Molonglo Valley Interceptor Sewer

Icon Water has just begun work on an important improvement project that will rehabilitate a large diameter sewer main located adjacent to the suburb of Coombs. The works will be a combination of night and day works and Interflow Pty Ltd have been engaged to undertake the work.

Pipe Lining

The method to be used for MVIS rehabilitation is the spiral wound lining method with Rotaloc liners. The Rotaloc liner comprises a continuous profiled strip of PVC that is progressively wound into the existing pipeline by the winding machine. The edges of the PVC strip are interlocked by the winding machine as it rotates and moves along inside the host pipe. (Below: winding machine with live flow into the sewer pipe)




















 Hours of work for the project

Because this is the main sewer for the area, the works will need to occur mainly at night when the flows are at their lowest. It is expected that some noise will be generated by the installation of machinery during the process. This timing for the work will ensure that the workers who undertake the job are able to access the works area safely. The night works will occur during the hours of 12am and 7.30am and will potentially cause, as said above, some mininal noise and odour emmissions.

There will also be some day works which will potentially create an increase in traffic in the vicinity of the works. These works will involve some modifications to the ground around the sewer access chambers along the respective sewer line. The majority of the disturbed areas will be restored using topsoil and a dryland grass seed mix. Interflow and Icon Water will make every attempt to minimise disruption to the community while the work is being undertaken.


Background to the MVIS

Molonglo Valley Interceptor Sewer (MVIS) was built between 1973 and 1976. MVIS is comprised of 1980mm diameter precast reinforced concrete pipes laid in the trench on a 1 in 483 grade. MVIS is one of the most critical trunk sewers in Canberra. It contains the flows from Tuggeranong Sewer Tunnel, Duffy Trunk Sewer, Weston Creek Sewer and Main Outfall Sewer (MOS). The flows from MOS, Duffy Trunk Sewer and Weston Creek Sewer enter MVIS via a vortex drop structure at Maintenance Hole 1 (MH1). Woden Valley Trunk Sewer (MVTS) and Molonglo Trunk Sewer enter MVIS at MH6 before aqueduct. The length of MVIS between MH1 and MH 6 is approximately 850m.


The MVIS is one of the most critical trunk sewers in Canberra’s sewerage network and therefore the substantial deterioration of the pipe condition already in place and the high profile of the proceeding high density residential development of surrounding areas, it is important to implement construction phase of the rehabilitation works of the sewer and the Fred Reardon by-pass pipe to ensure corrosion does not reduce the life expectancy of this asset.


The main purpose of this project is to ensure that the required level of sanitation is provided for the community and the main driver for this project is renewal.
















Feedback is welcome!

There are a number of ways that you can contact us if you want to talk to someone about this project - contact general inquiries on 6248 3111 (select option 3 during business hours) or you can email If you want to speak to someone out of hours, call faults and emergencies on 6248 3111 and select option 1 (this is a 24 hour number).