The ongoing Potomac River sewage incident is shaping up to be one of the biggest in U.S. history, some experts say.

In a Wednesday open letter to the local community, D.C. Water CEO David Gaddis called the January 19 event “deeply troubling,” saying people rightfully felt “concern, frustration, and a sense of loss.”

Part of the sewer system, the Potomac Interceptor, has allowed approximately 243 million gallons of wastewater overflow into the D.C.-area river since it collapsed. 

According to Gaddis, D.C. Water was alerted to the collapse when security cameras “detected unusual activity” near one of the agency’s odor control facilities that Monday evening.

“From that moment forward, D.C. Water crews and contractors mobilized around the clock — through sub-freezing temperatures and severe winter weather — to contain the overflow, protect public safety, and begin repairs to the 72-inch pipe,” the CEO wrote. “By January 24, an emergency bypass was activated to reroute flows and stop the discharge.”

In the initial press release alerting residents of the spillage, D.C. Water warned that the water could “contain many pathogens causing a variety of illnesses ranging from E. coli to hepatitis.”

“If people come in contact with the untreated overflow, they risk getting sick and bringing these pathogens into their homes,” officials said, advising locals to thoroughly wash off and disinfect if they come into contact with the contaminated water.

In a February 6 press release, D.C. Water estimated that approximately 243 million gallons of wastewater had overflowed from the collapse site, with approximately 194 million gallons overflowing within the first five days.

However, environmental group Potomac Riverkeeper Network claimed in a Wednesday Facebook post that the sewage spill had topped 300 million gallons.

A D.C. Water analysis of Potomac River flow data estimated that the peak discharge of wastewater, approximately 40 million gallons per day, represented about 2 percent of the Potomac River’s total flow during that period.  

While sampling within the drainage channel where the overflow occurred continues to show “elevated,” E. coli levels, the agency said that E. coli concentrations at all downstream locations sampled since February 1 have remained “within the U.S. Environmental Protection Agency’s acceptable range for primary contact recreational activities, apart from a single day at Fletcher’s Boathouse.”

Potomac Riverkeeper Dean Naujoks told the Baltimore Sun earlier this week that the only other spill that could compare in size was in 2017 on the U.S.-Mexico border, which caused a 230 million gallon overflow. 

Gussie Maguire, a staff scientist with the Chesapeake Bay Foundation, told the Hill that the Potomac River spillage is comparable to wastewater incidents in Baltimore.

“The way that I put it into perspective for myself and for people before, is I compared it to annual sewage overflow amounts,” Maguire said on Thursday. “You don’t really necessarily want to think about it, but there are a lot of sewage overflows going on in any particular year.”

“I follow happenings in Baltimore pretty closely, and their largest volume of sewage spilled in a year… The largest year that they’ve had in terms of volume in the last — in recent memory is from 2018, and they had right around 260 million gallons over the course of the entire year, or 250,” he explained. 

Olivia Rondeau is a politics reporter for Breitbart News based in Washington, DC. Find her on X/Twitter and Instagram.