Dam failure in California: Oroville accident. Causes and consequences

An emergency incident with the simultaneous destruction of all spillways of a dam in Oroville, California, served as a striking example of the emergence of a large problem due to a small but systematic oversight. Destructive processes that were not identified in time by the responsible services ultimately led to a serious threat and the need for the rapid evacuation of hundreds of thousands of people, the deployment of colossal forces to eliminate the accident and the expenditure of hundreds of millions of dollars on the operation. Until the situation reached a catastrophic stage - the water did not break the dam, but it revealed the problems of the existing system for maintaining hydraulic structures, and destroyed the guarantees that a real tragedy would not occur in any region of the world.

What is a California dam?

Oroville Dam is the highest in the United States. The height of its ground part reaches 235 meters. The dam is located on the Feather River (a tributary of the Sacramento River). A rock dam with a clay core forms the Oroville Reservoir, with a surface area of 10,200 square kilometers and a water volume of 4.3 cubic kilometers.

The reservoir itself is part of a complex that includes a hydroelectric power station with a capacity of 819 MW with six generators, a Hyatt power plant, a Thermalito pump-generator station, and a fish factory. The main objectives of the complex are water supply to the region, flood control and electricity generation. The facility was built in 1961–1968.

The complex's structures are located on the right side along the river. The object closest to the dam is an operational spillway (a tray made of reinforced concrete) for operation in normal water conditions. Even further to the right is an emergency discharge in case of catastrophic floods. Until the February incident, it was not used because there were no such floods. According to statistics, large-scale floods in this region can occur no more than once every ten thousand years.

The fault looks like a hundred-meter wall with a height of 10–20 meters. The incoming water must overflow without regulation, and its layer will be tens of centimeters. Further, at the junction with the right bank of the valley, there is a blind section of the dam with a height of up to 30 meters.

Chronology of the incident

Since the beginning of 2017, water levels in the Oroville Reservoir have been rising at an exponential rate. However, the record belongs to the summer of 1983, but no emergency situations were observed then. In January 2017, the amount of precipitation in the region exceeded the norm three times. Since the beginning of February, the weather has been extremely warm, even at night it did not fall below 10 degrees Celsius.

Already on February 7, a large washout was discovered in the middle part of the spillway. The karst failure, as experts from the CIS believe, occurred due to leaching of the rock base. While repairmen were inspecting the damage, water in the reservoir was rapidly accumulating. When it reached a critical point, which already threatened the safety of the dam itself, emergency crews left the failure area and directed the water through the discharge.

The consequences were not long in coming. The concrete fastening at the bottom of the structure was destroyed, after which the water began to wash away the rock underneath the drain. The destructive process began at the moment of water consumption at the level of 1.4 thousand cubic meters per second. For comparison, in 1997 the dam passed a flow of 4 thousand cubic meters per second without problems. The gap reached a size of 150 by 90 meters and a depth of 14 meters.

The engineers who identified the problem expected that the structure would collapse at any moment, so they reduced the water flow by 15%, using an emergency discharge that had not been used previously, and by February 10 it turned out that the soil foundation of the backup drain was also damaged, and the reason was the loss of integrity It was not possible to find out the object.

The flow of water carried rock fragments into the riverbed, so it was necessary to stop the operation of the hydroelectric power station, otherwise, due to backwater, it could be flooded. Meanwhile, the rupture pit on the main fault expanded, destroying its walls and eroding the adjacent slope. The situation at the emergency drainage has become critical. The decision was made to resume increased flow through the main spillway, despite the threat of loss of control of the dam due to possible failure of the flow.

Accident response and preventive measures

Since the threat of destruction of the dam infrastructure, California Governor Jerry Brown has asked President Donald Trump to send federal resources to deal with the emergency. In his address, the official noted that assistance should also be provided to the districts where residents evacuated from possible flood zones are located.

On Monday, February 13, the Governor of California declared a state of emergency in the region, covering three counties - Yuba, Sutter and Butte. State National Guard units were put on alert. The White House reported that the president has entrusted the coordination of emergency response efforts to the Federal Emergency Management Agency of the Department of Homeland Security. In addition, the country's Ministry of Defense also joined the work. Pronedra wrote earlier that Trump also declared a state of emergency in the disaster zone.

The Russian side immediately offered its help. The Center for Development of the Water Economy Complex of the Ministry of Natural Resources of the Russian Federation stated that domestic specialists can work on solving the problem of the emergency condition of the dam, including by providing appropriate scientific advice. Such tasks are not new to Russians; Moscow has already provided assistance in similar emergencies to countries in Africa and Southeast Asia.

Large forces were put on alert in the United States - a total of about 20 thousand military personnel. 125 construction crews and four dozen heavy vehicles were sent directly to the work area. Aviation was involved, including helicopters of the National Guard, with the help of which they began to drop bags of sand and rock at the sites where the drain was washed out. Barriers made of sandbags are also being erected around the dam. Every hour, about 1.2 thousand tons of rock fragments are placed in the gullies.

The state authorities informed that the work carried out by February 15 made it possible to stop the development of the catastrophic situation, and the expected storm with precipitation was not as significant as expected. In general, the cost of priority measures was estimated at $200 million. It is not yet known how the condition of the spillways will affect the further operation of the dam. Work continues. Thanks to the measures taken, the dam is already able to accommodate additional influx of water. Currently, the volume of discharge is 2.8 thousand cubic meters per second, while the rains do not stop and will continue for several more days.

According to RusHydro, measures are being taken to reduce the reservoir level by 2.5 meters per day in order to safely receive the upcoming precipitation. Debris is being removed in the riverbed to prevent possible flooding of hydroelectric power station structures. The launch of the station's capacity will make it possible to relieve some of the operational discharge. If the latter is subject to restoration, it will be repaired. If repair work is impossible, a new spillway will be built. It is possible that it is necessary to strengthen the emergency discharge slope with concrete and generally evaluate the possibility of its use in the future.

Evacuation, panic and looting

After information from the California Department of Water Resources appeared about the threat of an imminent dam failure (it later turned out that the forecasts were unjustifiably exaggerated), state authorities decided to evacuate the local population. By February 13, a total of 188 thousand people were removed or left on their own from the cities of Yuba City, Gridley, Olivehurst, Plumas Lake, Wheatland, Marysville and Live Oak. But along the route of the evacuees there were colossal traffic jams. Temporarily resettled citizens were placed in different areas at a distance of 32–120 kilometers from the possible flood zone.

Conflicting statements by officials, in particular the emergence of information about the possible destruction of the dam in a matter of hours, played a significant role in the emergence of panic. Already on February 15, the evacuated residents were told that they could return to their homes, although it was noted that the threat of flooding still remained and citizens might have to leave the dangerous area again. Citizens who returned to their homes faced the consequences of looting in their cities. Such reports also came from Oroville, where, in the absence of residents, mass thefts occurred in abandoned stores.

Forecast for the development of the situation in the near future

The state authorities initially took a pessimistic position in terms of forecasting developments. The California Department of Water Resources admitted that if the dam structure is damaged, the forecast could be unfavorable. According to local police, who interviewed experts in the field of hydraulic engineering, a hole in the spillway could threaten the integrity of the entire dam. However, experts emphasize that dams using concrete components are usually less susceptible to erosion processes.

However, if the structure is damaged, this can also lead to its collapse. The Russian Institute of Hydraulic Engineering and Energy Construction believes that the dam can survive if excess water flow is released through open gates. A disaster is potentially possible if the spillway is not functioning.

The most dire forecasts appeared on February 11, when state authorities announced that the water level in the river would rise to critical levels due to a possible dam failure. Although it was announced the next day that the threat had passed, on February 13, reports of the threat of the dam collapsing again appeared. The negative scenario provides for the speed of wave propagation in flat terrain within 25 kilometers per hour, in mountainous terrain - up to 100 kilometers per hour. It is stated that the height of the breakthrough wave for small reservoirs with a water volume of up to 50 million cubic meters will be up to one meter, but in the case of Oroville, whose capacity is eight and a half times greater, the wave will reach a height of up to nine meters.

Let us remind you that in this case, six settlements with a total population of up to 200 thousand people will be in the flood zone. In turn, RusHydro noted that as of February 12, when signs of active rock erosion were noticed on the slope below the emergency discharge, a certain threat arose for residents of the region. If the overflow wall collapsed due to intense erosion, it could cause an uncontrolled discharge of a layer of about 12 meters of the reservoir in height.

There are also alternative points of view. Forecasting for the coming days is a difficult matter, according to hydraulic engineers from the CIS, interviewed by journalists. It is more likely that the dam will remain unharmed, while the spillways - both the main and the emergency ones - will be washed out to the point of complete destruction, but no noticeable damage will be caused to the population and infrastructure. The overflow through the dam will stop after some time, or the process of erosion of the spillway will take place over a long period - within one month, which will not cause sudden changes in the situation and the problem will not become more complicated.

RusHydro believes that current data gives grounds to assert that there is no threat of destruction of the dam, but the spillway structures are in disrepair. The crest of the dam is located six meters above the emergency discharge mark, therefore an emergency overflow of water is also excluded. If the drainage erosion moves to the spillways themselves, then the latter will probably be destroyed. The pit immediately near the spillway stopped actively expanding, reaching the rocky base after the weak rocks were washed away.

Meanwhile, after the accident at one dam, other “hot spots” in California were simply forgotten. Reservoir overflow due to heavy rainfall is a problem not only at the Oroville Dam, but also at most hydraulic structures in the California Valley. The situation on the Sacramento River near the city of the same name is causing concern. The river dam is showing signs of deformation after prolonged exposure to flowing water. Some water has already leaked through the dam and entered the city park, which is located near the river. In addition, a threatening situation is observed in the area of the dam on the San Joaquin River.

In addition, the water level at the Don Pedro Reservoir dam has almost reached the upper edge of the structure. If a snow storm hits the Sierra Nevada Mountains in eastern California, flooding may be inevitable. To prevent the destruction of these structures, the state authorities decided to deliberately destroy the dam on the Moklamne River, which led to the flooding of nearby agricultural land, but reduced the threat of large-scale accidents.

Possible versions of the causes of the accident

Possible problems with the dam became known long before the February accident in 2006. Even then, experts discovered minor violations of the integrity of the main spillway, but the facility was declared suitable for operation. Major repair work on the dam has not been carried out for half a century - from the day it was put into operation. For the last decade, the dam has been operating under a temporary license. Probably, the reason for the uncertain status of the dam is associated with the attempt to obtain a permit for a period of 50 years by the Californian authorities and the subsequent reaction of social activists.

In 2005, a group of activists representing environmental organizations - the South Yuba Citizens League, Sierra Club and Friends of the River - demanded that officials reinforce the emergency discharge with concrete instead of an earthen foundation. The joint letter from the organizations argued that during winter rains, water will begin to overflow the main spillway, which will ultimately lead to erosion, further destruction of structures and flooding. Proposals were submitted to the Presidential Administration and the Federal Energy Regulatory Commission, but they, based on the findings of the California Department of Water Resources that such work was inappropriate, rejected the initiative. According to the authors of the letter, the authorities simply decided to save money, since strengthening the emergency spillway with concrete would have cost millions of dollars. Now the department says the cause of erosion on the drainage drains is unknown.

Like any serious threat, the situation with the risk of dam collapse has already become overgrown with rumors and exotic theories. In particular, it is assumed that a possible disaster was deliberately provoked in order to smooth out the discontent of the population of California, the majority of whom voted for Hillary Clinton in the presidential election. A great misfortune can unite a nation and eliminate political differences. In addition, it should be taken into account that California social activists are actively calling for the separation of the region from the United States.

Proponents of the conspiracy theory believe that the failure of the main spillway was controlled and was the result of sabotage - the leak arose by interfering with the work of the already worn-out infrastructure. In addition, there were statements that rescue services carried out exercises several years ago, during which they practiced actions in the event of a dam collapse. Moreover, the almost exact date of the possible event was already specified in the maneuver scenario.

If we talk about real facts, then RusHydro, which analyzed the development of the emergency situation and possible preconditions, came to a number of conclusions. It is noted that the destruction of the operational spillway occurred suddenly, and the water flow levels were not at all maximum. Thus, we should talk about an insufficient degree of control over the condition of the hydraulic structure, which did not allow timely detection of damage, the company noted.

It is difficult to call the design solution itself correct, associated with the discharge of water masses onto an ordinary unequipped slope. Spillways must undergo mandatory testing. However, it must also be noted that the safety margin of the dam turned out to be sufficient, despite the fact that accidents occurred at both spillways. Thus, large hydraulic structures can generally be considered reliable structures, the company noted.

Regardless of what the results of the accident investigation turn out to be, it is obvious even to non-specialists that, if we do not take into account dubious theories of sabotage or sabotage, the unsatisfactory condition of both spillways was most likely the result of ordinary negligence of the services, which did not timely track the process of structural damage due to natural wear processes. The lack of preventive measures almost caused a large-scale tragedy, and for the happy outcome of the situation we can only thank the reliability of the dam itself, which acted as insurance against the negligence of industry services.

The California Department of Water Resources tweeted that the dam could break within an hour. The main spillway has already been destroyed. The spare spillway may also not be able to withstand the water pressure, the clock is ticking.

Residents should avoid traveling north toward Oroville, officials said.

According to official data, almost 190 thousand people were evacuated. California authorities have also begun to take action to reduce water levels in Lake Oroville. In order to fill the hole in the auxiliary spillway and prevent further destruction, rescue services intend to drop stones from helicopters.

The Butte County Sheriff also announced evacuations. He asked people to leave the area near the lake, as well as the area where water could flow if the dam breaks.

Due to the evacuation, the timing of which has not yet been announced, traffic jams for many hours formed on California roads. Emergency services are addressing these issues, noting that in a worst-case scenario, people's lives would be in real danger. At the same time, they noted that the situation is developing very rapidly.

Fire Rescue Chief Kim Zagaris said at least 250 law enforcement officers from across California are on the scene or en route to the dam area to prevent unrest and ensure the safety of evacuating citizens.

Despite reports of looting in Oroville, city police deny this information. A representative of the city's law enforcement agencies claims that the absence of looting is confirmed by the leadership of the local police department.

The danger of a dam failure arose due to powerful flows of water caused by heavy rains. On Saturday, February 11, water began to overflow through the reserve spillway, and then through the main one. The emergency release of water caused severe soil erosion, which could lead to dam failure. Although experts do not expect complete destruction of the structure, the consequences could lead to the uncontrolled release of a significant amount of flood water. The volume of water in the lake is estimated at more than 4.3 billion cubic meters.

Last Friday, California Governor Jerry Brown asked the Federal Emergency Management Agency to declare a major disaster possible due to flooding and landslides.

Construction of Oroville Dam, which began in 1962, was completed in 1968. The 230-meter-high hydraulic structure is the largest in the United States. Downstream from the dam there is a city of the same name with a population of more than 16 thousand people.

Russian experts note that a dam failure could lead to casualties.

Dam in Oroville California burst.

The destruction of a dam in California is being monitored from helicopters. Millions of viewers watch online as specialists try to patch up a huge hole.

US dam collapses latest news

The California National Guard is on full alert to assist authorities and the public in responding to a possible disaster in the event of a dam failure at Lake Oroville. This was announced on Monday by US Department of Defense spokesman Jeffrey Davis.

There are about 23 thousand National Guardsmen stationed in California. As a Pentagon spokesman assured, “all units” in this state are “on alert” in case of flooding. Personnel are “ready to take action” if the dam is breached, he added.

The governor of the US state of California, Jerry Brown, asked US President Donald Trump for help. It is needed by 188 thousand residents affected by the destruction of the tallest dam in the United States.

Nearby homes in Oroville were evacuated due to concerns that the dam's emergency spillway could not cope with the pressure.

One of the most populous states in America is now under threat of flooding. The Lake Oroville Dam is watched live by millions of viewers. They are trying to patch up the dam in which a giant hole was discovered. If the dam breaks, a huge mass of water will cover several cities at once.

I think this is what they call “one step away from disaster.” The footage filmed by television cameramen from helicopters is impossible to watch calmly. And it seems that even engineers can no longer say what holds all this mass of water in the concrete pool.

California Governor Jerry Brown earlier Monday declared a state of emergency in three counties - Sutter, Butte and Yuba. Butte County Sheriff Coney Honey said at a news conference that the lake's water level was "noticeably decreasing, but the evacuation order remains in effect." According to preliminary information, this order affects 188 thousand people.

USA dam in Oroville destruction photo

Dam in Oroville California breach

Kevin Lawson, head of the emergency headquarters: “We are dropping rock from helicopters. We are trying to fill this hole with stones to reduce the water pressure on the remaining parts of the dam and prevent a disaster.”

The threat of collapse is caused by the fact that a hole the size of a football field has formed in the main drainage channel of the dam, and the backup channel has been damaged by erosion. The State Water Resources Management Department redistributes flows through drainage systems in an optimal manner, and also takes measures to reduce water levels in the lake. A plan has already been prepared to use helicopters to drop rocks to the damaged section of the main drainage drain to fill the gap.

A dam failure in California could lead to uncontrollable consequences, warns professor and academician of the Russian Academy of Natural Sciences Alexander Solovyanov, deputy director of the All-Russian Research Institute for Nature Conservation.

Professor Solovyanov emphasized that a similar situation arose during the accident at the Sayano-Shushenskaya hydroelectric power station. And if the dam finally breaks, then four million cubic meters of water will simply not be stopped.

In addition, the debris of the dam itself in this case will pose a separate danger.

Russian water management specialists are ready to provide assistance to the United States in connection with the destruction of the dam, said Ilya Razbash, head of public relations and media at the Center for Development of the Water Industry Complex of the Russian Ministry of Natural Resources.

“If there is a need, Russian specialists will be able to provide the necessary assistance to their American colleagues. For example, we provide similar consultations within the framework of cooperation with the countries of Southeast Asia and a number of African countries,” Razbash said.

In California, about 200 thousand residents are being evacuated due to the risk of the Oroville Dam breaking. This dam is the largest in the United States. California police say they are currently opening additional shelters and places to house people throughout the state.

In the United States, almost 200 thousand residents of California are being evacuated due to the threat of a breach of the Oroville Dam. This dam is considered the largest in America, its height is more than two hundred meters. The reservoir overflowed after record rainfall for the region, and the spillway system could not withstand the load. The concrete structures were partially destroyed by the powerful flow. Residents of several large cities are hastily leaving their homes, reports.

At the Oroville Dam in California, a real disaster could occur at any moment. The volume of water that can escape from the storage facility threatens to instantly flood vast areas. Immediately after discovering a gap in the drainage system, local authorities decided to urgently evacuate residents of all settlements located below the dam. First of all, this is the city of the same name Oroville with a population of 16 thousand people, as well as a number of other settlements located along the Feather River. The evacuation began on Monday night. In total, about 190 thousand people are displaced.

"We are now opening additional shelters in several cities. In the city of Chico, St. John's Church is also open to receive evacuees. We are organizing additional places for accommodation. We are acting as prescribed in the event of a flood," said Chico Police Chief Michael O'Bryan.

To accommodate people, all available premises in schools, colleges and other areas are being used where temporary accommodation centers can be set up. The roads are filled with cars. People quickly leave the dangerous area in their personal vehicles. Taking advantage of the fact that populated areas were quickly emptying out, looters began to operate in some places. At least three stores were reported robbed.

After years of drought, northern California has seen heavy rainfall for the past few months. The water level in Lake Oroville was rising rapidly. The first reports from engineers who discovered damage to the spillway at the dam were ominous. The structure was expected to collapse at any moment. It was decided to use a reserve spillway that had never been used before. But experts found a gap in it 90 meters wide and 150 meters long. The water pressure is constantly increasing and the hole in the spillway is increasing. Erosion of the main structure already occurred in 2009 and 2013, but then engineers were able to quickly repair the damage. Authorities have now deployed helicopters to drop rocks into the open part of the drainage system to fill the gap. But the effectiveness of these actions may be low.

“At the moment, there is about one hundred thousand tons of water in the main spillway. We are now working closely with experts to make sure that we have the opportunity to eliminate the soil erosion that led to the damage to the dam. We have been able to increase the amount of water released through the reserve spillway.” , said California Civil Defense Chief Kevin Lawson.