My house has been sitting in Kansas since 1964. It has never received tornado damage. It was never built to survive a tornado either. The bio-defense facility is going to be a modern and more-or-less tornado proof building. Simple construction techniques can make buildings pretty much indestructible. An earth wall with a 3-4 foot high concrete wall on top of that with a total height the same as the facility would be enough to protect the facility from even the most powerful tornadoes. I just don't see this as a problem.