It's a whopper.
JMorgan has highlighted the issues; here's how I understand them:
*No topsoil. The site was tree mulch over rock, so a soil base needed to be created.
*Clearing. Much heavier sledding than anticipated. It had all the "worst" elements of a site that needed to be cleared: bogs, rock outcroppings, large hills, to name a few. A sense of what they were up against was naming the hill on the 7th "Horse Hill." It earned the name by killing one of the work horses.
*Drainage. Very impermeable. Macdonald's niece said he told her the *only* reason he decided to accept the commission was during one of the surveys they discovered a "seam of sand." Without that discovery, things would have turned out very differently.
* Labor. While machines were used, most of the above had to be accomplished with horse, pan, and hand.
Mark