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Cofferdam of Three Gorges demolished in seconds (Xinhua) Updated: 2006-06-06 16:11 Fish dispelled away
Before the demolition operation,
about 90 percent of fish stocks have been dispelled 500 meters away from the
Three Gorges dam area, less than one hour before the explosion of the protective
dam, according to ultrasonic monitoring result in the reservoir.
Two
dispelling vessels drove in shore at around 3:00 p.m., as all navigation near
the world's largest hydro-power project in the middle of Yangtze River was
temporarily blocked off for the demolition of the cofferdam.
A total of
191.3 tons of explosives, enough to topple down 400 10-storey buildings, have
been installed to demolish the concrete cofferdam, which is located 114 meters
away from the just completed Three Gorges Dam, the world's largest concrete
reservoir dam. Debris from the explosion will be measured at 180,000 cubic
meters.
The detonators were triggered off at about 4:00 p.m. The
whole demolition operation lasted around 12 seconds.
Professor Tan
Xichang, who took in charge of the fish dispelling operation, said that nine
biologists used electric devises to create high-pressure electric pulse in water
to dispel fish schools near the cofferdam, including such rare species as
Chinese sturgeon, river dolphins and mullet.
"Sturted animals won't
return to the area at least for an hour, " said Tan, who referred to the
experiment result from the previous trial operation.
Tan explained that
the explosion and the accompanied shock waves would evitablely hurt some fish
species.
"Our job is to dispel water species away from an area of 700
square meters close to the cofferdam before the designated explosion," said Tan.
Nine biologists from the Water Biological Engineering Institute under
the Chinese Academy of Sciences took the two vessels loaded with sonar detectors
and electric machineries to carry out the mission.
The team of experts
have surveyed location of fish shoals within 600 meters of reaches from the
cofferdam before the operation.
Professor Tan said that the dispelling
method by using high-pressure electric pulse is China's patented scientific
breakthrough, which proved effective in driving away creatures in water without
hurting them.
The Three Gorges reservoir has become a natural habitat
for many endangered freshwater species, since the cofferdam exerted its role to
store water in the middle reaches of China's longest river of Yangtze in
2003.
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