The City of Chicago has demonstrated how permeable pavers can be used to achieve multiple objectives in the retrofit of a high density residential area. ¹  In Fall 2001, the Chicago Department of Environment, in cooperation with Alderman Mary Ann Smith (48^th) and the City’s Department of Transportation, reconstructed the asphalt alley shown in the top left photograph with a permeable system that was designed to alleviate the alleyway's chronic problems with flooding. A porous gravel structure was used to provide heavy load bearing support, unlimited traffic volume and parking duration, all while being able to handle up to 3 inches of rainfall per hour by allowing rainwater to soak into the ground. This successful retrofit not only reduced flooding and polluted runoff without relying on the sewer system, but it also helped to reduce the urban heat island effect through its use of porous, light-colored materials. 

Another example of the application of permeable pavers to high density residential areas comes from work in England.² At Coventry University, researchers are presenting the practical idea that stormwater, which is a significant component of the "wastewater" currently removed from a site, may be more appropriately seen as a resource.  In this view, a permeable paver system can be used to further advantage by undersealing it so that stormwater can be retained for reuse in non-potable services.  The sub-base of a permeable footpath, driveway or parking lot can be easily reconstructed with an impermeable membrane so that the desired storage volume is contained, yet the surface still exists as available land within its intended purpose.  Such a system is being installed for a new Youth Hostel in Nottinghamshire, UK, where stormwater storage will be reused in toilet flushing.  Stormwater from the permeable parking area, along with that collected from the hostel's roofs, will be stored, while any overflow from the sub-base goes into an infiltration trench.  This system is expected to provide totally for toilet flushing each month for up to 33 people in the Hostel.

In high density residential areas, other permeable paver designs can be adapted from commercial, industrial and institutional settings.  For example, permeable pavers can be used effectively in a number of ways when designing an apartment complex's parking lots.

References

¹ Photographs and information taken from the Urban Heat Island Initiative Alley Reconstruction case study provided by Invisible Structures, Inc. See http://www.invisiblestructures.com for more information.

² Pratt, C.J., 1999: Use of permeable, reservoir pavement constructions for stormwater treatment and storage for re-use. Wat. Sci. Tech., 39 (5), 145-151. 

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