Geotech

                               PROPOSED UNIT DEVELOPMENT
                               27 BOTTLEBRUSH AVENUE, NOOSA HEADS

4.4         Subsurface Conditions
Detailed descriptions of the subsurface conditions encountered in the boreholes are provided in the
borehole reports attached in Appendix A, along with definition sheets which describe terms and
abbreviations used on the reports. Subsurface conditions encountered in the boreholes are summarised as
follows:

          Fill – comprising very loose to loose sandy gravel and silty sand to depths between 0.6 m and
           1.3 m BGL (boreholes BH1 and BH2 only); then or from the ground surface
          Natural Sands – comprising silty materials to about 1 m to 1.2 m BGL, then poorly graded sands
           initially, being loose to medium dense to depths between 2.2 m and 5.2 m BGL, then becoming
           medium dense to the borehole termination depths.

DCP testing was continued beneath the borehole termination depths, which indicates that the sands
become dense (or denser) at depths between 4.2 m and 6.3 m BGL.

Table 1 below, summarises the subsurface profile in each borehole.
Table 1: Summary of Subsurface Profiles




                                                          T
                                               Very Loose/          Medium Dense         Dense (or
  Borehole No.                Fill
                                               Loose Sands             Sands           denser) Sands

          BH1               0 – 1.3              1.3 – 5.2*            5.2 – 6.0TD       6.2* – 6.6DCP
                            AF
          BH2               0 – 0.6               0.6 – 2.3            2.3 – 3.0TD       4.1* – 4.7DCP


          BH3                 NE                   0 – 2.2             2.2 – 3.0TD       4.3* – 4.7DCP

Notes: 1.         Depths noted in m BGL at time of investigation (27 July 2021)
       2.         NE denotes not encountered
       3.         TD denotes borehole terminated at target depth
          R
       4.         * inferred from DCP testing
       5.         DCP denotes DCP termination depth



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.
D

Groundwater conditions are expected to be reflective of prevailing weather conditions and seepage may
develop, 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 towards
Bottlebrush Avenue, thus draining into the roadside drainage system. It is noted that the site has relatively
large catchment; however, most runoff from upslope of the property is anticipated to be intercepted by the
existing stormwater infrastructure from the neighbouring structures and streets.

Given the sandy nature of the site, rainfall would normally be anticipated to infiltrate the ground surface.
However, as the proposed development will occupy a large part of the block, significant run-off from hard
surfaces will occur. Nevertheless, where directed into swales rather than pipes, such run-off would be
expected to infiltrate into the natural sands relatively rapidly. 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.

10 November 2021
Report No. 21286-001-Rev0                                    5