Pervious Pavement System Evaluation

The use of a pervious pavement can be effective as a low impact development stormwater control. The Urban Watershed Management Branch is evaluating interlocking concrete paver systems as a type of porous pavement. Although the pavers are impermeable, the spaces between the pavers are backfilled with washed, graded stone that acts as structural support for the pavers and also allows water to infiltrate. After passing the paving stones, the stormwater moves through several bedding layers where pollutants are removed. Recent literature shows that the concentration of total suspended solids in the exfiltrate is substantially less than in the infiltrate. Other pollutant constituents are subject to removal by microbial communities that develop with time. Concrete paver systems were chosen for this investigation for several reasons. Layers of the system can be removed, examined, and replaced, facilitating long-term system monitoring and maintenance. The overall objective of this ongoing project is to assess the pollutant removal efficiency of a pervious pavement system from parking lot runoff. One bench-scale study (hydraulic study) determined the flow rates and materials necessary for the full-scale experiment. Another bench-scale study (microbial study) will examine the role of microbial colonies in pollutant removal performance of this porous pavement micro-environment. Results from the two bench-scale experiments will be used to refine the full-scale investigation. This paper focuses on the hydraulic bench-scale study.