Preliminary Geotechnical Investigation · OPW21/0315

                                                                                              Page 6 of 11




trafficability, it is recommended that, in areas where loose to medium dense sands are exposed at
subgrade level, they be overlaid with 150 mm of well compacted select granular fill with a minimum
CBR value of 15%.


7.4    Foundations

High level footings may be preliminary designed using the allowable bearing pressures given in
Table 3.

Table 3: Preliminary Allowable Bearing Pressures for High Level Footings
                             Material                         Allowable Bearing Pressure (kPa)
Existing uncontrolled fill                                                      75
Medium dense (or better) natural sands                                         100

The above bearing pressures are contingent upon all footing excavations being free of any loose or
water softened material prior to the placement of concrete. All footing excavations should be inspected
and tested by an experienced geotechnical engineer from DP to confirm bearing pressures prior to
casting of concrete.

Where necessary to deepen footings in order to found into competent material, footings may be made
up with mass concrete poured to the underside of the footing, or alternatively, footings may be
constructed over mass concrete filled, backhoe excavated pedestals.

Where footings are located adjacent to underground services, the footings should extend to below
invert level for a distance of 1 m out from the trench. Beyond 1 m from the trench, the footings should
be taken to below an imaginary line drawn up at 45 degrees from the invert level. These requirements
do not override minimum structural footing base levels.

Slabs supported on high level foundations should be stiffened to suit the expected ground surface
movements.

Experience indicates that properly designed and constructed high level footings loaded as above are
likely to undergo settlements in the order of 1% of the footing width.


7.5    Acid Sulfate Soils

       7.5.1 What are Acid Sulfate Soils

Acid sulfate soils (ASS) are naturally occurring sediments and soils containing iron sulfides or sulfidic
materials, often located over extensive low-lying coastal areas, predominately below RL 5 AHD. These
soils are generally found close to the natural ground surface, but may also be found at depth within the
soil profile.




Proposed Residence                                                                     95120.00.R.001.docx
33 Wyuna Drive, Noosaville                                                                    October 2020