About

About Ffestiniog Power Station

Commissioned in 1963, Ffestiniog Power Station was the UK’s first major pumped storage power facility. Its four generating units are capable of achieving a combined output of 360MW of electricity – enough to supply the entire power needs of North Wales for several hours.

The Generation Cycle begins at Llyn Stwlan – Ffestiniog’s upper reservoir. Large screens inside the intake towers are opened to activate the high-pressure downflow.

27 cubic metres of water per second are discharged through two high-pressure shafts (each 200 metres in depth), which are connected to four concrete-lined tunnels. Steel penstocks then direct the discharge into the station via inlet pipes and valves to start generation.

Water is captured in Tan-y-Grisiau and pumped back to Llyn Stwlan, usually overnight, to complete the cycle.

Environmental Considerations

The environmental effect of building a hydro-electric scheme in an area of such natural beauty was central in each decision-making stage. The site at Ffestiniog lies within the upland grasslands of the Moelwyns. Relics of the slate and metal mining industry are apparent within the landscape. Local farmers let grazing rights for sheep.

The site comprises the upper and lower reservoirs and associated dams, Llyn Stwlan and Llyn Tan-y-Grisiau respectively, and the power station complex. There is one geological Site of Special Scientific Interest (SSSI) located between the two reservoirs.

Construction

One of the most fundamental problems for the architects and engineers to overcome was how to dispose of approximately one million tonnes of rock excavated during construction. Sites were chosen where the rock could be dispersed around the contours of the local landscape. Indigenous grasses, trees, and shrubs were then planted to enhance the area. Buildings and walls within the station complex have been constructed from local stone, slate, and other natural materials.

Preservation of Natural Life

Much is done to preserve the rich and varied natural life that surrounds the power station. On the slopes leading to Stwlan Dam, purple bell heather covers the mountainside, providing a haven for a diverse range of insects, bees, and butterflies during the summer months.

The area offers a natural habitat for many of Britain’s less common bird species, including stonechats, pipits, tree creepers, peregrine falcons, and wheateaters.