State Water Corporation / Construction of Lake Wetherell Fuse Plug Embankments and Levees at Menindee - SWCDoc14/2466

There are four main lakes in the system including Lake Menindee, Lake Cawndilla, Lake Pamamaroo, and Lake Wetherell. Lake Wetherell is one of the uppermost lakes, and is formed by the combination of a block dam in the Darling River, the Lake Wetherell Outlet Regulator, the Menindee Main Weir and a series of levees. Lake Wetherell plays a pivotal role in the operation of the system since it diverts water into all the downstream lakes via the Lake Pamamaroo inlet regulator.

The Lake Wetherell East levee extends from the Main Weir to sand hills near Windalle homestead and incorporates a fuse plug spillway. The role of this existing fuse plug (constructed in the late 1950’s) has been to safely divert Darling River flood flows that are greater than the capacity of the Main Weir (approximately 110,000 ML/day). 

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

This raised serious 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 minimise erosion and also to ensure that the design flood requirements were met.

Following an extensive investigation, it has been proposed to relocate the fuse plug further downstream of Three Mile Creek, which will minimise erosion along the river bank, and also divert incoming flood flows that are in excess of the capacity of the Main Weir without overtopping the eastern levee and block bank.

State Water has determined to proceed with construction of a new fuse plug arrangement. The works under this contract incorporate:

• a new fuse plug constructed by excavating and trimming the existing levee downstream of Three Mile Creek with crest length 1,500 metres, divided into two bays;
• raising of the lowered section of the existing fuse plug to convert it into a levee by transporting the materials from the above excavation;
• supply and install sheetpiles to divide the proposed new fuse plug into two bays;
• erosion protection works by cement soil mixing, as shown on the tender drawings.   

None.

Outlined in the RFT documents.

15 Weeks.