Paul,
At first he only lengthened the course (1924). In the 40s he removed many of the bunkers that Colt laid out, especially cross bunkers in long par 4s and 5s. He also redesigned two par 3s that were completely surrounded by bunkers.
His greens were all flattened out in 1966 by Harris and the centerline bunkers did not last more than 7-8 years. Strategic trees he brought into play in some holes, however, were not brought down.