The state of Maryland on Monday joined the legal opposition to Virginia’s plan to drain coal ash impoundments into local waters, filing an appeal over the treatment of the discharge into the states’ shared Potomac River.

Maryland’s Department of the Environment joined its Department of Natural Resources in an appeal that makes official the concerns staff first raised in an eight-page letter to their counterparts at the Virginia Department of Environmental Quality in mid-January. Maryland formally notified Virginia of its intent to ask the Richmond Circuit Court to review the draining decision.

“I am deeply concerned that untreated or improperly treated coal ash could be deposited in the Potomac River,” Brian Frosh, Maryland’s attorney general, said in a statement released Monday. “Residents in the Washington region look to leaders in Virginia and Maryland to safeguard their natural resources, and the Potomac is a treasure that must be protected. Any plan to dump waste in the river needs heightened scrutiny and rigorous analysis.”

Maryland DNR had filed written comments objecting to a request by Dominion Virginia Power to drain water from coal ash impoundments at its Possum Point Power Station near Quantico into tributaries of the Potomac River. Such releases are “not in keeping with the spirit or intent” of the federal directive to decommission the so-called ponds and could “cause significant harm to human and aquatic life,” the DNR contended.

Maryland joins the Prince William County (VA) Board of Supervisors and the Potomac Riverkeeper Network -- represented by the Southern Environmental Law Center -- in challenging a decision by the Virginia State Water Control Board to permit the discharge of more than 200 million gallons from Dominion’s coal ash impoundments. The SELC is also representing the James River Association in a separate appeal over Dominion’s plans to drain coal ash impoundments at its Bremo Power Station, 30 miles southeast of Charlottesville on the James River.

This is not the first time Maryland and Virginia have clashed over the health and waters of the Potomac. The river provides drinking water to more than five million people in northern Virginia and the District, but falls largely within Maryland territory. A dispute between the two states over a drinking water intake made it to the U.S. Supreme Court in 2003, which decided in that case that Virginia did not need Maryland’s permission to lay the pipe.

Maryland’s letter about Dominion’s plans cites the concerns of health experts and Potomac fisheries officials about draining the impoundments.  Coal ash contains a variety of toxic contaminants, including arsenic, aluminum, barium and boron, that can cause cancer, reproductive problems and birth defects when present in high concentrations.  The state contends the discharges permitted by Virginia are not sufficiently treated under current regulations to safeguard the river as both a source of drinking water and spawning habitat for fish such as striped bass.

Dominion officials said Friday they are still drafting their plans for treating the water, but intend to remove the majority of those contaminants before discharging the water at Possum Point.