13. Existing DMP (2006)

7.0 Acid Sulphate Soils

Noosa Council will follow the best practice environmental management, as outlined
in NRM s Soil Management Guidelines, to avoid environmental harm. Noosa Council
will manage the dredge operations based on the following Soil Management
Guideline principles:
   1. ASS will be avoided by shallow dredging to a maximum depth of -2.5 metres
       AHD.
   2. If ASS is present hydraulic separation of sulphides and strategic reburial will
       be undertaken to ensure that any pyrites are kept in anaerobic conditions.
   3. There will be no stockpiling of untreated ASS above the permanent
       groundwater table.
   4. Selection of a dredge site will be considered only after laboratory analysis of
       ASS has been completed.




7.1 PASS Testing and Operations

Soil Surveys Engineering P/L tested areas located upstream from Munna Point along
Gympie road, Noosaville (Figure 1) for acid sulphate soils (ASS) in November 2006.
Four boreholes were drilled 50+ metres from the riverbank and to a depth of 4 metres
finishing, at times, 2 metres below the proposed dredge depth (Soil Surveys 2006).
Vibracore drilling method provided a continuous sample of the subsurface soil, which
is retained within a plastic sleeve. Samples were tested at 250mm depth intervals in
each of the boreholes (a total of 56 samples) for potential acid sulphate soils (PASS)
analysis. Each test sample was assessed for both the field pH (pHF) and oxidised pH
(pHFOX) of the material. A pHFOX value of less than 3 indicates a strong likelihood of
the soils being PASS. The three (3) samples representing the depth interval 3.25m to
4.00m (borehole termination depth) in borehole BH2 returned pHFOX values of 2.4,
suggesting the presence of PASS material.       The pHFOX values of all remaining
samples were between 3.2 and 6.8. (Soil Survey 2006).




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