DWR to Stop Spillway Outflow for Debris Removal

An aerial view of the damaged Oroville Dam spillway on February 26, 2017. The dam is 770 feet tall (highest in U.S.) located in the foothills on the western slope of the Sierra Nevada.
Kelly M. Grow/ California Department of Water
Resources

February 27, 2017 – At 6:45 a.m. today, the Department of Water Resources (DWR) began gradually ramping down outflows from the Oroville Reservoir. Flows from the flood control spillway will be reduced from 50,000 cubic feet per second throughout the day and eventually reach zero in the afternoon.

As flows are reduced, DWR will monitor the status of the dam, spillways, and related structures to ensure their continued safety and stability. Flows will be reduced gradually to minimize risk to downstream levees. Through use of water stored in the Diversion Pool and Thermalito Forebay and Afterbay, flows necessary to meet fishery requirements in the Feather River downstream of the dam will be maintained.

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Cutting off flow from the flood control spillway for several days will allow workers to aggressively remove the debris pile at its base and reduce the water level surface elevation of the Hyatt Powerplant tailrace channel. The Lake level has decreased to 838 feet, 63 feet below the maximum level of the reservoir. The inflow has decreased to about 22,000 cfs and is expected to continue to decrease during the week. The lake elevation is expected to rise less than 15 feet during the zero-spillway-flow period. Spillway flow will resume later in the week.

Work continues in the area below the emergency spillway, on access roads, and in the various eroded areas created by emergency spillway runoff. Construction crews are now installing foundations for check structures that would slow water flows should the emergency spillway be required. Excavation equipment on barges will begin debris removal below the flood control spillway in the Diversion Pool this afternoon. This work will continue 24 hours a day.