TECHNICAL | SHAFTS, CAVERNS - BTS HARDING PRIZE COMPETITION
SHAFT SLIPFORM SECONDARY LINING - THAMES TIDEWAY WEST
The Harding Prize Competition is named after the founder of the British Tunnelling Society, Sir Harold Harding, and is for entrants under the age of 33. Shortlisted papers were presented to the BTS evening meeting on 19 March, at the Institution of Civil Engineers, in London.
Matthew Gibson, a Section Engineer with BMB JV, was winner of the 2026 Competition with a paper entitled ‘Construction of the Shaft Slipform Secondary Lining at Thames Tideway West’.
1. INTRODUCTION London’s rapidly growing population, now around nine million, has placed significant strain on the city’s critical infrastructure. The existing sewer network, designed by Sir Joseph Bazalgette in the Victorian era over 150 years ago, remains a remarkable feat of engineering but was built to serve a much smaller population. Today, it has capacity for less than half of London’s residents. As a result, millions of tonnes of untreated sewage are discharged into the River Thames during periods of rainfall, causing severe environmental damage and water quality issues. To address this challenge, the Thames Tideway
Tunnel, aptly named the ‘Super Sewer’, was conceived. The project intercepts sewage at 34 of the most
Right:
Slipforming for secondary lining at shaft on Thames Tideway West
polluting combined sewer overflows (CSOs), where flows would historically spill directly into the river, and divert them into a new tunnel system. The tunnel is 7.2m-diameter and extends 25km from
Acton in West London to Abbey Mills Pumping Station, in East London. At Abbey Mills, it connects into the Lee Tunnel, which conveys flows to Beckton Sewage Treatment Works. The route, shown in Figure 1, generally follows the profile of the River Thames, varying in depth from 31m below ground level, in the West, to 70m in the East, with flows gravity fed along the network at a gradient of 1m per 790m. The project represents an estimated £5 billion
investment and is scheduled for completion over a ten- year period from 2016 to 2026.
18 | April 2026
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