The part of the hole where the guy on the right is standing looks to be about 10' deep, and those 'tiles' in the neighborhood of 2' thick by whatever their planar dimensions are.
By the looks of it, about a dozen of them were ripped up and tossed further down the spillway .. imagine one of those comin' at ya !
The right side of the hole appears to be about 30' deep, with lots of unconsolidated material in the egress area bottom right.
Spillway is toast. This shot was taken not too many hours after the one with the men inside the hole inspecting it.
Just saw a news report where one official said that if the dam fails at the auxiliary spillway end, we'd probably get a 30-foot wall of water moving downstream.
I'm guessing that means that if the main part of the dam fails... fuhgeddaboudit!