Maintenance of Infiltration in Modular Interlocking Concrete Pavers with External Drainage Cells

Abstract
This chapter examines the effectiveness of methods used to restore the infiltration capacity of permeable pavers. The decrease in infiltration capacity with age and increased traffic use was tested and the possibility of street-sweeping/vacuuming the surface to maintain infiltration capacities of permeable pavers was investigated. Permeable pavers allow water to easily infiltrate into the subsurface layers, thus reducing the volume of runoff reaching receiving waters. As permeable-paver installations age, and are heavily used, the infiltration capacity decreases due to clogging of the external drainage cell (EDC) with fines (silt and clay), organic matter and extractable solvents from automobiles (primarily oil and grease).
An eight-year old installation of two different types of permeable pavements in a parking lot at the University of Guelph was studied. No maintenance procedures were used over the 8 y period, other than snow removal and street sweeping with rotating brushes once a year in spring. Infiltration rates were tested before and after material was extracted from the EDCs and subjected to a particle size and constituent analysis. The extracted material was tested for a number of different organic and chemical constituents such as heavy metals, nutrients and organic matter. Results indicate that the infiltration capacity decreases with increasing average daily traffic counts, and as the amount of organic matter and fine matter in the EDC material increases. Furthermore, the tests indicate that the infiltration capacity can be significantly improved by removing 10-20 mm (0.4-0.8 inches) of EDC material, a removal depth that might be achieved by using certain equipment.
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