The California Department of Water resources this morning issued an update on the giant hole caused by erosion in the Oroville Dam spillway:
SACRAMENTO – As it manages storm inflow to Lake Oroville with a main spillway damaged by erosion, the California Department of Water Resources (DWR) announced late Thursday that the reservoir’s emergency spillway likely will be used, perhaps as soon as the early hours of Saturday.
In that event, total discharges from the reservoir would be consistent with flood control releases at this time of year under these weather conditions. DWR does not expect the discharge from the reservoir to exceed the capacity of any channel downstream as the water flows through the Feather River, into the Sacramento River and on to the San Francisco Bay. Inflow to Lake Oroville was expected to peak late Thursday and begin to decline through the weekend.
Oroville Dam itself is sound and there is no imminent threat to the public, said DWR Acting Director William Croyle.
“We and our many partners are doing everything we can to minimize all risks to the public and the dam,” he said.
Thursday evening operators increased the releases down the damaged, gated spillway from 35,000 cubic feet per second to 40,000 cubic feet per second, with another 7,000 cfs passing through the dam’s hydroelectric power plant outlets. But those discharges are not enough to match an inflow of approximately 192,000 cfs from a storm that stalled over the watershed. The reservoir, at 884 feet elevation above sea level Thursday, will naturally begin to spill into the emergency spillway channel at elevation 901 feet. That point may come shortly after midnight Friday.
The emergency spillway has not been used in Oroville Dam’s 48-year history, but Lake Oroville came within a foot of spilling into it in January 1997.
The emergency spillway is a vegetated hillside near the dam, and should it be used, water would wash away large amounts of soil. In preparation for the possible use of the emergency spillway, trees and brush are being removed from the hillside to minimize any flow of debris into the river. Evacuation of fish from a downstream hatchery is underway to avoid harm to young fish and eggs from turbid water.
DWR is coordinating closely with state and federal wildlife and dam safety officials as it responds to the spillway erosion and manages reservoir operations. Those involved in contingency planning and response include the Federal Energy Regulatory Commission, the U.S. Army Corps of Engineers, Butte County Sheriff’s Office, the Governor’s Office of Emergency Services, the state’s Division of Safety of Dams, CAL FIRE and state and federal wildlife agencies.
Lake conditions, including lake levels, inflows, and outflows can be obtained via a recorded message at 530-534-2307. More information is available at the California Data Exchange Center.
Meanwhile, America Rivers issued a statement pointing out how a Nevada dam failure and the hole in the Oroville Dam Spillway highlight problems with aging dams:
Statement by Bob Irvin, President of American Rivers
February 10, 2017
Contact: Amy Kober, 503-708-1145
Washington – The failure of a dam in northern Nevada yesterday and the appearance of a 30-foot deep hole in the spillway of the nation’s tallest dam – Oroville Dam in California – highlight the crumbling of our nation’s water infrastructure and the danger posed by aging dams.
The earthen Twentyone Mile Dam on Thousand Springs Creek in Elko County, Nevada burst following heavy rains.
On the Feather River in California, erosion created a hole in the concrete spillway of the 770-foot tall Oroville Dam. Nobody was injured in the Nevada dam failure and officials say the hole in Oroville Dam’s spillway does not endanger the integrity of the dam or safety of downstream communities.
According to the Association of State Dam Safety Officials, America’s dams are degrading faster than they are being repaired, the number of high hazard dams has increased over time, and the cost to rehabilitate dams continues to rise.
By 2020, seventy percent of dams in the United States will be more than 50 years old. Aging dams can pose a serious safety threat for individuals and entire communities.
Bob Irvin, President of American Rivers, made the following statement:
“Outdated dams can threaten communities. When they fail, they can destroy lives and property. Thankfully nobody was injured in Elko County, but this event raises the alarm about the danger that aging dams pose to many communities.”
“It is critical we make the right investments to ensure our rivers are healthy and our nation’s water infrastructure is safe. More frequent and intense storms and floods are straining aging dams and other infrastructure.”
“Where appropriate, communities are using dam removal as a solution to address the problem of dangerous, outdated dams,” he said.
American Rivers said that states can strengthen their dam safety programs by:
• Making it the responsibility of dam owners to inspect and maintain their dams
• Requiring more frequent, detailed inspections of hazardous dams
• Increasing penalties for unsafe dams and violations
• Requiring dam owners to ensure that funds are available to repair or remove dams in the event they can’t or won’t meet safety standards.
Photo courtesy of Oroville Dam spillway courtesy of Maven’s Notebook.