Attachment C - Geotechnical investigation

                                                                                                   51 640 311 842
                                                                                                       CONTACT
                                                                                      [email protected]
                                                                                               arcosgroup.com.au
                                                                                                         OFFICES
                                                                           Sunshine Coast | Brisbane | Gold Coast




5.0 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.


An experienced geotechnical engineer undertook the walkover assessment on 05 Feb 2021.
As part of the walkover assessment, 'spot' measures were taken of the slope angles and
observations pertaining the any obvious previous slope instability on the allotment and
immediately adjoining areas that were readily accessible at the time of the inspection was
undertaken. The surface levels on the site fall away to the south to south east at varying grades
up to 33°. Signs of disturbed ground, tension cracks or hummocks were noted during the
walkover assessment. A variety of vegetation ranging from small shrubs to mature trees were
observed. Some of the mature trees were observed to have misshapen and curved trunks.
Misshapen or curved trunks are usually good indicators for previous slope instability.. The
photographs attached to this report show the conditions of the site at the time of the
inspection and assessment undertaken.

6.0 AGS Assessment
Landslides are caused where a soil or rock mass has a decrease in strength, usually attributed
to groundwater, resulting in the material not being able to maintain its own self-weight
resulting in a slope failure.


The Australian Geomechanics Society (AGS) developed a set of tools and procedures for
assessing the stability of a slope. The tools and procedures presented with the AGS
documentation form the basis of the assessment undertaken herein and their documentation
is attached for reference.


The guidelines also identify that the regulator typically sets the standard for levels of tolerable
risk. AGS defines tolerable risk as “risks within a range that society can live with so as to secure
certain benefits. It is a range of risk regarded as non-negligible and needing to be kept under
review and reduced further if practicable”.

The guides suggest that areas of moderate or greater risk should not be developed unless a
rigorous remediation plan be implemented to reduce the area to a level of Acceptable Risk.
AGS defines acceptable risk as “risk which everyone affected is prepared to accept. Action to further
reduce such risk is usually not required unless reasonably practicable measures are available at low
cost in terms of money, time and effort.”.

AGS suggest that regulators generally accept risk levels of “low” or lower as a level of
acceptable risk.


09 Feb 2021                                                           Proposed Residential Dwelling