Construction on the Sunrise Powerlink—a $1.88-billion, 118-mile, 1,000-MW-capacity power line that would connect urban San Diego with alternative energy sources in the Imperial Valley—could begin in June if the U.S. Forest Service grants final approval. The owner, San Diego Gas and Electric Co., says the line is a key part of California’s mandated goal of deriving a third of its power from alternative sources by 2020. SDG&E could expedite the decision by meeting two conditions based on environmental considerations: shifting right-of-way to a northern route to avoid crossing designated wilderness areas and completing some construction using helicopters to protect the
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.