By Tyra Dempster
DUJIANGYAN, China (Reuters) - Five thousand tonnes ofdangerous chemicals and heavy rain are adding to the mix ofthreats from one of China's "quake lakes" in danger of burstingtheir banks, a newspaper said on Thursday.
Illustrating the sense of urgency, the Finance Ministrysaid it was funnelling an extra 1 billion yuan (73 millionpounds) into relief work on an estimated 35 quake lakes inaddition to 400 million yuan already allotted to work onsmaller, damaged dams.
About 5,000 tonnes of chemicals, including sulphuric andhydrochloric acid, were trapped downstream from the Tangjiashanlake and had to be moved to safe ground, the Beijing News said,citing local environmental authorities.
China has evacuated more than 150,000 people living belowthe swollen Tangjiashan lake, formed by the devastating May 12earthquake, amid fears it could burst and trigger massiveflooding.
The official death toll from the 7.9 magnitude quake isalready more than 68,000 and is certain to rise further, withnearly 20,000 listed as missing. Aftershocks on Tuesday toppled420,000 houses, many already uninhabitable.
The chemicals, adding pollution to the threat of flooding,were stranded in different work sites downstream from the lake,the newspaper said.
The Tangjiashan lake was created when landslides blockedthe Jianjiang river above the town and county of Beichuan inmountainous Sichuan province, near the quake epicentre.
It has been raining at the site from early Thursday,hampering efforts by more than 600 soldiers to open a giantsluice to discharge floodwaters, Xinhua news agency said.Helicopters shipping in equipment were unable to take off.
Some 1,000 People's Liberation Army soldiers were makingtheir way by foot to the lake, carrying more than 10 tonnes ofdiesel for bulldozers already there.
SUDDEN BREAK
Alexander Densmore, a seismologist at Durham University inBritain, said any break in a quake lake would likely be sudden.
"It's a very real problem," said Densmore by telephone."These landslide dams pose a really significant risk in thesemountain regions, and in these narrow valleys it doesn't takemuch material to create a complete blockage."
Once a breach occurred, there could be an acceleratingprocess leading to a sudden rush of water downstream.
"Once that process starts, it's virtually impossible to doanything to decrease the water... When they fail, they tend tofail catastrophically," he said of the quake dams.
Given the topography of Sichuan, with the western mountaincountry giving way to plains around Mianyang, a major rush ofwater could spill downstream and possibly affect lower-lyingareas of cities such as Mianyang, he said.
The region along the faultline is densely packed with dams,raising concerns that if either the quake lakes or the weakeneddams burst, the rush of water could cause others to fail.
A massive relief effort, which involves providing food,tents and clothing for millions and the reconstruction ofhousing and infrastructure, including the many destroyedschools, is expected to take up to three years.
Education officials in Wenchuan county, the epicentre, arepressing neighbouring school authorities to accept more of thecounty's 14,000 children who have no place to resume theirstudies.
Thousands of injured have been transferred to otherprovinces and the capital for treatment to ease the pressure onlocal hospitals.
Song Liangwei, 9, had always dreamed of visiting Beijing,but not as a quake victim.
"I wanted to go to Tiananmen Square, to climb the GreatWall, and to watch the Olympic Games," he said.
(Writing by Nick Macfie; Additional reporting by LindsayBeck, Chris Buckley, Guo Shipeng and Phyllis Xu in Beijing;Editing by Sanjeev Miglani)