Twenty-three green-leaning House Republicans sent a letter to President Clinton earlier this month calling on him to stand firm against the destructive practice of mountaintop-removal mining. A federal judge ruled last year that the mining technique, which has decimated a number of West Virginia mountains and buried 500 to 1,000 miles of the state’s streams under rubble, violates the Clean Water Act and a federal mining act. But the Clinton-Gore administration has filed notice of intent to appeal the court decision and is trying to quietly slip a loophole into Clean Water Act regulations that would allow the practice to continue. The administration’s efforts are largely seen as attempts to appease powerful Democratic Sen. Robert Byrd (W.V.), who is a staunch defender of the mining industry.