Judicial review launched over approval for hydroelectric scheme in national park

Cymdeithas Eryri (the Snowdonia Society) argues that Eyri National Park Authority did not properly consider that the scheme would damage the Rhaeadr y Cwm waterfall and the surrounding landscape in various ways.

The national park authority’s Planning & Access Committee resolved at a meeting on 24 June to grant permission. The decision notice granting planning permission for the scheme was issued on 15 July 2026.

The scheme, proposed by Bala-based renewable energy company MED Dafydd, would generate up to 600kW of electricity and its developers have said it could produce enough power to serve around 700 homes.

It would involve building a small dam on the Afon Cynfal and diverting water from the waterfall through a pipe to generate electricity.

Those opposing the scheme argue that nearly 70% of the water would be diverted away from the waterfall into a plastic pipe at peak times, threatening the sensory experience and unique environment associated with this special place.

Cymdeithas Eryri is basing its judicial review challenge around “grave concerns” about aspects of the decision-making. 

This includes the authority’s alleged failure to explain and apply the requirements of national planning policy (Planning Policy Wales: PPW) regarding the circumstances in which approval for proposals damaging a Site of Special Scientific Interest (SSSI) can be granted and to satisfy the requirement that there are “wholly exceptional circumstances” for granting permission, as also set out in PPW.

The vote to approve the application was close – an 8 to 7 majority – with five of the six Welsh Government appointees to the Authority’s Board voting against it and the sixth unable to participate in the process.

Graeme Cotterill, Director of Cymdeithas Eryri, said: “Taking this step is unprecedented for Cymdeithas Eryri.  In our 60-year history, we have engaged with countless Eryri National Park Authority planning decisions – but this is the first time we’ve legally challenged one.

“Whilst our close working relationship with the Authority in recent years benefits everybody and we intend it to continue, it is important that we challenge decisions that we and our supporters feel are not made in the Park’s best interest.”

A spokesperson for Eryri National Park Authority said: "The Eryri National Park Authority can confirm that a claim for judicial review has been made in relation to its decision to approve a hydro-electric scheme on the Afon Cynfal. The Authority is currently considering the content of the claim."

The Cardiff Administrative Court issued the sealed claim form on 8 September 2026 and the claim has been formally served on the parties. A decision on whether the claim will proceed to a full hearing is expected by the end of 2026 with a final decision unlikely until mid/late 2027.

Cymdeithas Eryri is represented by Ricardo Gama, Carol Day, Lily Hartley-Matthews and Romany Kisbee-Batho of law firm Leigh Day.

Hartley-Mathews said: “The fact that Cymdeithas Eyri has taken this unprecedented step demonstrates how seriously it views this decision. This case concerns one of the most iconic waterfalls in Wales and a landscape afforded some of the highest levels of environmental protection available. At its heart, the claim is about ensuring that this decision to approve major development in Eryri National Park has been taken lawfully and in accordance with the national and local planning policies intended to protect places of such significance.”

Harry Rodd