You never get a second chance to make a first impression, whether you are a potential new employee -- or a parking lot. Officials in Annapolis, Md., certainly knew the latter. The parking lot for Gotts Court -- the Annapolis & The Chesapeake Bay Visitor's Center -- was made of asphalt, was worn down, and didn’t drain properly. In the summer that meant ankle-deep puddles; in the winter that meant ice, possible slips and falls, and the potential for lawsuits.
Permeable Paver for Parking
You never get a second chance to make a first impression, whether you are a potential new employee — or a parking lot.
Officials in Annapolis, Md., certainly knew the latter. The parking lot for Gotts Court — the Annapolis & The Chesapeake Bay Visitor’s Center — was made of asphalt, was worn down, and didn’t drain properly. In the summer that meant ankle-deep puddles; in the winter that meant ice, possible slips and falls, and the potential for lawsuits.
The lot was also a contradiction in terms: the place where you were supposed to park at a visitor’s center was often inaccessible. The only way in was through a parking garage. When the garage was deemed full — due in part to spaces set aside for monthly pass-holders — it was closed off, which meant that passing motorists could occasionally see an empty parking lot, but couldn’t get to it. In addition, from an aesthetic point of view, asphalt and concrete curbing didn’t fit in an open space in the middle of one of the most historic cities in the United States.
All in all, the parking lot in front of the welcome center wasn’t very welcoming.
Landscape architect Shelley Rentsch, RLA, ASLA, who is a partner in Annapolis Landscape Architects, resolutely set out to address all of the problems. Reorienting the entrance meant that there would be better access; and specifying clay brick permeable pavers instead of asphalt better complemented the surrounding red clay brick buildings, some of which date from Colonial times.
That left the drainage. Rentsch designed in a permeable paver drainage system using specially designed StormPave pavers. Made to resemble conventional English Edge pavers, StormPave has a 1/4-inch joint width so that water can infiltrate the system where it is naturally filtered as it dissipates into the ground instead of washing surface pollutants to nearby storm drains or waterways.
“We went about it to create a people place, and it was more about that than it was about the engineering,” said Rentsch. “The aesthetics, the engineering and the environment should come together every time.”
Underneath the pavers, the installation is remarkably different than a conventional installation, which uses crusher run and sand. Graded aggregates without fine particles are used, with larger aggregates on the sub base, and then progressively smaller aggregates layered atop them. Finally, the pavers are placed atop the smallest aggregates, which are also swept into the spaces between the pavers.
In the Annapolis project, rainwater falls on the pavers, fills the spaces in the aggregate underneath them, and is directed underground to six rain gardens that are on the edges of the property. From there, the water goes to an outflow pipe.
Trial by flood
The project was put to the test a year ago when Annapolis was hit by the remnants of Tropical Storm Nicole and its accompanying deluge of a little more than nine inches of rainfall in a 24-hour period. A National Weather Service hydrologist ranked the storm between a 100-year and a 200-year rainfall (that means that there is a chance of between one-half percent and one percent of that much rain falling in that length of time in any given year.)
The rain fell in torrents onto the parking lot – and from there, it promptly disappeared. Rentsch said that Tropical Storm Nicole is the only time that any drainage has come from the pipe and then, it was only a trickle.
During this past winter, visitors also noticed there was no ice. Again, the permeable installation took away the rainwater, which allowed the surface of the pavers to dry out. When temperatures dropped, there was no water to freeze — thus no ice.
A historic district
The deep red color of the pavers complements the surrounding neighborhood and its red brick buildings. “The paver really had to look like it belonged there,” said Rentsch.
But during construction, the parking lot itself actually became a historic site. Excavations led to the discovery of two privies owned by Charles Carroll of Carrollton (1737-1832), 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 of Annapolis, said that 7,857 catalogued artifacts were recovered as archaeologists worked alongside paver installers. Careful planning and cooperation led to the loss of only one day of work.
The bonus is that the engineering design kept the paver installation above the existing grade, which preserved as much of the undisturbed soil as possible. That means that any artifacts remaining in the ground will remain as they have for the past two centuries. Additionally, it would be relatively easy to remove the 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.