Maryland has appealed a ruling by a special master appointed by the court that Fairfax County had the right, despite objections from Maryland, to build a new pipe extending into the river to withdraw water for its 1.2 million customers.
Maryland appealed the ruling when Ralph Lancaster issued it in December. The court said arguments on the appeal would be heard "in due course," but did not set a date.
"It would have been surprising if the court had decided not to hear it," Andy Baida, an assistant attorney general for Maryland, said Monday. "It's such a historic case, and it's got such significant issues."
Maryland and Virginia have been feuding over control of the river since Colonial times, arguing over fishing rights and water rights. Maryland owns the Potomac under a 1632 land grant from King Charles I, but a 1785 compact between the states gives Virginia certain rights of use.
The most recent controversy erupted over a 1996 application by the Fairfax County Water Authority to build a new intake pipe.
The authority said the existing intake pipe draws water that is too muddy, forcing it to spend an estimated $1 million a year removing silt. Fairfax officials said they needed a longer pipe to draw clearer water.
The Maryland Department of the Environment rejected the authority's application, arguing that sprawl development in northern Virginia was hurting the river.
A Maryland judge ordered the department to issue the permit, but Virginia appealed to the Supreme Court, contending it should not have been required to seek a permit in the first place.
Lancaster ruled that "Virginia and its citizens have the right, free of regulation by Maryland, to construct improvements in the Potomac ... and to withdraw water from the Potomac."
He said any notion that Virginia's rights to use the river can be regulated by Maryland "would certainly have been abhorrent to the Virginia commissioners and legislators" who approved the 1785 compact.
Maryland Attorney General J. Joseph Curran announced when Lancaster issued his ruling that the state would ask the Supreme Court to overturn it.
"Maryland has a responsibility, as owner of the Potomac River for nearly 400 years, in caring for this important natural resource to the fullest extent possible," Curran said.