The Macondo well accident in the Gulf of Mexico, which marked its fifth anniversary on Monday, was a true tragedy. Eleven oil rig workers lost their lives, and no well is worth the loss of a single life. Tens of thousands of people in hundreds of communities were affected directly and indirectly by the ensuing oil spill.

But even as we study the Obama Administration’s newly issued blow-out preventer and well control regulations, at least four of the lessons we already have learned from this accident have and will continue to make offshore oil and natural gas drilling safer.