MCCOOK, Neb. (AP) – The U.S. Bureau of Reclamation has awarded SEMA Construction of Centennial, Colo., a $15.3 million contract to repair and modify Red Willow Dam in southwest Nebraska.  The bureau discovered tension cracks in the dam’s embankment and a sinkhole on the downstream side of the dam in October 2009. Water in Hugh Butler Lake was drained to ensure downstream safety. The dam sits about 10 miles northwest of McCook. Red Willow Dam is an earthfill embankment that is 126 feet tall. The reservoir lake can hold more than 86,600 acre-feet of water. An acre-foot is almost 326,000 gallons of water, or enough to cover an acre of ground with a foot of water.