Appendix F - Geo-Environmental Investigation Report · RAL24/0003

                                      PROPOSED SUBDIVISION
                                      41 TALLOWWOOD PLACE, BLACK MOUNTAIN

4.3           Geology
The 1:100,000 scale Gympie Surface Geological Map 2 (Ref. Text Figure 9) indicates that the site is underlain
by materials derived of the early to middle Triassic age Kin Kin Beds (blue-green shading), which are
described as “commonly cleaved and commonly kinked mudstone…”. The Australian Stratigraphic Units
Database describes the Kin Kin Beds as “arenite, argillite and phyllite.”




                                                                          Indicative Site Location




Text Figure 9: Extract from Gympie Surface Geology Map

4.4           Subsurface Conditions
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. Subsurface conditions encountered across the proposed new development area (i.e. test pits TP1,
TP3 and TP4) were consistent summarised as follows:
            Topsoil/Fill – comprising friable silty clay of medium plasticity, with varying organic, gravel and
             cobble content to depths between 0.3 m and 0.6 m BGL; then
            Residual Soils – very stiff to hard, silty clay of high plasticity and clayey silt of high liquid limit to
             depths between 1 m and 1.2 m BGL; underlain by
            Extremely Weathered (XW) Materials/Weathered Phyllite – hard, silty gravelly clay of medium
             plasticity and very low strength phyllite, rapidly grading to low strength (or stronger), with toothed
             bucket refusal or very slow digging achieved at depths between 1.7 m and 2.3 m BGL.

Test pit TP2 was excavated on the proposed driveway alignment, downslope of the rock fill embankment
(inferred remediated landslide) and encountered a friable topsoil layer to 0.3 m BGL, then a stiff to very stiff,
silty gravelly clay of high plasticity, being colluvium 3/landslide debris, with fissured and slickensided 4
surfaces to 3 m BGL (limit reach of the machine). Based on our site observations this area appeared to
have been impacted by previous landslide movements.

Text Figure 10 overleaf illustrates typical subsurface conditions encountered during the investigation.


2
    State of Queensland, Dept. of Natural Resources, Mines and Energy, Gympie Surface Geology, Sheet 9445, 2018
3
    A mixture of soil and/or rock (of various sizes) deposited over geological time due to movement induced by gravitational force
4
    A smooth, often striated surface produced by movement along a plane of weakness within soil or rock


22 May 2023
Report No. 23099-001-Rev0                                             7