So the probability of an oil spill between Roseville and Benicia is allegedly 0.009 percent in a year. That number is small comfort.
It does not magically prevent a spill that obliterates Whole Foods, Napa Auto Parts, and much of our beloved downtown.
Before that number is treated seriously we should see the assumptions on which it is based. When we examine the arithmetic we should watch how the human element was incorporated. That is the weak spot in any such calculation. Human beings misread dials, and they make wrong decisions under pressure. Witness the Three Mile Island partial meltdown in 1979, well described on the web.
Besides, as the 500-year-flood could arrive this winter, an oil spill, however rare, can take place any time it chooses.