Acid Sulphate Investigation · OPW19/0098

August 2003 +2 03683042(AA)

 

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4.0 METHOD OF INVESTIGATION
4.4 Field Work

The October 1998 “Guidelines for sampling and analysis of lowland Acid Sulfate Soils (ASS)
in Queensland” (Revision 4.0) produced by QASSIT (Queensland, Acid Sulfate Soils
Investigation Team) recommends four boreholes for development sites of less than one
hectare. Less than one hectare of the site is below RL 5 m, and about 1000 m? in the north-
western corner will not be developed. oO

Four boreholes (BH1 to BH4) were initially drilled using vibro-vacuum coring (VVC) rig
mounted on a 4WD utility drill rig to 2 m depth across vehicle-accessible. parts of the site
below RL 5 m. These boreholes were located above the previously mentioned break-in-slope ”
which defines the edge of the low-lying land (that intersects the north-eastern part of the site).

In order to assess the extent of ASS in the low-lying part of the site, one additional borehole
(BHS) was drilled by hand auger to refusal at 1 m depth. Borehole positions and site features
were located using a hand-held GPS unit having + 3 m accuracy for E/N coordinates.

Samples for ASS testing were recovered from the five boreholes at 250 mm intervals to the
depth of investigation. ASS sampling protocols in the field were conducted to minimise
oxidation prior to laboratory testing, and followed the QASSIT Guidelines.

The fieldwork was undertaken by experienced geotechnical personnel on 29 and 31 July 2003
and the borehole locations are shown in Figure 1. Results of the fieldwork are presented in
the Reports of Boreholes in Appendix A, along with explanatory notes.

4.2 Laboratory Testing

Tests to assess field pH and pH after oxidation (with 30% hydrogen peroxide solution

‘buffered to pH>4.5) were conducted as an initial screening procedure to help select samples

for Total Actual Acidity (TAA) and Chromium Reducible Sulfur (Scr) testing. Based upon
our assessment of the pH test results, a total of ten sub-samples were analysed by Mazlab at
Chinderrah, NSW using Method 22 as detailed in the QASSIT guidelines. The pH screening
was also conducted by Mazlab.

The ASS test results are given in Appendix B and are discussed in Section 6.0.

Golder Associates