Dam explosion in America. The largest dam in the United States could break at any moment
Nearly 200,000 residents are being evacuated in California as the Oroville dam collapses. This dam is the largest in the US. The California police say that additional shelters and places to accommodate people are currently opening throughout the state.
Nearly 200,000 California residents are being evacuated in the United States as the Oroville dam collapsed. This dam is considered the largest in America, its height is more than two hundred meters. The reservoir overflowed after a record rainfall for the region, and the spillway system could not withstand the load. Concrete structures were partially destroyed by a powerful stream. Residents of several major cities hurriedly leave their homes, reports.
At the Oroville Dam in California, a real disaster could happen at any moment. The volume of water that can escape from the reservoir threatens to instantly flood vast areas. Immediately after the discovery of a breach in the drainage system, the local authorities decided to urgently evacuate the residents of all settlements 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 river Feter. The evacuation began on Monday night. In total, about 190 thousand people are being moved.
“Now we are opening additional shelters in several cities. In the city of Chico, the church of St. John is also open to receive evacuees. We will arrange additional places for accommodation. We act as prescribed in case of flooding,” said Chico Police Chief Michael O'Bryan.
In order to accommodate people, all free premises of schools, colleges and other areas where temporary places of stay can be organized are involved. The roads are filled with cars. People hurriedly leave the dangerous area by personal transport. Taking advantage of the fact that the settlements are quickly emptying, looters began to operate in some places. At least three stores have been reported robbed.
After a years-long drought, northern California has had heavy rainfall over the past few months. The water level in Lake Oroville increased rapidly. The first reports from engineers who discovered spillway damage at the dam were ominous. The collapse of the structure was expected at any moment. It was decided to use a reserve spillway, which had never been used before. But experts found a gap in it 90 meters wide and 150 meters long. The pressure of the water is constantly increasing and the hole in the spillway is getting bigger. Erosion of the main structure has already happened in 2009 and 2013, but then the engineers were able to quickly repair the damage. Authorities have now deployed helicopters, which are dropping rocks into the open part of the drainage system to fill in the breach. But the effectiveness of these actions may be low.
"Currently, the main spillway contains about one hundred thousand tons of water. We are now working closely with experts to make sure that we have the ability to eliminate soil erosion that led to damage to the dam. We have managed to increase the amount of water discharged through the backup spillway" , - said the head of civil defense of the state of California Kevin Lawson.
The accident with the simultaneous destruction of all the spillways of the dam in Oroville, California served as a prime example the emergence of a big problem through a small but systematic oversight. The destructive processes, not detected in time by the responsible services, eventually led to a serious threat and the need for the rapid evacuation of hundreds of thousands of people, the use of colossal forces to eliminate the accident and the expenditure of hundreds of millions of dollars on the operation. Until the situation turned into a catastrophic stage - the water did not break the dam, however, it revealed the problems of the existing system of maintenance of hydraulic structures, and destroyed the guarantees that a real tragedy would not occur in any of the regions of the world.
What is a California dam
The Oroville Dam is the highest in the United States. The height of its soil part reaches 235 meters. The dam is located on the Feather River (a tributary of the Sacramento River). A stone dam with a clay core forms the Oroville reservoir with a surface area of 10.2 thousand 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 tasks of the complex are the water supply of the region, flood control and power generation. The facility was built in 1961–1968.
The facilities of the complex are located on the right side along the river. The closest facility to the dam is the operational spillway (reinforced concrete flume) for normal water operation. To the right is an emergency discharge in case of catastrophic floods. Until the February incident, it was not used, since 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 reset looks like a hundred-meter wall with a height of 10–20 meters. The incoming water should overflow without regulation, while 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, the water level in the Oroville Reservoir has been rising at an intermittent rate. However, the record belongs to the summer of 1983, but then no emergencies were observed. In January 2017, the amount of precipitation in the region exceeded the norm by 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 revealed in the middle part of the spillway. The karst failure, as experts from the CIS believe, happened due to leaching of the rocky base. While the repairmen examined the damage, the water in the reservoir rapidly accumulated. When she reached critical point, which already threatened the safety of the dam itself, the emergency teams left the failure zone and the water was directed through the discharge.
The consequences were not long in coming. The concrete fastening on the bottom of the structure was destroyed, after which the water began to wash out the rock under the drain. The destructive process began at the time 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 any problems. The gap reached a size of 150 by 90 meters and a depth of 14 meters.
The engineers who identified the problem expected the structure to collapse at any moment, and therefore reduced the flow of water by 15%, using an emergency discharge that had not been used before, and by February 10 it turned out that the subgrade of the backup drain was also damaged, and the reason for the violation of integrity object could not be identified.
The flow of water carried the debris rock into the river bed, therefore, the operation of the hydroelectric power station had to be stopped, otherwise, due to backwater, it could be flooded. Meanwhile, the rupture pit on the main fault was expanding, destroying its walls and eroding the adjacent slope. The situation at the emergency drain has become critical. The decision was made to resume the increased flow through the main spillway, despite the threat of loss of control over the dam due to the possible destruction of the flow.
Elimination of the accident and preventive measures
Since the threat of destruction of the infrastructure of the dam, California Governor Jerry Brown has asked President Donald Trump to send federal forces and funds to eliminate emergency. In his appeal, the official noted that assistance should also be provided to the districts that house residents evacuated from areas of possible flooding.
On Monday, February 13, the Governor of California declared a state of emergency in the region, in the territory of three districts - Yuba, Sutter and Butte. State National Guard units were put on alert. The White House reported that the president had instructed the Federal Emergency Management Agency of the Department of Homeland Security to coordinate the response to the emergency. In addition, the Ministry of Defense of the country also joined the work. Pronedra wrote earlier that Trump also declared a state of emergency in the disaster area.
The Russian side immediately offered its help. The Center for the Development of the Water Management Complex of the Ministry of Natural Resources of the Russian Federation stated that domestic specialists can work on solving the problem of the emergency state 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 teams of builders 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 onto the sites of the erosion of the drain. Sandbag barriers are also being built 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 a 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 spillways will affect the further operation of the dam. Work continues. Thanks to the measures taken, the dam is already able to receive additional water inflow. At present, the discharge volume 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 level of the reservoir by 2.5 meters per day in order to safely receive the upcoming precipitation. In the riverbed, rubble is being cleared to prevent possible flooding of the HPP facilities. The launch of the station's capacities will make it possible to unload some part of the operational discharge. If the latter is recoverable, it will be repaired. In case of impossibility of repair work, a new spillway will be built. It is possible that it is necessary to reinforce the slope of the emergency discharge with concrete and, in general, assess the possibility of its use in the future.
Evacuation, panic and looting
After the information of the department water resources California about the threat of an imminent breakthrough of the dam (later it turned out that the forecasts were unreasonably exaggerated), the state authorities decided to evacuate the local population. By February 13, a total of 188,000 people were evacuated or left on their own from the cities of Yuba City, Gridley, Olivehurst, Plumas Lake, Whitland, Marysville and Live Oak. But the routes of the evacuees were observed colossal traffic jams. Temporarily resettled citizens were placed in different areas at a distance of 32-120 kilometers from the zone of possible flooding.
A significant role in causing panic was played by conflicting statements by officials, in particular, the emergence of information about the possible destruction of the dam in a matter of hours. 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 was still preserved and that 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 came from Oroville, where, in the absence of residents, there were massive thefts in abandoned stores.
Forecast of the development of the situation in the near future
The state authorities initially took a pessimistic stance in terms of predicting developments. The California Department of Water Resources admitted that if the structure of the dam is damaged, the prognosis may be unfavorable. According to local police, who interviewed experts in the field of hydraulic engineering, a hole in the weir 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, it can also cause its collapse. IN Russian Institute of hydrotechnical and energy construction believe that the dam can survive if excess water flow is discharged through open gates. A catastrophe is potentially possible if the spillway does not function.
The dimmest predictions came on February 11, when state officials announced that the water level in the river would rise to critical level due to a potential dam failure. Although the next day it was announced that the threat had passed, on February 13, there were again reports of the threat of the dam being destroyed. The negative scenario provides for the speed of wave propagation in the flat terrain within 25 kilometers per hour, in the mountains - up to 100 kilometers per hour. It is claimed 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 larger, the wave will reach a height of up to nine meters.
Recall that in the flood zone in this case there will be six settlements with a total population of up to 200 thousand people. In turn, RusHydro noted that as of February 12, when signs of active erosion of rocks were noticed on the slope below the emergency discharge, a certain threat arose for the inhabitants of the region. If the overflow wall collapsed due to intense jetting, this 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 next few days is a difficult task, say hydraulic engineers from the CIS, interviewed by journalists. It is more likely that the dam will remain intact, while the spillways - both the main and the emergency ones - will be washed out to the stage of complete destruction, but there will be no noticeable damage to the population and infrastructure. The overflow through the dam will stop after some time, or the process of spillway erosion will take place for a long period - within one month, which will not cause drastic changes in the situation and the problem will not become more complicated.
RusHydro believes that the current data give grounds to assert that there is no threat of destruction of the dam, but the spillway facilities are in disrepair. The crest of the dam is six meters above the emergency discharge mark, so an abnormal overflow of water is also excluded. If the erosion of the outflow moves to the spillways themselves, then the latter will probably be destroyed. Directly the pit at the spillway stopped active expansion, having reached the rocky base after the fragile rocks were washed away.
Meanwhile, after the accident at one dam, other "hot spots" of California were simply forgotten. The overflow of the reservoir due to heavy rainfall is a problem not only for the Oroville Dam, but also for most of the hydraulic structures in the California Valley. Fears are caused by the situation on the Sacramento River near the city of the same name. A dam on a river shows signs of deformation after prolonged exposure to water currents. Some water has already seeped through the dam and into the city park, which is located by 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 dam of the Don Pedro reservoir has almost reached the upper edge of the structure. If a snow storm breaks out in the Sierra Nevada mountains in eastern California, flooding is likely to be inevitable. To prevent these structures from collapsing, the state decided to deliberately destroy the dam on the Moklamn River, which resulted in the flooding of nearby agricultural land, but reduced the risk of large-scale accidents.
Possible versions of the causes of the accident
Possible problems with the dam became known long before the February 2006 accident. Even then, experts discovered minor violations of the integrity of the main spillway, but the facility was recognized as serviceable. Capital repair work on the dam has not been carried out for half a century - from the day it was put into operation. For the past decade, the dam has operated under a temporary license. Probably, the reason for the uncertain status of the dam is associated with an attempt to issue a permit for a period of 50 years by the California authorities and the subsequent reaction of the public.
In 2005, a group of environmental activists - the South Yuba Citizens League, Sierra Club and Friends of the River - demanded that the authorities reinforce the emergency release with concrete instead of earthen bedding. In a joint letter from the organizations, it was stated that during the winter rains, water would begin to overflow through the main spillway, which would eventually lead to erosion with further structural failure and flooding. The proposals were received by the presidential administration and the Federal Energy Regulatory Commission, but they, based on the conclusions of the California Department of Water Resources about the inappropriateness of such work, 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 cost millions of dollars. Now, the department claims that the cause of erosion on the drains is unknown.
Like any serious threat, the situation with the risk of a dam failure is already overgrown with rumors and exotic theories. In particular, it is assumed that a possible catastrophe was deliberately provoked in order to smooth out the discontent of the California population, the majority of which voted for Hillary Clinton in the presidential election. A big disaster can unite a nation and eliminate political divisions. In addition, it should be borne in mind that California public activists are actively calling for the separation of the region from the United States.
Supporters of the conspiracy theory believe that the failure of the main spillway was manageable and was the result of sabotage - the leak arose by interfering with the work of an already worn-out infrastructure. In addition, there were statements that the rescue services conducted exercises a few years ago, during which they practiced actions in the event of a dam failure. At the same time, the almost exact date of a possible event has already been specified in the scenario of maneuvers.
If we talk about real facts, then RusHydro, which analyzed the development of the emergency situation and possible prerequisites, came to a number of conclusions. It is noted that the destruction of the operational spillway occurred suddenly, and the levels of water flow were not at all maximum. Thus, we should talk about the insufficient degree of control over the state of the hydraulic structure, which did not allow timely detection of damage, the company noted.
It is difficult to call correct the design decision itself, associated with the discharge of water masses onto an ordinary unequipped slope. Spillways must pass mandatory tests. Nevertheless, it must be stated that the safety margin of the dam turned out to be sufficient, despite the fact that accidents occurred on both spillways. Thus, large hydraulic structures in general can be considered reliable structures, the company noted.
Regardless of what the conclusions of the investigation of the accident turn out to be, it is obvious even to non-specialists that, apart from dubious theories of sabotage or sabotage, the unsatisfactory condition of both spillways, most likely, was the result of the usual negligence of services that did not track the process of structural damage due to natural wear processes. The lack of preventive measures almost caused a large-scale tragedy, and only the reliability of the dam itself, which acted as insurance against the negligence of industry services, can be thanked for the happy outcome of the situation.
For the second day in the world, tension is following the situation in California, where it can happen at any moment. Forces drawn to the region National Guard. The engineers managed to partially close up the holes in the spillways, however, the main threat lies ahead. In the near future, heavy rains will return to the area of the dam, which is already barely holding back the onslaught of water.
Hundreds of thousands of tons of water rushed down through the concrete wall of the emergency spillway. The stream washed away the road, the slope changed beyond recognition - there are now like channels of mountain rivers - narrow and seething.
Helicopters take off carrying bags of boulders. They drop stones to strengthen those places where it has already been washed away. In the same way, they try to somehow correct the flows and fence off vital objects.
Residents were notified of an urgent and mandatory evacuation through all channels, including automatically via smartphones. A message is forcibly displayed on the phone screen. A sharp signal sounds that cannot be ignored.
They were given 30 minutes to evacuate. During this time, the inhabitants of the town of Oroville in California had to collect documents, take pets, the most necessary things, jump into the car and rush to the top of their lungs. Away from the unpredictable Oroville Dam, 235 meters high.
“All this is very stressful, we are shocked. A lot of people, children - no one knows what to do now. Everyone is exhausted and upset that all plans have been violated,” says California resident Joelen Hull.
After record rainfall in California, the level in Lake Oroville went up sharply. The dam holds back the pressure of 4.5 billion cubic meters of water.
Specialists of the hydroelectric power station, which is located underground, opened a spillway next to the dam, but a large gully formed in the concrete gutter, which increased every hour. Then they decided to close it and use an emergency spillway - this is a high concrete wall through which water, flowing, is discharged onto an unfortified slope.
No one followed him, in many places he was overgrown with trees. It was no longer possible to calculate the consequences of the work of the dam and the hydroelectric power station in such emergency conditions, so it was decided to evacuate 200 thousand people from nearby settlements. The dam itself, authorities assure, is in order.
"Let me reiterate - the dam itself is strong. And it works reliably now during the record filling of the reservoir. Although we are faced with wear and tear on small fragments of the structure that are critical to the operation of the dam," said Bill Croyle, head of the California Department of Water Resources. .
What happens in the worst case scenario? There are only preliminary calculations. In a matter of hours, the town of Gridley can go under water, then Live Oak, and they are 50 kilometers from the dam.
It turned out that the accident at the dam was unexpected only for American officials. Back in 2005, three panels of experts warned that in the event of heavy rainfall, the spillways of the Oroville Dam might not work. But neither local nor federal authorities paid any attention to it.
“They should have been wary that something was going wrong. They should have started thinking in advance about what needs to be done. And not dragging it out until the last minute and then raising such a panic with everyone around,” he is outraged local Robert Brabant.
Modernizing a dam built in the 60s of the last century would cost hundreds of millions of dollars, and no one wanted to pay for it.
People are most interested in whether the dam is safe and when they can return to their homes. Now the level in the reservoir has been stabilized. At least until new rainfall.
In northern California, a state of emergency has been introduced and an order has been issued to evacuate 190 thousand people due to the threat of a dam break near the city of Oroville, one of the largest dams in the United States. Now the water level in the Oroville reservoir has risen to a critical level due to heavy rains, and the dam's drains are damaged, which at any moment can lead to flooding of the adjacent territory.
In California, the evacuation of residents of the city of Oroville and neighboring areas has been announced due to the threat of a breakthrough of one of the largest dams in the United States. A total of 190,000 people have been ordered to evacuate. California Governor Jerry Brown state of emergency in this territory. According to the California Fire Department, 35,000 people were evacuated in Butte County, which contains Oroville, 65,000 people in Yuba County, as well as 76,000 residents of Yuba City and 12,000 residents of Marysville.
The dam itself was not damaged, but an emergency spillway designed to be quickly emptied in the event of a sudden rise in water levels was destroyed on Sunday. According to the authorities, the spillway could not withstand the load and collapse at any moment, which will lead to the release of water from the Oroville reservoir. The main spillway was also washed out earlier last week.
If the dam breaks, the water could flood nearby towns. The water level in the Oroville Reservoir has risen due to heavy rain showers. Rainfall in Northern California is 228% above average for this time of year. “A dam failure like this is a disaster. We have determined that we cannot repair the damage,” California Water Resources Administration chief Bill Croyle said during a press conference.
The Oroville Dam on the Feather River is the tallest in the United States, reaching 230 meters in height. The dam was built in the 1960s. The Oroville Reservoir is the largest in California.
Doctor of Technical Sciences, Head of the Surface Water Modeling Laboratory of the Institute of Water Problems of the Russian Academy of Sciences Mikhail Bolgov: “You need to know the design of this dam and what place the emergency spillway occupies in it in order to give a full-fledged forecast. But according to preliminary data, the consequences of its breakthrough can be catastrophic, there is a very large reservoir with high pressure, so the destruction can be colossal. Usually the spillway is arranged so that it starts working as soon as the reservoir is close to overflow. Operational services try never to bring the situation to this point, this is a last resort. Why all the negative conditions have accumulated there, why, roughly speaking, this hole began to work in emergency mode, it is not clear. During construction, conduits are specially left, which are then plugged with concrete. Maybe this is one of the remaining construction conduits, but, as I said, they are plugged with concrete. The evacuation of people always occurs when the risks become great. This does not mean that the dam will definitely not withstand, but it is necessary to carry out an evacuation. It is necessary to carry out a full set of emergency measures, because it is better to resettle people than to catch the corpses later. There is only one way to reduce the level - all spillways are opened, all turbines, if they are in the dam, are turned on at full capacity, for this, thermal stations are shut down and in such a design mode hydraulic structure begins to work in order to minimize the pressure on this place where the accident occurred.
Former director for technical policy of JSC RusHydro Rasim Khaziakhmetov:“Information about the state of the Oroville dam is contradictory, I would say too much media and does not allow you to accurately predict the consequences. If the media and local authorities exaggerate the risks, nothing serious will happen. If the photos and videos of the first half of the day are accurate, then watersheds can be destroyed and, again, the consequences will not be excessively catastrophic, especially since the authorities have taken serious measures to evacuate the population. It was a little annoying that on one of the shootings from a helicopter, signs of filtration of the dam itself were visible, but this is scary. Imagine that there will be a landslide and a wave with a height of more than 200 meters with a pressure of 20 atmospheres will rush down. Then it may turn out that it was necessary to evacuate not 180 thousand people, but much more. There was already an accident in history, when in 1963 a landslide occurred in Italy and poured water over the dam. Despite the fact that there was practically a flat desert around and the wave height was about 20 meters, several villages were washed away in 7 minutes, 3 thousand people died. Everything seems much more dangerous here.”
Former Deputy Minister of Energy and former Chairman of the Board of Directors of RAO UES of Russia Viktor Kudryavy: “There is very little accurate information about the real situation with the dam, to what height it can collapse, at what speed, the characteristics of the lake itself, the amount of water accumulated in it, what elevation difference downstream, the terrain, whether there are turns that can provide overflow and mitigate the effects. A lot of factors. But it is clear that the base of the dam is good, since they are not very afraid, and a breakthrough can only occur in the upper part. The dynamics of destruction, height and wave speed are terrible. Total destruction will lead to a catastrophe the world has never seen before. I really hope it doesn't happen."
Yana Rozhdestvenskaya; group "Direct speech"