State Water Corporation / Expression of Interest (EOI) for Construction of Lake Wetherell Fuse Plug Embankment and Levees at Menindee - SWCDoc12/31350

Menindee Lakes, which are owned and operated by State Water, represent a significant natural, cultural and economic resource for Australia. There are four main lakes in the system including Lake Menindee, Lake Cawndilla, Lake Pamamaroo, and Lake Wetherell (comprising a number of smaller lakes and the channel of the Darling River), comprising three off-stream storages and one river storage - Lake Wetherell, which is located 10 km north east of Menindee.

The Lake Wetherell storage is formed by the Main Weir and a series of levees, the longest of which is the 32 km Eastern Levee that prevents the spread of water storage in the direction of the Talyawalka Creek.

There is an existing fuse plug at Lake Wetherell, which was constructed over several years and completed in late 1950’s, to divert incoming flood flows that are in excess of the capacity of the Main Weir.

The fuse plug has only operated on one occasion in 1974, which identified substantial problems with scouring and difficulty in stemming flow once activated. Given the very close proximity of the fuse plug to the river, headwall erosion progressed through the fuse plug to within only a couple of metres of the Darling River channel.

This raised some concern in regard to formation of a gully, which could lead the river system to branch out into the flood plain. Therefore, there was a need for reviewing the fuse plug arrangement and its operation to reduce erosion risk and also to ensure that the design flood requirements are met.

State Water has undertaken studies, and revised the fuse plug arrangement in order to minimise the risk of erosion, and also to divert incoming flood flows that are in excess of the capacity of the Main Weir without overtopping the eastern levee.

An environmental assessment (Part 5) was completed of the proposed works area, and Public Works developed the concept design for the proposed fuse plug arrangement. The concept design report (May, 2012) is attached for reference.

Currently, detailed design and documentations are in progress, and expected to be complete in Sept 2012.

Expressions of Interest (EOI) are invited from organisations wishing to be pre-registered to tender for the proposed contract for “Construction of Lake Wetherell Fuse Plug Embankments and Levees at Menindee”.

The scope of work includes:

• Modification of the existing levee to incorporate the proposed fuse plug profiles,
• Provision of a 5% cement stabilised layer at the downstream toe of the levee,
• Installation of sheet piles to create a two bay fuse plug system,
• Raising the existing fuse plug to match the adjacent levee,
• Removal and disposal of trees on the embankment batters by cutting.

The proposed contract will incorporate the GC21 General Conditions of Contract.

Further details can be obtained from the attached EOI document.

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