On the heels of two high-profile oil- pipeline leaks in Michigan and Illinois and a high-pressure gas-pipeline explosion that killed at least four people and destroyed a neighborhood in San Bruno, Calif., U.S. Transportation Secretary Ray LaHood on Sept. 15 sent to Congress proposed legislation to beef up federal regulatory oversight and increase penalties for violations of pipeline safety rules. Photo: Courtesy of U.S. Government Technicians in protective equipment prepare pipe section before cutting and removing it from the Enbridge pipeline oil-spill site near Marshall, Mich. The segment was shipped to federal lab for analysis. The legislation the proposed bill
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.