Acid Sulphate Investigation · OPW19/0098

August 2003 -4- 03683042(AA)

 

pH; and pHyox Was measured by the analytical laboratory on all samples and the results are
summarised in Table 2.

Soils at the site were found to be moderately acidic with pH, values (natural state) ranging
between 3.5 and 4.3. ,

6.2. Summary of Soil Analysis Results
Table 1 shows the ASS action levels adopted by Queensland authorities based on three broad
texture categories (QASSIT Guidelines - October 1998). These categories have been used to

highlight significant results in Table 2, based on the Action Criteria for coarse textured soils.

Table 1: ASS Action Criteria, . .

 

 

 

 

Coarse Texture $5 0.03 18 0.03 18
Sands to loamy sands
Medium Texture 5-40 0.06 36 0.03 18
Sandy loams to light
clays
Fine Texture 240 0.1 62 0.03 18
Medium to heavy

 

 

 

 

 

 

 

clays and silty clays

 

It is estimated that up to about 500 tonnes of soil will be disturbed at the site by excavation in
the south-west corner and elsewhere for underground services. Given the fine texture of the
soil (silty clay) the guidelines require the adoption of Action Criteria being 0.1% for
oxidisable sulfur and 62 mol H+/tonne for acidity.

The data quantifying the acid generating potential for soils sampled within the site have been
collated and are summarised in Table 2. Laboratory reports are presented in Appendix B.

Samples with pH drops of 2.0 or more pH units or pH < 3 after oxidisation are highlighted in
Table 2 together with Scr % and TAA values above the QASSIT action levels.

Golder Associates