Japan–Korea Undersea Tunnel at about ₩100 trillion (approx. US$90 billion), which would produce an extremely low benefit-to-cost result. In 2014, the South Korean Busan Development Institute estimated the undersea tunnel could create ₩54 trillion won (원54T, or US$53 billion) in economic benefits and provide about 45,000 jobs. In an April 2009 editorial, former Justice Ministers Daizō Nozawa of Japan and Kim Ki Chun of South Korea remarked on some of the similarities of the proposed Japan–Korea tunnel to the world's present longest undersea tunnel. The Channel Tunnel runs for 50.45 km linking the United Kingdom and France, and opened in May 1994: At
Channel Tunnel techniques from the oil industry were employed. Tunnelling was a major engineering challenge, with the only precedent being the undersea Seikan Tunnel in Japan, which opened in 1988. A serious risk with underwater tunnels is major water inflow due to the pressure from the sea above, under weak ground conditions. The tunnel also had the challenge of time: being privately funded, early financial return was paramount. The objective was to construct two rail tunnels, apart, in length; a service tunnel between the two main ones; pairs of cross-passages linking the rail tunnels to the service one at spacing; piston relief