@EthicalSkeptic I was referring to the foundation and how uniform the formation would have to be. What if, 30 foot in and 6 feet down(example) there was an inclusion or some deposit. How would they know if some contact of dissimilar materials were under the foundation?
@EthicalSkeptic My only 2 cents; nobody would undertake a project at this scale w/out knowing the suitability of the bearing material. They didn't have test holes or tools to map the material for joints or fractures or some deposit that would collapse under the overburden. 20' needed uniform.