On May 1, the upper coffer-dam, or the watertight enclosure used to hold back water to construct the dam, was broken, putting this section of the dam into full operation.

Since early this month, the continuing rainfall in the upper reaches of the Yangtze River and the Three Gorges Project (TGP) construction areas has tortured the project, the biggest dam ever built in the world.

Meanwhile, sound quality tests of the dam smashed recent rumours that poor construction quality and management loopholes have resulted in cracks, said sources with TGP builders.

By May 9 the water level was dangerously high as it grew to reach 68-metres, officials said.

But the 22 floodgates, each 10-metres-high and 6-metres-wide, did their job, and no damage to the dam was found.

Coffer-dam plays vital role in construction of TGP dam

During the past days, the quality of the concrete dam such as the welding and installation of floodgates were in excellent condition after severe water tests.

To ensure the non-interruption of river shipping, the 2,309-metre-long TGP construction falls into two phases: the current 1,600-metre dam and another 600-metre section to be built in December.

Since the river was dammed on December 8, 1997, the coffer-dam has endured numerous flood peaks and has played a vital role in the construction of the TGP dam, sources said.

Over the past four years, TGP builders have built many record-high portions of the dam, including a 168-metre-tall strong-intensity dam with some portions topping 185 metres in height.

After conducting careful checks and inspections, experts agreed in April to break the coffer-dam for good.

Dam builders are busy dismantling the rest of the 900,000 cubic metres of dam from 3.3 million cubic metres in total, sources said. It is predicted that removal will last until the end of June.

According to the TGP construction schedule, another coffer-dam in the lower reaches will be torn down on July 1.

Boasting the world's largest hydropower project, the multi-billion-yuan project began in 1993 and will be completed in 2009.

( May 14, 2002)