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King Street - Driving Down Carbon

Description of Works

FM Conway has worked with Westminster City Council to deliver a low-carbon street-works pilot that could transform the way public realm projects are designed and delivered in support of the climate emergency agenda.

Services used on this project Major Projects Aggregates & Asphalt Surfacing
Delivering Innovation

King Street, in Westminster, underwent a repair and replacement of the footpath and kerbs, which extends from St James’s Square to its junction with St James’s Street and features an existing footway constructed of artificial stone paving, with areas of granite setts and block paving.

As part of a six-week maintenance project to rejuvenate the area and minimise carbon footprint, the scheme used low-carbon electric plant, tools, welfare and recycled materials, the removal of diesel and petrol equipment, and the reduced consumption of natural resources. Furthermore, travel to and from site was reduced with carbon-friendly forms of travel used, and all plant brought to site used electric vehicles or vehicles powered with HVO fuel where electric was not possible.

Using the Metis carbon calculator and a second site, Marlborough Hill, the project was able to assess the full life cycle impacts for comparison, to target the extent and scale that the scheme has reduced embodied carbon.

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Challenges and Solutions

One of the biggest challenges of the project, was utilising equipment and materials that reflected the low carbon nature of the trial, therefore, alternatives needed to be found.

For the kerb line reinstatement, the teams used GreenPatch, a product manufactured with recycled asphalt and no petroleum-based ‘cut back’ solvents. This was used instead of Hot Rolled Asphalt (HRA) in order to provide a more environmentally friendly solution. Low carbon C10 concrete was then used for the footway and C40 concrete was used for the kerbing.

By reducing the slab thickness used from 63mm to 50mm, this also allowed for more efficient vehicle deliveries, ultimately reducing carbon, including a saving in embodied carbon and a reduction in waste removal and reduction of packaging.

The site welfare was powered by electric from renewable sources and on-site renewable energy to save on conventional diesel welfare cabins over the duration of the project. Plus, the electric powered plant and small vehicles gave savings in red diesel consumption and petrol, whilst also offering a quieter electric alternative to reduce noise pollution in Westminster.

A further saving was achieved by using HVO in FM Conway diesel HGV’s to make carbon savings where the technology is not available to change to an electric or zero carbon alternative.

A number of electric tools and plant were also used, including an electric excavator, an electric forklift, wacker and saw, as well as the use of an electric car service. An electric vehicle charge point was also installed in order to charge the electric plant and was left in place in order to encourage local residents to switch to electric vehicles.



The project was successfully delivered, achieving:

  • Operational savings of over 4t of carbon
  • Embodied savings of 23t of carbon
  • An overall saving of 27t of carbon compared to the Marlborough Hill scheme
  • Operational savings per day of 79%
  • Embodied carbon savings of 46% per m2

These savings are an important accumulating factor considering several hundred of these projects are carried out throughout Westminster annually. If the same specification and works method were employed on the annual programme of 25 footway schemes, potentially nearly 700t of carbon could be eliminated.

Following this successful trial, King Street aims to be a catalyst that will transform the industry and transition us into a new carbon-friendly delivery model, ensuring that we have the blueprint for providing London with a greener future.