6. Noosa River DMP Ver0 (Combined)

                                                                    Noosa River - Sediment Sampling Report
                                                BMT (OFFICIAL)




5 Conclusions

    ̶
The key findings of this study are as follows:

•       The vibro-corer was able to obtain target core depths, at all sites except BH2 and BH7 due to
        impenetrable clay/gravel material.
•       Sediments were dominated by sand (0.06-2 mm) fractions with an average of 93% sand.
•       The 95% UCL of the mean did not exceed the NADG Screening Levels or NEPM guideline values
        for any metal or metalloid at all sampling locations and with each sub-sample
•       Total nitrogen (TN) and total phosphorus (TP) were typical higher in the upper strata and highest
        downstream of the Noosaville canals (BH3 and BH4). Inorganic forms of nutrients (ammonium,
        nitrate, and nitrite) were either below laboratory LORs or recorded at very low concentrations. There
        are no NAGD Screening Levels or NEPM investigation levels for nutrients.
•       There were no detections of the organic compounds BTEXN, Organotin compounds,
        Organophosphorus Pesticides or Organochlorine Pesticides. Detection of hydrocarbons at site BH3
        and BH4 were well below the NAGD screening level.
•       PFAS compounds were recorded below the LOR for each sample.
•       Based on this assessment of ASS analytical results, the following is concluded:
        -   TAA (<2 mole H*/t) was not detected in any of the samples, indicating the sediments are not
            considered to contain actual ASS. The only exception was site BH8 (0.5 – 1.0m) which recorded
            4 mole H+ / t TAA.
        -   CRS results ranged from 0.037 to 0.388 %S, indicating PASS are likely to be disturbed during
            the dredging.
        -   Moderate to a large amount of ANC was detected in all sub-samples ranging from 0.05 to 2.66
            % CaCO3
        -   Net acidity (excluding ANC) ranged from 0.04 to 0.39 %S relating directly to the potential acidity
            as no actual acidity was recorded (other than site BH8). The net acidity (excluding ANC)
            exceeded the National acid sulfate soils action criteria of 0.03% S at several sites, as such
            requiring management. Management of PASS material should be defined in a dredge
            management plan for the dredge material.
•       Data validation through laboratory and field QA/QC showed that the data are valid to allow an
        assessment of sediment quality against the NAGD and NEPM guidelines.
Overall, the sediments were relatively clean with no analytes exceeding the relevant NAGD screening
levels or NEPM investigation levels, thus would be suitable for offshore or land-based disposal, with
suitable PASS material management.




A10342 | 005 | 01                                       30                                         14 April 2022