More than 180,000 people downstream of America’s tallest dam, the Oroville Dam, were forced to evacuate their homes earlier this week. Because of the possibility of water spilling over, due to the recent increase of California rain and melting snow.
The problem began earlier this week when operators discovered a hole in the concrete of the main spillway. The hole was “almost the size of a football field and at least 40 feet deep in the main concrete spillway,” according to CNN.
Although the main cause has not been identified, according to the New York Times, “one culprit is cavitation, or tiny bubbles of water vapor that can form in high-velocity water, said Blake P. Tullis, a professor of civil engineering at Utah State University. When the bubbles collapse, they create tiny shock waves that are strong enough to damage concrete, he said.
Once water stopped flowing through the main spillway, officials resorted to plan B, an emergency spillway built nearly fifty years ago when the dam first opened. As water was flowing through the emergency spillway, engineers rushed to temporarily fix the hole by using rocks.
Unfortunately, as water flowed through the emergency spillway it caused major erosion. “Because emergency spillways are seldom used, they are not built to the same specifications as main spillways, and some damage to them can often be expected if they are used,” reported the New York Times.
It was at this time that the evacuation was ordered and pure chaos was unleashed as hundreds of residents rushed to exit the city.
“Any spillway — primary or emergency — usually has some kind of protection, a concrete basin. For structures as big as this, it seems pretty uncommon to not have some protection at the base of the [emergency] spillway,” said Tullis.
Policy director with Friends of the River, Ron Stork claimed he foresaw this event nearly a decade ago according to CNN.
Stork with the Friends of the River, as well as the Sierra Club and the South Yuba Citizens League, filed a motion back in Oct. of 2005 with the Federal Energy Regulatory Commission (FERC) for Oroville Dam’s re-licensing process.
According to CNN, the motion argued that the Oroville Dam “did not meet modern safety standards.” The emergency spillway “was designed to work with a replacement dam that was never built.”
The State Water Contractors and the Metropolitan Water District of Southern California said the FERC “could not require them to pay the damages required for the upgrades,” noted CNN.
Bill Croyle, the current director of California Department of Water Resources, said he was “not familiar with [the] 2005 documentation or conversation” about spillway concerns.
Fortunately, the water level of Lake Oroville has decreased, but California is expecting another major storm soon.
As noted by the Los Angeles Times, “White House Press Secretary, Sean Spicer, said President Trump has been ‘keeping a close eye’ on the Oroville Dam emergency and is working with the Federal Emergency Management Agency to assist state officials.”
Officials are doing everything in their power to not only keep the water level down, but the worrying of residents as well.