The Thames Tideway Tunnel is the biggest infrastructure project the UK water sector has ever seen. Dubbed the “super-sewer”, the project involves building a 25km tunnel under the River Thames to help tackle the problem of overflows from the capital’s Victorian sewers and protect the river from rising pollution for at least the next 100 years.
Needless to say, it is an exciting project, and one which has earned its “super-sewer” moniker, according to Tideway engineer Gareth Thomas. He says it is an enormous undertaking on a scale not seen in Europe before. When complete, the sewer will intercept vast volumes of storm sewage, forming a strategic artery to enhance the operation of London’s sewer network and the quality of the River Thames for generations to come.
But excavating such a huge tunnel through one of the busiest cities in the world is a tough task. Keeping the noise down for a wide range of neighbours, working with utility and transport companies to avoid any interference with their networks, and operating in an environmentally friendly way are just some of the challenges facing Tideway.
Utility Week took a trip along the Thames to see the progress being made and discover how Tideway is overcoming the many obstacles it is encountering.
Working along the River Thames
Eleven of the project’s 24 sites are based on the foreshore of the River Thames. Some of these have required building out into the river, to give Tideway the space it needs for its construction works.
The cofferdam built into the river to build the shaft in Bermondsey is complete. Meanwhile, the construction of cofferdams at Blackfriars, Victoria Embankment, Chelsea Embankment, Albert Embankment and King Edward Memorial Park continues. After construction is complete these areas will provide seven new areas of public realm along the river, creating new areas of land where Londoners and visitors can get closer to the River Thames.
Tideway’s work so far has also included strengthening the river wall and building new docks to allow barges to reach the sites to bring materials in and take away spoil during tunnelling.
Creating a new generation of engineers and construction workers
At the peak of construction, 4,000 people will be working on the Thames Tideway Tunnel. One of Tideway’s priorities is ensuring it has enough skilled operatives to work on such a large infrastructure project.
One in 50 jobs will be an apprenticeship. Tideway says it is on target and has now offered more than 100 apprenticeship opportunities on the project. These range from civil engineering to construction, boat-masters, business administration and digital engineering.
Building underground in London
The route of the tunnel generally follows the route of the River Thames, passing under 67 bridges and 45 tunnels, which include tube lines and power networks. At Nine Elms in Battersea, construction is happening near Battersea Power Station, the Northern Line Extension and several residential and commercial developments.
Designing the tunnel and ongoing construction requires Tideway to work with companies including Thames Water, UK Power Networks, Transport for London and other organisations that keep London running.
As well as navigating the utilities and services that run under the city, the project has also had to consider London’s varying ground conditions. Tideway is tunnelling through a range of materials including the Lambeth system – which consists of gravels and chalk – London clay in west London and chalk in east London.
Tideway’s tunnel boring machines have been built to take into account the different ground conditions, with slurry machines being used in the east section and Earth Pressure Balance machines in the central and west sections.
Being a good neighbour
Building in the centre of London means Tideway’s sites are often close to people. T he company has built noise-containing enclosures over the main drive site shafts in Fulham and Battersea, and one is under construction at the main drive site in Bermondsey.
These will help minimise the amount of noise when tunnelling starts and when spoil from the tunnel is being transferred on to barges to be taken away. Tideway has also worked with its contractors to develop innovations such as an electric hydrofraise machine, developed by the team building the east section of the tunnel, which the company says is more environmentally friendly and quieter.
The company holds regular meetings and drop-in sessions for members of the community near its sites and has involved local artists and residents in the design of the hoardings around the sites.
Keeping everyone working on the project safe, healthy and happy is a fundamental philosophy at Tideway, which says it does things “safely, or not at all”. As part of their project induction, every member of the workforce – from tunnel operatives to delivery drivers and office staff – goes through an immersive, multimedia health and safety training day called Epic (employer’s project induction centre). Around 14,000 people so far have gone through the programme.
During construction of the Thames Tideway Tunnel, Tideway plans to transport as much material by river as it can. Where this isn’t possible, it has committed to using the safest vehicles possible. It has 22 “low entry cab” vehicles in use across the project, which increase the amount of direct driver vision to provide a much better chance of drivers seeing vulnerable road-users, especially cyclists. It also recently launched another Epic day specifically for HGV drivers working on the Thames Tideway Tunnel project.
Tideway also says it is committed to ensuring it is a sustainable, environmentally friendly project during construction.
Through its “sustainable transport – more by river” strategy, it aims to transport 90 per cent of materials by river. It will take an extra 200,000 HGV movements off London’s roads than originally planned, to further limit pollution, congestion and to protect cyclists and pedestrians.
The company says its teams are “constantly looking at ways to increase sustainability during construction”. Recently, operatives working at its Albert Embankment site started to collect plastic items that were gathering around the site on the foreshore. This plastic is processed and sent to a factory in Scotland that turns it into “plaswood” – a recycled material that can be used to make products, including items such as the plastic boat that transported the Utility Week team down the river.
Construction of the Thames Tideway Tunnel has been divided into three sections – East, West and Central – with each section being built by a different joint-venture.
The construction in the west region is being delivered by a joint venture of BAM Nuttall, Morgan Sindall and Balfour Beatty Group. This contract is known as Tideway West, with work taking place from Acton to Fulham.
The construction in the central region is being delivered by a joint venture of Ferrovial Agroman UK and Laing O’Rourke Const ruction. This contract is known as Tideway Central, with work taking place from Fulham to Blackfriars.
The construction site in the east region is being delivered by a joint venture of Costain, Vinci Construction Grands Projets and Bachy Soletanche. This contract is known as Tideway East, with work taking place from Bermondsey to Stratford.
Sites and progress
King Edward Memorial Park Foreshore
• Intercepts the North East Storm Relief combined sewer overflow (CSO)
• Online shaft straight into the tunnel is 60m deep
• Work involves building a cofferdam into the foreshore at 4,300 sqm
• New area of public realm will extend approximately 33m
• One of three main shafts for the tunnel
• Once complete, the shaft will be 30m wide and around 70m deep
• Noise enclosure currently under construction to minimise noise
• Diaphragm walling for the main shaft was carried out using an electric hydrofraise to minimise noise and environmental impact
• Tunnel boring machine will arrive on site by river next year, with tunnelling due to start later next year
Blackfriars Bridge Foreshore
• Point where Fleet sewer discharges into the River Thames
• Shaft here will be 24m and connect to the tunnel at a depth of 53m
• Additional public realm will cover approximately
• New foreshore dimensions will be 280m long by 30m wide
Victoria Embankment Foreshore
• New foreshore structure will extend 22.5m into river
• Work here will intercept sewage overflows from Regent Street and Northumberland Street CSOs
• It will also provide high-level overflow from the Bazalgette interceptor sewer in the Victoria Embankment to control for three other CSOs: Savoy Street, Norfolk Street and Essex Street
Albert Embankment Foreshore
• Intercepts Clapham (upstream) and Brixton (downstream) CSOs
• Shaft is 16m in diameter and 48m deep
• Main drive site for the central section of the tunnel – shaft is complete, around 30m diameter and 55m deep
• The two tunnel boring machines that will dig the central section of the main tunnel are in the ground at Battersea – tunnelling will start later this year
Chelsea Embankment Foreshore
• Chelsea Embankment is the third Bazalgette Embankment, after Victoria and Albert
• Intercepts the Ranelagh CSO
• Shaft will be 12m diameter and 45m deep
Falconbrook Pumping Station
• Intercepts Falconbrook Pumping Station CSO
• The site is 500m back from the river
• Shaft 9m diameter, 40m deep
• Main drive site for the west section of tunnel. The shaft here is 25m diameter, around 50m deep
• From here, Rachel, the main tunnel boring machine for the west section, will tunnel 6km west to Acton from early next year
• Shaft will also receive the smaller tunnel boring machine, Charlotte, which is digging the 1.1km Frogmore Connection Tunnel from Wandsworth
• Tideway currently constructing a conveyor structure on site behind the river walls, to transfer spoil from tunnel on to barges
• Work here includes strengthening the tunnel walls to allow tunnel construction to commence next year