If I understand the power of hurricanes and tornadoes properly, the winds will grab anything that is protruding, and can shove or lift things that aren't anchored down.

IMHO, if you didn't want to totally bury the concrete box, you could bury it halfway, then mound a fairly thick (2 feet?) layer of soil over it, and then plant the mound with something that has a good rooting system, like clover. But I think you would have to have a smooth plate or something for the access hole, something that provided no edge for the wind to grab.

A guy I was talking to a few years ago used to live in OK, and he mentioned that Grade 5 tornado that peeled up the road asphalt: "I wasn't there, but I would bet some money that the wind was able to grab an edge of that asphalt and peel it up like a roof shingle".

Re: safe room in a house -- what would that help if the wind grabbed the house itself? It's just my opinion, but Kevlar is good for some things and not for others. I'll bet that Kevlar grabbed by wind would act just like Tyvek. It MIGHT stay together, but you and your family might be 'mailed' to Oz by TEx (Tornado Express). <img src="/images/graemlins/smile.gif" alt="" />

Sue