Kiewit's contract was an execution at the start, not a design contract. The initial design hydrology was done through the client. There were targets set of certain boulders, of certain portions of the rock in the river that needed to be removed. Absolutely, there were targets to go and get those key pieces that the group felt would make the most impact to the hydrology.
Once that was achieved and while the water level was still low enough, the group collaborated on next areas to focus on, and removed as much rock as possible before levels came up. Hydrology work was then done to map out how much rock had been removed.