The Influence of Road Surface Characteristics on Runoff Quality
Stormwater Conference
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A study carried out in the Auckland region found marked differences in the quality of runoff discharged from a site on the northern motorway compared to three other highway sites. Concentrations of total suspended sediments (TSS), total copper and total zinc were lower than at the other sites. These results were unanticipated; given that the site was on one of New Zealand’s busiest sections of motorway, it was expected that runoff quality would be relatively poor here.
The better quality of runoff may relate to the recent resealing of the motorway with open graded porous asphalt (OGPA). Unlike other road surfaces, OGPA is designed to allow some infiltration of runoff in order to improve road safety and noise reduction. A byproduct of this porous nature is the ability to trap sediments and associated contaminants. However, there is evidence from another site in the study that the ability of OGPA to perform this function reduces over time.
This paper reviews the results of this study and those of others to consider the role that road surfaces play in influencing the generation, transport and removal of contaminants discharged in road runoff.