PTG_00259 - 0001 - Rev0 - Geotechnical Investigation Report (1)

                                                                                                                            PTG Consulting
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                                                                                                                 www.ptgconsulting.com.au



6. GEOTECHNICAL MODEL
In summary, the soil profile encountered within the borehole comprised silty sand fill to 2.6 m depth overlying
natural silty sand to the termination depth of 6 m.

Dynamic Cone Penetrometer (DCP) testing indicated:
•   The silty SAND varied in density from loose grading to dense with depth.

Groundwater seepage was encountered within the borehole at an estimated depth of 2.4 m. It should be noted
that groundwater levels can be perched and fluctuate seasonally and during and after heavy rainfall events.
Given this natural variability, it is prudent to assume that water levels can fluctuate.


7. LABORATORY TESTING AND RESULTS
NATA accredited laboratory testing was undertaken on selected representative soil samples recovered from the
boreholes in accordance with ‘AS1289-Methods of Soil Testing for Engineering Purposes’. The laboratory testing
aimed to determine typical soil behaviour characteristics for engineering assessment.

The laboratory testing comprised the following:
•    Particle size distribution tests; and
•    Atterberg Limit.

The Laboratory Test Result Reports are included in Appendix 3 and are summarised in the table below.

Table 1: Summary of Laboratory Test Results
                                          Fines                      Sand               Gravel
Borehole    Depth (m)      Material      < 75μm                     75μm –            2.36mm –          LL (%)   PL (%)    PI (%)     LS (%)
                                            (%)                   2.3mm (%)           63mm (%)

  BH1           2.5 – 2.9          SAND                7              93                   0              39      NP         NP         0
Note: LL – Liquid Limit, PL – Plastic Limit, PI – Plasticity Index, LS – Linear Shrinkage, NP – Non Plastic


Additionally, Acid Sulphate sampling was undertaken per the ‘Guidelines for Sampling and Analysis of Lowland
Acid Sulphate Soils in Queensland 1988, QASSIT Appendix A’ by the Department of Natural Resources.

Testing included field pHf, pHFOX and reaction with hydrogen peroxide in order to arrive at a ‘positive field
sulphide identification’ for subsequent selection of samples for further chromium suite testing. Results of the
testing are attached in Appendix 3.

Using these 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 (following
    oxidation) of less than 3 strongly indicates PASS.
Table 1 and Figures 1 to 3 show the pH screening test results and indicates which results fell below the action
criteria (pink zones). The test results highlighted in Table 9 and identified with a red circle in Figures 4 to 6
indicate the samples which were selected for the chromium suite.




PTG/00259 – 25 Wyuna Drive, Noosaville                          Page 7 of 15                                                28 June 2024