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Stopping Stormwater (With Trees and Flowers)

By Joshua Brown Article published June 29, 2006

garden
Mark Babson plants Black-eyed Susans as part of a new "bioretention" rain garden, installed near the Votey parking lot to help filter toxins and slow stormwater. (Photo: Joshua Brown)

Black-eyed Susan, silver maple, grey birch, Indian grass, speckled alder: these may not seem the typical tools of an engineer. But on an overcast Friday afternoon, Maeve McBride, a doctoral candidate in civil and environmental engineering, puts them to elegant use.

“These plants don’t mind getting their feet wet; some of them are true wetland species,” McBride says, standing in an oval of raw soil about the size of a small swimming pool at the bottom of the Votey parking lot near Colchester Avenue. Above her, an acre of pavement starts to darken with drizzle. Soon, rainwater will start to run across the pavement toward the dirt patch.

Behind her, 12 volunteers plant the saplings and flowers in an earthen berm that forms a small barrier along the edge of the avenue and access road.

“Right now, most of the rain ends up running down this asphalt swale,” she says, pointing to a paved trough along the entrance to the parking lot. “But once these plants really take root, we’ll dam it off and force the water in here.”

If it works, this plot of former lawn will bloom to become a “bio-retention” rain garden, catching the parking lot’s runoff: a watery brew that includes sand, oil, heavy metals, and the occasional dog dropping. Divided into two cells, like pools on a gentle waterfall, the garden will filter toxins, trap sediments and slow stormwater. This mimics what happens in a natural landscape, allowing the water to be reabsorbed by the earth — instead of rushing headlong over impervious pavement, carrying a load of pollution into Lake Champlain.

Plant power
The maples and grasses and flowers she has selected, simply by being plants, are a marvel of ecological efficiency: they assimilate waste, sponge up water, and hold the soil barrier in place while the rain ponds behind it.

This garden is a small-scale example of ecological engineering — an area of emphasis in UVM’s School of Engineering and Mathematical Sciences, led by Dean Domenico Grasso, who also serves as the editor of the journal Environmental Engineering Science. The basic idea: solve problems using low-cost natural systems near the location where they originate—instead of relying on big, expensive (and often less effective) fixes farther downstream. In this case, downstream is the Winooski River.

“This does reduce the ecological footprint of the university and in a small way protects the lake,” McBride says, “but it also is a demonstration project for outreach and education about the problems with stormwater. We’ll put a sign up here. I’d like to see more of these gardens across campus.”

While there is a detention pond on Riverside Avenue that receives stormwater from a large area, including the Votey and Mansfield lots, it still allows pollution and excess water volume to pass into the lake, especially during big storms. A series of rain gardens could be an important supplement to the existing stormwater system, which in many areas of Burlington is no more than a pipe or stream straight into the harbor.

Wide benefits
Designed and lead by McBride, the garden project is an effort of UVM’s student chapter of the American Water Resources Association (see UVM AWRA Projects for more information), and her students in CE295, “Water Resources Engineering,” plus numerous other supporters and volunteers, including Mark Babson ’06.

“I volunteered yesterday and today to help out,” he says, looking up from his task of taking flower plugs out of a tray. As an undergraduate he studied constructed wetlands with John Todd, an expert in ecological water systems who teaches in UVM’s Rubenstein School of Environment and Natural Resources. “I did a lot of reading, and now it’s great to actually get it going, not just do the design. This is some hands-on, in-the-dirt work that will make a difference,” he says — and then starts digging again.

“One of the best things about this project is that it brings together academics and operations,” says Gioia Thompson, coordinator of the UVM Environmental Council that provided two small grants to fund a site plan and purchase the plants and materials. “It helps everyone. Operations and grounds get educated along with the students.”

One student moving from the theoretical to the practical is Dani Newcomb, a graduate student in aquatic ecology, who took McBride’s water engineering course. “This is a practical application of the things we were learning about in class,” she says, spreading mulch around a pale green seedling. “I have no idea what this plant is, but I’ll go find out.”