Coordination of Complex Geotechnical Works at a Tideway Site in Central London

The Thames Tideway Tunnel is one of the largest current infrastructure projects in the UK: upgrading London’s Victorian sewer network and extending over 25km across the city. The Tideway construction site at the Earl Pumping Station raised a number of technical, managerial, logistical and environmental challenges. At this 'postage stamp' sized site, a 52m deep drop shaft intercepting a 6.45m TBM-dug tunnel, a combined sewage overflow chamber and other ancillary structures have been constructed within heavily contaminated ground immediately adjacent to the live Thames Water pumping station serving the local South London community. Solutions developed between the joint venture of Costain, Vinci Grands Projects & Bachy Soletanche (CVBJV) and its partners, required extensive geotechnical works including: a diaphragm wall installed using a hydrofraise, Cased Continuous Flight Auger (CCFA), rotary bored and Sectional Flight Auger (SFA) piling, deep soil mixing (both panels and columns), and grouting (as jet, chemical and cementitious permeation). This paper discusses the approaches to reviewing the challenges, risks and lessons learnt on and off site, with the aim of showcasing the cohesive implementation and integration of complex schemes within the very congested site space and challenging delivery programme.