Scope
The scope of work included:
- excavation and placement of 270,000m3 of earthworks
- placement of 110,000m3 of pre-load to Stage 21
- construction of five high efficiency sediment basins
- treatment of acid sulphate soils using almost 10,000 tonnes of lime
- placement of 780 metres of concrete revetment walls
- construction of 1 kilometre of sandstone boulder wall
- installation of 1.3 kilometres of saltwater exchange PE pipe rising main including 925 metres of DN500mm PE rising main pipework
- construction of a saltwater exchange pump station
- electrical control works for the saltwater exchange
- construction of an asphalt access roadway to pump station
- construction of lake outlet culverts.
Outcomes
The project team overcame environmental challenges through effective staging of excavation works, efficient treatment of acid sulphate soils using almost 10,000 tonnes of lime, and successfully undertaking lake outlet works within environmentally sensitive zones.
Water quality testing was required and undertaken throughout works to comply with strict environmental approvals. Twelve groundwater monitoring stations were sampled weekly to test water for PH, suspended solids, dissolved aluminium, total iron and ferrous iron. The groundwater level was also tested to ensure the lake excavation works did not impact on the water table, and water quality was tested upstream and downstream, and compared with baseline results to ensure the excavation did not impact on water quality downstream of the works.
