In 1986 a contract was awarded to a joint venture of Costain and Tarmac for construction of the UK’s first immersed-tube tunnel, to form a key part of the A55 Expressway which runs across North Wales. One of the first tasks was to excavate a basin, of 300 metres by 200 metres, at Morfa Conwy. In this basin, six large sections of the tunnel tube were cast. Each section was 118 metres long, 24 metres wide and 10.5 metres high, and weighed c.30,000 tons.
An opening to the estuary was then created, filling the basin with water. Buoyancy devices kept the tunnel sections afloat while they were towed to their final positions in the estuary and lowered into a trench dug across the bed.
The water-filled casting basin was subsequently equipped for its new role as a haven for leisure boats. Conwy Marina, which opened in 1992, provides 500 pontoon berths, making it the largest marina in Wales.
Postcode: LL32 8GU