Perhaps you should get a Structural Engineer to have a look at it. A roof with all the right sized beams can still collapse due to lack of stability, for example.
I would also like to learn whatever lessons come out of this tradgedy.
I also have sympathy for the construction professionals who have been rounded up in what sounds like a "witch hunt". Perhaps the true location of the blame will emerge in due course.
If there is no water expected, design for water 1 m above bottom of structure, or 1/3 of depth below ground surface, which ever is worse.
If there is any water expected, design for water 1/4 of depth of structure below ground surface.
Water may come from burst mains, climatic change etc., so...