The mention of the two bunkers at Harrison Hills, the one at
Gov Club, the ones at Yale, the ones at PGA West, etc. all
make me wonder what the definition of a "deep bunker" is.
Does deep technically mean that the faces/slopes of the
bunker must be sand or is it just how far below the (usually)
green the flat bunker is?
Here is right of Harrison Hills to illustrate the point of a
technically flat bunker deep below the putting surface: