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Dinorwig Power Station

Llanberis, Gwynedd

DInorwig Power station footbridge model across the Afon and Mala

Sector: Conservation, Cultural, Industrial, Landscape, Master Planning
Client: Central Electricity Generating Board
Project value: £425 million
Project stage: Complete

Frederick Gibberd Partnership were appointed as the Landscape Consultants and Architects by CEGB in 1970.  The scheme was the development of  a hydroelectric power station within the remains of the old Dinorwig slate quarry which is located within the Lianberis pass. The power station, the first of its kind in the UK, generates energy during peak demands by potential energy. It uses the off peak electricity to transfer water from the lower reservoir (Llyn Peris) back up to Marchlyn Mawr reservoir and the cycle is repeated.

It was the largest civil engineering contract ever awarded by the UK government at the time and consisted of 16km underground tunnels in Elider mountain in Snowdonia National Park in a Special Area of Conservation within North Wales.

The new scheme reservoirs of Llyn Peris and Marchlyn Mawr were the main areas of focus by Gibberd. Marchlyn’s remote and wild setting in a natural hollow in the mountains and its curved plan form enabled it to be contoured naturally into its surroundings. All engineering structures were recessed into the mountain face with a design emphasis on blending into the scenery. External elements comprised stone masonry in keeping with the local vernacular of the Dinorwig area. Work’s to the lower Llyn Peris at the base of the quarry followed the same principles of random stone masonry, unifying the scheme with its quarry landscape. The construction of new roads and landscaping had to accommodate the variation of water levels by 2.8m and continue a seamless transition throughout the landscape. Contouring of the embankment along the river bank, is barely discernible with planting on the abutments merging with the existing planting on each side of the valley.

The scheme is now one of the main attractions of the Snowdonia National Park and includes the later construction of a tourist centre following the Gibberd masterplan. It is dubbed Electric Mountain and is one of Europe most imaginative environmental and engineering projects bolstering architectural design.

All excess water overflows into the Llyn Padarn . Both Llyn Peris and Llyn Padarn are ancestral homes to the Arctic char, a rare fish in the UK. The view of the potential risk to the species saw a rescue operation undertaken for the transfer of all char from Llyn Peris to suitable lakes in the local area.

Wildlife and environmental studies were carried out due to the unique biodiversity found in the area. This was carefully monitored with the emphasis on the design enabling the natural wildlife to thrive. Movement of Slate waste from all construction areas was a challenge to transport safely; in what was the largest excavation project before the building of the channel tunnel, this had to be carefully managed to minimise impact to the surrounding area.