Attachment 5 - Geotechnical Report · MCU18/0015

J000635-002-R-Rev1                                                                                   November 2018




                                                                                            Approximate site location




                                                                      Qpd2



Image 1: Site geology as presented in the Gympie Special Geology Map1.
5.2       Ground Conditions
The subsurface conditions in the boreholes across proposed Lots 1 to 3 generally comprised:

          Topsoil (sand) between 0.2 m and 0.3 m thick, overlying
          Aeolian/Alluvial soil comprising about 1 m to 2 m of loose sand.
Stiff sandy clay (residual soil) was observed in borehole BH2 at 3.3 m depth. Very stiff sandy clay
(colluvium/residual soil) was also encountered at 1.4 m BGL in test pit TP10 in the 2003 investigation on
proposed Lot 3.
Inferred very loose or loose sands were typically encountered along the seismic lines to depths of about 1 m
to 2 m, up to about 3 m in some parts. The seismic testing indicates that soil density generally increases with
depth. Shear-wave velocities corresponding with weathered rock were encountered from about 12 m BGL
along Lines 1 and 2 (proposed Lot 1), and about 17 m depth at the higher elevation at Line 3 (proposed Lot
2).
Groundwater seepage was not encountered in any of the boreholes or test pits across proposed lots 1 to 3

6.0        GEOTECHNICAL DISCUSSION & RECOMMENDATIONS
6.1       Earthworks
      6.1.1    Site preparation & trafficability
Site preparation in building and pavement areas should include the following:

     Strip the surface of vegetation, organic matter, organic rich soils (topsoils), severely root affected soils,
      and uncontrolled fill. Topsoil was generally encountered up to about 0.3 m, however it is anticipated that
      grubbing of tree stumps and tree roots will require localised stripping to greater depths.

     ‘Proof roll’ the stripped surface by several passes of a minimum 10 tonne smooth-drum roller (without
      vibration, to reduce slope stability impacts) to identify loose or soft areas. Proof rolling in areas of cut
      may be deferred until after bulk excavation is completed.
     Depressions formed during removal of large tree root systems should be backfilled with select fill and
      compacted in layers in accordance with Section 6.1.3.


                                                          5