Development of a Low Cost High Efficiency Stormwater Litter Trap

Every summer New Zealand newspapers are filled with stories about the amount of litter and debris on our beaches. The major source of this is urban stormwater systems, where every catchpit eventually drains to the sea.

This paper discusses the process and development of a catchpit insert specifically designed to focus on gross pollutants. The other focus of the design was to make a stormwater litter trap that could easily be hand maintained and is affordable; therefore promoting greater uptake by the public.

Developing a stormwater management device is not easy; each contaminant in stormwater has its own removal issues. The contaminant removal issues associated with gross pollutants are as the following:

• Size of the contaminants
• Variable buoyancy
• Decay and release
• Transported load and structural and maintenance implications
• Gross pollutants do not exhibit a first flush phenomena

The paper also discusses the process and observations of the laboratory and field testing and how this a required element in the development to ensure the device would perform in a range of applications and weather conditions.