Local impacts of new outfall

Water Services - Wastewater

Image of men working in outfall pipe. Local impacts of the new outfall

Key council wastewater projects

As our city continues to grow, we are planning ahead to ensure that our wastewater network and treatment systems will continue to meet
our needs.

The city will spend a total of $112m between 2004/05 and 2013/14 on upgrading, expanding and improving the efficiency of the Rosedale wastewater treatment plant. A further $156m will be spent between 2004/05 and 2013/14 on upgrading and expanding the pipe network and pump stations.

The construction of the new outfall is a key project that will further improve the efficiency and capacity of our treatment plant. It will be one of the largest single projects our council has undertaken, with an estimated cost of $75million (at 2004 costs).

We expect to let the contracts for the project early in 2007 and construction is likely to start in 2008. A tunnelled option for the entire on-shore section was initially chosen to allow gravity flow and avoid the need for pumping, and to avoid serious disruption during construction.

After Auckland Regional Council consents were granted for this route, further geotechnical investigations indicated difficult ground conditions along the eastern section of the on-shore route could result in excessive land settlement above the tunnel, given the tunnelling technology available at the time.

A change in the proposed construction method was then proposed to give council the option of bringing the tunnel closer to the surface on the eastern section to where the ground is less susceptible to settlement. This would see construction of this section by open cut trenching and sub-surface pipe-jacking along sections of Maxwelton Dr and Ramsgate Terrace, and Sidmouth Street.

Further geotechnical and engineering investigations are continuing as our engineering staff progress engineering and traffic management aspects of the project, in order to find the most cost-effective construction method while minimising the effects on the local community.

Impacts on the community

Because of the magnitude of the project, it is inevitable there will be some disruption and inconvenience to the community.

However our engineering staff will draw on our experience of other major works, such as the installation of the new trunk sewers in Browns Bay, to ensure any impacts are minimised and those most directly affected kept up to date with developments.

If parts of the eastern section of the tunnel are constructed by open cut trenching, properties along Maxwelton Dr and Ramsgate Tce could have limited street access. It is possible that between four to six properties may have limited access at any one time for between six to eight weeks as a four metre wide trench is dug.

During construction we will take every measure possible to minimise these effects and ensure those most directly affected by the work are kept informed about the project.

Our engineering staff are happy to discuss the possible construction methods and the likely impacts with you.