Geotechnical Investigation

                             PROPOSED CALILE HOTEL NOOSA DEVELOPMENT
                             3 – 7 SERENITY CLOSE, NOOSA HEADS

6.0      GEOTECHNICAL RECOMMENDATIONS
General recommendations to help maintain the stability of the site are given in the document Some
Guidelines for Hillside Construction, which is attached.

6.1      Development Limitations
In accordance with previous practice along Serenity Close, it is recommended that all structures are founded
below a plane rising at 27° from the toe of the dune to the south of the site. It is anticipated earthworks will
include cuts for the basement level of up to about 6 m depth, with filling up to about 3 m high to form finished
surface levels. Should proposed cuts/fills exceed these quantities, Tectonic must assess the impacts on
slope stability before construction.

Due to the depth of excavations proposed and temporary shoring required, to evaluate the deeper
subsurface conditions for detailed design a deeper investigation would likely be required. Such an
investigation would likely require a series of boreholes along the proposed temporary retention alignment
using a specialised rig adopting a combination of open hole auger drilling and cased wash boring to depths
in the order of 15 m BGL. Tectonic can provide a fee proposal to undertake such an investigation following
preparation of detailed design drawings and removal of existing vegetation.

6.2      Earthworks – General
6.2.1       Site Preparation and Trafficability
Following removal of the existing vegetation (where required), buildings and associated construction
elements (e.g. footings, services, etc.), any tree stumps and large roots should be ‘grubbed out’. Any
organic rich topsoil should then be stripped and set aside. Based on the boreholes, topsoil stripping depths
should generally range between 0.1 m and 0.4 m BGL. Existing uncontrolled fill across the proposed
development area should be stripped and set aside. It is possible that deeper pockets of topsoil or
uncontrolled fill may exist and deeper, localised grubbing out of tree roots may be required. Following
stripping of any unsuitable materials, the subgrades must be ‘proof rolled’ and visually assessed by a
civil/geotechnical RPEQ to ensure no heaving or unacceptable subgrade deflection occurs.

Topsoil materials must not be used in structural fill; however, may be placed across landscaping areas.
Unsuitable natural material such as any saturated, loose or soft materials encountered should also be
removed during subgrade preparation for bulk earthworks.

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 vibrating plate). Care must be taken with the use of vibratory equipment (e.g. compactors or sheet piling)
to ensure that there are no adverse impacts on surrounding structures. The impacts from ground vibration
must be closely monitored and managed during construction. It would be prudent to conduct a dilapidation
survey of neighbouring structures prior to commencement of construction.
The exposed natural subgrade following excavations will likely be in a loose condition and must be
compacted by several passes of a vibrating plate or minimum 4 tonne vibrating smooth drum roller, in
conjunction with surface application of ample water, to achieve the required compaction.

Due to the potential for development of poor trafficability during construction, placement of a minimum
150 mm thick granular working platform may be required across laydown areas. Specific platform design
would be required prior to mobilisation and trafficking of any heavy mobile plant on the site (e.g. mobile
cranes, concrete pumps or piling rigs).

Due to the highly permeable nature of the sands at this site, stormwater is expected to rapidly infiltrate the
ground, making un-sealed surface drainage ineffective for the control of flows. Any sealed areas should be
graded to ensure free drainage of stormwater away from construction areas, and to a control point(s).




7 October 2022
Report No. 22239-001-Rev0                              14