An independent study says earthquakes in Quang Nam Province's Bac Tra My District, where a hydropower plant is located, could reach up to 6.1 on the Richter scale, not 5.5 as previously confirmed. Therefore, experts said the plant and its dam should be consolidated. The study, titled “Assessments on earthquakes in the Song Tranh 2 Hydropower Plant and proposals on disaster mitigation,” was conducted by a group of researchers led by Dr Cao Dinh Trieu at the Vietnam Association of Physics Geography Science and Technique, according to an order placed by the Vietnam Union of Scientific and Technique Associations (VUSTA). The study was conducted independently and was completed yesterday, October 3, Trieu said. As shown in the study, the plant is located on the Hung Nhuong-Tai Vi fault, and the earthquake activity in the area is divided into three phases: the first began in November 2011; the second started in March-April; and the most recent was in late August and early September. The intensity of earthquakes in the three stages were 3.4, 3.4-3.8 and 4.1-4.2 on the Richter scale, respectively. Before the plant was built in 2005, the Global Physics Institute had conducted a study and confirmed that the max intensity of a quake in the area was 5.5 degree, but according to this independent study, the figure is higher, Trieu said. In the center of the plant’s reservoir, an earthquake can occur at 5.9 degree, while in the dam and the plant’s downstream area, a quake can reach 6.1 on the Richter scale, Trieu said. Therefore, protecting the safety of the plant is a very important and urgent duty. Le Dinh Thang, from the Society of Soil Mechanics and Geotechnical Engineering, said the plant had been built based on the fact that the max intensity of an earthquake there would be 5.5. Therefore, given the the new conclusion of the independent study, the plant should be strengthened so that it can survive a 6.1 degree quake.
The Song Tranh 2 hydropower plant's dam, which should be consolidated soon for safety reasons, according to an independent study (Photo: VNA)
“I cannot imagine why the Song Tranh 2 Hydropower Plant was built in such an area. VUSTA should send a report about the risks to the plant to the Prime Minister,” said Prof. Nguyen Truong Tien, chairman of the Society. As previously reported, Bac Tra My has been hit by about 20 quakes since early last month, panicking local residents and authorities. After several studies, scientists have confirmed that these quakes were reservoir-induced seismic activity. On October 2, a plan to evacuate residents in Bac Tra My District in case the plant’s dam breaks was published by the Military Command of Quang Nam province and its unit in Bac Tra My. Although the State Appraisal Council has confirmed that the plant is safe for operation since the leak in the dam has been repaired successfully, the investor and the manager of the plant should not be inattentive or reckless, said Major General Nguyen Van Nhon, Deputy Commander of Military Zone 5.