The five-level dual-track ship locks of the mammoth Three Gorges Dam have passed their acceptance test after 13 years of construction and been officially opened to two-way traffic, officials announced on Monday.

Headed by Jiao Yong, vice minister of the Ministry of Water Resources and Xu Zuyuan, vice minister of the Ministry of Communications, a 49-member panel carried out the acceptance test from Saturday to Monday on the ship locks which started testing two-way traffic on May 1, two months ahead of schedule.

"The two-way traffic trials have been successful and tests have shown the lock will provide safe navigation for ships when the water level behind the dam rises from 156 to 175 meters." the panel said.

The engineering, metal structures, machinery and electronic equipment of the lifting facility for the 113-meter drop between upstream and downstream meet national and international standards, according to the panel.

Construction of the 6.4 km long lock, which cost 6.2 billion yuan (US$800 million), began in mountainous terrain on the northern bank of the Yangtze in 1994 and has been the only navigable route past the dam since 2003.

Four-level operation began in 2004. The lock has been restricted to one-way traffic, alternating every 24 hours, since September last year when work began to raise the beds of the two uppermost tiers of the lock from 131 to 139 meters.

The operation began on the southern route, which reopened on January 20, and work on the northern track started the same day. The Three Gorges Project is located on the middle reaches of the Yangtze River, China's longest and one of the country's most important inland waterways.

(Xinhua News Agency May 15, 2007)