The U.S. Bureau of Reclamation will examine the possibility of drilling tunnels through Glen Canyon Dam to ensure water can pass through it at low Lake Powell elevations, two knowledgeable sources told the Arizona Daily Star. Such a re-engineering project will be among several options the bureau will look at due to new concerns about the ability to deliver Colorado River water through the 61-year-old facility under such circumstances. It could prevent a catastrophic occurrence if lake elevations ever fall so low that no water could get through the dam to serve farms and Lower River Basin cities, including Tucson, Phoenix, Las Vegas, Los Angeles and San Diego.