Current construction activity

Date from

Date to


February 2022

Late 2025

Seabank substation and nearby pylons at Crooks Marsh

June 2021

Late 2024

Access to public footpaths and rights of way

May 2021


Building new pylons



Roadworks and traffic management

Overview – Summer 2022

In July 2022, we started work on building 27 new lattice pylons in the northern section of the Hinkley Connection from Sandford to Seabank, near Avonmouth.

National Grid is using lattice pylons in and around Avonmouth, rather than the T-pylon design seen elsewhere on the Hinkley Connection route because at 50 metres high, the lattice design provides the height required across the River Avon, and means National Grid can navigate the tighter turning angles that are needed on the route between the River Avon and Seabank substation.

Our contractor, Balfour Beatty, erected the first lattice pylon next to the M49 on Tuesday 19 July 2022. Most pylons take up to four weeks to assemble with those near the River Avon taking approximately six weeks.

We expect all pylons to constructed and the wires in place by 2023. During the work to install the wires between the pylons, we’ll use controlled lifting systems and erect scaffolding where the wires cross over roads.

Our contractor, J Murphy and Sons, started work in February 2022 to modify the existing electricity, replacing nearby pylons at Crooks Marsh with new underground cables and make changes within Seabank substation. This work is set to be completed in late 2023.

To make way for the new 400,000 volt connection, National Grid is removing 67 kilometres of existing 132,000 volt overhead wires and 249 along the new connection route.

In 2021, we removed seven pylons from across the M49. During 2023, we we’ll take down another line of pylons between Portishead and Avonmouth substations, removing pylons from a residential area, including those near Avonmouth C of E Primary School and Daisy’s Nursery.

Thank you from everyone working on the project for your patience as we continue our work to deliver electricity safely, efficiently, and reliably, and support the UK’s ambition to achieve net zero by 2050.

Contact our community relations team to register for project updates direct to your inbox.

Take a look at our detailed map

Avonmouth timeline

Completed September 2020


Modify Avonmouth substation and existing overhead line to the east of the substation

Work carried out by Western Power Distribution (WPD):

  • Replaced a small section of overhead line to the north of the substation with underground cables.

  • Constructed a new cable sealing end (CSE) pylon to connect the underground cables to the overhead line.

  • Changes inside Avonmouth substation to enable the connection of the new underground cables.

  • Reinstatement work including removal of the temporary construction compound and part of the haul road.

To be confirmed


Modify Seabank 132,000 volt substation and the existing overhead lines at Seabank

What we're doing:

  • Building a temporary construction compound and temporary entrances and access roads to allow construction traffic to enter the undergrounding site from the local highway.

  • Undergrounding a small section of the three existing overhead lines at Seabank. This will enable the new overhead line to pass safely overhead.

  • Building three pylons to connect the existing overhead lines to underground cables.

  • Modifying Seabank substation to enable the connection of the new underground cables.

  • Removing the existing overhead lines that are no longer needed in this area.

This work will be done by Western Power Distribution.

Mid 2021 to mid 2025


Build new 400,000 volt overhead line

What we're doing:

  • Building temporary entrances and access roads to allow construction traffic to enter site from the local highway.

  • Building a new overhead line from Sandford substation to Seabank substation (approximately 31.2 km).

  • In this area, we'll use a mix of steel lattice pylons and T-pylons.

Mid 2021 to mid 2025


Remove the existing 132,000 volt overhead line

What we're doing:

  • Removing Western Power Distribution’s overhead line from the A368 in Sandford to Avonmouth substation, which will make way for, and minimise the visual impact of, the new connection.

  • Removing a small section of the existing overhead line to the east of Avonmouth substation.

To be confirmed


Modify Seabank 400,000 volt substation

What we're doing:

  • Extending the existing substation to enable the connection of the new overhead line.

  • Modifying the existing site access road.

  • Removing unnecessary electrical equipment.

  • Installing a perimeter flood defence wall with flood gates around the substation to help guard against tidal flood risk.