California water authorities will stop the outflow from the Oroville Dam's crippled spillway to allow workers to remove debris blocking a hydroelectric plant from working, officials said Sunday.
The Department of Water Resources said it will start gradually reducing outflows from the Northern California dam beginning Monday morning and completely halt them by the afternoon.
The outflow from behind the 770-foot-tall dam will be stopped for several days to allow workers to clear concrete, silt and other debris from a pool at the bottom of the spillway. Removing the debris will protect a shuttered underground hydroelectric plant and allow it to eventually resume operations, the agency said.
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"Once operational, the Hyatt Power Plant can discharge roughly 14,000 cubic feet per second, which will allow DWR to better manage reservoir levels through the remaining spring runoff season," it said.
The reservoir's water level has been reduced nearly 60 feet since it reached capacity at 901 feet earlier this month, the department said.
The department said it will continue releasing 50,000 cubic feet of water per second the rest of Sunday and overnight. With inflows of water at only 25,000 cubic feet of water per second, more space will be made at the reservoir before the outflows are cut on Monday.
On Feb. 11, water managers used the emergency spillway for the first time in the dam's 48-year-history after a chunk of concrete tore out the main spillway, creating a 200-foot-long, 30-foot-deep crater. But the flow of water ripped through a road below and carved out deep chasms in the ground, leading authorities to order a two-day evacuation of 188,000 people for fear the emergency spillway could fail.
Since then, crews have been working to fortify the badly eroded emergency spillway.