By Bill O’Brian

Environmental education, wildlife conservation and healthy hydrology converge at Tualatin River National Wildlife Refuge — in the parking lot.

For five years, the parking lot’s centerpiece, a sophisticated bioswale, has welcomed refuge visitors, hosted birds and pollinators, and filtered stormwater runoff before it enters the Tualatin River ecosystem near Portland, OR.

“That bioswale is like a mini-wetland,” says visitor services manager Kim Strassburg. “It is a model, and it is an example of something you can do in your own backyard.”

Refuge manager Erin Holmes concurs: “It provides an amazing opportunity for people to learn about native plants they can plant in their backyards. We’ve got nesting birds in there. It’s a great place for pollinators. It’s a little habitat for little critters.”

A bioswale is a manmade, gently sloped, vegetation-filled depression designed to remove pollution from surface runoff water. The Tualatin River Refuge bioswale is state-of-the-art. Completed in 2011, it and the surrounding parking lot cost roughly $90,000, most of it American Recovery and Reinvestment Act money. Sustainable methods and materials — including warm-mix asphalt and permeable pavers — were used in building the 54-space lot. It meets “low impact development” (LID) standards.

“As it relates to stormwater, LID means we are looking for ways to understand where polluted runoff is going and respond thoughtfully,” says Alex Schwartz, a U.S. Fish and Wildlife Service Pacific Region landscape architect who oversaw the bioswale’s design and construction. “We want to clean [the runoff] and slow it down as close to its point of origin as possible. To me, it means not passing the problem down the watershed in a pipe or with grassy swales, as has been standard practice for many years. LID means understanding the place and responding with your stormwater management scheme in a way that mimics the natural functions of the watershed.”

The bioswale’s 12,800-square-foot planted area collects, slows and filters runoff from about 26,000 square feet of tarmac/pervious pavers and from a refuge building roof. Three water control structures on three tiers under the bioswale slow runoff before it enters refuge wetlands and the river.

All of the bioswale’s plants are native to Oregon and can tolerate automotive runoff.

“There is a lot of nasty junk that potentially gets in there,” says Schwartz. Things like soot particles from exhaust, copper from brake pads, lead, tire rubber, motor oil and antifreeze. “It’s important to remember that besides dealing with automotive pollution, bioswales also help control the temperature and flow rate of impervious runoff, which can be higher than normal and have effects on macroinvertebrates, fish and wildlife. Facilities like this can help prevent stream incision and erosion, which in turn means healthier riparian areas in a watershed.”

In part because of inspirational signage such as “All life needs water… We all live downstream” and a display explaining the bioswale’s purpose, the concept is a big hit with refuge visitors and a showcase for sustainable runoff management.

“We’ve had cities come and ask us about it,” says refuge manager Holmes. “They want to model it.”

Individuals are curious, too. “We get questions all the time,” says visitor services manager Strassburg. “People have come out and said, ‘Can you just talk to our apartment manager?’ I’ve had several of those. ‘What’s the name of the pavers you used?’ ‘How do I get those plants?’ ‘Where do you buy them?’ ”

But the key to ongoing success is two volunteer botanists at Tualatin River Refuge, Ginny Maffitt and Sandy Reid.

“They have rallied the troops, and they bring in the Master Gardeners [of Washington County] to have work parties” to maintain the bioswale, says Strassburg. “Without them, it would be very difficult to maintain and have it looking the way it does.”