In response to a February blast that killed six workers at a Connecticut powerplant under construction, the U.S. Chemical Safety Board voted late last month to recommend a ban on use of natural gas to clean pipes. It also called for an end to venting or purging gas indoors, which triggered a fatal factory explosion in 2009 in North Carolina. Board experts probed both accidents on-site. The board also urged the U.S. Occupational Safety and Health Administration to develop rules to ban both practices and for the National Fire Protection Association to take similar action through code revisions. The recommendations
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.