Completion of our work in the Cremorne and Mosman area

We previously advised that we will complete our work at these locations in late 2024.

At the time we advised this estimated completion, we had insufficient information on other Sydney Water work that requires the ongoing access of the NSOOS tunnel using these sites. In addition, we used an arbitrary duration to forecast delays due to wet weather and other system events.

We have since identified additional Sydney Water work from 2023 and early 2024 in the Cremorne, Mosman, and North Head Water Resource Recovery Facility (WRRF) areas that require continued access to the NSOOS tunnel at these sites, including:

  • A project to remove silt from the Northside Storage Tunnel (NST) access decline and wet well areas at North Head WRRF is expected to commence in mid-2024. This will require removing the NSOOS flow diversion into the NST. It is estimated that the current NSOOS works in Cremorne and Mosman will be delayed by three to four months in early 2025 while the work occurs in the NST wet well area at the North Head plant.
  • More detailed repair work has been identified in the NSOOS tunnel between Quakers Hat Bay and the Spit Syphon at Mosman. We encountered some unforeseen tunnel conditions in this section of the NSOOS that slowed down our work. We also need to change our construction method to ensure the ongoing safety of our work crews inside the tunnel.
  • We experienced greater impacts from wet weather and tunnel system conditions than we originally anticipated.
  • Additional work has been identified to rehabilitate three large submains that flow into the NSOOS tunnel between Quakers Hat Bay and the Spit Syphon at Mosman. Planning the work on the Balmoral Slopes, Pearl Bay, and Spit Road submains has commenced and is in the early concept design phase. Our technical teams have yet to determine access requirements into the NSOOS tunnel this work will have.

In light of this, Sydney Water has revised its expected completion timing at these sites to be early 2027.

The early 2027 timing includes contingency for us not being able to access the NSOOS tunnel with wet weather and other network conditions.

It also allows for full demobilisation and restoration of the sites at

  • Brightmore Reserve, Cremorne
  • Brothers Memorial Park – Fifth Avenue, Cremorne
  • Quakers Hat Bay – Bay Street, Mosman
  • Upper Spit Road, Mosman

The Spit Syphon site will be demobilised with equipment and left secured for ongoing operational use by Sydney Water.

Share Completion of our work in the Cremorne and Mosman area on Facebook Share Completion of our work in the Cremorne and Mosman area on Twitter Share Completion of our work in the Cremorne and Mosman area on Linkedin Email Completion of our work in the Cremorne and Mosman area link