Totally correct the superintendent is the person nominated under...

Totally correct the superintendent is the person nominated under the contract to be the principals agent and is not independent of HRR at all. that being said that sort of over-run seems pretty over the top for and the only two ways I can imagine that it could happen is ground conditions, which are early in the scope and often not included in a GMP but as a provisional sum, or client initiated changes of scope. Both of these would have come up early in project execution.

My guess is that it has cost more than Sedgman allowed and they are trying to claw back some cost blowouts. Prediction for final outcome from me is HRR will pay something which will be offset against the LD claim (which at the end of the day may be what Sedgman is trying to avoid).