A permanent end to a seemingly endless torrent of oil gushing from a runaway well in the Gulf of Mexico appeared in sight in mid-July as BP successfully installed a sealing cap on the wellhead—a crucial step in shutting it down. The cap was bolted on even as a drilling crew was coming close to intersecting the well bore almost 13,000 ft below the seabed with one of two relief wells being drilled nearby. Their aim is to pierce the well bore and kill the well by choking it with drilling mud and cement. BP is owner of the Macondo
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.