Son La Dam, located on the Da River in northern Vietnam, will be the largest hydropower project in Southeast Asia when it is completed in 2012. Under construction since 2005, the roller-compacted-concrete dam will measure 139 meters tall, 900 m long and 4.8 million cu m in total volume. Installed capacity will be 2,400 MW. Over 5,000 workers were on-site by May 2009. Electricitie de Vietnam (EVN) is the owner. Colenco Power Engineering Ltd. (Switzerland) was responsible for design. SMEC International (Australia) is the lead construction supervision partner, along with Nippon Koei and J-Power of Japan. Song Da No. 9
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.