Sunshine Butterflies - Attachment D - 010816-2

                             OUR BACKYARD
                             468 MCKINNON DRIVE, COOROIBAH

6.0      ENGINEERING ASSESSMENT
6.1      Earthworks
No earthworks design details are available at the time of reporting.

6.1.1        Site Preparation and Trafficability
Any vegetation, tree stumps and large roots must be ‘grubbed out’ and any organic rich topsoil/unsuitable
material must be stripped from the construction area. Topsoil/unsuitable materials must not be used in
structural fill, however may be placed across landscaping areas.
Subgrade materials exposed after site stripping and trimming to design levels are expected to comprise
silty/clayey sands and high plasticity clays. Such soils could be subjected to strength loss from repetitive
vehicle loading (particularly from rubber tyred plant) or if they become wet. Due to the potential for poor
trafficability during and after wet periods, placement of a minimum 150 mm thick granular working platform
may be required along access ways and laydown areas.
Construction areas and surrounds should be graded to shed surface water runoff. At the end of each
working day, subgrades should by ‘sealed off’ by compacting the surface with a smooth drum roller.

6.1.2        Excavations
Excavations in the natural soils should be achievable using conventional earthmoving equipment (e.g. small
to medium excavators) with toothed bucket attachments.
Temporary cuts in medium dense (or denser) sands and stiff (or stiffer) clays may be formed no steeper than
1V:1H, with permanent batter slopes in such materials formed at 1V:2H, or flatter if possible (1V:3H). Flatter
batters may be required if groundwater seepage is encountered, or if earthworks are undertaken during or
immediately following a period of heavy rainfall.

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

6.1.3        Filling
The existing soils are expected to be suitable for re-use as structural fill, subject to appropriate moisture
adjustment and removal of organic and deleterious materials. However, considering the high plasticity and
low CBR of the natural clays, such materials should be excluded from structural fill areas.
Should importation of fill be required, it is recommended that such fill comply with the following:

       Minimum CBR of 10%
       Maximum plasticity index of 15%
       Maximum particle size of 100 mm
All structural fill should be compacted at moisture contents within the range of ±2% of optimum moisture
content for Standard Compaction. Fill should be placed in 250 mm thick (loose thickness) layers and be
compacted by repeated rolling to achieve a dry density ratio of at least 95% of the maximum Dry Density
Ratio (DDR), based upon the Standard Compaction method. Compaction to 100% DDR will be required in
fill layers within 0.3 m depth of the design subgrade level.
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.




4 May 2016
Report No. 16081-001-Rev0                               6