Reducing Stormwater in the Sewer, Byron Shire

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Inflow and Infiltration in Mullumbimby - Working towards a better system and healthy waterways

Working towards sustainable solutions for reducing stormwater in the sewerage system (inflow and infiltration) in the Byron Shire.

Council is committed to providing a sanitary sewerage system for the safety, health and well being of our community and conservation of our natural environment.

An improved sewerage and stormwater network is needed to better accommodate the area’s growing population and more extreme weather in the future.

A good sewerage network requires a combined approach from Council and community.

This process will help Council better understand the scope of inflow and infiltration in the Byron Shire area, assist with providing the most sustainable solutions and help to better plan for future infrastructure.


Working towards sustainable solutions for reducing stormwater in the sewerage system (inflow and infiltration) in the Byron Shire.

Council is committed to providing a sanitary sewerage system for the safety, health and well being of our community and conservation of our natural environment.

An improved sewerage and stormwater network is needed to better accommodate the area’s growing population and more extreme weather in the future.

A good sewerage network requires a combined approach from Council and community.

This process will help Council better understand the scope of inflow and infiltration in the Byron Shire area, assist with providing the most sustainable solutions and help to better plan for future infrastructure.


  • Structural relining of gravity sewer mains – Interflow’s process

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    29 Apr 2020
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    Byron Shire Council has engaged the services of specialist contractor Interflow to undertake various rectification works on the existing gravity sewer network throughout Mullumbimby.

    Since 1991 Interflow has installed over 2,500 kilometres of their structural liner (Expanda Pipe) in Australia. The minimum useful life guarantee of this product is 50 years. Interflow has a documented process that is strictly followed and certified by the site engineer to ensure the integrity of this new asset meets Council’s needs well into the future.

    The process is well trialled and tested with over 2,500km of this product being previously installed by Interflow.

    The relining process involves:

    • Initial cleaning via pressure water blasting of the existing gravity sewer main to remove all obstructions and dirt from the inner wall of the pipe.
    • CCTV inspection of the existing gravity sewer main to ensure the path is clear for installation of the new structural liner.
    • Insertion of the structural liner winding machine in the maintenance hole and connection of the liner to the winding machine.
    • Installation of the liner until it reaches the next maintenance structure.
    • Final CCTV inspection to ensure there are no defects or bulges in the liner.
    • Cut out and sealing of all property connections and sealing of both ends at the maintenance hole.

    Structurally relining a gravity sewer main typically takes between 1-2 days. This includes preparation of the existing main, installation of structural liner, cut out of all existing private properties, and connections at each maintenance hole.

  • Summary: 2019 Sewer Assessments - Mullumbimby

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    17 Feb 2020
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    • Flow monitoring was undertaken in the Mullumbimby sewer catchment which identified that inflow and infiltration was evident.
    • Further visual assessments, CCTV, and smoke testing were undertaken to confirm the condition of this portion of the network.
    • Assessments included 109 gravity sewer mains and 107 stormwater urban mains in addition to associated maintenance structures.
    • Assessments identified various assets requiring maintenance, rectification works, and/or renewal.
    • A risk analysis was undertaken of each asset so that Council can prioritise the highest risk assets for the recommended works.
    • The first scheduled works include:
    1. Structural relining of 27 sewer mains;
    2. Minor rectification of 27 sewer and stormwater mains, including various maintenance structures; and
    3. Reassessment of 26 sewer and stormwater mains (due to incomplete or obstructed original assessment).

    • These works are expected to commence in February 2020 and be completed by June 2020.

    • CCTV assessments of the remainder of the gravity sewer network will be on a priority basis.
    • Byron Bay and Ocean Shores will be assessed as the next two highest priority sewer catchments between February and June 2020.
    • The results from these assessments will enable Council to direct budget to Byron Shire's highest risk areas of the sewer network.
    • All rectification works on gravity sewer mains can be done with a structural liner, which is a quicker, more cost effective, lower risk option than replacement and has a lower impact on community (noise, dust, traffic etc).
    • Structural liners typically have a design life of at least 50 years.
    • Council is seeking a comprehensive understanding of the condition of its gravity sewer and stormwater networks to ensure their integrity and function are maintained so associated risks can be managed accordingly.
  • Smoke testing of sewer system in Mullumbimby to commence

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    09 Sep 2019
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    Image: Smoke testing, Interflow

    Images: Interflow

    Non-toxic, non-staining, and odourless smoke testing of Mullumbimby’s sewer system will commence from Monday 16 September to identify where stormwater may be incorrectly entering sewer pipes.

    Byron Shire Council’s Manager Utilities, Mr Cameron Clark said identifying and resolving leaks, defects and incorrectly installed stormwater connections into Council’s sewer mains will help reduce incidences of flooding or overflow on private property.

    Smoke testing involves the pumping of non-toxic, non-staining, odourless coloured smoke into a public sewer or manhole during dry weather. Smoke enters the sewer system and escapes through leaks, cracked pipes or incorrectly installed stormwater drains. Smoke may emerge from yards, roof gutters, pipes or street drains. The smoke is not flammable and will not cause any harm to people, pets or plants.

    Specialist contractor, Interflow, will smoke test approximately 77 gravity sewer lines and associated private junctions in public areas within the main town area of Mullumbimby.

    “Smoke testing is a standard testing procedure and an efficient and cost effective way to locate and identify leaks in the sewer system without the need for manned entry and with minimal disruption to residents”, Mr Clark said.

    Interflow will also conduct bucket testing on sewer manholes to test the integrity of seals and identify points where stormwater may be entering the sewer system. Bucket testing involves pouring water around the concrete surround of the sewer maintenance hole and identifying where water may be infiltrating through the walls of the manhole within a one minute period.

    Council’s sewer and stormwater mains in Mullumbimby were recently pressure cleaned and inspected for leaks and defects via CCTV inspection. The smoke and bucket testing will conclude the assessments on this infrastructure and will provide Council with a comprehensive understanding of the condition of its sewer and stormwater assets.

    Mr Clark said the results of a recent residential survey will also add valuable data to Council’s Reducing Stormwater in Sewer project for Mullumbimby.

    “The results of this work will further inform what action is taken,” Mr Clark said.

    To stay informed about the Reducing Stormwater in Sewer project in Mullumbimby, Council have a project page online at www.yoursaybyronshire.com.au/reducing-stormwater-in-the-sewer-mullumbimby

  • Council thanks Mullumbimby residents for survey response

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    09 Sep 2019
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    Byron Shire Council would like to thank Mullumbimby residents for their responses to the Reducing Stormwater in Sewer survey, issued to the community at the start of August.

    Council’s Manager Utilities, Mr Cameron Clark said there had been a good response from residents, indicating the high level of interest in this important issue in Mullumbimby.

    “The survey process has provided valuable insight into the latest condition of both private and public sewer and stormwater assets, especially since there’s been a major flood event since the last data was collected and the condition of pipes deteriorate with age.”

    The data will now be analysed by the Reducing Stormwater in Sewer project team and cross-referenced with existing Council data and latest reports from Interflow, a specialist contractor currently conducting testing and inspections of Council’s assets in Mullumbimby.

    Mr Clark said high priority areas will be established in the town and planning will commence for customised solutions, including the use of Water Sensitive Urban Design, an option being assessed by Australian Wetlands Consulting.

    Once the range of options has been developed the project will be presented to the Water and Sewer Committee for review before implementation.

    “Council continues to be open to possible solutions and will work with industry experts to identify the most effective, practical, cost effective and sustainable options for reducing stormwater in the sewer”, Mr Clark said.

    In response to residents’ reports of blocked drains, Council scheduled an immediate clean-up team to clear laneways and gutters in one of the most high priority areas identified through the survey.

    “Facilitating the flow of stormwater and reducing impact on private property is of paramount importance to Council. This is only the first step before longer term solutions are implemented,” Mr Clark said.

    The stormwater drain maintenance schedule for other areas of Mullumbimby will be reviewed during the development of options process.


  • Residential Survey - Stormwater and Wastewater Flooding in Mullumbimby

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    22 Jul 2019
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    Hey Mullum - how are your pipes?

    Does your property or street frontage experience flooding from stormwater or wastewater, especially in times of heavy rainfall? Our Water and Sewer team want to know.
    A five-minute survey is all it takes.
    Help Council reduce localised flooding and stormwater overflow into the sewage system in Mullumbimby.
    Click here to complete the Reducing Stormwater in Sewer Residential Survey.

    Survey closes Wednesday 14 August, 2019.
  • Searching for smart drainage solutions in Mullumbimby

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    22 Jul 2019
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    Recent data collected from flow monitoring of the sewerage system and inspections of Council’s water and sewer pipe connections will help find answers to why there is too much stormwater in Mullumbimby’s sewer.

    When too much stormwater enters the sewer, the treatment plant can become overwhelmed and cause overflows in the community.

    Pipes can deteriorate between inspections due to age, pressure from local development and heavy traffic, damage from tree roots or poor installation and maintenance. This leads to stormwater getting into the sewer system, commonly known as inflow. To manage inflow efficiently, sewer and stormwater pipes require regular inspection and maintenance.

    The amount of stormwater inflow to sewer has been monitored for over five months. This data will assist Council with identifying problem areas and calculating the cost of developing an efficient stormwater and sewerage network to accommodate population and tourism growth in the Mullumbimby area.

    Council’s Water and Sewer team are working with specialist environmental design and consulting agency, Australian Wetlands Consulting, to consider the benefits of Water Sensitive Urban Design in reducing inflow and improving drainage of stormwater in the town, to prevent it from entering the sewerage system.

    Water Sensitive Urban Design is a holistic approach to water management in urban areas, focusing on stormwater capture and recycling, cleaner waterways and greener, cooler towns and cities.

    To find out more about Water Sensitive Urban Design,click here

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  • Improving drainage for Mullum

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    22 Jul 2019
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    Drains and pipes are under examination in Mullumbimby to help reduce the risk of flooding and overflow in residential areas that occurs when too much stormwater enters the sewerage system. This is commonly known as inflow and infiltration.

    Byron Shire Council’s Water and Sewer team is actively gathering data on dry and wet weather flow rates, overflow events and the health of the pipes and sideline connections from Mullumbimby residences to Council mains.

    Six flow meters and two rain gauges were installed on Council mains in December 2018 and visual inspections on sewerage and stormwater connections began in late May 2019.

    Camera inspection and non-toxic smoke testing are also occurring in the Mullumbimby CBD area to help identify sources of inflow (stormwater entering the sewer from incorrectly installed pipes or drains).

    The smoke testing involves pumping coloured smoke into pipes to identify possible sources of inflow and infiltration. Cracked pipes are identifiable at points where the smoke becomes visible, such as from yards, roof gutters or pipes.

    These tests will be carried out by Interflow, a specialist subcontractor to Byron Shire Council.

    Jason Stanley, Project Manager Inflow and Infiltration for Byron Shire Council, said the overall goal of the project is to remove stormwater from the sewerage system at Mullumbimby to reduce costs for residents, Council, community and environment.

    “Stormwater overflow and localised flooding can damage personal property and homes, which can be costly to residents,” he said.

    When stormwater enters the sewer system it adds to the total flow reaching the sewage treatment plant. The excess flow then also increases costs to the community and Council through increased processing and energy costs of the treatment plant to process it. The treatment plant is also placed at risk of becoming overwhelmed.

    “Council will be working with individual property owners and residents later in the year to inspect connections from downpipes and rainwater tanks, low lying gully traps, drain openings, manholes and street gutters or swales,” he said.

    “It’s important we work together to identify improperly connected or outdated house and business surface drains connected to the sewer so that Council can provide infrastructure for the community of Mullumbimby that is not only adequate, but sets the foundation for a longer term sustainable solution.”

    Council’s Water and Sewer team is currently working with specialist environmental design and consulting agency, Australian Wetlands Consulting, to consider the benefits of Water Sensitive Urban Design to improve drainage in the town.

    “Residents’ desire to maintain the character of Mullumbimby is of paramount importance to us and our team is looking for ways to maintain the heritage look and feel of the town while providing better drainage for private residences and street frontages,” Mr Stanley said.

    Council has released a community survey for residents to assist Council in identifying high risk areas affected by inflow and infiltration. Residents will also be advised of inspection dates later this year by house-to-house letter drops and on-site door knocking immediately prior.

    You can keep up to date with information and register your interest in Reducing Stormwater in the Sewer project at yoursaybyronshire: https://www.yoursaybyronshire.com.au/

    You can complete the survey here.


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