Background and importance
Construction to raise the Murrumbidgee River levee system in Wagga Wagga will start in October 2017, giving residents for the first time a 1 in 100 year level of protection against flooding.
Strengthening the levee system will help safeguard the central business district, many of the city’s critical assets and thousands of homes.
The journey from concept to construction has been a complex process and Wagga Wagga City Council staff have been working tirelessly in the background to ensure the project is executed to the highest standard, and that what is built, is considered and built to last.
Community consultation has been vital throughout the levee upgrade process. Feedback, suggestions, ideas and advice collected from the many community sessions and forums have helped inform final designs and decisions.
Where is the levee upgrade project up to?
Keep up to date on the latest project news and information on the project diary page
How will the levee upgrade be constructed and how long will it take?
The Main City Levee upgrade will be delivered through a staged construction.
Stage 1 – consists of two levee sections:
Section 1: Flowerdale, including spillway, to Wiradjuri Bridge
Section 2: Copland Street, including spillway, to Kooringal Road Monumental Cemetery
Note: Spillways are built to allow for controlled entry of water over the levee system if a flooding event exceeds the design height of the levee. Wagga’s Murrumbidgee levee system has two spillways, one in the downstream side at Flowerdale (see video below), the other in the upstream side at Kooringal.
Stage 2 - Gobbagombalin Bridge to Cadell Place wall (parallel to Fitzmaurice Street) to Johnson Street, then from, Riverina Playhouse to Hammond Avenue.
Stage 1 is expected to be complete by January 2019.
Stage 2 construction starts in January, 2019 and will be complete by mid-2020.
Options for a North Wagga Levee are currently being considered. Any works that proceed in North Wagga will be Stage 3 of the levee upgrade project.
How is the levee upgrade being funded?
At a cost of about $23M to upgrade Wagga Wagga's levees, Council and ratepayers simply cannot fund the entire levee upgrade project. Financial contributions are needed from all three levels of government to fund the project.
The following funding contributions have been made to cover the $23M cost of the Wagga Wagga levee upgrades:
- City of Wagga Wagga - raising one-third share of $7.75M through a special rate variation, effective from 2016 and maintained for five years
- State Government - stage 1 grant funding of $2M and stage 2 grant funding of $2.1M
- Federal Government - $10M funding under the Community Development Grants Programme
Note: Costing of $23M is pending tender processes and/or variations.
What will construction look like?
Stage 1 of the levee consists of embankment levee earthen works and construction of two concrete spillways. Residents will see movement on the banks of the levee from September 2017 for site preparation works. Excavators will move in from October, starting at the Flowerdale section of the levee, moving around to the Wiradjuri Bridge. Works will then start on section 2, starting at Copland Street and moving south towards Kooringal Road Monumental Cemetery.
The works include removing the existing topsoil and grass, shaping and scraping the existing levee to allow for key-in of the new material and compacting the new levee to the required standards. The slope and shape of the levee is designed to minimise erosion and will be finished off with a decomposed granite surface allowing for all-weather access and reducing moisture entry into the clay bank.
In total, machinery will move 25,000 cubic metres of clay, topsoil and granite as part of the stage 1 upgrade of the levee.
The Wagga Wagga levees are designed to cater for a specific design flood and include a freeboard allowance of about 900mm. The design is based on analysis of historical data and extensive hydraulic modelling to determine flood levels along the length of river in the floodplain around Wagga Wagga.
Common practice when building a levee is to place a spillway in the levee. These spillways are designed to allow floods that are in excess of 500mm above the design height to enter protected zones in a controlled manner. Two concrete spillways will be included in Stage 1 of the levee upgrade, one on the downstream side at Flowerdale, across the Olympic Highway from the former Alan Staunton Park, 350metres wide. The second on the upstream side, parallel to Kooringal Road, just upstream from Copland Street, 100metres wide.
Stage 2 will comprise of predominately capped sheet piles that will protrude from the earth levee running the length of the Cadell Place wall (parallel to Fitzmaurice Street) to Johnson Street, then from, Riverina Playhouse to Hammond Avenue. In addition to the sheet piling, raising and extending the existing concrete retaining walls along Cadell Place and behind Watermark apartments, will also be part of this stage.
What is sheetpiling?
Sheetpiling will occur where there is limited space on the existing levee and not enough room to use earth to raise the height of the levee.
Stage 2 will involve just under two kilometres of sheet piling. A 30-metre stretch of sheetpiling has been built along Tarcutta Street as a demonstration.
The process involves driving steel sheets approximately 2.7 m into the ground to create a wall along the levee bank that is approximately one metre high and achieves a 1 in 100 year level of protection against flooding. The wall will be capped with aerated concrete blocks. Council has worked with a local artist to design an artwork to be installed along sections of the capping.
Designated access points have been incorporated into the sheetpiling design to enable access to the riverside.
During construction will there be impacts to residents?
What levee works are underway at Kooringal Rd?
As part of Stage 1, a new 800m section of levee is being constructed from the Monumental Cemetery to the disused railway line where it will join with the existing levee bank. The new section of levee is being constructed in accordance with Wagga Wagga’s 1 in 100-year flood planning strategy.
The existing levee - directly opposite the Exhibition Centre Netball Courts – is being reinforced, widened and a 130m concrete spillway built as a flood mitigation protection.
Head walls on either side of Copland Street are also under construction. In the event of a major flood additional temporary barriers are locked in to these strong structures to secure the levee.
Stage 1 of the levee project at Kooringal Road is scheduled for completion by January 2019.
Will a bike path be built on the levee bank at Kooringal Road?
How have residents been consulted throughout this project, and, will there be updates throughout the delivery of the project?
Wagga Wagga City Council continues to have conversations with the Wagga Wagga community in respect to flood management. Council staff have met face-to-face, or had phone conversations with landholders directly affected by the project. Direct updates will be provided to these landholders as the project progresses.
A dedicated projects page for the levee upgrade can be found on the Wagga Wagga City Council website, www.wagga.nsw.gov.au/levee(external site). Updates will also be available via Council’s social media pages and through Council News. residents are encouraged to sign up for updates via email. Subscribe at the top of this page.
Are there any environmental impacts?
As with any project of this size and complexity, a full and comprehensive Review of Environmental Factors (REF) was required and subsequently completed by Wagga Wagga City Council staff.
The Review of Environmental Factors identified that the levee upgrade concept is environmentally, socially and economically beneficial to the wider Wagga Wagga community and there was no requirement to carry out a broader Environmental Impact Assessment.
What about North Wagga?
In July 2015 the Council resolved to proceed with the construction of the Main City Levee to provide a 1 in 100 year level of protection, making allowances for the possibility that the North Wagga Levee may also be constructed to provide up to a 1 in 100 year level of protection.
A final position on upgrading the North Wagga Levee is dependent on decisions voted on by the Floodplain Risk Management Advisory Committee as part of an overall update of the Wagga Wagga Floodplain Risk Management Study and Plan. This study and plan are currently being finalised. A report recommending to place the draft study and plan, including options for North Wagga, on public exhibition is expected to go before the Council in the coming months.