Leaking dam needs overall check, experts say

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VietnamNet English - 32 month(s) ago 4 readings

Leaking dam needs overall check, experts say

Amidst increasing concerns about the leaking dam of the Song Tranh 2 hydropower plant in Bac Tra My and Nam Tra My Districts, Quang Nam Province, some experts have called for a comprehensive check of the facility in order to avoid any possible consequences.






Dr To Van Truong, one of the experts of the Ministry of Science and Technology’s scientific research program involving natural resource exploitation, disaster prevention and environmental protection, told Tuoi Tre that independent consultants should be engaged in a comprehensive inspection of the dam to identify the cause of the problem and seek remedies.

His proposal was made after the Vietnam National Verification Department for Construction Works confirmed after an inspection that the dam was experiencing water leakage but “remained in safe conditions.”

As reported earlier, there are seven locations in the dam’s body from which water is leaking in strong currents at a volume of 30 liters per second, double the acceptable level.

The fact that water impregnated into the damp’s body and then leaked out proves that there is something wrong in the dam’s design, Truong said. “Under standard design water can penetrate into the dam’s body, but it is not allowed to reach to the surface of the dam and flow out.”

There should have been a water collection system arranged at the dam’s contraction and expansion joints to receive the impregnated water so that it could not leak, he said, adding that the dam’s contractor and supervisor should have discovered this omission and taken measures to correct it.

Risk management

Risk management measures, which are usually taken for large dams in many other countries in America, Europe and Asia, must be carried out to minimize the risk of damage, Truong said.

In 1926 and 1927, the St. Francis Dam in Los Angeles, the US, experienced the same problems as the Song Tranh 2 dam, with many cracks appearing on the dam’s body, causing water leakages. On March 12, 1928, a new leak was discovered and there were worries that the dam had been undermined.

After an examination, American experts announced that the dam was still in safe condition. However, in the middle of that night, the dam collapsed, killing a total of 600 people, Truong said.

“Subsequent inspections blamed the disaster on three main causes: the geological instability of the foundation on which the dam was set, mistakes in design – especially the increase of the dam’s height in 1925, and shortcomings in supervision and construction,” he said.

“After the disaster, Los Angeles authorities ordered a re-examination of the Mulholland Dam, which had the same characteristics as the St. Francis structure, in order to prevent similar incidents.”

Similarly, the Song Tranh dam should be re-checked in terms of design, construction, and supervision to find the cause of the leaks. There should not be any perfunctory conclusion about the dam’s problems only to calm the public’s nerve, he said.

Expert council needed

Considering the leak of the dam as abnormal Prof. Dr. Nguyen The Hung, deputy chairman of the Vietnam Society of Fluid Mechanics, said the State should set up a council of senior specialists in various fields, including geography, structures and hydraulics to identify the causes and seek feasible and effective solutions to the problem.

The check should be carried out immediately so that it can be completed before the rainy season begins, he suggested. “If we don’t take action soon, the useful life expectancy of the dam will be reduced, causing a huge waste to the State’s budget, since the dam is a national property.”

He also said the conclusion that “the damp remains safe” was a hurried decision, since such water leaks are abnormal and further inspections must be carried out to identify what exactly the problems are.

In case the damp is destroyed the consequences, especially in human life, will be very great and unforeseeable, Hung warned.

According to its design, the 190 MW hydropower plant’s reservoir can contain 730 million cubic meters of water, making it one of the top reservoirs in the central provinces.

Tuoitre

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