22 Jan 2026
Plans for the proposed Mid Hill wind farm in the Scottish Borders have suffered a major setback after the Ministry of Defence (MoD) lodged a formal objection warning that the project poses an “unmanageable” risk to the UK’s nuclear test monitoring capabilities and to military air operations.
The application by developer Invenergy, the US’s largest private renewable energy company, was submitted to the Scottish Government’s Energy Consents Unit (ECU), and seeks approval for 13 turbines up to 200 metres tall plus an energy storage facility southwest of Hawick. The site lies within the safeguarding zone for the Eskdalemuir seismic monitoring array – the UK’s only facility to detect nuclear tests carried out anywhere in the world.
In its objection, the MoD warned that the development would have severe implications for the Eskdalemuir station, stating that Mid Hill would have “an unmanageable impact on the operation and capability of the Eskdalemuir Seismological recording station”.
The department added that the seismic array forms part of a global network whose effectiveness depends on maintaining an environment with minimal interference. Current planning controls include a 10 km exclusion zone and 50 km safeguarding zone for wind turbines.
The MoD additionally highlighted the negative impact on national defence aviation systems, citing “detrimental effects on the performance of radar systems used to manage air traffic”, as well as military training and Air Traffic Control tasks.
The MoD stated that modern wind turbines generate seismic noise which interferes with the ultra-sensitive seismic sensors at Eskdalemuir. Research has shown that the cumulative effect of turbines within a 50 km radius must be strictly limited to ensure the UK can meet its obligations under the Comprehensive Nuclear Test Ban Treaty. As a result, the MoD manages a finite “seismic noise budget” within that 50 km safeguarding zone.
According to its objection, “there is no seismic noise capacity available” – meaning additional turbines would push the cumulative vibration levels beyond acceptable limits and compromise the station’s international monitoring role.
The proposed turbines fall within a tactical training and low flying area where fixed-wing aircraft routinely operate at extremely low levels.
According to the objection: “The development falls within Tactical Training Area 20T… within which fixed wing aircraft may operate as low as 100 feet (30.5 metres) above ground level… The addition of turbines in this location has the potential to introduce a physical obstruction to low flying aircraft operating in the area.”
The MoD further noted that turbines over 150m must meet aviation safety lighting requirements, and confirmed it would require accredited MoD lighting specifications were the scheme ever to be approved.
Local residents argue the Borders is already overwhelmed by wind energy infrastructure.
Sarah St Pierre of the Borthwickwater Landscape Conservation Group said: “This region has been inundated with large-scale wind farm plans. Now we are being asked to sacrifice not only our landscape but a critical part of the international security network that monitors nuclear activity. The Borders has done more than its fair share.
“What the MoD has now confirmed is that there is no remaining seismic capacity for further turbines and that Mid Hill would undermine both nuclear monitoring and defence aviation. At some point we have to say enough is enough – this is not a suitable location and these impacts are not trivial.”
The objection is expected to become a central issue in the planning process, given the rarity and strategic importance of the Eskdalemuir station and the difficulty of mitigating seismic and aviation interference from wind turbines in the safeguarding zone.