THREE GORGES DAM SITE, Hubei Province, June 5 (Xinhua) -- The demolition of the last cofferdam protecting the just-completed Three Gorges Dam set for June 6 will take only about 12 seconds with explosive enough to topple down 400 10-storey buildings, said a senior project designer here on Monday.

    Zhao Gen, a senior engineer with the Yangtze River Academic Institute, designer of the demolition project, said that 191.3 tons of explosives have been installed to demolish the concrete cofferdam. Debris from the explosion will be measured at 180,000 cubic meters.

    The removal of the cofferdam means the Three Gorges Dam, completed on May 20 this year, will formally begin its role in flood control two years ahead of the schedule.

    The cofferdam holding the reservoir water since 2003, while construction of the dam was going on, is 580 meters long, 140 meters high and eight meters wide at the top.

    Zhao said that the blast will only remove the upper 30 meters of the cofferdam, which is now holding the reservoir water up to 135 meters above sea level. While, the under-water part of 110 meters in height will be remained in water as a protective structure for the dam. Enditem