The heavy metal trapping efficiency of pervious paving systems

Sealing of urban areas leads to increasing flooding and contamination which can be addressed by replacing impermeable surfaces with Pervious Paving Systems (PPS) which have the potential to remediate some pollution in situ.... [ view full abstract ]

Sealing of urban areas leads to increasing flooding and contamination which can be addressed by replacing impermeable surfaces with Pervious Paving Systems (PPS) which have the potential to remediate some pollution in situ.
This paper presents results of the testing of laboratory-based models with a variety of surface courses and sub-surface structures in order to monitor their pollutant-retention capabilities. These models included porous asphalt (PA), pervious concrete (PC), block pavers (BP) and one PA which had been a quarry car park for 12 years. The total monitoring period was 3 years. Coventry Road Sediment (CRS) and unused oil was applied to the surfaces and artificially rained on in order to investigate their efficiency in dealing with contamination. Water quality of the effluent subsequently draining from the rig was found to be better than WHO potable water guidelines.
A core was taken down through the surface of one PA rig into the subsurface structure, and revealed that the majority of the sediment remained in the surface course, identified by its high heavy metal concentrations. However, these levels were lower than the original CRS, suggesting some of the metals had migrated down through the rig. Relatively high levels of metals were found in the tap water feed to the rainfall simulator which was removed from the effluent, suggesting that the large amounts of sediment found throughout the aggregate layer were acting as sinks for the metals. This has implications for management at end-of-life for the device, whether it is classified hazardous material.