Acid Sulfate Report

                             25 EDWARD STREET, NOOSAVILLE
                             PROPOSED DUPLEX DEVELOPMENT

5.0      GEOTECHNICAL ASSESSMENT

5.1       Earthworks
5.1.1        Site Preparation

Existing fill (presumably uncontrolled) and organic rich topsoil should be stripped and set aside. Stripping
depths for topsoil will typically range from 100 mm to 200 mm, to remove organics bearing soil. This material
must not be re-used as structural fill, however may be retained on site for later landscaping use, if required.
Fill material below topsoil to a depth of 0.5 m BGL should also be removed, but may be reused where free of
deleterious matter and compacted under controlled conditions.

Subgrade areas should be ‘proof rolled’ using a fully laden water cart or minimum 4 tonne roller in order to
identify any ‘soft spots’. Treatment of ‘soft spots’ may involve excavation and replacement with select fill or
tyning, appropriate moisture adjustment and compaction. Proof rolling should be carried out in the presence
of an experienced engineer.

5.1.2        Excavations

Excavations are expected to be within mostly loose to medium dense sands, and should be achievable using
small excavator(s) (3 to 5 tonne).

The groundwater table was recorded during subsurface investigation at depths between 1.2 m and 1.4 m
BGL. Therefore, some temporary excavations, such as for services, may extend below the groundwater
table. Temporary shoring of trenches, in combination with isolated (short term) dewatering, may therefore be
required. This could be achieved using trench shields in combination with dewatering well points (connected
to submersible pumps). The extent of dewatering will need to be carefully managed to ensure that there are
no adverse impacts on adjoining structures or ASS.

5.1.3        Trafficability

After stripping, the subgrade is expected to comprise loose to medium dense sand. Such materials should
provide reasonable trafficability, however placement of rock fill (say 150 mm thick layer of 75 mm ‘ballast’)
may be required to maintain subgrade stability for any heavily trafficked areas.

Specific design will need to be carried out to determine working platform requirements for any heavy plant
(e.g. cranes or piling rigs), and a thicker rock fill platform may be required than recommended above.

5.1.4        Filling

Due to the close proximity of the neighbouring houses, and presence of underlying loose sand, it is essential
that earthworks be carried out in a fashion to minimise ground vibrations. No vibratory equipment should be
used. It would be prudent to conduct a dilapidation survey of nearby structures prior to construction in order
to establish a ‘baseline’ of structural condition.

Filling is expected to be up to 1.0 m deep and will need to be imported to site. Any fill required to form the
design platform levels should comprise materials which meet the following specifications:

    ▪   Minimum CBR value of 10%
    ▪   Maximum ‘fines’ content (percent passing 0.075 mm sieve) of 10%
    ▪   Plasticity index not exceeding 15%

Note: To enable minimum compactive effort without the use of vibration, it is our recommendation that the
imported fill comprise ‘roadbase’ type material.

All fill should be compacted at moisture contents within the range of ±2% of optimum moisture content for
Standard Compaction. Fill particles greater than 100 mm must be excluded. Fill should be placed in


25 August 2017
Report No. 17265-001-Rev0                               6