Northside Storage Tunnel

The Northside Storage Tunnel improves water quality in Sydney Harbour by storing wastewater and stormwater that would have otherwise overflowed into the harbour during heavy rain.

The wastewater system is built with overflow points that act as 'relief valves' when pipes reach their capacity. The largest of these overflow points are at:

  • Lane Cove River West
  • Scotts Creek
  • Tunks Park
  • Quakers Hat Bay.

How much water can the tunnel hold?
The tunnel can store almost 500 million litres of water that's collected from the four overflow sites. It's then transported to North Head Wastewater Treatment Plant. 
Diagram of Northside Storage Tunnel route from Lane Cove to North Head

The tunnel stretches 16 km from Lane Cove to North Head.

Key facts

  • The tunnel's diameter ranges from 3.8 m to 6.6 m.
  • The tunnel starts 40m below sea level west of Lane Cove River and runs 16 km east to end 100 m below sea level at North Head.