Reference Document - MCU26 0012 & OPW26 0034 (As Published)

Considering the existing site conditions (Ref. Section 2), and subject to the implementation of
recommendations given below, it is assessed that there should be a Low Risk of global slope instability
affecting the proposed shed. Regulators (NC) normally require that a Very Low or Low Risk of landslide
affecting the property must be demonstrated to enable development approval.
Summarised in Table 2 is our qualitative assessment of landslide risk for the extensions. A summary of
qualitative terminology for use in assessing risk to property is attached (taken from AGS 2007).

Table 2: Details of Qualitative Risk Assessment for Property (AGS 2007)
                                                            Assessed
           Hazard                Likelihood   Consequence              Comments
                                                              Risk

                                                                       The likelihood of a landslide within the fill or
                                                                       natural soil materials affecting the proposed
                                                                       structures is considered Unlikely, given that no
                                                                       evidence of such slope movement was noted
     Landslide extending
                                                                       on the site or in the immediate vicinity,
    through proposed fill
                                                                       moderate ground slopes (even on the
   and/or natural residual        Unlikely      Medium        Low
                                                                       spur/drainage line flanks, being ≤10°) apparent
  soils to cause damage to
                                                                       lack of groundwater seepage, and that there
  the proposed structures
                                                                       was an opportunity to create favourable
                                                                       surface water drainage. The consequence of
                                                                       such instability would be Medium, with the
                                                                       resultant risk being Low as per AGS 2007.

                                                                       Given the strength of the deeper residual soils,
                                                                       limited extent of deeper earthworks filling, and
                                                                       absence of indicators of slope instability, it is
  Deeper landslide (>2 m)                                              considered Rare that a deeper landslide would
     through very stiff (or                                            occur extending below the proposed
                                   Rare          Major        Low
 stiffer) residual soils below                                         foundation depths, subject to implementation
    the foundation depth                                               of the recommendations in Section 4. Even for
                                                                       a Major consequence from such instability
                                                                       there would be a resultant Low risk as per AGS
                                                                       2007.



4.        Recommendations
General recommendations to help maintain the stability of the site are given in the document Some
Guidelines for Hillside Construction, which is attached.

4.1       Extent of Development
The location and nature of the proposed residence, stables and arena (including earthworks) as
described in Section 1.1 shall not be altered unless assessed and approved by Tectonic.

4.2       Earthworks
Future earthworks in building areas are expected to be most significant for the proposed residence,
extending to about 3 m maximum depth of cut and up to about 1.9 m height of fill. Deeper isolated
excavations may be required for footings and underground services.
Any loose or soft soils, saturated silts, organic rich topsoil and severely root affected soils, must be
removed from the proposed construction areas. Following site stripping subgrades should be proof
rolled using a minimum 4 tonne roller in the presence of a civil/geotechnical RPEQ to identify any ‘soft


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