Reference Document - Geotechnical Investigation Report MCU25/0053 & OPW25/0074

                                                                                                                    PTG/01608 – 0001 – Rev0


            » BH1 – 0.25 m to 4.50 m;
            » BH2 - 1.50 m, 2.50 m to 3.25 m and 3.75 m to 4.50 m;
            » BH3 – 3.50 m to 4.50 m; and
            » BH4 – 1.25 m and 3.00 m.
            These results are presented in Table 4 to show the distribution of where samples were identified at depth relative to
            each borehole. As borehole BH1 was the closest to the river, it is not unexpected that samples from that borehole had
            the most number of positive results.

            Table 4: Summary of possible PASS, based on initial pHF and pHFOX screening.

               Sample Depth (m)                   BH1                      BH2                    BH3                   BH4

                       0.25                  Possible PASS                   -                      -                     -
                       0.50                  Possible PASS                   -                      -                     -
                       0.75                  Possible PASS                   -                      -                     -
                       1.00                  Possible PASS                   -                      -                     -
                       1.25                  Possible PASS                   -                      -               Possible PASS
                       1.50                  Possible PASS             Possible PASS                -                     -
                       1.75                  Possible PASS                   -                      -                     -
                       2.00                  Possible PASS                   -                      -                     -
                       2.25                  Possible PASS                   -                      -                     -
                       2.50                  Possible PASS             Possible PASS                -                     -
                       2.75                  Possible PASS             Possible PASS                -                     -
                       3.00                  Possible PASS             Possible PASS                -               Possible PASS
                       3.25                  Possible PASS             Possible PASS                -                     -
                       3.50                  Possible PASS                   -                Possible PASS               -
                       3.75                  Possible PASS             Possible PASS          Possible PASS               -
                       4.00                  Possible PASS             Possible PASS          Possible PASS               -
                       4.25                  Possible PASS             Possible PASS          Possible PASS               -
                       4.50                  Possible PASS             Possible PASS          Possible PASS               -

            On the basis that PASS had been identified, CRS testing was carried out on a selection of samples to confirm the
            presence and severity of PASS.

            The texture of the soil sediment influences soil behaviour and therefore treatment required if excavated. The %S and
            TAA action criteria thresholds for different soil textures are shown in Table 5. Based on the provided information, it
            has been assumed that more than 1,000 tonnes of soils will be disturbed below RL 5 mAHD. The following table is
            referenced from the ‘Queensland Acid Sulfate Soil Technical Manual, Soil Management Guidelines V5.1’.

            Table 5: Action Criteria Thresholds for Soil-Lime Treatment

                                                              1 – 1000 tonnes disturbed                 > 1000 tonnes disturbed
                  Texture                                                        Equivalent                           Equivalent
                                       Texture Range
                  Category                                   Equivalent           Acidity –         Equivalent         Acidity –
                                                             Sulfur - %S         TAA (mole          Sulfur - %S       TAA (mole
                                                                                 H+/tonnes)                           H+/tonnes)
                                       Sands to loamy
                   Coarse                                       0.03                   18
                                       sand and peats
                                       Clayey sands to
                   Medium                                       0.06                   36
                                          light clays                                                   0.03                  18
                                       Light, medium
                     Fine               to heavy clays          0.10                   62
                                        and silty clays

            As more than 1000 tonnes of material will be disturbed, the applicable action criterion is 18 mol H+/t.

            The action criterion was breached in half of the soil samples tested, nine in total. At least one sample from each
            borehole exceeded the criteria, with borehole BH1 again returning the most number of positive results. The lowest Net

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Document Set ID: 24149758
Version: 1, Version Date: 26/09/2025