J000154-001-R-Rev0_ASS Investigation Report · RAP15/0034

J000154-001-R-Rev0                                                                              November 2015


In general accordance with the above and based on our experience in the area, 3 boreholes (designated
BH1 to BH3) were drilled using a 4WD mounted drill rig (with vibro-core and push tube sampling capabilities)
to depths of up to 3.5 m bgl across the site. Due to the size of the site (616 m 3) and our experience in the
area it was determined that 3 boreholes would be sufficient to assess the presence or absence of ASS
across the site.
The fieldwork was carried out by an experienced environmental scientist from Core on 5 November 2015.
Borehole locations are shown on Figure 1, and reports of boreholes are attached in Appendix A along with
explanatory notes.
To enable groundwater monitoring, and allow for groundwater sampling, BH1 was completed as a
groundwater monitoring well (designated GW1).
Soil samples were recovered from all boreholes at approximately 0.25 m intervals to the depth of
investigation. ASS sampling protocols outlined in the “Guidelines for Sampling and Analysis of Lowland Acid
Sulfate Soils (ASS) in Queensland 1988” (Ahern et al., 1998) were observed in the field in order to minimise
oxidation of the samples prior to laboratory testing.

5.2.1        Groundwater Monitoring
Groundwater quality monitoring was undertaken at GW1 in order to provide a ‘snap shot’ of the water quality
of the site for future reference (e.g. ‘baseline’ data) and to enable an appraisal of the influence of ASS (if
any) on water quality.
The groundwater level in GW1 was measured by an experienced environmental scientist on 5 November
2015. A groundwater sample was recovered and screened in the field, after initial purging. Water samples
were tested in field for temperature, pH, salinity and electrical conductivity (EC) using an Aquaread
‘Aquaprobe’ AP 2000-D model water quality analyser.
The sample was then dispatched to Eurofins/MGT (Eurofins) to undergo further analysis. Eurofins is a
National Association of Testing Authorities (NATA) accredited for the analytical tests. Results of groundwater
monitoring are summarised in Section 6.4. Eurofins laboratory results are attached in Appendix B.
Groundwater sampling, field testing, sample handling and dispatch procedures were performed in
accordance with Core procedures, the Department of Environment and Heritage Protection (EHP) Monitoring
and Sampling Manual 2009 Version 2 September 2010 and the Murray Darling Basin Groundwater Quality
Sampling Guidelines (MBDC 1997).

5.3      Laboratory Testing
A total of 42 samples were screened at our laboratory to assess field pH (pHF) and pH after oxidation (pHFOX)
using 30 % hydrogen solution.
The pHF/pHFOX screening method consists of two steps. In the first step, the field pH of a 1:5 soil/water
suspension is measured (pHF). In the second step, a 30% Hydrogen Peroxide solution is added to a second
sample of the same material which is then heated to accelerate the oxidation of the sample. The pH after
oxidation (pHFOX) is then measured. A significant difference between the pH F and pHFOX results is an
indication of potential acid sulfate soils (PASS); however, test results may be affected by other inclusions
such as shell material and organics.
Based upon the results of pH screening tests, 12 samples (approximately one sample per metre per
borehole) were selected and dispatched to Eurofins to undergo quantitative analysis by the Chromium
Reducible Sulfur (SCR) suite in accordance with ASS Method 23F and 22B laboratory procedures of Ahern et
al (2004).
This SCR method includes analysis of ‘inherent buffering capacity’ from naturally occurring alkaline materials
(i.e. calcite, coral debris, fine shell fragments) and 'retained acidity' which includes sulfur held in stable
oxidation minerals such as 'jarosite' and allows for calculation of 'net acidity'. The SCR test method was
selected in preference to the Suspension Peroxide Oxidation Combined Acidity & Sulfur (SPOCAS) method




                                                       3