An Alternative to Stormwater Ponds

A stormwater pond was constructed by a private development company in 2004 at Carol Lee Place, Albany Heights, Auckland in order to meet stormwater quality, extended detention and peak flow attenuation objectives for a 2.97 hectare residential catchment. The pond has since failed to perform to the required standards and is undersized to achieve the required stormwater management objectives and meet consent conditions. In 2010 the former North Shore City Council undertook a detailed evaluation of the existing pond and identified a number of options for its redevelopment. The main constraint was limited space within the existing drainage reserve for the construction of a fully compliant device. Five alternative options were identified and assessed, with Option 4 determined to be the best practicable option. This concept incorporated a raingarden overlaying an underground modular crate-type detention tank system. This solution is a unique device that is able to achieve the required stormwater management objectives to the greatest practicable degree. The concept has since gone through a detailed design process and planned for construction in March and April 2012. It is anticipated that the system will have wide-reaching implications and could be replicated in similar situations throughout the Auckland region and beyond.