Paul:
If I'd ever get my book finished about Pacific Dunes, you wouldn't have to ask this question, but since it's not done yet ...
Probably 90% of the fairway contours at Pacific Dunes are natural, or less than that if you refuse to count the contours on three fairways which we had to cap with sand because they were blown down to sandstone.
The most completely natural fairways are holes 2, 3, 5, 7, 8, 12 & 13 (which had to be capped), and 16. We had to do a bit more work on the others, but only in confined spots, not the whole fairway.
And yes, we're going to start on the fourth course after January 1st; and no, we didn't start the fire, it just happened and luckily (because we had been clearing the edge of the third hole up over the dune) it didn't go down the dune all the way to the resort.
P.S. The fact that nobody else here could really answer your question is a testament to the quality of the work that my crew did out there. Other threads are busy arguing about whether "natural" architecture is as good as "man made" architecture but the best occurs when you can't tell the difference.