MCU14/0106 Appendix E - Engineering Report

August 2004 -12- 04682104(AB)

 

7.0 ACID SULFATE SOILS

The development of potential acid sulfate soils (PASS) is commonly the result of marine or
estuarine deposition of sulfate and iron bearing sediments in the presence of an abundant source
of readily decomposable organic matter resulting in the deposition of pyrite. This pyrite is
stable within the soil so long as anoxic conditions prevail. Oxidation of this material produces
acidic conditions and oxidation typically occurs as the material is exposed above the water table
by excavation.

Previous experience and available guidelines indicate that Potential Acid Sulfate Soils (PASS)
are normally restricted in extent to recent (Holocene to Pleistocene age) soil horizons deposited
in a saline environment below RL 5m AHD. The State Planning Policy SPP2/02 Planning and
Managing Development Involving Acid Sulfate Soils applies to land, soil and sediment at or
below 5m AHD where the natural ground level is less than 20m AHD. Within such areas the
SPP applies to development involving any of the following:

> Excavating or otherwise removing 100 m’ or more of soil or sediment; or

> Filling of land involving 500 m’or more of material with an average depth of 0.5 m or
greater.

The southern part of the site is consistent with the above criteria and the proposed development
in this area involves placing fill up to about 3 m deep together with excavation for stormwater
ponds / basins. Where the ground surface elevation falls below RL 5 m AHD, the proposed
development covers an area about 150 m in total length by 15 min width. SPP2/02 is therefore
applicable to this part of the site and an assessment of potential disturbance of ASS is required.

7.1 Investigation Aims

The aims of this investigation were to:

> Conduct an ASS assessment in accordance with SPP 2/02 and Queensland Sampling
Guidelines;

> Identify the presence or absence of ASS in the proposed disturbance area; and

> Provide an indication of the likely location of ASS, and treatment methodology.

The results of the ASS investigation follow.

It should be noted that ground water was not encountered in any of the three ASS investigation

test pits. Consequently, a ground water investigation (in accordance with SPP2/02) was not
conducted.

Golder Associates