A federal court judge has ordered the nation's largest public utility to dig up all its coal waste at a power plant site in Tennessee and move it to a specialized site that can prevent the waste from leaching into the Cumberland River.

U.S. District Court Judge Waverly Crenshaw came down with the decision late Friday, ordering the Tennessee Valley Authority power plant outside of Nashville to remove the waste.

His ruling favored legal claims made by clean water groups, saying coal ash storage at the Gallatin Fossil Plant has polluted the river for decades in violation of the Clean Water Act.

"While the decision to build the Ash Pond Complex is in the past, the consequences of that decision continue today, and it now falls on the Court to address them," Crenshaw wrote. "The way to do so is not to cover over those decades-old mistakes, but to pull them up by their roots. TVA, as the entity responsible for the ponds, must be the entity to do so."

It would cost TVA about $2 billion for it dig up and move the coal ash, the utility said. The large, federally-created power company said it plans to appeal the ruling, according to the Associated Press. A company spokesman pointed out that the judge noted that their have been no adverse health impacts or environmental damage due to the existing coal ash storage ponds.

The utility has said that an alternative to moving the coal ash waste would be to just cap the existing site. But the judge called the method of "cap and closure" a gamble.

"If closure in place did prove inadequate, the likely, if not inevitable, result would be yet more litigation — and, of course, decade after decade of the public simply having to hope that whatever unplanned, incidental leakage that was coming from the impoundments was not enough to do them significant harm," according to the judge's decision.