How gardens could help clean up Puget Sound

A RainWise rain garden in Ballard. Credit: Bob Spencer/Seattle Public Utilities

If Karrie Kohlhaas had her way, everything that’s happening on the block she lives on in Delridge would be a citywide movement: rain gardens instead of grass, bio-swales instead of parking strips and permeable surfaces instead of pavement. Designing a block here and a project there is good, but not good enough she says, because there’s been so much devastation to our waterways. 

“But what would it look like if we started doing this as a citywide kind of movement, where instead of ‘Oh, here’s a cluster here and a project going on in this neighborhood,’ what if every project could include some environmental component to it?” Kohlhaas asks.

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There was a time that Kohlhaas thought that rain gardens were just ponds with lilies. Then she received an email from Stewardship Partners, a non-profit, committed to building 12,000 rain gardens by 2016. Would she like a rain garden built on her front lawn at no cost and could she find neighbors willing to do the same?

She and another neighbor, Tanya Baer, replied immediately. “Within four days we had ten families on our block who were committed to participating in the Stewardship Partners rain garden cluster project.” Stewardship Partners has jump-started rain gardens in Puyallup, Burien, Tacoma and Ballard among others.

Building rain gardens cluster-style with several per block — or as part of the green infrastructure of an entire housing or business complex — is the most effective, says Stewardship Partners' Aaron Clark. That’s where most of the private land is in an urban environment. “On top of that, the environmental impact of clustered rain gardens [is huge]. Rather than ten thousand or twenty thousand gallons of storm water being collected in one place, you multiply that by ten. Then you’re talking about hundreds of gallons of pollution that are no longer going into Puget Sound or, in this case, into Longfellow Creek.”

Two years earlier another neighbor on 25th Avenue in Delridge, Jay Mirro, decided to look for funding to solve the problem of standing pools of water on the block during the rainy season. He applied for funding through the Neighborhood Street Fund. Funding was approved through the Bridging the Gap Levy Citizens Oversight Committee. In the fall SDOT began re-grading the street, adding curbs and new sidewalks. Most importantly to rain garden advocates like Kohlhaas, parking strips will have bio-swales and native plants instead of grass.

Kohlhaas points to large concave trenches. “There will be different layers of sediment and that’s where the bio-swales will go. So the water from the street can come into the rain garden.” 

She wishes there were funding for bio-swales and curb cuts along all of the street's parking strips. There will be two swales on the east side of the street and between six and eight on the west side of the street. The King Conservation District chipped in $25,000 for the nutrient rich soil that makes up a bio-swale, soil that absorbs run-off. Stewardship Partners contributed $2,000 for native plants and the city an additional $1,000.

These kinds of improvement programs aren't easy. Though the city’s storm water code mandates that the Department of Transportation address run-off, many jurisdictions say they just don’t have the money. The state Department of Ecology, responsible for maintaining water quality under the Clean Water Act, faces appeals from some 12 cities and six counties, including King, over new state permits that require them to upgrade storm water pollution standards by August 2013.

Seattle Public Utilities began to tackle the problem of run-off and sewage overflow in 2001 with its so-called “SEA Street” project near Carkeek Park. Intense storms from climate change were overloading the drainage system, causing sewage to overflow into the sound. Ten years later a drainage project in Ballard back-fired because of inadequate soil analysis.

Today SPU is doubling the amount of soil testing and listening more closely to the community. SPU’s Susan Stoltzfus says the utility has presented a new plan to the EPA and Department of Ecology to protect local waterways from both sewage overflows and storm pollution. “We’ll be the first ones in the nation coming up with a way to evaluate relative benefits and risks of stormwater over sewage,” says Stoltzfus.

If regulators agree, other blocks in Delridge may become a green infrastructure testing ground to protect waterways from run-off, even when there’s no sewage problem. What will that look like? More than two bio-swales per block and a lot more low-impact development, according to Stoltzfus. “Because that’s what makes sense; that’s the best decision for Longfellow Creek or any other waterway in the city," she says. "But we have to make a case for that."

When that happens, it will likely be good news for the neighborhood. A homeowner around the corner from Tanya Baer, one of the neighbors who responded immediately to Stewardship Partners offer to build a rain garden, asked if his block was next. Baer says she knows that’s not yet the case. Her block was unique in its ability to pull together to bring both rain gardens and street and sidewalk improvements.

She and her husband feel strongly that basic amenities like sidewalks for pedestrian safety and rain gardens and bio-swales to protect urban waterways from pollution should be standards for all. “I wonder about the inequities of another block that may not be as organized for whatever reason. That’s a random occurrence really," she says. "And so then, are they without amenities that most of Seattle has?” 

Green Acre Radio is brought to you with support from the Human Links Foundation. Engineering by CJ Lazenby. Note: This story has been updated since it first appeared to make corrections.

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