Antiquated sewer systems continue to force shellfishing closures in Dartmouth, and while little can be done, efforts are underway to find alternative shellfishing locations.

While sewer discharge and nitrogen pollution have routinely closed shell fishing in the waters of Apponagansett Bay — a joint state and local effort is looking upstream at the Slocums and Little Rivers for future shellfish harvesting.

The sewer discharge occurs when heavy rains overload the sewer systems of New Bedford in events known as “combined sewer overflows,” or CSOs.

When the overflow occurs, raw untreated sewage flows through a range of 27 overflow pipes that empty directly into Buzzards Bay. Natural tides and currents then move the contaminated water into Dartmouth’s waters, resulting in poor water quality and the subsequent closing of shell beds, said Dartmouth Harbor Master Steve Melo.

“The sewer overflow didn't happen overnight. The state did change regulations, which made the existing conditions scrutinized more and made it more front and center. But it's not going to be an overnight solution. We can't just shut them down,” Melo said.

After the overflow events, the state requires Dartmouth to shut down all harvesting, including — aquaculture farms like Padanaram Oyster Farm — for 21 days. On the seventh day, samples can be processed to find out the exact impact from the discharged sewage. If samples are in a safe threshold, the re-opening process can be quickened, said Melo.

In Dartmouth, regulations for recreational and commercial harvesting of oysters, soft-shell clams, quahogs and mussels can be found on the “Dartmouth Shellfishing Abstract” chart on the town website.

Last August, Dartmouth saw an increase in closures following stricter guidelines from the Division of Marine Fisheries and the Federal Food and Drug Administration. Since then, more vigilant regulation — and poor water quality — has increasingly led to more closures on the bay, Melo said.

Growing areas are classified based on water quality conditions and state-surveys of pollution sources. To ensure shellfish are safe-to-eat, the state classifies areas from approved to prohibited. In Dartmouth, the state Division of Marine Fisheries has designated nine shellfish growing areas.

While few options are available to stop the combined sewer overflows, Melo said a joint effort is underway to open the Slocums and Little Rivers for new shellfishing locations that are far from the sewage overflow issues — which all are out of Dartmouth’s control.

Melo is working with the Division of Marine Fisheries and the Dartmouth Public Health Director to collect more water quality data on the Slocums river. Efforts to collect data began on the Slocums a year ago, and he said they are seeing promising results a year into the five year re-opening strategy.

“There’s some promising preliminary results. It’s a long process. We can't short circuit the process, but we're making the right moves and the efforts that are required to get that reopened to some degree,” Melo said of the Slocums river.

Terry O’Neil, senior shellfish biologist at the Division of Marine Fisheries, has been taking samples from the Slocums River since last year. He’s working with the town to examine the Slocums for future shellfishing opportunities — which has been closed for years due to poor water quality.

“It looks pretty promising for a potential future winter-time opening to shellfishing. I do need to get quite a bit more data, certainly another winter's worth of data, so all winter I'll be in there next year, sampling it heavily,” said O’Neil. “If that turns out favorably, then that could be another option for at least recreational activity.”

Melo said the most promising alternatives lie in areas that are far away from where combined sewer overflow events can occur, or, far from the coast. Once headway is made on the Slocums, he said they plan to conduct similar efforts on the Little River.

Naomi Rappaport, a Dartmouth resident and recreational shellfisher, said she has seen the drop in shellfishing quality in Apponagansett Bay over recent years.

“Three or four years ago, when I would go pick oysters, I would spend all my time looking for the best oysters that were the easiest to open. Now I spend most of my time looking for oysters that are alive,” Rappaport said.

Melo said Dartmouth does not track data on how many days the beds have been closed, and commercial shellfishing has grown to become a rarity in the area.

The Division of Marine Fisheries plays a pivotal role in water quality testing. They collect, test and report the important water quality data that is used to both close and re-open beds.

Matt Camisa, the New Bedford regional shellfish supervisor at the Division of Marine Fisheries, oversees the classification of shell beds, and said the combined sewer overflows are the largest threat to water quality and shellfishing.

“That's the big ticket item for water quality issues for us on almost a weekly basis, and also subsequent testing and everything that we can possibly do to minimize the closures and get it back open as fast as we can,” Camisa said.

O’Neil said solutions to poor water quality are slim as combined sewer overflow events continue.

“As long as those CSOs are flowing at the volumes and concentrations that they are, there really is not a whole heck-of-a lot we can do. We are somewhat bound to run these dilution calculators and close accordingly,” O’Neil said.

For Melo, the tradition of shellfishing in Dartmouth is personal. As alternatives are sought, he hopes to see shellfishing make a return to the local waters he grew up searching for oysters in.

“We're not just going to throw in the towel or walk away from what is a historic tradition in the town of Dartmouth,” said Melo.

Residents can find the most recent shellfishing closure information on the Shellfish and Aquaculture Regulations page on the town website.