Oroville >> A hole in the concrete spillway chute of the Oroville Dam first made itself known 100 days ago.

How it got there is still a mystery, as is what it will cost to fix the resulting damage and whether a fix will be in place in time for the next rainy season.

These key dates show what happened leading up to the break and what has happened since the hole began breaking open and was spotted by the Department of Water Resources.

Dec. 8, 2016, to Jan. 31, 2017: Lake Oroville bottoms out Dec. 8 at 725-foot elevation and begins rising, but is 175 feet from full. Jan. 13 when the lake is 50 feet from full, the spillway is opened to release 15,000 cubic feet per second. Before Jan. 31, the lake tops 855 feet and releases fluctuate between 12,500 cfs and 20,000 cfs.

Feb. 3-6: Multiple storms cause the DWR to increase releases up to 50,000 cfs. The lake elevation is 849 feet.

Feb. 7: Spillway releases increase, with target of 65,000 cfs. However a large hole breaks open in the spillway floor about noon, about midway down, and the releases are stopped. With inflow in excess of 100,000 cfs, Lake Oroville begins to rise rapidly, topping 862 feet.

Feb. 8: With the lake continuing to rise, the DWR conducts test releases through the damaged spillway of 20,000 cfs to see how much erosion occurs. Lake level nears 875 feet with inflow still in excess of 100,000 cfs. With no other option, DWR begins releasing 35,000 cfs down spillway, recognizing the bottom may wash away.

Feb. 9-10: Spillway releases increased to 65,000 cfs, then scaled back to 55,000 cfs. DWR says inflow has peaked and is declining, says 55,000 cfs discharge should be enough to keep the emergency spillway from being used. Regardless, the water agency removes trees, rocks and debris from slope below emergency spillway weir. PG&E removes power lines crossing the area that might be flooded if water tops emergency spillway weir. Lake level tops 890 feet, 10 feet from full. On Feb. 10 work continues below emergency spillway weir and the Hyatt Powerplant is turned off as debris accumulates in Diversion Pool at base of spillway.

Feb. 11: About 8 a.m., lake level tops 901 feet and begins spilling over emergency spillway weir for the fist time since the lake was completed in 1968. Main spillway releases continue at 55,000 cfs.

Feb. 12: Lake reaches 902.59 feet at 3 a.m. and begins to decline, but water is still running down the emergency spillway. At noon, DWR describes the situation as “stable.” However, at 3 p.m. a gash erodes into the hillside below the emergency spillway weir and begins cutting back toward the weir, raising the risk of a catastrophic failure that could release in excess of a quarter-million acre-feet of water down the Feather River. Releases down main spillway are increased to 100,000 cfs to relieve pressure on weir. Butte County Sheriff Kory Honea orders immediate evacuation, as do sheriffs in Yuba and Sutter counties. All told, in excess of 180,000 people are told to leave their homes.

March 6: Despite repeated requests for information, DWR refuses to say how much has been spent during the emergency. State Assemblyman James Gallagher finally gets an answer: $4.7 million per day, or $100 million during February alone.

April 6: The state Department of Water Resources outlines its plans for repairs and replacement of the Oroville Dam spillway by Nov. 1, with the undamaged top chute as the priority.

April 25: For the first time since the crisis began, members of the state Legislature pepper key water leaders with questions about what happened, what will happen next and what can be learned from it all. Despite the first legislative grilling, not much new was shared or learned.

April 27: Bill Croyle, the acting DWR director, answers questions and listens during a series of community meetings as residents affected by the spillway debacle step up to a microphone and are heard. A total of seven meetings are completed by May 11.

May 4: The independent board overseeing the repair of the spillway recommends the DWR change its priorities and focus on the damaged bottom chute rather than the top.

May 18: After 100 days of spillway drama, questions remain as work on the spillway continues.