By Ibby Caputo
Dec. 5, 2011
BOSTON — The intersection of five busy streets in Dorchester seems like an unlikely place for a garden. But in Peabody Square near the Ashmont T station, if you look behind the clock tower, you’ll see what the City of Boston planted: a rain garden.
What was once a lawn in no-man’s-land is now a garden and a gravel trench. The garden is planted with native trees, shrubs and flowers in a ditch. Rainwater flows into this ditch and is absorbed into the ground, then taken up by the plants.
That is what makes this garden special. It’s a utilitarian use of space. It looks like a garden, but it is actually a storm water management system.
How nature manages rain
“Rain gardens are a really interesting, simple way to think about managing rain in an urban environment,” said Kate Bowditch, the director of projects at the Charles River Watershed Association, the nonprofit that consulted on the design of Boston’s first rain garden. “It’s really the way nature manages rain and we’re just replicating it in an urban environment.”
Rain gardens are designed to treat the first inch of rain, which carries the most pollutants.
When rainwater comes into the garden, it soaks down through the soil, Bowditch explained. An active microbial mix in the soil breaks down the pollutants and eats up the nutrients; the plants drink up a lot of the water and nutrients as well. The rest of the water then percolates through the soil into the groundwater.
Less storm runoff = cleaner rivers
The purpose of this green infrastructure technique is to reduce flooding and improve water quality. Both are problems created by what is called “gray” infrastructure: concrete, pipes and pavement.
“It’s hard to live in a city with no pavement and you can’t live in a city with no buildings,” said Bowditch. “But the buildings and the pavement have really cut off the water from the ground, so we have all this rainwater falling out of the sky, landing on all of these paved areas and rooftops, and where’s it going to go? It has to go somewhere.”
Bowditch said that most storm water currently drains into pipes and shoots straight out to local bodies of water such as the Charles River. This causes water quality problems and increases the risk of flooding.
Rainwater runoff from Peabody Square drains into the Neponset River, which is on a list of polluted waters compiled by the Environmental Protection Agency.
The Peabody Square project is part of a larger initiative paid for by federal stimulus dollars to improve 15 intersections along Dorchester Avenue. While only a few of the reconfigured intersections will include rain gardens, the Peabody Square project was specifically designed to address water quality.
“There’s a lot of really, really interesting new techniques and technologies that are evolving that allow us to make the urban environment function much more like a natural environment, particularly in terms of water,” said Bowditch.
City officials said they hoped to learn from the Peabody Square pilot and include a green dimension in all future projects, including the redesign of Audubon Circle and Central Square in East Boston.
Subscribe to WGBH Science Emails