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

                                                                                                                                              PTG/01608 – 0001 – Rev0



                                                             Difference in pH following oxidation
                             0
                            0.5
                             1
                            1.5
                             2
                Depth (m)




                            2.5
                             3
                            3.5
                             4
                            4.5
                             5
                                  0          1                   2                  3                  4                   5                  6                   7
                                                                               pH difference (pH units)

            Figure 6: Change in pH following oxidisation. The pink area indicates a change in pH of greater than 1.0 pH units.

            After receiving the results of the above screening testing, one quarter of the samples were selected for follow up
            Chromium Reducible Sulphur (CRS) suite testing. Samples were selected based on screening results that indicated a
            large pH difference, a higher reactivity number and/or lower pHFOX results, whilst ensuring a representative spread of
            sample depths and boreholes. A summary of the CRS testing is presented in Table 3 below. The detailed laboratory
            results are attached in Appendix 3.

            Table 3: Summary of Chromium Reducible Sulphur (CRS) test results
                                                                                                                                  Acid
                                                                                   Actual               Potential
                                       Sample                                                                                  Neutralising        Net Acidity
               Borehole ID                                   Material              Acidity               Acidity
                                      Depth (m)                                                                                 Capacity            (mol+/ t)
                                                                                  (mol+/ t)             (mol+/ t)
                                                                                                                                (mol+/t)
                                          0.5                  SAND                     13                    13                    0                     26
                                          1.75                 SAND                      2                    11                    0                     13
                            BH1           2.75                 SAND                     14                   41                     0                     55
                                          3.25                 SAND                      8                   61                     0                    69
                                          4.0                  SAND                      8                   77                     0                     85
                                           1.5                 SAND                     <2                    11                    0                     11
                                          2.25                 SAND                     <2                    11                    0                     11
                            BH2            2.5                 SAND                     74                   16                     0                    90
                                          3.0                  SAND                      4                    11                    0                     16
                                          4.25                 SAND                      8                    51                    0                     58
                                          2.25                 SAND                     <2                   14                     0                     14
                                          3.75                 SAND                      4                    12                    0                     16
                            BH3
                                          4.0                  SAND                      6                   121                    0                    128
                                          4.5                  SAND                      4                   58                     0                     63
                                          1.25                 SAND                      2                    15                    0                     17
                                          3.25                 SAND                     <2                   41                   <10                     37
                            BH4
                                           3.5                 SAND                     <2                   42                    121                   <10
                                          4.5                  SAND                     <2                   40                    111                   <10
            Note: The highlighted Net Acidity values have exceeded the relevant action criteria as outlined in the National Acid Sulfate Soil Guidelines, assuming less
            than 1,000 tonnes of soil are disturbed below RL 5m AHD.




            8 ACID SULFATE SOILS COMMENTS
            AASS are typically indicated by pHF results below 4.0. None of the samples tested exceeded this criterion. The lowest
            pHF result was 4.7 as recorded in the 2.75 m sample from borehole BH2.

            Possible PASS are typically indicated by pHF results above 4.0 with a pHFOX result below 3.0 after a reaction to added
            peroxide. The following samples tested met this criterion:
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Document Set ID: 24149758
Version: 1, Version Date: 26/09/2025