Attachment 3 - Revised Slope Stability Assessment

Brett Hage                                                                                      22328-001-Rev1
                                                                                              17 November 2022

3.0     ASSESSMENT OF LAND STABILITY
3.1   Existing Conditions
In the proposed Lot 2 area, a High landslide hazard has been allotted in NC landslide hazard overlay
mapping for much of the main drainage line running west-east through the overall lot; and its associated
flanks. The area currently proposed for building on proposed Lot 2 generally has been mapped as having a
Low (no shading) to Moderate hazard rating (Ref. extract in Text Figure 8).




                                                                                 Overall existing Lot boundary




Text Figure 8: 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largely based on ground slope, and is superseded by this site specific assessment.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, the existing structures on site were in good condition,
with no significant erosion or slumping observed over the existing fill earthworks pad, or other minor
earthworks features (e.g. horticultural terraces). In addition, the natural subsurface conditions were
favourable with stiff to very stiff soils present from near surface, and weathered meta-mudstone rock
logged at relatively shallow depth in both the boreholes; and XW material exposed in earthworks cuttings.

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 2 on the
following page and the Qualitative Terminology for Use in Assessing Risk to Property is also attached.




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