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Entrance Works
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Lake Illawarra Entrance Works fact sheet number 1
 

Construction work is to be undertaken in two phases:

 

Phase 1 (Rock Structures)
 

• Northern breakwater measuring 360m long (projecting approx 200m into the sea) with a crest level varying from 2.5m AHD to 4m AHD at the head of the structure.
• Southern breakwater measuring 240m long (projecting approx 200m into the sea) with a crest level varying from 3.0m AHD to 3.5m AHD at the head of the structure.
• Reduction in the width of the gaps in the existing southern training wall to 30m at mean sea level.
• Extension of the Elliot Lake groyne by 20m with a crest level at 3.5m AHD.

 
Contract for Phase 1 work awarded to Coastwide Civil P/L on 1 May 2006.

Start: June 2006
Finish: August 2007

 
The work involves the sorting and placement of 60,000 tonnes of rock.

It is expected that the breakwaters will trap about 50% of the volume of sand which is currently washed into the entrance channel from the Perkins Beach embayment.  Ebb tide flows are expected to transport a large percentage of “in fill” sand back out to sea resulting in less shoaling of the channel and the formation of a sand bar at the breakwater heads.

 

The layout of the breakwater structures has not been designed to provide for safe navigation.  The NSW Maritime Authority is responsible for navigation and will assess entrance conditions once work is complete.

 

Phase 2 (Dredging and Beach Nourishment)

 

• Removal of up to 200,000 cubic metres of sand from the channel with disposal of sand to Warilla Beach.
• Creation of a channel 100m wide x 2m deep from the mouth of the lake to Berageree Island.
• Creation of a bird roosting sand island measuring 220m long x 50m wide with a crest level of 1-1.5m AHD.

 

Contract for Phase 2 work awarded to Neumann Contractors on 14 November 2006.

 
Start: January 2007

Finish: August 2007

 

Notes:

AHD:  Australian Height Datum approximates to mean sea level ie 0m AHD.  Tide levels are normally quoted in hydrographic datum to Indian Spring Low Water (ISLW).  Zero AHD equates to about 0.9m ISLW.  As an example a high tide of 1.6m (ISLW) would be equal to 0.7m AHD and a low tide of 0.4m (ISLW) would equate to -0.5m AHD.

 

For more information contact the Lake Illawarra Authority on (p) 4224 9633 or toll free 1800 467 377.