Westminster City Council King Street Low Carbon Trial

PPM KING STREET WORKS METHOD

The low carbon method for relaying the footway is to:

1. Take up and relay the kerb line, using a 1.5t electric excavator

2. Take up the existing paving materials with the excavator

3. Excavate the sub-base to the required level using the excavator

4. Level the sub-base by hand

5. Install the sub-base concrete, use electric wacker plate to level

6. Prepare paving area by hand

7. Lay grout paving bed by mason

8. Prime and then lay the paving slabs, with any cuts carried out with an electric disc cutting saw (masonry work)

9. Fill the joints using Marshalls’ Pavepoint

10. Reinstate the kerb line with Greenpatch, a hand-laid asphalt

POWER SUPPLY

Power supply was one of the greatest challenges to the trial as it was impractical to take the electric excavator and electric plant off-site to be charged, so a solution to charging on site had to be found. A 32 amp supply from existing street furniture such as lighting columns is currently not available and the power pack required a 63 amp three-phase supply, so a feeder pillar with a three-phase 100 amp metered supply was installed. Our ambition was to utilise a JCB power cube, which could have delivered 15kVA of power output through lithium-ion batteries. This could have been charged by an on-site feeder pillar or taken away to a depot to charge, which would have made charging of all site equipment very easy. However, JCB are still waiting for full approval to supply them. The lead time to obtain the feeder pillars was quite substantial (partly due to COVID-19) and the installation was required at least one week prior to the commencement of construction to allow for any installation delays or COVID-19 related issues. As the job could not commence without the feeder pillars and power supply, it was crucial that this phase was complete in time to plan the logistical set up. The power was required to charge the power pack and the welfare unit, and as a legacy to the project it needed to convert into two EV charging points to be used when the works were complete. Unfortunately, when we were informed that the power pack was not available, the feeder pillar needed to be adapted to allow direct power charging of the electrical equipment. In addition, we learnt that the plant had different connections that needed to be accommodated, which would have worked better if the power pack had been available for use. This was installed the week preceding the scheme going to site and connected to the power with a primary UK Power Network (UKPN) connection. The full specification is shown in Figure 7 and Figure 8.

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