Appendix C - Geotech Report · RAL22/0021

                             PROPOSED RESIDENTIAL DEVELOPMENT
                             39 PICTURE POINT CRESCENT, NOOSA HEADS

6.2.2       Excavations
Excavations through the soils should be achievable using conventional earthmoving plant (e.g. small or
larger excavators with toothed buckets). Temporary unsurchaged cuts in the very loose to loose sand could
be formed at 1V:2H, and at 1V:1.5H in medium dense (or denser) sand, for batters up to 4 m in height. Flatter
batters or temporary retention may be required if groundwater seepage is encountered or if sloughing of dry
sand occurs at the batter surface. Deeper cuts, if required, should be specifically assessed by Tectonic.

Permanent cuts or fills greater than 1 m must be retained. Permanent cut batters up to 1 m depth; and fill
batters up to 0.5 m high shall not exceed 1V:2.5H. Any permanent soil and fill batters will require erosion
protection (e.g. revegetation or surface protection).

It is likely that the above temporary batter slopes will not be able to be achieved, due to spatial restraints,
and so temporary shoring may be required (e.g. sheet piles) as per the recommendations in Section 6.4
below. Excavations in close proximity to existing structures and infrastructure (e.g. sewer main within the
site), including on neighbouring properties, will need to be specifically designed to prevent undermining. It is
recommended that footing exposures or confirmation of existing foundations via certified building plans be
undertaken to assess the possibility of undermining. If undermining is a potential issue the existing
structures may need to be underpinned or excavations may require temporary shoring.

The advice of a suitably qualified and experienced RPEQ structural engineer must be sought regarding any
potential undermining and design and construction of any underpins/temporary shoring (if required).

The above recommendations do not supersede any existing safety regulations or legislation applicable to
excavations (e.g. limits on personnel entry into trenches).

6.2.3       Filling
The natural sandy soils where free of deleterious materials (e.g. vegetation, organics etc.) may be considered
for re-use off site as structural fill, subject to appropriate moisture adjustment. It should be noted that
compaction of such relatively ‘clean’ sands as structural fill requires the addition of substantial volumes of
water (‘flooding’) combined with the use of vibratory compaction equipment (typically a smooth drum roller or
heavy vibrating plate).

Should importation of fill be required, it is recommended that such fill should comply with the following:

       Minimum CBR of 10%
       Maximum plasticity index of 15%
       Shrink-swell index ≤ 1%
       Maximum particle size of 100 mm

Any fill should be compacted at moisture contents within the range of ±2 % of optimum moisture content for
Standard Compaction. Fill material should be placed in 250 mm thick (loose thickness) layers and be
compacted by repeated rolling using a minimum 4 tonne smooth drum roller (or equivalent, with vibration on
if safe to do so) to achieve a dry density ratio of at least 95 % of the maximum Dry Density Ratio (DDR),
based upon the Standard Compaction method, or a Dry Density Index of at least 70 %.
Confirmatory compaction testing must be carried out at regular intervals. A minimum of two tests per vertical
lift is recommended where structural fill heights are to exceed 300 mm. Further details for control and testing
of fill are given in Australian Standard AS 3798-2007 Guidelines on Earthworks for Commercial and
Residential Developments.

Fill embankment edges must be over-filled by 0.5 m (horizontally) and then trimmed back to well compacted
material.




10 February 2023
Report No. 22511-001-Rev0                              13