Installing underground cables through the Mendips AONB

We started work in April 2019 to prepare to install 8.5 kilometres of underground cables across the Mendip Hills Area of Outstanding Natural Beauty (AONB). This work is being carried out because of feedback received during consultation.

The cables run from a new cable sealing end compound we’re building at Loxton, south of the Mendip Hills AONB, to the new Sandford substation.

In summer 2020 we completed our working area and temporary haul road to allow vehicles to move safely along the cable route, and to keep as much of our construction traffic away from local roads as we can. The working area along the cable route is about 60m wide.

To lay the cables we dig four cable trenches approximately 2m wide, 1.8m deep and a few metres apart. We carefully remove and store the soil while we complete our work. We then install ducts and pull the cables through the ducts in lengths of approximately 650m-1,000m. In sensitive areas, such as road crossings and waterways, we use horizontal directional drilling (HDD) to push the ducts through the ground.

Once the cables are laid, we join the cable sections together in a process known as ‘jointing’ and cover the cables with cement-bound sand and a protective cover. Finally, we carefully fill the trenches with the stored soil from excavation and reinstate the land.

By the end of October cable installation was 74 per cent complete, and 58 per cent of the cable sections were jointed together. We expect to complete our work by 2024.