RFI - Att 1 - Slope Stablility Assessement

eastern and southern parts of the site using a 4WD utility mounted solid flight auger rig, on similar
ground to the dam areas, to depths of 2 m below ground level (BGL).
A walk-over survey was conducted to make an appraisal of the general condition of the existing and
proposed dam areas regarding topography, drainage, vegetation, geology, erosion, condition of existing
structures and slope stability. The walk-over was carried out by an experienced geotechnical engineer
from Tectonic on 3 March 2026. Results of the desk-top study and walk-over survey are included in
Section 2 below.

1.3       Qualifications of Responsible Engineer
This report has been prepared by Ashley Davey, an RPEQ with more than 30 years’ experience in
geotechnical engineering, including numerous slope stability projects.


2.        Description of Existing Conditions
2.1       Geology
A published geological map 1 indicates that the site is underlain by residual strata derived from the
Triassic age Kin Kin Beds. The formation typically comprises strongly cleaved and commonly kinked
mudstone with thin siltstone laminae; minor volcanilithic sandstone (denoted Rk in Text Figure 4).




                                       Subject Site




                           Text Figure 4: Extract from Gympie Surface Geology map

No exposures of ‘bedrock’ were observed near the dams, however weathered mudstone was observed at
about 1 m deep below the ground surface in shallow access track cuttings on the ridge areas in the
southern parts of the site (Ref. Text Figure 5 overleaf). Residual clay soil derived from weathering of
mudstone was observed in exposures around the existing Dams 01 to 04 (Ref. Text Figure 6 overleaf).




1 State of Queensland, Dept. of Natural Resources, Mines and Energy, Gympie Surface Geology, Sheet 9544, 2018




18 March 2026
25029-002-Rev0                                                                                                  4 of 12