Channel Tunnel terms of the Concession, Eurotunnel was obliged to investigate a cross-Channel road tunnel. In December 1999 road and rail tunnel proposals were presented to the British and French governments, but it was stressed that there was not enough demand for a second tunnel. A three-way treaty between the United Kingdom, France and Belgium governs border controls, with the establishment of "control zones" wherein the officers of the other nation may exercise limited customs and law enforcement powers. For most purposes these are at either end of the tunnel, with the French border controls on the UK side of the tunnel
Channel Tunnel at the English portal, caused concerns. Identified by the 1964–65 geophysical survey, the Fosse Dangaered is an infilled valley system extending below the seabed, south of the tunnel route in mid-channel. A 1986 survey showed that a tributary crossed the path of the tunnel, and so the tunnel route was made as far north and deep as possible. The English terminal had to be located in the Castle Hill landslip, which consists of displaced and tipping blocks of lower chalk, glauconitic marl and gault debris. Thus the area was stabilised by buttressing and inserting drainage adits. The service tunnel acted