The U.S. Environmental Protection Agency announced on Sept. 30 that it would use the Clean Air Act to potentially regulate greenhouse gasses. Industry sources say the proposal, which applies to stationary sources that emit more than 25,000 tons of greenhouse gasses annually, could result in litigation and construction delays if it were to go into effect. The same day, Sens. Barbara Boxer (D-Calif.) and John Kerry (D-Mass.) introduced legislation to address global warming in the Senate. The House of Representatives passed a global warming bill last spring, but the Senate has failed to move forward on a comparable bill until
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.