SHASTA LAKE, Calif. (AP) – A U.S. Bureau of Reclamation crew has begun testing the strength of Shasta Dam’s concrete as part of preparation work to raise its height by more than 18 feet. Crews are drilling holes on top and on both sides of the dam to determine if the 602-foot structure can withstand the additional height. Don Bader, the bureau’s area manager, says crew will drill about 70 holes in the dam over the next few weeks. He says they will also be drilling into the bedrock beneath the dam. The bureau has been studying the idea of raising the 602-foot high structure since the 1980s. Bader says the bureau plans to award a contract to raise the dam in December 2019 and work would begin shortly thereafter.