OPW052025 Report - Part 2

in slope towards the base of this rise, and encountered an upper layer of basaltic slopewash,
transitioning to residual soils, extremely weathered (XW) material and weathered phyllite below. The
finished excavation for test pit TP3 is shown below in Text Figure 10 for information.




                                                                             Residual soils/XW material of the
                                                                             Kin Kin Beds



                                                                            Dark red brown coloured basaltic
                                                                            slopewash




                                 Text Figure 10: Finished excavation - test pit TP3

4.2.2         Subsurface Conditions
Figure 1 (attached) shows the locations of the test pits. The detailed logs and explanatory notes can be
found attached in Appendix A.
Test pits TP1 to TP3 were excavated progressively from lower ground to the east/north-east to higher
ground in the south-west. These were focussed around the crest of the ridgeline forming the alignment
for the proposed driveway, with the results summarised as follows:
▪    Test pit TP1 was located on the northern facing part of the ridgeline approaching the existing sheds.
     The pit encountered topsoil to 0.2 m BGL, underlain by residual soil of firm to stiff, silty clay to 0.8 m
     BGL, where XW material (described as medium dense gravel and highly weathered phyllite) occurred
     to 1.3 m BGL. Following this, highly weathered very low to low strength phyllite was logged with the
     test pit terminated due to slow digging at 2.5 m BGL.
▪    Test pit TP2 was excavated at the saddle to the southern edge of the site, where topsoil was logged
     to 0.1 m BGL underlain by hard, residual gravelly clay soil, then very low strength weathered phyllite
     to 1.1 m BGL, where the phyllite graded to low strength. It was possible under slow excavation
     conditions to dig to 2.6 m BGL, where the test pit was terminated.
▪    Test pit TP3 was positioned below the final rise up to the proposed residence (Ref. Text Figure 10
     above). The subsurface profile consisted of slopewash to 0.25 m BGL, then residual soil and XW
     material of stiff to very stiff, silty clay with varying gravel content to 2.5 m BGL, where highly

Geotechnical Investigation & Slope Stability Assessment
9 April 2025 | 25050-001-Rev0                                                                                    9