The standing remains of the Llyn Eigiau Dam Wall are approximately six to seven metres in height, and constructed of stone and concrete. The structure is over 1500 metres in length and it is broken through and ruined in places where parts of the walling have collapsed. The dam was part of the original water-catchment system dating from 1907 to 1911 that supplied the hydro-electricity station at Dolgarrog. On the second of November 1925 the mass concrete gravity dam collapsed and swept away a lower dam. The volume of water reached the Dolgarrog village where it killed sixteen people. The dam was never repaired.

Source: David Gwyn & Merfyn Williams (1996) `A Guide to the Industrial Archaeology of North West Wales?. Association for Industrial Archaeology

RCAHMW, 15 November 2011.