If it is on the side of the containment pool, the wet well may not be covered by a floor (I have seen conflicting schematics on this). However, Unit 4's primary issues were with their spent rod pool. If that is involved, there are two concrete decks between the bottom of the pool and the space exposed by presumed hole.
So, my guess is the wet well may be exposed by that hole in the curtain wall, and may or may not have any damage, but the wet well is definitely failed in Unit 2, and I can see where they wouldn't want people whooping and hollering about wet wells. I'm sure the insides of that are a complete mess at this point. Even if this was a normal construction site, it would be a complete mess at this point.
I see others have mentioned there may be a truck access tunnel at this spot. Perhaps, but I'm unclear as to the orientation of the 4 sides, and that seems a bit irrelevant to the reactor.
Meanwhile, the NRC daily updates petered out long ago. I'm not planning any trips to Fukushima any time soon.
Update: here is a great presentation we got from Areva. Glad to see it's available to the public:
I can still recall during my sentiment during the unfolding of the Fukushima incident. The whole time, I kept reassuring everyone to keep calm and not assume the worst because the information coming out of TEPCO indicated that the reactor was "OK". Heh, boy did that turn out to be a mistake.
So, what we have here is a situation where TEPCO has dropped a nuclear bomb on their credibility. Normally, I'd give them the benefit of the doubt and assume that all these are perfectly plausible explanations worth considering, but after the way they handled the incident as it was occurring, I'm not inclined to believe anything not seen or verified by my own eyes or trusted third-parties.
A doctored image coming from TEPCO gives us every reason to be alarmed. Given their past behavior, it's a good indication that something is amiss.
I'm not arguing that point. All I'm saying is, whatever is going on, I don't think I'm going to get called back over for contingency operations. The joint task force never disbanded, we're all theoretically still on call for this. As far as TEPCO's relationship with the Japanese people, that is a situation for them to resolve internally. My brother's wife is from Ibaraki prefecture (between Tokyo and Fukushima). He plans to make a career of law in Japan. But I seriously doubt we will see any new catastrophic developments or American tax dollars spent on the problem.