Reference Document - RAL25/0020 & OPW25/0194 (As Published)

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as a broad guide as many factors influence excavatability including plant condition and operator
expertise.

6.4    Batter Slopes

Near vertical temporary excavations less than 1.5 m depth in dry, stiff or stronger clays are likely
to be suitable for the short term footing construction or installation of underground services
provided there are no sensitive services or structures, or vehicular trafficked areas close to the
excavation crest.

It should also be noted that excavations in firm silt and loose sands have the potential to ‘collapse’
unexpectedly in a trenching situation, particularly where groundwater seepage is encountered.
Battering or formwork will be required to prevent loss of material and slumping into the
excavations.

All excavations in firm silt, or excavations greater than the above mentioned depths will need to
be benched, battered or positively supported for stability and prior to personnel entering the
excavation.

Suitable unsurcharged temporary and permanent batter slopes up to 3 m high are presented in
Table 5. Specific advice should be sought from Douglas for batter slopes greater than 3 m in
height. Where groundwater seepage is encountered, or where there are any additional loadings,
batter slopes will need to be considerably flatter.

Table 5: Batter Slopes (unsurcharged, up to 3 m in height)
                                                             Safe Batter Slope (H:V)
 Material
                                                             Short Term                    Long Term
 Firm silt                                                   2.5:1                         3:1
 Controlled fill*, stiff (or stronger) clays                 1:1                           2:1
Notes: * Depends on fill material type and level of compaction. Assumes a clayey fill material compacted under ‘Level 1’
Inspection and Testing.


The above temporary batter slopes are suggested with respect to slope stability only, and do not
allow for lateral stress relaxation which may result in movement of nearby inground services or
shallow footings. If such services or footings are settlement sensitive and are located near the
crest of the cut face, then the excavation may have to be positively supported.

Long term slopes may need to be flattened to 3H:1V or less, in order to allow vehicle access for
maintenance of grass. It is recommended that all batters incorporate crest and toe drainage. The
batters should also be covered with topsoil and vegetation to provide long term erosion
protection.

6.5    Soil Reactivity and 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 AS 2870.




Proposed Subdivision                                                                               237894.00.R.001.Rev0
12-14 Gympie Street, Tewantin                                                                             October 2025