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

lf stormwater becomes ponded in bunded or disturbed areas affected by the presence
of acid sulfate soil then the pH should be checked prior to any off-site discharge. The
pH should lie in the range of 5.5-8.5. If the pH is less than 5.5 then then pH can be
raised by adding builders lime (slaked lime or calcium hydroxide). The builders lime is
more soluble than agricultural lime but agricultural lime can be used if necessary. The
lime should be added in doses, mixed and the pH measured. The pH is likely to resist
change until it rises towards a value of 5.5. After this it will often rise quickly with small
additions of lime. The mixed water will be turbid but should settle overnight. It is
preferable to allow the sediment to settle prior to any discharge. If discharge of turbid
water is necessary then sediment can be removed by filtration through sand filter tanks
or by slow overland flow across grassed areas.

Water quality should conform to the following criteria prior to discharge:

pH 5.5-8.5

dissolved oxygen >=80% saturation
turbidity < 100 NTU
suspended solids <25 mg/L
dissolved aluminium <0.1 mg/L
dissolved iron <1 mg/L

i. Groundwater

k. Unexpected Groundwater

Geotechnical studies of the site have not revealed the presence of groundwater or strata
likely to provide a significant groundwater flow. In the event of groundwater being
encountered the management plan will follow the actions described for "Ponded Water"
in section 4.i.

5. VALIDATION

Validation testing is regarded as an essential component of the management pian. Due
to the variable nature of mixing soil and lime, care must be exercise to obtain a
representative sample for validation analysis.

The engineer, project manager, geotechnical officer or other suitably qualified person
must ensure the validation testing has been performed and the results are satisfactory.
A copy of the test certificates is to be submitted to the local authority (or referral
agency).

a. Validation Sampling

*

The sub-samples must be representative of the treated soil volume. The location
of the samples should span the depth as well as the horizontal area for placed
soil. For stockpiled soil the samples should be evenly spaced through the soil
mass.

* The distribution of lime in a lime treated soil mass is typically highly variable on
a small scale. Whilst this mixing is adequate on a "landscape" scale it makes
accurate sampling difficult. It can be expected to collect some sub-samples with
no lime and others with a high lime content. It is necessary to collect a large
number of sub-samples to form a composite sample that provides an "average"