New Zealand’s first permeable pavement study
A new type of road surface gaining in popularity overseas because of its environmental benefits has been successfully trialled in the Auckland suburb of Birkdale.
Researchers from The University of Auckland’s Faculty of Engineering completed a study of the surface on a 200 square metre section of Birkdale Road on the North Shore.
Called ‘permeable pavement’, it is made up of interlocking concrete blocks designed to soak up stormwater, and reduce contaminants in water which flows to streams and eventually to the harbour.
Dr Elizabeth Fassman and ME student Samuel Blackbourn from the University’s Department of Civil and Environmental Engineering monitored the effectiveness of the surface over two years. Results show it decreased stormwater run-off at peak flow by an average of 75 percent during most storms, and reduced the volume of total run-off by about 40 percent, 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 also had on average 70 to 80 percent 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,” says Dr Fassman. “Permeable pavement is emerging internationally as an important stormwater management technology. We set out to prove this technology works under local conditions, and in comparison to international studies it performed well, despite the challenging conditions. Essentially we tried to doom it to failure by installing it on a busy roadway. Most permeable pavements overseas are in carparks or quiet roads.”
Seattle in the United States has been an avid adopter of the technology, installing the surface widely on footpaths and some roadways 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,” Dr Fassman says.
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. The researchers have delivered a report on the performance of permeable pavement, and observations about maintenance and installation procedures. Guidelines on how to design and install the system are being updated by the North Shore City Council.
