This information was largely taken from EPA Region 3 publication A Citizen's Guide to Address Contaminated Coal Mine Drainage, EPA-903-K-97-003.
In some cases, there is still recoverable coal in the vicinity of contaminated mine drainage. Before AMD sites are scheduled for expensive treatment system construction, it may be worthwhile to have a geologist determine whether enough coal is present at the site to justify remining. Some old mines were worked before the development of modern equipment, so it is possible that significant coal reserves are still present. The remining contractors would apply for permits that would ensure that their operations prevent the generation of AMD by careful planning, engineering, and operational approaches to the remining work.
Remining as a Tool to Address AMD Problems, a presentation by Michael Smith, PA DEP.