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Parys in Springtime: Hazard management and steps towards remediation of the UK’s most polluted acidic mine discharge.

Lookup NU author(s): Professor Paul Younger, Dr Hugh Potter


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Mynydd Parys is a hill on the Isle of Anglesey in North Wales which is riven with old copper mine workings, dating back more than 3500 years. Continued movement of air and water through old workings generates extremely acidic water, though the average flow rate is only about 10 l/s. After the last underground workings closed in the early 20th Century, the interior of one of the adits was fitted with a concrete plug incorporating a valved pipe. Until about 1950, this valve was periodically opened to flush water into ponds filled with scrap metal, where copper was precipitated by the "cementation" process. When these operations ceased, the valve was left closed and the dam forgotten. In the late 1990s it was realised that failure of this dam could cause a devastating flood in the town which had since grown below the mine. A complex multi-stakeholder process was initiated to resolve this hazard. Removal of the dam diverted much flow from a second catchment, so most drainage now flows in a short channel to the sea; the impact on marine life is now being investigated. Pilot treatment trials recommended an HDS lime-dosing operation, for which funding is now being sought.

Publication metadata

Author(s): Younger PL, Potter HAB

Publication type: Conference Proceedings (inc. Abstract)

Publication status: Published

Conference Name: 9th International Conference on Acid Rock Drainage (ICARD)

Year of Conference: 2012