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We dispose of treated wastewater from the Woodman Point and Point Peron wastewater treatment plants via the 24km Sepia Depression Ocean Outlet Landline.

The Sepia Depression Ocean Outlet Landline (SDOOL) is also used for the disposal of treated wastewater from the Kwinana Water Recycling Plant, BP Refinery, CSBP Limited, Perth Energy and Perth Power Company. It extends 4km offshore from Point Peron into the sepia depression, a 20m deep channel running parallel to the shore.

The landline has carried treated wastewater from wastewater treatment plants since 1984. In 2004, in accordance with the Environmental Protection Act 1986, we were granted approval by the Minister for Environment to discharge treated wastewater from selected industries.

We have engaged an independent consultant, Oceanica Marine and Coastal Specialists, to conduct the program.

Regulatory framework and reporting

Our environmental approval allows us to discharge up to 30 million litres per day of industrial wastewater via the landline.

As part of our environment approval, the quality of wastewater must meet the:

  • ANZECC/ARMCANZ (2000) 80% species protection guidelines for bio-accumulating toxicants at the point of discharge
  • ANZECC/ARMCANZ (2000) 99% species protection guidelines for toxicants 100 metres from the diffuser.

Cobalt is an exception, where the 95% species protection guideline needs to be met at 100 metres from the diffuser.

The program is conducted under Ministerial Conditions set by the Minister. We produce an annual report outlining the monitoring and management activities for SDOOL, which is also provided to the Environmental Protection Authority.

Environmental monitoring

We have developed a Monitoring and Management Plan to ensure that both the ecological and social values for marine waters in the vicinity of the Sepia Depression ocean outfall are maintained. The plan details monitoring required to evaluate the environmental effects of discharging treated wastewater into the Sepia Depression. It also describes the management responses that may be implemented if guideline trigger levels or Environmental Quality Standards are exceeded.

The plan compliments the Perth Long Term Ocean Outlet Monitoring program, which aims to monitor any potential problems resulting from Perth’s Ocean Reef, Point Peron and Swanbourne outfalls.

Contact details

The SDOOL program team comprises a multi-disciplinary group of scientists responsible for carrying out monitoring and analytical tasks specific to their area of expertise.

For further information about the program please contact us on 13 13 75.