The Nature Conservancy, a conservation organization that works to protect ecologically important lands and waterways, issued a report last week asserting that wastewater from residential septic systems and sewage treatment plants contributes approximately half of the nitrogen pollution found in 25 of 43 areas surveyed within the Peconic Estuary.
Large quantities of nitrogen are leaching from onsite disposal systems into waterways on the South Fork, the report stated, an overabundance of which is blamed for oxygen-depleted water, algal blooms, fin and shellfish kills, and the loss of seagrass and marsh habitat. The areas studied are within the towns of East Hampton, Southampton, Shelter Island, Southold, Brookhaven, and Riverhead.
Fertilizer and atmospheric deposition — the natural accumulation of nitrogen — each account for roughly one-quarter of the nitrogen pollution, the report said. Nitrogen from these sources reaches water bodies through both ground and surface water flow.
“There is no denying that excess nitrogen is the largest threat to Long Island’s beautiful and economically important water bodies,” Nancy Kelley, the executive director of the Nature Conservancy on Long Island, said in a release accompanying the report. The report called on Suffolk and Nassau County officials to act quickly to reduce nitrogen leaching.
Residential septic systems and cesspools, said Chris Clapp, a marine scientist with the Nature Conservancy, “are the majority of the problem. If we don’t address them, we run the risk of giving up our maritime heritage and tourism industry.”
In single-family houses, wastewater from toilets, showers, sinks, and washing machines converge to a single pipe leading to the underground septic tank. The systems are designed so that the effluent — liquid waste discharged from the system — is discharged from the tank into a set of pipes with holes, known as a leach field, through which the effluent is released. It is then filtered by soil or sand.
“The concept was that we lived on a big sandbar and the sand was good at removing pathogens,” Mr. Clapp said of current methods. “Aside from systems near surface water, they’ve done the job okay. But as sea level rises and people build closer to shore, there are many systems that are now tidally influenced: One or two times a month or, in some places, during a storm, the tide comes up, the groundwater rises and floods the septic. When the tide goes out, it takes everything away with it.”
“Most of our septic systems don’t deal with nitrogen,” said Bill Taylor, the town’s waterways management supervisor and an East Hampton Town trustee. “Once you get organic nitrogen in the water system it creates all these algal blooms. We’ve been trying to prevent this for a long time.”
East Hampton Town Supervisor Larry Cantwell pointed to faulty septic systems and “legacy systems around our harbors and bays that were built many years ago before the Health Department and local wetlands laws were created.” The next phase of the town’s wastewater study, he said, will be issued in the fall and focus attention on nitrogen pollution and mitigation strategies. “We’re going to need to find ways to upgrade, relocate, and replace systems that are causing nitrogen loading,” he said.
Modern septic systems, Mr. Clapp said, are essentially “mini wastewater treatment plants.” Such a system “would have a shallow drain field that gets a regular dosing over time of the effluent. You get extra treatment just by moving it closer to the surface. Put them shallow in the ground to take advantage of the microbes in the soil and the potential for surf grass to uptake the nutrients. Between the actual treatment unit and the change in how we disperse the effluent, you can really make substantial changes.”
Replacing septic systems, however, “is not inexpensive,” Mr. Cantwell said. “How you ask an individual to pay for that, or provide assistance to do so, is a challenge.”
The town’s current effort to purchase undeveloped properties in the Lake Montauk watershed using money from the Peconic Bay Region Community Preservation Fund transfer tax, Mr. Cantwell said, is part of a long-term proactive effort to reduce pollution in the lake. “Rather than being faced with that situation where we’re required to approve more cesspools, we can use C.P.F. to avoid that problem on those parcels in the future.”
Mr. Taylor and Mr. Clapp also mentioned the overuse of fertilizers by homeowners, farmers, and for recreational use, such as golf courses. “People have got to understand that anything they put on their lawn winds up in their water,” Mr. Taylor said.
“It would be nice to see the agricultural community embrace some of the voluntary options that they have now to reduce nitrogen,” Mr. Clapp said, such as targeted, efficient use of fertilizer.
Stephanie Forsberg, a town trustee who has a doctorate in marine science, welcomed the Nature Conservancy’s report. “As a county and town, we need to delve deeper into the source of what is causing events in our estuaries such as seasonal, harmful algal blooms,” she wrote in an email.
The trustees, in cooperation with Christopher Gobler of Stony Brook University, have implemented a water-quality monitoring program in trustee-managed waterways. “We plan to look at specific types of nitrogen in the water to see if they are present before, during, or after harmful algal bloom events,” Dr. Forsberg wrote. “By obtaining this data, we hope to work with our fellow constituents and elected officials at the town level and higher to collaborate jurisdictions and work towards fixing the source of what may be setting off these undesired chains of events in our trustee ecosystems.”
The Nature Conservancy report, she wrote, “is a step in the right direction; now we will continue by focusing on water quality and possible nitrogen sources within our town’s watershed.”
The consequences of not acting, Mr. Cantwell said, include more toxic algae blooms and degradation to shellfish and other marine life. “That,” he said, “is too high a price to pay.”