Yes, that's a great question.
Our reactor and containment building—the nuclear island—is approximately 140 feet deep. That would result in basically a single-storey building that's above ground, similar to a supermarket, which has no safety function whatsoever. It has a number of truck bays and those types of things. All of the safety structures are embedded underground.
The key there, of course, is that they are what I will call below grade. So in locations where you have issues with deep excavation or water, it's then more about creating a berm under which the structure can be located to protect it from external threats. That's the main goal.