DWR says that costs not covered by FEMA will be paid by the State Water Contractors. That's the group of 27 urban and agricultural water agencies that get water from the State Water Project, of which Oroville Dam is the key facility.

Mellon said Friday the spillway-related costs may continue to "evolve," based on changing conditions or new requirements for the massive project. Work on the main spillway is about half complete, and Kiewit's crews are focusing during the winter months on a massive concrete-pile wall on the slope of the badly eroded emergency spillway. The contractor is also preparing to place a 22-acre "splash pad" on the slope immediately below the massive concrete weir at the very top of the emergency spillway hillside.

One of those unforeseen costs this year could be the potential "corrective action" that DWR says may be needed on three of the 234 concrete spillway slabs placed during the 2017 construction season.

Ted Craddock, a DWR deputy director who has been put in charge of the Oroville reconstruction project, said in a statement he read during the media call that the concrete in the three slabs "did not cure as anticipated." Craddock said the curing problem grew out of an unscheduled outage of a batching plant at the construction site that prevented crews from placing the concrete within the required time and "hot, high winds (that) dried the surface of the slabs before the contractor could finish final surfacing work."

Mellon said in a follow-up email that DWR is consulting with Kiewit and regulators to decide "if remediation is necessary and what that work would include."

Cracking in many of the 234 newly placed concrete slabs came to light last fall when the Federal Energy Regulatory Commission, which oversees the Oroville facilities, asked DWR to explain the cracks and what it planned to do about them.

The department maintained that the cracks "are something you expect to see" and were due largely to reinforcement steel, anchor bars and other design elements that strengthen the slabs but exert stress as the concrete cures.