The volume of water leaking from the Song Tranh 2 hydropower plant’s dam in Quang Nam Province is 75 litres per second, not 30 litres as earlier reported and fivefold the acceptable level, the Management Board of the Hydropower Project 3 confirmed.
Tran Van Hai, head of the board, gave the confirmation at Tuesday’s meeting with a group of experts from the Global Physics Institute and the Institute of Mechanics who were conducting a survey on the dam’s safety.
| The dam of the Song Tranh 2 hydropower plant in Quang Nam Province |
Photo: Tuoi Tre
The volume of the leak is five times higher than the acceptable level of 15 litres per second, according to standards of the Department of Verification of Work Construction.
However, Hai told the meeting that such a leak level is not a problem. “The leak at 75 litres per second is still safe. In the US, some dams have leaked up to 500 litres per second and survived.”
Since the leak was discovered last month, the Electricity Group of Vietnam (EVN) has directed the plant to operate at full capacity to reduce the water level in the plant’s reservoir to facilitate solutions to the leak. As a result, the water level has been reduced to 155 metres, 15 metres above the dead line, Hai reported.
EVN has asked the plant to maintain such a level to ensure the plant’s optimal operational efficiency, Hai said.
Dr Nguyen Tien Khiem, from the Mechanics Institute, said the agency would give recommendations on how the dam should be repaired and controlled after obtaining data from five seismic observation stations that have been planned to be built in locations around the dam.
Such stations are needed as scientists have confirmed that the plant is located on the Hung Nhuong-Ta Vi-Tra Bong fault zone, which can trigger earthquakes that could damage the dam’s structure.
For the time being, the dam’s managers should record exactly the volume of water leaking out from expansion joints and any changes in the leak’s volume over time to form a basis for taking proper remedies.
He also said any changes in the expansion joints after any earthquakes in the area must also be recorded in order to determine what impact such an event can have on the dam.
Dr Le Huy Minh, deputy head of the Global Physics Institute, asked the plant’s management to inspect the expansion joints using ground-penetrating radar (GPR/georadar), which is a geophysical method that uses radar pulses to image the subsurface.
GPR surveys can detect subsurface features without drilling, probing, or digging. This nondestructive method uses electromagnetic radiation in the microwave band of the radio spectrum and detects the reflected signals from subsurface structures.
The plant’s managers should report to EVN regarding this issue so that the group can prepare expenditure for such an inspection, which needs to be conducted soon, Minh said.