D&C of the low point sumps on the Westconnex M4-M5 Link Tunnels Project


WestConnex, the largest road infrastructure project in Australia, is a 33-kilometer motorway network that will be delivered in 4 stages. The New M4, opened in July 2019, the M8, opened in July 2020, the M4-M5 Link Tunnels, are due to open in 2023 and the Rozelle interchange, is also due to open in 2023.

RSGx are performing scope on the third stage of the project, the M4-M5 Link Tunnels. The M4-M5 Link Tunnels will consist of 7.5km of tunnels, linking the New M4 at Haberfield with the M8 at St Peters, with connections to the Anzac and Iron Cove bridges via the Rozelle Interchange.


RSGx’s scope consists of the detailed design, supply, installation and commissioning of the tunnel’s common gravity drainage system, the Low Point Sump (LPS). Each LPS is separated into two compartments, the Minor Flows (MF) sump and the High Flows (HF) sump connected by an under/over weir. The Northern LPS pumps will pump to the tunnel high point and water will flow by gravity to the Southern LPS; Southern MF pumps will pump directly to the WTP inlet buffer tank; Southern HF pumps will pump to the surface holding tank.

RSGx are responsible for the design, manufacture, supply, installation, testing and commissioning of all mechanical and electrical equipment to be installed in each low point sump pumping station, including but not limited to:

  • Hydraulic installation: submersible pumps, pipework and instrumentation;
  • Ventilation installation: supply and exhaust air network;
  • Fire Suppression installation: hydrocarbon detection and foam suppression;
  • Electrical installation: control panel, cabling, lighting;
  • Control and Monitoring installation: PLC, I/O schedule

Read more about the project in the project case study, which can be downloaded through the below link.