Drainage nets

The City of Kwinana’s drainage nets made social media headlines after images of the drainage nets went viral in April 2018. Since this time, the City has been inundated with phone calls and emails worldwide to find out more about this simple, yet effective solution to minimise the City’s environmental impact on the drainage network.  

Installation of Drainage Nets 

The City of Kwinana installed two drainage nets at the piped drainage outlets located in Henley Nature Reserve, Leda, in March 2018. The City also installed another three drainage nets during the 2019/20 financial year at the drainage outlets located at Orelia Oval (Lot 501 Christmas Avenue), Sloans Reserve and Lot 766 Oakley Road.

The drainage nets were installed at the outlets of concrete drainage pipes (450mm and 750mm diameter) to prevent pollution of the nature reserve by intercepting and collecting solid waste conveyed by the piped drainage system. The solid waste entering the piped drainage system from various residential road reservations mainly consisted of food wrapping, drink bottles, cans, organic waste including tree leaves and other domestic waste generally found in urban road network.

The drainage nets were designed and supplied by Urban Asset Solutions and installed by the City of Kwinana. The supply and installation cost of the drainage nets were approximately $10,000 each. This also included the cost of civil upgrade works, ie improvement of access to the drainage nets.

Ongoing Maintenance of Drainage Nets and Waste Collection 

The drainage nets are inspected regularly and the materials collected in the nets are removed off site. The type of waste collected by drainage nets usually includes leaves, sand, plastic bottles, cans, rubber balls and the odd items such as keys. A two man drainage maintenance crew inspects the contents and cleans out the nets while the loader will measure the nets and its content for data collection for operational purposes. The net is then taken to a tipper truck at which point its contents is unloaded and inspected and recorded, again for data collection for operational needs.

Between the months of May 2018 to June 2019, waste was collected and removed 11 times from both of the two drainage nets, with more frequent collections during the rainy season. It took a two man crew four hours to complete each collection. During these collection a total of 1,690kg (1.69 tonnes) of waste was removed from the two drainage nets. The most waste collected in one nets were 26kg (750mm drainage net) and 100kg (450mm drainage net).

The contents removed from the drainage nets are taken to  a waste management site where the material is disposed and then later collected in bulk and transported to a waste management facility for sorting.

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