Northern Line Extension (Interim)

CEEQUAL Excellent (75.2%) – Interim Client & Outline Design Award
Version 5, August 2018 | London, UK

Client: London Underground
Designer: Mott MacDonald
Contractor: Laing O’Rourke

Assessors: Amy Cox, Vivek Deva (Mott MacDonald)

Project summary

The Northern Line Extension (NLE) is a project on behalf of London Underground Limited (LUL), with Ferrovial Agroman Laing O’Rourke (FLO) Joint Venture as Principal Contractor and Mott MacDonald as the primary Designer. It extends the existing Charing Cross branch of the Northern Line from the Kennington Loop to a new terminus south of Battersea Power Station.

Economic development and population growth is supported by this project within the Vauxhall, Nine Elms and Battersea Opportunity Area, and overcrowding on the Northern Line South of Kennington, and the Victoria Line north of Vauxhall will be alleviated through it.


The project includes:

a. Two new fully functional stations – one at Nine Elms and one at Battersea.

b. Two permanent ventilation / intervention shafts at Kennington Park and Kennington Green.

c. Two running tunnels, one northbound and one southbound, consisting of: i SCL Launch Tunnel ii TBM driven, segmentally lined tunnels from the SCL launch tunnels to the shafts iii SCL running tunnels from the shafts towards the Kennington loop.

d. Step Plate Junction into the Kennington Loop.

e. SCL overrun tunnels beyond Battersea station.

f. Five tunnel cross passages at the following locations: i Cross passages CP1 and CP2 between Nine Elms Station and the Step Plate Junction into the Kennington Loop ii Cross Passage CP3 between Nine Elms and Battersea stations iii Cross passages CP4 and CP25 in the overrun tunnels south of Battersea Station.

g. Four new cross passages in Kennington station.

The application for the London Underground (Northern Line Extension) Order was approved by the Secretary of State for Transport in November 2014. In making the order, the Secretary of State granted deemed planning permission for the development under Section 90(A) of the Town and Country Planning Act 1990.

Project Strategy

Under the project strategy section, the scheme clearly delivers significant economic benefit to wider society as identified through its socio-economic impact assessment. The extension is the catalyst for delivering up to 5,500 additional residential units and 14,000 additional jobs in the Vauxhall, Nine Elms and Battersea Opportunity Area than if it were not to be built.

This is a significant share of the London Plan targets and of the Boroughs’ housing targets. In the London Borough of Wandsworth’s case, Vauxhall, Nine Elms and Battersea is critical to delivering its housing target. The scheme was also assessed as having a major beneficial long term effect on the labour market and productivity within the Vauxhall, Nine Elms and Battersea Opportunity Area.

More jobs will be accessible within a given travel time for existing residents of the local area, which can in turn mean they move to more productive jobs. Shorter travel times increases the density of employment in an area which is also associated with higher productivity. There will also be benefits for local unemployed or economically inactive residents.

As part of the TWA Order Application, robust EIA has been undertaken to asses economic, social and environmental elements of the works and enable the designer and contractor to incorporate appropriate mitigation measures to the design and work methodology.

A Sustainable Innovation workshop was held with the client, design team and contractor during the detailed design phase of the project to review the Sustainability Appraisal that was undertaken and enable the team to incorporate recommendations into the design. Changes to reference design to improve its sustainability performance included rearranging ticket halls to maximise natural light and reduction in the thickness of tunnel segments to improve resource efficiency. This was in alignment to the Resource Efficiency Strategy produced at an early stage of the project.

Project Management

A specific environmental requirements document was produced by London Underground to outline their commitment to ensuring that the Northern Line Extension is built in accordance with all relevant and current environmental legislation and best practice.

This document was a contractual document that the design team, contractor and any sub-contractors were required to work to and clearly set the project team environmental objectives to work towards. A collaborative working style on the project allowed environmental risks and opportunities to be captured and managed appropriately via monthly environmental meetings with the client, design team and contractor.

In addition, Environmental Design Statements were produced for each package of works for the project provides assurance that the design complies with the Northern Line Extension environmental commitments.

The project team were keen to share the innovative thinking that went into the optimised tunnel design via a series of workshops on the project and did so by producing an article for the Tunnelling Journal. The article discussed the significant improvements in safety and carbon savings achieved by the optimised design. This was achieved by detailed geological assessments and structural modelling of the tunnels to reduce the thickness of the tunnel lining required.

In addition, the project team worked to substantially reduce the storage and pumping provisions for drainage on the scheme. Instead of requiring the construction of sumps for storage of effluent in the confined space of a cross-passage, the configuration of these was redesigned to reduce the volume of excavation required.

People and Communities

The project won a Green Apple Award Environmental Best Practice Award for the use of an innovative sigicom environmental monitoring system. This included a combined noise, vibration and air quality system to help manage and minimise impacts to the local community.

In addition, extensive consultation was undertaken with the Environment Agency to agree a Waste Transfer Station Permit allowing waste to be delivered to the Battersea construction site and removed via barge. This avoided thousands of HGV movements from the roads reducing impact on the local community.

This was the first time an active construction site has also been granted a waste transfer station permit.

Land Use and Landscape

A flood risks assessment was undertaken for the project and resulted in the following incorporations into the design to mitigate and improve the flood risk associated with the development:

  • The design of all sites are in line with the London Plan target of 50% of predevelopment runoff. At Nine Elms, this has been achieved through restricted outfall and attention storage systems.
  • The Kennington park headhouse location has been designed to attenuate 100% of the flow from approximately 80m2 of the catchment area for a 1 in 10-year storm event. A green roof has also been implemented within the design to provide some attenuation and treatment of surface water prior to entering the surface water drainage network.
  • Water tight hatches were incorporated within the design to ensure no surface water enters the shaft.
  • Hydrobrakes installed to limit discharge rates.

The Historic Environment

All three London boroughs (Wandsworth, Lambeth, and Southwark), The Mayor of London and The Greater London Authority, English Heritage, and The Garden History Society were consulted with prior to the planning application submission.

The project enabled the retention of historical assets using mechanisms such as Historic Environmental Assessments, Archaeology and Heritage Management Plans and Instrumentation and Monitoring Method Statements. Archaeological Watching Briefs were also used at all sites and it details the strategy should a discovery be made.

Museum of London Archaeology were appointed to oversee the archaeological works required on the project.

Ecology and Biodiversity

During construction the contractor was in communication with a number of nature conservation bodies including BeeUrban, Friends of Kennington Park, Trees for Cities and the Peregrine Falcon handler through Battersea Development Corp. They had a number of presentations from BeeUrban and Trees for Cities to the project team and have also held volunteering opportunities that included planting bee friendly trees around Kennington Park.

The Contractor also helped fund an innovative study assigning a monetary valuation to the benefits the existing trees in Kennington Park provided. Carpenters from the construction team made bird boxes that were donated to a local horticultural charity based in Battersea Park and pollinator  friendly species were included in the landscape designs.

The workforce were briefed on the importance of the protection of the peregrine falcons including what actions to take if a juvenile/ fledgling were to be encountered on site. Further awareness was raised via filming the movement of the falcons and posters on site.

The Water Environment

The project will result in a beneficial effect by reducing surface water runoff and therefore improving surface water quality due to a reduced risk of spillages in the River Thames from combined sewer overflows.

Physical Resources – Use and Management (Energy, Water, Materials, Waste)

A carbon assessment was undertaken for the scheme and identified decisions incorporated into the design of the project that have led to avoided carbon emissions compared to if no action was taken. These design changes have led to savings of approximately 14,025 tCO2e during the construction phase of the project and include some of the following:

  • Launch tunnels reduced from 110m to 77m and transfer chamber removed from design;
  • Bored tunnel lining reduced in thickness by 30mm along 4.9km 2,655m3 saving in concrete;
  • Removal of earthworks by barge rather than road.

Precast concrete elements were stipulated where possible, which reduced the amount of concrete waste produced on site and reduced the build time. Where diesel generators were required due to the inability to connect into the mains hybrid battery packs were connected to them. This includes the UK’s largest hybrid unit that was utilised for the works at Kennington Station to construct new passenger tunnels between the existing platforms.

These hybrid battery packs provided emission free power once charged by the diesel generator. Used cooking oil from the site canteen was collected by a specialists company that turn it into biofuel to power vehicles. Food waste collections were also arranged, which were taken to a local facility that turned it into fertiliser and energy.

The Supply Chain were also challenged to reduce packaging waste. Reusable containers were encouraged where feasible.


The primary aim of the NLE is to encourage economic growth in London and the wider UK economy by facilitating the sustainable regeneration and development of the VNEB OA.

The whole scheme will provide a new transport connection, two new stations on the Northern Line, efficient transport mode in an area which is in part characterised by poor access to public transport, thereby benefiting both new and existing residential and business communities.

The use of barge to remove construction material from site had a positive effect on the local transport network. To reduce travel undertaken by the project team, a project office has been set up at Camelford House in London where all associated parties could base themselves to further reduce travel for meetings.

The project team used Skype meetings to save travel every day on the project, both with the Client and internally. However, the best example of minimising travel associated with the design team was the interface with the Global Design Centre Chennai team. The GDC have completed all of the RIBA 4 design for MEP for both stations and shafts. There was a formal weekly Skype meeting with the GDC.

This has meant that UK staff have had to travel to the GDC less frequently than would otherwise have been necessary – with less than 50% in country supervision / interfacing necessary as a result. This would not have been possible without Skype – and even more importantly the project’s usage of a BS1192 compliant Projectwise Common Data Environment (CDE), hosted by MM – accessible by the whole FLO supply chain (e.g. including TPN in Croydon and Chennai GDC). The CDE fully supports the UK Governments Level 2 BIM requirements.

Ensuring accessibility for non-motorised users was key for the project team and the following measures were incorporated into the design:
– Provision of induction loops
– Step free access to platforms
– Public wheelchair accessible WC and baby change at ticket hall level
– All offices and station staff areas designed to be accessible for wheelchairs.

Further information

Important benefits delivered by the use of CEEQUAL

Reduced material purchases due to reduction in tonnage of materials in some design aspects. This also resulted in reduced plant use on site, saving fuel use and potentially spend.

What were the main challenges for the project and how were these overcome?

The main challenge during the early stages of the project was gaining support and interest in the sustainability and environmental constraints from the wider project team.
To counteract this, the environment team organised workshops to train and educate the wider team. Sustainability Champions were identified within the engineering teams in order to keep the sustainability and environmental agenda as a high priority. The team also allocated engineers certain credits that they were responsible for and this ensured that all requirements were being met.

What were the drivers and perceived benefits for undertaking a CEEQUAL assessment on this project?

TfL is committed to delivering transport infrastructure and services in a sustainable way as dictated by the Mayor of London in his Transport and Environmental Strategies
for the city.

TfL is using the CEEQUAL framework to drive sustainable design and construction in its large capital projects.

On the NLE scheme, sustainable design was in key focus to
meet planning requirements, encourage improved practices with our contractors to overall deliver better quality of life and value for money.
The tool helped establishing sustainability as a key objective to deliver the civil engineering elements of the project, encouraging local community engagement, improving on relations with affected stakeholders, selecting energy efficient machinery, setting up a waste transfer station to ensure efficient material reuse, considering other transport users, educating staff about sustainable construction methods.

Since it is initiated from the client organisation, CEEQUAL provides a clear focus to all aspects of sustainability and provides an overall, externally recognised sustainability rating for the works as a whole.

CEEQUAL helped to think above and beyond the legal requirements and demonstrate that TfL is a responsible organisation conserving the environment, considering local neighbours, providing new, sustainable transport services for the next generations to come.

How did the use of CEEQUAL influence the outcomes of the project? What was done differently because of the CEEQUAL process?

The project being assessed through the CEEQUAL criteria led to innovative workshops that promoted sustainable design. This led the exploration of opportunities such as energy harvesting and PV technologies. The project also investigated what measures could be employed to reduce the energy consumption of the tunnel boring machines.

The tunnel boring machines are the single biggest electricity/ energy user during construction of the project and this investigation has led to a saving of approximately 22%.

What elements of this project highlight best practice and innovation?

CEEQUAL/BREAM workshops and innovative design led to avoided emissions such as those listed below:
– Launch tunnels reduced from 110m to 77m and transfer chamber being
removed saved ~270 tCO2e
– Bored tunnel lining reduced in thickness by 30mm along 4.9km led to
2,655m3 saving in concrete and ~5,880 tCO2e saving
– Reduced diameter of piles in shafts from 900mm to 750mm leading to a
saving of ~630 tCO2e.

It was possible to quantify the approximate carbon emissions reduction, which will show a net reduction of around 16% to overall carbon emissions of the Project. Some of these reductions have come directly from the requirements of the CEEQUAL process.

The project won a Green Apple Award Environmental Best Practice Award for the use of an innovative sigicom environmental monitoring system. This included a combined noise, vibration and air quality system to help manage and minimise impacts to the local community.

“Using CEEQUAL as a framework on the project has helped foster collaboration
between Client, Designer and Contractor to identify and target measures that could
bring environmental benefits. It has helped to give focus and also track performance.”

– Matt Brinklow, FLO Project Environmental Lead

Award Presentation

Northern Line Extension Award Presentation

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