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Molonglo Valley Sewer

Molonglo Valley Sewer Ventilation and Odour Control

The Molonglo Valley Interceptor Sewer (MVIS) is a two (2) metre diameter sewer that transports a significant amount of Canberra’s wastewater to Lower Molonglo Water Quality Control Centre, Canberra’s wastewater treatment plant. Population and density growth means we need to continue improving our sewerage infrastructure to ensure it can:  

  • Handle Canberra’s projected population increase.  
  • Function without causing odour that impacts the surrounding community. 
  • Meet its design life by providing ventilation that reduces the likelihood of corrosion. 


Corrosion of sewers is caused by hydrogen sulphide gases that are naturally released from wastewater. If left in the sewerage network, the gases oxidise on exposed concrete surfaces, forming sulphuric acid and weakening the concrete structures.  

We are in the process of renewing ventilation and odour control assets that service the MVIS and related sewer infrastructure. This is being delivered through a staged program of works: 

Stage 1: North Weston Ventilation facility – this work has recently been completed.  

It involved the construction of a new 500 metre long 1.2 metre diameter foul air pipeline using glass reinforced plastic piping. A new fan house building has been constructed on Ryan’s Hill, along with an 18-metre ventilation stack designed to provide optimal air dispersion. These new assets are constantly monitored via our remote telemetry system. It will operate automatically in conjunction with other existing sewer ventilation facilities. 

Stage 2: Odour Control Units No. 1,2,3,4 – Odour control units (OCU) will be built along the MVIS.  

These OCUs use special filters that absorb hydrogen sulphide and other gases. They will protect future residents from odour impact while preventing sewerage corrosion. 

Stage 3: Odour Control Unit No. 5 – we are investigating the need for an additional odour control unit.  

This OCU will likely be constructed adjacent to the existing North Weston Ventilation facility.