"A complete adjudication of the legality of the construction of valley fills under SMCRA and the CWA requires the presence of EPA in this action," Adams wrote.
In his motion, Adams did not challenge any of the central allegations of the Highlands Conservancy suit.
The other current defendant, the Corps of Engineers, did not file a motion to dismiss the case before the Tuesday deadline doing so. Corps officials have recently said they agree with several key allegations of the suit.
Lawyers for three Arch Coal Inc. subsidiaries filed their own motions asking that the mountaintop removal suit be dismissed.
In one of those motions, Jackson & Kelly lawyer Robert G. McLusky argued that if the court rules valley fills are illegal, it will destroy the Appalachian strip mining industry.
"Without valley fills and refuse impoundments, the coal industry could not exist in mountainous areas," McLusky wrote.
"The plaintiffs oppose large-scale surface mining, known popularly as 'mountaintop mining,'" McLusky wrote. "Their attack, however, is far broader. It challenges practices used by virtually all coal mines in the mountainous areas of West Virginia."
The case is before Chief U.S. District Judge Charles Haden.