Song Tranh 2 incident and safety at hydro-power plants

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Song Tranh 2 incident and safety at hydro-power plants

VietNamNet Bridge – From the leakage at the Song Tranh 2 hydro power plant which is stirring up the public in the last couple of days, let’s review the panorama of hydro-power development in Vietnam.



Ministry says Tranh River hydropower plant is faulty



Leakage at the Song Tranh 2 dam.

Planning, design and construction of hydro-power plants

In Vietnam, hydro-power accounts for up to 40 percent of the total power output. However, the water resource for power generation is dependant on the weather and the operation of reservoirs.

Vietnam does not have a law on planning, so all sectors have their development plans but these plans are not closely connected with each others. As a result, there are overlap and conflicts in development plans.

The biggest problem of the hydro-power development plan is it intensifies water-use conflict. In 2010, we had a field trip to Yok Don forest in Dak Lak province and witnessed a 20km dried section of the Serepok River, which was caused by the Serepok 4A hydro-power plant’s dam. Obviously, if hydro-power benefits power producers, it will affect others by causing flood or drought.

In the market economy, investors in hydro-power seek to earn highest profit. They try to save on cost in all tasks, from survey to design, construction and assessment, etc. This type of thrifty practice will affect the quality of hydro-power plants.

In Vietnam, roller-compacted concrete (RCC) dams are designed under American standards, rock-faced earth-fill dams are designed under Chinese standards and earth-fill dams are designed under Vietnamese standards (based on Russian standards).

This fact has resulted in a matter: Vietnam’s current standards are inconsistent in classifying hydro-power plants based on capacity.

In developing hydro-power in Vietnam, the factor called “environmental flow” and what will happen when hydro-power plants stop operation (when deposits cover the water-receiving door) are not considered carefully.

Song Tranh 2 incident

Leakage in the left side of the dam of Song Tranh 2 hydro power plant has been detected recently. Water flows from the reservoir through the leaks and cracks that have developed on the dam.

When the incident broke out, the project management board confirmed that water leakage Song Tranh 2 hydropower dam does not pose safety problems although Quang Nam Province’s residents and authorities heightened their concerns over the leaks.

“Water flows downstream via leaks at 30 liters per second, which remains a safe level for the dam,” said Tran Van Hai, head of the Hydro Power Project Management Unit 3.

Plus, relevant agencies also reported the dam still meets technical requirements.

Moreover, Hai claimed that water running from reservoir is actually through heat vents instead of leaks. Some 30 heat vents along the reservoir aims to eliminate thermal stresses causing concrete cracks during the dam’s operation.

As the biggest reservoir in the central region, Song Tranh 2 plant’s reservoir can store 730 million of cubic meters. But it is built 100 meters higher than the basin areas, so the leaks raise concerns over the safety of nearby residents. Song Tranh 2 hydro power plant has a total investment capital of VND5.2 trillion and a designed capacity of 190 MW. The plant was built in 2006 and it officially generated electricity in 2010.

Hydraulic Construction Corporation No.4 and the management board are working closely on the conditions against water leaks in an effort to enhance the quality of the dam. Hai echoed the technical issue does not affect the dam’s operation and stability.

However, Cao Dinh Trieu, a specialist working at the Institute of geology, said Song Tranh 2 hydro-electric plant is located on a strong operating fault zone, and it is urgent to fix the current leakage through the dam to avoid flooding disaster for downstream areas.

“If the leakage expands further, the dam will collapse, pouring millions of cubic meters of water from the 100-meter reservoir to the downstream areas alongside unexpected damages,” Trieu said.

According to the latest conclusion made by Deputy Prime Minister Hoang Trung Hai on March 28, relevant authorities had inspected the dam and they had not found any unusual cracks that would be a matter of concern.

However, Mr. Hai still instructed all the relevant parties to speed up repair work of the cracks on the dam that were still leaking water.

He blamed the Electricity of Vietnam Group (EVN), the investor in the hydropower plant, for confusing the public on actual facts of the situation, handling the issue unprofessionally, and not informing the media in time and with factual information.

He instructed EVN to run the Song Tranh 2 Hydropower Plant at its fullest capacity to lower the water level in the reservoir and facilitate repair works.

Leaks in the dam are currently being repaired and there is no danger to the plant. EVN should instruct relevant units including investors, contractors and consultants of the plant to urgently step up measures to plug the leaks and also look into the causes.

They must regularly report to the State Inspection Committee for Construction Projects and the Ministry of Industry and Trade.

The ministry should coordinate with the group and the council to send experts to the scene to monitor and instruct the implementation of repair works, and host a press conference to explain clearly all investigation results and solutions.

Mr. Hai tasked the State Inspection Committee for Construction Projects to give their conclusions on the dam safety and inform residents so that they can feel much more secure.

The People’s Committee of Quang Nam Province should continue to work with EVN and the Ministry of Industry and Trade to operate the hydropower plant safely and effectively.

The Ministry of Information and Communications should instruct the media to report factually and objectively about the situation at the Song Tranh 2 Hydropower Plant, so as not to raise panic in people.

Though the dam is still safe, the incident is a serious warning for the safety of hydro power plants in Vietnam.

A dam in the US was broke with an initial phenomenon like Vietnam’s Song Tranh 2. The St. Francis Dam was a concrete gravity-arch dam, designed to create a reservoir as a storage point of the Los Angeles Aqueduct.

The dam was built between 1924 and 1926. Two and one-half minutes before midnight on March 12, 1928, the dam failed catastrophically, and the resulting flood killed more than 450 people. The collapse of the St. Francis Dam is one of the worst American civil engineering failures of the 20th century.

Throughout 1926 and 1927, several temperature and contraction cracks appeared in the dam as the reservoir filled. The cracks and leaks were inspected and judged to be within expectation for a concrete dam the size of the St. Francis.

A new leak was discovered on the morning of March 12. Concerned that the muddy color of the runoff, experts observed could indicate the water was eroding the foundation of the dam. After inspecting the leak, they determined that the muddy appearance of the water was not from the leak itself, but came from where the water contacted loose soil from a newly cut access road. Convinced that the leak was not a danger, they pronounced the dam safe.

Two and one-half minutes before midnight on March 12, 1928, the St. Francis Dam catastrophically failed.
As the dam collapsed, 45 million m³ of water surged down the San Francisquito Canyon in a dam break wave and destroyed everything in its path.

The Los Angeles Coroner's Inquest concluded the disaster was primarily caused by the paleomega landslide, on which the eastern abutment of the dam was built, but would have been impossible for the geologists of the 1920s to detect. The jury determined responsibility for the disaster lay with the governmental organizations which oversaw the dam's construction and the dam's designer and engineer.

TVN

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