Gannawarra Shire Council: Quambatook Weir Refurbishment and Mechanisation

Mar 31, 2014 by vic@ipwea.org.au    Comments Off    Posted under: Innovation

This project refurbished the Quambatook Weir flood control mechanism from a deteriorating concrete structure with manually operated gauge boards to become a ‘state of the art’ air operated water control gates system, eliminating the manual handling issues with its operation.  The project was a collaborative approach between Gannawarra Shire Council, North Central Catchment Management Authority (NCCMA) and the local community and was instigated as a consequence of the damage caused to the weir by the January 2011 flood event. The project was managed by the Gannawarra Shire Council and overseen by the NCCMA.  Under the direction of the successful contractor, the existing concrete wall was strengthened and a new aluminium air operated lay flat water control gates system was installed.

Project Description

a.        Project Objectives

The project objective was to refurbish the Quambatook weir and provide an operable flood gate that allowed the passage of unimpeded flood flow in the Avoca River and have the ability to retain the maximum weir pool volume for community amenity and recreational use.  The existing weir was old and structurally unsound and was damaged in the 2011 flood event.  Flood control was achieved by manually placed horizontal wooden gauge boards which were difficult to operate during floods and involved considerable manual physical risk in doing so.   Consideration for lifting the boards was based on a gauge water level of 3-4m (2400 – 3100 ML/day).  The boards were removed when water level reached 5-6m at the Charlton gauge (5500 – 8400 ML/day).  The objective was to bring the weir into a strengthened, safe operating condition with a modern pneumatic flood gate mechanism.  Funding was secured by the NCCMA from the “Natural Disaster Relief and Recovery Arrangements” for the repair and mechanisation of the weir which provided an appropriate full water level and open weir height that was acceptable to the Council, NCCMA and  the community.  The project was put out to tender by the Gannawarra Shire Council and APCR McDonald.  Constructions P/L was selected as the successful contractor with a concept proposal from subcontractor (AWMA) for the gate mechanism design.  Key objectives of the project were to minimise on-going maintenance, minimise or eliminate OH&S issues, provide a facility that met expectations of community amenity, recreational use and environmental features, and it must be cost effective.    The main objectives of the project were to address the issues of  ongoing management of the weir pool levels, while ensuring that there would be no impact on flood levels or extents, and to minimise on-going maintenance and operation of the weir structure.

b.      Project Outcomes

Completion of the works ensured that the weir structure was brought up to a condition where the Gannawarra Shire was satisfied to enter into a Deed of Transfer with the NCCMA to take over ownership of this asset.  The weir structure was refurbished and a mechanised flood gate operating system installed.  The water level in the weir and the volume of water flowing through it can now be controlled by means of an air operated water control gate regulated via a control panel located on the bank of the weir.  An appropriate full water level and open weir height were established through community involvement and a detailed report prepared by the NCCMA. The full (gate closed) level was revised to give the maximum amount of water retained in the weir for the purpose of community amenity, improved environmental outcomes and recreational use. The ability for the weir structure to pass flood flows in the Avoca River (gate open) was reviewed and a new open gate level set.

c.       Innovative features of the project

Using an established Design and Construction Tender process the Gannawarra Shire provided potential contractors with the opportunity to be innovative in the solutions they proposed for this project.   APCR McDonald Constructions P/L was awarded the contract, with a concept proposal from a subcontractor (AWMA) for the gate mechanism design.  The subcontractor – AWMA of Cohuna – is a local company involved in the water control industry (across Australia) and has a renowned reputation for innovative solutions to water management challenges. Their proposal utilised a pneumatic air operated water control gate system to raise and lower the gate in a tilting lay flat design. The system is controlled from a control panel on the bank and eliminates the manual handing of gauge boards and the need to gain access onto the wall structure.

d.       Innovative features of the project

Using an established Design and Construction Tender process the Gannawarra Shire provided potential contractors with the opportunity to be innovative in the solutions they proposed for this project.  APCR McDonald Constructions P/L was awarded the contract, with a concept proposal from a subcontractor (AWMA) for the gate mechanism design.  The subcontractor – AWMA of Cohuna – is a local company involved in the water control industry (across Australia) and has a renowned reputation for innovative solutions to water management challenges. Their proposal utilised a pneumatic air operated water control gate system to raise and lower the gate in a tilting lay flat design. The system is controlled from a control panel on the bank and eliminates the manual handing of gauge boards and the need to gain access onto the wall structure.

e.      Benefit to the community of the project or service

Prior to the commencement of the construction works, an extensive community consultation process was conducted.  The height of the water level in the weir was an important issue for the community, whose preferred option was to hold the level at a maximum height in normal flow conditions. There was a strong recognition by the community that flood flows needed to pass through the structure with minimum afflux that could potentially affect flood levels in the town of Quambatook.   The weir is downstream of Quambatook which is a small rural township in the Victorian mallee.    The Avoca River is a feature of the township and as well as the essential aesthetic value of the weir, the weir is important for both wildlife and people, especially with the majority of dams and alternate water sources having been eliminated over recent years with the introduction of the Wimmera Mallee pipeline.   Socially, the weir is a key gathering point for exercise, social events and sport including fishing and canoeing. The ability to manage the flow of all available water through the weir is integral to getting the maximum benefit for the community.

f.        Program and project management, highlighting how any barriers were overcome to achieve success

The refurbishment of the Quambatook weir was an initiative of the NCCMA, who sourced funding, initial concept designs and conducted the community engagement process.  Gannawarra Shire Council took over the responsibility for project management and settled on the Design and Construction Contract format to encourage innovative solutions to address the issue of flood mitigation and security for the Quambatook Township.

Barriers to the project were:-

g.           Costs/benefits associated with the Project

The total cost of the project was $218,000 made up of $150,000 sourced through the Natural Disaster Relief and Recovery Fund, with the remainder of funds required contributed by the North Central Catchment Management Authority.  The original estimated cost of the replacement was $265,000, but due to the innovative design of the replacement infrastructure, the final cost came in well under budget.   In light of the damage caused to the weir as a result of the 2011 flood event, there was an immediate imperative to repair the weir.  The NCCMA had identified that the weir was surplus to its requirements and advised Council that it intended to replace the structure as a rock weir at a crest level of 89.02m AHD.  After extensive community consultation it was clear that the community’s preference was for the weir to be replaced at the maximum crest level of 89.32m AHD.  Upon completion of the project, ownership of the Quambatook  weir was transferred by Asset Transfer Deed  from the NCCMA to Gannawarra Shire Council.   Council has included the weir on its Asset Register and ongoing  maintenance will be funded and managed by Council.

3.      Specific contribution made by the individual/team you have nominated

The Asset and Design team lead by Brent Heitbaum undertook a thorough analysis and investigation of what outcomes were required whilst scoping the project.  In evaluating the project it was determined that the innovative design of the air operated water control gates system demonstrated technologically advanced design features specific to this application which would achieve all aspects of the project scope.  What has been achieved is a structure which has significantly reduced all occupational Health and Safety risks associated with the previous structure and has increased the serviceability during flood events.  The team’s ability to accept and supervise new innovative designs/construction techniques demonstrates their commitment to deliverable outcomes for their community.

4.      General comments

The refurbishment of the Quambatook Weir and the installation of the innovative air operated gate control system has provided the community of Quambatook with security and a solution to their flood mitigation issues, while maintaining an aesthetically pleasing feature in the centre of the community.  It has also provided relevant agencies with a modern and functional weir operating system that can be managed with reduced risk for personnel and the floodplain environment.