In the late 1990s, surveys of the mine's hydraulic systems revealed that a large reservoir held back by a dam in an underground working was in poor condition. An assessment made at the time considered that failure of the dam was likely and that catastrophic failure could inundate parts of Amlwch causing loss of life and substantial damage to property. An added complication was that the water in the underground reservoir was highly polluted by copper and other metals and was very acidic. In 2003 a carefully controlled drainage operation was carried out which dropped the water levels by 70 metres (230 ft), releasing the pressure on the dam and enabling its removal. The removal of the reservoir also gave access to many more passages and to a connection to the nearby previously inaccessible Mona Mine. The entry into these sections was filmed for the TV series Extreme Archaeology.
Taken - 26/09/2014
Location: Parys Mountain, South of Amlwch, North Anglesey, North Wales
Photographer: Stephen Dutch