Designing a gross pollutant trap to protect wetlands from upstream urbanisation

Maryland Creek GPT Design

In an increasingly urbanised environment, maintaining environmentally sensitive water catchments is especially important within our towns and cities. Recognising this, the City of Newcastle engaged our team to design a gross pollutant trap (GPT) at Maryland Creek. Their goal? To reduce the level of gross pollutants and coarse sediment from the increasingly urbanised upstream catchment ending up in the downstream wetlands.

Initially, our team developed a water quality model to quantify the expected levels of pollutants and how large the collecting bay would need to be to align to desired maintenance frequency. Further hydraulic and hydrological models were then used to determine the impact of the device on site flood behaviour and upstream flood levels. Once the impacts were modelled, we ran a design process to assess different concept device layouts and placements with regards to functionality, cost, accessibility, flood impacts, and aesthetics. We then completed a detailed design of the final device, an online GPT, for implementation. The major challenge for the project was ensuring that the GPT design was able to deal with significant flooding events and is able to protect the downstream wetlands.

Now operational, the GPT has seen no problematic upstream or downstream impacts in flood events and has succeeded in protecting the wetlands.