Project goal: 

Undertake a trial to better understand the implications and impacts of Gross Pollutant Traps (GPTs) on our drainage network.



Delivery Date:


What are Gross Pollutant Traps?

Gross pollutant traps (GPTs) are structures which physically trap contaminants such as litter, debris and coarse sediments in stormwater drainage systems before they enter rivers or the ocean.

Litter includes human derived rubbish such as paper, plastic, styrofoam, metal and glass. Debris consists of organic material including leaves, branches, seeds, twigs and grass clippings. Coarse sediments are typically inorganic breakdown products from sources such as soils, pavement or building materials (Stormwater Management Manual for Western Australia, 2007).

GPTs are a cost-effective solution for trapping the contaminants from stormwater drainage systems and reducing the maintenance frequency.


What’s happening? 

We are investigating how we can address the issue of plastic reaching the ocean through stormwater drains. 

In order to do so, we are undertaking a trial to better understand the implications and impacts of Gross Pollutant Traps (GPTs) on our drainage network, by exploring:

  • Operational requirements (inspection, maintenance, cleaning and disposal);
  • Capital and operational costs; and
  • Hydraulic function and water quality. 

The trial will run for a period of two years, and will be monitored closely according to the above parameters. Following this, a report will be compiled to assess their effectiveness and potential future use. 

Where is this happening?

 After initial investigations, Herdsman Lake and its catchment was identified as the ideal trial site. The trial at Herdsman Lake includes:

  • Two floating litter traps
  • One floating litter boom

Please refer to the map for the location of the work and the sites where the GPTs have been installed.

When is this taking place?

Construction of the three sites and installation of the traps and boom was completed between February and June 2021.

The trial will now run for a period of two years.  
Additionally, we are planning to revegetate one of our open drains within the Herdsman Lake catchment and convert a second one into a vegetated living stream by 2022.


How will this impact the community?

Now the GPTs have been installed, the community will be able to see the GPTs capturing the gross pollutants. The only noticeable activity after installation will be during maintenance periods, when we will check and, if necessary, clear the litter, debris and/or coarse sediments.

Who can I contact?

Contact us

Carley Robbins - Community Engagement Advisor

Phone icon (08) 9420 3020

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