Reference Document - MCU26 0012 & OPW26 0034 (As Published)

spots’. Materials in any such soft spots should be excavated and replaced with select fill material,
constructed as recommended below.
Any fill materials utilised should be free of organic or otherwise unsuitable materials and compacted at
moisture contents within the range of -2 % to +2 % of optimum moisture content for Standard
Compaction.
Fill should have a maximum particle size of 100 mm for an uncompacted layer thickness of 200 mm and
shall be compacted by repeated rolling with a small compactor to achieve a dry density ratio of at least
95 % of the Standard Maximum Dry Density for cohesive soils, or 70 % Dry Density Index for any
imported cohesionless soils.
All fill must be ‘benched’ into the sloping ground. Fill should be overbuilt and then trimmed back to the
well compacted material.
Confirmatory testing must be carried out at regular intervals and further details for control and testing of
fill are given in Australian Standard AS 3798-2007 Guidelines on Earthworks for Commercial and
Residential Developments. Given the extent of earthworks proposed, it is suggested that Level 1
geotechnical inspection and testing should be conducted at a Type 3 frequency.
Excavation through the natural residual soils should be achievable using conventional earthmoving plant
(e.g. excavators with toothed buckets/soil augers) to the maximum depth of the borehole drilling.
Non-surcharged, temporary batter slopes should be formed no steeper than 1V:1H in stiff (or stiffer)
natural soils.
Non-surcharged, permanent batter slopes should be constructed at a maximum grade of 1V:2H in stiff
(or stiffer) natural soils or controlled fill up to 2 m high. Permanent batter slopes above this height are
not anticipated within the scope of the project works. Any permanent soil or fill batters would
nonetheless require erosion protection (e.g. revegetation or surface protection).

4.3       Retaining Structures
Retaining structures must be founded as described in Section 4.4 below. Engineer design and
certification of retaining walls is required where such walls:
▪     Exceed 1 m height.
▪     Are subjected to surcharge loads (e.g. from backslope, adjacent structures, etc.).
▪     Are located within close proximity to other structures (e.g. the existing shed, proposed dwelling).
We suggest the parameters as shown in Table 3 over page may be adopted for retaining wall design.




13 February 2026
26020-001-Rev0                                                                                      10 of 13