Chicago Transit Authority this fall plans to begin an environmental impact study of upgrades to three rail lines for projects that would cost the agency $1.98 billion. The mass-transit program would extend 5.3 miles of elevated, double track to the city's Red Line, 2.3 miles of trench-and-elevated, double track to the Orange Line and 1.6 miles of elevated, single track to the Yellow Line and calls for building six new train stations. The agency is now seeking about $57 million in federal funding to move forward with the EIS and preliminary engineering. CTA has selected a joint venture of CDM,
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.