Approved Plan - OPW21-0279

Anthony Kelly                                                                                 21354-001-Rev0
                                                                                           17 September 2021

3.0     ASSESSMENT OF LAND STABILITY
3.1   Existing Conditions
In the area of the earthworks undertaken at the site, the NC Landslide Hazard Overlay has assigned a risk
rating of Moderate to High. An extract of the NC mapping is given below in Text Figure 11.




                                                                                           Lot boundary




Text Figure 11: Extract from NC Landslide Hazard Overlay 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 (e.g. a higher risk has been allotted east of the site area, coincident with
the natural gully feature, with slightly steeper sideslopes to the adjacent ground), and is superseded by
site specific assessment works.

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 earthworks, with shallow batter slopes
and drainage already in place, as well as erosion control measures (revegetation). In addition, the
subsurface conditions appeared favourable with residual soils of the Kin Kin beds exposed consistently in
cut slopes observed around the site area.

There was also a significant offset of at least 10 m to any existing structures on the site (e.g. shed,
residence etc.). Downslope of the earthworks, no structures were present, and the subject site extended
well to the east and west. To the north, an offset of over 20 m was present between the toe of the fill
pushed out as part of the northern cleared area, and the nearest property boundary.

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.




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