Geotechnical Report

                                   PROPOSED UNIT DEVELOPMENT
                                   31 BOTTLEBRUSH AVENUE, NOOSA HEADS

Table 1: Summary of Subsurface Conditions
                                      Very Loose to Loose       Medium Dense              Dense Sand
  BH       Topsoil          Fill
                                        Silty Sand/Sand             Sand
  No.
                                           Depth in metres below ground
  BH1        NE        0.0 - 0.6           0.6 - 1.2                1.2 - 3.6            3.6 – 3.8 (TD)
  BH2      0 - 0.05         NE             0.05 – 1.4               1.4 – 4.3            4.3 – 5.4 (TD)
 Notes:
    1) TD – denotes borehole ‘Termination Depth’ of DCP testing.

More detailed descriptions of the subsurface conditions are provided in the borehole reports attached in
Appendix A.

4.5      Groundwater
No signs of groundwater seepage (‘springs’) were observed during our walk-over. Groundwater was not
encountered in the boreholes at the time of investigation.

Groundwater conditions are expected to be reflective of prevailing weather conditions and seepage may
occur at shallower depths, and at locations not previously observed, particularly following periods of
prolonged or heavy rainfall.

4.6      Surface Drainage
Surface drainage would be expected to follow natural surface contours to the south west with flows directed
into the kerbside drainage on Bottlebrush Avenue, thus draining into the road side drainage system. Run-off
would likely currently be of relatively low volume due to the sandy nature of the exposed soils at the site,
and is currently interrupted by terracing, retaining walls and landscaping features.

It is acknowledged that a catchment for the site exists to the north east, extending to the crest of the dune
(Ref. Section 4.2 above). However, no significant surface run-off features were noted during our
assessment (e.g. deep rilling or scour/wash out scars). This indicates that significant overland flow is
generally absent during rainfall events.

Recommendations to improve surface drainage as part of the development works are provided in Section
6.5.

4.7      Existing Structures
The exiting residence comprised a two storey masonry brick structure sited on a levelled building pad with
concrete block walls supporting cut and fill in various locations around the perimeter ranging in height from
about 1 m up to a maximum of 3 m high. The structures did not exhibit any signs of distress that could be
attributed to slope instability however the retaining wall at the front of the stie alongside the driveway was
cracked. The distress to this wall appeared likely to be a result of subsidence due to consolidation
settlement of the loose sand (both fill and upper natural foundation materials) under the wall and
embankment loading.




17 December 2020
Report No. 20370-001-Rev0                               7