Canton streams have issues with bacteria, report finds

Streams in Canton experienced an increase in bacteria levels for the 2022 season over data from the last several years, according to a report from the Neponset River Watershed Association (NepRWA). None of the eight sites sampled by NepRWA met MassDEP swimming standards for E. coli bacteria across all six sampling events, although the two sites on the East Branch and mainstem of the Neponset River were the closest to reaching swimmable quality.

Pecunit Brook experienced the greatest increase in bacteria levels over prior years. “Unfortunately, these tributaries of the Neponset River continue to have major problems with E. coli levels,” said Ian Cooke, NepRWA’s executive director. “This is dangerous because E. coli presence provides evidence of fecal contamination that could make people sick if they come into contact with the water during recreation.”

Stormwater runoff carries high levels of E. coli when polluted with pet waste or other contaminants. Community members can help reduce these levels by cleaning up dog waste properly and disposing of it in the trash rather than leaving it on sidewalks, roadways, or lawns. Some pet owners mistakenly dispose of pet waste bags in the storm drains along roadways, thinking that these lead to wastewater treatment areas. However, in Canton and throughout the Neponset River Watershed, these drains lead directly to the nearest stream with no treatment.

People can also create opportunities for runoff to infiltrate into the ground by planting rain gardens, installing rain barrels, or designing bioswales. “The Canton Sustainability Committee has partnered with The Great American Rain Barrel Company to offer rain barrels to Canton residents at a reduced cost,” noted Kristine Meaney, Canton’s stormwater manager. “Interested residents can visit the committee’s website for more information.”

According to Canton Conservation Agent Regen Milani, there are currently 1,525 dogs licensed with the Town Clerk’s Office as of June 2023, and each of those dogs produces an average of roughly three quarters of a pound of waste per day based on data from the U.S. EPA. “That amounts to over 417,000 pounds of dog waste per year in Canton,” Milani said. “If it is not picked up and sent to the incinerator, it is going directly into Canton’s brooks and ponds. Dog waste is not fertilizer like cow manure. Dogs consume high amounts of protein, and their waste is highly acidic. It is harmful to lawn grass and loaded with bacteria.”

While the chore of bagging and properly disposing of one’s pet waste might be irritating, Milani said it is essential to being a good community member. Even on private property, she stressed that stormwater runoff can flow off the lawn and carry pet waste into the street drainage system or an adjacent waterbody or wetland.

However, stormwater may not be the only concern. Bacteria levels in Pecunit and Massapoag brooks were high even in dry weather as early as May. Because bacteria spikes during dry weather are less likely to be caused by pet waste and runoff, this suggests ongoing issues with sewage infiltration to these particular streams. Meaney said the town of Canton is currently in the process of evaluating its storm drainage system using the sample data provided by NepRWA along with its own sampling data.

The NepRWA report also describes water quality parameters important for wildlife, including phosphorus and dissolved oxygen. In comparison to 2020, phosphorus levels from Pequit Brook, just upstream of Reservoir Pond, have fallen but remain at the state-recommended level for water entering lakes or reservoirs. Beaver Meadow and Massapoag brooks just upstream of Bolivar and Forge ponds, respectively, are similarly close to the highest recommended level.

“Phosphorus is necessary for plant growth, but naturally is found in very low concentrations,” explained Dr. Sean McCanty, NepRWA’s river restoration director. “Because of this, it is often the ‘limiting’ resource in the freshwater environment. We tend to see algal growth when phosphorus concentrations increase — because all the other required nutrients are likely already there.”

“Aside from the aesthetic factor, the real problem is that when these extra plants and algae eventually die, they get eaten by bacteria,” McCanty added. “This process consumes oxygen; in extreme circumstances the dissolved oxygen levels get so low that fish and other animals die.”

There are three sites in Canton — on Beaver Meadow, Pequit and Ponkapoag brooks — where phosphorus levels were more correlated with decreases in oxygen, suggesting eutrophication may be an issue for these areas. Meaney said the town has recently installed stormwater controls at the Earl Newhouse Waterfront, which can help remove nutrients and contaminants before water enters Reservoir Pond and Pequit Brook.

In 2022, dissolved oxygen was a major problem at both Pequit and Beaver Meadow brooks, with water levels frequently dropping below 3 mg/L, which can make large sections of the water uninhabitable by fish and other aquatic life. McCanty said the persistently low levels of oxygen seen at some of these sites is a significant concern, especially when combined with the impacts caused by drought. “We hope in the future to look into whether improvements can be made to stream shading, maintaining good water flow, and find ways to prevent decaying material from sucking the oxygen out of these sites,” he said.

The water quality monitoring program that collects this data is part of a larger watershed restoration effort. Throughout the Neponset River Watershed, efforts to improve water quality, restore river and salt marsh habitat, and reconnect the streams to allow fish passage are all underway. “All of these issues are connected,” said McCanty. “Removing old dams helps prepare our communities for climate change, improves fish passage and dissolved oxygen levels, and can limit the amount of algae overgrowth. Replanting along the riverbank helps filter storm runoff and stabilize the banks, improving water quality for fishing, boating and swimming.”

The Neponset River Watershed Association, with headquarters in Canton, is an environmental nonprofit that publishes an annual report on the health of the Neponset River and various local streams. The water quality data used in the report is collected as part of the NepRWA’s volunteer-based Community Water Monitoring Network (CWMN) program, which collects samples monthly from May to October to test for constituents that impact safety for recreation and wildlife.

For the full water quality report, visit neponset.org/town-water-quality-reports.

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