you are forgetting the black swans, unexpected floods, earthquakes, groundwater seepage and let's not forget terrorists.

These storage facilities are hardly protected and are very easy prey for anyone wanting to hold government ransom. A couple of gasoline trucks and some C4 to split open the barrels would be enough. The wind will do the rest.

Terrorists have 100.000 years of time to make their move one day. No society can afford to protect these storage facilities for so long.