A six-member panel of federal investigators probing the cause of the BP oil spill got an earful last week, as witnesses testified to a litany of mechanical errors and safety shortcuts that may have played a role in the largest oil spill disaster in U.S. history.

Mike Williams, the Deepwater Horizon’s chief electronics technician, told investigators that the general safety alarm was not fully activated when the rig caught fire. It was typically set to “inhibited” to not wake up the crew in the middle of the night, and because the alarm did not sound during the April 20 disaster, workers were forced to warn those sleeping via the loudspeaker system, hampering evacuation efforts.

Other witnesses throughout the week described a number of mechanical failures in the weeks leading to the explosion, including leaking emergency equipment, computer crashes, and power outages.

Additionally, an audit conducted by BP seven months before the disaster documented a history of mechanical errors, including 390 undone repairs–some labeled “high priority”–that required over 3,500 hours of labor to complete. It is unknown how many of the repairs had been completed before the explosion.

Meanwhile, with the threat of Tropical Storm Bonnie now behind them, crews are preparing to resume work on drilling a relief well and completing the “static kill” procedure to plug the damaged well. According to Retired Coast Guard Admiral Thad W. Allen, the storm has delayed the work by seven to nine days. The “static kill” procedure, in which drilling mud and concrete will be pumped into the leaking well, is now anticipated to begin in early August. Fortunately, tests on the well cap show that it is holding, despite the storm.