02-11-2017, 07:05 PM
Oroville Dam’s untested emergency spillway activated. Flows to continue ‘40 to 56 hours’
Water began pouring over the emergency spillway at Oroville Dam early Saturday for the first time in its 48-year history.
State officials continued to say they don’t expect the situation to result in flooding in Oroville or other communities downstream.
Unable to release enough water from the dam’s heavily damaged main spillway, officials with the California Department of Water Resources announced that water from the swollen reservoir started flowing over the adjacent emergency spillway at around 8 a.m. Department spokesman Doug Carlson said water was flowing over the emergency structure at 5,000 to 10,000 cubic feet per second.
Carlson said engineers expect flows from the emergency spillway to continue at 5,000 to 10,000 cubic feet per second “for 40 to 56 hours, based upon current modeling.”
At that point, with dry weather in the near-term forecast for the Sierra watershed that feeds the reservoir and inflows to the lake slowing, it’s expected that the uncontrolled releases from the emergency spillway will end and the lake level will start dropping, Carlson said.
Sometime in the next few days, the department expects the reservoir will recede to 890 feet, or 11 feet below the lip of the emergency spillway, Carlson said.
Although the flows from the spillway started out slowly, at around 600 cfs, the water was already churning up debris from the unlined, heavily wooded hillside.
“There is a fair amount of debris in the diversion pool at the bottom of the dam,” Carlson said, referring to the body of water that leads to the Feather River.
Cal Fire spokesman Mike Smith said DWR officials had laid out floating structures known as booms in the waterways to catch debris. Work crews had spent the last two days removing some of the trees from the hillside in anticipation of water going over the emergency spillway.
“DWR is confident that there should be no flooding,” Smith said. He added that the levees and channels downstream could “handle roughly twice the flows” that the releases were expected to produce.
The battered main spillway, which developed a pothole this week that has ballooned to a 300-foot gash, continued to release 55,000 cfs of water. That meant a total of 60,000 to 65,000 cfs was pouring out of the dam. About twice as much water was released from the dam during the 1997 storms, which produced considerable flooding in Yuba and Sutter counties after several levees broke. Since then, hundreds of millions of dollars have been spent upgrading levees and other flood control facilities.
“I don’t believe we’re in an emergency situation in terms of flooding,’’ said Butte County Sheriff Kory Honea as he entered DWR’s regional office a few miles from the dam. But he urged residents to stay alert “if the situation changes and there is need for additional response.” Residents can call 530-538-7826 for updates.
Ironically, the water began flowing over the emergency spillway as Oroville enjoyed its first sunny morning in days. The sky was completely blue, and officials said they hoped a spell of dry weather would continue to diminish the volume of water flowing into Lake Oroville from the Sierra watershed.
Eric See, a DWR spokesman, said the releases from the emergency spillway were expected to continue fluctuating between 5,000 and 10,000 cubic feet per second, with wind currents rippling across the lake affecting how much water gets pushed over the concrete lip of the 1,700-foot-wide spillway.
“It’’s going to go up and it’s going to go down,” See said.
He said downstream residents should expect the Feather River to run high but not cause flooding. “This is not a flood event,” he said. “We had more water than this in 2006,” the last time officials around Oroville were warning of significant problems.
During the January 1997 floods, which caused fatalities and significant destruction further downstream in Yuba and Sutter counties, the Feather was running at around 160,000 cfs, he said. He said the Feather shouldn’t flow any stronger than 75,000 cfs during this event.
State officials had hoped to prevent use of the emergency spillway for the first time since the reservoir was built in 1968. While it has a concrete lip, the spillway leads to a heavily wooded ravine. Releasing water through the spillway would likely bring fallen trees, dirt and other debris cascading into the Feather River.
Two independent experts interviewed by The Sacramento Bee agreed with state officials that the situation posed no immediate threat to the integrity of the dam. But they also said erosion is an ongoing concern.
Early Friday, DWR officials had expressed confidence that they could avoid the emergency option. Despite a huge pothole in the dam’s main concrete spillway that was discovered Tuesday, engineers had ramped up water releases to 65,000 cubic feet per second early Friday morning.
With rains letting up, and inflows into lake subsiding, they believed they could keep the water level behind the dam to below 901 feet.
But Friday at about 8 p.m. they had to throttle back the water releases to 55,000 cfs to prevent erosion along the side of the main spillway from “compromising” the power line towers that link to the dam’s power plant.
Even though inflows have fallen to 95,000 cfs - or about half what they were about 36 hours earlier - the crippled spillway has struggled to keep up.
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[url=http://www.sacbee.com/news/state/california/water-and-drought/article132122669.html]Water continues to rush down Oroville spillway on Friday
The Department of Water Resources said it planned to slow releases from Oroville Dam’s damaged main spillway “to prevent erosion along the north side of the spillway from compromising nearby power line towers.” The lines run to the dam’s power plant.
Video by Randall Benton, Produced by Sue Morrow The Sacramento Bee
Water began pouring over the emergency spillway at Oroville Dam early Saturday for the first time in its 48-year history.
State officials continued to say they don’t expect the situation to result in flooding in Oroville or other communities downstream.
Unable to release enough water from the dam’s heavily damaged main spillway, officials with the California Department of Water Resources announced that water from the swollen reservoir started flowing over the adjacent emergency spillway at around 8 a.m. Department spokesman Doug Carlson said water was flowing over the emergency structure at 5,000 to 10,000 cubic feet per second.
Carlson said engineers expect flows from the emergency spillway to continue at 5,000 to 10,000 cubic feet per second “for 40 to 56 hours, based upon current modeling.”
At that point, with dry weather in the near-term forecast for the Sierra watershed that feeds the reservoir and inflows to the lake slowing, it’s expected that the uncontrolled releases from the emergency spillway will end and the lake level will start dropping, Carlson said.
Sometime in the next few days, the department expects the reservoir will recede to 890 feet, or 11 feet below the lip of the emergency spillway, Carlson said.
Although the flows from the spillway started out slowly, at around 600 cfs, the water was already churning up debris from the unlined, heavily wooded hillside.
“There is a fair amount of debris in the diversion pool at the bottom of the dam,” Carlson said, referring to the body of water that leads to the Feather River.
Cal Fire spokesman Mike Smith said DWR officials had laid out floating structures known as booms in the waterways to catch debris. Work crews had spent the last two days removing some of the trees from the hillside in anticipation of water going over the emergency spillway.
“DWR is confident that there should be no flooding,” Smith said. He added that the levees and channels downstream could “handle roughly twice the flows” that the releases were expected to produce.
The battered main spillway, which developed a pothole this week that has ballooned to a 300-foot gash, continued to release 55,000 cfs of water. That meant a total of 60,000 to 65,000 cfs was pouring out of the dam. About twice as much water was released from the dam during the 1997 storms, which produced considerable flooding in Yuba and Sutter counties after several levees broke. Since then, hundreds of millions of dollars have been spent upgrading levees and other flood control facilities.
“I don’t believe we’re in an emergency situation in terms of flooding,’’ said Butte County Sheriff Kory Honea as he entered DWR’s regional office a few miles from the dam. But he urged residents to stay alert “if the situation changes and there is need for additional response.” Residents can call 530-538-7826 for updates.
Ironically, the water began flowing over the emergency spillway as Oroville enjoyed its first sunny morning in days. The sky was completely blue, and officials said they hoped a spell of dry weather would continue to diminish the volume of water flowing into Lake Oroville from the Sierra watershed.
Eric See, a DWR spokesman, said the releases from the emergency spillway were expected to continue fluctuating between 5,000 and 10,000 cubic feet per second, with wind currents rippling across the lake affecting how much water gets pushed over the concrete lip of the 1,700-foot-wide spillway.
“It’’s going to go up and it’s going to go down,” See said.
He said downstream residents should expect the Feather River to run high but not cause flooding. “This is not a flood event,” he said. “We had more water than this in 2006,” the last time officials around Oroville were warning of significant problems.
During the January 1997 floods, which caused fatalities and significant destruction further downstream in Yuba and Sutter counties, the Feather was running at around 160,000 cfs, he said. He said the Feather shouldn’t flow any stronger than 75,000 cfs during this event.
State officials had hoped to prevent use of the emergency spillway for the first time since the reservoir was built in 1968. While it has a concrete lip, the spillway leads to a heavily wooded ravine. Releasing water through the spillway would likely bring fallen trees, dirt and other debris cascading into the Feather River.
Two independent experts interviewed by The Sacramento Bee agreed with state officials that the situation posed no immediate threat to the integrity of the dam. But they also said erosion is an ongoing concern.
Early Friday, DWR officials had expressed confidence that they could avoid the emergency option. Despite a huge pothole in the dam’s main concrete spillway that was discovered Tuesday, engineers had ramped up water releases to 65,000 cubic feet per second early Friday morning.
With rains letting up, and inflows into lake subsiding, they believed they could keep the water level behind the dam to below 901 feet.
But Friday at about 8 p.m. they had to throttle back the water releases to 55,000 cfs to prevent erosion along the side of the main spillway from “compromising” the power line towers that link to the dam’s power plant.
Even though inflows have fallen to 95,000 cfs - or about half what they were about 36 hours earlier - the crippled spillway has struggled to keep up.
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[/url]
[url=http://www.sacbee.com/news/state/california/water-and-drought/article132122669.html]Water continues to rush down Oroville spillway on Friday
The Department of Water Resources said it planned to slow releases from Oroville Dam’s damaged main spillway “to prevent erosion along the north side of the spillway from compromising nearby power line towers.” The lines run to the dam’s power plant.
Video by Randall Benton, Produced by Sue Morrow The Sacramento Bee