Slope Stability Report (rec. 16.04.25) · MCU25/0042

                                                                                                        ABN 51 640 311 842
                                                                                                        arcosgroup.com.au
                                                                                       Sunshine Coast | Brisbane | Gold Coast




1         INTRODUCTION
Arcos Unit Group Pty Ltd (Arcos Group) was commissioned to undertake a geotechnical investigation for the project
at the location described on the title page of this report.
This report outlines the results of the investigation, laboratory testing, analysis, and interpretive reporting on the
following items:
 Review of the existing slope stability hazards, their attributed risks and impacts of the proposed development in
  alignment with the practices set out within the Australian Geomechanics Society guidelines; and,
 Provide recommendations from a geotechnical context that will avoid or reduce any potential instability.
This report must be kept in entirety. The use of this document is exclusively undertaken in accordance with our terms
and conditions.

2         REGIONAL GEOLOGY
The site is in an area underlain by Pleistocene aged parabolic sand dunes, which typically comprises “quartz sand”.

3         EXISTING STABILITY RISK
Local authorities prepare mapping tools to aid in assessing potential slope stability requirements. The mapping tools
are a “high level” approach where the site specific investigations are specific to a particular site/allotment. It is
important to note that where a site specific investigation and slope stability assessment are undertaken, they take
precedence.
Reference to the available overlays for the area show the site has been initially mapped as “Moderate” in terms of
landslide hazard.

4         GEOTECHNICAL INVESTIGATION
A soil test has recently been undertaken by Australian Soil Investigations (ASI). The soil test comprised the drilling
of two bores to between 2 m and 3 m depth using hand-held auger equipment. In summary, the subsurface conditions
encountered in the bores generally comprised loose to medium dense silty sand (which is consistent with the
published geology). No groundwater seepage was encountered in the bores; however, it should be noted that
groundwater is transient and can fluctuate with seasonal changes and human influences (such as broken
infrastructure). A copy of the ASI report is attached.

5         WALKOVER ASSESSMENT
Geotechnical comments are based on the factual findings of the investigation, best practice, local experience,
published correlations; however, are fundamentally founded in opinion and this should be considered.
A site walkover assessment was undertaken by a Geotechnical Engineer on 26 March 2025. The site is located on
the western flank of a hill within the Yunaman Bushland Reserve. The site is occupied by an existing brick veneer
dwelling and an empty in-ground pool at the rear. These structures appeared to be stable, and no visible signs of
distress (associated with downhill slope movements) were observed. Topographically, the site is initially relatively flat
and level from the road but then gently slopes down towards the western boundary. Slopes angles are moderate and
range between 5° and 10°. No obvious signs of disturbed ground, tension cracks or hummocks were noted at the
site and surrounding area during the walkover assessment. A variety of vegetation ranging from small shrubs to
mature trees were observed. The mature trees at the site were all observed to be typically vertical with no misshapen
or curved trunks. Misshapen or curved trunks are usually good indicators for previous slope instability.



Sunshine Coast | Brisbane | Gold Coast