RFI - Attachment D - Geotechnical Investigation Report · MCU25/0053

                                                                                                       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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