Riverina Western Imperial Lake Dam Decommission

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Gavin Priestley Regional Director 02 6339 5900

What goes up, must come down.

When Essential Water no longer required Imperial Lake Dam as a water supply source for Broken Hill, they called on Public Works to advise on, and manage, the de-commissioning process.

Located about 5 km north-east of the city centre, Imperial Lake Dam was designed and constructed by the NSW Public Works Department in 1888 as a water supply for Broken Hill. It is a curved zoned earth-fill embankment with a spillway cut through the rock on the left abutment. In 1967 North Broken Hill Mining Ltd reconstructed and enlarged the dam to supply water for its mining operations, and in 2000 Essential Water took ownership of the dam as an additional emergency water supply for the city.

Water supply to Broken Hill and surrounding communities is now secured by a pipeline from the Murray River, and to continue operating the dam would require ongoing dam maintenance and management duties as prescribed by Dams Safety NSW.  Public Works' Dams team were tasked to investigate options to de-commission the dam.

"Following our investigations and assessment of concept design options, cutting down the existing dam embankment to form a low-flow weir structure was determined to be the most direct and inexpensive method” said George Samios, Principal Engineer Dams. “A low-flow weir refers to a slot in the embankment that would immediately ’trigger’ or release dam flood inflows. This conforms with our underlying design philosophy of ‘what comes in goes out'"

Construction of the decommissioning works were managed by Peter McGaffin from our Dubbo Regional Office.