Looming Nor Cal Natural Disaster

In northern California, on the western side of the sea of Nevada flows the sparkling water of the feather river. A river once priced for its gold, once feared for its massive floods and destruction of human life, animal, and farm produce- today the flood waters of feather river has been tamed and stored at the Sierra Nevada foothills as the primary water storage facility for the California water state project.

An outstanding engineering achievement has achieved this project by building the Oroville Dam; at 770 feet (230metres) high, making it the tallest dam in the US. The Oroville Dam is an earth-fill embankment dam on the Feather River east of the city of Oroville, California, in the United States constructed of concrete and asphalt.  Its principal purpose being water supply, hydroelectricity generation, and flood control. The dam impounds Lake Oroville, which is the second largest human-made lake in the state of California.

The barrier can store more than 3.5 million acre-feet (4.4km3) and is in the east of the Sacramento Valley. It was built by the California Department of Water Resources (DWR), Oroville Dam is one of the major achievements of the California State Water Project, one among the two major projects passed that set up California’s statewide water system.

The construction of this dam was initiated in 1961 and was encountered by numerous difficulties during its construction, including multiple floods and a major train wreck on the rail line used to transport materials to the dam site. Despite all the drawbacks during this stage of construction, the embankment was topped out in 1967 and the entire project was ready for use in 1968. The dam began to generate electricity after the Edward Hyatt Pump-Generating plant was completed then later the US largest underground power station.

History of Oroville Dam construction:

In the year 1935, work began on the Central Valley project (CVP), it was a federal water project that would develop the Sacramento and San Joaquin river systems for irrigation of the highly fertile Central Valley. However, after the end of world war II in 1945, the state experienced an economic growth that led to rapid urban and commercial growth in the central and southern portions of the state, this clearly shown that California’s economy could not depend solely on a state water system geared primarily towards agriculture. A new study of California’s water supplies by the Division of Water Resources (today California Department of water Resources, DWR) was carried out under an act of the California State Legislature in 1945.

Later in the year 1951, California State Engineer A.D. Edmonston proposed the Feather River Project which was the direct predecessor to the State Water Project (SWP), which included a major dam on the Feather River at Oroville, and aqueducts and pumping plants to transfer stored water to destinations in central and southern California. This proposed project by A.D. Edmonston was strongly opposed by voters in Northern California and parts of Southern California that received water supply from the Colorado river, although it was supported by other Southern Californians and San Joaquin Valley farmers. However, major flooding in the year 1950 facilitated the 1957 passage of an emergency flood-control bill that provided sufficient monetary funds for construction for a dam at Oroville, regardless of whether it would become part of the State Water project.

In May 1957 groundbreaking on the dam site occurred with the relocation of the western Pacific Railroad tracks that ran through the Feather River canyon. The Burns-Porter Act, which authorized the State Water Project, was not passed till November 8, 1960. Engineer Donald Thayer of the Department of water Resources was commissioned to design and head construction of the Oroville Dam, and the original contract work was assigned to Oro Dam Constructors Inc, a joint venture led by Oman Construction Co.

Two concrete-lined diversion tunnels, each of length 4,400 feet (1,300m) long and 35 feet (11m) in diameter, were excavated to channel the Feather River around the dam site. One of the tunnels was located at river level and would carry average water flows, while the second tunnel would only be used during excessive rain that would lead to floods. In May 1963, workers poured the last of 252,000 cubic yards (193,000m3) of concrete that comprised the 128-foot (39m) high cofferdam, that would protect the construction area from floods. This structure would then later serve as an impervious core for the completed dam. With the cofferdam in place, an 11-mile (18km) railway line was constructed to move earth and rock to the dam site. An average of 120 train carriages ran along the line each hour, transporting fill that was mainly excavated from large piles of hydraulic mining remains that were eroded down by the Feather River after the California Gold rush.

On December 22, 1964, disaster nearly struck when the Feather River, after days of heavy rainfall, reached a peak flow of 250,000 cubic feet per second (7,100m3/s) above the Oroville Dam site. This Christmas flood of 1964 was one of the most disastrous floods in the records of northern California region, but the incomplete dam managed to reduce the peak flow the Feather River by nearly 40 percent, averting massive amounts of damage to the area.

After ten months, four men, died in a tragic accident on the construction railway line. On the month of October 7, 1965, two 40-carriage work trains, one was fully loaded and the other empty, had a head-on coalition at a tunnel entrance, igniting 10,000 US gallons (38,000l) of diesel fuel, destroying the two locomotives. The burning fuel from the collision started a forest fire that burned 100 acres (40ha) before it could be extinguished. The crash delayed construction of the Dam by a week while the train wreckage was being cleared off the site. The Oroville Dam was designed to be earthquake proof able to withstand the strongest earthquake possible for the region and was fitted with hundreds of instruments that serve to measure water pressure and settlement of the earth fill used in its construction; this earned it the nickname “the dam that talks back”.

Damage progression of Oroville Dam

On February 7, 2017, during the ongoing flood control release of about 50,000 cubic feet per second (1,400m3/s), a crater appeared in the Oroville Dam spillway. High inflows to Lake Oroville forced dam operators to continue using the damaged spillway, causing additional damage to the existing damage on the spill way. By February 10, the spillway hole had grown to 300 feet (90m) wide, 500 feet (150m) long and 45 feet (14m) deep. Meanwhile, remains from the depression in the central spillway was moved away downstream, and caused damage to the Feather River Fish Hatchery due to high turbidity, State workers began removing fish and eggs from the hatchery to reduce the damage. Although engineers had hoped that using the damaged spillway could drain the lake enough to avoid use of the substitute spillway, they were forced to reduce its discharge from 65,000 cfs (1,800 m3/s) to 55,000|cu|ft/s (1,600|m3/s) due to potential damage to power lines.

Measures were taken to prepare the emergency spillway that is officially known as the substitute spillway, for first-time use. On February 10, 2017, power transmission lines were moved, and workers began clear-cutting trees on the hillside below the substitute spillway.

Shortly after 8:00 am on February 11, 2017, the substitute spillway started carrying water for the first time since the construction of the dam in 1968. This is because the spillway was a separate structure from the dam officials stated that there was no danger of the main embankment being breached, and evacuation of Oroville region itself was not put to consideration at that time, as officials stated that there was no threat to public safety. Once the lake rose to the level of the substitute spillway, an overflow that topped out at 12,600|cu|ft/s (360|m3/s) began that was uncontrollable, and water directly flowed onto the hillside below the concrete crest of the substitute spillway.

On February 12, 2017, an evacuation was ordered for those in low-lying places along the River Feather Basin in Butte, Yuba and Sutter counties, due to an anticipated failure of the substitute spillway. Specifically, erosion on the side of the hills was growing uphill toward the concrete edges of the replacement spillway, leading to the fear that it would collapse. A failure of the solid top of the spillway would allow up to thirty vertical feet of Lake Oroville through the gap in an uncontrolled flood. The flow over the main spillway was increased to 100,000 cu ft/s (2,800 m3/s) to try to slow the erosion of the substitute spillway.

By 8 pm. on the evening of February 12, the increased flow had successfully lowered the water level to below the substitute spillway, allowing the replacement spillway to stop overflowing. However, evacuation orders were not revoked, the soil erosion there to be hastily inspected and stabilized with boulders. Experts are worried that the damage would be moved to the main spillway, not only to make future repairs more expensive but also that the damage to the main spillway could grow uphill to the point that it endangered the main spillway gates, this has left no safe way to release water. The prediction of such damage was in-evident, hidden by water spray and darkness; it was expected to be assessed on the morning of the 13th.

During late night of February 12, helicopters were dropping boulders into damaged areas to shore up the erosion.

Problems caused by damage from Oroville Dam

  1. Displacement of people living around the area.
  2. This will cause stop in learning activities for scholars around the area.
  3. Increased financial expenses in maintenance of the damaged parts of the dam, increased demand of emergency health services, reconstruction of recreational facilities and shelter provision for the displaced people in the region.

Future of the Oroville Dam

The future of the Oroville Dam lay in the hands of the California Water state department and they are expected to roll out a method of saving this dam before there is too much collateral damage, hence maintain Oroville region irrigation projects, fishing, and even farming in order to maintain Californians economical activities majorly relying on the Dams life.

Failure of intense action towards saving the life of this life time engineering project, Oroville region will resume heavy flood problems from river feather, hence leading to endangerment of farming and fishing activities in the region.

Recent updates concerning Oroville Dam

Lake Oroville water levels have fallen to 901 feet, the level at which water flows over the emergency spill way, state figures from 8 p.m. show. That means little or no water is likely coming over the emergency spillway and the threat of collapse due to erosion has diminished said Joe Countryman, who is a member of the Central Valley Flood Protection Board and he was also a former engineer with the U.S. Army Corps of Engineers.

Water coming over the top of the emergency spillway is likely to be the main factor in its erosion, Department of Water Resources spokesman Chris Orrock said Sunday night.

Now, officials should be able to start assessing the damage caused to the emergency spillway as it begins to dry up. “They are going to dry out the emergency spillway area,” Countryman said. “They are going to start the repair work.

This does not mean that the risk of catastrophic flooding has come to an end. Officials released water so quickly in a rush over the damaged main spillway that they may have further threatened its integrity and hence its vulnerability, Countryman said.

 

Leave a Reply

Your email address will not be published. Required fields are marked *