ADDISON COUNTY — How often do you think about what happens to the water that runs off our roofs, roads and sidewalks during a rainstorm?

That water can have a big impact on the surrounding environment, potentially picking up pesticides, bacteria and other pollutants as it flows through storm drains and ditches into nearby waterways. Such polluted runoff is one of the largest threats to clean water in the United States, according to the Environmental Protection Agency.

With that in mind, some property owners are turning to green stormwater infrastructure, or GSI, as a way to reduce stormwater runoff and its water quality impacts.

Green stormwater infrastructure is used to filter and manage stormwater runoff in a way that resembles the natural environment, such as with plants and soil. Examples of the infrastructure include rain gardens, green roofs, bioswales and riparian buffers.

This differs from “gray” or traditional stormwater infrastructure — like gutters, pipes and drains — that collect stormwater as it runs off impervious surfaces and ultimately directs it into a nearby body of water.

“For the most part, (green stormwater infrastructure) is not for you. It’s for your neighbors,” Tim Parsons, landscape horticulturist at Middlebury College, said. “Your own yard is just a small piece of a larger ecosystem that we all collectively maintain. So, if you are slowing down stormwater on your property, you may or may not see direct benefits from that, but your friends and neighbors in low ground, or say on a flood plain, they will see that cost that you’ve helped them upslope.”

At Middlebury College, a lot of the stormwater on campus gets collected by storm drains and directed to a large retention pond near the running track, which then travels through a swale (a broad, shallow channel that helps convey and filter stormwater) that eventually hooks up to the Otter Creek. Parsons noted that the college has a lot of impervious surfaces, including around 16 miles of sidewalks, about 21 acres of parking lots and many roofs.

“We don’t want to see all of this (stormwater runoff) go down to the Otter Creek if we can treat it first,” Parsons said.

The college treats stormwater through various types of GSI, such as a couple of green roofs on campus and a system of collection areas, wet meadows and swales near Davis Family Library.

Another example of GSI sits on the southside of a building called the Axinn Center at Starr Library, which hosts stormwater retention and filtering features. Parsons said the building’s courtyard has been graded and planned to account for the structure’s roof space. So, the land is sloped and graded to collect rainwater that flows off the roof into a swale.

“This (area) was then planted with trees, shrubs and herbaceous plants to use that stormwater as it sits and accumulates,” Parsons explained.

A bioswale in the courtyard collects rainwater that runs off another part of the building’s roof, as well as any overflow from the other swale. A raised storm drain in the area collects water if it gets too full of water.

“I have only seen it do that (in) about two or three really bad storms,” Parsons said.

PROJECTS FOR HOMEOWNERS

The Axinn Center site offers an example of the type of a GSI project that homeowners can take on — but at a smaller scale.

“This, I think for most homes, is still big, but it’s a good idea of what you could do with, say, one tree, three of that shrub, one of this shrub, some tall perennial sunflowers, this and that,” Parsons said.

What other options exist for landowners interested in green stormwater infrastructure? Parsons said he likes the idea of mowing less, though he’d advocate for adopting a “no mow midsummer” approach rather than the typical No Mow May.

“To not mow in May sets you up for a lot more lawn mowing in June, and I don’t actually think you save a lot of time,” he explained. “Whereas if you did mow in May and the first two, three weeks of June and then stop, you probably wouldn’t have to mow again until fall because that’s just the life cycle of grass.

“Think about all of the farms that we are surrounded by. They get most of their hay in first cut, which is in May or the first week or two of June,” Parsons continued. “Then the grass slows down in the heat of the summer, doesn’t need as much maintenance … to have a no mow midsummer, I think that would make a lot more sense, and it would promote good root growth, good soil structure, all the things that you want from plants that you don’t get as well in an average maintained lawn.”

Establishing low-mow or no-mow zones can also help promote wildlife habitat and decrease runoff.

Parsons said property owners could also think about ways to repurpose parts of their lawn they’re not using. That’s something he considers when it comes to the lawns on campus.

“I’m trying to get our lawns down to ones that are used because lawns are still used, they are still good, but perhaps you don’t need all of them,” he said. “There are sections of lawn here that see a lot of use — frisbee games, or they’ll hold classes out on the lawns. There are also lawns that haven’t seen a student foot in 20 years.”

MIDDLEBURY COLLEGE TREATS stormwater on its campus through various types of green stormwater infrastructure, including stormwater retention and filtering features just outside the Axinn Center at Starr Library. A courtyard at the site has been graded and sloped to collect rainwater that flows off the roof into swales, which are broad, shallow channels that help convey and filter stormwater.
Independent photo/Marin Howell

That approach could be scaled down for homeowners, he said.

“You, I’m sure, have lawns that you want to hang out on. You might have lawns that your kids want to play on, but what is actually used and then what could be repurposed to something else, say, trees and shrubs,” Parsons asked.

Peter Norris often comes across green stormwater infrastructure projects in his work with Norris Landscaping and Nursery. He said common projects include rain gardens, swales, and planting more native materials on slopes prone to erosion.

Jill Sarazen is the Green Infrastructure Collaborative Coordinator for the University of Vermont. She offered a couple success stories of GSI installations in the Burlington area.

“In one case the landowner had water in their basement and a dirt parking area eroding, so we installed gutters, permeable pavers in the driveway, two rain barrels and it worked,” she said.

Sarazen also pointed to a three-unit, older home on a steep slope that had issues in its basement.

“We were able to redirect water upslope, capture it and direct it to the side where we put in a permeable walkway, created a swale and dry well with plantings in it to infiltrate the water,” she said.

COSTS AND BENEFITS

Sarazen noted that finding landowners willing to stick through the whole GSI process can be a challenge.

“Usually the most motivated people have erosion or flooded basements on their property,” she said, adding that, “GSI systems can make a difference, but they can’t stop a flood.”

What other costs or challenges might come up in GSI projects?

“Part of it may require a little bit of excavation and some planting, but some of it is just a matter of management, keeping the vegetation or not mowing the lawn near erosion prone areas,” Norris said.

Parsons also noted there’s maintenance that comes with GSI projects.

“It’s not sitting on a lawn mower, it’s coming down to pull weeds,” he explained. “This is still a managed landscape. It’s just a different type of management, but it is still work.”

He said that at the Axinn Center site the amount of maintenance required has decreased over time.

“This is certainly not as much work as it was in the first two, three years to get established,” he said. “We probably come through here once or twice a year to pull weeds … The first couple of years to get a new planting established is quite a bit of work.”

In weighing the costs of different projects, Parsons noted it depends on what a landowner’s end goal is.

“If your end goal is to have your yard look like a golf course, you will mow,” he said. “If your goal is to help treat stormwater and increase biodiversity, your lawn will not be as effective as a bioswale is, but that comes at a cost of more physical maintenance.”

As for the benefits, GSI can provide aesthetic elements in communities and habitats and food for wildlife, according to the Rain Garden Manual for Vermont and the Lake Champlain Basin. Some GSI practices, such as planting larger shrubs and trees, can also provide shading and improved air quality.

The EPA outlines several other economic, social and environmental benefits of green stormwater infrastructure, including reducing localized flooding and improving water quality.

Parsons noted there are also nontangible benefits of GSI to consider, such as increased biodiversity.

“Not just in terms of plants, but now think in terms of the insects that live on these plants that then they turn into a food source for birds,” he said. “As we live in a very built world, a long ways from the woods, how can we bring smaller spots like (GSI at the Axinn Center) to increase biodiversity to help connect our real urban spaces to more natural ecosystems?”

Matt Witten contributed reporting to this story.