The bioswales are planted with species that are hardy and beautiful, like this snowberry. (Photo by Ann Dornfeld)
Some cities are looking at taking away parking
on residential streets and replacing it with shallow
ditches full of native plants that filter stormwater.
It’s a way to reduce the polluted runoff that flows
into lakes, rivers and the ocean. As Ann Dornfeld
reports, not everyone is thrilled with the idea:
Transcript
Some cities are looking at taking away parking
on residential streets and replacing it with shallow
ditches full of native plants that filter stormwater.
It’s a way to reduce the polluted runoff that flows
into lakes, rivers and the ocean. As Ann Dornfeld
reports, not everyone is thrilled with the idea:
We’re walking down a winding lane lined with maple trees, tall, dry grasses and
evergreens. Bright white snowberries dot the dark branches. It feels like a walk
in the country. But we’re actually admiring a big-city sewer system.
This little valley – a sort of shallow ditch – is called a “bioswale.” Its plants filter
out pollutants that run off the street. And special, thirsty soil helps the water
absorb into the earth. Sections of the street are narrowed to make room for the
bioswales, so some parking along the street is lost. But houses without
driveways get two parking spaces between the swales.
The bioswales have thick layers of native grasses, shrubs and other plants. It’s
kind of a wild, natural look. Debbie Anderson lives on a nearby street. As she
walks by the bioswale she says to her it just looks messy.
“We think it looked nice when it was first built, but it hasn’t continued to
look good, I don’t think. We moved out here because there was no
sidewalks and the streets were wide open and we like that. Lots of parking,
we can have lots of company. This way you can have, what, two people
that can come? That’s it! No. I don’t want it.”
That’s a pretty familiar argument to Bob Spencer. He’s with the City of Seattle’s
Public Utilities office.
“The big thing is the lack of parking. People really get into using these
street right-of-way shoulders as their personal parking spots.”
But not everybody thinks parking spots are more important than doing something
to reduce water pollution. Spencer says the neighbors on this street actually
competed with other blocks to get these bioswales. It’s free landscaping – and
the city even worked with each homeowner to choose plants that would blend
with their existing garden.
Spencer says the city’s traditional method of dealing with stormwater has washed
contaminants into a nearby creek.
“Well, in the surrounding streets around here, we have what’s called ‘gutter
and ditch’ drainage. And what happens is the water runs off the property
and the impervious streets and rooftops. And it enters a ditch and then
goes pell-mell screaming down to our local salmon-bearing creek, Piper’s
Creek.”
It’s not just Seattle’s creeks that are flooded with runoff. Untreated rainwater
flows straight into lakes and the ocean, polluting them. Cities across the country
are looking for ways to deal with toxic runoff like that.
Spencer says Seattle is pioneering
large-scale natural drainage. In other words, the rain is allowed to drain like it
does in the wilderness. The plant roots slow the water so it can absorb into the
earth. That helps prevent flooding. Pollutants like heavy metals, pesticides
and fertilizers are trapped in the soil, and some of them are broken down in these bioswales.
“So we’ve got a little bit more like a forested system in that we have a duff
layer that acts as a sponge.”
Spencer says the city hasn’t tested the water quality of the runoff that eventually
enters the creek. But he says the runoff has been slowed to a trickle.
“It infiltrates and holds and keeps here 99% of that runoff. So that’s a
pretty large flush of water that’s not entering the creek with this system.”
Officials in Seattle’s city government like the green look of the bioswales. And
they help the city meet federal pollution guidelines. City Council President
Richard Conlin says over the course of three bioswale projects, the city has been
able to lower the cost to about the same as conventional stormwater treatment.
Seattle’s newest bioswale system will be at the foot of Capitol Hill. That’s where
seemingly half of the city’s young people live, in blocks full of apartments,
nightclubs and parking lots.
“It’s actually the densest urban neighborhood west of Minneapolis and
north of San Francisco. So it has a lot of impervious surface.”
Stormwater from Capitol Hill rushes off the hard surfaces and down to a lake. So
the city is taking advantage of new development at the bottom of the hill. It’s
planning to filter the runoff through bioswales before it pollutes the lake.
“And once we’ve done that, I think we’re pretty much ready to say this is
the standard from now on.”
Conlin says the city will likely install bioswales in all new developments, and on
streets where the most runoff enters waterways.
He says cities around the country are contacting Seattle to find out how to install
bioswales of their own.
For the Environment Report, I’m Ann Dornfeld.
