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Nature's filter used on parking lot runoff Agency installs trees, soil to protect creek


A 303-year-old city like Annapolis suffers no dearth of Colonial charm. But what it sometimes does not have is such modern inventions as storm water management facilities.

The state Department of Natural Resources put the finishing touches yesterday on a clean-water project in its Annapolis headquarters parking lot that planners hope will inspire managers of 74 other decades-old parking facilities in the area.

Frank Dawson, director of the DNR's watershed restoration division, said his staff began researching the project two years ago when Friends of College Creek discovered that water contaminated with oil and refuse was running directly from the lots into the creek.

"The city is older, and a lot of things were built" before the state required such facilities for the construction of developments, Dawson said.

"DNR feels some responsibility to not just tell people how to manage their lawns. We felt it would be good for us to demonstrate storm water management on our own land," he said.

With funds from the State Highway Administration, the Maryland Department of the Environment and the state Department of General Services, the DNR spent about $70,000 equipping its 2.5-acre parking lot to include a "bioretention facility" that uses plants to filter out 70 percent to 90 percent of contaminants.

Instead of collecting rain in a pond and pumping it back into waterways, which Dawson said is the conventional method, the idea of bioretention is to use trees, shrubbery and soil to extract nitrogen and phosphorus -- which contaminate waterways but which are used by plants for growth -- before the water is pumped back into the creek.

Goal is replication

"We're trying to mimic nature in the way that nutrients are recycled in a living, dynamic system," said Larry Coffman, associate director in the Prince George's County Department of Environmental Resources, who proposed the bioretention system.

"The goal is to replicate predevelopment hydrology. You just can't replace that original hydrologic regime with a pipe and pond."

Coffman said the DNR parking lot is the first bioretention facility in Anne Arundel County and one of about 150 in the state, including 100 in Prince George's County. He said the number of such facilities in Maryland has grown gradually. The idea is catching on in California, Pennsylvania and Delaware and has attracted storm water management planners to Prince George's County from as far away as Japan, Germany and Poland.

"What we're finding is that current technology does not solve all the problems that we hoped it would, and that restoring the hydrological regime is very important to protecting streams," Coffman said.

In the DNR parking lot, planners removed 17 parking spaces, replaced asphalt with an underground pipe covered with soil and planted a tiny grove of trees and shrubs. When rainwater runs off the parking lot, the soil and plants filter out contaminants before the water enters the pipe and is funneled into College Creek.

Before the bioretention facility was constructed, "whenever it rained, whatever was on the parking lot ground, whether it was cigarettes or gum wrappers or beer tabs, it was in the creek in a matter of minutes," said Ron Gardner, a DNR environmental planner.

Edward Cline, deputy director of the Maryland Stadium Authority, said sports fans like the look of two bioretention facilities built last year in parking lots E and H of the Baltimore Ravens stadium.

Parklike setting

"Parking lot H is the tailgating area for Ravens games," Cline said. "When there's a football game, it's heavily used for a large portion of the day, and this provides a parklike setting. With a [storm water pond], sometimes you have to use a chain-link fence around it."

Dawson said the DNR will monitor the bioretention facility to determine how well it removes contaminants.

The department hopes the results will encourage managers of neighboring parking lots to consider similar projects, he said.

Camille Destafney, head of the environmental division of the Naval Academy, which has several parking lots from which runoff goes into College Creek, said she is considering installing bioretention facilities but wants to see how well the DNR project performs.

"It's really important in order to sell a project to say, 'This is how it works. This is what it looks like,' " Destafney said, "and whether it works or not."

Pub Date: 12/02/98

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