Repairs to various connecting tunnels in the NSOOS

Sydney Water’s contractor, Metrocorp Technologies, was recently awarded a $5 million contract to repair several tunnels that form part of the Northern Suburbs Ocean Outfall System (NSOOS).

This repair work will restore the tunnels close to their original structural condition and improve their operating performance and reliability. The work will also reduce the risk of overflows and ensure a high standard of wastewater services to customers in Sydney’s northern suburbs.

Repairs will be done on the following five rock tunnels, whose wastewater flows into the NSOOS:

• Dorset Road Tunnel: 232 metre section between Coolawin and Dorset Roads, Northbridge. This sewer is mainly in a residential area and has varying degrees of deterioration.
• West Lane Cove Tunnel: 2,909 metre section between Porters Creek Landfill and Recycling Centre, off Wicks Road, Macquarie Park and the corner of Pittwater and Coxs Roads, North Ryde. Part of this tunnel traverses the Lane Cove National Park.
• Newport Low Level Submain Section 2 Tunnel: 865 metre section from the corner of Avalon Parade and Barrenjoey Road, Avalon and the end of Allan Avenue, Bilgola Beach. The start of this section of work is located near the Avalon Beach Surf Life Saving Club and ends near Bilgola Beach. Work will be done during the winter months to reduce the impact during summer time.
• Porters Creek Tunnel: 468 metre section between the corner of Ryrie and Morshead Streets, North Ryde and Council land off Epping Road, North Ryde.
• Mowbray Point Tunnel: 299 metre section between The Bulwark, Castlecrag and Rockley Street, Castlecrag.

The tunnels are located near the coastline, with the exception of Porter’s Creek Tunnel. The majority of work will be done on roadways, footpaths and public reserves. Some maintenance holes are on private land and other private properties will need to be accessed to do the work.

Work will be done during the day and involves setting up site compounds, cleaning and repairing inside the pipe (shotcrete coating), silt and debris removal, providing ventilation and restoring maintenance holes. Crews will enter the sewer via maintenance holes, and do their work in flowing wastewater. Trenchless technology will be used to line the pipes, so minimal excavation will be done.

Work on this project should start the last week in July 2011, and take nine months to finish, weather permitting. Work will occur in the local government areas of Willoughby, Ryde and Pittwater.

The tunnels must remain in use while repair work is being done. Repairs will protect the interior from deteriorating further, and help avoid the need for extensive structural repairs in the future. The tunnels are up to 2.4 metres high and 1.5 metres wide.

Work hours will be:

7 am to 6 pm, Monday to Friday
8 am to 1 pm on Saturdays, if required.

Affected residents will be advised before work begins. Residents may notice an increase in noise, possible odour and vehicle movements during the work. Appropriate safety and environmental controls will be in place at all times.

There will be no disruption to water or wastewater services. When work is complete, Sydney Water will consult with Councils to ensure work areas are restored as close as possible to their original condition.

This essential repair work is part of Sydney Water’s $560 million SewerFix program to improve the wastewater system and protect public health and the environment.