Study Suggests Boaters May Be Releasing Septic Waste in Sag Harbor

Dr. Christopher Gobler speaking before the Harbor Committee on Feb. 6. Peter Boody photo

A two-year study of water quality in Sag Harbor found that it is good overall but that nitrogen loading, mostly from conventional cesspools and septic tanks leaching untreated waste into groundwater, is promoting algae growth including a rust tide in the summer.

The study also found that fecal bacteria — some of it from human waste, possibly including boaters illegally releasing effluent — is an issue in some locations.

While waste from dogs and small mammals was present at most of the six sites around Sag Harbor where water was tested, there’s a “very strong human signal” in the DNA of fecal bacteria found in the inner harbor and Sag Harbor Cove, Dr. Christopher Gobler reported on February 6, when he presented highlights of his study to the Harbor Committee and a packed audience in the Municipal Building.

Private donors paid most of the $80,000 tab for the study, including the Sag Harbor Partnership and the Sag Harbor Yacht Club and Yacht Yard. Sag Harbor Village and the East Hampton and Southampton Town Trustees also contributed. Mary Ann Eddy, the chair of the Harbor Committee, which regulates activities on the water and within 100 feet of it, helped coordinate the project.

Dr. Gobler, a professor at the SUNY School of Marine and Atmospheric Sciences in Stony Brook, and his researchers set up sensors and took regular samples at six sites around Sag Harbor’s waters from April to October in 2018 and 2019. They tested for multiple indicators of water quality, such as nitrogen and oxygen content.

In addition to his presentation last week, he has prepared a 90-page report on the project titled “Assessment of Water Quality in Marine Waters Surrounding Sag Harbor Village, 2018-2019.”

In his presentation, Dr. Gobler said that septic systems and cesspools could not be the source of fecal bacteria in local waters because the bacteria “can’t travel in groundwater,” unless the septic systems are actually submerged. In that case, they could be directly passing fecal bacteria into ground and surface waters.

The municipal sewage treatment plant has as high level of waste treatment, including ultraviolet light to kill bacteria and is the best option for the treatment of human waste, Dr. Gobler noted. But it has been cited by the state DEC following breakdowns in the past for “violations in fecal coliform” in its effluent, so it could be a contributing source for the bacteria found in the inner harbor and Upper Sag Harbor Cove, Dr. Gobler said.

Sag Harbor Cove contained the next-highest level of human fecal bacteria, Dr. Gobler reported, even though it is well removed from the treatment plant. It has nearby marina activity, he noted, adding that he has seen the same rise in human waste bacteria when sampling water closer to marinas in Three Mile Harbor in East Hampton.

“Some finer scale sampling could resolve the relative importance of each,” Dr. Gobler said, referring to boat traffic and the sewage treatment plant. With samples from more locations, he added, his researchers could correlate high bacteria counts to nearby vessel concentrations.

“I cannot say from my study it is the boats,” Dr. Gobler said when asked by audience member Steve Williams, president of the Azurest Property Owners Association, if “boats are discharging in our harbor.”

“It could be the boats; there are some signs it is the boats,” Dr. Gobler said. “But there is the sewage treatment plant … and there have been occasions when it has had high levels” of fecal bacteria in its effluent.

“There’s only a small human signal” in the waters off Havens Beach, the village’s public swimming facility, Dr. Gobler said, but he called the presence of fecal coliform there from other sources, including dogs and small mammals, the most problematic of all six sites tested around Sag Harbor water because people swim and shellfish there.

Nitrogen loading exceeded the Peconic Estuary Program’s recommended maximum in the inner harbor inside the breakwater, and in Otter Pond on two occasions, Dr. Gobler reported. Water clarity declined in the summer months and chlorophyll levels, “a proxy for total algae,” peaked. Oxygen levels fell to low levels in Sag Harbor Cove and Otter Pond.

One alga, rust tide or cochlodinium, which kills fish, reached high levels in Sag Harbor Cove and the Upper Cove and in the harbor itself in 2019, but “they weren’t what I’d call Biblical levels,” Dr. Gobler said.

Summing up Dr. Gobler’s report in response to an emailed request for comment, Ms. Eddy wrote that “going forward …. further study is needed at the Inner Harbor including the STP [sewage treatment plant] to determine the source(s) of human pathogens.”

She wrote that the public and local officials should “accept that we have a nitrogen problem” coming from on-site septic systems and she wondered if properties close to shorelines should be required to install innovative/alternative septic systems that actively reduce nitrogen levels, unlike conventional systems.

She said a meeting with Mayor Kathleen Mulcahy — who attended the presentation and said she wanted to see the study project continued — would take place this week “to discuss the report and steps going forward this week.”

Dr. Gobler called the study “very complex … the most complex I’ve ever had,” and thanked Ms. Eddy and the project sponsors. “It took a village to pull off this study,” he said.