Attachment 4 - Geotech Report · MCU23/0030

                             50 NOOSA PARADE, NOOSA HEADS
                             PROPOSED RESIDENCE




                                                            Subject Site




Text Figure 8: Maroochy-Caloundra Acid Sulfate Soils Map 2 (NR&M-SEA-I-A0 3331)

7.3       ASS Investigation Results
Site and laboratory investigation methods are described earlier in this report in Section 4. The investigation
findings for soil and groundwater analyses are discussed below. ASS laboratory results are summarised in
Table C1 attached in Appendix C, together with laboratory test certificates.

7.3.1        Field Screen Analysis

A total of 30 samples were recovered and assessed using pH field screen analyses. Soil pH (pHF) ranged
from 4.8 to 8.2, being mostly within acidic to neutral pH range.
A combination of three factors is considered when arriving at a positive field sulfide identification using pH
field screen analysis.
      1. Strength of the reaction with peroxide.
      2. Level of difference between field pH (pHF) and oxidised pH (pHFOX)
      3. Actual value of oxidised pH (pHFOX)
All samples indicated a pH change greater than 2, and pHFOX values of less than 4, resulting in all 30
samples indicating a moderate or higher likelihood of potential acid sulfate soils (PASS) being present.
It is noted that pH screen testing is indicative only and cannot definitively confirm the presence of ASS, nor
can it quantify the nature or strength of any acidity present. Further quantitative laboratory testing was
therefore carried out on a range of samples in order to assess the strength of any acidity present, and to
quantify the level of oxidisable sulfur content, if any.

7.3.2        Quantitative Laboratory Analysis

Quantitative laboratory analyses were completed on 8 samples using the CRS suite of testing in order to
quantify the severity and nature of any actual or potential acidity present in the soil profile. The quantum of
any actual acidity was assessed using Titratable Actual Acidity (TAA), and potassium-chloride extractable
sulfur (SKCl) was used to assess the nature of the measured actual acidity. Potential acidity was measured
by the CRS method which specifically measures inorganic oxidisable sulfur (SCR). These methods are set
out in the National Acid Sulfate Soil Guidance; National acid sulfate soils sampling and identification manual
(2018) and associated ASS management guidelines.
Based on the nature of the proposed disturbance an action criteria of 0.03 %S (18 mol H+ per tonne) was
adopted for comparison with the combined actual and potential acidity results.




2 February 2023
Report No. 22500-001-Rev0                              14