Mark,
How does one go about surface draining a grass bunker, which I would understand to be a hollow/hole in the ground in some form or another, unless it was built on sand soils? Or, would the shape of the bunker be such that it had a sublte creative outlet that allowed surface runoff water to escape, but looked as though it fit the bunker and its surrounds? If so, would it then really be considered a grass bunker...guess it depends on ones definition of a grass bunker and since I haven't reached that point in your book, maybe I should shut up and go read!