Thames Tideway Scheme

The Thames Tideway Tunnel is an under-construction 25 km (16 mi) tunnel running mostly under the tidal section of the River Thames through central London, which will provide capture, storage and conveyance of almost all the combined raw sewage and rainwater discharges that currently overflow into the river. Bazalgette Tunnel Limited (BTL) is the licensed 'Infrastructure Provider' set up to finance, build, maintain and operate the Thames Tideway Tunnel. BTL is a consortium of investors that comprises Allianz, Amber Infrastructure, Dalmore Capital and DIF. From the licence award, BTL trades and is known to the public as 'Tideway'. On 3 November 2015, BTL received its operating licence from Ofwat, ensuring the start of the project.^[1]

Starting in 2016, construction of the Thames Tideway Tunnel will take seven to eight years, giving a target completion date of 2023.^[2] Once constructed, the main tunnel will have an internal diameter of 7.2 m (24 ft) and will run from −30 m (−98 ft) at Acton in the west of London for over 25 km (16 mi) under central London down to −70 m (−230 ft) at Abbey Mills in the east. It will connect 34 of the most polluting combined sewer overflows (CSOs), via transfer tunnels, and is expected to reduce the number of overflow events to a maximum of four per CSO per year at time of commissioning, increasing gradually due to effects of climate change and population growth.^[3] The tunnel will transfer the captured sewage to the Lee Tunnel for onward delivery to Beckton Sewage Treatment Works for treatment. The recycled clean water is then released into the River Thames.

The current estimate of its capital cost – excluding unknown financing costs and ongoing operations and maintenance costs – is £4.2 billion in 2012 prices.^[4]

Background

Built between 1859 and 1865, Sir Joseph Bazalgette's original London sewerage system was designed to capture both rainwater runoff and the sewage produced by four million people. As a failsafe, to prevent sewage backing up and flooding people's homes, Bazalgette's system has the ability to overflow into the Thames via 57 combined sewer overflows (CSO) along the banks of the river.

By 2012, the population of London had grown to an estimated eight million^[5] and Thames Water said that the current system lacked the necessary capacity. Bazalgette's original system does not serve all of these eight million people, as areas in outer London, built later, were provided with separate sewerage and rainwater infrastructure. Overflows have become increasingly common and now occur on average 50 times a year.^[6] These discharges, of combined raw sewage and rainwater, need to be reduced to comply with the EU's Waste Water Treatment Directive (UWWTD) and to improve the ecology of the river. An estimated total of some 39,000,000 m³ (3.9×10¹⁰ l), or 39 million tonnes, of storm sewage enters the river in a typical year.^[7]

Options assessment

Instigated in 2001, the Thames Tideway Strategic Study,^[8] conducted by a group comprising Thames Water, the Environment Agency, DEFRA and the Greater London Authority, was intended to assess the impact of the CSO discharges into the Thames and to identify objectives and propose potential solutions, while keeping costs and benefits in mind.

Outcomes

After four years, the Thames Tideway Strategic Study report was published in 2005, and outlined the following objectives:

1. To protect the ecology of the Tideway;
2. To reduce aesthetic pollution due to sewage-derived litter; and
3. Protect the health of recreational water users

Potential strategies

Four potential strategies were discussed:

1. Adoption of source control and sustainable urban drainage;
2. Separation of foul and surface drainage and local storage;
3. Screening, storage or treatment at the discharge point to river; and
4. In-river treatment

After evaluation of the potential strategies it was decided that only one, the screening, storage or treatment at the point of discharge, would fully meet the objectives. The remainder were found to be either impractical or insufficient to provide a solution, although a number of parties are questioning the validity of this conclusion, in particular relating to the dismissal of SUDs/blue-green infrastructure as a solution. Some groups that oppose the tunnel state that it is an unsustainable 19th-century solution to a 21st-century problem. They argue that rainwater should instead be captured or slowed down before entering the combined sewers, which would reduce pressure on capacity and take away the need for a tunnel.^[9]

Screening, storage and treatment

It was decided that the best method of implementing the screening, storage and treatment approach would be a three-pronged solution collectively known as the London Tideway Improvements.^[10]

The first part consisted of a deep storage and conveyance tunnel known as the Lee Tunnel. This 6.9 km (4.3 mi) long tunnel, running up to 75 m (246 ft) deep from Abbey Mills to Beckton captures 16,000,000 m³ (1.6×10¹⁰ l), or 16 million tonnes, annually from the single largest polluting CSO in London. Thames Water awarded the construction contract to the MVB joint venture, made up of Morgan Sindall, VINCI Construction Grands Projets and Bachy Soletanche, in January 2010. The cost is an estimated £635 million. The construction of the tunnel began in 2010^[11] and on 28 January 2016 Mayor of London Boris Johnson opened the tunnel for service.^[12]

The second part is the £675 million project to modernise and extend London's five major sewage treatment works.^[13] This is aimed at increasing capacity at the works so that a greater volume of sewage can be treated, greatly reducing the need for storm discharges to the river. The five treatment works (with planned improvements) are:

• Mogden Sewage Treatment Works – a £140 million upgrade to extend sewage treatment capacity by 50 per cent^[14]
• Crossness Sewage Treatment Works – a £220 million upgrade to extend treatment capacity by 44 per cent^[15]
• Beckton Sewage Treatment Works – a £190 million upgrade to extend treatment capacity by 60 per cent^[16]
• Riverside Sewage Treatment Works – an £85 million upgrade as part of a major scheme to help improve water quality in the River Thames and produce renewable energy on site^[17]
• Long Reach Sewage Treatment Works – a £40 million upgrade in Dartford, as part of a major scheme to help improve water quality in the River Thames^[18]

These upgrade works will also improve the standard to which the sewage is treated at each of the works, further boosting the water quality of the Thames.

The final part of the London Tideway Improvement plan is another deep storage and conveyance tunnel, which will intercept the outflows from London's most polluting CSOs and direct them to the sewage treatment works for processing before they can enter the river. This part is known as the Thames Tideway Tunnel.

Thames Tideway Tunnel planning and consultation

Initial design and phase 1 consultation

Following the Thames Tideway Strategic Study, Thames Water consulted with relevant authorities to get feedback from stakeholders who would potentially be affected by the construction of the Thames Tideway Tunnel. Thames Water sought feedback on the proposed tunnel routes and potential locations of construction sites.^[19]

Initially three potential tunnel routes were considered:

1. River Thames Route – the alignment of this route broadly followed the river from west London to Beckton STW and would cut across the Greenwich Peninsula, reducing the length of the tunnel at a location where there are no CSOs to be intercepted along the river.
2. Rotherhithe Route – the alignment of this route was similar to the River Thames route, but would have cut across the Rotherhithe Peninsula as well as the Greenwich Peninsula, reducing the length of the main tunnel by approximately 1.8 km (1.1 mi) but requiring longer connection tunnels from some CSOs.
3. Abbey Mills Route – this route was different from the River Thames and Rotherhithe routes in that it connects the Thames Tunnel to the head of the Lee Tunnel at the Abbey Mills Pumping Station. This would have followed the same route as first two options but then deviated from the river toward Abbey Mills. The main tunnel length would be approximately 9 km (5.6 mi) less than the River Thames Route and save approximately £900 million.

Route and sites selection

A long list of 373 potential sites was created using a desktop survey of the land on either side of the 34 most polluting CSOs (as identified in the Thames Tideway Strategic Report). These sites were then further evaluated against more detailed planning, engineering, environmental, property and community considerations resulting in a shortlist of sites.^[20]

The three tunnel routes, as well as the shortlist of sites, were then put out for consultation between September 2010 and January 2011.^[19] In total 2,389 feedback forms (both online and hard copy), 480 pieces of correspondence and five petitions were received.

In response to the comments received, changes and improvements to some of the sites, including the potential use of alternative sites and alternative technical solutions, were considered. Based on this a round of interim engagement took place between March 2011 and August 2011.^[19] During this phase residents around 11 specific sites were sent letters explaining that these sites were being considered as alternative sites,^[21] and inviting residents to attend drop-in sessions to pose questions and gain a better understanding of the project. In total ten two-day sessions and one community liaison meeting was held. These were attended by over 800 people. In all 168 comment cards and 147 pieces of site specific correspondence was received and considered.^[19]

Based on this first round of consultation and interim engagement it was recommended that, for the project to be as cost-effective as possible and cause the least disruption, while still meeting the requirements of the UWWTD, the preferred scheme for the Thames Tideway Tunnel would need to involve:

• the shorter Abbey Mills route
• a main tunnel, 23 km (14 mi) long with an internal diameter of 7.2 m (24 ft);
• the direct interception of 21 CSOs;
• the indirect interception of a further 12, and a local solution for the remaining CSO;
• the selection of five out of 52 shaft sites from the final shortlist, including three where main shaft sites are combined with CSO interception sites; and
• the selection of seventeen out of 71 CSO sites from the final shortlist.

The new preferred route and sites were then sent out for a second round of public consultation and feedback.^[19]

Phase 2 and targeted consultation

The second phase of consultation was carried out between November 2011 and February 2012^[22] when local authorities, land owners, local businesses and communities were consulted on:

• The need for the project and whether a tunnel was the most appropriate solution
• The preferred tunnel route (including the detailed alignment of the tunnel)
• Preferred sites and permanent works (taking into account the feedback received from the first phase of consultation such as the move from greenfield to brownfield sites)
• Detailed proposals for the preferred sites (again taking into account the feedback from the phase one consultation)
• The effects the project would have (as outlined in the preliminary environmental information report)

A total of 1,374 feedback forms (online and hard copy), 4,636 pieces of correspondence and nine petitions were received.^[22]

Following this consultation, and taking into consideration all the feedback received, the proposed route was finalised as the Abbey Mills route and the preferred construction and drive sites were identified. Several sites were also identified as needing further, targeted consultation which resulted in further refinement and improvement of designs at those sites.

Site list and type

• Acton Storm Tanks – main tunnel reception and CSO interception^[23]
• Hammersmith pumping station – CSO interception and connection tunnel drive site^[23]
• Barn Elms – CSO interception and connection tunnel drive site^[24]
• Putney Embankment foreshore – CSO interception and connection tunnel drive site^[25]
• Carnwath Road riverside – main tunnel drive and reception and connection tunnel reception site^[26]
• Dormay Street CSO- interception and connection tunnel drive site^[27]
• King George’s Park – CSO and connection tunnel reception site^[28]
• Falconbrook pumping station – CSO and connection tunnel drive site^[29]
• Cremorne Wharf Depot – CSO interception and connection tunnel drive site^[30]
• Chelsea Embankment foreshore – CSO interception and connection tunnel drive site^[31]
• Kirtling Street – main tunnel double drive site^[32]
• Heathwell pumping station – CSO interception and connection tunnel drive site^[33]
• Albert Embankment foreshore – CSO interception and connection tunnel drive site^[34]
• Victoria Embankment foreshore – CSO interception and connection tunnel drive site^[35]
• Blackfriars Bridge foreshore – CSO interception site^[36]
• Shad Thames pumping station – system modification site^[37]
• Chambers Wharf – main tunnel drive and reception site^[38]
• Earl pumping station–CSO interception site^[39]
• Deptford Church Street – CSO interception site^[40]
• Greenwich pumping station – CSO interception and connection tunnel drive site^[41]
• King Edward Memorial Park – CSO interception site^[42]
• Bekesbourne Street – system modification site^[43]
• Abbey Mills pumping station – main tunnel reception site^[44]

Proposed design and construction

To build the Thames Tideway Tunnel, four tunnel boring machines (TBMs) will be needed to excavate the main tunnel plus at least two others for smaller connection tunnels. It will also require two types of construction sites: main tunnel sites, where the TBM will either be launched or received, and CSO sites, where interception tunnels and a connection culvert will need to be built to connect the existing sewer to the new tunnel.^[45]

Construction of the shafts at the CSO sites, to transfer flows from the existing sewer to the tunnel, will vary depending on the depth, the amount of flow they need to carry and the geology. The shaft will be a concrete cylinder with an internal diameter of 6–24 m (20–79 ft) and 20–60 m (66–197 ft) deep. Ventilation structures at CSO sites to allow air in and out of the shaft will also need to be built. Construction at these sites is expected to take between  2 ¹⁄₂ and  3 ¹⁄₂ years and once complete each site will be landscaped.^[45]

At the main drive sites, four main activities need to take place: shaft construction (where a concrete cylinder 25–30 m (82–98 ft) in diameter and about 40–60 m (130–200 ft) deep would need to be constructed), tunnelling preparations (preparing the site for arrival of the TBM), TBM assembly and lowering into the shaft, and driving the TBM to excavate the main tunnel.^[45]

As the TBM moves forward precast concrete segments will be brought in and fixed together to create the tunnel wall. Excavated material will then be transported out the tunnel via a conveyor belt and will be processed before being taken off site. In order to minimise disruption, Thames Water have committed to use the river as much as possible to transport materials both in and out of the construction sites. At the main tunnelling sites, works are expected to take place 24 hours a day.^[46]

Planning application

In October 2012, the deadline for the Thames Tideway Tunnels' Section 48 closed.^[47] This lasted 12 weeks and was the last opportunity for the public to have their say on the updated proposal.

The Application for Development Consent – a detailed plan for construction of the Thames Tideway Tunnel – was delivered to the Planning Inspectorate on 28 February 2013. The Inspectorate then had 28 days to decide whether the application is valid and whether the consultation undertaken was adequate.^[48] On 27 March 2013, it was confirmed that the application was valid and that Thames Water’s consultation for the project had been adequate.^[49] All the application documents were made available in their own section of the Planning Inspectorate's National Infrastructure website. Thames Water also made the documents available for scrutiny at six public locations along the tunnel’s proposed route, three either side of the river.

On 3 June 2013, it was announced that the Secretary of State for Communities and Local Government had appointed five inspectors (Jan Bessell, Libby Gawith, Emrys Parry, Andrew Phillipson and David Prentis) as the examining authority to consider any matters arising.^[50] As part of this process, interested parties would be able to make representations.

A preliminary meeting, open to those who had registered an interest, began on 12 September 2013 at the Barbican Centre.^[51] Chaired by the Planning Inspectorate, this determined how the examination would be carried out, including consideration of more detailed hearings on site-specific matters, as well as project-wide issues. Once the Inspectorate concluded its examination of the application, a recommendation on whether or not to grant approval (by issuing a development consent order) could be submitted to Government ministers to make the final decision.

Planning acceptance

On 12 September 2014, the UK Government approved the plans,^[52] overriding some of the findings of the Planning Inspectorate.^[53][54][55] The decision has given rise to at least three Judicial Reviews.^[56][57]

Funding and delivery

The budget for the scheme has steadily increased since it was first put forward – for example, the stated budget in 2004 was estimated at £1.7bn, which included the Lee Tunnel and sewage treatment works upgrade costs. In the words of the Consumer Council for Water in 2011:

"The estimated cost of the project has escalated, from £1.7bn in 2004 (including Lee Tunnel and sewage treatment works (STW) costs) to £2.2bn in 2007 (also including Lee Tunnel and STW costs) to £3.6bn now for the shorter Thames Tunnel as far as Abbey Mills, plus some £1bn for the Lee Tunnel and upgrade of works at Beckton. The total costs of all the Tideway schemes have therefore increased from £1.7bn six years ago to £4.6bn today (all costs at relevant year prices). There is no guarantee that the current estimate will not be subject to further escalation."^[58]

Less than a year after this writing, in November 2011, a further £500 million was added to the estimate.^[59]

Following detailed analysis it was decided that the best means to deliver the project would be through a regulated infrastructure provider (IP)^[60] as this would maximise value for money. The IP, originally to be formed through a competitive process starting in the spring of 2013, will hold its own license from the industry regulator, Ofwat, and will build, manage and maintain the tunnel.

In January 2013, it was announced that procurement of the IP was to be delayed because Thames Water needed more time to firm up the funding model to secure financial assurances from the government. The subject of taxpayer support for the construction of a tunnel is a source of controversy, with opponents arguing that the government should not bear risks associated with the project. In a letter to the Financial Times in November 2012, Sir Ian Byatt (former Director General of Ofwat) and politician Simon Hughes MP stated:

"If Thames is unwilling to make a rights issue, the owners, Macquarie, should be expected to return funds to the utility. If they do not, Thames should go into special administration (allowing for continued service to customers) and another company or financier allowed to take over its activities."^[61]

However, procurement for main contractors (who would eventually be contracted to the IP) for up to three packages of work valued at around £500m each started in the summer of 2013.^[62] On 29 July, Thames Water announced that a contract notice for work on the tunnel had been published in the Official Journal of the European Union (OJEU). Following prequalification questionnaires, Thames Water invited shortlisted contractors to tender between November 2013 and April 2014.^[63]

The successful contractors for the three main tunnelling contracts were announced in February 2015:^[64][65]

• West: Joint venture of BAM Nuttall, Morgan Sindall and Balfour Beatty Group
• Central: Joint venture of Ferrovial Agroman UK and Laing O'Rourke Construction
• East: Joint venture of Costain, Vinci Construction Grands Projets and Bachy Soletanche

In August 2015, the independent investors to finance and deliver the scheme were confirmed. Bazalgette Tunnel Limited, a new special-purpose company appointed to take the project forward, received its licence from Ofwat as a new regulated utilities business, separate from Thames Water.^[66][67] The special-purpose company is backed by pension funds and other long-term investors represented by Allianz, Amber Infrastructure Group, Dalmore Capital and DIF.^[66]

Controversy

Since its initial proposal, questions were raised on the scheme based in its cost, the location of construction sites and duration and associated disruption of the works, and whether a tunnel is actually necessary or indeed the right solution for London and Thames Water customers.

The £4.2bn cost of the Thames Tideway Tunnel project is to be wholly funded by Thames Water customers. This has angered some customers who believe the company has benefited from tax breaks sanctioned by industry regulator Ofwat, when it was allowed to add debt to its balance sheet, reducing its tax payments while at the same time allowing its shareholders to receive dividends – money they feel should have been spent on the Thames Tideway Tunnel.^[68] Thames Water has maintained it has done nothing unusual by raising debts to reduce tax bills and is following conventional practice. It says the money raised was used for essential maintenance and upgrade works, although some have asked questions about how Thames Water has paid so little corporation tax at the same time as distributing funds to its shareholders.^[69]

Those living alongside proposed sites are also concerned about the noise, disruption and the potential loss of public space resulting from construction. To address this Thames Water has put together a Code of Construction Practice (CoCP) which outlines both site-specific and project-wide requirements and measures that will be applied to minimise the impacts of the construction and how best practice standards and requirements will be implemented across all sites and contracts.^[70] The Code also covers transport (both road and river transport), noise and vibration mitigation, air quality and water resources, land quality, waste management and resource use, ecology and conservation and historic environment.^[71] In the report that concluded its inspection of these documents, the Planning Inspectorate found that Thames Water had "underestimated of impacts on those that have been identified as having a significant effect and underestimated the number of receptors experiencing a significant effect" (12.97) and concluded "We do not consider that [Thames Water's] proposals meet the first aim of the NPS test to avoid significant adverse impacts on health and quality of life from noise" (12.357).^[54]

Tunnel sceptics maintain that a sustainable urban drainage solution (SUDS) or green infrastructure would remove the need for the tunnel. Replacing paved, impermeable surfaces in London with permeable options and implementing green roofs, swales and water butts would promote the infiltration of rain-water preventing it from reaching the combined sewer system thus reducing peak flows and limiting the number of CSO overflows. Opponents also feel that these measures would provide the level of control required whilst being cheaper than the proposed Thames Tideway Tunnel.^[72][73] Green infrastructure would have further benefits for London in addition to addressing the rainwater overflow problem, such as:

1. Increased resilience to drought and floods,
2. Reduction in urban air pollution,
3. Climate change mitigation – contrasted to the tunnel's significant carbon footprint,^[74]
4. Enjoyment, aesthetics and health benefits of green spaces and nature,^[75]
5. Reduced urban heat island effect and associated reduction in cooling load and carbon emissions,
6. Improved urban biodiversity.
7. Earlier avoidance of EU fines for not meeting water standards than under the scheme.

The earliest customers’ bills would be affected was 2014–15, with charges rising gradually after that. The project was estimated to add up to £70 to £80 to average annual wastewater bills from around 2019 (excluding inflation). However, these figures were subsequently revised downwards; in August 2015, the impact was expected to be around £20 to £25 per year by the mid-2020s.^[66][76]

References