Reference Document - OPW23 0189

 Project No. PG-10899                                                                                                      Page | 5
 November 2023
 Ref: PG-10899, 2023-10-16, ASR VER 3
 DD Sunnyside CD Sunnyside Pty Ltd – Acid Sulfate Soil Investigation - Proposed Residence, 30 Mossman Court, Noosa Heads




Typically the groundwater levels in the area are encountered at levels of
approximately RL 0.5m to RL 1.0m. Fluctuations of +/- 0.5m are typically noted in the
area.

Increases in the groundwater levels often occur following significant rainfall events
(floods) with the groundwater levels to as much as RL 1.5m to RL 2.0m being noted in
the area.

6.0 LABORATORY TESTING

Laboratory testing was undertaken in general accordance with the
recommendations outlined in the QASSIT 'Acid Sulfate Soils Laboratory Methods
Guidelines 2004' and was undertaken by Pacific Geotech. The results of the testing
program are appended to this report.

The testing program comprised of initial screening tests on recovered samples,
followed by quantitative testing using the Chromium Reducible Sulfur (CRS) suite.

Screening Tests

Screening tests were undertaken on soil samples collected from borehole BH01. Two
small sub-samples of each soil sample were prepared; one sub-sample from each
sample was mixed with approximately 20mL of distilled water, and the other sub-
sample mixed with approximately 20mL of hydrogen peroxide (H2O2), buffered to a
pH of 5.4 with sodium hydroxide.

Slurry pHs were measured with a calibrated pH meter. The pH of the distilled water/soil
slurry (pHF) was measured approximately one hour after mixing, whilst the pH of the
hydrogen peroxide/soil slurry (pHFOX) was measured approximately one to two hours
after mixing.

The pH screening tests can be used for the preliminary identification of a potential or
actual ASS using a combination of three trigger factors as follows:

     a) The strength of the reaction with peroxide is a useful indicator but cannot be
        used alone. Organic matter and other soil constituents such as manganese
        oxides can also cause a reaction.

     b) A pHFOX value at least one unit below pHF may indicate a potential ASS. The
        great the difference between the two measurements, the more indicative the
        value is of a potential ASS. The lower the final pHFOX value the better the
        indication of a positive result.

     c) If the pHFOX is less than 3, and the other two conditions apply, then it strongly
        indicates a potential ASS. The more the pHFOX drops below 3, the more positive
        the presence of sulfides.

In broad summary, several of the ‘natural’ soil samples tested did show a strong
indication of ASS presence at depths greater than 3m below ground level. The results