China to build world's longest underwater tunnel

China plans to build the world's longest underwater tunnel beneath the Bohai Sea by 2026, connecting the port cities of Dalian in Liaoning province and Yantai in Shandong province.

The blueprint of the ambitious project is expected to be submitted to the State Council of the People's Republic of China in April, the China Daily reported Friday.

"Once approved, work could begin as early as 2015 or 2016," Wang Mengshu, a tunnel and railway expert at the Chinese Academy of Engineering, who has worked on the plan since 2012, was quoted as saying.

Wang said that the 123-km underwater tunnel will cost around 220 billion yuan ($36 billion).

The length of the tunnel will be more than the combined length of the world's two longest underwater tunnels - Japan's Seikan Tunnel and the Channel Tunnel between Britain and France.

"Using the tunnel, it will take only 40 minutes to travel from Dalian to Yantai," Wang said.

At the moment it is a 1,400-km drive and it takes eight hours by ferry.

Wang, however, emphasised that the safety of the project will be the top concern.

"The draft plan has two chapters discussing the potential dangers in the project and the emergency plan," he said.

Tan Guangzhong, Wang's colleague, said flooding is the biggest safety risk during tunnel construction.

He said, during the construction of the Seikan Tunnel, a slew of leaks led to financial losses and killed four workers.

Wang said the Bohai tunnel will be built at least 30 metres below the seabed, which is mostly hard rock.