Approved Plan - EXE21-0015

Mr Dean Frith                                                                                           21182-001-Rev0
                                                                                                           28 May 2021

3.0     ASSESSMENT OF LAND STABILITY
3.1   Existing Conditions
The proposed shed site has generally been mapped by NC as presenting a Moderate landslide hazard area
(pale yellow brown shading). An extract of the NC mapping is given below in Text Figure 13.




                                              Proposed shed site




Text Figure 13: Extract from NC Landslide Hazard Mapping

It should be noted that the NC map is a broad-scale indication of the potential landslide susceptibility only,
largely based on ground slope, and is superseded by this site specific assessment.

The site does not exhibit any indicators of global, natural slope instability. No landslide back scarps or
areas of natural ‘hummocky’ ground were observed at or near the proposed shed site, however minor
erosion and slumping was observed in part of the fill batter which is likely due to existing surface drainage
conditions and uncontrolled fill. In addition, the subsurface conditions appeared favourable with stiff
residual soils and weathered rock encountered at relatively shallow depths within the Ground Drill
boreholes.

3.2   Qualitative Stability Assessment
The risk assessment for this project has been carried out following AGS 2007 Practice Note Guidelines for
Landslide Risk Management. Relative levels of risk and their implications are given in Table 1 below and the
document Qualitative Terminology for Use in Assessing Risk to Property, which is also attached.
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 .




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