Worst case scenario

In the last 6 year I have seen 3 events that were made worse by man believing that the worst case scenario would not be possible.  

New Orleans took a direct hit from Hurricane Katrina.  The storm was a category 3 when it made landfall, certainly not the most powerful of storms.  However, the storm surge is what really caused the damage.  The levee systems were not designed to handle what the designers believed would not be possible to actually happen

The Deepwater Horizon oil spill became a disaster because of the failure of the blowout preventer.  The safety system on this deep water drilling rig was not designed to handle what the designers believed would not be possible to happen.

Now, in Japan we see the concern over the destruction caused by an earth quake, quickly give way to the horrors of possible multiple nuclear meltdowns.  The systems designed to keep nuclear reactors cool, and their backup systems, have failed.  What is the next level of backup?  There is none because the design of the safety system did not account for what the designers believed would not be possible to happen.

I’m reminded of the line from the movie Princess Bride where, yet one more time, Vizzini utters the word “inconceivable” and Inigo Montoya tells him, “You keep using that word. I do not think it means what you think it means”.

It seems that safety systems on some of our most dangerous ventures are designed more with an eye on “economic outcomes” instead of worst case scenarios.  Of course, a worst case scenario depends on what is conceivable in the minds of the designers.