The U.S. Environmental Protection Agency on Nov. 23 issued a court-ordered final rule that, for the first time, sets national monitoring requirements and numeric limits on construction-site stormwater runoff. Under the rule, builders on sites that disturb 10 or more acres at one time must comply with specific limits on discharge of soil and sediment into nearby water bodies. Owners and operators of sites that disturb one or more acres must use erosion- and sediment-control best-management practices to reduce stormwater discharge pollutants. EPA issued the rule in response to a 2004 lawsuit. It will phase in the rule over four
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.