Patrick
I checked Shackleford's book on Riviera for the Thomas sketch (my copy of Golf Architecture in America is on loan to a course supt interstate, so I can't check that at present).
On page 68 and 69 of Riviera Country Club's Definitive History, Thomas's graph of the side profile of #18 is reproduced. It shows that without the wash being filled, the green site would have been set just before the wash at a hole length of some 310 yards. With the wash filled in, the green could be located at 430 yards. The chart shows that the new green site would be raised about 10 feet above the natural grade through fill. The area short of the green was to be raised some 27 feet in the deepest part of the wash. So, the sketch implies that the #18 green has been raised and built entirely on fill, and not cut into the hill.
Thomas did write that 'wash was filled by soil taken from the hill at right and greater length secured. Drainage was cared for by piping'. The hill to the right in the sketch is the hill leading up to the clubhouse. The sketch does not show where the cut was proposed.
So Patrick, I think this implies the green was raised, rather than cut into the hill.
There is some interesting editorial on these pages by Ben Crenshaw, who was involved in the restoration of Riviera greens with Bill Coore. Ben described Riviera as
'quite possibly the very finest MADE golf course in the United States'.
Later, he added
'a major fill (27 feet!) was utilized for filling a natural wash some 100 to 150 yards short of the present 18th green, and for the No. 18 green site as well. Thomas and Bell took vast amounts of earth and filled the areas at the base of the clubhouse for several reasons:
1) it took the feature of abruptness out of this wash in order to provide a more gradual climb toward the finishing hole;
2)more length was provided and thus made #18 a more challenging hole;
3) the 18th hole now merged "imperceptibly" with the land leading up to the clubhouse to provide a more natural appearance;
4) to provide a wonderful "natural" amphitheatre for the finish of the round for spectators;
5) the balance of the "cut" and "fill" was utilised in the formation of the Second green, the 3rd teebox, and the 9th green and its surroundings.'
The Definitive History is a good read indeed. I appreciate my copy.
James B