On March 3, the U.S. Energy Dept. formally withdrew its application with the Nuclear Regulatory Commission to make southern Nevada the site of national nuclear-waste repository. The move comes after 23 years and $38 billion in studies at Yucca Mountain, 90 miles northwest of Las Vegas, where it had planned to store up to 77,000 tons of radioactive waste from 80 sites in 35 states. The construction price tag was estimated at about $100 billion. It leaves the waste problem unresolved and the federal government exposed to utility lawsuits. Since 1983, ratepayers have paid over $33 billion into the Nuclear
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.