Piper Alpha Oil Rig - $3.4 Billion

The world's worst off-shore oil disaster. At one time, it was the world's single largest oil producer, spewing out 317,000 barrels of oil per day. On July 6, 1988, as part of routine maintenance, technicians removed and checked safety valves which were essential in preventing dangerous build-up of liquid gas. There were 100 identical safety valves which were checked. Unfortunately, the technicians made a mistake and forgot to replace one of them. At 10 PM that same night, a technician pressed a start button for the liquid gas pumps and the world's most expensive oil rig accident was set in motion.

Within 2 hours, the 300 foot platform was engulfed in flames. It eventually collapsed, killing 167 workers and resulting in $3.4 Billion in damages.