In 2009, as a drought emergency response to manage lowering river water levels and the risk of emergent Acid Sulfate Soils (ASS) in the lower reaches of the Currency Creek, Finnes River and Goolwa Channel, the SA government installed the Currency Creek Regulator to inundate high risk bed sediments.
Once critical water levels had been raised and maintained, this temporary regulating structure was able to be removed, and Maritime Constructions were contracted to decommission the Currency Creek regulator.
The decommissioning was carried out through the use of a cutter suction dredge and land based civil plant, returning the site as close as practical to original river bathymetry.
Scope of work
Stage 1: A Cutter Suction Dredge (CSD) dredged approx. 22,000m3 of displaced acid sulfate sediments (PASS) located within a 20m wide zone on either side of the Regulator sand core through a floating pipeline to a deeper section within the Currency Creek channel.
Stage 2: Approx. 27,000m3 of dredged sand disposed of into a disposal pond via a 4km long pipeline. Decant water was returned to the creek, with testing in accordance with the Acid Sulfate Management Plan. At completion the pond was decommissioned and dredged sand spread evenly spread over disposal area.
Stage 3: The CSD dredged an estimated 15,000m3 of displaced sediments located within a 50m wide zone of the now removed Regulator sand core. The material was disposed into the void created in Stage 2 through removing the sand core.
Stage 4: Removal of imported rock which formed an access causeway to the Regulator. Civil equipment and an amphibious excavator were used to excavate approx. 1,500m3, which was lime dosed to neutralize the acid sulfate soils
Department of Environment, Water and Natural Resources (DEWNR)
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