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REGIONAL: Work continues at Oroville Dam spillway; crews focus on debris removal, restoring power plant function
NORTHERN CALIFORNIA – State officials said emergency repairs are continuing at the Oroville Dam’s damaged spillway in an effort to restart operations at the dam’s power plant, which provides another outlet for water release at the facility.
On Tuesday, one day after the Department of Water Resources, or DWR, halted flows down the damaged flood control spillway at the dam, crews continue removing a debris pile estimated at roughly 1 million cubic yards at the base of the spillway.
Debris removal will help lower the water level in the channel that leads to Hyatt power plant, officials said.
Bringing down the water height in that channel is a key step to restoring function at the power plant, which will give DWR another means of releasing water from the reservoir.
The forecast for the coming week is relatively dry, and Lake Oroville is not expected to rise above 860 feet elevation while spillway flows are halted for up to seven days.
The lake level still would be 41 feet below the level at which the emergency spillway would be used. The current lake level is 840 feet elevation, with inflows of roughly 20,000 cubic feet per second.
If Hyatt power plant function is not restored within seven days, DWR will use the flood control spillway again to regulate reservoir levels.
In preparation for the restarting of Hyatt power plant, DWR is moving a power line in order to connect the second of three lines needed to enable reoperation of the entire plant. This work is being coordinated with Pacific Gas & Electric Co.
Once operational, the Hyatt power plant can discharge roughly 14,000 cubic feet per second, which will allow state water officials to better manage reservoir levels through the remaining spring runoff season.
On Monday, flows down the flood control spillway gradually dropped from 50,000 cubic feet per second to zero, ceasing around noon.
The cessation of flows has allowed DWR to better assess the extent of erosion on the flood control spillway that was first noticed Feb. 7.
“We’ve been monitoring this spillway closely since Feb. 7, and we knew there was significant damage before we went to zero flows,” said acting state Water Resources Director Bill Croyle. “It’s clear we have a lot of work ahead of us. Work already is underway to repair or replace the damaged spillway so that we are ready for next winter.”
The halt in flood control spillway releases gives workers safe access to the debris pile. Crews are excavating day and night. Excavators, bulldozers and several crane barges are in operation.
Flows necessary to meet fishery requirements in the Feather River downstream of the dam are being maintained at 2,500 cubic feet per second through use of water stored in the diversion pool and Thermalito Forebay and Afterbay. This complex of small reservoirs just downstream of Oroville Dam will provide enough water to maintain flows for approximately seven days.
DWR and the California Department of Fish and Wildlife together are surveying the Feather River downstream of Oroville Diversion Dam to rescue fish that may get stranded in pools as the river level falls.
Adult salmon are not expected to be in the river at this time of year, and young salmon likely have already moved downstream with recent high flows.
Since Feb. 12, Department of Water Resources has reduced water levels in Lake Oroville from 901 feet elevation to 840 feet, more than 60 feet below the top of the emergency spillway.
DWR is coordinating with Caltrans to address the impact of emergency response activities on local roads, and this will continue throughout the operation.
For information on lake conditions; including lake levels, inflows and outflows visit http://cdec.water.ca.gov/cdecapp/resapp/resDetailOrig.action?resid=ORO .