The volume of raw sewage that flowed into the Jones Falls, the stream that cuts through the heart of Baltimore before emptying into the harbor, was bigger than first reported, Maryland environmental regulators said Friday.

Roughly 1.7 million gallons of untreated sewage flowed into the tributary this week , according to the Maryland Department of the Environment. That’s more than 300,000 gallons over the initial estimate.

State and city officials were still investigating the cause of the overflow Friday afternoon, and the Jones Falls appeared to run clear and odor-free earlier in the day.

The overflow, though, is the latest flare-up in a decades-long struggle to stem the tide of sewage that escapes Baltimore’s old pipes and runs into its waterways, contaminating them with bacteria and harmful nutrients.

Under a state and federal consent decree, Baltimore public works officials anticipate that they will have to spent $2 billion to fix these overflows by the end of the decade, but millions of gallons of sewage still escape the system each year.

The city’s Department of Public Works wants to extend the deadline for compliance with its sewage consent decree by 16 years, until 2046.

A spokesperson for the Baltimore Department of Public Works did not immediately respond to follow-up questions about the incident by late Friday afternoon.

While sewage overflows on this scale remain too common in Baltimore, Alice Volpitta, a harbor water quality watchdog with the group Blue Water Baltimore, said this week’s incident was particularly concerning.

Overflows are typically driven by heavy rains that flush sewage out of the underground system and into the harbor and its tributaries, the water advocate said. In this case, though, rain wasn’t the trigger — Baltimore has had a dry week — meaning this overflow wasn’t diluted by stormwater.

It was pure, raw sewage, Volpitta said.

Though Baltimore has made headway in tackling its problem with sewage overflows, Volpitta thinks the public needs to be aware that there is still “the potential for things to go very wrong very quickly.”

The Jones Falls enters a century-old tunnel south of the site of this week’s spill and flows beneath the city to reach its terminus at the harbor, and Blue Water Baltimore has long advocated for signs around the harbor that indicate the risks of sewage overflows.

DPW has said the event started around noon Wednesday near the 2200 block of Huntingdon Avenue, an area in Remington north of the Streetcar Museum on Falls Road, and persisted until 4:30 p.m. Thursday. Officials said hundreds of thousands of gallons of untreated sewage escaped through a manhole and travelled down a storm drain, which emptied the waste into the Jones Falls.

MDE spokesman Jay Apperson said Friday that city officials had constructed a bypass that has prevented more sewage from escaping. The city believes a broken pipe may have resulted in the overflow, according to Apperson, but the cause of the break remains under investigation.

While DPW says the city is on track to eliminate 94% of its wastewater overflows by the end of the decade, tracking the problem can be tricky. The city believes modeling may overstate the extent of the problem, while advocates like those at Blue Water Baltimore worry about the opposite.

Either way, overflows persist. DPW reports in its recent consent decree proposal that 104 manholes remain in violation of requirements. Data compiled by Volpitta, meanwhile, tracked 32 million gallons of sanitary sewage overflows in 2024.

A 2015 report by the Environmental Integrity Project found that Baltimore had piped more than 330 million gallons of raw sewage and stormwater into the Jones Falls over five years, and Volpitta said this stretch along Falls Road remains a problem area for overflows.

For Dick Williams, a Bolton Hill resident and board member with the group Friends of the Jones Falls, this week’s incident is a reminder of the challenges facing the urban tributary.

DPW has fielded community backlash lately over a proposal to move a city dump from Remington to a site along Falls Road within the tributary’s 500-year flood plain.

At the same time, this overflow occurred as regulators are fielding feedback on Baltimore’s request to delay the deadline on its sewage system consent decree. A public comment period on that proposal closes Dec. 1.

“What happened on Wednesday was just a prime example” of the challenges facing the Jones Falls, said Williams. “Why are we letting up the pressure [on] getting the aging sewage system fixed?”