Parc Lead Mine
|Date||21 July 2012|
|Location||Gwydyr Forest||SH 78749 60143; 53.12461°N, 3.81344°W|
Of the numerous lead mines in Gwydyr Forest, Parc Mine was the largest, most successful and the last to close. Official records of production date back to 1860, when the mine was operated as Gwydyr Park Consols by the D’Ersby and Gwydyr Company. There were a number of lengthy interruptions during its history and work at the mine ended in 1958. It was later used in 1962-3 for experiments into automated milling before finally closing for good.
Rock extracted from the mine was crushed on site and the lead and zinc ores separated before being sent elsewhere for further processing. Today there remains very little of the surface structures at the mine. In fact, remedial work was undertaken to revegetate the site in the 1970s in order to reduce the environmental impact from contamination from the spoil heaps. Erosion of the tailings was allowing lead and zinc to leach out into the nearby stream. Polluted water then entered the Afon Conwy, affecting agricultural land on its flood plain downstream. To counteract this, the waste tip was regraded, capped with a layer of shale and then seeded with a resistant species of grass.
Parc Mine played a role in a research project investigating the elastic behaviour of the Earth’s structure. Between 1972 and 1975, researchers from Bidston Observatory, Birkenhead set up a monitoring station in one of the mine’s tunnels 41m below ground. Loading on the surface of the Earth by the sea varies with the tides and this in turn causes variations in the tilt of land relatively close to the coast. Accurately measuring these perturbations and correlating them with the movements of the tides allows information about the elastic properties of the upper strata of the Earth to be inferred. The final conclusion of the project, however, was that, owing in part to deformations of the cavity of the tunnel itself, measurements of a high enough accuracy could not be obtained in mines and that boreholes would provide a more suitable location for this type of investigation.