Slope Stability Report 26-5-2019 OPW19-0193

TRUBUILT
SLOPE RISK ASSESSMENT REPORT



      •   Wedge failure – failure of rock along two or more natural defects such as foliation and/or joints;
      •   Shallow slumping – shallow rotational failure in soil and soil like materials;
      •   Translational sliding – sliding of soil materials over shallow underlying rock;
      •   Creep flow – slow movement of soil over underlying materials, these slips can exhibit features of both
          shallow slumping and translational sliding.

Table 2 outlines the risk assessment for the various mechanisms given above:

Table 2 - Slope risk assessment for various mechanisms
      Potential                                       Assessed
                        Likelihood   Consequence                                       Comments
       Hazard                                           Risk
                                                                   A likelihood of RARE has been adopted for the site
                                                                   since there is no evidence of major slope failures in
                                                                   the surrounding landscape. The likely consequence
  Global failure        RARE          MAJOR             LOW        of a failure would result in significant damage to the
                                                                   proposed structure. Therefore, the assessed risk is
                                                                   LOW.
                                                                   A likelihood of POSSIBLE has been adopted for the
                                                                   site since there are proposed cuts into rock and this
                                                                   manner of failure is common within the Kin Kin Beds
  Wedge failure        POSSIBLE       MINOR         MODERATE       elsewhere. The likely consequence of a failure would
                                                                   result in minor damage to the cut batter slope that
                                                                   would require the removal of spoil. Therefore, the
                                                                   assessed risk is MODERATE
                                                                   A likelihood of LIKELY has been adopted for the site
                                                                   since fill material will comprise soil with sericite and
       Shallow
      slumping
                        LIKELY        MINOR         MODERATE       crushed phyllite material. The likely consequence of
                                                                   a failure would result in partial loss of fill batter
                                                                   slopes. Therefore, the assessed risk is MODERATE
                                                                   A likelihood of UNLIKELY has been adopted for the
                                                                   site since the cut batter slope will be occurring at the
   Translational                                                   upper, flatter sections of the site. The likely
      sliding
                       UNLIKELY       MINOR             LOW        consequence of a failure would result in minor
                                                                   deposition of material onto the cut platform.
                                                                   Therefore, the assessed risk is LOW
                                                                   A likelihood of LIKELY has been adopted for the site
                                                                   since the mechanism is present in multiple locations
                                                                   on surrounding slopes. The likely consequence of a
    Creep flow          LIKELY       MEDIUM             HIGH       failure would result in damage to part of the site
                                                                   which may require stabilisation works. Therefore,
                                                                   the assessed risk is HIGH


Further information on landslides and the risk assessment process can be found in Australian Geoguides LR1,
LR2, LR3, LR4 and LR7.


3.4         Slope Risk Mitigation

The sections below give recommendations to reduce the risk associated with the hazards identified above.




LEONTAKIANAKOS-R-001                                Page 9                                                     26 May 2019