Xinhua
October 1, 1999

Workers have begun to install monitoring equipment that will measure the impact of the huge explosion planned for Tuesday aimed at demolishing the last cofferdam built for the construction of the Three Gorges dam.

Yichang: Workers began to install monitoring equipment on Saturday to ensure the safe demolition of the last cofferdam built for the construction of China’s Three Gorges Dam. The equipment will measure the impact of the explosion to prevent the blast from damaging the main dam 114 meters downstreamon June 6. The cofferdam, which has been in use since 2003, is 580 meters long and 140 meters high. About 192 tons of dynamite have been placed below the waterlineto demolish the dam above the 110-meter mark, a total of 186,000 cubic meters of concrete. Scientists will measure the surge, ground swell, vibration, dynamic strain, sound waves, noise and other data, said Zhao Gen, a senior engineer with the Yangtze River Research Institute in charge of the demolition. The statistics, combined with the results of a comprehensive study of the dam and the adjacent buildings after the explosion, would be the key criteria in evaluating the blast, Zhao said. The installation of the equipment is due to be finished on June5. When the cofferdam is destroyed, a huge amount of water will bereleased to raise the water level at the Three Gorges to 139 meters from current 135 meters. The water level in the mammoth reservoir is expected to rise to156 meters after the summer flood season this year and reach the 175 meters target upon completion of the entire project in 2008. Construction of the Three Gorges Dam, on the Yangtze River in Hubei Province, was completed on May 20. The demolition of the cofferdam means the mammoth project will formally play its role in flood control, two years ahead of the schedule. The 185-meter-high dam will be able to hold back 22.15 billion cubic meters of water, and eventually produce 22.4 million kwh of electricity per hour after the power-generation facilities are installed in 2008.