Channel Tunnel, popularly called the "Chunnel," a three-tunnel railroad connection running under the English Channel, connecting Folkestone, England, and Calais, France. The tunnels are 31 mi (50 km) long. There are two rail tunnels, each 25 ft (7.6 m) in diameter, and a central tunnel, 16 ft (4.8 m) in diameter, that is used for maintenance and ventilation. The depth of the tunnels below the seabed averages about 150 ft (45 m). The project is a joint English and French venture, with a 55-year concession granted to Eurotunnel, a private company, and is the centerpiece of a high-speed rail link between London and Paris. The project began with the signing of the Channel Tunnel Treaty between France and Britain in 1986; passenger service began in 1994. A higher than expected cost of digging the tunnels and lower than predicted tunnel traffic levels left Eurotunnel with huge debts, the repayment of which strained the finances of the company, threatened the company with insolvency, and led a French court to grant (2006) Eurotunnel creditor protection while the company reorganized (as Groupe Eurotunnel in 2007) and restructured its debt.
See G. Anderson and B. Roskrow, The Channel Tunnel Story (1994); T. Byrd, Making of the Channel Tunnel (1994); C. J. Kirkland, ed., Engineering the Channel Tunnel (1995).