Eskdalemuir Seismic Array – Government Consultation and MOD Response signal progress in the Southern Uplands
Background
On 20 March 2026, the Department for Energy Security and Net Zero ("DESNZ") published a consultation on an updated approach to managing onshore wind turbine interference with the Eskdalemuir Seismic Array (the "Array"), alongside a draft Technical Guidance Document and Analytical Annex https://www.gov.uk/government/consultations/eskdalemuir-seismic-array-revised-approach-to-managing-onshore-wind-turbine-interference . This was quickly followed by the Ministry of Defence ("MOD") publishing its response on 24 March 2026 to its own, earlier consultation on its approach to safeguarding the Array, adopting a new safeguarding approach with effect from 18 March 2026 https://www.gov.uk/government/consultations/consultation-on-the-ministry-of-defences-approach-to-safeguarding-the-eskdalemuir-seismological-array/outcome/mod-response-to-consultation-on-the-ministry-of-defences-approach-to-safeguarding-the-eskdalemuir-seismological-array .
Taken together, these publications represent the most significant development in Eskdalemuir policy in over a decade, with the potential to unlock several gigawatts of onshore wind capacity across southern Scotland and northern England.
The Array is a seismological monitoring station in the Southern Uplands of Scotland which was established in 1962 to detect seismic signals from nuclear explosions. It is the UK's primary asset for monitoring underground nuclear tests and supports the UK's obligations under the Comprehensive Nuclear Test Ban Treaty. Onshore wind turbines emit seismic ground vibrations ("SGVs") that can interfere with the Array's detection capabilities, meaning that wind development in the vicinity of the Array must be carefully managed.
Since January 2018, when the proposed Faw Side Wind Farm caused a breach of the cumulative SGV threshold (set at 0.336 nanometres), the MOD has objected to all proposed wind turbine developments within the 50km Consultation Zone, effectively blocking new onshore wind development across a large swathe of the Southern Uplands.
The DESNZ Consultation
The DESNZ consultation, which closes on 15 May 2026, seeks views on a proposed updated approach developed by the Eskdalemuir Working Group, comprising DESNZ, the Scottish Government, and the MOD. The proposals fall into four broad areas.
Extended Exclusion Zone
The consultation proposes to formalise and extend the existing exclusion zone around the Array from 10km to 15km, within which no wind farm development would be permitted. The existing 50km Consultation Zone would be re-designated as a "Restricted Zone" covering the area between 15km and 50km from the Array, within which a new process for assessing and managing seismic impacts would apply. Data from the Xi Engineering studies commissioned by the working group indicated that a single turbine installed at 10km from the Array has, on average, the equivalent seismic interference of approximately 5,500 turbines at 50km, making the extension of the exclusion zone a critical step in optimising overall capacity within the wider zone. The extension would prevent deployment of around 0.8GW of pipeline capacity located between 10–15km but would enable significantly more development further from the Array.
Updated Predictive Methodology and Seismic Impact Limit
The consultation proposes to update the predictive model currently used to calculate SGVs to incorporate turbine-specific seismic data, replacing the conservative "worst case" approach introduced in 2014. The Xi Studies concluded that the 2014 model had the potential to over-estimate cumulative SGVs by as much as 36.1%. By applying the updated 2026 algorithm and accounting for consented and constructed developments only, the Xi Studies identified between 0.206324 and 0.245040nm of headroom within the 0.336nm threshold.
A new Seismic Impact Limit would be introduced, applied to each individual turbine within a proposed development and expressed in nanometres per square root of megawatts (nm/√MW). The limit is designed to prevent any single turbine from consuming a disproportionate share of the remaining headroom. The consultation proposes that the limit be set at a single point between 0.004614 and 0.005479 nm/√MW. At the lower end, this could enable deployment of around 3–5GW between 28–50km; at the higher end, around 4–6GW between 25–50km.
Developers would be required to generate SGV Reports using an open-access industry tool (hosted by Scottish Renewables) and submit these alongside their planning applications. If a developer wishes to propose a turbine not yet registered on the tool's Approved Turbine List, it would be responsible for testing and validating its seismic signature at its own expense.
Strengthened Legislative Framework
A significant element of the proposals is the introduction of new legislation requiring Determining Authorities to refuse, or decline to determine or accept, applications for wind turbine developments in certain circumstances. Specifically, the proposals would require Determining Authorities to:
decline to determine or accept applications within the 15km Exclusion Zone;
decline to determine or accept applications within the Restricted Zone where any proposed turbine would breach the Seismic Impact Limit; and
refuse applications within the Restricted Zone where the MOD has objected on grounds relating to seismic impact, such as breach of the overall threshold.
This represents a significant shift from the current position, under which the MOD's objection is treated as a "material consideration" but is not determinative; in theory, a Determining Authority could currently approve an application notwithstanding an MOD objection. The proposed legislative changes, enabled by powers in the Planning and Infrastructure Act 2025, would remove that discretion where Array safeguarding is engaged.
Headroom would continue to be attributed by the MOD on a "first come, first served" basis, with the date of attribution based on the date on which the relevant MOD office receives notification of the application from the Determining Authority. Repowering applications would be treated as new applications for these purposes.
Alternative Approaches
The consultation also invites views on alternative solutions for mitigating seismic interference, noting that DESNZ and the MOD have initiated a joint appraisal of potential alternative mitigation solutions. One option under review is the use of boreholes to place sensors deeper underground, thereby reducing background seismic noise. The Government has stated that it does not preclude pursuing an alternative approach if a more effective solution is identified.
The MOD Response
The MOD's response to its own consultation (which ran from September to December 2024) confirms the adoption of its new safeguarding approach, which took effect on 18 March 2026. The MOD's consultation arose from an undertaking given to the Court of Session following judicial review proceedings brought by Energiekontor UK Ltd, which successfully challenged the MOD's previous approach to the order in which it assessed the seismic impact of proposed developments.
The key elements of the MOD's new safeguarding approach are as follows:
First come, first served. Applications will be assessed on a first come, first served basis, with the order determined by the date on which the Defence Infrastructure Organisation (DIO) Safeguarding office receives the consultation request by email from the consenting authority. This replaces the previous approach, which treated Electricity Act applications differently from Planning Act applications and was found to be unlawful. Where more than one request is received on the same day, the MOD will rely on the time of receipt.
Audit of the MOD's List. The MOD has completed a comprehensive audit of its baseline list of existing, consented and pending wind turbine developments within the Consultation Zone. The audit revealed inaccuracies in the data previously held by the MOD, including instances where it had not been consulted on applications or variations, and where consents had been granted without conditions securing compliance with the parameters used to calculate SGVs. The audited list is published in the third appendix to the MOD’s response.
Scoping requests removed. Scoping requests will no longer be treated as applications for consent and have been removed from the MOD's List.
Threshold retained. The Eskdalemuir threshold of 0.336nm is retained.
Suspensive conditions. The MOD maintains its position that suspensive conditions (which would permit development to commence only if and when headroom subsequently becomes available) do not provide adequate protection for the Array.
Repowering. Repowering applications will be treated as new applications under the first come, first served approach. Limited exceptions apply for applications to vary, modify, or amend existing consents where the MOD has not previously objected and there is no increase in predicted SGV.
Re-consultation on changes. Where changes during the application process increase predicted SGV, the MOD will move the application to the end of its list, treating it as if received on the date of the re-consultation notification.
MOD's role. The MOD has been clear that optimisation of renewable energy generation within the Consultation Zone is not part of its functions, emphasising that its role is limited to safeguarding the Array. The MOD has stated that it will carefully consider any guidance adopted by the UK and Scottish Governments supported by legislative reform and consider what consequential changes should be made to its safeguarding approach.
Potential Capacity Unlocked
The Analytical Annex published alongside the DESNZ consultation provides indicative estimates of the capacity that could be unlocked. At the lower Seismic Impact Limit, deployment of approximately 3–5GW could be enabled between 28–50km, with up to 1.5GW potentially available pre-2030 assuming an optimistic deployment timeline. At the higher limit, around 4–6GW could be enabled between 25–50km, with up to 1.7GW pre-2030.
However, DESNZ cautions that there is considerable deployment risk for pre-2030 capacity, noting that the policy would need to be in place by mid-2026 to secure these figures and that actual deployment timelines would be dependent on individual planning decisions.
Comment
These publications mark a significant turning point for onshore wind development in southern Scotland and northern England. The effective moratorium on new consents in the vicinity of the Array since 2018 has been a major source of frustration for developers, and these proposals offer a credible pathway to unlocking significant new capacity.
The MOD approach, already in force, applies the existing 2014 algorithm and the audited baseline. The DESNZ proposals envisage a new 2026 algorithm, the Seismic Impact Limit, and legislative changes. The MOD has acknowledged that if the algorithm is replaced, its list and SGV calculations will be reviewed again. Developers will need to navigate both frameworks and understand the transitional period between them.
The retention of the first come, first served principle for headroom attribution in both the MOD's approach and the DESNZ proposals creates a competitive race dynamic. Developers with projects between 25–50km of the Array will be keenly assessing their turbine models against the proposed Seismic Impact Limit range and considering whether to submit applications promptly once the new regulations are in force. The risk of bed blocking by large developments close to the Array consuming disproportionate headroom is partially addressed by the extended exclusion zone and the limit but remains a concern.
The DESNZ consultation closes at 17:00 on 15 May 2026. The Government aims to publish a response in Summer 2026. The MOD's new safeguarding approach is already in force. For the pre-2030 capacity targets to be met, the new regulations and guidance would need to be in place by mid-2026.
