Mining companies remove vast surface areas to expose the coal in a procedure known as mountaintop removal. The process often involves dumping the dislodged dirt and rock into valleys.
Environmentalists estimate hundreds of miles of streams have been affected, some of them obliterated, because of lax enforcement of the 1983 restrictions or different interpretations of the federal rule.
"Kentucky's vast water resources are critical to our health and economic development, and I do not believe the newly proposed waivers can be effectively and uniformly applied to protect these water resources,'' Beshear wrote.
Conway said he realizes coal is an integral part of Kentucky's economy and an important energy resource.
"Nevertheless, our rivers and streams are also critical natural resources that must be protected if we are to pass along a stable environment to coming generations,'' he said.
Conway, Kentucky's top prosecutor, said he believes the proposal has "the potential to open up increased environmental abuse'' in the state.