construction in 1968. The water flowed directly onto the earthen hillside below the emergency spillway, as designed. However, headward erosion of the emergency spillway threatened to undermine and collapse the concrete weir. On February 12, an evacuation was ordered for low-lying areas, due to possible failure of the emergency spillway. The flow over the main spillway was increased to to try to slow erosion of the emergency spillway. By 8:00 pm on the evening of February 12, the increased flow had lowered the water level, causing the emergency spillway to stop overflowing. On February 14, the sheriff of Butte County lifted the mandatory evacuation order. Investigation and reconstruction On May 19, 2017, the spillway was shut down for the summer, to allow demolition and repair work to begin. The total cost of the repair was projected to exceed $400 million, with the $275 million primary contract awarded to Kiewit Construction. FEMA was expected to cover a large portion of the expenses. According to an independent forensics team led by John France, the exact cause of the spillway failure remains uncertain, though they identified "24 possible causes for the spillway failure, including a faulty drainage system, variations in concrete thickness, and corrosion in the structure’s rebar." The DWR has planned for 2018, to demolish and reconstruct the portion of the spillway which was undamaged by the flood, but which also has been identified as structurally defective. In addition, crews are working to extend a cutoff wall under the emergency spillway to prevent erosion should that structure be used again in the future. On November 1, 2017, DWR director Grant Davis said, "Lake Oroville’s main spillway is indeed ready to safely handle winter flows if needed". While this completes phase 1 of the construction, there remains a phase 2 to be completed in 2018. The second phase would include rebuilding the top section of the spillway (which was not rebuilt this season), putting slabs over the roller compacted concrete section, and constructing a concrete secant cutoff wall for the emergency spillway. The cost estimate at this point is over $500 million. In October 2017, hairline cracks were found in the rebuilt spillway. Things that added to the cost included relocating power lines, dredging the river downstream of the dam, as well as the discovery that the bedrock under the spillway was weak, necessitating deeper excavations and more concrete. The DWR commissioned an