Environmental and energy efficiency advocates are praising the Environmental Protection Agency for issuing guidance to local and state permitting authorities to help reduce greenhouse gas emissions using best available control technologies (BACT). But industry groups have blasted the guidance, saying it could result in a moratorium on the construction of new powerplants and industrial facilities. The EPA released BACT guidance on Nov. 10 to help states and local air permitting authorities identify cost-effective pollution reduction options for greenhouse gasses under the Clean Air Act. The new preconstruction permit program among the states begins on Jan. 2, 2011. Gina McCarthy, assistant
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.