TIMELINE: What Happened at the Oroville Dam

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OROVILLE — Here’s a timeline of events surrounding problems related to the Oroville Dam and its spillway.

January 13 — Record rainfall in the Feather River watershed leads the state Department of Water Resources to make reservoir releases from Lake Oroville of up to 10,000 cubic feet per second (cfs).

January 31 — Flows through the main spillway increase to more than 10,000 cfs as runoff into the river increases.

February 7 — Reservoir releases through the main spillway were increase to 54,500 cfs to offset higher inflows from rainfall. DWR discovers a large amount of debris coming out of the concrete-lined spillway and stops all releases to inspect the damage. Engineers discover a massive crater. Authorities decide to use the crippled spillway, but with reduced flows.

DWR continues to assess the concrete erosion on the Oroville Dam spillway. No imminent threat to the dam or public. (Photo Courtesy: CA - DWR)
DWR continues to assess the concrete erosion on the Oroville Dam spillway. No imminent threat to the dam or public. (Courtesy: CA – DWR)

February 11 — The water elevation in Lake Oroville reaches 901 feet, its full capacity, leading water to flow over the emergency spillway for the first time in its nearly 50-year history.

Water flows over the Oroville Dam's emergency spillway for the first time in the dam's history (Courtesy: DWR)
Water flows over the Oroville Dam’s emergency spillway for the first time in the dam’s history (Courtesy: CA – DWR)

February 12 — Erosion begins to progress up the right side of the emergency spillway. Fearing the ground will collapse underneath a concrete slab holding water in the reservoir, authorities order a mandatory evacuation of 188,000 people in towns downstream. DWR increases the primary spillway releases to 100,000 cfs to draw down the water level. Within hours, water stops flowing over the emergency spillway so experts can assess the erosion.

February 13 — Crews begin working around the clock to repair the eroded areas below the emergency spillway. Almost 200,000 people remain under evacuation order.

February 14 — Water levels in Lake Oroville continue to drop. Authorities lift the mandatory evacuation order but ask residents to be prepared in case of another evacuation.

February 15 — Dump trucks and helicopters for a second day drop thousands of tons of rocks and sandbags to shore up the emergency spillway. Lake Oroville’s water levels had dropped by 26 feet.

February 16 — Officials reduce the flow of water below 100,000 cfs for the first time since Sunday, allowing them to clear debris from the bottom and prepare to restart the dam’s hydroelectric power plant.

February 18 — Lake Oroville water levels have continued to drop in preparation for the upcoming storms and, as of 4 p.m., were at 854 feet. The main spillway outflow has been brought down to 55,000 cubic feet per second. This is to allow crews to conduct debris removal at the diversion pool near the flood control spillway. A barge is being constructed so that equipment can be brought out to dredge up debris and sediment.

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February 19 — Outflow from the main spillway was increased at 2 p.m. from 55,000 cfs to 60,000 cfs. This should help the DWR to balance the water flowing into and out of the reservoir. Elevations of Lake Oroville were at 851.02 feet at 7 a.m., according to the Marysville Police Department.

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