Geotech Report - Acid Sulfate Soil Assessment

 

SECTION 4 - INVESTIGATION RESULTS

44 Results

The subsurface conditions encountered in the bores are given on Bore Report Sheets included in Appendix A,
using classification and descriptive terms defined in the accompanying notes. Laboratory test report sheets are
included in Appendix B.

4.2 Subsurface Conditions

For a description of the stratigraphy encountered in the bores, the Bore Report sheets should be consulted.
However, in broad summary, the subsurface conditions encountered in the bores generally comprised a surface
layer of either fill material (in Bores 1 to 4) that varied up to a maximum depth of 0.8m, or silty sand (in Bores 5
and 6) to a maximum depth of 0.4m. In Bores 1 and 2 only, the fill was underlain by natural, dark grey-brown
silty clays that were underlain in turn by silty sands that were indurated below 2m depth. In Bores 3 to 6, the
surface fill or silty sand layer was underlain by sands.

4,3 Groundwater

Free groundwater was encountered during the drilling of four of the six bores at the depths/RLs given in Table 1.
It should be noted that groundwater levels can vary seasonally and with prevailing weather conditions.

Table 1: Observed Groundwater Depths/Reduced Levels During Drilling

Groundwater Observations

Folp Depth Reduced Level
1 0.8 RL 2.3m
"2 08 | RL23m
3 46 RL 6.0m
4 Not encountered
5 16 | RL 5.9m
6 Not encountered

44 Laboratory Testing

4.4.1 Screening Tests

Screening tests were undertaken on all soil samples collected from all bores. The screening tests comprised
two small sub-samples of soil; one mixed with approximately 20 mL of distilled water, and the other mixed with
approximately 20 mL of hydrogen peroxide, buffered to a pH of 5.0 with sodium hydroxide.

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

 

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