The massive sewage spill on the Potomac River has left a lasting impact on public perception of “The Nation’s River,” with some people continuing to question the safety of getting in or on the water or eating any fish from it.
In late March, weeks after authorities had declared the river safe, a Maryland politics column published on Substack declared the Potomac “poisonous” and warned readers: “Keep children away. Keep dogs away. Keep yourself away.”
And as the weather warmed enough for fishing, one angler asked in mid-April on a Facebook page, “[A]re snakeheads still safe to eat after the big sewage spill?”
The collapse of the Potomac Interceptor sewage pipe on Jan. 19 dumped an unprecedented torrent of raw sewage into the river — as much as 300 million gallons, by one estimate. Researchers, state environmental officials and other experts say the environmental and health impacts could reverberate well into this summer and perhaps beyond.
One big yuck
As far as anyone can tell, snakeheads from the Potomac are safe to eat, though there are longstanding cautions about consuming some other fish because of unrelated contamination. And authorities have lifted the advisories against recreational contact and shellfish consumption that they slapped on the waterway in the wake of the spill. The only exception is the immediate area of the discharge near Lock 10 on the C&O Canal in Montgomery County, MD.
E. coli, bacteria in human or animal waste, tend to decay rapidly in water. In many cases, those and other pathogens can be gone within a few days. But studies show that they can survive longer — for weeks and perhaps months. Their persistence may depend on the water itself, with colder, murkier conditions potentially prolonging their lives.
Researchers also have found that fecal bacteria are more likely to last when embedded in soil — or in this case, in mud or sand on the river bottom or in its banks. Buried pathogens may return to the water if the bottom is stirred up, either by a storm or by people wading or splashing about. The size of the sewage spill and low flow of the river when it occurred are almost without precedent, which complicates matters, according to Natalie Exum, assistant professor of environmental health and engineering at Johns Hopkins University.
“In theory, it looks like the river is safe to go into,” she said during a late March webinar organized by the Potomac Riverkeeper Network. But while levels of E. coli measured at the river’s surface may appear reassuring, there’s a question about what may have settled into the river bottom.
“We are not out of the woods yet,” she said. People wading or swimming in the water could stir up the bottom sediment, she noted, and bacteria might get into a cut or break in the skin, leading to an infection.
“I’m the mother of four kids. They love to go in the water,” Exum added. “I can just picture what’s getting turned up in those sediments.”
Testing by the University of Maryland’s School of Public Health shows that bacteria concentrations are trending downward. But Dr. Rachel Rosenberg Goldstein, the microbiologist co-leading the effort, said she intends to keep up weekly sampling until her funding runs out in June. If she can find more money, she’d like to test until at least the incident’s one-year anniversary.
“It’s really important we keep following the impacts of this spill over time because this waterway is so dynamic, and we’ve never had a spill of this magnitude,” she said.
Watered down?
One thing might help: lots of rain.
“We always say it: dilution is the solution to pollution,” Exum said. A rainy spring could help wash sediments downriver, stirring up and eventually neutralizing any bacteria or disease-causing organisms stored in the bottom.
But downstream portions of the river can pay a price in the short-term. On Feb. 17, the day after a rainfall, sampling by the Maryland Department of the Environment showed E. coli levels far above the safe recreation threshold at Little Falls, just downstream from the spill, and lower but still unsafe at Chain Bridge in the District of Columbia. MDE detected an E.coli spike at Little Falls again in mid-March, when up to 1.5 inches of rain fell on the area.
The District’s Department of Energy and Environment likewise detected elevated levels as far downriver as the 14th Street Bridge on two occasions in March during or after rainfall.
Potomac Riverkeeper Dean Naujoks said sampling conducted by his organization during a dry week in mid-April measured high E.coli levels on the river’s surface at “Three Sisters,” a trio of small islands near the Key Bridge.
Overall, though, Adam Ortiz, an MDE deputy secretary, said he and other agency officials are “cautiously optimistic” that human health threats from the sewage spill are past.
“The trend line is definitely going in the right direction,” he said. But he acknowledged that conditions can change, “so we’re going to remain vigilant.”
Water sampling farther downriver never detected bacteria levels high enough to make oysters harvested there unsafe to eat. As a precaution, MDE closed shellfish harvesting down to the U.S. 301 bridge, reopening those waters on March 10.
The DC region’s drinking water has remained unaffected because the intake was upriver of the spill, officials say.
Researchers hit the water
Aquatic life may not be so fortunate. Initial examinations suggest water quality could get worse before it gets better.
A dozen researchers from the University of Maryland Center for Environmental Science partnered with state scientists for a two-day research expedition on the river over March 3-4. They sampled water, mud and air at 17 different sites from just upstream of the spill site to the river’s mouth at the Chesapeake Bay.
Their results at the spill site showed exceptionally high values for many indicators of untreated human sewage, including saltiness, E. coli, caffeine and acetaminophen (the generic name for Tylenol). Although the sewage had been contained to the C&O Canal by that point, the results suggest that some continued leaking out, said Lora Harris, who helped lead the UMCES research.
DC Water, the pipe’s owner and operator, returned the sewage to the temporarily fixed pipe on March 14 and plans to complete a permanent fix by the end of the year.
The sewage that poured into the Potomac not only carried human pathogens, but also a huge amount of nitrogen and phosphorus, the nutrients that feed algae blooms and deprive aquatic life of oxygen. Some worry that the massive spill could worsen the river’s summertime “dead zone” and lead to fish kills.
The UMCES researchers found nitrogen and phosphorus concentrations consistent with some of the worst years in recent memory. While those levels aren’t without precedent, the nature of the contamination could be setting up the river for a summer and fall of miserable water quality, Harris said.
That’s because what flowed from the pipe was what she calls “really juicy, organic stuff.” It hadn’t gone through any treatment processes yet, so its contents — the organic forms of carbon, nitrogen and phosphorus — are more likely to persist longer in the river and its sediment. .
It won’t be until May when water temperatures start to warm in earnest that scientists will have a better sense of the impact on this year’s Potomac dead zone. But Harris said she wouldn’t be surprised if it’s worse. Her team has already spotted an algae bloom downstream from the spill.
Public perception
The spill upended the long-running narrative of improving Potomac water quality, riverkeeper Naujoks said. His organization’s 37-station monitoring network had shown the river getting cleaner over the last seven years.
Now, he said, the only way to reassure the public that the Potomac is safe again is to keep monitoring water quality.
“The bottom line is people going in the river in July don’t want to hear about testing done in April,” he said.
But that could be the case in some instances. The U.S. Environmental Protection Agency will finish its water quality testing by May 1, according to an agency spokeswoman.
MDE has been sampling sediment and water quality weekly and will continue at least “into the early summer,” Ortiz said. “We’ll only stop when we’re confident that there’s no risk to public health. For the foreseeable future, we’ll be monitoring.”