New Jersey and Washington, D.C. Combined, the agencies serve
Arch dams, classically curved monoliths situated in narrow valleys, are not as common as other types of dams, such as embankment dams and gravity dams. ENR takes a look at some of the biggest arch dams in the world, both completed and under construction.