Jun 30, 2011

Rain Through the Ages

Many users have always known that StormPave genuine clay pavers from Pine Hall Brick work well as parking lot surfaces. But officials in Annapolis, Md., found that they also efficiently drain rainwater from heavy storms, help with archaeological research and can even prevent pedestrians from slipping and falling.

The story began in September 2010 when Annapolis was hit by the remnants of Tropical Storm Nicole. A deluge of a little more than 9 in. of rain in a 24-hour period fell on the city, which a National Weather Service hydrologist ranked as between a 100-year and a 200-year rainfall.

The rain came in torrents onto the parking lot of the Annapolis & The Chesapeake Bay Visitor’s Center, which was paved with StormPave clay brick permeable pavers from Pine Hall Brick Co.

From there, the rainwater promptly disappeared.
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Landscape architect Shelley Rentsch, RLA, ASLA, principal of the O’Doherty Group, which oversaw the design of the installation, said the 10,000-sq-ft parking lot directs rainwater underground to six rain gardens that are on the edge of the property. From there, the water goes to an outflow pipe.

Rentsch said the only time any drainage has come from that pipe was during the tropical storm—and then it was only a trickle.

The $795,000 project was funded mostly through a federal grant from the American Recovery and Reinvestment Act through the Maryland Department of the Environment. The Baltimore Sun reported that the city paid $64,000.

Rentsch said the project’s goal was to create a green parking lot that was welcoming to visitors and complemented the surrounding historic district, which is made up of red brick buildings, some of which date back to Colonial times.
“We went about it to create a people place, and it was more about that than it was about the engineering,” Rentsch said. “The aesthetics, the engineering and the environment should come together every time.”

More Historical Proportions

In a way, the StormPave installation has even contributed to the area’s history. Excavations at the job site led to the discovery of two privies owned by Charles Carroll of Carrollton (1737 to 1832), a wealthy Maryland planter who was an early advocate of independence from Great Britain and the last surviving signer of the Declaration of Independence.

Lily Openshaw, project manager for the city, said that 7,857 of catalogued artifacts were recovered as archaeologists worked alongside paver installers.
“We came up with a monitoring plan, which identified what we considered the hot spots, and we scheduled for their field person to be out at the site when the contractor went into those areas,” she said. “When she would find something, she would have them move. I think we stopped one full day, but we were able to work with them on staging and let them keep working.”

The bonus was that the engineering design kept the paver installation above the existing grade, which preserved as much of the undisturbed soil as possible. This means any artifacts remaining in the ground will remain as they have for the past two centuries. Additionally, it is relatively easy to remove clay pavers, set them aside and then put them back, which means that researchers could conceivably come back and do further archaeological digs in the future.

Openshaw said the installation offered one unexpected bonus: no ice.

In the past, the parking lot was paved in asphalt. In winter, it would typically rain and water would puddle up and then freeze. Sometimes, the city would have to rope off the parking lot to keep down the possibility of fender benders and falls to the pavement.

Openshaw reported that the first winter upon installation, the water went into the ground and the brick pavers dried out. There was no standing water or ice.

“It has performed better than expected,” she said. “This is fabulous; it really is—and it looks beautiful, too.”

Marc Barnes is a writer for King's English, an advertising,
marketing and public relations agency in Greensboro, N.C.

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