MCU25 0087 - Reference Document - Geotech assessment report (As Published) · MCU25/0087

        4.4             Subsurface Conditions
        Detailed descriptions of the subsurface conditions encountered in the boreholes are provided in the
        borehole reports attached in Appendix A, along with definition sheets which describe terms and
        abbreviations used in the reports. Subsurface conditions encountered in the boreholes are summarised
        below and are illustrated as a cross-section in Figure 2 (attached at the end of report text).
        The subsurface conditions encountered in the boreholes surrounding the existing residence comprised
        initially loose clayey and silty sand fill to depths of 0.4 m and 0.5 m BGL in boreholes BH1 and BH2,
        respectively. Then, very loose to loose natural sands were encountered to depths of 0.4 m and 2.4 m in
        boreholes BH1 and BH2, respectively. Below this in borehole BH1, medium dense sand was encountered
        to a depth of 1.2 m BGL, overlying dense (or denser) sand to the borehole termination depth of 4 m BGL.
        In borehole BH2, medium dense sand was encountered to the borehole termination depth of 3 m BGL,
        with downhole DCP testing indicating the presence of dense sand below 6.5 m BGL.
        Standalone DCP testing undertaken across the dune to the east of the site indicated loose natural sand
        to depths of 1.3 m to 1.8 m BGL, then becoming medium dense to depths of 1.9 m to 2 m BGL, overlying
        dense (or denser) sand to the DCP termination depths.
        Table 1 below provides a detailed summary the subsurface profiles encountered in each borehole and
        standalone DCP test (presented left to right from west to east direction, western boundary of site to high
        foredune toe).

        Table 1: Summary of Subsurface Profiles

          Material / Test Location     BH2              BH1                DCP1           DCP2          DCP3

          Loose Sand Fill              0.0 – 0.5        0.0 – 0.4          NE             NE            NE


          Very Loose to Loose          0.5 – 2.4        0.4 – 0.4          *0.0 – 1.4     *0.0 – 1.9    *0.0 – 1.5
          Natural Sands

          Medium Dense Natural         2.4 – 5.0*       0.4 – 1.2          *1.4 – 2.0     *1.9 – 2.1    *1.5 – 2.0
          Sands

          Dense (or denser)            *5.0 – 6.9TD     1.2 – 4.2R         *2.0 – 2.9TD   *2.1 – 2.2R   *2.0 – 2.3R
          Natural Sands

        Notes:
              1. Depths noted in m BGL at time of investigation (24 September 2025)
              2. NE Denotes not encountered
              3. * denotes materials inferred from DCP results
              4. TD denotes DCP test termination depth
              5. R denotes DCP refusal


        4.5             Groundwater
        No signs of groundwater seepage (‘springs’) were observed at the ground surface during our walk-over
        and no groundwater was encountered in the boreholes. It is expected that an unconfined groundwater
        table would exist below the toe of the dune, close to sea level, and fluctuate with tidal and weather
        conditions. The groundwater level is anticipated to rise slightly under the dune moving west.




        Geotechnical investigation
        19 November 2025 | 25289-001-Rev0                                                                             8
Document Set ID: 24631529
Version: 1, Version Date: 24/03/2026