The Reinvention of the Ayr Drinking Water Supply

THE REINVENTION OF THE AYR DRINKING WATER SUPPLY TO MEET WATER QUALITY AND RESILIENCY BENCHMARKS

Nick Wellwood Burdekin Shire Council

Cal Paige Burdekin Shire Council

Tayla Heuir Burdekin Shire Council

Coralie Mannea Burdekin Shire Council

The drinking water for Ayr, Brandon and Alva has been historically supplied via a network of connected Bore Fields since approximately 1966.

The treatment train associated with this drinking water has been historically low, while still meeting Australian Drinking Water Quality guidelines, due to the historical quality of the ground water in the Burdekin Delta. In recent times contamination of the drinking water was detected in the Principal Bore Field from external sources, which caused many bores to be switched off to meet drinking water health targets. This also resulted in an unbalanced network from the loss of the bore fields and placed additional network pressure on trunk mains not previously used for distribution from other bore fields in the catchment. The resiliency of the total network was called in to question, including water storage, trunk distribution capacity and future treatment trains. This resulted in a reanalysis and modelling subsequent of the total network and staged upgrade of trunk mains, Scada Controls, reservoir storage and pressure balance. Construction of these augmented works for the water supply network is now underway, including the design of future treatment works to future proof drinking water supply for several townships in the Burdekin. The details of the network analysis, design, trunk main route selection, bore field upgrade, control systems and reservoir storage analysis and structural design are outlined in this paper. This is the story of ‘The Reinvention of Ayr Drinking Water Supply’ and the many challenges faced on this journey.

Executive Summary

The potable drinking water of Ayr, Brandon and Alva has been historically supplied via a network of connected borefields since approximately 1966. The treatment train associated with this drinking water has been historically low while still meeting Australian Drinking Water Guidelines, due to the historical high quality of the groundwater in the Burdekin Delta. In recent times, since April 2018, PFAS was detected in the principal borefield coming from external sources which caused many of the bores within the Nelson’s Borefield to be switched off to meet drinking water health targets. This also resulted in an unbalanced network from the loss of this centralised borefield and placed additional network pressure on trunk mains not previously used from other borefields in the catchment. The resiliency of the total network was called into question including water storage, trunk distribution capacity and also the need for future treatment options. This resulted in a reanalysis and modelling and a subsequent total network upgrade of trunk mains, SCADA controls, reservoir storage and also pressure balancing mechanisms. Construction of this augmented works for the water supply is now well underway including the design of a future treatment plant to future proof the drinking water supplies for several townships within the Burdekin Shire local government area. This paper sets out the details of this analysis of the network, design elements, trunk main selection, borefield upgrade, control systems, the reservoir storage and also the future filtration staging to meet drinking water requirements for the Ayr catchment. This is the story of the ‘Reinvention of the Ayr Drinking Water Supply” and the challenges faced on this journey.

Introduction

The drinking water for Ayr, Brandon, Alva and also the remainder of the Burdekin Shire has been historically provided by a series of connected borefields that connects into the Burdekin Delta Aquifer. They effectively provide a ‘slow sand filtration’ of

water within the Aquifer which has been historically high quality and enabled very little treatment to meet Australian Drinking Water Guidelines. Historically since 1966, water was simply extracted by pump from the aquifer via these borefields with very little treatment. Following the revisions of the Australian Drinking Water Guidelines the treatment train expanded to allow for disinfection by sodium hydrochlorite and also oxidation to remove Co2 from the water enabling a softer and also longer asset life of distribution networks.

In April 2018, tests were undertaken by Qld Health which discovered PFAS contamination which are polyfluoroalkyl substances in the principal borefield at Nelson’s Borefield. This resulted in further analysis of the contamination which determined the relevant PFAS signatures of PFOS and PFOX SX. The speciation of this PFAS required an extensive amount of work to enable both the Council and Regulators to determine the source of contamination of the groundwater. Contamination of the aquifer was extensive and the point source treatment of the PFAS contamination was deemed to be too expensive both in terms of capital costs and also providing enduring safety to enable water to be effectively treated below current and potentially future Australian Drinking Water standards relating to PFAS.

The decision was taken by Council to decommission the bores which had PFOS levels exceeding Drinking Water Standards whilst using the remaining bores with lower contamination levels under the drinking water standards and also combining with other borefields within the Ayr Catchment. This resulted in an unbalanced network from the loss of the borefields and placed additional network pressure on trunk mains which were not previously used for distribution from other borefields in the catchment. The total resiliency of the water supply network was found to be deficient, and it was decided that a holistic solution was required and indeed the “Reinvention of Ayr Drinking Water Supply” needed to be undertaken.

This paper examines both the background to the contamination of the drinking water and also looks at the various proposed water solutions which was undertaken to address the resilience of supply of drinking water for both Ayr, Brandon and Alva. This paper examines the network analysis required to redesign the distribution of water supply within the catchment as well as potential water storage requirements to achieve greater resilience, due to the lack of consistent borefield operation within the contaminated aquifer and also the need to provide more resiliency in relation to North Queensland weather and disaster events. The paper looks at the various treatment trains both in terms of the initial phase of iron and manganese removal and also the future proofing of the water treatment to potentially allow for future raw river extraction and treatment. The current construction works including a new trunk main augmentation, under boring, borefields and also the construction of a 10ML storage and pumping is examined in detail within the paper. The staging of filtration to deal with initially the iron and manganese and secondly the raw water is also examined as well as future changes to the Drinking Water Quality Management Plan which will be required as part of this “Reinvention of the Ayr Drinking Water Supply”. Finally, the paper looks at the future challenges in relation to the supply of drinking water within the Ayr catchment and also the need for continual monitoring and adaption of the proposed drinking water solution for the Ayr, Brandon and Alva communities.

Conclusion

In conclusion, the discovery of PFAS within the principal borefield at Nelson’s lagoon in the township of Ayr has been highly problematic in relation to the distribution of clean drinking water to the townships potable water scheme. The entire Council Engineering team including external agencies have worked rigorously on solutions that have been set out in this paper to continue to provide safe and clean drinking water with PFAS levels below the Australian Drinking Water Guidelines. The resulting disconnection of the Nelson’s lagoon borefield has required extensive re-analysis

Current bore locations in Ayr

Trunk duplication pipeline alignment

Proposed Trunk Main Alignment

and re-engineering of the entire drinking water network within Ayr to ensure that all water meets the Australian Drinking Water Health-Based Guidelines. The resulting unbalanced network has been overcome by the design and construction of additional trunk pressure mains to take pressure off mains not designed for this distribution. The provision of greater water storage to allow water to be taken from more distant borefields and stored centrally within the Ayr township to provide water for the Ayr, Brandon and Alva potable water network. The total resilience of this scheme has been increased by the provision of this water storage and also the increase of trunk water distribution capacity. The design of a treatment plant to remove iron and manganese from the water within the South Ayr Borefield, which despite this mineral discolouration is free of PFAS and provides a relatively cost-effective solution to supplement the loss of water from the disconnected Nelson’s Borefield catchment. The design of this filtration plant is underway and is expected to then translate a business case for the construction of the first phase of the treatment train required to remove the iron and manganese from South Ayr bore field which will provide greater provision of clean drinking water to the entire network. All of these elements including the network analysis, the trunk main design and route selection, construction works of borefield upgrades, distribution trunk mains and reservoir storage have resulted in a complete “Reinvention of the Ayr Drinking Water Supply”. There have been many challenges along this journey, however the adaptable management from both Council and State Government Agencies response to this emergent issue has established water network solutions that were both practical and sustainable. This has achieved the continued supply of clean drinking water for the townships of Ayr, Brandon and Alva.

INFORMS. CONNECTS. REPRESENTS. LEADS.

UP TO 6 CPD HOURS

TEMPORARY TRAFFIC MANAGEMENT PRACTICE FOR MANAGERS, SUPERVISORS AND PROJECT MANAGERS

Overview Temporary Traffi c Management (TTM) represents one of the highest WHS risks to Road Infrastructure Managers (RIM) due to the volume of activities that occur on and near roads and the serious outcomes that may arise in the event of a traffi c incident. Asset owners must have a clear understanding of the associated risks and develop the policies, procedures, guidance, and systems that ensure that best practice TTM is implemented as practicable. Content This one-day workshop will provide a practical overview of the new standards, the key changes in TTM practice, and other key elements that must be applied to achieve compliance. Key learnings will impart a better understanding of best practice TTM and explore the potential for substantial cost savings by reducing the level of TTM and the subsequent costs for a wide range of low impact and short-term activities without a reduction in safety. Learning strategies • Lectures • Case studies • Group discussion • In-class activities and exercises

Who should attend? This workshop is primarily aimed at staff involved in the areas of planning and managing road construction and maintenance activities, including, but not limited to: • Road Asset Managers • Engineers • Technical professionals • Project Managers • Supervisors • Inspectors Outline • An overview of all reference documentation • Key changes in TTM practice • RIM role and obligations • Policy and process documentation • Self-delivered services • 3rd party works • RIM role in procuring and managing projects with TTM • Procurement of TTM and risks commonly seen. • Roles responsibilities of RIM / PCBU / TTM contractor • Current industry issues and risks • Overview of TTM technical requirements • Introduction to a TMP, its requirements and contents, and what to expect • Introduction to the TGS design and best guidance for oversight • Training requirements • Best practice processes for surveillance and inspection of TTM on site.