The Environmental Protection Agency has set a timetable for regulating greenhouse gases from powerplants and oil refineries that some critics say is unrealistic. But environmental advocates say the development of the New Source Performance Standards for greenhouse gases under the Clean Air Act is long overdue and will supplement some 75 other New Source Performance Standards already in existence for the power sector and other industries. Photo: Courtesy EPA Powerplants would be regulated under the New Source Performance Standards program. The timetable is part of a settlement reached among EPA and several states—including California, Rhode Island and Massachusetts—and environmental groups,
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.