Attachment C - Soil Survey Report · MCU18/0013

Project No. 1-20119                                                                                                        Page | 12
March, 2018
Ref: 1-20119, 2018-03-02, BR VER 2
Sam Hopper – Slope Stability Assessment and Geotechnical Report - Proposed Residence, 24 Arakon Crescent, Sunshine Beach




However, once suitable permanent retaining structures are in place, the hazard rating would
drop to Low (lower end) which translates to a Likelihood Descriptor of Rare.

Note: The above assumes that all retaining structures on the site are designed by a
suitably qualified RPEQ and constructed in accordance with their design.

               5.4.5   Hazard C - Scour of Exposed Surfaces

As noted above, the methods as adopted for Hazards A and B do not have a corresponding
method for the analysis of scour (Hazard C). The following comments will allow the hazard to be
assessed:-

              The proposed development is likely to require the clearing and exposure of soil over
               essentially the entire site (slope angles generally of 5º to 30º).
              The exposed surfaces would most likely be fill and sandy soils.
              Experience with these types of materials would suggest that the exposed material would
               scour easily if left exposed and water is allowed to run over the slopes.

Based on the above comments and observations on site, the likelihood rating for the scour of
exposed surfaces would be assessed as being Moderate to High which translates to a
Likelihood Descriptor of Unlikely to Likely.

However, if soils are protected from scour as would be expected to be required as part of the
development during and following construction, then the rating would reduce to Very Low or
Low which translates to a Likelihood Descriptor of Barely Credible to Rare.

    5.5 Consequence Analysis

               5.5.1   General

As part of the assessment of the risk of slope instability, the analysis of the consequence of any
failure must also be considered.

This analysis is based on the effect on the following for each type of hazard:-

          i)      Consequence to Property (proposed dwelling)
         ii)      Consequence to Persons within and around the proposed dwelling

               5.5.2   Site Factors

The development consists of the construction of a new residence on the site. The following will
be used to assume consequence:-

              A residence will be constructed with basement level formed by cuts into the existing
               slope.
              Based on the provided drawings, temporary cuts of up to approx. 4.0m to 5.0m will be
               required, as tiered cuts for the basement and first floor near the middle of the site
               (including near boundaries).
              The cuts will be supported initially by temporary engineer designed and certified
               retaining structures during construction and then with permanent retaining structures as
               part of the residence.