CT towns have seen nearly 150 sewage spills this year. See where, why and what’s being done.

Between Jan. 1 and Nov. 30, there were 146 sewage spills into Connecticut’s rivers and harbors, according to state Department of Energy and Environmental Protection data.

That number is led by Norwich, which has had 41 spills into the Shetucket River and 16 into the Thames, which empties into Long Island Sound, data show.

That’s one reason the city recently bonded $199 million to completely overhaul its sewage-treatment plant on Hollyhock Island in the Yantic River, a project that will take five years.

In Norwich and three other Connecticut cities, outdated sewer systems that share the underground rainwater pipes, mean that several state rivers, and ultimately the Sound, become polluted after heavy rains.

But while there have been more than 10 spills a month this year — usually when rainwater overwhelms those old systems, Connecticut is in much better shape than it was back in the 1970s and before, say DEEP officials.

“We have been working on this problem for many years, since the 1970s,” said Ivonne Hall, assistant director of municipal wastewater at DEEP. “We have data that shows that we had 13 municipalities that had these combined sewer overflows,” which combine groundwater and wastewater in one pipe.

“At that time, we didn’t have the Clean Water Fund,” Hall said. “We had its precursor, which was the EPA construction grants program, but then in 1987, we got the Clean Water Fund in Connecticut, one of the first in the nation.”

The Clean Water Fund, which is composed of federal and state money, totaled $583 million for 2023-24, half of which went to combined sewer overflow systems.

Now there are four cities with combined sewer overflows: Norwich, with 57 spills to date this year; Bridgeport, with 42; New Haven, 30; and Hartford, eight. Two more are combined just before the sewage-treatment plants: Norwalk had two spills and Waterbury had one.

Even though there are just four combined systems left, they are in the cities that will be the most difficult to separate. Hartford has been working for years to address it and end the flooding and overflows.

“It’s just those last remaining CSOs that are going to be the hardest to remove because they’re in the most tightly populated areas,” Hall said. “Unfortunately, it’s going to be decades to come in order to eliminate it.”

When ‘it’s not raining”

Hartford, which has an underground storage tunnel to store water during heavy rains, intended to prevent overflows, still has a problem in the North End that combined sewer systems were meant to prevent: sewage backups into the basements of residents’ homes.

“Back about 100 years ago … particularly in really urban communities, the thought and the best engineering practice at that time was to have one pipe installed that would collect sewage, any other wastewater from people and their activities, as well as any rainwater that fell within those inhabited areas,” said Nisha Patel, director of DEEP’s Water Planning and Management Division.

“Because at the time the real driver was public safety,” she said. “There was one pipe that was constructed to collect that and then discharge it to the nearest water body,” she said.

In Hartford’s North End, that system hasn’t worked well, especially with new rainfall totals, and $85 million from the Clean Water Fund will be used to address the problems.

However, even towns with separated sewer and groundwater systems have had sewage spills this year: Fairfield, five, and Stratford, one.

The number of spills may not reflect how much sewage is being released into the rivers, Hall said.

“There are certain communities, like Hartford, which might have a fewer number of releases, but it doesn’t really tell you how much volume is discharged,” she said. The 41 spills in Norwich “are probably smaller than some of the other ones.”

“Norwich is a great example of what we’ve been doing but it also will tell you how long these projects take, because it takes a lot of years to plan, design, fund,” Patel said.

“Norwich started … about 10 to 12 years ago. … So it’s taken this long to go through all of that engineering, all of that project planning and financing to get to a point where we just did groundbreaking at that facility. And that’s not atypical, because these are highly engineered, highly expensive systems.”

Norwich has made “tremendous progress,” decreasing the volume of its spills by 53%, from 1.69 million gallons per inch of rain in 2018 to about 795,000 in 2022, according to Chris Riley, communications and community outreach manager for Norwich Public Utilities.

Besides totally renovating the sewage-treatment plant, the city has been relining pipes in the Greenville section by the Shetucket River, Riley said. He said when there are spills, which are approved by DEEP, just 1% is wastewater.

“We’ve made dramatic progress,” he said. “Norwich is an older city. We’ve got a lot of older infrastructure. Some of the CSOs are more than 100 years old and some of the infrastructure was put in in the ’50s. It’s well past its useful life, so we’re realigning some pipes, we’re eliminating them in certain areas. It’s expensive and time consuming, but it’s critically important work because we’re on a consent order with DEEP.”

“As it works now, if it’s not raining, the sewer system works fine,” said Larry Sullivan, integrity manager for Norwich’s water and wastewater divisions. “Depending on the rainstorm, if you get 1 inch of rain over 24 hours, they probably won’t activate. You get 1 inch of rain in an hour, it’s probably going to activate because the pipes get overwhelmed.”

There are 11 locations where wastewater can spill into one of the rivers, down from more than 50, Sullivan said. Seven spill into the Shetucket River; four go to the Thames.

Sullivan said the treatment plant handles 8.5 million gallons in dry weather and can handle up to 15 million during a rain. Once it’s rehabilitated, “the new plant will be able to treat 20 million gallons effortlessly,” he said.

DEEP requires towns and cities to warn residents not to go into the water near an outflow pipe after it rains.

“When we permit these facilities, the wastewater-treatment facilities that manage this wastewater, we require each of those municipalities that have the systems to say, where you have … a pipe that’s discharging into a water body, you have to put up signage to let residents know that, hey, there’s this kind of outfall, so be aware and don’t go in the water or don’t fish in the water right after a rain event,” Patel said.

She said there is also a citizen’s right-to-know law that requires municipalities to let neighboring towns and their own residents know of spills. DEEP has a page on X (previously Twitter), @ctsewagespills, where it posts notices.

“This is not the ideal. No one wants these things to exist,” Patel said. “But the fact that they are triggered when there are rainfalls, there is some benefit to the fact that the discharge of sewage is pretty heavily diluted with storm water.”

She said spills “generally get cleared away within 24 to 48 hours, depending on the specific flow conditions of that river or water body. So it’s not a lengthy period of risk. … It’s not a prolonged risk to aquatic life either.”

Ed Stannard can be reached at estannard@courant.com.