Individual rain gardens keep runoff out of streams

By STEVE BROWN

Capital Press

PUYALLUP, Wash. -- "Rain gardens" have popped up in many neighborhoods around the Puget Sound as homeowners retrofit their properties to reduce runoff.

Rain gardens are a new label for what used to be called bioswales or retention pools, said Dan McCain, of Storm Lake Growers. He has worked with the nonprofit Stewardship Partners in years past on similar projects.

The idea has taken root in Maryland, Alaska, Kansas City and San Francisco.

Stacy Gianas of Stewardship Partners said the Western Washington goal of 12,000 rain gardens by 2016 is ambitious. That many rain gardens will soak up 160 million gallons of runoff annually that could otherwise carry pollutants into storm sewers, irrigation ditches and other waterways that feed the Puget Sound.

A rain garden consists of porous soil covered by a thin layer of mulch. A stand of native grasses, shrubs and small trees is also established to promote evapotranspiration, maintain soil porosity, encourage biological activity and promote the uptake of some pollutants.

Runoff from impervious areas -- such as roofs, driveways and patios -- is directed into the rain garden.

"We're trying to promote the rain gardens around salmon-bearing streams, where dissolved oxygen levels and coliform levels are critical," Gianas said.

Besides reducing pollution, she said, the gardens help prevent flooding, increase home value, are low maintenance and help communities save millions of dollars in expensive stormwater projects.

Many residential rain gardens have been built in Seattle, Burien, Tacoma and Puyallup. Several schools, city offices and public libraries have also participated.

The city of Eatonville -- with a population of about 2,500 -- has the highest per capita number of rain gardens, "with a goal to disconnect entirely from the stormwater system," she said.

Other communities have also encouraged residents to install rain gardens, she said. Bellingham and Puyallup offer incentives to homeowners, and Kitsap County offers $500 rebates to homeowners.

Stewardship Partners has teamed up with Washington State University Extension to lead the campaign, along with local governments, conservation districts, conservancy nonprofits and nurseries.

Storm Lake was one of the first nurseries in the area to offer native plants, McCain said.

McCain's operation, which is one of several that have provided plants for the rain gardens, is a wholesale nursery. Not many area retailers stock native plants, he said.

"Sometimes homeowner groups looking to re-establish native vegetation will come to us," he said. "We give them the opportunity to buy at wholesale, and we charge them sales tax under state law."

He said landscape contractors and homeowners have two goals in mind: "that the plants function well and look nice."

Native plants tend to be less showy, but the most ornamental include salal, native irises and evergreen huckleberries. Low-growing sedges and rushes are also popular.

About 700 rain gardens were registered by the beginning of July, Gianas said.

"Besides the website, we have other outreach efforts, like free evening workshops and volunteer planting events to involve whole communities," she said.

WSU's Pierce County Extension has prepared a 45-page handbook to guide homeowners through the process of locating, designing, building, planting and maintaining rain gardens.

Online

www.12000raingardens.org