New Coire Mashie 400kV Substation and Earba PSH Connection

We would like to provide an update on upcoming ground investigation (GI) and forestry enabling works associated with the proposed Coire Mashie Substation and underground cable connection.

These surveys and enabling activities are an important part of the development process and will help inform the detailed design of the proposed project.

Welfare compounds and mobilisation

As part of the mobilisation process, two temporary welfare compound areas will be established to support the works. Welfare cabins are scheduled to be delivered to the FLS quarry area on 13 and 14 August 2026. A map showing the locations of the welfare compounds has been shared with local stakeholders.

Ground investigation works

Ground investigation works will be undertaken by BAM Nuttall.

Mobilisation is scheduled to begin on 17 August 2026 and will continue for three days. Borehole and trial pit investigations will then commence on 20 August 2026, starting in the Loch Earba area before progressing north-east across the site.

The programme is expected to run for approximately 10 weeks, with demobilisation anticipated on 21 October 2026.

Scope of works

The investigations will include:

• 78 trial pits
• 29 boreholes
• Up to 15 BAM Nuttall personnel on site at any one time

The information gathered will help improve understanding of ground conditions across the proposed development area and support ongoing project design work.

Working hours

Ground investigation works will be carried out on an 11-day fortnight working pattern, operating from Monday through to the following Thursday, between:

07:30 and 17:00

Planned weekend working

To help maintain progress, weekend working is currently planned every second weekend on the following dates:

• Saturday 22 August and Sunday 23 August 2026
• Saturday 5 September and Sunday 6 September 2026
• Saturday 19 September and Sunday 20 September 2026
• Saturday 3 October and Sunday 4 October 2026
• Saturday 17 October and Sunday 18 October 2026

Where weekend working is required, activities will be undertaken away from nearby properties wherever possible to minimise disturbance to residents.

Forestry enabling works

In parallel with the ground investigation programme, RTS Forestry will undertake forestry enabling works to facilitate access to investigation locations within forestry areas.

Mobilisation is scheduled for 17 August 2026, with works commencing on 18 August 2026 and continuing for approximately six weeks, concluding around 21 September 2026.

Scope of works

The forestry works will involve:

• Tree felling within pre-agreed areas
• Mulching of vegetation
• Stump removal
• Creation of temporary access corridors to trial pit and borehole locations

Up to six RTS Forestry personnel are expected to be on site at any one time.

Working hours

Forestry works will take place:

Monday to Friday, 07:00 to 19:00

Access arrangements

Access for both the ground investigation and forestry works will be taken from the A86 via the existing route serving Feagour and Loch Earba.

Properties most directly affected by these activities have been contacted separately with additional information regarding the planned works.

Looking ahead

As the project design has developed, alternative access options for the potential construction phase have also been explored.

Subject to the project receiving planning consent, the current preferred approach for construction of the proposed substation and underground cable connection would utilise an alternative access route. This approach could significantly reduce the amount of construction traffic using sections of the existing access route that will be used during the ground investigation and forestry works.

These proposals remain subject to planning consent and further design development. However, they represent a significant change from earlier concepts, and we are committed to keeping communities informed as project planning progresses.

Ongoing engagement

Maintaining open communication with local communities remains a key priority throughout the works programme.

Development Project Managers Darrell and Emma, who attended previous consultation events, will be undertaking regular site visits throughout the programme, typically on a fortnightly basis.

Should any concerns arise during the works, we will be happy to arrange discussions with the Community Council, local residents or other affected stakeholders where appropriate.

Contact us

If you have any questions about the upcoming works or would like further information about the proposed Coire Mashie Substation and underground cable connection project, please do not hesitate to get in touch with the project team. We will continue to provide updates as the works progress.

We have today published a new economic report setting out the significant economic benefits associated with our planned £29bn investment in new and upgraded electricity transmission infrastructure across the north of Scotland.

The report, titled ‘Re‑energising the North: Transforming Scotland’, provides an update on our previously outlined economic analysis on plans to invest billions in mission-critical grid infrastructure, providing further insight into the scale of economic opportunity associated with the investment programme.

The report reaffirms our programme as one of the largest private infrastructure investments in Scotland’s history, with around £29bn of planned investment across the north of Scotland in the next five years, and it details the extent of the economic opportunity across the region.

Using advanced economic modelling to analyse the impact of clean power infrastructure investment, the report’s findings conclude that our investment: 

• Will support up to 10,000 jobs in the north of Scotland, and 24,000 across Scotland; 
• When added to investment by other transmission operators and investment in generation will add around £60bn to UK economic output - with the Scottish economy up to 3% larger over the long term; 
• Will deliver long-term improvements in productivity, wages and economic resilience, with employees moving into higher-value roles and key sectors expanding permanently; and 
• Will create unique opportunities for Scottish suppliers, businesses and communities across multiple sectors, including forestry, peatland restoration, aggregates and concrete too. 

The findings highlight the importance of ensuring that the benefits of investment are felt locally, with thousands of skilled jobs, increased supply chain activity, and investment flowing into communities across the north of Scotland.

Read the full News and Views article to find out more.

We would like to inform the community that the Screening Letters for both the Coire Mashie Substation and the proposed reconfiguration of the existing Beauly–Denny 400kV overhead line have now been uploaded to the project webpage.

These documents can be found under the “Project Documents” tab and are available for anyone wishing to review the initial stages of the Environmental Impact Assessment (EIA) process.

For convenience, the Screening Letters can also be viewed directly on the following official platforms:

• Scottish Government – Energy Consents Unit (ECU)
  Scottish Government - Energy Consents Unit - Application Details..
• The Highland Council Planning Portal
  26/00761/SCRE | EIA Screening Opinion Request for the proposed Coire Mashie Substation | Land 2KM S…

Screening is the first step in determining whether a full Environmental Impact Assessment is required. We will continue to share updates as further milestones are reached in the development process.

If you have any questions or would like further information, please feel free to get in touch.

Our Report on Consultation for the new Coire Mashie Substation and Loch Earba Pumped Hydro Scheme Connection has now been published.

The report provides a summary of the extensive feedback received during the consultation period, outlines how this feedback has been considered, and confirms that the substation site Option 1 will be taken forward to the next stage of development. While all of the appraised site locations presented a range of environmental and engineering challenges, the challenges associated with Option 1 were considered manageable and capable of being addressed through further design and mitigation work.

The Report on Consultation (RoC) can be downloaded from the Documents tab on our project website. All stakeholders who have registered for project updates will also receive a direct link to the report. New Coire Mashie 400kV Substation and Earba PSH Connection - SSEN Transmission

We would like to thank all stakeholders who took the time to engage with our early consultation process. Your feedback has been invaluable in shaping the proposals to date.

Publication of the RoC marks the completion of the first round of non-statutory consultation, during which we sought views on the proposed route for the 400kV connection, and substation locations. We will continue to engage with stakeholders ahead of further community consultation in the new year, as we work to refine our proposals.

We welcome ongoing dialogue and would like to reassure stakeholders that there will be further opportunities to engage as the project progresses.

We are holding a public consultation for the new proposed Coire Mashie 400kV substation and connection to the consented Earba Pumped Storage Hydro (PSH).

During this consultation, we are presenting our approach to developing the new 400kV substation required near Kinloch Laggan in the Highlands of Scotland for the Earba Pumped Storage Hydro connection.

The consultation event will take place on:

Wednesday 28 May 2025, 3pm - 7pm at Laggan Village Hall, Laggan Bridge by Newtonmore, Inverness-shire, PH20 1AN

Our consultation includes information regarding our site selection process and the potential site options being considered, the planning process, environmental and engineering considerations and maps which aim to give stakeholders and community members a better visual representation of the work on the project to date.

Stakeholder engagement in the development phase is vital in shaping our proposals. To do this effectively, we need to capture consultation feedback and harness local knowledge to identify challenges and explore community benefit and opportunities.

We’re therefore requesting views regarding the site selection process, and any thoughts regarding the potential sites for the new Coire Mashie substation presented.

We invite all interested parties to attend our public drop-in event to discuss our plans with the project team and share your views.