Geotech Report - Initial Findings

Essence of Peregian
215-219 David Low Way, Peregian Beach
Project No. 007-160A,
27 April 2010




       SECTION 4 - INVESTIGATION RESULTS
       4.1       Reports

       The subsurface conditions encountered at the bore locations are summarised on Bore Report sheets
       included in Appendix A, using classification and descriptive terms defined in accompanying notes.

       4.2       Subsurface Conditions

       For details of the strata encountered at the bore locations the Bore Report sheets should be consulted.
       However, in very broad summary, the stratigraphy encountered in the bores generally comprised a
       discontinuous surface layer of fill and/or possible fill to 0.2m to 0.8m depth in Bores 1 to 4, 9, 10 and 12.
       Underlying the fill and/or possible fill, and from ground surface levels in the remaining bores, very loose to
       loose sand and silty sand was encountered that was underlain in turn by medium dense sand below 1.2m to
       3.9m depth. In all bores except Bore 11, the medium dense sand was underlain by a variable thickness
       layer of dense, weakly cemented indurated sand. In Bores 1 and 2 only, the fill was underlain by natural,
       dark grey-brown silty clays then silty sands that were indurated below 2.0m depth. In Bores 7, 8 and 9 the
       indurated sand layer was underlain by medium dense sand. The bores were discontinued in sand and
       indurated sand at approximately 7.3m to 8m depth.

       It should be noted that the medium dense sands underlying the indurated sands represents a ‘strength
       inversion’ (i.e. lower strength material underlying higher strength material). A strength inversion was also
       encountered in Bore 11 where loose sand was encountered below 6.2m depth underlying medium dense
       sand.

       4.3       Groundwater

       Free groundwater was encountered during auger drilling of the bores at the depths/levels given in Table 2. It
       should be noted that groundwater levels would be expected to vary both seasonally and with the prevailing
       weather conditions. It is recommended that groundwater presence/levels be confirmed if construction is
       undertaken during or following significant wet weather, or if a significant period of time elapses between this
       investigation and construction.
       Table 2: Summary of Particle Size Distribution Test Results

                                                  Groundwater Observations from April 2010
               Bore                       Depth                                     Reduced Level
                                           (m)                                          (m)
                 7                         2.8                                           RL3.2
                 8                         2.7                                           RL4.6
                 9                         1.6                                           RL4.2
                10                         1.2                                           RL4.0
                11                         0.5                                           RL2.5
                12                         0.9                                           RL2.0




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