Bio–Filtration Raingarden, from Design to Built

Biofiltration Raingardens are “gardens with purpose”. They improve stormwater quality through filtration media and are considered a sustainable stormwater management device that can replace hard-engineered stormwater infrastructure while also meeting regulatory obligations.

Meeting the regulatory obligations is often the first consideration when implementing stormwater management solutions and undertaking best practicable options analysis. However, a change in focus to address specific contaminants of interest requires a different approach to achieve compliance with ICMP objectives and other obligations. Raingardens can provide the flexibility that is required and become the device of choice with respect to changes in focus of contaminant removal.

Raingardens have often been used as a centralized or decentralized stormwater management device and an important tool for water sensitive design. Raingardens can provide stormwater quality treatment, runoff attenuation, groundwater recharge and intangible value such as potential benefit human health and welling being whilst providing greater connection between the urban and natural environment.

This paper discuss various design methodologies, applications and potential challenges throughout the raingarden design phase and highlights some of the additional challenges that arise during construction by presenting examples from several projects in the Waikato and Auckland Regions. The presented case studies will expose the challenges faced during the construction phase and how these can be overcome during design evolution. . Challenges include:

• Design to target specific pollutants
• High water tables
• Media selection
• Outlet Design
• Construction methodology
• Maintenance requirements