Lake Oroville surges over emergency spillway for first time in history

Lake Oroville surges over emergency spillway for first time in history

by Dan Bacher

Water from Lake Oroville flowed over the emergency spillway at Oroville Dam for the first time in the reservoir's 48-year history after the water level exceeded 901 feet in elevation shortly after 8 a.m. today.

The water slowly began to flow over the concrete weir of the auxiliary spillway, down a hillside and into the Feather River, a major tributary of the Sacramento River, the state’s largest river.

The flow over the auxiliary spillway has been between 6,000 and 12,000 cubic feet per second (cfs), according to an update from the California Department of Water Resources (DWR) at 10:14 am. on February 11.

Agency officials expect these flows to go into the auxiliary spillway for 32 to 58 hours, based on the latest modeling of weather, reservoir inflow and other factors. There is "no danger to dam or people" from the flows, according to DWR.

In a news briefing today, DWR Acting Director William Croyle said dealing with the damage caused by the growing hole in the dam's primary spillway could cost $100 to $200 million.

Croyle said the damaged spillway will need "complete replacement," noting that the current structure is "toast all the way to the bottom."

“The flows we’re seeing are extremely low compared to the design of the structure,” said Croyle. “Based on our current situation, there is no threat.”

In a statement earlier today, DWR said the volume of water "is expected to pose no flood threat downstream and should remain well within the capacity of the Feather River and other channels to handle. Oroville Dam itself remains safe, and there is no imminent threat to the public."

"The emergency spillway has not been used since the dam was finished in 1968, but DWR has anticipated and prepared for its use since Tuesday, when erosion opened a cavity on the concrete, gated spillway typically used in winter operations at Lake Oroville," the agency said. "DWR continues to use that damaged spillway to discharge 55,000 cubic feet per second, but the approximately 95,000 cfs inflow to the lake exceeds that discharge. As of 4 a.m., the lake level was .7 feet away from the 901 foot elevation at which water flows over a concrete weir and into the unlined emergency spillway."

The agency noted that DWR and CAL FIRE crews in past days have been clearing trees and brush from the path water is expected to take in the emergency spillway, an unlined hillside. The emergency spillway flows are expected to wash large amounts of soil and debris into the Feather River, and crews are positioned to remove as much debris as possible from the channel immediately downstream of the dam.

"The total flow of water from the reservoir, including the emergency spillway, is expected to be on the order of half of downstream flood system capacity and consistent with releases made at this time of year in wet years such as this. While DWR does not expect flows to exceed downstream channel carrying capacity, the rate of flow into the ungated emergency spillway may change quickly," DWR said.

In a tweet this morning, Peter Gleick, President Emeritus and Chief Scientist of the Pacific Institute, pointed out, "Oroville Dam inflow continues to exceed controlled outflow. Reservoir will rise until flow over emergency spillway equals inflow."

Late yesterday afternoon, over 50 staff from the California Department of Fish and Wildlife completed a rescue of 8 million young salmon and 1 million eyed steelhead eggs at the Feather River Fish Hatchery.

Hatchery staff using 8 trucks relocated the 6.5 million fall-run and spring run Chinooks to the hatchery annex near the Thermalito Afterbay, according to Andrew Hughan, CDFW spokesman. These fish, approximately 1 inch long each, would die from suffocation in the turbid, sediment-laden water if left in the raceways of the hatchery.

Approximately 1.5 million juvenile salmon will remain in the hatchery where they will be benefit from sediment ponds set up to cleanse the water. Engineering staff have also set up a charcoal filtration system utilizing a fire hydrant pump for the 1 million eyed steelhead eggs remaining in the hatchery.

“Right now we consider our rescue operation to be a good success,” said Hughan. “We brought in staff from hatcheries all over the state to help in this emergency effort.”

For more information on the fish rescue, go to: http://www.elkgrovenews.net/2017/02/cdfw-rescues-8-million-young-salmon-1.html

Critics of the Delta Tunnels project said the Oroville Dam spillway rupture shows how basic dam assessments, management plans, and maintenance are being neglected as Governor Jerry Brown constantly promotes the California WaterFix as the "solution” to the state’s water supply and ecosystem problems.

“According to the American Society of Engineers 2013 Report, there are 678 high hazard dams in California, and 48% of them do not have an emergency plan,” said Barbara Barrigan-Parrilla, executive director of Restore the Delta, responding to the Oroville Dam rupture on February 8. “Watching the damage unfold at Oroville, it is striking to us that Governor Brown, CA WaterFix proponents, and Department of Water Resources leaders keep telling Californians that the tunnels are the needed fix for updating California’s water delivery system, yet basic dam assessments, management plans, and maintenance are forgotten or put off."

“The Federal Government had indicated that Oroville Dam needed a further seismic assessment, but the Department of Water Resources stated in 2013 that a seismic assessment of Oroville Dam was not needed. What would happen if an earthquake were to happen near the dam today during this high water event?” she asked.

For more information, go to: http://www.dailykos.com/story/2017/2/8/1631621/-Giant-cavity-opens-in-Oroville-Dam-spillway-as-Jerry-Brown-focuses-on-Delta-Tunnels

Lake conditions, including lake levels, inflows, and outflows can be obtained via a recorded message at 530-534-2307. More information is available here at http://cdec.water.ca.gov/cdecapp/resapp/resDetailOrig.action?resid=ORO.