Projects, Sewer, Sewer rehabilitation, Water

Sewer assessments helping to manage risk

Moree Plains Shire Council in the North West Slopes region of New South Wales is currently undertaking inspections, risk assessment, and maintenance of its sewer network to assess the condition of these assets as part of its major asset management strategy.

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Roland Heatley, Water Services Manager (left), and Anub Nair, Water and Waste Technical Manager.

By adopting a more strategic approach to maintenance, the council aims to reduce unplanned maintenance requests, and the overall costs of annual maintenance. These assessments will help it better manage the full lifecycle costs of the sewer system, while still providing a high level of service.

This is the first time the council is completing condition scheduling for its whole network, which includes around 112km of sewer mains comprising 83km of gravity mains, 21km of rising mains, 2km of pressure mains, and 6km of vacuum mains.

Moree Plains Shire Council Water Services Manager Roland Heatley said the program is something new for the council and aims to look at the whole network to reduce maintenance costs and allow the council to take advantage of current technology.

“Condition assessment is an investment for these valuable community assets. It’s also an investment in managing risk. Knowing the structural condition of your assets will allow you to avoid emergencies, prioritise repair and replacement projects, and plan for the long-term future.

“An analysis of the data and information helps determine structural and operational issues, and performance of the system. Condition assessment also includes failure analysis to determine the causes of infrastructure failures, and to develop ways to prevent future breakdowns.

“Condition assessment enhances the ability of the council to make technically sound judgments regarding asset management.”

Assessing the network

In 2006, 25km of sewer mains were cleaned and a CCTV condition assessment was completed. Another 46.8km of sewer cleaning and condition assessment will begin in the last quarter of the 2016/2017 financial year.

“The major flood of 2012 has meant that the majority of the sewer requires heavy cleaning to get rid of the built up silts and gravel,” Mr Heatley said.

“On average, one CCTV crew can clean and condition assess around 400-600m of sewer main each day. For the current project, we expect it to take 80-90 days (15-18 weeks) to clean and condition assess the 46.8km of mains.

“We have also condition assessed half of the network’s sewer pump stations, and the remaining will be completed next financial year.”

Using technology to identify problems

The inspection of the conduits is being completed by CCTV cameras in accordance with the Water Services Association of Australia (WSAA) Conduit Inspection Reporting Code of Australia.

The computer software WinCAN V8 is also being used to undertake video recording and defect coding of all inspected mains, as well as reporting on the condition of the sewer network for evidence of inflow and/or infiltration, and the identification of defects.

The technology used by the council aims to provide a number of benefits including:

  • Rapid and thorough documentation of critical inspection work
  • A tilt/panning head camera with high resolution colour camera modules with 90˚ picture view has allowed for a more complete view of the main
  • The Combination Jet Vac unit has allowed contractors to conduct heavy cleaning when required
  • EZITRAK Easement Reel has allowed for access to more difficult jobs

Moree Plains Shire Council Water and Waste Technical Officer Anub Nair said these technologies allow the council to identify issues and maintenance requirements and therefore, prioritise resources across the network to provide reliable sewerage infrastructure for the community.

“The report provides details of the location and characteristics of reportable features including defects and features of interest, together with details necessary to define the details of the inspection in accordance with the requirements of the code.

“The inspection report includes a grading of the structural and service condition of the asset determined in accordance with the code,” Mr Nair said.

Condition assessment that has been completed so far on 25km of sewer mains has helped the council identify the following issues and maintenance requirements:

  • 7km of sewer main needs relining and around 20 dig-ups are required
  • The collapse of 225mm concrete pipe with three collapsed pipe sections and two joint dislocations
  • The affected sewer line is around 125m of 225mm diameter concrete pipe with three manholes which are 5.5m to 5.7m deep with 14 household 150mm sewer connections
  • Unrepairable pipe and unstable ground above the sewer main and fourteen 5.5m excavations for household connections involved
  • Pipe bursting 225mm mains and replacing with 225 PVC pipe offsetting a shallow main and connect 13 household connections to manhole

“Manhole condition assessment has been completed for half the network, currently a contract is been signed for relining 40 manholes per year for the next three years,” Mr Nair said.

Relining of sewer mains contracts will be tendered out within this quarter for relining 3km of sewer main in this current financial year, with an additional two 6km sections in the next two financial years.

Inspection providing vital information

Mr Heatley said asset management plays an important role in the community, as the condition assessments provide critical information needed to assess the physical condition and functionality of a wastewater collection system, and to estimate its remaining service life and asset value.

“After the field inspection, pipe defects are classified using a standard coding system and pipe condition is assessed using a systematic method to produce consistent, useful information,” Mr Heatley said.

“Following data analysis, condition assessment information is used to make estimates of a pipe’s remaining useful life and its long-term performance, and to make decisions about pipe rehabilitation, pipe replacement, and/or further inspections.”

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