Slope Stability Report - 22072-001-Rev0

H.M de Groot                                                                                                 22072-001-Rev0
                                                                                                              21 March 2022

 Table 1: Stability Risk Levels

 Risk Level             Example Implications(1)
                        Unacceptable without treatment. Extensive detailed investigation and research, planning
        Very High
 VH                     and implementation of treatment options essential to reduce risk to Low; may be too
        Risk
                        expensive and not practical. Work likely to cost more than value of property.
                        Unacceptable without treatment. Detailed investigation, planning and implementation of
 H     High Risk        treatment options required to reduce risk to Low. Work would cost a substantial sum in
                        relation to the value of the property.
                        May be tolerated in certain circumstances (subject to regulators’ approval) but requires
        Moderate
 M                      investigation, planning and implementation of treatment options to reduce risk to Low.
        Risk
                        Treatment options to reduce to Low risk should be implemented as soon as practicable.
                        Usually acceptable to regulators. Where treatment has been required to reduce the risk
 L     Low Risk
                        to this level, ongoing maintenance required.
        Very Low
 VL                     Acceptable. Manage by normal slope maintenance procedures.
        Risk
 Note: (1) The implications for a particular situation are to be determined by all parties to the risk assessment and may
 depend on the nature of the property at risk; these are only given as a general guide.

Considering the existing site conditions (Ref. Section 2), and subject to the implementation of
recommendations given in Section 4, it is assessed that there would be a Low (L) Risk of global slope
instability affecting the proposed shed. Regulators (NC) normally require that a Very Low or Low Risk of
landslide affecting the property must be demonstrated to enable development approval. Summarised in
Table 2 is our qualitative assessment of landslide risk for the site. A summary of qualitative terminology for
use in assessing risk to property is attached (taken from AGS 2007).
 Table 2: Details of Qualitative Risk Assessment for Property (AGS 2007)

                                               Assessed
 Hazard               Likelihood Consequence
                                                 Risk     Comments

                                                          The likelihood of a failure through the existing cut batters or fill
                                                          embankments adjacent to the building platform is considered Unlikely,
 1: Failure through
                                                          given the favourable topography, lack of groundwater, lack of evidence
the existing cut
                       Unlikely   Medium         Low      of existing natural instability and subject to implementation of the
batters or fill
                                                          recommendations specified in Section 4. The consequence of such a
embankments
                                                          failure would remain Medium, with the resultant risk being Low as per
                                                          AGS 2007.


 2: Deep failure                                          The likelihood of a deep failure through the weathered rock is assessed
through weathered                                         as Rare due to the strength of such materials, and no evidence of deep-
                        Rare       Major         Low
rock below the                                            seated instability in the area. Although the consequence of such a failure
foundation depth                                          could be Major, the resultant risk would be Low as per AGS 2007.



The potential impacts on slope stability of the development components have been assessed, and the
measures recommended below in Section 4 have been designed to mitigate those impacts.




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