Cofferdam dismantling won't trigger severe geological disaster

To blow up the massive cofferdam of the Three Gorges Project won't trigger off severe geological disasters, said an executive representing the developer.

"Blasting away the concrete cofferdam and the Three Gorges Reservoir's water storage will spark off no severe geological disasters," said Li Yong'an, general manager of China Yangtze River Three Gorges Development Corporation, in an interview with Xinhua on Tuesday.

At 4 p.m. on Tuesday, Chinese construction workers demolished the Three Gorges cofferdam connected to the southern bank of the Yangtze from the height of 110 meters above with 191.3 tons of explosives planted under the water.

The timed dismantling was declared a complete success by Li.

The explosives used to dismantle the upper part of the 580-meter-long and 140-meter-high cofferdam protecting the just-completed Three Gorges Dam were enough to topple down 400 10-storey buildings, said Zhao Gen, a senior engineer with the Yangtze River Academic Institute and also the designer of the demolition project.

The entire Three Gorges Dam, which was put to hold back water following the successful dismantling of the cofferdam's upper part on Tuesday afternoon, will play a role in this year's flood control efforts on the Yangtze River.

And the water level of the Three Gorges Reservoir rose to 139 meters after the cofferdam was partially dismantled. It will rise to 156 meters and then to 175 meters after the summer flood season is over.

"It is unavoidable to trigger earthquakes by keeping the water level in the Three Gorges Reservoir at a high level, but the aftermath won't be catastrophic," said Li.

"Three Gorges Dam will remain unaffected and safe even if there might be earthquakes," said the general manager.

Li supported his conclusion by saying that the mega dam had been constructed on a complete granite structure which has a stable trait but has no fractures or any damages.

Moreover, the intensity of the most serious quake ever taking place in the Three Gorges Area in the written history is five degrees on the Richter scale.

According to Li, China Yangtze River Three Gorges Development Corporation has entrusted the seismic institute of the China Seismological Bureau to develop an advanced reservoir-inflicted earthquake warning system.

And the monitoring records have shown that there have been an increase in the number of earthquakes in the Three Gorges Reservoir Area since June 1, 2003 when the Three Gorges Project was put to water storage to the height of 135 meters, but most of the quakes are tremors with the intensity below two degrees on the Richter scale, which won't endanger the Three Gorges Reservoir Area or ever produce impact on the Three Gorges Dam designed to sustain earthquakes measuring 7 degrees on the Richter scale.

Source: Xinhua