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

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To provide confirmation of the above qualitative testing, quantitative analytical testing was
carried out on selected samples, generally with the greatest difference in pH f and pHfox readings
and strongest reaction using the Chromium Suite method.
•    Chromium reducible sulfur (SCR) values where greater than 0.01 %S indicates a significant
     level of sulfide, and where greater than 0.03 %S then the soil has a potential acidity level
     exceeding the action criteria. None of the samples tested exceeded 0.03 %S, however two
     samples tested indicated a significant level of sulfide.
•    Titratable actual acidity (TAA) values greater than 18 mol/t indicates the soil has an acidity
     level exceeding the action criteria. All but one sample tested returned TAA values greater
     than 18 mol/t.
•    Where the sulfur in KCl extract values (SKCl) is less than 0.03 %S, then the soil has little or no
     history of sulfide oxidation. A low SKCl combined with a low SCR indicates the measured acidity
     is not likely attributed to sulfides and further development of acid is likely to be low.

Generally, the action criterion from the chromium suite of tests, which triggers a requirement for
ASS disturbance to be managed, derived from the Soil Management Guidelines (Dear, et al., 2024)
are as follows:
•    Net Acidity (TAA + SCR + SNAS) of greater than or equal to 0.03 %S for soils greater than 1000
     tonnes of disturbance.
The action criterion was exceeded in all but one of the samples tested. The measured acidity is
likely to be attributed mostly to AASS.

       6.9.3    Management and Treatment of ASS

‘Ag lime’ should be used as the preferred neutralisation agent for the management of AASS as it
is usually the cheapest and most readily available product for soil neutralisation. This material is
mildly alkaline (pH of 8.5 to 9), of low solubility, and does not present any handling problems. ‘Ag
lime’ comprises calcium carbonate typically made from limestone that has been finely grounded
and sieved to a fine powder.

Based on the laboratory test results, an indicative liming rate for neutralisation of the AASS
material likely to be disturbed would be 12 kg/m3.

It is recommended that a guard layer of neutralising agent (eg. aglime) be spread under any
stockpiles and over exposed excavation surfaces to limit the generation of acidity and any
leachate emerging from the surface. A nominal guard layer rate of 4 kg/m2 is recommended.
Reapplication of the guard layer will be necessary under areas of repeated temporary stockpiling.

It is generally preferable if an ‘ag lime’ with a purity of 95% or better is used (ie. NV >95, where NV
is the neutralising value, a term used to rate the neutralising power of different forms of materials
relative to pure, fine calcium carbonate which is designated NV = 100). The above lime dosing
rates should be adjusted by a factor of 100/NV.

Sampling for verification testing should be undertaken to confirm that the ASS has been
adequately neutralised. A minimum of at least one sample for every 500 m3 should be taken for
verification testing. The sample shall comprise a split from at least six random subsample
locations across the treatment area or stockpile. This method reduces the likelihood of sampling
a small patch of under- or over-treated material, and also helps prevent sampling bias. Treated




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