The Visual Impact Provision project in Eryri National Park aims to reduce the visual impact of National Grid’s overhead line across the Dwyryd Estuary from Minffordd to Llandecwyn.

About the project

The Visual Impact Provision project in Eryri National Park aims to reduce the visual impact of National Grid’s overhead line across the Dwyryd Estuary from Minffordd to Llandecwyn.

Stakeholders have agreed that the best way to achieve this is to remove a section of this overhead line and replace it with electricity cables buried in a tunnel underground. It represents a major opportunity to conserve and enhance the natural beauty, wildlife and environmental heritage of this precious landscape of Eryri.

The section of overhead line

The section of overhead line to be removed runs from the Garth Sealing End Compound (SEC) near Minffordd and crosses the Dwyryd Estuary in Penrhyndeudraeth, where it enters the western edge of the National Park. It then continues eastwards up to just beyond Llandecwyn.

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

Project area overview map

The section of overhead line, constructed in 1966, is part of the 400kV electricity route connecting the 400kV Pentir substation near Bangor with the former Trawsfynydd Power Station, now a 400kV substation.

There is an existing section of underground cables across the Glaslyn estuary to the west of the section included in the VIP project.

Currently the pylons operate with one circuit at 400kV on one side of the pylon, while the circuit on the other side operates at 132kV as part of the distribution network operators (DNO) system.

The DNO in this area is Scottish Power Energy Networks, who we’ll be working with throughout the project.

The 4ZC route is an integral part of the National Electricity infrastructure and this project has been designed to meet the capability of the existing infrastructure which will help to provide secure and reliable power supplies to North Wales and beyond.


Why was this section selected?

This section of line was identified by an independent landscape study as having landscape impacts of very high importance, particularly on the Ardudwy Coastal Hinterland as well as a small part of the Morfa Harlech landscape. This is a complex and dramatic landscape which provides a transition between the popular tourist coastline of the National Park and the adjacent upland areas.

The special qualities of the National Park are clearly expressed in the landscape, which also displays high scenic quality, conservation interests and recreational value.

The existing overhead line conflicts with the character of the landscape, forming a highly-visible intrusive feature which has a significant impact on the landscape surrounding it.

Removal of the overhead line will enhance the special landscape properties in the area and improve the setting of the Aberglaslyn registered Welsh Historic Landscape. Views and the setting of the registered park and garden at Portmeirion as well as a number of listed buildings will also benefit. Views will also be enhanced from local roads, trails, footpaths and the coastal railway when the pylons are removed.


Our work in Eryri so far

Since 2015, we have held a series of technical workshops for stakeholders, and public ‘drop-in’ events in the National Park. The stakeholder workshops included representatives from the National Park Authority, Cyngor Gwynedd, Natural Resources Wales, Cadw and National Trust.

Burying the cables underground was the preferred option with stakeholders and members of the public that attended the events. It was felt that screening or camouflaging pylons or adopting an alternative design would not have sufficient impact. We then continued to work with local technical stakeholders to identify and develop possible route corridor options for this work, which included talking to key stakeholders and landowners to identify any environmental, archaeological and land issues that would influence where an underground route could be built.

In November and December 2018, we held public consultation events over three days in Penrhyndeudraeth and Talsarnau. Stakeholders and members of the public were invited to these events to find out more detail about the project, speak to members of our team and to submit formal feedback on our plans.

We held further engagement events at the end of 2019 and taking all the feedback from stakeholders and local people into account, on 6 March 2020 we submitted the planning application to the Eryri National Park Authority and Cyngor Gwynedd.

The proposal also included the construction of two new tunnel head houses, which will give access to the tunnel, along with a sealing end compound at the eastern end, which will connect the cables to the overhead line that will remain.

In July 2020, we received planning permission subject to the discharge of a number of conditions from both the National Park Authority and Cyngor Gwynedd. Both planning committees were unanimous in their approval of the project.

In January 2022 we announced that we had appointed Hochtief UK as our main contractor to carry out the work following a tendering process.

Since then, we have been continuing with design development and in our negotiations with landowners.

2022 saw the start of work in the area with more surveys in the spring and the start of site establishment later in the year. Construction is due to start fully later in 2023 with the pylons and overhead line due for removal in 2029.