Contaminated surface water

Directing stormwater, rainwater or groundwater to our wastewater system can overload it, causing overflows.

All customers must manage excess water on site by using bunding, stormwater drainage channels and roofing.

Discharge from open area (contaminated surface water)

We understand it's not practical to roof an area in some circumstances and the contaminated run-off can't be directed to the site stormwater system.

In these situations, we may permit only the first 10 mm of rainfall collected in a first flush system to be discharged to sewer. You must have our written approval to discharge this first flush volume to sewer.

In all cases the wastewater first flush volume must be treated to meet our acceptance standards before discharge.

We'll consider an application to discharge rainwater from contaminated open areas. However, you may need to provide:

  • evidence why the area can't be roofed to direct the rainwater to the site stormwater drainage system
  • a report from the EPA or local council confirming the run-off is contaminated and can't be directed to the site's stormwater drainage

Discharge of contaminated surface water from an open area
Open area < 50m2 Open area > 50 m2
  • Install an approved first flush system designed to  capture the first 500 litres of rainfall and direct the rest to the stormwater drainage system

  • Install an approved first flush system designed to  capture the first 10mm of rainfall and direct the rest to  the stormwater drainage system

  • First flush volume to  be pumped to sewer at a rate not exceeding 0.3litres/second

  • Install an approved rainfall cut-off device and delay discharge of first flush volume to sewer for at least one hour after rain stops


  • Install a complete approved first flush system* in accordance with the manufacturer's specifications, designed to capture the first 10mm of rainfall, or more if specified, and direct the rest to the stormwater drainage system

*Fox Environmental Systems FF600

A first flush system for an area greater than 50 m2 

Typical set up for first flush system

To see what a typical set up looks like, view  Typical first flush system for open areas greater than 50 m2.  

Excavation and construction 

We won't permit you to discharge groundwater and surface water collected during excavation and construction to our system. You must treat and discharge it to the site stormwater drainage system.

Talk to the EPA or your local council about their requirements.