271117 Techtonic GeoTech Cooroy Mtn Rd

Mr Ken Freeman                                                                                           17385-001-Rev0
                                                                                                       27 November 2017

 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 (Refer Section 3), and subject to the implementation of
recommendations given below, it is our opinion that there is a Low (L) Risk of global slope instability affecting
the proposed development. Regulators (NSC) normally require that a Very Low or Low Risk of landslide
affecting the property must be demonstrated to enable development approval. Summarised in Table 3 is our
qualitative assessment of landslide risk for the development. A summary of qualitative terminology for use in
assessing risk to property is attached (taken from AGS 2007).
 Table 3: Qualitative stability risk assessment

                                                              Assessed
 Hazard                            Likelihood   Consequence
                                                                Risk
                                                                         Comments


                                                                         The natural soils on site are generally at least
                                                                         stiff/medium dense material, underlain by rock at
                                                                         relatively shallow depth (<1.3 m BGL), no
                                                                         groundwater was encountered in the previous
 1: Shallow landslide through                                            Bowler investigation or the recent test pits.
natural soils above foundation      Unlikely      Medium          Low    Therefore, it is considered Unlikely that a shallow
depth                                                                    landslip would develop. However, the potential
                                                                         impact from instability is assessed as Medium,. The
                                                                         resultant risk would therefore be Low as per AGS
                                                                         2007, subject to the implementation of
                                                                         recommendations in Section 5.




                                                                         No signs of existing instability in the fill embankment
                                                                         were observed, and future fill is to be supported by
                                                                         engineer designed retaining walls, therefore it is
 2: Shallow failure through fill                                         assessed that the likelihood of shallow failure in the
material in terrace on the          Unlikely       Minor          Low    fill is Unlikely. No buildings are planned in the filled
northern side of house                                                   area, therefore the consequence of the failure would
                                                                         be Minor. The resultant risk is Low as per AGS
                                                                         2007, subject to the implementation of
                                                                         recommendations in Section 5.




                                                                         The likelihood of a deep failure through the
                                                                         weathered rock is assessed as Rare due to the
                                                                         strength of the rock, apparent absence of
 3: Deep seated landslide                                                groundwater, and no evidence of existing instability
through weathered rock below         Rare          Major          Low    in the vicinity of the works. Although the
foundations                                                              consequence of such a failure would be Major, the
                                                                         resultant risk is Low as per AGS 2007, subject to
                                                                         the implementation of recommendations in Section
                                                                         5.




The potential impacts on slope stability of the development components (including during earthworks) have
been assessed, and the measures recommended below in Section 5 have been designed to mitigate those
impacts.




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