Correction to This Article
This column misstated the name of an environmental non-profit organization in Beltsville. The company is called the Low Impact Development Center.

Rain Gardens Make Water Good to the Last Drop

By Adrian Higgins
Thursday, July 3, 2008

A downspout descends from the side of the brick Colonial house of Andy and Shizumi Manale in Silver Spring, but instead of emptying into the foundation bed, it stops about eight feet above the ground, where it moves over the path, like an arch, to empty into a bed of shrubs and perennials on the property line.

For the hostas and azaleas, it's bathtime.

Shizumi Manale disappears as her husband explains that he hates to waste bath water. She has gone upstairs to pull the plug on the tub (actually, to turn on a pump), and after a few seconds, water comes gushing out of the downspout, down a Japanese-style rain chain attached to it and into the growing beds. Andy Manale offers a proud grin, but the recycled bath water is just one way that he irrigates his lush garden. In virtually every garden area around the house, the land brims with rainwater from the roofs and from three sump pumps.

The Manales live in a typical Washington neighborhood of sticky clay, high water tables and water seeping into the street. But even in a year of excessive rain, "very little water actually leaves my property," he said.

They are among a pioneering class of gardeners who have turned to rain gardens, designed to slow and trap storm water in a way that's good for the garden and the environment. The plants love it, and the Manales have done their bit to prevent runoff from polluting local waterways and, ultimately, the Chesapeake Bay.

Before urbanization, the marshland and forests held rainwater, filtered it and allowed it to seep slowly into aquifers and streams. In our modern world of roofs, parking lots, roads and lawns, fast-moving water carries pollutants to the bay and, through its sheer energy, erodes and silts the ailing estuary and its tributaries.

Although the pre-settlement swamps of Washington have gone, "we can mimic what the wetlands used to do," said Andy Manale, a policy analyst and biochemist at the Environmental Protection Agency.

Rain gardens have become an increasingly popular component of eco-gardening in an age of global warming and weather extremes. Some local jurisdictions give grants to defray their cost.

But to create one, you have to dig. The water is arrested by working the earth: removing compacted clay soil and backfilling the excavated area with a permeable soil mix containing lots of gravel or sharp sand. Buried perforated pipes take the water away to distant parts of the yard. About 10 minutes after the bathtub demonstration, Shizumi Manale called from about 30 feet away to point out a plant border in the lower lawn. "I see the flowing water," she said.

The Manales have positioned large steppingstones in these water courses and planted them with perennials, shrubs and trees that can take brief periods of wet soil. Choices include azaleas, hostas, pulmonarias -- plants that like moist soil but can take dry conditions once they have become established and develop deep roots. Because these gardens are free-draining, they remain saturated for hours, not days, and thus allow a fairly broad palette of plants.

The Manales began building their rain gardens soon after moving to their home 21 years ago, and the features can be found on all four sides of the house. More are planned, and existing ones will be refined. "It's about observing what's happening on the land," Andy Manale said. "Where do I have runoff, where do I want to slow it down, where do I plant trees to take advantage of the water?"

To create theirs, the Manales excavated as deeply as three feet or more, a depth that would require knowing the exact location of buried utility pipes and wires, not to mention a strong back. He used much of the surplus clay to form a berm behind a fish pond.

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