An employee of the U.S. Department of Agriculture walks along the muddy shore of Roaches Run Waterfowl Sanctuary in response to an oil spill near Ronald Reagan National Airport on Feb. 8, 2016. (Kate Patterson/For The Washington Post)

Dominion Virginia Power, which last week acknowledged that an oil spill from its Crystal City substation had spread into a Northern Virginia waterfowl sanctuary and the Potomac River, could be fined up to $1.3 million, state officials said Friday.

The Virginia Department of Environmental Quality (DEQ) announced that it will assume from the Coast Guard the responsibility for overseeing the cleanup of the 13,500-gallon spill, and the agency issued a formal notice of violation. Its spokesman said any fine will have to be negotiated with the party responsible for the spill.

“If it is determined a fine is appropriate, we’d have to reach an agreement with Dominion,” DEQ spokesman Bill Hayden said. “It’s a civil penalty, and under state law, it has to be negotiated. . . . The maximum fine is $100 per gallon.”

The Coast Guard said 29 birds died as a result of the spill. Twenty other birds that had been cleaned by a wildlife rescue group are to be returned to the river Monday. The Coast Guard said that no additional sheening has been observed in the refuge or on the river and that no additional harm to wildlife has been reported.

State Sen. Scott Surovell (D-Fairfax) said he found it strange that a state environmental agency does not have the power to fine an organization that has caused damage to the environment.

“They probably spoiled a couple miles of shoreline in my district,” he said. “Given what’s gone on at Possum Point, this scenario presents a real opportunity for Dominion to show whether they’re responsible corporate citizens or not.”

The utility company won a permit last month to release about 215 million gallons of treated coal-ash water into Quantico Creek from its Possum Point power plant in Prince William County, despite strong opposition from local officials and environmental groups.

Maryland Gov. Larry Hogan’s administration this week said it plans to appeal the permit.

The Jan. 25 spill at Dominion’s Crystal City substation involved mineral oil, Dominion officials said. Coast Guard tests eventually determined that oil from that site matched the oil spotted a week later in the refuge and river.

The Coast Guard had previously identified the oil from the spill as a medium-weight fuel oil, akin to home heating oil. The mineral oil used at the substation would be included in that spectrum, the Coast Guard said.

Surovell said “mineral oil . . . sounds like stuff you feed to constipated babies. But this is not harmless stuff. It’s killed 29 birds and done who-knows-what other damage.”

Dominion spokesman Chuck Penn said: “Mineral oil is a nonhazardous product used to cool equipment in the substation. It is also used in baby oil and cosmetics.”