Campaigners have knocked back plans for a hydroelectric scheme in Eryri National Park.  

The challenge by the Snowdonia Society saw the park authority agree to withdraw approval for the scheme, which proposes diverting water away from Rhaedr y Cwm waterfall.   

Campaigners argue the development would negatively impact the waterfall and damage the surrounding environment and wildlife, outweighing any benefits of the energy generated by it. 

The park authority accepted one of the grounds of challenge submitted by campaigners and agreed to quash the plans, which will now be re-reviewed. 

Plans for the scheme were approved in June, proposing the construction of an intake weir and underground pipe from the Afon Cynfal river near Llan Ffestiniog, diverting, at times, up to 70 per cent of the water at Rhaedr y Cwm waterfall away to be used for electricity production. 

Some 1,590 objections were submitted, with Ffestiniog Town Council also opposing plans. 

Following park approval, campaigners started a judicial review challenge.  

The site of the proposed scheme is partially located in a designated Site of Special Scientific Interest (SSSI), which offers protections to ecologically important land. Campaigners argued the park authority misinterpreted or misapplied planning policy for developments that affect SSSIs, and the scheme does not do enough to mitigate any environmental damage it might cause to the area, which is afforded special protections due to being a SSSI.

The group also says diverting water from the waterfall will have a negative visual and acoustic impact understated in plans. They say the proposed level of water abstraction will harm rare bryophyte populations, and there is a high risk of permanent scarring on the landscape due to the need for a vehicle access track, as well as the potential for erosion damage and sediment pollution. 

The group also argues the park authority was wrong to accept there was an overriding public need for the development. 

After filing its claim with the High Court in September, campaigners received confirmation from the park authority that it would consent to the quashing by the court of its decision to approve the hydroelectric development, conceding the first ground of the campaign group’s legal challenge. The ground alleged the park authority unlawfully failed to advise the planning committee the scheme did not comply with planning policy on development in an SSSI. 

Snowdonia Society director Graeme Cotterill said: “We are delighted part of our legal challenge to the decision was accepted as valid without having to hold a full court hearing, and grateful to all involved for this early resolution. However, we recognise this could be only the first step in an ongoing battle for the future of Cwm Cynfal’s waterfall and wildlife and Eryri’s special qualities as a National Park.

“We urge decision-makers to continue to consider the other important issues we and other objectors highlighted, including the lack of the ‘wholly exceptional circumstances’ that Planning Policy Wales is clear should be in place for any work affecting a SSSI. We firmly hope that the first judicial review application in our history will not need to be followed almost immediately by a second.”