VietNamNet Bridge - The Song Tranh 2 hydropower plant in Quang Nam Province, central Vietnam, is located on an active fault zone, which can cause earthquakes anytime, scientists from the Geo-physics Institute said.



Recently-reported underground explosions at the Song Tranh 2 plants were defined as reservoir induced quakes, with the highest intensity of 3.4 Richter scale.

The quakes were caused by the operation of the Song Tranh 2 reservoir, which enhanced the fault’s intensity. However, the recent quakes did not make serious impacts on the dam.

The reservoir has a capacity of 730 million cubic meters of water, making it one of the largest reservoirs in the central region.

The above information was released at a meeting between scientists of the Geophysics Institute, the Song Tranh 2 plant management board and the authority of Bac Tra My district--where the plant is situated, on April 9.

At the meeting, the related parties decided to build five seismic observation stations around the plant.

Scientists will survey five locations in the communes of Tra Bui, Tra Doc, Tra Mai, Tien Hiep and Tien Ngoc for construction of the seismic observation stations, which will be located within a radius of 10-40 km from the dam.

Once the stations become operational, they will provide necessary data for experts at the Geophysics Institute to analyze the mutual correlations between the dam’s operation and the development of the fault zone. Based on the data, the Institute will recommend optimal solutions for the plant’s operation to minimize the risk of earthquake damage.

The Institute’s Deputy Director, Dr Le Huy Minh, noted that though the earthquakes are weak in intensity and have yet to have an impact on the dam’s structure; they seem to be getting stronger.

Residents in the downstream area of the power plant have been living in fear after underground explosions and water was found leaking from the dam last month.

Leakage from the 96 metre-high dam, built as part of the hydro-power system that came into operation in January, 2011, has significantly reduced from 30 litres per second, recorded in February and early March, according to chairman of Bac Tra My District People's Committee Dang Phong.

The Ministry of Industry and Trade (MoIT) admitted that the leakage was unusual, and a number of experts questioned the quality of the dam's construction. The entire reservoir is roughly 43 times the size of Ha Noi's West Lake.

Phong said that, even though tremors have been recorded near the $249-million plant, they are not as major as the record measured of March 6, which hit 3.4 on the Richter scale.

He is hopeful that warning systems will ease worries. "We hope that the scientist's work will show there is no danger to the dam, its safety system or the surrounding areas," he said.

Minh said that the recent tremors in the vicinity could be attributed to the operations of the dam itself, adding that it was a common occurrence in areas where large man-made reservoirs have been built.

Quang Nam is said to be located on an active geological area, but much less prone to quakes than other parts of Viet Nam, especially the mountainous regions of the north-west, Nghe An, or the coastal region stretching from Ba Ria to Vung Tau.

Previously MoIT did not consider the tremors a safety risk to the dam.

"This is a normal occurrence which happens during the construction of hydro-power dams," said Deputy Minister of Industry and Trade Hoang Quoc Vuong.

Similar tremors have been recorded near the Hoa Binh hydro-power plant, constructed in the north in 1989, but they subsided within five years of construction, he said.

Na Son