(Xinhua)
Updated: 2008-06-08 16:03

Some 600 armed police and soldiers worked for six days and nights to dig a 475-meter channel to divert water from the lake.

Soldiers are still widening and deepening the sluice channel with the help of 30 bulldozers and excavators. They are also digging a second sluice channel on another side of the lake barrier.

The soldiers had finished building a third of the new channel, which required the removal of about 60,000 cubic meters of earth and stone, said Liu Yongjian, a PLA officer in charge of the channel.

"We have also prepared underwater blasts to deepen the channels for accelerated drainage," said Liu.

Rao Xiping, head of the Beichuan hydro-meteorological station, said the lake dam remained stable as the drainage continued.

"We have found no obvious expansion of the sluice holes nor fissures in the dam. There is no sign of dam collapse either," said Rao. The staff of his station and soldiers are keeping 24-hour patrol along the dam.

Water Resources Minister Chen Lei warned that increasing rainfall, aftershocks, landslides and leakage were still threatening the barrier.

Rainfall of 400 mm or 500 mm, well above normal levels, was forecast upstream in June and July, posing a risk for the swollen lake, he said.

Landslides could pour another 17 million cubic meters of rock and earth into the lake, threatening a dam burst and workers on the barrier could be swept away, he said.

According to the lake relief headquarters, the lake area had seen nine aftershocks measuring two to 3.2 magnitude in the 24 hours since 1 p.m. on Saturday. However, the possibility of a strong aftershock measuring six or above on the Richter scale directly endangering the dam was slim.

Geologists with the Chinese Academy of Sciences arrived at the dam on Sunday morning by helicopter to conduct a geological study of the dam.

"We planned to take dam samples with drills from eight spots on the dam for a long-term study," said Pu Zhiyong, an expert.

He said experts had set up monitoring systems, like cameras, on the two sides of the dam.

The Tangjiashan "quake lake" was formed after a massive quake-triggered landslide from Tangjiashan Mountain blocked the Tongkou River, which ran through the Beichuan County, one of the worst-hit areas in the quake.

The swollen lake is the largest of more than 30 quake lakes in Sichuan following the May 12 quake, posing a threat to 1.3 million people downstream.

More than 250,000 people in low-lying areas in Mianyang have been relocated under a plan based on the assumption that a third of the lake volume breached its banks.

Two other plans require the relocation of 1.2 million people if half the lake volume is released or 1.3 million if the barrier is fully opened.

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