On Oct. 13, the National Transportation Safety Board released its preliminary report on the Sept. 9 gas pipeline explosion in San Bruno, Calif., that killed eight people and damaged 55 homes. The report came a day after Pacific Gas & Electric Co. announced its new natural-gas pipeline safety measures, known as Pipeline 2020. The explosion of a natural-gas pipeline released 47.6 million standard cubic feet of natural gas, creating a crater 72 ft long by 26 ft wide and throwing a 30-in.-dia, 28-ft segment of the pipe 100 ft. Investigators are looking at the sequence of events that led up
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.