RFI - 21327-001-Rev0 Plover St

                             PROPOSED RESIDENCE
                             34 PLOVER STREET, PEREGIAN BEACH

It is likely that the above temporary batter slopes will not be able to be achieved, due to spatial restraints,
and so temporary shoring may be required (e.g. sheet piles) as per the recommendations in Section 6.4
below. Excavations in close proximity to existing structures and infrastructure (e.g. sewer main along the
northern boundary), including on neighbouring properties, will need to be specifically designed to prevent
undermining. It is recommended that footing exposures or confirmation of existing 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).

6.2.3       Filling
The natural sandy soils where free of deleterious materials (e.g. vegetation, organics etc.) may be reused as
structural fill, subject to appropriate moisture adjustment. 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 smooth drum roller or heavy vibrating
plate).

Should importation of fill be required, it is recommended that such fill should comply with the following:

       Minimum CBR of 10%
       Maximum plasticity index of 15%
       Shrink-swell index ≤ 1%
       Maximum particle size of 100 mm

Any fill should be compacted at moisture contents within the range of ±2% of optimum moisture content for
Standard Compaction. Fill material should be placed in 250 mm thick (loose thickness) layers and be
compacted by repeated rolling using a minimum 4 tonne smooth drum roller (or equivalent, with vibration on
if safe to do so) to achieve a dry density ratio of at least 95% of the maximum Dry Density Ratio (DDR),
based upon the Standard Compaction method, or a Dry Density Index of at least 70%.

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.
Fill embankment edges must be over-filled by 0.5 m (horizontally) and then trimmed back to well compacted
material.

6.3       Building Foundations
6.3.1       Indicative Site Classification
Site classifications for footing design are determined in accordance with AS 2870-2011 Residential Slabs and
Footings, and depend on the depth of cut / fill undertaken at a site, variations in the natural soil/rock depths,
and the reactivity of the in situ soil / rock and any imported fill materials.
Based on the results of the investigation, the site is classified as Class P in accordance with AS 2870-2011
Residential Slabs and Footings, due to the presence of poor bearing capacity soils at shallow depths and
trees. If not for these factors, the site would have the characteristics of Class S, with the estimated
characteristic surface movements (‘ys’) ranging up to about 20 mm. However, due to the potential variability
in subgrade density a site classification of Class M is recommended in relation to assessment of flexibility
requirements for ground slabs, footing and plumbing design.




10 September 2021
Report No. 21327-001-Rev0                              10