geotech report · 132003.220660.5

5. Instability of temporary excavation batters.
6. Instability of proposed retaining walls and shoring.

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 geotechnical 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
The following Table A summarises our assessment of risk to property during and following construction of
the proposed alterations and additions and indicates the assessed risk to property is “Low” and “Very Low”
which in accordance with the criteria given in Reference 1 is considered to be “Acceptable”.

Risk to Life
We have not completed a comprehensive assessment of risk to life. However, based on the indicative
probabilities associated with the assessed likelihood of instability and assuming typical temporal,
vulnerability, evacuation and spatial factors for this type of site, we consider that the levels of risk to life
under existing conditions, during and following construction to be “Acceptable” in relation to the criteria
given in Reference 1, i.e. less than 1x10-6 and assumes the recommendation outlined in Section 6 below are
referred to.



5.2.3 Additional Comments
It must be recognised that, due to the many complex factors that can affect a site, the subjective nature of a
risk analysis, and the imprecise nature of the science of geotechnical engineering, the risk of instability for a
site cannot be completed removed. It is, however, essential that risk be reduced to at least that which could
be reasonably anticipated by the community in everyday life and that landowners be made aware of
reasonable and practical measures available to reduce risk as far as possible. Hence, risk cannot be completed
removed, only reduced, as removing risk is not currently scientifically achievable.

In preparing our recommendations given below we have assumed that no activities on surrounding land
which may affect the risk on the subject site would be carried out. We have further assumed that all Council
owned buried serviced and other buried services within and neighbouring the site are, and will be regularly
maintained to remain, in good condition.




32032URrpt                                          10