More than two decades after Baltimore first came under federal and state oversight to end sewage overflows, public works officials say resolving the problem could take another 20 years and hundreds of millions more in taxpayer dollars.

Baltimore’s Department of Public Works expects that by the end of this decade it will have eliminated 94% of wastewater overflows — a problem that’s imperiled the health of the city’s harbor and streams for decades — but officials say in a new report that getting to the finish line would require another $674 million.

That’s more than a third of the $2 billion needed to cover that first 94% of the problem.

And this spending could stress Baltimore’s financial situation, compounding debt the city has racked up to fix its troubled sewage system, DPW says in its 105-page report, which outlines plans for completing work required under federal and state oversight of the city sewage system.

In order to ease the pain for the city’s water and sewer ratepayers, Department of Public Works officials proposed in a plan released late last month to delay the deadline on the city’s consent decree to 2046 — 16 years later than the agreed-upon 2030 end date.

Alice Volpitta, Baltimore Harbor Waterkeeper for the group Blue Water Baltimore, has watched with frustration for years as sewage overflows persist in parts of the city, welling up from manholes and outfalls during heavy rains, flooding tributaries and rushing into the harbor.

The city hadn’t acknowledged that it would miss the end-of-decade deadline until DPW revealed its proposal late last month, but for Volpitta it explains a lot. She’d long worried whether the city could meet its consent decree requirements.

It feels a bit like learning your spouse has been harboring a gambling addiction, Volpitta said.

“At least now I know what the problem is,” she said, “and we can work together to get this back on track.”

The extension plan requires approval by the U.S. Environmental Protection Agency and Maryland Department of the Environment. DPW is accepting feedback until Wednesday, but state regulators plan to extend that comment period.

If approved, this wouldn’t be the first time Baltimore has missed a deadline to fix its sewage system.

Baltimore first entered this consent decree in 2002, during former Mayor Martin O’Malley’s first term. The city invested hundreds of millions of dollars but, as a 2016 deadline approached, officials negotiated to push the end date for the massive infrastructure effort to 2030.

Still, Baltimore has covered a lot of ground in the last two decades.

DPW reports that overflows are down 84% today compared to 2002. Officials expect to achieve a 94% reduction by the end of the decade, at which point the city will have spent $2 billion on system improvements.

This progress has reduced wastewater pollution in the harbor, where people have begun to swim in recent years, albeit infrequently and only under the right conditions.

But overflows persist. DPW reports that 104 manholes remain in violation of consent decree requirements, resulting in millions of gallons in wastewater overflows.

Assessing progress can be tricky. The city’s report highlights dramatic declines since 2018, but that was a historic year for rainfall that caused devastating floods in the region. If Baltimore gets another year like that, it’s not clear how the system would hold up.

Continuation of the consent decree also hinges partly on participation by the EPA, which under President Donald Trump has emphasized deregulation. The Trump administration has ended consent decree oversight of police departments in cities like Louisville, Kentucky, and Minneapolis. It’s not clear how new EPA leadership could shift the approach to water regulation.

The EPA did not answer emailed questions on Baltimore’s extension proposal.

In their plan, public works officials suggest that this final phase of wastewater projects may not be worth the cost. Remediating the final 6% of overflows would cost hundreds of millions of dollars for “relatively minimal” environmental benefits, the report states.

DPW spokeswoman Jennifer Combs said Public Works officials believe state and federal regulators should consider affordability for ratepayers when determining whether the city needs to spend so much more. They also lay out concerns that current projections may saddle them with more work than is necessary.

As the department notes in its proposal, Baltimore has racked up debt to finance wastewater system improvements. Remaining work under the consent decree, it said, “will jeopardize [the city’s] financial stability and create an environment where it cannot secure necessary funding for capital projects.”

Already earlier this year, Mayor Brandon Scott’s administration approved rate hikes on water and wastewater services of as much as 15%.

Asked whether the city hopes to negotiate an end to its consent decree without completing these final projects, Combs said officials will discuss “consumer affordability concerns” with state and federal regulators, but added the city remains committed to meeting the terms of its consent decree.

MDE spokesman Jay Apperson said the state recognizes the city’s significant progress, as well as the substantial work remaining.

“We will weigh all of the factors involved, including the cost to ratepayers, while maintaining accountability to the agreement’s requirements,” Apperson said in a statement.

To Volpitta, the city’s claim that eliminating overflows won’t make much of a difference for local water quality is concerning.

For one, the city’s consent decree doesn’t address one of the most pernicious issues with the sewage system: the backups that routinely flood residents’ basements.

Volpitta also worries the data used to measure sewage overflows underestimates the problem. Conditions have changed since the city entered its consent decree in 2002. Climate change is bringing heavier storms, and the harbor advocate said she hasn’t seen evidence that the city’s models account for these changing conditions.

City officials, meanwhile, think projections may overstate the problem. Their data relies on modeling rather than reports of actual sewage overflows, and one reason the city wants an extension is to allow more time for field assessments.

Otherwise, DPW’s proposal argues, Baltimore could burn hundreds of millions of dollars based on shoddy estimates.