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Walgett Weir Raising and Fish Conservation Works
About the project
To address the water supply issue in Walgett, the existing weir level needed to be raised. In addition, a fishway has been incorporated into the weir structure to allow fish to move freely upstream. This project was critical to the area, particularly in times of drought, experienced over the last five years. It will also ensure fish continuity and sustainability in the Barwon and upstream rivers for the associated communities.
Location
Walgett, New South Wales
Client & Duration
Walgett Shire Council
January 2020 - January 2021
Project Scope
- Raising the Walgett Weir by 1m
- Construction of a new 31 vertical slot fishway to facilitate upstream fish passage
- Construction of a high flow full width rock ramp
- Upstream flood mitigation works
- Removal of Namoi Weir #10
- Access road construction
Challenges
- Works were located at the confluence of the Barwon and Namoi rivers and part of the extensive Northern Rivers catchment. The river systems are subject to unpredictable and unseasonal weather including extreme heat and heavy rain, creating a high-risk environment through flooding
- The specified rock and quarry material could not be sourced locally, resulting in it being hauled a considerable distance
- Covid-19, border closures and local harvest season saw very limited local labour and subcontractors
- Compliance with the environmental impact mitigation
- Construction on a riverbank presented geotechnical challenges with poor ground conditions impacting sheet piling
Achievements
- Despite a 1 in 50-year record flood, unseasonal wet winter rains, border closures and challenging specifications the project has proceeded with minimal delays
- Strong local community and business engagement delivering social and financial benefits to the local residents
- Positive collaboration with the client to successfully deliver the project and secure future work
- 3D scanning technology used to assist with the fabrication and pre-engineering of fishway components, designed with minimal tolerances and tight specifications
- The project is close to completion even with the challenges of limited resources and regular trial and error
