Water quality improvement by base course aggregate in a permeable pavement with underlying reservoir structure

Permeable pavements are an emerging water sensitive urban design component that allow for onsite infiltration of stormwater while providing both a structurally supportive surface and full amenity value of above lying land. This paper reports on research investigating the water quality effects of modifying the structure of a permeable pavement to accommodate underlying water storage amongst aggregate for harvesting and reuse. To investigate the effects on water quality of water storage in an aggregate matrix, model pavement structures were constructed in a laboratory and a synthetic stormwater was applied directly to the pavement reservoirs. The stored water was then monitored for quality changes over a six day period. Results suggested an improvement in water quality is achieved with storage within a dolomite and calcite substructure. Reductions in heavy metal (Cu, Pb, Zn) and phosphorous concentrations exceeded 90% in all cases. While an overall improvement in water quality is achieved, increases in pH, alkalinity and dissolved solids were evident. Some reduction in water quality was observed with storage when the stored volume was low and/or the settled material was disturbed. The outcomes of this work will be used in further investigations on the effect of long term storage and multiple infiltration events.