Geotechnical Report

5.2   Risk Assessment

5.2.1 Potential Geotechnical Hazards
Based on our site observations, assessment of existing conditions provided above, and the form of the
proposed alterations and additions, we consider that the potential geotechnical hazards for the site are as
follows:
1. Deep seated slope instability.
2. Instability of existing retaining walls.
3. Instability of temporary excavation batters.
4. Instability of proposed pool walls.

It is important to be mindful that slope instability can occur at any time and it would be difficult or impossible
to predict when the identified potential hazards will occur. Also, we cannot predict when an extreme or
unusual event may occur (such as an earthquake, or 1 in 100 year rainfall event, etc.) and what impact it
would have on the stability of the identified potential hazards described above.



5.2.2 Risk Analysis
Our geotechnical assessment of the risk of instability is based on the methodology proposed by Australian
Geomechanics Society (2007c) ‘Practice Note Guidelines for Landslide Risk Management’ (Reference 1) and
the relevant site features described above.

Risk To Property
Table A below summarises our qualitative assessment of each potential landslide hazard and of the
consequences to property should the landslide hazard occur during and following construction of the
proposed alterations and additions. Based on the above, the qualitative risks to property have been
determined.

  TABLE A: SUMMARY OF RISK ASSESSMENT TO PROPERTY DURING AND FOLLOWING CONSTRUCTION
 Potential Landslide            1.                       2.                     3.                   4.
 hazard                 Deep seated slope     Instability of existing      Instability of       Instability of
                           instability1          retaining walls2           temporary          proposed pool
                                                                        excavation batters3        walls2
 Assessed Likelihood     Barely Credible             Rare                      Rare                 Rare
 Assessed                    Major                  Medium                    Minor               Medium
 Consequences
 Risk                       Very Low                     Low                 Very Low               Low
Notes
   1. Due to slope angles deep seated instability not expected to occur.
   2. Existing retaining walls assumed to be engineer designed and new pool walls designed in accordance
      with the advice presented in Section 6 of this report.
   3. Assuming temporary batters are formed in accordance with the advice presented in Section 6 of this
      report.


36409UR                                              8