PART Response to Information Request · OPW11/0335

5.0         SOILS INFORMATION

Soils testing undertaken by Butler Partners (2007) involved six (6) bores drilled to depths of 2.5
meters from across the site. Surface soils were described as fill (silty sand with sub-angular
gravel) over most of the development (particularly the lower slopes), with some silty sand
observed near the eastern margin. The depth of surface fill was 0.8m on the lowest slopes, and
was about 0.2m further upslope.

Soil under the surface fill was described as dark grey-brown silty clay or silty sand on the lowest
slopes (under the thick layer of surface fill), or light grey-grown fine sand under the 0.2m of fill
further upslope. The soil texture described by these tests were used to assess the soil erosion
hazard for the SECP by an Erosion Hazard Assessment Form (Queensland Best Practice
Environmental Management Guidelines 2009).

Butler and Partners (2007) identified acid sulphate soils at isolated locations, which will require
management and treatment to neutralise any net acidity if the soils are disturbed. The affected
soils are the dark grey-brown silty clay under the 0.8 m of fill adjacent to the wetland heath on
the western margin of the development site. Butler and Partners developed a draft Acid
Sulphate Soil Management Plan (appended in Butler and Partner, 2007).

The SECP does not propose the installation of sediment ponds to collect runoff from the
building site to avoid disturbing acid sulphate soil. Instead sediment fences have been
recommended, with filter socks at outlet points to remove suspended fine sediment from the
overflow (Appendix D). The same philosophy has been applied to the Bioretention Trenches
installed for the SWMP, which will be located within additional fill placed over the existing site,
thereby also avoiding the need for excavation and potential disturbance of acid sulphate soil.

Soil tests were also undertaken by Simmonds and Bristow on the 10th July 2009. Eleven
samples of surface soils (0 - 100 mm) were collected across the site area, from the road to the
edge of the field (refer to sample location map in Appendix B). The soils were analysed for
Loss on Ignition, Total Nitrogen, Total Phosphorus, pH, and Electrical Conductivity (Table 5-1).
These soils were slightly to strongly acidic, which lessens the availability of soil nutrients
available to plants. The soils had inherently low total nitrogen concentrations, and very low soil
salinity, based on these data.

Table 5-1: The Quality of Surface Soil Measured in the Undeveloped Site
                  Soil Quality Indicator                                SS2          SS3          SS4     SS5        SS6       SS7
Conductivity (1:5 soil : water extract) (µS/cm)                           76          23          26          19      32        29
Loss on Ignition at 450°C (%)                                            2.4         1.6          1.6         1.7     3.7       2.2
pH (1:5 soil : water extract)                                            6.6         5.6          5.4         5.4     5.6       5.5
Total Nitrogen as N (mg/kg)                                             4700         3600        3600     6900       5700     4200
Total Phosphorus as P (mg/kg)                                           1000         1100         580     1100       710       700

Table 5-2: The Quality of Surface Soil Measured in the Undeveloped Site
                    Soil Quality Indicator                                     SS8         SS9          SSIO        SS11     SS12
Conductivity (1:5 soil : water extract) (µS/cm)                                97           28           49          80        53
Loss on Ignition at 450°C (%)                                                  3.2          2.9         3.1         3.1        2.5
pH (1:5 soil: water extract)                                                   5.2          5.6         5.7         6.0        6.4
Total Nitrogen as N (mg/kg)                                                 9000           5100         3900        5900     2900
Total Phosphorus as P (mg/kg)                                                  840          720         1300        1100     1700



©2012 Simmonds & Bristow Pty Ltd                          Contrast Constructions                           J-1005-310 -13 January 2012
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SCEMP_Scanlon Property Group_V3 0_ta_120113.doc                                                                            Page 6 of 24