A key federal report blames poor management, key missteps and a faulty cement job by BP and others for the worst offshore oil spill in U.S. history and the deaths of 11 rig workers. The details, released Wednesday, were contained in the final report from an investigation team of the U.S. Coast Guard and the agency that regulates offshore drilling. The panel held hearings over the course of a year following the April 20, 2010, Deepwater Horizon tragedy. The Coast Guard-Bureau of Ocean Energy Management Regulation and Enforcement investigation was among the most exhaustive. Other investigations have faulted misreadings of key data, the failure of the blowout preventer to stop the flow of oil to the sea, and other shortcomings by executives, engineers and rig crew members.