Blackwall Tunnel from immigrants; the tunnel lining was manufactured in Glasgow, while the manual labour came from provincial England, particularly Yorkshire. The tunnel was officially opened by the Prince of Wales on 22 May 1897. The total cost of the tunnel was £1.4 M and 800 men were employed in its construction, during which seven deaths were recorded. The southern entrance gateway to the tunnel, also known as Southern Tunnel House, was designed by LCC architect Thomas Blashill and was built just before the tunnel was completed. It comprises two floors with an attic. Today the western bore is only used for
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