What's happening now?
National Grid is carrying out work at Penrhos to construct a new Gas Insulated Substation on the former substation site, alongside the replacement of approximately three kilometres of existing underground electricity cable that previously connected into the site. This work is needed to keep the electricity network safe and reliable, and to enable new customers to connect to the electricity transmission system.
Early works have included surveys, ground investigations and site preparation. The main construction phase is due to start in summer 2026. Work will take place on the substation site and along the existing cable route.
The substation site is to the south-east of the former Anglesey Aluminium site. The cable route starts at the substation and runs broadly alongside the A5, towards Valley and just beyond Gorad Road. Along this route, we will remove and replace sections of the existing cables with new infrastructure. To do this, we will need temporary access points, known as bellmouths, as well as the use of temporary tracks and compounds to support construction.
Latest updates
Gorad Road and A5 east of Causeway - bellmouth installation
Bellmouth works have been temporarily paused while environmental investigations are carried out, following new information indicating the potential presence of protected species in a pond adjacent to the works. We are working with Natural Resources Wales (NRW) to agree appropriate mitigation, with investigations expected to take a minimum of eight weeks.
Stanley Embankment - cable removal
Between Monday 18th May and Friday 20th November 2026, there will be temporary two‑way traffic lights along the Stanley Embankment. This is so our workforce can remove existing cables from the concrete troughs along the embankment, allowing new cabling to be installed at a later date.
The works will be carried out in four stages, each around 250 metres long. Once work is completed in one section, the traffic management will move on to the next. A temporary 20mph speed limit will also be in place for the duration of the works.
How will these works affect me?
You may notice more activity in the area while we carry out construction, including construction vehicles, workers on site and temporary changes to traffic arrangements.
To keep people safe, we will need temporary traffic management at some points during construction. This may include traffic lights, lane closures and, in some locations, road closure. These measures will be introduced in stages across locations and will be designed to minimise disruption as much as reasonably possible.
We will continue to provide advance notice of key activities and keep you informed as work progresses, so you can plan ahead. Our project team will also be available to answer any questions.
Contact the team
If you have a question, you can contact us in the following ways:
Email us: [email protected]
Call us: 0808 303 0570