Behind the Museum of Science in Raleigh, there is a small area between the parking garage and other buildings. This area is almost 100% paved, but has no visible drains, except for a single trench drain. The area captures most of the runoff from the surrounding hard surfaces, the buildings, and the roofs using permeable pavers… a tiled paving system. This is used in combination with an attractive green area with bamboo, to drain the entire area. The value of this system is that it significantly reduces the impact of the runoff on the City’s stormwater system, and instead stores stormwater below the paving and allows it to permeate into the ground.
This system provides a very attractive, charming appearance. It can be used to reduce traffic speed in neighborhoods. It can also be used for large parking areas, such as box retail stores, to capture and retain rainwater, prevent flooding, and reduce or potentially eliminate stormwater piping for a large parking area. The green implications of permeable paving for large metropolitan, and urbanizing areas, such as around Raleigh and throughout North Carolina are significant.
Information is available by the City of Raleigh Engineering Services here including a video on permeable paving by the North Carolina Cooperative Extension detailing how permeable paving works. Soils in central North Carolina can be quite clay-intensive, however, permeable paving can capture 50% or more of rainwater, because most rainwater events are small, short events. The system is worst case scenarios, and can be combined with other features such as retention areas, swales, and green areas (such as may be required for parking area landscaping requirements).
When looking at the costs of the system, the cost of the paving is not the only cost to be considered, because permeable paving works as part of an overall stormwater management system, to capture and retain rainwater rather than transmitting it directly to a stormwater piping system. therefore, the cost of the entire system should be compared, rather than simply the cost of the surface paving. As the State of North Carolina, especially cities and towns in metropolitan areas, continue to urbanize rapidly, the video mentioned above points out that stormwater is the number one source of pollutants for municipal areas, which leads to costs for the municipality and users to treat and separate stormwater. Permeable paving systems has the potential to eliminate the loads on the system by 50% or more. A very good informational page about the system and cost savings is available from the Interlocking Concrete Pavement Institute, here.
For areas which are urbanizing and transitioning from rural, agricultural areas to urbanized and suburban areas, this is a great, simple technology (modern and traditional at the same time), for providing a very attractive pavement solution, reduce traffic speeds, improve quality of life, and also turn an area which would have been a major source of pollution ( box store parking lots) into an area which can capture, replenish, and retain ground water, and reduce or potentially eliminate stormwater piping systems. When combined with landscaped features, this can even turn an area that would have deterred pedestrians into an attractive area that people can enjoy spending time.