Update 3: Here is the question officials are asking: can they drain the Oroville dam fast enough before the Wednesday storm? As the SacBee writes, water is flowing out of Lake Oroville's main spillway fast enough to cause lake levels to drop by up to 30 feet before the next storm Wednesday night. Officials hope that will be enough. Lake Oroville can fill fast during a big storm. During storms from Monday of last week through Friday, lake levels increased by 50 feet.
The main factor in how fast the lake drains continues to be the condition of the main spillway. Officials said Monday morning that the main spillway had not further deteriorated despite huge outflows cascading over it Sunday afternoon and evening. The more water drained from the lake by the next storm, the less chance that the lake again will fill to the point that activates the emergency spillway. Erosion on the emergency spillway Sunday night created the need to evacuate nearly 200,000 people.
With 100,000 cubic feet per second of water flowing out of the lake, lake levels were dropping about one foot every 3 hours on Monday morning, state figures show. That translates to a drop of about 120,000 acre-feet every 24 hours. At current pace, the lake will fall to about 400,000 acre-feet below its emergency spillway by Thursday morning. To get the lake back to the levels normally mandated for flood control, it would need to fall by about 700,000 acre-feet.
Officials have more modest goals. They said Sunday night that they hope to drain the lake by 20 to 30 feet by the next storm. At current pace, they will hit that target.
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Update 2: Video clip of a flooded park located underwater from the Oroville dam
Update: some good news - according to state officials, an early morning inspection of the battered main spillway revealed that ramping up the water releases did no additional damage to the main release point for the dam. “There’s been no additional erosion on the main spillway,” said Chris Orrock, a state Department of Water Resources spokesman. “We will continue at 100,000 (cfs).”
Orrock added that while giant sandbags are being filled with crushed aggregate at a staging area overlooking the dam, it is still uncertain whether the aggregate will be helicoptered in to try to fix the erosion beneath the emergency spillway.
Bags full of crushed rock sit ready to be dropped into the damaged areas of the Oroville Dam emergency spillway on Monday, Feb. 13, 2017.
The larger rocks in the background are being crushed to fill the bags.
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After discovering a hole in Oroville Dam's emergency spillway, officials said late Sunday that they will attempt to plug it using sandbags and rocks. But, as the LA Times notes, they stressed the situation remains dangerous and urged thousands of residents downstream to evacuate to higher ground. Video from television helicopters Sunday evening showed water flowing into a parking lot next to the dam, with large flows going down both the damaged main spillway and the emergency spillway.
Breaking Here come the choppers to the site with oversized sandbags pic.twitter.com/sNusIXG5Js— Dale Kasler (@dakasler) February 13, 2017
They also showed lines of cars getting out of downtown Oroville. An evacuation center was set up at the Silver Dollar Fairgrounds in Chico.
Almost 200,000 people were ordered on Sunday to evacuate from the area below the Lake Oroville Dam, the tallest dam in the United States, after authorities said its emergency spillway could give way.
While officials said the situation seemed less dire overnight, Sacramento television station KCRA reported that helicopters from around the state were sent to drop chest-high bags of rocks to close the hole in the spillway. The NBC affiliate showed dump trucks dropping off piles of rocks - see below - which were then loaded into the bags with backhoes, while helicopters were deployed to the site with oversized sandbags. The operation to close the gap would begin as soon as it was feasible, the station said.
Officials feared a failure of the emergency spillway could cause huge amounts of water to flow into the Feather River, which runs through downtown Oroville, and other waterways. The result could be flooding and levee failures for miles south of the dam, depending on how much water is released.
The efforts to make repairs to the damaged emergency spillway at the Oroville Dam are a race against time. Forecasters say Monday and Tuesday should be dry. But on Wednesday, more rain is possible. And the wet weather is expected to continue into the weekend. The rain is likely to increase water levels at Lake Oroville. Sunday night, officials were able to send water out of the damaged main spillway, taking pressure off the emergency spillway. Workers plan to make repairs to the emergency spillway beginning Monday.
After five years of drought, Northern California has experienced one of the wettest winters on record.
So to limit the potential damage and flooding, the primary plan of action currently in place is to plug a hole in the emergency spillway, including using helicopters dropping bags of rock into the crevasse to prevent any further erosion. Here's the loud, chaotic scene as the choppers prepare for the rock drop via @judywbrandt on Twitter.
Meanwhile, as the LA Times also adds, the California National Guard is on standby and ready to assist with the Oroville Dam emergency, Adjutant General David Baldwin said during Sunday night's press conference. The California National Guard put out an alert to all 23,000 of its soldiers and airmen telling them to be “ready to go if needed,” Baldwin said. The last time officials sent out such a broad notification was during the 1992 riots in Los Angeles, he said. The California National Guard would deploy eight helicopters to assist with spillway reconstruction; military police would also be deployed to Yuba County, Baldwin said.
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Finally, as noted above, the reason for the scramble to fix the dam is because a new storm system is forecast for later this week put water officials on a race against time. Bill Croyle, the acting director of the state Department of Water Resources, said they planned to continue discharging flows at a rate of 100,000 cubic feet per second, with the hope of lowering the reservoir level by 50 feet.
The biggest concern was that a hillside that keeps water in Lake Oroville — California’s second largest reservoir — would suddenly crumble Sunday afternoon, threatening the lives of thousands of people by flooding communities downstream. With Lake Oroville filled to the brim, such a collapse could have caused a “30-foot wall of water coming out of the lake,” Cal-Fire incident commander Kevin Lawson said at a Sunday night press conference. Luckily, so far this scenario has not played out.