Go to this link below it shows the PEPCON Rocket fuel factory which after the first shuttle diasater kept making solid rocket fuel, ran out of the normal storage containers and started storing them in PVC barrels and that mixed with a welder doing routine maintenance. Well watch the film, it was taken by some people erecting a cell tower on a hill five plus miles away so you can get a sense of the size of this event.
http://www.youtube.com/watch?v=HJVOUgCm5Jk
http://www.youtube.com/watch?v=HJVOUgCm5Jk