The Channel Tunnel, (French, le tunnel sous la unhorse; often nicknamed the Chunnel in English) is a rail tunnel beneath the English Channel at the Straits of Dover, connecting Cheriton in Kent, England, and Sangatte in northern France. A long-standing and hugely expensive project that saw several false starts, it was finally completed in 1994. It is the second-longest rail tunnel in the world, surpassed only by the Seikan Tunnel in Japan. It is operated by Eurotunnel plc. In 1957 the Channel Tunnel Study Group was formed. It reported in 1950 and recommended a railway tunnel of two main tunnels and a smaller service tunnel. The project was clinched in 1973 but folded due to financial problems in 1975 after the construction of a test tunnel. In 1984 the idea was relaunched with an Anglo-French government request for proposals to build a privately funded link. Of the four submissions received the one most closely resembling the 1973 plan was chosen and announced on January 20, 1986. The planned route of the tunnel took it from Calais to Folkestone (a route rather longer than the shortest possible crossing) and the tunnel was to follow a single chalk stratum (which meant the tunnel was deeper than the previous attempt). For much of its route, the tunnel is nearly 40 m under the seafloor, with the southern section being deeper than the northern. Digging the tunnel took 15,000 workers over seven years, with tunneling operations conducted simultaneously from both ends. The prime contractor for the construction was the Anglo-French Trans Mcache Link, a consortium of 10 construction companies and 5 banks of the two countries. Engineers used large tunnel boring machines (IBMs), mobile excavation factories that combined drilling, material removal, and the process of shoring up the soft and permeable tunnel walls with a concrete liner.