There's no risk if he doesn't have any WMD factories, is there?
It's kind of like when an Iraqi official implied a few weeks ago, "We have no weapons of mass destruction...and we're prepared to use them!"
Which is it?
If they have WMD factories, then they're in breach of UN 1441. If they don't have WMD factories, then there's no danger about bombing harmless facilities.
As for bombing WMD factories, any nuclear penetrator is a last resort. We already have conventional bombs that can penetrate up to 60 feet below ground. There are devices like the hyperbaric bomb that burn with a very fierce intensity, probably enough to destroy chemical or biological agents.