Ffestiniog Pumped Storage Scheme was opened in 1963. The reservoir, Llyn Stwlan, has a capacity of 2,000,000 cubic metres of water, retained by a dam 244m long and 37m high. The water is used to drive four turbines in Ffestiniog Power Station (nprn 401209) to generate electricity; in off-peak periods, the turbines act as pumps to force water back to Llyn Stwlan.
Source: Ffestiniog Power Station.
RCAHMW, 12 December 2011.