City of Seattle Facing Expensive Fix for Poorly Planned Rain Gardens

An April 22 InvestigateWest article highlights the need for careful planning when implementing rain gardens to treat stormwater runoff.  Maryland now requires the use of environmental site design techniques, such as rain gardens, to the maximum extent practicable when treating stormwater runoff.  The article compares the successful use of rain gardens in one Seattle, Washington, neighborhood against another Seattle neighborhood that had less successful results.

 But when the city recently tried going green in the Ballard neighborhood, homeowners there felt like they got stuck with the booby prize.

The rain gardens installed by the city last summer and fall haven’t worked as planned. The gardens, which look sort of like shallow, sparsely-planted ditches running between the road and sidewalk, fill with water – and stay filled up. Some of the rain gardens drain over the course of hours or days, but some become mini ponds until the city comes to pump out the water.

Many of the residents are not pleased. They worry that the swamped gardens are a drowning hazard for young children, a breeding ground for mosquitoes, and will lower their property values. There’s even a neighborhood blog calling for their removal.  …

But Ballard’s rain garden fiasco is a very visible reminder that green solutions aren’t always quick, easy and predictable. The project offers a cautionary tale to be heeded nationwide: rain gardens have limitations.  

 “Low-impact development technologies are very site specific,” said Art Castle, interim executive vice president at the Building Industry Association of Washington, an organization representing the housing industry. Castle, who served on an advisory committee that helped the state craft its low-impact development rules, says he believes rain gardens work, but worries about mandates for their use. 

The City of Seattle estimates that it will cost an additional $500 million to fix the dysfunctional Ballard rain gardens.  Unlike the failure in Ballard, the article describes the success of rain gardens in another Seattle neighborhood.

West Seattle’s High Point is an emerald jewel in Seattle’s green infrastructure crown. Block after block of the low-income housing development is lined with rain gardens that capture rainwater runoff that gushes off the roadways and roofs.

Some of the gardens are nearly a foot deep. The sloping ditches are planted with red-twig dogwood and huckleberry bushes, grasses and sedges – all plants that don’t mind soggy soil. The rainwater soaks into the ground rather than flowing into the city’s stormwater or sewer system. As it soaks, oil and grease, pesticides and other pollutants are filtered out and often gobbled up by organisms in the soil.

Seattle Public Utilities was the driving force behind the High Point gardens, which are a poster child for how attractive green infrastructure can be. Just hours after a gully-washer, the rain gardens are hardly wet.

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