Reference Document - OPW25 0085 (AS Published)

4.7           Subsurface Conditions
Subsurface conditions encountered in the test pits are summarised as follows:
      Topsoil – comprising either loose, silty sand or firm and stiff clayey silt from the ground surface to
       depths between 0.17 m to 0.3 m BGL; then
      Residual Soils – comprising either initially loose, becoming medium dense to dense with depth,
       clayey sands or silty clays/clayey silts of high plasticity/liquid limit and initially of stiff consistency,
       quickly becoming very stiff and hard to depths between 0.8 m and 3.2 m BGL (test pit target depth in
       TP2 & TP4); underlain by
      Weathered Sedimentary Rock – being either highly weathered sandstone (Test Pit TP1) or siltstone
       (TP3 and TP5 to TP12), initially being very low strength, then generally grading to low strength (or
       stronger) to target depths of 2.3 m to 3 m BGL.
Table 1 summarises the subsurface profile in each test pit. Text Figure 10 overleaf provides and
illustration of the typical subsurface profiles encountered within the sandstone and siltstone profiles.
Detailed descriptions of the subsurface conditions encountered in the test pits are provided in the
reports attached in Appendix A, along with definition sheets which describe terms and abbreviations
used on the reports.

Table 1: Summary of Subsurface Profiles

                                                                                Residual Soil
                                                    Residual Soil                                           Weathered
    Test Pit No.           Topsoil                                           Medium Dense /
                                                   Loose or Firm                                         Sedimentary Rock
                                                                             Stiff (or stronger)
        TP1                0.0 – 0.2                   0.2 - 0.6                   0.6 – 1.1                  1.1 – 2.3 *
        TP2                0.0 – 0.3                   0.3 – 0.6                   0.6 – 3.0                      -
        TP3                0.0 – 0.3                      NE                       0.3 – 1.6                  1.6 – 3.0
        TP4                0.0 – 0.2                   0.2 – 0.4                   0.4 – 3.0                      -
        TP5                0.0 – 0.2                      NE                       0.2 – 1.1                  1.1 – 3.0
        TP6                0.0 – 0.2                      NE                       0.2 – 1.1                  1.1 – 2.7*
        TP7                0.0 – 0.2                      NE                       0.2 – 1.2                  1.2 – 2.6 *
        TP8               0.0 – 0.17                      NE                       0.17 - 0.8                 0.8 – 2.5 *
        TP9                0.0 – 0.2                      NE                       0.2 – 2.0                  2.0 – 3.0
       TP10                0.0 – 0.2                      NE                       0.2 – 1.7                  1.7 – 2.7*
       TP11                0.0 – 0.2                      NE                       0.2 – 0.9                  0.9 – 3.0
       TP12                0.0 – 0.2                      NE                       0.2 – 1.4                  1.4 – 3.0
Notes: 1.          Depths noted in m BGL at time of investigation (13 & 19 December 2024)
        2.         NE denotes not encountered
        3.         * denotes test pit terminated due to very slow digging, toothed bucket or ripper refusal




Geo-Environmental Investigation for Proposed Subdivision
7 February 2025 | 24386-001-Rev0                                                                                            9