Five minutes was all it took to overwhelm the city of Holyoke's aging sewer pipes, during an intense rainstorm in western Massachusetts this summer. The storm caused the pipes to release 7 million gallons of mostly water and some sewage into the Connecticut River.
What followed was a video appearing to show toilet paper and sewage flowing down the Connecticut River in Suffield, Connecticut. The images were widely shared on social media.
As the video circulated online, two Connecticut Republicans reached out to the Environmental Protection Agency asking for help. They wanted answers on an issue that’s long plagued cities in southern New England – combined sewage overflows, or CSOs.
CSOs are a mix of stormwater and sewage released by older sewer systems into local bodies of water during periods of heavy rain.
“It's mostly stormwater, it's not wastewater,” said Mary Monahan, Holyoke’s interim director of public works. “It's been diluted. That doesn't mean we still want to do it, but it's been diluted.”
300 million gallons of water in 5 minutes
Combined sewage overflows are big – usually millions of gallons of water – and can include untreated, or partially treated, sewage.
But precisely how big and frequent these overflows are is directly related to the weather. Storm intensity, duration, and even things like how fast the snow melts, can all play a role, according to the Massachusetts Department of Environmental Protection.
On a dry day, Holyoke’s average flow of sewage and stormwater is 6 million gallons. But on July 27, heavy rain caused the city’s flow to jump from 6 million gallons to 327 million gallons in just five minutes, according to Jason Swain, project manager at the Holyoke Water Pollution Control Facility.
With climate change causing more intense rainstorms, older pipes common to New England are likely to get overwhelmed more frequently, Monahan said.
“Climate change and the increase in storm events, the increase in total rainfall and individual storm events, is exasperating this issue,” Monahan said. “Regular rain events don't create the problem. It's the large storm events that create the issue.”
One pipe for everything
Most cities in the United States have two separate sewer systems — one carries sewage to a water treatment plant, while another brings stormwater to a nearby body of water.
But four cities in Connecticut – Bridgeport, New Haven, Hartford and Norwich – have combined sewer systems. Those systems use one pipe to collect sewage from homes and businesses and stormwater from parking lots, streets and driveways.
There are 19 municipalities with combined systems in Massachusetts, according to a state report.
The idea of using one pipe for everything was popular in the 1800s, before water treatment plants existed and rivers were thought of as a “floating dump,” Monahan said.
Today, modern engineering has mitigated direct sewage discharges to an extent.
Many sewer pipes have a partial wall inside of them known as a baffle. On dry days, the sewage and stormwater flow through the pipe and hit the baffle, which directs the sewage and stormwater to a treatment plant.
The water is then treated and released into a nearby body of water.
But on days with a lot of rain, a surge of water and sewage overwhelms the system, flowing over the baffle and out into a nearby river.
Hartford and three cities in Massachusetts — Holyoke, Springfield, and Chicopee — release discharge into the Connecticut River. Norwich, Bridgeport and New Haven discharge into Long Island Sound.
There are also two smaller CSOs in Norwalk and Waterbury, according to a Connecticut environmental spokesperson. Waterbury’s discharges into the Naugatuck River and Norwalk’s into Long Island Sound.
Billions of gallons, but still a drop in the bucket
In 2024, Massachusetts released approximately 2.8 billion gallons of combined sewage overflows, while Connecticut released 1.2 billion gallons, according to state reports.
Nisha Patel, director of the water planning and management division at Connecticut’s Department of Energy and Environmental Protection, said the CSO discharge is more rainwater than sewage.
“I can't tell you that in all instances, it's half-half or 75% rain, 25% sewage” Patel said. “But what we can tell you is that a good chunk of it is rainwater, and the more intense the rain, the longer period of rain, the more the percentage of rainwater to sewage is going to increase.”
The discharge is small compared to the size of the Connecticut River, according to Patel.
“The river is flowing at over 100 times what that discharge is,” Patel said. “In terms of the river’s ability to accept these discharges and flush them out of the system and the state, it’s pretty effective.”
Without combined sewer overflows, heavy periods of rain or snowmelt would cause sewage to back up into people’s homes and pour out onto streets, or it could overwhelm the water treatment plant and potentially damage pumps or tanks.
“These are really technical, expensive features in wastewater treatment facilities,” Patel said.
“If a pump goes out, it's not that you can immediately order one on Amazon. These are really big pieces of equipment.”
Politicians want answers on upgrades that could take decades
Tami Zawistowski and Devin Carney, two Connecticut Republican state representatives, wrote a letter to the Environmental Protection Agency in August, asking for help in preventing Massachusetts and other up-river states from discharging rainwater and sewage into the Connecticut River.
Mark Sanborn, head of the regional EPA, wrote back on Sept. 18, stating that the “EPA has been working with Springfield, Chicopee, and Holyoke for many years.”
“Collectively, these communities have spent hundreds of millions of dollars towards infrastructure improvements that have reduced these discharges. While we have made progress in reducing CSO discharges, a significant amount of work remains,” Sanborn wrote.
Zawistowski said the reply “falls short of providing any immediate, short-term solutions and insists that changes are being made, albeit slowly and as funding permits."
"I appreciate the timely response and I'm glad we have open lines of communication with federal agencies as we continue to press for solutions," Zawistowski said.
Meanwhile, Connecticut has reduced its sewage discharges in recent years.
The state has invested more than $5.4 billion in updating its combined sewer systems, bringing the total number of Connecticut cities with the aging sewer systems from 13 to four, according to Will Healey, director of communications at DEEP.
But updating the sewer systems for the remaining four cities will likely take decades, Patel said.
“As to whether it's 2040, or 2050, or 2060, it's hard to say.”
Áine Pennello is a Report for America corps member who covers the environment and climate change for Connecticut Public.
