The water quality in Little Pond is showing improvement since the surrounding homes were hooked to town sewer four years ago, and after a $40 million investment to taxpayers.
The town has been monitoring the pond for the last three years to measure nitrogen levels. The average of the data collected at the 46 locations on various dates indicates a downward trend in the amount of nitrogen over time, with one well in particular showing promising results.
“The fact that the dissolved inorganic nitrogen is at 3.2 milligrams per liter is suggestive of a steady decline,” said Kenneth H. Foreman, a member of the Falmouth Water Quality Management Committee and a scientist at Marine Biological Laboratory.
The pond is Falmouth’s most-polluted estuary, having been flanked by housing developments on hundreds of small lots with cesspools beginning in the 1950s. Excess nitrogen from the septic systems had been fueling plant growth that depletes the water of oxygen. The goal of the Little Pond Sewer Project was to stop the nitrogen flow from the lower part of the Little Pond watershed into the estuary as the only way to restore water quality.
Dr. Foreman spearheaded the monitoring program by placing a network of wells at various locations and depths around the shoreline to monitor groundwater. The concentration of dissolved inorganic nitrogen (DIN is ammonia, nitrate and nitrite) was measured at approximately 46 points between 2016 and 2018.
Little Pond Well Number 3 started at 9.5 milligrams per liter of nitrogen in 2016 and decreased to 6.7 in 2017. It was tested twice in 2018, with declining results of 5 and 3.2. The standard for drinking water is 10 milligrams per liter.
“We started out very close to exceeding safe drinking water standards and now we see results suggesting positive change,” Dr. Foreman said.
How long a full recovery will take is unknown, Dr. Foreman said. The sediments and decomposition that occur when eelgrass dies will slow down recovery. As it decomposes it will release and burn off organic matter. But for now, a “decline in nitrogen in the groundwater by reducing the cesspools seeping into the pond is a great first indicator,” he said.
Full recovery is not expected to occur with sewering alone, but it is expected to remove 83 percent of the total nitrogen load of that pond, said Kristen Rathjen, a technical consultant for Science Wares, Inc.
“There will still be nitrogen in groundwater from other sources like lawn fertilizers or Title V septics farther up in the watershed that have not been recharged,” she said.
Water Quality Management Committee board member Eric T. Turkington expressed the importance of monitoring the pond. “It is really important after spending $40 million sewering the water body. We want to know the results of that effort,” he said.
Students in the Semester in Environmental Science program that Dr. Foreman directs at Marine Biological Laboratory placed the wells and took the samples. As much as he praised the students’ work, he said he would like to see more testing done on a more-consistent basis, which cannot occur with students here for a limited time. He is applying for grants to pay for a more-robust monitoring program.
“If we’re talking about future sewer projects, we need to justify further expenditures and keeping track,” he said.