New Bedford working to reduce sewer overflows

New Bedford working to reduce sewer overflows

Blue Stream Shellfish owner Dale Leavitt says that in light of Massachusetts Division of Marine Fisheries’ recent shellfish bed reclassifications, and a changing climate, New Bedford must find a way to get its combined sewer overflows under control. 

Yet this job is easier said than done. 

Since the 1990s, New Bedford has invested hundreds of millions of dollars in reducing overflows, and upgrading its combined sewer system, city Department of Public Infrastructure Commissioner Jamie Ponte said. 

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The city has reduced combined sewer overflow discharge volume by more than 90%, from an estimated 3.1 billion gallons in 1990 to an estimated 183 million gallons in 2016. These projects have kept New Bedford in compliance with EPA administrative orders mandating their work, under the Clean Water Act. 

“It’s been a priority for us,” Ponte said. “The city’s reduced its contribution quite a bit over time, and we continue to do so.” 

The City has separated more than 330 acres of combined sewer service area and eliminated 11 outfalls. And it is working toward a 20-year combined sewage overflow reduction plan, submitted to the EPA in 2017. It comprises projects worth $427 million in 2022 dollars, which is projected to reduce combined sewer overflow discharges to roughly 100 million gallons annually by 2037. 

Yet a significant amount of projects still need to be planned out. New Bedford still has 27 CSO outfalls and still needs to separate more than 100 miles of combined sewer. 

New Bedford has one of the lowest median income levels in Massachusetts, and roughly one quarter of residents live under the poverty line. So progress is contingent on how much money the city can spend. The city decided against proposing a remediation plan to the EPA in 2017, worth $1.6 billion in 2022 dollars, which it deemed “unaffordable” for ratepayers. 

Ponte said the work in the current 20-year plan should ultimately limit combined sewage overflows to occurring only in an 100-year rain event, and not during everyday storms. Yet it won’t fully resolve the issue of combined sewer overflows in the city. 

When combined sewer overflow systems discharge

Credit: Kellen Riell / The New Bedford Light

Combined sewer systems, which are more often found in older cities, are designed such that stormwater and sewage run in the same pipes. When there is heavy rain or significant snowmelt, the system can get overloaded, so combined sewer overflows (CSOs) release some of the untreated sewage and stormwater into local waterways through outfalls so that it doesn’t back up into homes or public streets. 

When the weather is drier and there is no need for overflow, the sewage will get transferred to the local wastewater treatment plant, though sometimes there can be releases during dry weather due to malfunctions in the system.

Newer systems have separate piping for stormwater and sewage, but some older cities in Massachusetts, including New Bedford and Boston, are still operating to some degree with the older, combined systems.

According to the EPA, sewage discharges are a “major problem” in the country and cause some bodies of water to remain unsafe for swimming and fishing, with the problem being “especially acute” in New England.

Climate change may lead to more overflows

More intense storms and wetter conditions — the predicted impact of climate change on the region — are further complicating New Bedford’s work to reduce its combined sewer overflows. 

In 2022, considered a dry year, there were roughly 50 days with rains that triggered combined sewer overflows in New Bedford from July to December, producing an estimated 295 million gallons of discharge. 

In 2023, a wet year, there were roughly 125 days in which a combined sewer overflow occurred, producing an estimated 580 million gallons of discharge. 

New Bedford is “aware” of the stressors that climate change will put on its sewer system, Ponte said, and will work to account for them as it actualizes its 20-year plan. 

In 2024, there have been more than 30 days with a combined sewer overflow thus far, and a total estimated discharge volume of more than 300 million gallons of overflows. One storm in January put an estimated 50 million gallons of New Bedford combined sewer overflow discharge into Buzzards Bay. 

The methods New Bedford is currently using to estimate and publish combined sewer overflow volumes for the public are imprecise, Ponte said. The city is investing in studies of its sewer system that should improve these estimates.

He added that these annual combined sewer overflow volumes need to be examined in relation to multi-year averages — or “typical” wet and dry years — to draw conclusions about the overflows over time. 

DMF’s model-based buffer zones for the New Bedford and Fairhaven treatment outfalls will be a “consideration” in planning out the next five years of projects. Yet right now, Ponte said, it will not alter New Bedford’s current 20-year plan to address combined sewer overflows, given the lack of statistical data from local waters showing real health risk. 

“Some evidence needs to be found to solidify that stance,” he said. “It’s hard to say that all the projects that we have prioritized before to be the most effective and efficient, aren’t sound anymore.” 

Christian Petitpas, DMF’s South Shore shellfish program leader, said shellfish growers may need to lobby legislators for more funding to resolve combined sewer overflows in densely populated cities like New Bedford. She added that the city could consider options like combined sewage overflow storage tanks to reduce the amount of untreated sewage that flows into the water. 

Email climate and environment reporter Adam Goldstein at [email protected].

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