The report I read said some of them were 250+ feet deep, out of reach of all known conventional bunker busters.
Hence the need for new bunker busters.
Tactical nuke bunker busters were supposedly turned down by Congress. But a new design of conventional bunker buster is supposedly under development. I do not know how deep it can go, or even if it is ready. But the need would seem to be urgent.
Global security has all the data you'd wish for, including step by step overheads for Natanz.
I'm too tired to look it up right now, but 67 feet rings strong bells in the old memory banks. of course, different failities are at different depths, but if ever I saw a centrifuge hall, Natanz is it.
One of them anyway, there are rumors of identical facilities under mountains north of Tehran, we'd either have to leverage the human ancilliary facilities to render them inop, or put boots on the ground there.
Or...well we don't do things like that, do we?