You forgot to mention
the gas terminal
even a relatively small detonation, flinging relatively few viable explosives would be enough to create some fireworks. It would also not be entirely clear how long you had to wait before you consider that any more would not be dislodged after being destabilised by the initial ignition.
Only needs one ship with engine failure to bash it, or a sudden, significant structural failure (not unlikely either), or someone, gosh, attempting to do it deliberately.
There are a few tonnes of WW1 explosives kept nicely out of sight underground too, that were never removed or exploded (look it up) but they are not near said, shipping lanes, gas terminals, docks etc.