Former landfill site set to play its part in transmitting low carbon energy
Three double-circuit 132kV overhead electricity lines that previously connected into Seabank substation – the most northerly point on the Hinkley Connection route - have been successfully removed and replaced with underground cables at Crooks Marsh to make way for the new 57km, 400kV line between Shurton and Seabank.
The six electricity distribution pylons that carried the lines have also been replaced by three cable sealing end (CSE) pylons – the type of pylon required to join the existing overhead lines into the newly installed cables. With reinstatement works currently underway, these works have left the landscape at Crooks Marsh unrecognisable from its status as a former landfill site.
A challenging terrain
The journey to this point has not been easy. The presence of contaminated land meant that National Grid’s contractor, J Murphy & Sons had to import 105,000 tonnes of stone to build up the land and encase the cables safely. Depths of the stone on site measures up to five metres at some locations. This extensive groundwork, which began in the summer of 2022, was essential to prevent disturbing the contaminants below.
One of the significant challenges faced during this process was the need to account for land settlement in the design. This was addressed by introducing expansion troughs that provide slack to the cable system, reducing the need for piling on the project. Consequently, only the CSE pylons and the expansion troughs sections required piling.
Harriet Dal Din, Project Manager for National Grid said, “The success of this phase is a testament to the collaborative efforts of our dedicated team. The project, delivered by an exceptional team from J Murphy & Sons required close coordination with multiple stakeholders, including NGED for managing outages, Woods for OHL re-conducting to the new CSE towers, and Balfour Beatty, who are installing the new 400kV pylons in the vicinity. We extend a thank you to everyone involved for their hard work and commitment.”
Works at Crooks Marsh is now heavily in the reinstatement stage, the site offices and some of the temporary access roads have been removed and teams are placing topsoil over all the stone that was imported to encase the new cables. Work on site is planned to complete in early December 2024.
