If water fills that garden, it spills over a low rock dam into a second plant bed. Only if both beds overflow does runoff reach the street, the storm drains, and eventually Jordan Lake. Otherwise, the captured water slowly infiltrates the ground, nourishing the plants and leaving pollutants behind.

“It’s beautiful, and it works! It really works!” Keck said.

Keck’s two beds comprise a 90-square foot “rain garden” – a stormwater-capturing and -filtering device, as well as an amenity in a home landscape. Facing massive costs to improve the quality of water draining from Durham into the Jordan and Falls lakes, the city is promoting rain gardens as one way residents can do their bit for the cause.

“The downside is, we probably need thousands to make a difference,” said Chris Dreps, executive director of the nonprofit Ellerbe Creek Watershed Association. “The upside is, if we teach 1,000 people to do it we might get 10,000 if they spread the word.”

Testing what works

The city is hiring the watershed association to hold several workshops for the public over the next few months, as well as install 13 home rain gardens in the watershed of Ellerbe Creek – Falls Lake’s most polluted tributary.

“That could be getting ready to kick off within a couple of weeks,” said Sandi Wilbur, city manager of the Ellerbe Creek Watershed Improvement Project.

• In another project, teenage crews in the Mayor’s Summer Jobs Program have installed about 40 rain gardens over the past two years, at no charge, for homeowners in the Northeast and Third Fork creek watersheds draining into Jordan Lake.

• In a third program, called “Rain Catchers,” the city is building rain gardens and cisterns, planting trees and trying other pollutant-grabbing measures in the South Ellerbe Creek drainage area, 480 acres of heavily developed downtown and Trinity Park.

“We’re trying to investigate how well these practices work,” said Bobby Louque, project manager for the city’s residential rain-garden program: how well they filter pollutants, and how well having one or more in the yard will appeal to homeowners.

• In a fourth, Durham County’s Soil and Water Conservation District is promoting in-town rain gardens, too, with Community Conservation Assistance that will reimburse homeowners for 75 percent of the cost of installing a rain garden on their own.

“It’s a great program for a county like Durham, that has a lot of people who are interested not only in protecting the environment but are active in doing the right green thing,” said district director Eddie Culberson.

“Any little bit that we can contribute to the task Durham has,” said Brian Jacobson, whose year-old city-installed rain garden has three descending beds, the last closed by a low grassy berm.

Jacobson works for an engineering firm and was familiar with the stringent new Jordan and Falls Lake water quality rules, and, “As a Christian, I feel like I’d like to be a good steward of the environment. ... It’s just part of who I am.”

After a hot, dry spell in August, purple coneflower and black-eyed susans were blooming, ferns were soft green and small shrubs provided height at the back.

“I like the plants they’ve chosen,” he said. “For the most part they’ve survived and grown,” and when one plant “took a turn for the worse” he got a replacement. “I’ve had a good experience,” he said.

To build a garden

Not every yard is suitable for a rain garden, Louque said. Sometimes stormwater can’t easily be caught off a gutter or a driveway. If soil doesn’t drain within 36 hours it’s not a good candidate.

Assuming a yard is suitable, you do the math, said Dave Milkereit, a soil scientist certified by N.C. State University in rain-garden design and construction. Add up the impervious square footage and divide by 10 – that gives you the size rain garden you need. So you consider how the yard is used, where there are obstructions like big roots, draw up a plan and take up pick and shovel.

Milkereit leads a crew of four teen-agers building rain gardens in southern Durham. They started in mid-July and their goal is to have about 25 done before the team has to start school. By Aug. 1, they were building No. 15.

“It’s more interesting than working at McDonald’s,” said garden-builder Traron Trueluck, a senior in the engineering program at Southern High School. “I feel like I’ve lost 50 pounds already.”

They dig the chosen spot out to a depth of about 15 inches, then backfill with nine inches of compost, excavated soil and Stalite – an aggregate of sand and other material. A three-inch layer of hardwood mulch goes on top, and the garden is ready for planting in the fall.

“The plants will need to be watered and really cared for for a year before they’re established,” Milkereit said.

New and different

Early in the summer, at Roseann Keck’s garden, mapleleaf hydrangea had been lush with flowers. Now, in August, the “nice little puffy-pink flowers” have faded, leaving stems colored a rich golden brown. But a garden phlox is in full bloom and on a low-growing grasslike specimen the blade tips had turned bright white.

“Isn’t that cool?” she said. “I didn’t know what colors I was going to have, didn’t know what flowers, it was just so exciting.”

A neighbor across the street calls Keck any time she spots a new blossom, and when Keck is out in the yard runners going by stop to talk about the garden.

Before, she said, “When it rained there was all this wonderful water just going down into the sewers. So when they came out with this rain garden idea I jumped on it.”

Now, she said, “I’m so glad I got this. So happy. It’s wonderful. It’s a beautiful thing.”