This wasn't your question, please pardon me...
Laws treat Ammonium Nitrate as a fertilizer, but sensible engineers should treat it for what it is: an explosive.
A primary explosive if tainted with some fuel. A secondary explosive even if pure. Big amounts even allow it to switch from burning to detonation mode without a detonator.
It happened with a cargo ship in France (Le Havre? 1948?). Good part of the port destroyed.
Law didn't impose appropriate safety measures (would have banned it as a fertilizer I suppose).
So it happened again in Toulouse (2001?). Part of the city destroyed.
It had also happened before and meanwhile. Perfectly known.
So if I can dare a suggestion:
Please do more than law requires. Treat this stuff as far as possible for what it is: an explosive.
Try hard to store limited unit amounts of it, separated in a way that prevents the explosion to propagate.
As such a plant is a perfect target, protect it passively and actively against military and covert action.
Sorry for the interruption.