IPWEA Awards 2011

Water Sensitive Urban Design

Project Summary

The use of new innovative Water Sensitive Urban Design (WSUD) features such as Sediment tanks, Bio-filtration systems and WSUD street tree pits within the Shire has diversified the approach towards a more sustainable peninsula. The Shires Initiative to incorporate WSUD within its urban landscapes is a positive endeavour.

With use of new technology, such as Rockpave as a filtering materiel within the kerb and channel, has improved the functionality, maintenance and safety of street tree pits within the urban environment.

Project Description

Project Objectives – The WSUD had to improve the aesthetics of the urban landscape, convey and retard storm flows, reduce pollutant export of harvested storm water and reduce irrigation requirements.  It was proposed to seek a new type of WSUD elements within an urbanised landscape, to treat pollutants commonly found within stormwater runoff can include phosphorus, nitrogen, nitrates, suspended solids, a multitude of heavy metals and gross pollutants such as litter.

Barriers – The most important design considerations for tree pits were, selecting the right plant species for the proposed site, the hydraulic structure detail to ensure efficient filtration and no damage, necessary design measures that will minimise and threat to public safety, the catchment area and available space for treatments, selecting best filter material to ensure an appropriate infiltration rate of water through the media and the health of the plant can be sustained, identify existing services located near the site, due to the common placement of the tree pits (footpaths, shopping precincts, highly urbanised areas).

Innovative features – The design involved the collection of stormwater from the roadway through Rockpave treatment with kerb line to eliminate debris entering the WSUD filtration system (larger debris are collected at end of line GPT system), to feed filtered water to the sub-root structure of the existing trees. This process has controlled flows directly to the root structure and filter the stormwater to remove pollutants. This process has more effectively mimic the natural system by treating the stormwater upstream than for conventional approaches, which will provide a flow-down effect that benefits the entire catchment.

Project Outcomes – an innovative solution has been developed with the use of Rockpave within the kerb line to eliminate debris from entering the WSUD filtration system, which has eliminated on going maintenance issues within typical tree pit type structures in removing debris.

Costs/Benefits –  Significant benefits have been achieved in reduced labour maintenance cost associated with general ongoing cleaning of tree pits. Rockpave filtration system is cleaned on cyclic period with general street cleaning of the roadway.