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Wingate Dam Unlocks New Water Source For Barossa Valley

McMahon Services successfully deliver new water storage dam in Adelaide’s Northern region.

McMahon Services worked closely with Bunyip Water and HydroPlan as part of the Gawler Water Re-use Scheme (GWRS), a key step in a program to unlock new sources of water in the Barossa Valley.

The GWRS emanated from the creation of a large borrow pit adjacent the Gawler River, excavated to source fill material for the construction of the Northern Expressway. The pit provided a significant opportunity to harvest urban stormwater runoff from the Gawler River catchment when flows are above the environmental threshold (616L/s), and store it in the new and existing dams in the Barossa region, and the nearby Kangaroo Flat underground aquifer for subsequent reuse in Summer.

The water will be piped to a holding dam from where it will be ready for the foundation customer’s use for urban irrigation in Hewett and vineyards in the Western Barossa Region.

The project involved the construction of a flow gauging station, three pump stations, a 430 mega litre storage basin and all associated pipe and ancillary works.

McMahon Services were responsible for delivering all works including land clearance, site preparation, demolition of existing infrastructure and bulk earthworks to form both basin structures.

The basin structures were formed using site won clay material, cut and filled to form a 600mm clay layer, and incorporated a HDPE lined sump scour protection in the form of reno mattresses and rock lining. This was placed at the inlets of the dam structure to protect the clay liner from erosion.

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McMahon Services also undertook the supply and installation of a complex network of pipework infrastructure to connect the dam system to the upstream supply and downstream consumer. This included pumps to the three pump stations, valve assembly and over 1000 lineal metres of pipeline, varying in diameter from 32mm to 320mm. The project required the supply and installation of all high and low voltage electrical conduits, as well as underground communications infrastructure.

Hard landscaping works consisted of an access road running along the top of the dam embankment, a heavy vehicle turning zone and maintenance vehicle carpark.

The final works included the installation of all stormwater pipework, headwalls, swales and drains, as well as all soft landscaping including spreading of topsoil to bank slopes, hydro-mulching and planting of native vegetation.

Project Challenges

Due to the depth of the pipe risers, the valve assembly was fabricated prior to installation within the chamber. McMahon Services designed and fabricated a complex steel frame to ensure verticality upon lifting and placement.

The inlet pit cover design was also changed from original design to allow for a single sheet of fibre-reinforced plastic to be slid on and off the top of the lid and held down with four bolts. This option ended up being much lighter and easier to remove than the original heavier design that called for an aluminium cover raised in 4 x 4 metre sections.

A significant sustainability initiative for the region, the dam will substitute at least 800 mega litres per annum of River Murray water used in the Barossa, with stormwater harvested on the vineyards. HydroPlan irrigation design engineers have enhanced the water security by connecting to treated wastewater from Bolivar, and providing for managed aquifer recharge expansion to include stormwater anticipated from the Roseworthy Township Expansion.

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