Northern Suburbs Ocean Outfall Sewer (NSOOS)

Our 2024 Christmas holiday shutdown will start from close of business on Friday 20 December.

We'll return to work on Monday 13 January 2025.

Sites will be locked, security cameras will remain operational, and there will be random inspections throughout the holiday period.

We previously advised that we would finish our work at these locations in late 2024.

At the time we advised this estimated end date, we had insufficient information on other Sydney Water work that required 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've since identified additional work from 2023 and early 2024 in Cremorne, Mosman and at the North Head Water Resource Recovery Facility that requires continued access to the NSOOS tunnel at these sites.

• A project to remove silt from the Northside Storage Tunnel (NST) access decline and wet well areas at the North Head facility is expected to start in mid-2024. This will require removing the NSOOS flow diversion into the NST. It's estimated that the current NSOOS work in Cremorne and Mosman will be delayed by 3 to 4 months in early 2025 while the work occurs in the NST wet well area at the North Head facility.
• 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 3 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 started and is in the early concept design phase. Our technical teams have yet to determine access requirements into the NSOOS tunnel.

In light of this, we've revised our expected end date 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.

Please note our Christmas shutdown will start from close of business on Thursday 21 December.

We'll return to work on Monday 8 January 2024.

Sites will be locked, security cameras will remain operational, and there will be random inspections over the holiday period.

Critical Sewer Solutions, a joint venture of Metrocorp Technologies and Interflow in partnership with Sydney Water, rolled out the red carpet at their Quakers Hat Bay NSOOS rehabilitation worksite on Saturday 15 October.

It was a great day, where we shared with residents our project's scope of work, what a typical day is like for crews and our challenges.

Repairs to the NSOOS started between Brightmore Reserve, Cremorne, and Quakers Hat Bay, Mosman, in mid-2021.

Our work on the NSOOS at ANZAC Park, Cammeray, involves close cooperation with the ANZAC Park Memorial Community Garden.

After heavy rains between March and June, Metrocorp Technologies offered to supply and spread coarse gravel inside the garden to improve access. The recycled gravel used on Tuesday 11 October was chosen after consultation with North Sydney Council. Vehicle mats helped protect the park surface.

Work went smoothly despite more wet weather, and the pathway is now in much better shape. Garden volunteer coordinator and local resident Sue Wright greatly appreciated the effort.

All tunnel entry and ventilation sites will be closed on Tuesday 21 December, with work starting again on Monday 17 January 2022.

Sites will be locked, security cameras will remain operational, and there will be random inspections over the closure period.

Sydney Water engaged the highly experienced Critical Sewer Solutions (CSS) delivery team in late June 2021 to continue and finish rehabilitation works inside the NSOOS tunnel between Quakers Hat Bay, Mosman, and Brightmore Reserve, Cremorne.

CSS consists of specialist contractors Metrocorp and Interflow, companies that have a solid track record of working inside the NSOOS. They've successfully finished over 1.5 kilometres of tunnel rehabilitation at Lane Cove and Cremorne. This proven expertise will ensure the work is done safely and efficiently.

The CSS team looks forward to working closely with the community, ensuring minimal impact and disruption while we remove silt and debris, pressure clean and repair the tunnel.