Rain gardens are suffering from an identity crisis.

On one hand, there are homeowners who love rain gardens composed of feathery grasses and bushy native shrubs. They even hire landscapers to install them and post signs to let others know that their yard is helping solve the problem of polluted runoff. There are Puget Sound databases and maps packed with examples of the water-sponging plantings. Walking tours in Portland and elsewhere showcase the green landscaping approach.

On the other hand, there are some small, but vocal, clusters of residents opposed to rain gardens that have been proposed for public spaces adjacent to their homes. They invoke the “Ballard rain gardens” — a local shorthand referring to some rain gardens that the city of Seattle installed in parking strips that failed to drain properly and filled with water. (It’s worth noting that the infamous gardens have now either been rebuilt or removed to the apparent satisfaction of residents: The blog Ballard Raingardengue launched to track the offending gardens went quiet a year ago.)

So what is the true nature of Northwest rain gardens? Are they an attractive, affordable tool to shrink the amount of fouled stormwater runoff that damages local lakes and streams? Or are they an infrastructure folly that doesn’t deliver? 

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  • A proposal to build rain gardens in the West Seattle neighborhood near the Barton Pump Station has resurrected the Ballard woes and the arguments against the roadside landscaping. The plan for Barton is being led by King County, which wants to build the gardens along roads to reduce the amount of stormwater runoff and raw sewage waste that spills into Puget Sound. The rain gardens are favored as a more cost-effective, environmentally friendly alternative to building bigger treatment plants and holding tanks.

    Some of the Barton neighbors are lobbying against the plan. They have sent a letter to King County Executive Dow Constantine making their case, and are urging others to join them. One of the residents was kind enough to share the letter with me. I’m a homeowner, and I understand their concerns. Houses are monstrous, scary investments. The idea of a landscape project gone wrong being parked outside your front door is a nightmarish.

    However, after looking through the concerns about the project, it seems most of the worries are largely unfounded, and many are echoes of fears raised in Ballard that never came to pass. Let’s take a look, point by point.

    Ballard rain garden in a storm.

    Ballard rain garden during a March storm, by Lisa Stiffler.

    Kids will drown in the standing water: Rain gardens are typically shallow depressions, about 6-12 inches deep. Rarely do they hold water for more than a few hours. Toddlers admittedly are at risk for drowning in water that’s surprisingly shallow. But keep in mind the rain gardens proposed for Barton are roadside rain gardens, which means they’re right next to a ROAD with moving cars. When my daughter was a toddler, I didn’t leave her unattended in my fenced-in backyard, let alone playing unsupervised in a parking strip along a road.

    Mosquito breeding ground: Mosquitoes can successfully reproduce using water that’s been standing for more than three days. The Barton rain gardens are being designed with underdrains that, should a real gullywasher fill them up, will speed the draining of the water.

    Keep in mind that Washington doesn’t even start worrying about West Nile Virus until about June, which is when the state Department of Health starts its monitoring program. That’s also about the time that Washington begins getting less rain, which means there’s very little chance of standing water in the rain gardens during the summer’s mosquito season. More likely bug breeding spots are birdbaths, the dishes under flowerpots, and clogged gutters that don’t drain at all.

    Also note that the vast majority of Washington’s West Nile cases have come from the Eastern side of the state, and the number of infections has been on the decline. Last year there were zero human cases in the state.

    Sidewalk pavers along rain garden.

    Sidewalk pavers run alongside a Ballard rain garden, by Lisa Stiffler.

    Steeply sided rain gardens are hazards to elderly, young, and disabled: It’s true that a drop off on the side of the road could present a danger. But the plans for Barton don’t suggest the gardens will be steep or deep. The Ballard rain gardens are neither, and there’s a strip of pavement between the curb and plantings that people getting out of cars can step onto (see photo).

    Standing water will attract rats: Again, the water won’t be standing for long. And this is a city laced with streams, pocked with lakes, and riddled with dark and hidey storm drains. If I were a rat, I’d opt for a more secluded drinking spot than a roadside rain garden.

    Designs call for trees planted near sidewalks: The worry here is that newly planted trees will be too near sidewalks, causing root damage and making sidewalks treacherous for walking. I haven’t seen the species list for what will be planted, but it’s easy to choose trees less likely to harm pavement and residents should encourage the county to pick carefully.

    Loss of street parking concerns: Residents fear that the loss of some parking spaces will disrupt driving patterns and force people to park farther from their homes, and this is probably true. They also suggest that there will be more car break-ins when people park farther from home, but no research is offered to support that.

    Homeowners will be sued if the rain gardens hurt people: The rain gardens are on public property. I’m unclear on how a homeowner would be liable, and have not seen any citation of a case where a homeowner was sued over an injury in the public right-of-way.

    Striped sign marks rain garden.

    Striped sign marks rain garden for drivers, by Lisa Stiffler.

    The rain gardens and associated signs are ugly and will “ruin the beauty and quality of life in our neighborhood”: While many people prefer the plantings, some folks clearly love the simplicity of grass and won’t like rain gardens no matter how they perform. The ugliness of the signs, likewise, are a matter of opinion, but they strike me as pretty unoffensive (see photo).

    Rain gardens will reduce property values: The only local, data-based research on rain garden economics available indicates that they actually increase property values by 3.5 to 5 percent. Opponents to the Ballard rain gardens said they talked to some real estate agents who claimed the plantings reduced property values, but there’s no information about how many agents were queried or how they calculated the devaluation.

    Poorer neighborhoods are being targeted for the projects: Barton was chosen for the rain gardens because there’s a problem with sewage overflows in the area, and because the soils were suitable for draining water. Historically and regionally, rain gardens have been seen as street improvements and a desirable improvement.

    Soils are the same as Ballard, and underdrains will clog: King County is doing extensive upfront testing in Barton, including more than two-dozen groundwater monitoring wells and eight test sites for how quickly water soaks into the soil.

    The Ballard project was an anomaly. The city fast tracked the rain gardens to take advantage of cash offered through the federal stimulus program, and officials admit they made shortcuts that wound up backfiring. They cut short pre-project testing so they didn’t discover underground springs that seeped into the rain gardens causing them to fill up even in the absence of actual rain. The soil was worse in spots than expected.

    Using underdrains at Barton will relieve any overfilling, should it occur. There’s no reason to believe that they’ll clog, and if they do, they can be cleaned. The county needs this infrastructure to work to meet obligations to clean up sewage spills, they need for these gardens to work.

    Underdrain illustration

    Illustration of a rain garden with an underdrain, from King County.

    The underdrain design is untested technology: Underdrains are a basic feature for many rain gardens, and often included in larger projects. The specific design of the Barton gardens might be unique, but that’s exactly what you want. A fundamental principal for creating effective rain gardens is to make sure the size, soil, plantings, and orientation are well suited to the location and purpose of the garden.

    The only example of rain garden “retrofits” are in Ballard: Most rain garden projects are retrofits, which just means they’re constructed in already developed neighborhoods. There are hundreds, if not thousands, of these projects in the Northwest alone. Unfortunately and unfairly, the countless working rain gardens have fallen into the shadow of Ballard.

    A couple of examples that are top of mind include projects in south Seattle that consultant Cari Simson has managed. One was a roadside rain garden retrofit at Markey Manufacturing near the Duwamish River, a project that has beautified an industrial street and eliminated massive puddles.

    “Those are performing amazingly,” Simson said. “This is an industrial business. The owners never would have imagined they would be on the forefront of green infrastructure.”

    More recently, Simson helped a group of neighbors in Georgetown install rain gardens on a residential block of South Orcas Street. The 1,375 square feet of roadside rain gardens now front six homes.

    Residents liked that they wouldn’t have to mow their roadside lawns anymore, Simson said. “There was a lot of enthusiasm.”

    Rain garden in NW Seattle.

    Rain garden in Seattle’s original SEA Street project, by Lisa Stiffler.

    There are other Seattle examples, as well as projects in Puyallup, Portland, and Gresham that come immediately to mind.

    County and city won’t maintain rain gardens: This is a tricky area. In Seattle, the Department of Transportation is responsible for the public right-of-way, which includes the planting strips between the road and sidewalk. Residents have to get permits to do extensive work in the strip, such as removing trees, installing raised garden beds, or paving. While roadsides are public property, residents generally are expected to maintain them so that plants don’t spill out into the street or become heaped with trash. But rain gardens admittedly fall into a sort of gray area. Neighbors are right to ask county officials for a clear explanation of what sort of maintenance support they can expect.

    Rain gardens will require more fossil fuels that conventional stormwater solutions: Building extra sewage treatment capacity and more storage vaults for polluted runoff, or laying new pipes to separate stormwater from sewage seem like fairly greenhouse-gas intensive projects relative to installing rain gardens. But I haven’t seen data to show which approach would produce more carbon dioxide, so that question is unresolved.

    Reining in rain garden fears

    Clearly, some of the Barton neighbors are genuinely worried about these roadside rain gardens, and have made a serious effort to compile their concerns. But digging deeper into their objections, most are overblown. Experience, research, and examples from around the Northwest show that rain gardens can and do work most of the time.

    Ballard rain garden "no parking" sign.

    Ballard roadside rain garden “no parking” sign on flipside of striped sign, by Lisa Stiffler.

    Admittedly, there were concerns that I couldn’t speak to, namely those related to long-term maintenance and existing water challenges, and I’d encourage folks from King County to weigh in here with comments if they’d like to. Likewise, if residents near the Barton project have more to say or feel I haven’t accurately portrayed their concern, I hope they comment as well.

    Overall, the county is moving slowly on this project, giving lots of opportunity for public input, and making the whole process admirably transparent.

    I hope that residents worried about what’s being proposed will go visit the Ballard rain gardens and see how they look and perform in person.

    The gardens proposed for Barton and elsewhere are part of a broader effort to recover the health of Puget Sound, an effort that’s going to require residents to change how they live, work, build, and play in Western Washington if it’s to succeed.