The U.S. Army Corps of Engineers is initiating emergency permitting procedures to expedite cleanup in anticipation of oil coming ashore from the April 20 explosion of British Petroleum’s Deepwater Horizon rig about 50 miles off the Louisiana coast. Corps districts in Alabama, Mississippi and Louisian indicate that they have cut the normally lengthy permitting process to 24-48 hours as authorized under Nationwide Permit 20, which covers those activities subject to the National Oil and Hazardous Pollution Contingency Plan and are performed in accordance with the Spill Control and Countermeasures Plan. Basically, any oil spill cleanup excavation, dredging or remediation in
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.