Digging from Both Sides

Construction began in 1988 using 11 tunnel boring machines (TBMs). Teams dug simultaneously from England and France through a chalk marl layer 40 meters beneath the seabed:

• Each TBM weighed 1,100 tonnes and was as long as two football fields
• Workers removed 4.9 million cubic meters of spoil — the French dumped theirs at sea, the British used theirs to create Samphire Hoe, a new piece of land
• The two sides met on December 1, 1990, just about 36 cm off horizontally and 58 cm off vertically

That accuracy over nearly 38 km of undersea tunnel remains one of the greatest precision engineering feats in history.