Some while back the Environment Agency produced a document listing a "top 50" non ferrous metal mines impacting on the environment in Wales.
Here is the link
http://www.environment-agency.gov.uk/regions/wales/426317/393155/ It leads off to all sorts of downloadable PDF files (report, maps etc) that are of interest.
(I've posted it on this forum because most are in mid Wales)
Incidentally, as well as the usual suspects, the list has some anomalies (I'm pretty sure that at least one mine is mis-identified). I think this reflects the original protocol that dates back to the National Rivers Authority (pre EA).
See what you think