HA NOI — Deputy Minister of Industry and Trade Hoang Quoc Vuong promised no more leaking at the biggest dam in central Viet Nam by mid-April and full repairs to be finished before the flood season starts.
"The leak at the Song Tranh 2 hydro power plant needs to be curbed by that deadline or by the end of March if possible," he said at a press meeting in the capital yesterday.
According to the Ministry of Industry and Trade (MoIT), water has been leaking from the dam in Quang Nam Province since February, worsening 10 days ago due to faulty repair carried out by the Management Board of Hydro power projects 3, an Electricity of Viet Nam unit which directly manages the plant.
Vuong said the leak had reduced after the EVN adjusted repair methods. Water had been leaking at a speed of 7 litres per second yesterday morning, instead of at 30 litres a couple of days ago.
The information was confirmed by Chairman of the Bac Tra My District People's Committee Dang Phong via telephone.
"Water flowing down to low-lying areas is currently much less, but we are still worried since the leakage remains," he said
The MoIT said water was flowing out through so-called "thermal gaps" — small openings placed between concrete blocks to prevent cracking in the heat.
To date, no cracks in the dam have been found, according to the deputy minister, who concluded that the $249-million plant "remains safe and stable".
"There's no possibility of any further accidents that could cause damage to low-lying areas," Vuong said.
The 96m-high dam, part of the hydro power plant that began operations in January 2011, is capable of holding 729 million cubic metres of water - equivalent to 43 West Lakes in Ha Noi.
While denying any mistakes in design and construction, Nguyen Tai Son, director of Electricity Construction Consultancy Company 1, admitted that "water leakage outside the dam was abnormal".
Initial assessments by experts from the MoIT, the EVN and the State Council for Assessment and Acceptance of Construction Works showed some water holes were blocked, resulting in water leaking from thermal gaps.
Water holes were designed to receive water absorbed from inside the dam's concrete walls (concrete is not an absolute waterproof material) into water ditches before it could leak out of the dam.
The MoIT said most of the blocked water holes had been clear, which reduced water leakages and the unblocking process was expected to finish by the end of March.
"More assessment and repair to prevent further water leakage must be done before the flooding season [end of July]," Vuong noted.
Meanwhile, independent expert Hoang Xuan Hong, from the Viet Nam National Committee on Large Dams and Water Resources Development, said that there must be something wrong with the waterproof shields inside the thermal gaps that normally prevent water from flowing out.
"There are technologies available in the world to fix these, but they are very costly," Hong added.
"It is important to fix these thermal gaps before they get larger under high water pressure during the rainy season or during earthquakes," he said.
Minor quakes, measuring at 3 on the Richter scale, were recorded in the surrounding area earlier this month.
The plant has passed its first State assessments which allowed it to run at part of its total capacity while awaiting full assessment in May.
"This means all repair costs must be born by the bidder, the Irrigation Construction Corporation 4," Son said. — VNS