Westminster City Council King Street Low Carbon Trial

KING STREET DEVIATIONS FROM METHOD - OPERATIONS

For the King Street trial most of the operations took place as per the standard methodology. However, no diesel vehicles or plant were permitted on site.

Staff, operatives and visitors were required to attend site by a sustainable mode of transport and materials were delivered to site by an electric vehicle or cargo bike where possible.

At present there are very little or no options for sustainable larger vehicles such as grab lorries. For internal deliveries where these vehicles were used, diesel fuel was replaced by Hydrotreated Vegetable Oils (HVO). HVO is a renewable diesel alternative and is one of the world’s cleanest fuels on the market. It eliminates up to 90% of net greenhouse gas emissions such as CO2 and hugely reduces nitrogen oxide (NOx), particulate matter (PM) and carbon monoxide (CO) emissions. For the paving and grouting delivery from Marshalls, a single delivery was made to a central hub as the supplier could not commit to converting to HVO for a single journey. The final mile delivery to site came via a grab lorry on a ‘just-in-time’ basis.

The following plant was used instead of the usual specification:

• Electric Welfare Unit

• Electric 1.5t Excavator

• Electric Wacker Plate

• Electric Disc Cutting Saw

KING STREET DEVIATIONS FROM METHOD - SPECIFICATION

The scheme had already been designed using ASP as standard paving, therefore, to avoid a complete redesign and maintain the look and feel of the street, it was decided to keep the material the same. The team had a discussion with the paving supplier Marshalls to understand if there were any alternative low carbon slabs on the market. Due to the highly cementitious content within the slabs and the method of production at present there is very limited choice available, and to maintain the current aesthetics there are none. However, the option of reducing the thickness of the paving slab allowed for some carbon reduction as standard ASP slabs used in Westminster are 63mm thick, whereas Marshalls have a standard 50mm paving slab. They estimated that by making this change, 4kg/m2 of carbon could be saved. Further work on the specification by Marshalls showed that the slabs could even have a shallower foundation if the correct grout and pave bed were to be used.

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