Western Harbour Tunnel Water Treatment Plant

On the NSW Government’s Western Harbour Tunnel project, ACCIONA partnered with SciDev to deliver sustainable water treatment solutions that support environmental goals and regulatory compliance. The 6.5 km dual three-lane tunnel generates large volumes of groundwater during excavation. To manage this, three advanced temporary Water Treatment Plants (WTPs) were installed—two at the northern portal and one at the southern.

Key design features of the WTP which make it unique include;

• The WTPs operate 24/7, treating up to 35 L/s at the southern portal WTP and 15 L/s at each of the plants at the northern portal.
• The treatment process includes sedimentation, clarification, filtration, chlorination, activated carbon polishing, nitrate removal, and solids handling.
• MaxiFlox® flocculants ensure effective chemical conditioning for water clarification under variable feed conditions.
• Existing assets, such as a filter press, were repurposed to reduce waste and cost.
• The WTPs were designed to operate automatically with minimal maintenance required.

Treated water is reused on-site for dust suppression, wheel washing, and workshop use, reducing demand on local water resources. The system supports a circular water strategy and includes real-time monitoring and automated controls to meet Environmental Protection Licence standards.

Once commissioned, the system was handed to the construction team, with automation enabling easy operation. This integrated, sustainable approach positions the project as a model for environmentally responsible infrastructure delivery.