‘Rain Gardens’ Turn Backyards Into Water Treatment Facilities, Benefiting Marine Life

by  Ben Adlin


Seattle’s frequent rainfall is responsible for much of the region’s natural beauty, from old-growth forests to the creeks and rivers that flow into Puget Sound and the Salish Sea. But rain can also be catastrophic to area ecosystems. When precipitation falls on roofs, roads, and other hard surfaces, it sweeps pollutants like heavy metals directly into local waterways, disrupting marine environments and devastating wildlife.

Consider salmon, long a mainstay of the region’s ecology and culture: Last year, researchers in the state determined that stormwater runoff, which flushes tire particles from roadways into urban streams, kills more than half of all returning Coho salmon before they can spawn.

One of the best ways of curbing the problem is so simple that just about anyone with a yard can do it. By installing landscaping meant to capture and filter rainwater, commonly known as a “rain garden,” outdoor spaces can be transformed into tiny water treatment facilities.

Need even more of an incentive? Rain gardens can also help prevent basement flooding during heavy rains and save homeowners money on outdoor water costs.

Two programs in Seattle and King County are making rain gardens more affordable than ever. Aimed at encouraging more homeowners and businesses to convert their outdoor spaces and help undo damage wrought by decades of development, the programs offer funding to offset the cost of installing a rain garden, usually covering most or all of the total expenses.

photo of people doing landscape work in front of a house
A rain garden work party (photo: Stewardship Partners).

“We need more rain gardens in the community,” said Aaron Clark, director of strategic partnerships at Stewardship Partners, a local nonprofit that’s working to sign people up for the new programs through its new RainChangers campaign. “If we want a healthy Puget Sound for people and animals,” Clark said, “we’re going to need more of this green infrastructure.”

RainChangers aims to bring attention to two programs that offer thousands of dollars to fund installation costs for residential rain gardens and other water catchment projects. RainWise Rebates, operated by Seattle Public Utilities and the King County Wastewater Treatment Division, reimburses homeowners for costs associated with professional installation of rain gardens in the city of Seattle. A separate initiative, King County GSI Mini Grants, provides money up front for people to hire a contractor or install a rain garden on their own.

The mini grants, funded by King County and administered by Stewardship Partners, provide up to $1,500 in funding to homeowners and businesses, with low-income people and nonprofits eligible for up to three times that — $4,500. The grants are available to anyone in the county who doesn’t qualify for the RainWise program, which targets areas that are particularly susceptible to runoff and offers rebates of about $4,000 on average, Clark said.

Funding from the programs covers about 80% of the costs for most projects, according to Clark, although in some cases it can cover the full amount, especially if people are willing to shop around among contractors. Projects can also be scaled up or down based on budget.

Similar programs are also up and running outside King County.

Rain gardens aren’t the only improvements that help mitigate the consequences of heavy rainfall. The programs also provide free or low-cost cisterns — essentially giant rain barrels — that capture rainwater from roofs and other structures, then either release it slowly or save it for use on a lawn or garden.

rain garden image

Both programs also offer troves of free online resources, including online webinars, how-to guides, a free gardening hotline with multilingual service, and more. Stewardship Partners and RainWise also organize regular educational and volunteer events.

Clark himself has installed a rain garden and two cisterns at his View Ridge home and said he now uses “essentially zero water” for his yard and other landscaping. He’s calculated that “10,000 gallons of runoff every year will be soaking into my property and getting cleaned up” instead of carrying debris and pollution into Puget Sound.

Barron Peper, an architect who lives on Beacon Hill, recently took advantage of a mini grant to install an 800-gallon rain cistern and remove a concrete driveway from his yard to allow rainwater to be absorbed into ground. The cistern, which collects water from his roof, filled up after just a few days of rainfall, he said, and now provides more than enough water to care for other plants in the yard.

While Peper hasn’t installed a rain garden — the grant he received wouldn’t have covered both projects, and he only recently moved into his house and didn’t feel prepared to install a rain garden at the time — he says he’s sold on their benefits.

“Rain gardens are just an incredible tool for creating a small, diverse landscape in something as small as your backyard,” he said. “It invites in the opportunity to hold and retain water, which invites in a whole different mess of species and plant varieties.”

While the programs are only open to landowners, Clark said he’s seen renters successfully work with landlords to coordinate on projects. In West Seattle, for example, resident organizers installed water catchment cisterns at Duwamish Cohousing, which are expected to prevent flooding and help keep polluted stormwater out of the nearby Duwamish River.

“We’re trying to figure out more tools that folks that are renting and living in transitional housing can engage in,” Clark said. 

Local horticulture and environmental experts told the Emerald that rain gardens and cisterns are generally low-maintenance projects that can serve as a frontline defense against environmental contamination and help better manage the region’s water supply.

“It definitely makes a difference,” said Sarah Skamser, a faculty member at South Seattle College’s landscape horticulture program. When it comes to runoff from heavy rains, “What you want to do is slow it, spread it, and sink it,” she said. Which is precisely how rain gardens and cisterns function: They smooth the sharp peaks and valleys of rainfall over time, capturing and steadily releasing water back into the environment.

“One of the main parts of permaculture is any force that comes to your site — which is water or sun or heat or wind or whatever — you want to use it as best you can before it leaves, because they’re transient,” Skamser explained. “What a rain garden does is it can direct water to what you’re growing, and then you use what falls on your site without having to supplement the water.”

Beyond toxic pollution such as herbicides or heavy metals, rain also washes away soil and sends literal tons of silt into creeks, streams, and stormwater drains. “Look at Elliot Bay when it rains,” Skamser pointed to as one example. “It’s all brown.”

A worse problem is the sewage that stormwater can bring to waterways such as the Duwamish River, Lake Washington, Lake Union, and Puget Sound. In some of Seattle’s older neighborhoods, stormwater and sewage are carried in a single pipe. In times of light rain, the pipe brings the combined mixture to a wastewater treatment plant. But during storms, heavy rains fill those pipes, and the combined systems overflow into nearby bodies of water.

So-called combined sewer overflows are actually a main driver behind the water retention projects. RainWise, the City and County program, is funded by the King County Wastewater Treatment Division (WTD) and Seattle Public Utilities (SPU), which are required to manage and reduce combined sewer overflows.

“Both WTD and SPU have an obligation to manage combined sewer overflows and not have more than one overflow location per year,” said Marie Fiore, who handles strategic communications at WTD.

Surface water runoff is also the leading source of many dangerous contaminants in Puget Sound, according to the state Department of Ecology, including lead, mercury, arsenic, motor oil, gasoline, and more. That pollution is a prime threat to orcas, salmon, shellfish, octopuses, and other iconic species of the Pacific Northwest.

By preventing rainfall from funneling down roadways into a storm drain in the first place, rain gardens can be “great to help water quality,” said Sally Brown, a soil scientist and research professor at the University of Washington’s College of the Environment.

For homeowners who want to conserve water or stop using their spigots to water their lawns, however, she cautioned that rain gardens “won’t help water grass or flowers in summer months.” To do that, you’ll need cisterns. Big ones. 

“With a big enough cistern — yes, absolutely!” Brown said. “But for many people even with the best of intentions, it may not be feasible to save water for the summer months.”

RainWise was launched in 2010 by SPU, and WTD joined the program in 2013, said Fiore. Today there are more than 2,000 RainWise installations in Seattle.

“The power behind the program is that it is something that people can do to help solve the problem,” she said, “and it can beautify their yard and neighborhood at the same time.

Because RainWise is funded by WTD ratepayers and SPU stormwater fees, there’s robust funding for the rebate program. “At present, the limiting factor is not funding,” Fiore said. “We are actively working to reduce barriers and improve access to the RainWise program.”

Meanwhile, money for the mini-grant program — which has wider eligibility and also provides money up front rather than reimbursing home and business owners for expenses — is more limited, coming through a WTD grant program with additional funding from the King County Council.

“At the moment I think we have enough funding for a few dozen projects,” said Clark, at Stewardship Partners, which administers the program. He added the group is currently seeking funding “to do dozens more.”

To drum up interest in both programs, the nonprofit’s new RainChargers initiative has put out a splashy ad campaign that focuses on the connection between Seattle residents and local wildlife. In one radio ad, for example, actor Monisa Brown voices an orca who pitches Pearl Jam guitarist Stone Gossard (“The Neighbor”) on the benefits of rain gardens.

“The whole ad campaign came around that concept of being a good neighbor,” Clark said. “The radio ads and the bus-side ads are trying to point out that this is a win-win situation. We can talk about Puget Sound and why it needs rain gardens all day long. The reason that this is a great solution is that it’s also a solution for homeowners.”

Editors’ Note: An earlier version of this story stated that Aaron Clark resided in Beacon Hill. This has been corrected.


Ben Adlin is a reporter and editor who grew up in the Pacific Northwest and currently lives on Capitol Hill. He’s covered politics and legal affairs from Seattle and Los Angeles for the past decade and has been an Emerald contributor since May 2020, writing about community and municipal news. Find him on Twitter at @badlin.

📸 Featured Image: A rain garden work party. (Photo: Stewardship Partners)

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