Noosa River DMP V1

Pacific Geotech 2023
Subsequent geotechnical investigations and assessment regarding acid sulfates were undertaken by Pacific
Geotech (January 2023), with the following detail regarding acid sulfate management:
          “The initial testing indicated an acid sulfate hot spot in the area of BH08. This additional testing has confirmed
          the material initially encountered has either been naturally scoured away or is of such an isolated volume so as
          to not be significant and acid sulfate treatment will not be required. It is possible that the material was related to
          sediment build-up at the outlet of the stormwater drain but this is not considered to be an issue now.”

          “The results of the earlier laboratory testing have been reviewed. Considering the proposed dredging
          methodology (ie. use of a cyclone separator) and the natural buffering capacity of the sands, treatment for the
          acid sulfate neutralisation is not likely to be required. This should be confirmed with validation testing at the time
          of the dredging operation. Validation testing should be undertaken at a rate of 1 test per 250m3 of disturbed
          material.”

          “On the basis of the testing undertaken, all samples provided nett acidity values below the QASSIT defined
          action criteria. Therefore, soils disturbed on-site do not require treatment for acid sulfate potential.”

Summary
As such, the sandy sediments are considered to be suitable for nourishment, acid sulfate treatment is not required
and the material is uncontaminated in accordance with NAGD 2009.

                  Marine Plants
Marine plants include mangroves, seagrass, samphires, saltcouch and saltmarsh plants, algae and other tidal
plants growing adjacent to the tidal zone, landward and seaward. They provide important habitat for fish and are
protected against deliberate damage or destruction under the Fisheries Act 1994.
Biome Consulting have undertaken a marine plants survey on the foreshore at Hilton Esplanade, Gympie Terrace
and Munna Park (Appendix D). The scope of this survey focussed on areas proposed to be dredged and
nourished; it did not include the entire foreshore extent as the presence of marine plants changes over time and
the potential for nourishment to impact on existing marine plants depends on the state of the foreshore at the time
of the works and many sections of foreshore are accreted and currently do not require nourishment.
The following advice is summarised from the report:
        “The marine plants on the foreshore and intertidal zone of the river have the potential to be impacted by
        the uncontrolled placement of sand over root zones. Where present, seagrasses have the potential for
        direct and indirect disturbances from sand extraction.”
        “Seagrass surveys were undertaken by wading the shallow areas of the extraction and nourishment sites
        and using an underwater drone in the deeper areas. No seagrass was recorded.”
        “Marine plants growing in the intertidal and foreshore areas were recorded along the Gympie Terrace and
        Hilton Esplanade foreshores and included mangroves (Avicennia and Rhizophora species) and
        Casuarina glauca. No marine plants were recorded at Munna Park.”




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