07/1586 - Response to Information Request [As Published] · 132007.1586

* Project No. 307-2624 Page 5
August, 2007

 

6.0 ACID SULFATE SOIL ASSESSMENT & MANAGEMENT

The ASS regulatory and guidance documentation (refer Section 4.1) for management of
acid sulfate soils has defined action levels for the quantitative test results, and these are
used to assess the need for an ASSMP. The following action criteria apply:-

* TAA - 18 mol H*/tonne
* Scr (%) - 0.03%

It is noted that the above action levels apply to the combined Scr and TAA results, which
should be added together (in like units).

It is seen that only one sample returned a combined value exceeding the action level of
0.03 %S by weight, or 18 mol H+/tonne. This sample was taken from borehole BH2 at
2.75 - 3.0m depth, was described as dark grey silty sand, and it was shown to contain

potential acid suifate soil only, with no actual acid.

Given the action level is exceeded by this sample, under the regulatory framework set
down in the referenced documentation, it is necessary that an acid sulfate soil
management plan (ASSMP) be established. This management plan would be executed
to ensure that the excavation operations are carried out in such a way as to limit or avoid
any adverse environmental or infrastructure impacts. However, we note that its
implementation can be viewed as precautionary, since the sample exceeding the action

level for ASS was taken from below the expected maximum excavation depth.
6.1 Acid Neutralisation

It is anticipated that the excavated material removed during the construction would be
disposed possibly by one or both of two methods. The excavated material could be used
for landscaping purposes on site, or as fill material to be used on other earthworks and

construction sites in the region.

Current experience indicates that the most effective method for limiting or preventing the
adverse consequences of acid release from the excavated actual or potential ASS
material, is by the controlled application of a suitable neutralising agent to the excavated
soil.

 

Z SOIL SURVEYS ENGINEERING