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

                                                                                                                            PTG/01608 – 0001 – Rev0


            From the guidelines:
            •        A measured pHF less than 4 indicates that oxidation of sulfides has probably occurred in the past, indicating
            that AASS could be present; and
            •        A strong reaction with peroxide, a pHFOX at least one unit below the measured pHF, and a pHFOX of less than
            3 strongly indicates PASS.

            Figures 4 to 6 below present the Table 2 results graphically and indicate which results indicate the presence of either
            Actual or possible Potential Acid Sulfate Soils (within the pink zones). The samples that were selected for follow up
            testing are circled in red.


                                                              Field pH measurements
                             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        8       9       10      11      12         13   14
                                                                        Field pH (pH units)

            Figure 4: Field pH test results. The pink zone (pH < 4) indicates the possible presence of AASS.


                                                               pH(fox) measurements
                             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        8       9       10      11      12         13   14
                                                                         pH(fox) (pH units)

            Figure 5: Field pH after peroxide (pHFOX) test results. The pink zone (pH < 3) indicates the possible presence of PASS.




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