The Case of the Strange Lane Cove Hum

Over the last couple of weeks In the Cove followers have reported hearing a strange hum.  The humming can be heard at night and quite frequently in the mornings around 5.30 am or 6.30 am.  Originally local residents thought it was the Chatswood Metro Dive Site.  ITC undertook further investigations.  We have not found the source of the hum but we have found the source of an odour complaint near St Ignatius School Riverview.

Chatswood Metro Dive Site

In the Cove asked Transport for NSW to advise if the hum was related to the Chatswood Metro Dive Site.

A Transport for NSW spokesperson said:

There is no work being completed on the Sydney Metro Chatswood dive site that generates the noise described.

Noise monitoring is regularly undertaken during out-of-hours works. Sydney Metro’s tunnelling contractor advises after hours works within the site have been found to be inaudible from outside the site.

Extensive acoustic mitigation measures have already been installed or are planned for the construction site, including large acoustic sheds and noise hoardings.

Northern Suburbs Ocean Outfall Sewer

During a visit to Burns Bay Reserve, ITC spotted work on the Northern Suburbs Ocean Outfall Sewer.  This is a tunnel that is over 26 kilometres long and extends from Parramatta all the way to Manly.

Sydney Water’s contractor, Interflow, is cleaning and repairing a 1.3-kilometre section of the tunnel between Lane Cove River and Tambourine Bay Road Riverview. A spokesperson for Sydney Water stated this work is essential to ensure they continue to protect public health and the cleanliness of Sydney harbour.

Work started in Januaru 2017 and, to date, Sydney Water/Interflow have cleaned and repaired the tunnel between Tambourine Bay Road and St Ignatius College Riverview. They are now repairing the tunnel between St Ignatius College Riverview and Lane Cove River. This work is done by two crews accessing the NSOOS at three locations:

Sydney Water expects to complete this work by early next year. Once complete, their work crews will commence working on the tunnel east of Tambourine Bay Road to Woodford Bay Reserve.

Is Sydney Water/Interflow responsible for the humming noise?  ITC thought we were on to something when we saw the machinery in operation at Burns Bay Reserve.  See our video below.

Apparently this is not the cause of the humming noise.  As spokesperson for Sydney Water advised:

“Sydney Water’s contractor Interflow’s work hours are between 7 am and 6 pm Monday to Friday and from 8 am on some Saturdays. Fans are turned on at 7 am at Burns Bay Reserve and at 331 Burns Bay Road, Lane Cove West. A pump is turned on a Burns Bay Reserve from 7.30am when work crews enter the tunnel. If out-of-hours work is required, Interflow will notify all residents within a 200-metre radius of the site.

The environmental approvals for this project prohibit Sydney Water’s contractor Interflow from operating any equipment outside the approved working hours of between 7 am and 6 pm Monday to Friday and 8 am to 1 pm Saturday. When our equipment is in use, we have the following measures in place to minimise the impact of these works on the surrounding community:

  • Acoustic barriers between the work site and the nearest residents; and
  • The pump in use at Burns Bay Reserve is located within a sound-proof barrier.”

The mysterious case of the humming noise continues.  Have you heard it lately?

On the Nose

While ITC may not have discovered the reason for the noise, we did discover a possible answer to another question raised by a Riverview resident.  They were concerned about a strong sewerage smell each morning near the roundabout before the entrance to St Ignatius College.

A Spokesperson for Sydney Water advised:

“To ensure the safety of our crews working in difficult conditions up to 40 metres below ground, we have in place a carefully controlled ventilation system whereby we blow fresh air into the tunnel at the three work sites.

We also have in place gas monitors that continually monitor odour-causing gas levels, deodorisers to minimise any unpleasant smells from the tunnel as well as an odour-control unit at Burns Bay Reserve that filters the air released from the tunnel.

Sydney Water takes all odour complaints received from the community very seriously and will proactively investigate the cause. The wastewater system is extensive and odour can be caused by any part of the wastewater network, which includes infrastructure managed by Sydney Water as well as privately owned wastewater pipes. While we have controls in place to minimise any odours that may be caused by our work, there are other odour-causing factors that we cannot control, such as the weather.  As part of our work within the NSOOS, we are currently undertaking extensive odour logging at St Ignatius College, where we open access lids to enter the tunnel. Preliminary results have shown no detectable levels of the most obvious odour-causing gas, hydrogen sulphide. However, we will continue to monitor the situation.”

If you have a noise or smell complaint relating from the work please contact the  community relations team on 1800 233 076 or email [email protected] For 24 hour service disruptions or emergencies please call 13 20 90.

History of the Northern Suburbs Outfall Sewerage

The NSOOS runs along the north side of the Parramatta River collecting wastewater from as far west as Blacktown and transporting it to the North Head Wastewater Treatment Plant in Manly. It was constructed progressively between 1916 and 1933 and collects about 25% of Sydney’s wastewater. It was an incredible undertaking at the time tunnelling through rock and cost the lives of three men.  The project was called an engineering marvel for its time.

Credit: Sydney Water / WaterNSW Historical Research
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