The Eryri hydro scheme proposed beside Rhaeadr y Cwm waterfall has suffered a major legal setback after Eryri National Park Authority agreed that its planning approval should be quashed. The concession follows a judicial review claim by Cymdeithas Eryri, also known as the Snowdonia Society, concerning the treatment of a Site of Special Scientific Interest (SSSI).
The conservation charity and its lawyers announced the development on 7th October 2026. The authority accepted a challenge to the way its Planning and Access Committee was advised about Welsh national planning policy. That is a significant outcome for the particular consent, but it should not be described as a fully reasoned court judgment on every environmental allegation.
The scheme would create a hydroelectric generating facility of up to 600kW on the Afon Cynfal near Llan Ffestiniog. Its proposed abstraction could, according to the challengers, divert as much as 70% of the water away from the waterfall at certain times. I’d keep two questions separate here: whether the authority followed the right legal process, and whether the hydro scheme could ultimately be acceptable in this protected landscape.
Eryri hydro scheme: what the authority conceded
In a 7th October statement, Cymdeithas Eryri said the national park authority had conceded that one of its legal arguments was arguable and that the decision to grant permission was potentially unlawful and should be quashed. The society said the authority had not accepted most of its other arguments, and expected the application behind the Eryri hydro scheme to be reconsidered by the Planning and Access Committee, perhaps as soon as 25th November.
The claimant’s solicitors, Leigh Day, reported that the authority accepted the ground alleging a failure to advise members that the proposal behind the Eryri hydro scheme did not comply with national planning policy for development affecting an SSSI. A Landmark Chambers case note likewise reports that the authority conceded the claim after proceedings were issued.
There is an important procedural distinction. An agreement to consent to a quashing order is not the same as a published judgment after a contested hearing. Neither a sealed court order nor a full substantive judgment has been independently verified for this report. The defensible present account is that the authority has conceded a legal ground and agreed to the consent being quashed, with redetermination anticipated.
What the original 600kW permission covered
The authority’s official Planning and Access Committee material identifies application NP5/59/495C, made by MED Dafydd for land near Pont yr Afon Gam at Llan Ffestiniog. The works comprise an intake weir, an extraction pond, an approximately 1.2km below-ground penstock, turbine and metering buildings, access changes, construction areas and an electricity connection.
According to the society’s procedural account, committee members voted on 24th June 2026 to approve the proposal behind the Eryri hydro scheme and the formal permission was issued on 15th July. Contemporary reporting recorded an eight-to-seven vote. The previous recommendation to grant permission should not be confused with the actual committee vote or with the later issue of the decision notice.
The developer’s stated objective was to generate renewable electricity, with a claimed output potentially equivalent to the annual demand of around 700 homes. That comparison describes an energy-production estimate, not a housing planning permission. The consent concerns physical engineering works and water abstraction in a highly sensitive environment, with benefits and impacts requiring their own assessment.
Why Planning Policy Wales matters for SSSIs
The central planning-policy issue concerns the special protection afforded to SSSIs. Planning Policy Wales, Edition 12, paragraph 6.4.26, establishes a presumption against development within an SSSI other than development necessary for its management and against proposals outside a designation which are likely to damage it. It requires careful assessment of impacts on the features for which the site at the centre of the Eryri hydro scheme was designated.
Paragraph 6.4.27 addresses wholly exceptional circumstances, appropriateness, the absence of likely damage and agreement for mitigation and enhancement in the context described by the policy. These are not optional matters that can simply be balanced away because a scheme offers low-carbon energy. The claimant’s accepted ground was that the committee had not been properly advised on the relevant policy conflict.
That finding about the advice given to decision-makers has a significance distinct from whether the proposed scheme would ultimately be acceptable. An authority may have to consider the application behind the Eryri hydro scheme again with a properly framed policy assessment. It does not follow from the concession alone that every hydroelectric proposal within an SSSI is prohibited or that the developer can never secure permission.
Wildlife, waterfall and landscape concerns
Rhaeadr y Cwm lies within the Cwm Cynfal SSSI and the wider Migneint-Arenig-Dduallt designated landscape and habitat complex. Conservation organisations have raised concerns about altered hydrology, bryophytes including moisture-dependent mosses and liverworts, and the visual and acoustic experience of the waterfall. Those are environmental claims advanced by objectors; they must not be reported as findings made by a court.
The North Wales Wildlife Trust has warned that reducing flows could threaten sensitive habitats. Objectors also questioned construction disturbance and landscape impacts associated with the underground pipeline and access route. Previous council documentation addressed conditions for construction management, ecological oversight, landscaping, watercourse crossings and an abstraction licence.
Campaigners reported roughly 1,590 objections to the application. Objection totals can indicate public interest, but they are not substitutes for applying the statutory and policy tests to a proposal’s effects. Practitioners should assess the adequacy of surveys, likely effects, mitigation commitments and advice to members separately from the number of representations received.
The judicial review timeline and what follows
The society says it filed its judicial review claim on 26th August and that the Administrative Court in Cardiff issued the sealed claim form on 8th September. Its public account describes a concession received in late September, reported publicly on 7th October. The challenge was made after a planning permission had been issued; it was not an ordinary planning appeal against a refusal.
Once any quashing order takes legal effect, the application returns to the decision-making process. The same proposals may be reconsidered, potentially with an amended officer report, new advice or further material if required. The claimant expects another committee consideration, but the suggested November date should not be treated as an officially fixed hearing until the national park authority publishes its agenda.
Graeme Cotterill, the society’s director, described the result as the first step in an ongoing battle
. That restrained description reflects the position: one ground has been conceded, but the future planning merits and final legal orders should not be presumed. The developer and authority may still need to address the wider arguments raised by opponents.
Lessons for Welsh planning authorities and developers
The practical lesson is about the quality of decision-maker advice. Where a proposal affects an SSSI, an officer report should make the relevant policy presumptions explicit, identify any departure from policy, and explain the evidence said to justify the recommendation. A general reference to environmental benefits is not sufficient to demonstrate that the specific policy tests have been applied.
Members should be able to distinguish protected-site effects, mitigation proposals and renewable energy benefits before voting. Developers should likewise establish whether the surveys, abstraction assumptions and construction methods adequately address the protected features. An apparently positive recommendation can remain vulnerable if the committee was not properly directed on national policy.
This is a Wales-specific national policy story. English, Scottish and Northern Irish statutory designations and policy frameworks must be assessed separately. Readers interested in the wider relationship between ecological protections and planning decisions can also review Planning Geek’s Pembrokeshire protected-site case-law summary, while the current Welsh national planning framework consultation provides context for continuing national policy work.
Primary records and reporting caveats
The essential contemporary records are the claimant society’s 7th October update, Leigh Day’s legal account, the national park authority’s committee report and Planning Policy Wales. They support the nature of the proposed development, the policy issue and the announced concession.
This article does not present a published judicial judgment or court order as available when neither has been verified. It does not assert that a new committee decision has been reached, nor that permission has permanently been refused. The next meaningful update will be an official court disposal or an Eryri National Park Authority committee notice explaining how application NP5/59/495C is to be reconsidered.
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