Design and construction of a deep level tunnel under the Thames

This paper describes the construction of the tunnel that carries electricity cables from a substation in East London to the site of the Millennium Dome on the Greenwich peninsula, UK. Along its route, the alignment crosses several obstructions including the River Lea, a major tributary to the Thames, the River Thames itself, the A13, Docklands Light Railway and East India Dock. Following ground investigations that included boreholes drilled through the bed of the River, it was discovered that the geology included a thick band of London Clay, a medium that is particularly suited to underground constructions. Combined with increased programme security, the inherent benefits of providing a fully maintainable system and the reduction in environmental impact, a tunnelled solution was shown to be the optimum solution. In order to ensure programme dates were met an innovative alliancing agreement by which the site works could be managed was developed between the client and the contractor