It's possible to drill or cut without creating sparks. Just need to control the speed of the cutter.
Besides, tanks like these have various portholes, valves and drains already. The article mentions an "inoperable valve" so maybe that's the problem but I'd be surprised if there were just one. They must have been getting the contents out of the tank and into the manufacturing process somehow.
Does this mean that we should shoot holes in it like cowboys to relieve pressure, or does that instead mean that we should not shoot holes in it like cowboys to relieve pressure?
(Because, I mean: If this thing is as sketchy as it is made out to be, then nobody is just walking over there with a spanner to loosen a cover. There aren't enough dollars nor PPE available to make this happen.)
Shooting holes in pressurized vessels with explosive stuff is probably a very bad idea, as outlined in my comment[1]. Slowly loosening a valve is a better idea.
That being said, in no way, shape or form am I an authority on the subject.
Besides, tanks like these have various portholes, valves and drains already. The article mentions an "inoperable valve" so maybe that's the problem but I'd be surprised if there were just one. They must have been getting the contents out of the tank and into the manufacturing process somehow.