07/2023 - Response to Information Request [As Published] · 132007.2023

*

the following areas are regarded as having higher environmental sensitivity for
treated soil placement

* within 50 metres of a drainage line, stream or other surface water

* where the watertable is within 2 metres of the surface

* where the site is below the 50 year flood line.

Should these more sensitive locations be selected for placement then it is
recommended the excavated soil be treated at the source and validation tests be
proved successful prior to placement.

e. Bunding of Excavated Soil

*

It is proposed to bund any area with untreated disturbed soil, either at the
excavation site or placement site.

It is proposed to size the bund to retain a Q=2, 60 minute storm event plus
a 200 mm freeboard. For relatively flat areas a surrounding bund height of 500
mm is likely to be adequate.

All excavated soil will be stored in a bunded area by the end of the working day
unless lime treatment has been undertaken.

The bund must either be constructed from non-ASS material or from lime treated
ASS material.

The bund should drain to a sump or other water collection point.

The bund floor and wall should be clay or other impermeable material to
minimise infiltration of water. The floor should have a hydraulic conductivity of
less than 1 x 10% m/d for a minimum depth of 400 mm or have an equivalent
resistance to the passage of drainage water. Compaction is likely to be required
to achieve this level of hydraulic conductivity.

Any water trapped within the bund or excavation site must be pH tested
prior to discharge. The pH must be adjusted to be within the range of 5.5
to 7.5 prior to discharge. The use of calcium hydroxide (builders lime) is
suggested for this purpose.

If a bund is impractical smaller stockpiles can be covered with plastic sheeting
or similar materials to exclude rainwater. The stockpile must not be located in a
runoff flow path.