South Coast oyster growers say sewage-related restrictions will hurt

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After a storm wiped out Luke Sebesta’s Dartmouth aquaculture business in 2022, he was looking forward to purchasing 20,000 seed oysters this spring to get it back up and running. But this March, the Massachusetts Division of Marine Fisheries announced new restrictions on shellfish beds in parts of Buzzards Bay. Now, his re-opening of his Nonquitt oyster farm — Buzzards Bay Oysters — is at a “standstill.”

“It’s making me question whether it’s even worth it,” he said.

On March 12, the state announced new regulations of the shellfish beds surrounding the New Bedford and Fairhaven wastewater treatment plant outfalls — the main discharge pipes for treated sewage. These changes are part of a statewide effort to expand the areas around these pipes that are closed to shellfishing — called “buffer zones” — to comply with requirements in the National Shellfish Sanitation Program.

These buffer zones are based on computer modeling of how treated sewage flows from treatment plants out of these pipes, and dilutes and disperses into its receiving waters near shellfish beds. They are meant to protect consumers from the risk of getting sick when eating shellfish grown near a wastewater treatment plant, if it fails and dispenses untreated sewage into the water. 

Roughly 90,000 acres of Buzzards Bay shellfish beds, stretching from Dartmouth to Mattapoisett, changed from fully approved to conditionally approved as a result of the computer modeling. That means oyster growers using these beds could now be shut down for seven to 21 days after episodes of “rainfall or seasonally poor water quality or other predictable events.” 

State officials say the change is a necessary concession. The U.S. Food and Drug Administration recommended fully closing down more than 103,000 acres of beds across Buzzards Bay, based on its modeling. The state says the new classification plan protects public health, keeps growers open, and complies with requirements in the National Shellfish Sanitation Program.

The Division of Marine Fisheries “is taking every possible action to comply with federal guidance while minimizing impacts on commercial fishing communities and aquaculture businesses,” said DMF director Dan McKiernan. 

Sewer overflows and oyster beds

Still, South Coast oyster growers want the state to do more to push back on the FDA. They have serious concerns about a local wrinkle to DMF’s reclassification plan which now threatens their viability: New Bedford’s combined sewer system.

Much of New Bedford’s wastewater system — which dates back to the 19th century — handles stormwater and sewage in the same pipes. It also features a series of relief valves that discharge untreated sewage and stormwater into local waters when the pipes exceed capacity during heavy rains, before they reach and overwhelm the plant. These events are called combined sewer overflows. 

These overflows protect the treatment plant from potential failures — the main concern guiding the buffer zone modeling. New Bedford’s wastewater treatment plant has never failed, according to a city spokesperson. The overflows also keep sewage from backing up into homes and businesses. 

But the untreated sewage in these overflows can also pollute Buzzards Bay waters to the point where DMF must shut down shellfish beds, to let potential contamination clear.

Dale Leavitt, owner of Blue Stream Shellfish in Fairhaven, said the state has suggested that 2 million gallons of combined sewer overflow discharge in New Bedford could be enough to temporarily close these conditionally-listed beds. He calculates that less than an inch of rain in a day could now trigger a closure.

Separating New Bedford’s combined sewer system is an ongoing, expensive, slow-moving project. The city’s population, and the amount of sewage it produces, have grown over the past decade. And strong rains are happening more frequently in the region — a pattern which is expected to  intensify with climate change.

So being classified as conditionally approved may severely limit local growers’ ability to sell oysters — even though oyster aquaculture has coexisted with New Bedford’s combined sewer system for decades, without any consumers getting sick.

“The amount of times they could close you down, it’s unnerving,” Sebesta said.

Several oyster growers across Dartmouth, Fairhaven, and Mattapoisett have been reclassified by the state’s buffer zone modeling. They argue that the FDA’s rule for these buffer zones does not reflect the real health risk of Buzzards Bay oysters. 

“The criteria that FDA is putting forth are very severe, and may not be appropriate for this situation,” Leavitt said. 

These growers add that DMF’s modeling did not include relevant data on viral and bacterial loads from local shellfish beds. 

“Business is being shut down based on speculation, not real data,” said Padanaram Oyster Farm owner Scott Soares.

State oyster industry representatives worry that DMF’s computer model may lead the agency to reclassify thousands more acres of Buzzards Bay oyster beds, without sufficient evidence of real health risk. 

Dartmouth’s wastewater treatment plant will be the next to get an updated buffer zone, followed by treatment plants in Bourne, Marion and Wareham. Close to 40 growers work more than 300 acres of oyster farms in Buzzards Bay, accounting for more than $3 million in reported revenue in 2022. 

“There’s the bigger, more regional concern we’re worried about,” said Massachusetts Aquaculture Association president Seth Garfield. 

And if DMF continues this modeling across the state, it could hurt Massachusetts’ $30-plus-million farmed-oyster industry — one of the largest on the East Coast. 

State officials are defending their decision, saying if they did not conduct this modeling — and act on it quickly — they risked the FDA finding them noncompliant with requirements in the National Shellfish Sanitation Program. The FDA could have asked the Interstate Shellfish Sanitation Conference — the program’s legislative body, made up of states, industry, and federal regulators — to ban all sellers of Massachusetts mussels, whole scallops, and clams, as well as oysters, from out-of-state markets. Together, those dealers accounted for commercial landings valued at more than $70 million in 2022.

The shutdown

The state’s decision to reclassify shellfish beds surrounding local treatment plant outfalls may have been sudden. But it was no shock to Leavitt.

“I knew it was coming, and I knew the results of the model could be problematic,” he said. 

In 2022, DMF reclassified shellfish beds in waters surrounding the North and South Rivers in Scituate, the start of its effort to update buffer zones around treatment plants. 

Oysters and other bivalve shellfish are vulnerable to contamination from harmful bacteria, viruses, and chemicals while filter-feeding in polluted waters. So the FDA says states should prohibit shellfishing in areas surrounding treatment plant outfalls where there is a ratio of one or more gallons of treated sewage to 1,000 gallons of receiving water. Areas in which the treated sewage-to-water ratio is 1-to-100,000 or greater should be conditionally approved. 

The FDA’s criteria were established in 1995, “using the most relevant scientific literature at the time,” an agency spokesperson said. Internal follow-up studies in 2011 and 2015 have since validated them as protective of human health, “based on the average wastewater treatment plant.”

Buffer zones used to be based on shellfish bacterial load data gathered by state agencies at aquaculture sites, and meeting these dilution-based standards was not mandatory. Yet in 2015, the FDA successfully lobbied to make its dilution standards enforceable against states in the National Shellfish Sanitation Program. It also added a clause stating that buffer zones should be based on hydrographic modeling of how plants’ treated sewage disperses through receiving waters if states cannot provide sufficient bacterial and viral load data.

The Massachusetts DMF lacked the capacity to gather sufficient data for the FDA, nor did it have the modeling expertise to meet the National Shellfish Sanitation Program buffer zone requirements. The FDA cited Massachusetts as “deficient” in 2016 and 2020 for not having large enough buffer zones. If DMF continued to be found deficient, it risked having all Massachusetts bivalve shellfish dealers (not just oyster dealers) lose access to out-of-state markets — a huge economic hit. 

So in 2021, the state contracted Changsheng Chen, a fisheries oceanography professor at UMass-Dartmouth, to use his hydrodynamic model to develop these buffer zones.

Chen’s model is “world-renowned,” and meets FDA criteria, said Christian Petitpas, DMF’s South Shore shellfish program leader, in a March hearing. Federal agencies use it to model the effects of tides, currents, and other physical forces on objects in coastal waters. 

In October 2023, Chen’s preliminary results showed the state would’ve had to close more than 103,000 acres of shellfish beds in Buzzards Bay to comply with FDA buffer zone standards, including more than five oyster operations in Nasketucket Bay, and one in Apponagansett Bay.

DMF acted quickly, working to close roughly 7,000 acres of beds in New Bedford Harbor and Clark’s Cove within 24 hours of receiving Chen’s results. If DMF had taken no action at all, it again would’ve risked Massachusetts bivalve shellfish dealers losing access to interstate markets. 

“The risk associated with not complying far outweighed the unfortunate consequences of having to act fast,” a DMF official said at a media briefing in March. 

Instead of shutting down all the beds, the state developed an alternative plan, based on its work with a modern wastewater treatment plant in Scituate. 

Its plan prohibits shellfishing in areas surrounding outfalls where there is a ratio of one or more gallons of treated sewage to 300 gallons of receiving water. Areas in which the treated sewage-to-water ratio is 1-to-1,000 or greater would be conditionally approved. 

Fisheries officials presented the plan to the FDA this past winter, and it was enacted in March. Agency leaders said this interim plan will stay in place while they gather viral and bacterial load data from shellfish on Soares’s and Leavitt’s oyster farms over the next year to verify the health risk projected by Chen’s model. They say there have been no cases of reported illness tied to eating local shellfish. 

“We feel there’s justification in not immediately closing them, and giving them the benefit of the doubt while we do additional testing,” Petitpas said.

The FDA did not object to DMF’s approach, though it stands by its existing buffer zone dilution standards in the National Shellfish Sanitation Program, an agency spokesperson said.

Grower pains 

Soares, the state director for Massachusetts, Connecticut, and Rhode Island in the Department of Agriculture’s Rural Development division, says he appreciates the state’s work to keep local oyster growers open — especially amid federal pressure to close them entirely. Still, he feels “a noose is tightening” around his ability to produce oysters. 

DMF already reclassified Soares’s half-acre farm from fully approved to conditionally approved in 2021, given its proximity to a mooring area (a spot where more than 20 boats anchor). This was a response to an FDA-backed precautionary change to the National Shellfish Sanitation Program requirements, and not local viral and bacterial load data. 

Now, shellfishing is prohibited in the areas abutting Soares’ property to the east, because of buffer zone modeling. 

“If you keep going in the direction where precaution rules the day on whether or not you can sell oysters, then it’s going to move in a direction that limits our ability to sell,” he said. 

In 2024, sales for local oyster growers have already been limited by precautionary measures, Leavitt of Blue Stream Shellfish said. 

Even before the March reclassification, Leavitt and Soares both experienced four unrelated emergency closures initiated by DMF, triggered by storms that caused large combined sewer overflows in New Bedford.

Garfield said that DMF started instituting these emergency closures in fully-approved beds in the past couple of years, after several intense storms each produced tens of millions of gallons of combined sewer overflow discharges. 

Leavitt said recent emergency shutdowns, which closed his business for six weeks, have prohibited his company from taking advantage of increased early-season demand for oysters this year. 

Garfield said that climate change continues to bring more frequent intense storms, which are overwhelming “antiquated” combined sewer systems in communities like New Bedford.

He fears that reclassifying these beds as conditionally approved under the buffer zone model means closures will happen more often for local growers, as combined sewer overflows regularly exceed stringent state thresholds.

Garfield also worries that DMF using their buffer zone model to reclassify beds across Buzzards Bay means that one strong storm could knock out production across the region, even though local oysters aren’t getting people sick.

What concerns Leavitt even more is the possibility of an extended closure. The earliest an oyster grower can be reopened after a conditional closure is seven days. And Marine Fisheries must reset the clock in the middle of a closure, if rainfall or combined sewer overflow discharge exceeds benchmarks.

Oyster farms without significant cash on hand can run into trouble meeting operating costs if they cannot sell their product for extended periods.

Next steps 

Garfield, of the Massachusetts Aquaculture Association, says he understands Chen’s model and the state’s need for it. Yet he believes there is a “fundamental missing piece” in the state’s decision to reclassify these shellfish beds: local data that reflects human health risk. 

DMF’s model did not account for viral and bacterial loads in local shellfish and seawater, nor the decay rate of hypothetical contaminants.

Chen declined to comment on the state’s use of his model for shellfish bed reclassifications. He said in an email that it had been refined to meet the requirements of the National Shellfish Sanitation Program. 

Leavitt said he is taking issue with the model’s outputs and his reclassification until DMF’s modeling study undergoes a peer review. 

He added that the state should work with industry to push back on the FDA’s “generic” buffer zone modeling requirements, “which may not be appropriate for our systems.”

Criticism of the National Shellfish Sanitation Program’s modeling requirements — which are “pretty risk-averse” — is fair, Petitpas said. But those are the rules the agency must work within to keep interstate markets open to Massachusetts bivalve shellfish dealers. 

The biological data that DMF will collect this year could show that the model correctly conveys health risk. If so, the agency will have to close wide swaths of Buzzards Bay to shellfishing, including Leavitt’s and Soares’s farms. 

Petitpas added that she is “optimistic” that local data will show fully prohibiting 103,000-plus acres of Buzzards Bay to shellfishing is not necessary, and that DMF, local growers, and the FDA can develop an area-specific plan for local aquaculture.

Email climate and environment reporter Adam Goldstein at agoldstein@newbedfordlight.org.