China Proposes Worldâ€™s Longest Underwater Tunnel Under Bohai Sea - Businessweek China may invest 220 billion yuan ($36 billion) to build the worldâ€™s longest tunnel beneath the Bohai Sea to connect the northeastern city of Dalian to Yantai in Shandong province, the state-run China Daily said today. Proposals for the 123-kilometer (76 miles) tunnel, which is targeted for completion in 2026, may be submitted to the central government in April, the newspaper said, citing Wang Mengshu, an engineer working on the project. A feasibility study taking two to three years could begin as early as 2015, the report said. The proposed tunnel will be the latest large-scale project undertaken by China if approved. The worldâ€™s second-largest economy has poured billions in past years to build infrastructure to spur growth, which may be more critical with gross domestic product forecast by economists to expand this year at the slowest pace since 1990. Story: Foxconn Might Assemble Your Next Smartphone in Indonesiaâ€”Using Robots The estimated project cost, at about 6 percent of Chinaâ€™s 4 trillion-yuan stimulus package during the 2008 global financial crisis, may boost consumption of steel to cement. The major ports of Qinhuangdao, Tianjin and Caofeidian are located along the coast of the Bohai Sea. The tunnel will operate a rail link that will cut travel time between the two cities to 40 minutes, from about eight hours by ferry currently, the newspaper said. It will be more than twice the length of Japanâ€™s Seikan Tunnel, currently the worldâ€™s longest undersea tunnel at 53.9 kilometers. Trains in the Bohai tunnel will run at about 220 kilometers an hour, while passenger vehicles will ride through the tunnel on rail carriages, the newspaper said.