Acid Sulfate Management Plan · MCU16/0103

FPE Ref: 4956-161019-1.0


increase the heavy metal concentration of the receiving waters (increasing toxicity levels by allowing iron
and aluminium to ‘fall out’) and reduce the neutralising and buffering capacity of the receiving waters. The
result of this is the degradation of environmental conditions. The lowering of pH can also have social and
economic costs such as seriously affecting building materials and structures, and the reduction of public
amenity and safety.

ASS can either be defined as actual or potential. Actual ASS (AASS) are those soils which have previously
been oxidised, while potential ASS (PASS) pose limited threat unless disturbed or oxidised. The following
are descriptions of these, as defined by Queensland State government authorities:

Actual Acid Sulfate Soils (AASS): Soil or sediment containing highly acidic soil horizons or layers affected
by the oxidation of soil materials that are rich in iron sulphides, primarily pyrite. This oxidation produces
hydrogen ions in excess of the sediment’s capacity to neutralize the acidity, resulting in soils of pH 4 or less.
These soils can usually be identified by the presence of jarosite (a yellow coloured mineral).

Potential Acid Sulfate Soils (PASS): Soils or sediments containing iron sulphides or sulfidic material that
have not been exposed to air and oxidised. The field pH of these soils in their undisturbed state is pH 4 or
more, and may be neutral or slightly alkaline.

Projects involving the disturbance of ASS must assess the risks associated with disturbance through the
consideration of both on and off-site impacts. A thorough ASS investigation (in compliance with the
Sampling Guidelines) is an essential component of risk assessment. Such an investigation is needed to
provide information on the environmental setting, location of and depth to ASS, existing and potential acidity
present in the soil, and soil characteristics. The results from the investigation determine the most
appropriate management strategy for the site.

1.3 THE INVESTIGATIONS
The investigation must aim to include the following information and techniques where possible;
     The approximate location of each borehole;
     Description of the vertical dimensions of the borehole relative to surface AHD;
     Occurrence of any groundwater;
     A brief description of the equipment and/or methods used to retrieve the samples;
     A field description for each soil profile including soil texture, colour, mottling and other diagnostic
        features (e.g. jarosite, shell);
     Results from field soil tests (field pH (pHF), pH after oxidation with hydrogen peroxide (pHFOX) and
        reaction with peroxide at 0.25m vertical intervals to the base of the soil profile; and
     Collect samples at 0.25m intervals down the soil profile e.g. surface, 0–0.25m, 0.25–0.5m etc.,
        ensuring each horizon is sampled. Samples collected to extend 1m past the deepest excavation
        point.

1.4 REPORT OBJECTIVES
This report seeks to address issues relating to ASS in accordance with the State Planning Policy—state
interest guideline Water Quality Department of State Development, Infrastructure and Planning August




October 2016                          Acid Sulfate Soil Investigation Report                                  3
                                            New Duplex, Noosaville