A new type of road surface that is gaining in popularity because of its environmental benefits has been successfully trialled in the Auckland suburb of Birkdale.
Called ‘permeable pavement’, it is made up of interlocking concrete blocks designed to soak up stormwater and reduce contaminants in water that flows to streams and eventually to the harbour.
Dr Elizabeth Fassman and Samuel Blackbourn, a mechanical engineering student from the University of Auckland’s Department of Civil and Environmental Engineering, monitored the effectiveness of the surface on a 200m2 section of road over two years.
Results showed it decreased stormwater run-off at peak flow by an average of 75 per cent during most storms and reduced the volume of total run-off by about 40 per cent when compared to run-off from asphalt on the same road.
Storms with less than 7mm rainfall produced only a slow trickle of run-off that was too low to measure accurately. Run-off from the permeable pavement had on average 70 to 80 per cent less sediment, copper, and zinc.
‘The water quality was as good as water treated by detention basins or constructed wetlands, which are commonly used to control stormwater but can take up a lot of space,’ said Fassman.
The technology has been widely adopted in Seattle in the US, where the surface has been deployed on footpaths and some roads to control stormwater run-off.
‘There are miles of roads and carparks in Auckland, and if they were converted to this surface it would make a huge impact on protecting our waterways and streams, and preventing stream erosion,’ Fassman added.
The trial also confirmed the best installation techniques for the system, how susceptible it is to clogging and how it responds under the weight of heavy traffic.
The trial was supported by the Auckland Regional Council and North Shore City Council.