It is now possible to imagine the beginning of the end of a ruinous form of mining called “mountaintop removal.” Local opposition is growing, and the Environmental Protection Agency is tightening rules and threatening to veto one of the largest projects ever proposed.

Enormous harm has already been inflicted on Appalachia’s environment, most acutely in West Virginia. Mountaintop mining involves blasting the tops off mountains to expose subsurface coal seams. The coal is trucked away, but the debris is dumped over the side into the valleys, forests and streams below. As many as 2,000 miles of clear-running streams have been poisoned or buried in this fashion.

The dumping is a clear violation of the Clean Water Act. Regulators during the administration of President George W. Bush willfully looked the other way. The Obama administration is trying to turn things around. First it agreed to review about 80 existing permits. Then it raised the bar for new permits  tightening stream protections and promising a case-by-case analysis of new projects instead of the blanket approvals granted before.

Most important, in June, the E.P.A. and the Army Corps of Engineers announced that before granting any new permits they would insist on a robust scientific analysis of a proposed mine’s downstream impact on fish, salamanders and other aquatic life. If the agencies remain true to their word, this new guidance  required under the Clean Water Act, but ignored for years  could make mountaintop mining all but impossible.