Preliminary Geotechnical Investigation · OPW21/0315

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Based on the results of the screening tests and visual inspection of the samples, selected samples
were subjected to more rigorous Chromium Suite analytical testing. The results of this testing are
discussed further in Section 7.5.2 with detailed report sheets attached.

Preliminary field screening and chemical laboratory tests for ASS were carried out with reference to
the QASSIT Guidelines (Ahern, C R; Ahern, M R; Powell, B, 1998), the Soil Management Guidelines
(Dear, et al., 2014) and the Laboratory Methods Guidelines (Ahern, McElnea, & Sullivan, 2004).


7.     Comments

7.1    Site Classification

Site classification of foundation soil reactivity strictly only applies to residential buildings up to two-
storeys and to other buildings of similar size, loading and flexibility as defined in accordance with
AS2870.

In the absence of documentation to confirm that the existing fill was placed in a controlled manner to a
specified engineering standard, the fill is deemed to be ‘uncontrolled’. In addition, given the presence
of relatively loose sands with an allowable bearing capacity of less than 100 kPa, the site would then
be classified as ‘Class P’ (problem site) requiring design by engineering principles.

However, it is anticipated that the relatively loose sand fill will be excavated and removed as part of
the basement excavation. Provided all footings (ie. edge beams, internal beams and load support
thickenings) extend through any fill and found into the natural strata, the site maybe be reclassified
based on engineering principles. Based on the investigation results, the existing sand fill and natural
sand material encountered on this site are non-reactive to changes in soil moisture content, consistent
with Class A conditions.


7.2    Basement Construction

Excavations in the order of 3 m below existing site levels are anticipated to achieve the proposed bulk
excavation level for a basement.

Based on the ground conditions encountered in the bore, excavation of the existing fill and natural
sands could be undertaken using conventional small to medium sized earthmoving equipment, such
as drotts, backhoes or 15t (or larger) excavators. The use of pneumatic tools or hydraulic rock
breakers will be required to assist in the excavation of any existing concrete.

It should be recognised that the excavatability estimates are based on materials encountered at the
bore location only and that conditions may prove more difficult (or easier) for excavatability beyond the
bore location and the depths drilled as part of this investigation.

Where space permits, battering would be the most economic option to stabilise the excavation faces.
Temporary batter slopes in fully dewatered conditions should be no steeper than 2.5H:1V. Battering is




Proposed Residence                                                                      95120.00.R.001.docx
33 Wyuna Drive, Noosaville                                                                     October 2020