The first undersea tunnel built in the Chinese mainland opened to traffic in the southeastern province of Fujian on Monday.

The highway tunnel joins Xiamen Island, one of the first special economic zones opened in the early 1980s, to Xiang'an district to its north under the Xiamen municipal jurisdiction.

The tunnel, which was designed for an average driving speed of 80 km per hour, is expected to cut the travel time between the two areas from one hour to nine minutes.

The 8.7-kilometer tunnel, 6 kilometers of which is under the sea with a maximum depth of 70 meters, cost a total of 3.2 billion yuan (US$468 million) and took four years and eight months to build.

It boasts the world's largest tunnel cross-section with a maximum area of 170 square meters, and consisting of three bores (17.5 meters wide and 13.5 meters high) with one for maintenance and emergency use and the other two each containing a three-lane highway.

The completion of the tunnel, which was designed and constructed by Chinese experts and companies, was a result of extremely tough work caused by loosening soil and a permeable sand layer under the water, said Zeng Chao, vice director of the Xiang'an tunnel project.

The project had garnered valuable experience for building more undersea tunnels, he said.

Fujian Province would see another two tunnels built in the near future, and a tunnel in the Jiaozhou Bay in east China's coastal Shandong Province was under construction, said Zeng.

Zeng said academic circles and industry insiders have called for the building of a undersea tunnel linking Fujian and Taiwan, noting the Xiang'an tunnel, located in the Taiwan Strait, can serve as a reference.

Ministry of Railways chief engineer He Huawu said last week the ever closer economic and trade ties between the mainland and Taiwan made the building of a cross-Strait tunnel urgently needed.

He, also a member of the Chinese Academy of Engineers, made the remark at a seminar on cross-Strait tunnel building attended by railway and tunnel building associations on both sides of the Strait and senior officials of the Fujian provincial government.

Official figures showed that the cargo volume transported from Taiwan to the mainland grew by an average 11 percent annually and the growth rate for the other way was 20 percent in recent years.

In December 2008, the two sides launched their first-ever direct cargo flights and shipping routes after a six-decade gap.

Plans for building cross-Strait undersea tunnels linking Chinese mainland and Taiwan Island had been under discussion for several years, said Zeng.

He also said it would take years to conduct a feasibility study and other preparations before the project, which would cover more than 100 km, could be started.

(Xinhua News Agency April 26, 2010)