The Route


The preferred mitigation option which is being developed involves the replacement of the existing section of overhead line with underground cabling. After carrying out engineering and environmental studies to investigate various options for crossing the Dwyryd Estuary our team has concluded that a deep underground tunnel is the best option.

Local stakeholders and the community welcomed this option during public events in summer 2016 and the project will now include the removal of 3km of overhead line and ten pylons between the existing Garth sealing end compound in the west and Cilfor in the east.

At the eastern end of the underground route corridor, there will need to be a sealing end compound. These are needed where a section of underground cable connects to an overhead line. A tunnel head house would also be required at each end of a cable tunnel.

Our aim is to carefully select their locations to reduce the visual impact of this electricity infrastructure and again, we are working with our group of technical stakeholders to identify the best locations.

We are also considering the potential impact on this section of line arising from proposed new generation in the area including a new nuclear power station that is proposed to be built on Anglesey by 2024. The new power station will require the construction of a new transmission line across Anglesey, and uprating of the circuits between Pentir and Trawsfynydd. These circuits include the section of line being considered for undergrounding as part of the Visual Impact Provision project. Studies are ongoing to identify what work will be required to accommodate the proposed new generation.

At present, we are proposing to continue with the pre-construction, environmental survey and planning works for the undergrounding project, but to align construction activities with the nuclear connection project to ensure an efficient and economic solution and to minimise impacts on the local community and the environment.

If you would like more information about this, please email

Please click on the link below to see a map of the existing transmission line and our current search areas for the tunnel route and the possible locations for the tunnel head houses and sealing end compound.

Download map here