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Artist impression of the upgrades for the Lake Macdonald Dam Improvement Program - right side view
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Lake Macdonald Dam Improvement Project

Seqwater is upgrading Noosa’s Lake Macdonald (Six Mile Creek) Dam as part of its Dam Improvement Program. Early works are now underway, with construction expected to commence mid-2024.

Home What We're Doing Lake Macdonald Dam Improvement Project

About the project

Dams are long-life assets which require continual assessment, monitoring and maintenance. South East Queensland dams were built to high safety standards, but most were built some decades ago. Methodologies and data used to estimate extreme rainfall events continue to improve and industry engineering standards and understanding of risks can progress over time. 

Across Queensland and Australia, there are multiple dam upgrades occurring to meet modern engineering standards. 

Seqwater’s Dam Improvement Program is ensuring its dams comply with the latest safety standards and continue to function safely during extreme weather events in line with regulatory requirements.  

The Lake Macdonald Dam Improvement Project will involve building a new spillway and reconstructing the existing earth embankments. 

The project will reduce risks associated with extreme weather events, achieve regulatory compliance, and ensure the continued reliability of this water source for the Sunshine Coast region for years to come.  

Lake Macdonald Dam Improvement Program timeline - early works

    Project update

    Project update

    Throughout 2021 and 2022, Seqwater worked with a Technical Review Panel to evaluate and short-list options for the Lake Macdonald Dam Improvement Project.

    In 2023, Seqwater worked through the preferred design option, completed the environmental and economic studies, and advanced through important project approvals.

    The confirmed design option includes a new split-level concrete spillway (set at the original lake level), with an upper labyrinth spillway (zigzag in shape) to accommodate higher floods (see design section for detail). 

    The optimal construction approach is being worked through, including finalising the engineering. While this is an important project to ensure the ongoing safety of the structure during extreme weather events, Seqwater is committed to reducing the impacts of construction wherever possible. 

    Areas of impact assessed included, but were not limited to, water security and the lake level, traffic, noise, dust, water quality, recreation, cultural heritage, environment and ecology. Extensive project planning has led to a modification of the construction plan, and there will now be: 

    • More water in Lake Macdonald during construction through the use of a temporary cofferdam
    • The Noosa Water Treatment Plant will continue to operate for ongoing water security
    • Reduced impact/risk to aquatic life, plants and animals in and around the lake due to higher lake levels
    • Environmental flows will be maintained to ensure water supply to support the habitat downstream
    • Some recreation areas and activities at Lake Macdonald Park will remain open during construction: 
      • The boat ramp at Lake Macdonald Park, next to the Noosa Botanic Gardens
      • Fishing, stand up paddle boarding and canoeing 
    • Benefits to local community and visitors by keeping the lake open
    • The project will employ local contractors and procure local businesses as much as possible.

    Design 

    Lake Macdonald Dam Improvement Project split level labyrinth spillway layout design

    This image shows the new split level spillway layout, including the upper labyrinth spillway (zigzag portion of the dam wall), and the new embankment. 

    The design for the new dam wall at Lake Macdonald is a split-level concrete spillway. The primary 'lower ogee' spillway is set at the original lake level, and an upper labyrinth spillway for higher floods.  

    A labyrinth spillway is an overflow weir, zigzag in shape, to enable higher flows due to a longer total effective length over the spillway, caused by large rain events. The labyrinth spillway provides an efficient means of increasing spillway capacity without raising the dam’s crest.  

    The earth embankments will be reconstructed to their original level on either side of the spillway. 

    Scour protection will be an addition, with rocks placed downstream of the spillway to prevent erosion.  

    An outlet tower will be constructed to the left side of the spillway which will have mechanical pipework and electrical components to facilitate both emergency release of water, to lower the dam reservoir, and environmental flows to the downstream Six Mile Creek.  

    At completion of the project, the new dam will have the same storage volume and full supply level as the existing dam (storage to 8,000ML). The improved design will be able to withstand a 1 in 500,000 year flood, meeting modern dam safety guidelines. 

    Project scope 

    The Lake Macdonald Dam Improvement Project will include:  

    • Minor lowering of the Lake Macdonald water storage to accommodate construction. Seqwater has worked to minimise this impact, with a temporary water level that will be reduced by approximately 2 metres, from the full supply level (technically speaking this will be at RL 93m or 42%). This water level will provide water security reliability for the Noosa community and maintain access to the lake and local ambience.  
    • Relocation of fish by expert fish biologists, via a purpose-built fish transport vehicle, to Cooloolabin Dam. 
    • Construction of a cofferdam to protect the site and manage flows in Six Mile Creek during construction. 
    • Demolition of the existing spillway and dam wall. 
    • Removal of unsuitable foundation material under the new spillway, excavating down to a rock foundation, then backfilling with mass concrete. 
    • Construction of a split-level concrete spillway. The primary spillway will be set at the original lake level, and an upper labyrinth spillway will be constructed for large floods.  
    • Removal and reconstruction of the earth embankments on either side of the primary spillway.  
    • Ground improvement works below the new embankments. 
    • Provision of a new outlet works structure to enable environmental releases downstream of the dam into Six Mile Creek. 

    Additional works include fish protection measures (including proposed construction of a fishway at Gympie Weir), land management activities and rehabilitation.   

    Upstream cofferdam  

    A cofferdam structure will be built to undertake the construction work safely. A cofferdam is an enclosure built within a body of water to allow the enclosed area to be pumped out or drained. The pumping creates a dry working environment so that the dam wall construction work can be carried out safely.  

    The cofferdam for the Lake Macdonald Dam Improvement Project will be:  

    • 300 metres long 
    • 10 metres wide   
    • Approximately the same height as the current dam wall. 

    Construction will commence in the first half of 2024 and take around 12 months to build. This is a temporary measure for dam safety during construction and once the new dam wall is complete, the cofferdam will be removed, and the dam will naturally refill to its original full supply level. 

    Minor lake lowering

    Seqwater has worked to minimise environmental impacts from this project, with a revised construction methodology that will temporarily reduce the water level by approximately 2 metres, from the full supply level. 

    Technically speaking, Lake Macdonald will sit at about 42 per cent of its full supply level (or 93 metres). 

    This reduced water level will allow the construction work to safely take place. The lake will remain at this level throughout construction unless dry conditions create a naturally lower level.  

    The Noosa Water Treatment Plant will continue to be operated as per the annual operating strategy and the monthly operational supply schedule (currently 20ML/d on average). 

    Drop-in information sessions

    The below drop-in community information sessions are being held to provide the opportunity to seek further information on the project. Drop by anytime during the sessions to speak with the team:

    • Tuesday 13 February, 2:30pm-5pm - Cooroy Memorial Hall, Maple St Cooroy
    • Monday 19 February, 9:30am-12noon - Cooroy Memorial Hall, Maple St Cooroy
    • Saturday 2 March, 9:30am-12noon - Pomona Memorial Hall, Reserve St Pomona
    • Tuesday 19 March, 2:30pm-5pm - Cooroy Memorial Hall, Maple St Cooroy.

    For more information

    If you have any questions about the project, please see the project FAQs below, or get in contact with the project team.

    Phone us: 07 3432 7000 (Monday to Friday, 9am to 5pm)

    Email the team: [email protected]

    Stay informed as this project progresses, by signing up to project updates below.

    • Project updates
    • FAQs
    • Resources
    • Lake Macdonald

      John Holland Group Queensland awarded Lake Macdonald Dam Improvement Project construction contract

      Seqwater has awarded John Holland Group Queensland the construction contract for the upgrade of Noosa’s Lake Macdonald (Six Mile Creek) Dam.

      Part of Seqwater’s Dam Improvement Program, the upgrade will enhance water security and enable the dam to withstand extreme weather events.

      The project involves building a new split-level concrete spillway and upper labyrinth and reconstructing the existing earth embankments. 

      Major site construction activities will commence later in the year.

      Drone shot of a crystal blue lake with a wide concrete spillway

      Community info sessions begin for Lake Macdonald Dam Improvement Project

      Seqwater has released the final design concept for the upgrade of Noosa’s Lake Macdonald (Six Mile Creek) Dam, with early works commencing ahead of major construction in mid-2024.   

      Part of Seqwater’s Dam Improvement Program, the upgrade will enhance water security and enable the dam to withstand extreme weather events. 
      Seqwater is committed to keeping the community informed throughout the project and will hold community information drop-in sessions in February and March, where the project team will be available to talk through the design and construction approach and answer any questions.

      Community Information Drop-In Sessions:
      Cooroy Memorial Hall:
      •    Tuesday 13 February: 2:30pm – 5:00pm, Cooroy Memorial Hall 
      •    Monday 19 February: 9:30am – 12:00noon, Cooroy Memorial Hall 
      •    Tuesday 19 March: 2:30pm – 5:00pm, Cooroy Memorial Hall 
      Pomona Memorial Hall: 
      •    Saturday 2 March: 9:30am – 12noon, Pomona Memorial Hall 

       

      Lake Macdonald

      Early works begin on Noosa’s Lake Macdonald Dam Improvement Project

      • Early works on the Lake Macdonald Dam Improvement Project have commenced, ahead of major construction mid-2024
      • Creating 150 jobs for Sunshine Coast locals
      • New split-level concrete spillway to increase the dam’s capacity to withstand extreme weather events, and maintain water security

      Seqwater has released the final design concept for the upgrade of Noosa’s Lake Macdonald (Six Mile Creek) Dam, with early works commencing ahead of major construction in mid-2024. 

      Part of Seqwater’s Dam Improvement Program, this upgrade will enhance water security and enable the dam to withstand a 1 in 500,000-year flood event.

      The dam improvement project involves building a new split-level concrete spillway and upper labyrinth and reconstructing the existing earth embankments. 

      Following a comprehensive technical review undertaken in 2021 and 2022, the new optimised design will increase the dam’s capacity to withstand extreme weather events while also ensuring the dam remains operational during construction for water security and some recreation activities.

      Seqwater has worked hard to keep the lake water level as high as possible during construction. The lake will be temporarily lowered for construction work to occur safely, and a temporary cofferdam will be installed to support water security during construction. The Noosa Water Treatment Plant will continue to operate during construction.

      This will be the first major upgrade of Lake Macdonald Dam since its original construction in 1965. Importantly, more than 150 local jobs are expected to be created over the life of the project.  

      Survey works are currently underway on-site, with site establishment and lake lowering occurring over the coming months. Major work to construct the temporary cofferdam is expected to commence mid-2024, following contractor appointment.

      Due to the significant nature of the project, some recreational use of the lake and surrounding areas will be disrupted during construction. However, recreation activities at Lake Macdonald, Lake Macdonald Park and the Noosa Botanic Gardens will remain open.

      Seqwater will keep the community informed throughout the project and will hold information sessions early-2024 where the project team will be available to talk through the design and construction approach and answer any questions. 

      Quotes attributable to Minister for Water, Glenn Butcher:

      “I’m pleased to see progress on this critical project. This important upgrade will ensure the longevity of Lake Macdonald Dam so it can continue to provide water security and dam safety for years to come. 

      “Dams in Queensland are built to very high, internationally accepted safety standards, but methods used to estimate extreme weather and flood risks have changed significantly since some were built.

      “This is one of several important dam safety projects being undertaken by Seqwater. Since 2015, Kinchant Dam, Eungella Dam, Wappa Dam, Boondooma Dam, Leslie Harrison Dam, Fairbairn Dam, and Sideling Creek Dam (Lake Kurwongbah) have been completed across Queensland.

      “With construction starting soon, the upgrade is also set to boost local employment opportunities in the region, with around 150 jobs expected to be created over the life of the project.” 

      Quotes attributable to Seqwater CEO, Neil Brennan:

      “While Lake Macdonald Dam continues to operate safely, the upgrade will ensure the dam meets updated engineering and safety standards, taking into account extremely rare weather scenarios and climate change.

      “The revised design will allow water to be retained in Lake Macdonald during construction, some recreation activities to remain open, reduced impact on aquatic life, plants and animals in and around the lake, and will ensure the Noosa Water Treatment Plant continues to operate for local water supply. 

      “Projects of this scale are complex and require significant planning time and we thank the community for their understanding while we undertook this important work.” 

      Further Information:

      Through its Dam Improvement Program, Seqwater is investing in South East Queensland’s dams to ensure they provide water security for years to come.

      Dams are long-life assets which require continual assessment, monitoring and maintenance. 

      Seqwater’s dam infrastructure upgrades are progressively being delivered and are due for completion by 2035.

      Seqwater undertakes regular monitoring and engineering assessment to make sure the region’s dams continue to operate safely.

      An aerial image showing a wide spillway with additional concrete zig zag steps to one side

      Lake Macdonald Dam Improvement Project Update

      Throughout 2021 and 2022, Seqwater worked with a Technical Review Panel to evaluate and short-list options for the Lake Macdonald Dam Improvement Project.  

      In 2023, Seqwater worked to confirm the preferred design option and obtain the required state and federal approvals to proceed with the project. 

      Seqwater has completed comprehensive engineering, environmental and economic studies; as well as taken on the feedback from the previously established community reference group in 2019. All of this information has gone into informing the best design approach that focuses on reducing potential project impacts to the community and environment.   

      Seqwater finalised the design option in late 2023 which involves a new split-level concrete spillway, with an upper labyrinth spillway for extreme floods (see design section for detail).  

      While this is an important project to ensure the ongoing safety of the structure during extreme weather events, Seqwater is committed to avoiding or reducing the impacts of construction wherever possible.  

      Areas of impact assessed included, but were not limited to, water security and the lake level, traffic, noise, dust, water quality, recreation, cultural heritage, and ecology. Seqwater has also taken onboard community feedback obtained through the previous Community Reference Group sessions, where possible. 

      Project planning has included the modification of the construction methodology, and there will now be:  

      • The use of a coffer dam, to retain water throughout the project 
      • More water in Lake Macdonald during construction 
      • The Water Treatment Plant will continue to operate, utilising water from the lake 
      • Environmental flows will be maintained as per the condition of the water license  
      • Reduced impact/risk to aquatic life, plants and animals in and around the lake  
      • Recreation areas at Lake Macdonald Park will remain open during construction:  
      • The boat ramp at Lake Macdonald Park, next to the Noosa Botanic Gardens 
      • Fishing, stand up paddle boarding, canoeing  
      • Benefits to local community and visitors by keeping the lake open 
      • The project will employ local contractors and procure local businesses where possible. 
    • No FAQs match your query

      What is the Dam Improvement Program (DIP)? 

      South East Queensland dams were built to high safety standards, but most were built some decades ago. Methodologies and data used to estimate extreme rainfall events continue to improve and industry engineering standards and understanding of risks can progress over time. 

      Across Queensland and Australia, there are multiple dam upgrades occurring to meet modern engineering standards. 

      Seqwater’s Dam Improvement Program is ensuring the region’s dams comply with the latest safety standards and continue to function safely during extreme weather events in line with regulatory requirements.  

      Since 2008, Seqwater has delivered 13 upgrades, including Leslie Harrison Dam at Capalaba, Sideling Creek Dam north of Brisbane and Ewen Maddock Dam on the Sunshine Coast.  

      Planning work is underway for the next tranche of upgrades at Somerset, Wivenhoe, North Pine and Lake Macdonald Dams.   

      Seqwater undertakes regular monitoring and engineering assessment to make sure the region’s dams continue to operate safely. 

      Why does Lake Macdonald Dam need to be upgraded?

      Lake Macdonald – also known as Six Mile Creek Dam – was originally constructed in 1965. 

      There have been significant advances in dam design since the dam was built, as well as new ways of estimating extreme rainfall and flood events, and a greater understanding of the size and severity of earthquakes.

      This will be the first major upgrade of the dam since the wall was raised in 1980. The Lake Macdonald Dam Improvement Project will aim to:

      •    increase the spillway capacity to safely pass floods 
      •    protect the dam wall in extreme flood events
      •    efficiently control water flowing out of the dam 
      •    reduce risks to the dam structure during earthquakes
      •    meet modern design and engineering standards
      •    comply with dam safety guidelines.

      What will Lake Macdonald Dam look like, following the upgrade? 

      The new dam will occupy the same footprint as the current structure, but the spillway will be a split-level concrete spillway. The primary ‘ogee’ spillway is set at the original lake level, and an upper labyrinth spillway will be constructed for large floods. No spillway gates are included in the new structure; and reconstruction of the earth embankments to their original level on either side of the primary spillway. 

      The primary spillway is a flat concrete structure, similar to the current dam wall.   

      The labyrinth spillway has a zigzag shape when viewed from above and is made from concrete. In the event of a very large inflow, the water will flow over the upper labyrinth spillway and into Six Mile Creek downstream.  

      The current earth fill embankment on the Lake Macdonald Drive side of the spillway does not meet today’s design and safety standards – that is, it is too steep and at risk of erosion. The new embankment at this location will be the same size and height of the existing embankment and finished grass and rocks.  

      The right earth embankment on the other side of the dam's spillway, closest to the water treatment plant, will also be re constructed and finished with grass (looking much the same as it does now.   

      Rocks will sit down stream of the new spillway, called scour protection, and will assist in preventing erosion.  

      An outlet tower will be constructed to the left side of the spillway which will have mechanical pipework and electrical components to facilitate both emergency release of water, to lower the dam reservoir, and environmental flows to the downstream Six Mile Creek.  

      What will the cofferdam look like? 

      A temporary coffer dam structure, engineered to manage inflows after each rain event, will be built in 2024 to undertake the construction work safely. This structure will hold back the water in Lake Macdonald during construction of the new dam wall. This is a temporary measure for dam safety and once the new dam wall is complete, the coffer dam will be removed, and Lake Macdonald Dam will be able to naturally refill to its original full supply level (8,000ML).  

      How long will the dam upgrade take? 

      Work will commence on the project in 2024, with a range of pre-construction works including site mobilisation and establishment, minor lake lowering, coffer dam establishment, and fish salvaging and relocation. Construction of the spillway is scheduled to commence later in 2024 and is expected to take approximately four years to complete. We expect the project be complete in 2028 - subject to weather and construction conditions.  

      How will impacts to the natural flora and fauna be mitigated? 

      As part of the planning and delivery, Seqwater has undertaken extensive environmental investigations by way of both desktop searches and field surveys focusing on protected plants, important habitats for plants and animals, waterway environments, and significant local species. 

      This has helped to inform reduced water levels, locations to avoid around Lake Macdonald, where possible, as well as inform any mitigations needed to be in place during construction. 

      Seqwater is aware that the minor lake lowering and construction works will have some impacts on the flora and fauna, both in and around the lake, and is committed to minimising and mitigating these impacts. A range of surveys and studies have been completed to identify the species of aquatic fauna, including those of conservation significance in the lake. An environmental management plan will be in place during construction, which outlines the measures required to minimise the impact of the natural environment.  

      Click here for the link to the Coordinator General’s evaluation reports on this project.

      Will there be fish relocation in the lead up to construction?  

      Investigations are underway into the measures needed to manage aquatic fauna at the 42% or 93m reduced water level. Seqwater will develop a comprehensive recovery and relocation plan, in consultation with key stakeholders, to manage any aquatic fauna impacted during the lowering and throughout construction. 

      It is expected there will be a period when the habitat available for aquatic species, including those of conservation significance such as the Mary River cod, Australian lungfish, Mary River turtle, white-throated snapping turtle, and platypus, is limited. To minimise the impacts to these important species, Seqwater is proposing an initial aquatic fauna relocation program.  

      We will aim to relocate species of conservation significance before construction begins. Some fish are sensitive to handling or changes in water temperature and may suffer injury or mortality if relocated. Therefore, appropriate measures will need to be identified and incorporated into the management approach. 

      All relocation will be delivered by expert fish biologists, via a purpose-built fish transport vehicle to Cooloolabin Dam.

      Can I still fish in the lake throughout the project? 

      At this stage, Lake Macdonald will remain open to all on-water recreation activities during the construction period including motorless boating, canoeing, and fishing. These activities will be permitted outside of the construction zone, which the coffer dam will isolate. We expect there will be areas around the lake for shoreline fishing. Once the upgrade is complete, Lake Macdonald will continue to be used for water supply as part of the South East Queensland Water Grid, and the lake will remain open to the public for shared recreation.  

      What will traffic impacts be? 

      We expect project vehicles, including heavy vehicle traffic to use Elm Street, Lake Macdonald Drive, Sivyers Road, and Gumboil Road.  The project will implement a traffic management plan including traffic control as required to manage the safe flow of traffic, on the affected roads. 

      Will any roads close during construction?  

      During construction there may be partial road closures and temporary changes to traffic conditions at times for the safety of road users. We will provide advance notification of any road closures, including details of any detours. 

      What noise impacts can be expected during construction?   

      Neighbours should expect increased noise at various times during construction. The project team will be in contact with those residents who are directly affected throughout the project to advise of noise impacts in advance. Every effort will be made to minimise impacts on the local community and environment while this work is undertaken. We thank the community in advance for your patience and understanding while these necessary works are carried out. 

      Construction activities will include, but are not limited to, demolition works, heavy vehicle moment, concrete batching and pouring, rock breaking, drilling, piling, excavation and stockpiling of raw materials. 

      There will be times of weekend and nightworks for time critical construction activities, which we will be sure to notify the neighbours of beforehand.

      What impacts will there be to recreation areas?  

      Seqwater has been able to work through a new construction approach and Lake Macdonald is expected to remain open to on-water recreation and parks and facilities recreation throughout the project. This means that both Lake Macdonald and Lake Macdonald Park (off Lake Macdonald Drive), and the Noosa Botanic Gardens will remain open.

      There will be closures to the scouts camp ground, the Mary River Cod Park and the Mary River Cod Park boat ramp, the fishing platform on Lake Macdonald Drive, and walking, riding and horse trails.

      This image shows the Lake Macdonald boat ramp, foreshore, and Lake Macdonald Park which is expected to remain open to the public during construction of the dam.

      An aerial shot of a boat ramp and foreshore area leading into a blue lake

      Will the project construction impact local water security for the region? 

      To maintain local water security during the construction of the project, a minimum Full Supply Volume of 42% will be retained for Lake Macdonald Dam (which equates to a level of 93m AHD), and the Noosa Water Treatment Plant will continue to operate. 

      To the community, this will look approximately two (2) metres lower than the dam's full supply level. 

      This is the level the lake will sit at throughout construction unless dry conditions create a naturally lower level.

      Does the need for a dam improvement project mean the dam is currently unsafe?  

      All Seqwater dams within the Dam Improvement Program continue to operate safely. Dam improvements are undertaken to meet modern guidelines for these life-long assets – many of which were built some years ago. 

      Seqwater undertakes regular monitoring and engineering assessments to ensure all our dams continue to operate safely. 

      Dams in Queensland were built to high, internationally accepted safety standards. However, the methodologies and data used to estimate extreme weather events and flooding impacts have significantly improved, and engineering standards and risks have progressed. 

      All these factors are considered as part of Seqwater’s Dam Improvement Program so our dams continue to operate as they should, now and into the future.

      Will water still be able to flow/runoff downstream into Six Mile Creek?

      In line with the water license for Six Mile Creek, Seqwater manages continuous environmental releases from Lake Macdonald to maintain a healthy water supply to help protect the habitat downstream.

      Environmental releases, which will continue during the Lake Macdonald Dam Improvement Project, occur daily and are adjusted based on a range of factors including rainfall, inflows, losses and releases to ensure we meet our release obligation.

      Seqwater has ongoing long-term source water protection partnership programs with both the Mary River Catchment Coordinating Committee (MRCCC) and the Noosa District Landcare Group (NDLG). As part of these partnerships, Seqwater works with MRCCC and NDLG to improve water quality and broader catchment health.

      Seqwater will continue taking steps to improve overall catchment resilience in the region for water supply and quality benefit, including during periods of low rainfall.  

      Will platypus at Lake Macdonald be impacted?

      Seqwater is committed to the responsible management of the environment, including caring for flora and fauna and complying with relevant legislation and environmental requirements. A Species Management Plan has been developed which addresses platypus preservation, including specific mitigation and management actions for each phase of the project. Measures include riparian vegetation management and considering the timing and volume of water releases to maintain flows in line with the natural creek flow regime for platypuses living downstream.

      Will a fish ladder be included in the upgrade?

      There is no existing fish passage (a fish ladder is a specific type of fish passage) at Lake Macdonald Dam, and no proposed fish passage included in the Lake Macdonald Dam Improvement Project. The reasons for this are:   

      • There are currently no fish pest species in Lake Macdonald, and a fish passage could allow for pest species to enter Lake Macdonald reservoir.  

      • A more suitable location for a fish passage has been identified at the Gympie Weir. A fish passage in this location will allow fish to pass up and down the main Mary River, allowing passage between the upper tributaries and reaches. 

      • The Coordinator-General, as part of the Project Approval Conditions, have stated that Seqwater upgrade the Gympie Weir to include a fish passage.  

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