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

                              PROPOSED SUBDIVISION
                              41 TALLOWWOOD PLACE, BLACK MOUNTAIN

4.9       Buildings and Other Structures
Although not covered by this slope stability assessment, the existing residence in the central part of the site
comprised a single storey structure elevated on posts, with a formalised undercroft area. Based on an
external assessment the residence appeared to be in good structural condition, considering age, with no
obvious signs of distress (e.g. tilting, cracking, misalignment etc.) which would indicate global slope
instability.

As mentioned previously, timber sleeper and boulder walls up to about 1.5 m high supported previous
earthworks undertaken around the residence. Some of the timber sleeper walls were noted to be
tilting/leaning, with large voids present within the boulder walls. Horizontal separations up to about 30 mm
were present between a concrete pathway and the north-wester corner of the residence, with parts of the
slab undermined. The distress observed in these structures appeared to be related to age, poor
construction, and adverse drainage conditions rather than global slope instability.


5.0       SLOPE STABILITY ASSESSMENT

5.1       Existing Conditions
The Noosa Planning Scheme 2020 includes a landslide hazard overlay map (Ref. extract in Text Figure 11)
which indicates that most of the site, including the proposed new development area has a Moderate to High
Landslide Hazard.




                Proposed Development Area

                                                             Subject Site




Text Figure 11: Extract from NSC landslide hazard overlay mapping

It should be noted that the NC map is a broad-scale indication of the potential landslide susceptibility only
and is superseded by this site-specific assessment. The recommended building area as defined in
Section 6.1 did not exhibit any indicators of global, natural slope instability, with competent natural
materials and weathered rock encountered at shallow depths in the test pits excavated across the area.
Building exclusions and setbacks from areas of identified instability are recommended.

Surface cracks up to about 20 mm wide were observed across the proposed new building area which
appeared to be related to soil shrinkage due to drying, rather than slope instability.




22 May 2023
Report No. 23099-001-Rev0                                9