On April 27, the U.S. Green Building Council and the Green Building Certification Institute released LEED Version 3. The latest version of the green building rating system, in the works for more than three years, "sets the stage for the growth and improvement of the whole LEED program for the next several years," says Mike Optiz, USGBC's vice president for LEED implementation. The current release includes LEED 2009, LEED Online Version 3 and a new certification process based on ISO standards, administered by the GBCI. It also updates all the LEED categories at once. These include LEED for new construction,
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.