`New Orleans Canal Levee Failure`

1880, the New Orleans levees had a safety factor of 1.3. One of the civil engineers designing those in 1880 was my grandfather. You needed a bigger safety factor, but back then they were lucky if they could even calculate the safety factors. So a safety factor — it's hard to decide what you want to call your capacity, your operating stress will be defined historically by codes and standards, and then it's really a question of what risk you're willing to take. If it's man-rated, you want a bigger safety factor.