Now is the time for the U.S. to update its approach to water treatment, says Bob Perciasepe, U.S. Environmental Protection Agency deputy administrator. “[The challenge] is how to get a 20th-century law—the Clean Water Act—appropriate for 21st-century projects,” he said at the Water Environment Federation’s annual meeting, held on Oct. 3-7 in New Orleans. When water-quality standards were first developed during the 1960s, problems such as high nitrogen and phosphorous levels as well as pharmaceuticals and other endocrine disruptors were not considered. Perciasepe said that implementing and enforcing Total Maximum Daily Load standards for contaminants are the best way to
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.