geotech

                              PROPOSED UNIT DEVELOPMENT
                              9 BOTTLEBRUSH AVENUE, NOOSA HEADS

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

Construction areas and surrounds should be graded to shed surface water runoff. Swale drains should be
constructed along the crest and toe of any cuts, and above fill batters, where possible. Drains are to be
graded to discharge collected waters to a control point(s) before release into existing stormwater
infrastructure.

It should be noted that during wet weather, the natural soils may cause sediment run-off. Appropriate
erosion and sediment control measures must be installed prior to commencement of earthworks at this site.

6.2.2       Excavations
Excavations through the existing 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:1H in medium dense (or denser) sand for batters up to 3 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.

If filling or permanent cuts exceed 1 m, then these must be retained. Permanent cut and fill batters up to
1 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 above temporary batter slopes will not be able to be achieved, due to spatial restraints, and so
temporary shoring will be required (e.g. sheet piles) as per the recommendations in Section 6.4 below.
Excavations in close proximity to existing structures, including on neighbouring properties, will need to be
specifically designed to prevent undermining. It is recommended that footing exposures or confirmation of
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).
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).

 6.2.3       Filling
The existing sandy soils (fill and natural) where free of deleterious materials (e.g. vegetation, building debris
etc.) may be reused as structural fill, subject to appropriate moisture adjustment. It should be noted that

13 July 2021
Report No. 21169-001-Rev0                               10