A rendering of what the area will look like once green infrastructure is implemented, which includes bio-retention infrastructure and planting native vegetation to filter stormwater. Contributed / FB Environmental Associates
Topsham is entering the next phase of its plan to filter out pollution from the Topsham Fair Mall Stream, which includes the installation of a biofiltration system and working with businesses and property owners to implement more environmentally-friendly practices.
The stream surrounds the parking lots and roadways that make up the Topsham Fair Mall property and drains into the Androscoggin River, which flows to Merrymeeting Bay, an important water source for many coastal towns. It was identified as being “impaired for aquatic life” by the Maine Department of Environmental Protection, according to a Watershed Management Plan in 2014, due to high chloride levels washing off the nearby pavement.
The town and its consultant, FB Environmental Associates, who drafted the plan, are pursuing “practices that will improve the water quality and climate resiliency,” Mindee Goodrum, project manager for FB Environmental, told The Forecaster this week. The town plans to install a biofiltration system to filter out pollution before it enters the stream.
Techniques will include retaining roof runoff, directing surface runoff from the parking lot into permeable paving, planting native vegetation to filter stormwater, heated sidewalks to melt snow and ice, using brine rather than salt to melt snow and rain barrels to catch stormwater before it enters the ground.
“The town public works (department) is installing a rain garden near the intersection with Monument Place and Topsham Fair Mall, and have a plan drawn up that gives suggestions,” said Topsham Town Planner Skye Siladi.
This would be designed to better absorb rain runoff, reducing the amount of polluted water that could flow into the stream.
“We’re meeting with contractors and businesses to talk about how they do winter management currently, and working with them to come up with adjustments to their practices if needed,” Goodrum said.
The Topsham Fair Mall Stream drains into the Androscoggin River, which flows to Merrymeeting Bay, an important water source for many coastal towns. Contributed / FB Environmental Associates
One challenge to approaching the issue of water quality is that there is no single point of pollution. Much of it stems from winter salting of the nearby pavement and concrete, which then funnels chloride into the stream, Goodrum said. Unnatural surfaces like asphalt and roofing are considered “impervious cover,” which makes up more than 30% of the Topsham Fair Mall stream watershed.
“The ideal is closer to 8%, so we’re looking to reduce the impervious cover,” said Goodrum, through “strategies that have benefits to the area.”
“Macroinvertebrate diversity isn’t what you want it to be,” she said, which is how the DEP determined this as an area of concern. Macroinvertebrates are aquatic insects vital to the food chain, and their health tends to signify the health of the overall ecosystem, she said.
“Chloride is entering from the groundwater, so there’s a source of chloride into the stream all year long,” said Goodrum. “That’s what’s really the issue for the species that live in the stream.”
The town first began working with FB Environmental Associates to draft the watershed plan in order to determine the best approach to address concerns raised by the DEP. The town’s goal has been to implement this Watershed Management Plan by 2024, and this May the environmental firm released a breakdown of the green infrastructure they plan to install in the area.
“I think a lot of people don’t really realize the stream is there, because it has a forested buffer around it,” Goodrum said.
Last week, the town held a site walk for residents to see the area, understand the issues at hand and present solutions.
In 2022, the town was awarded a roughly $150,000 grant through the Maine DEP Nonpoint Source 319 Program, which will cover this third phase of the plan, with at least two more phases on the horizon. The third phase involves collaborating with public works to install a biofiltration system to treat about 1.5 acres of stormwater, conducting education and outreach on winter management practices, and working with at least two private property owners in the Fair Mall area to install stormwater best management practices on their own properties.
Goodrum encourages nearby private landowners to get involved, as there are still grant funds available for them to do environmental infrastructure for the benefit of the stream.
“It’s a collaborative effort, so it’s been great to work with Topsham and come together to brainstorm how we can improve water quality,” said Goodrum.
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