Compiled Reference Document - MCU25/0020 (As Published)

6.2.4        Filling
Based on the supplied architectural drawings, and the proposed construction methodologies, no filling
works are anticipated as part of the development, although controlled filling may be required for over-
excavation of unsuitable materials exposed in the foundation subgrade if a raft footing system is
adopted. It is recommended that any imported fill for the project comprise good quality, low reactivity
materials (e.g. non-descript crushed rock, ‘clean’ sands, or similar), that comply with the following:
   Minimum CBR of 10 %
   Maximum plasticity index of 15 %
   Shrink-swell index ≤ 1 %
   Maximum particle size of 100 mm
Fill material should be placed in 200 mm thick (loose thickness) layers and be compacted by repeated
rolling using a minimum 4 tonne roller (vibration on if safe to do so) to achieve a dry density ratio of at
least 98 % of the maximum Dry Density Ratio (DDR), based upon the Standard Compaction method, or a
Dry Density Index of at least 75 %.
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. Level 1 geotechnical inspection and testing of all structural
fill is recommended, with density testing at a Type 3 frequency.
Due to the close proximity of structures on surrounding blocks and underground services, care will need
to be taken with any activities which may cause excessive ground vibrations (e.g. fill compaction and
excavations). It would be prudent to conduct a dilapidation survey of nearby structures before
commencement of construction, and to monitor ground vibrations during construction works. When in
proximity to settlement sensitive structures or services, only static compaction rolling should be
conducted, particularly if excessive ground vibrations are encountered, and/or to prevent pumping of
pore water leading to subgrade heaving/strength loss over the subgrade generally.


6.3          Temporary and Permanent Retention
Excavations for the basement and floor slab are expected to range between about 7 m and 8 m BGL.
Given that the planned basement footprint extends close to site boundaries, excavations will cover most
of the site. Some form of temporary shoring will be required to support the excavation.

6.3.1        Temporary Batters
Temporary batters in loose to medium dense sands above the groundwater table may be formed at
1V:1.5H provided that they are not subjected to surcharge loads (e.g. from surrounding buildings) and
are protected from saturation by rainfall. Flatter temporary batters would be required where affected by
groundwater seepage or rainfall. Excavations below the groundwater table will require temporary
shoring and dewatering to actively lower groundwater below the base of the excavation, and to control
groundwater inflow. Where the above temporary batters cannot be achieved (e.g. due to spatial
restraints etc.), retention will be required (refer to Section 6.3.2). Any excavations required adjacent to
existing structures or infrastructure will need to be specifically designed to ensure that the structures are
not undermined.




Geo-environmental Investigation Proposed Residence
4 June 2025 | 25040-001-Rev1                                                                               12