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New Bedford sailors did a double-take on a Saturday morning in mid-September when plumes of the normally blue harbor water turned a deep, wine-dark red.
The unusual color wasn’t a rust tide or environmental disaster, but a dye study conducted by the Massachusetts Division of Marine Fisheries. Management officials hope the study, which involves dying New Bedford’s wastewater with 100 gallons of EPA-approved red dye, will help them better understand how the city’s treated sewage moves throughout Buzzards Bay.
Dale Leavitt, a shellfisherman and aquaculture industry advocate, is particularly invested in their results. Since 2021, Leavitt has operated a 47-acre oyster farm in Nasketucket Bay in Fairhaven. In 2024, he and seven other area oyster farmers received word that the bay would be subject to more stringent food-safety regulations, due to the high volume of wastewater flowing out of New Bedford’s wastewater treatment facility.
These new rules were based on a mathematical model from University of Massachusetts Dartmouth’s School of Marine Science and Technology, or SMAST. Leavitt hopes that the dye study will tell regulators something different.
“At this point, it’s really hard to speculate as to where [the water] is all going to go,” Leavitt said. “The good news is that we now have harder data than what we had before.”
Beginning at 2 a.m. on Sept. 12, researchers began releasing rhodamine dye aboard a boat off the coast of Fort Taber. By 8 a.m. that morning, a cloud of reddish-purple water had already begun to form.
The fluorescent red dye is designed for water tracing because it does not harm the environment and it takes over two weeks to break down, giving researchers ample time to track how treated sewage moves through the bay.
Researchers continued to monitor the plume until Thursday, Sept. 17. To better understand how the water moves through the shellfish themselves, Leavitt and another shellfisherman Scott Soares donated oysters to the research.
“The oysters, if there are pathogens, such as coliform bacteria in the water, then they will concentrate them, because that’s their food and they’re filtering small particles out of the water,” Leavitt said.
Scientists will finalize the results of the study next year. Their findings will help update maps of wastewater flow and help inform emergency response if the wastewater treatment facility fails.
Treated sewage isn’t the bay’s biggest problem
But even armed with more knowledge, Leavitt and his industry peers will still have to live with wastewater. The dye study monitors treated sewage, which theoretically contains no pathogens. But during heavy rainfall, millions of gallons of untreated sewage and stormwater spill out into the harbor in what’s known as combined sewer overflows (CSO). In the event of a CSO, Leavitt’s farm must cease harvest for 21 days.
This year, a relatively dry year, New Bedford’s wastewater system has already dispensed 296 million gallons of sewage and stormwater into the harbor, 50 million gallons of which spilled out the week of Sept. 13. That takes the year-to-date total past the 250 million gallons released by this time in 2025. And while many East Coast cities are working to reduce combined sewer overflows, New Bedford sits closer to the state’s shellfish industry.
So far in 2026, Leavitt’s Fairhaven oyster farm has experienced four closures, including one that lasted almost all of July.
“It was a killer because one of our biggest markets is the months of June, July, and August,” Leavitt said. “I lost a third of my sales to combined sewer overflows.”
Since the 1990s, the City of New Bedford has invested almost $500 million on upgrading its combined sewer and stormwater systems, and it has reported an over 90% reduction in CSO discharge. But the last 10% will take years to address, city engineer Shawn Syde said in a public information meeting about CSOs earlier this year.
The cost to further upgrade the city’s sewage system sits around $1.2 billion. Syde also said that an increased percentage of the city’s resources will go toward updating the over 50-year-old wastewater treatment facility in the next few years. The city manages 27 CSO outfall pipes in total.
In neighboring Fairhaven, the cost to upgrade that town’s outdated wastewater treatment facility is estimated between $62 million and $71 million. One round of upgrades is expected to be completed this October.
Oyster farms can open after seven days if they test their shellfish and prove that they don’t contain any harmful bacteria. The trouble is, the nearest FDA-approved testing lab is located in Gloucester, so it can take up to 10 days for results to come back.
This past winter, Gov. Maura Healey came to New Bedford to meet with Buzzards Bay shellfishermen who advocated for improved local testing. At August’s Marine Fisheries Advisory Commission meeting, officials announced that they had secured funding for two new full-time positions on the agency’s shellfish team, including a lab technician based at the SMAST.
“They’re hoping that by us working harder in the South Coast, we could bring some relief to that in terms of shellfish closures,” commissioner Tom O’Shea said in the meeting. “But those CSOs are way too routine.”
Email Brooke Kushwaha at bkushwaha@newbedfordlight.org.
