Summer update: Pentir to Trawsfynydd network reinforcement

We’re writing to provide you with an update on our work to upgrade the electricity transmission network in west Gwynedd in the coming years.
 
Earlier this year we appointed our main contractor Murphy Power Networks to design and deliver the underground cable section of our work, between Wern to the west of Porthmadog and Garth to the east.
 
Having carried out various walkover surveys in the last few months, we now need to undertake more detailed ground investigation (GI) survey work involving test boreholes to better understand the exact ground conditions. 
 
These GI surveys will allow us to carefully consider the routing and design of our cables, so that any potential impacts and mitigation measures can be considered at an early stage.
 
As part of GI, we also hope to carry out field walkover surveys soon, which will include soil assessments using a hand auger, a handheld tool used to take soil samples. National Grid’s appointed land agents, Fisher German, will be in contact with individual landowners to arrange these surveys on their land.
 
Separate to this, we are also contacting all landowners along the route between Wern and Garth to share a red line boundary – which is the likely maximum area within which we expect our work needs to take place. It’s important to make clear that the boundary does not mean we need all of the area within it.
 
Within the area is a proposed underground cable route corridor, which has been informed by known features and constraints within the area, as well as gathered local information and surveys to date. The information we gather will help us to identify and consider options for potential routes for our new underground cables to replace the existing cables and increase capacity.
 
This proposed cable route corridor indicates the areas which may be required for installing new cables, decommissioning the existing cables, and associated activities such as access routes and temporary work areas. We are not proposing installing cables in all areas, and the corridor will be further refined and narrowed as the project design develops and our on-the-ground studies continue.
 
Once we’ve gathered feedback and carried out further surveys to inform the design, we will identify the land and rights that will be required for the installation, operation and long term maintenance of the cables. We will then contact affected landowners again with proposed plans and details to discuss this with them. 
 
At the same time, we have been in close discussion with key stakeholders, including Welsh Government and Traffig Cymru/Traffic Wales North and Mid Wales Trunk Road Agent (NMWTRA), Ffestiniog & Welsh Highland Railways and Welsh Highland Heritage Railway, on potential crossing points. Further to this, we have been in close discussions with representatives from Natural Resources Wales (NRW) to ensure they are also kept informed as our route refinement progresses.
 
In addition to the work for the replacement underground cables, we have also been carrying out non-intrusive survey work along the rest of the route between our substations at Pentir and Trawsfynydd, where the existing overhead cables need to be replaced. We’re continuing to liaise with those who have our overhead line running over their land about this work.
 
This careful environmental and design work on both the buried cables and overhead line will be followed by consenting and regulatory activities. It will also include engagement and consultation with key stakeholders and with the public.
 
Based on our current timeline, we expect construction work will then start in mid to late 2025.
 
As before, this work is separate from our ongoing Visual Impact Provision (VIP) Project, which is removing a section of overhead line in a visually sensitive part of Eryri National Park and replacing it with electricity cables buried in a tunnel. It is also separate from our work to replace underground cables between Dinorwig Power Station and our Pentir substation. We are working closely with our colleagues on both these projects to ensure our work is coordinated and efficient.
 
You can find more information at https://www.nationalgrid.com/electricity-transmission/network-and-infrastructure/pentir-thrawsfynydd. We’ll continue to update this web page as our work progresses.
 
If you would like to know any more about our work at this stage, please do contact us at nationalgrid@pentir-traws.co.uk or call on 0800 915 2485.
 
We’ll make sure we continue to keep you up to date as our work progresses.
 
Yours faithfully
 
Tom Hurford
 
Project Manager