RFI - Attachment G - Acid Sulfate Soils Investigation

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4.     Field Work Methods

The field work was carried out on 24 April 2019 and comprised the drilling and sampling of four bores
(designated Bores 1 to 4). The bore locations were set out by an experienced geotechnical engineer
from DP with reference to site features, with the locations and surface levels recorded using a real-
time DGPS device. The approximate bore locations are indicated on Drawing 1 in Appendix B.

The bores were drilled to 4.0 m depth using a 4WD mounted Jacro 200 drilling rig using continuous
flight augers fitted with a tungsten carbide (TC) bit. Pocket penetrometer (pp) testing was carried out
within Bores 3 and 4 to assess the strength consistency of the subsurface soils. On completion, the
bores were observed for groundwater seepage and then backfilled with spoil tamped in the hole.

The field work was undertaken by experienced geotechnical personnel under the supervision of an
experienced geotechnical engineer from DP, who logged the bores and collected samples for visual
and tactile assessment and for subsequent laboratory testing. Strata identification was undertaken
through observation of cutting returns and recovered samples.




5.     Field Work Results

The subsurface conditions encountered in the bores are described in detail on the borehole logs in
Appendix C, together with accompanying notes which define the classification methods and
descriptive terms used. The depths were measured below existing surface levels at the time of
investigation.

In summary, the subsurface conditions encountered in the bores generally comprised fill overlying
natural silty sand then sandy and silty clays which are further described below:
    Fill: Surficial silty sand fill underlain by silty and sandy clay fill was encountered to between
     1.0 m and 1.1 m depth in the bores.
    Silty Sand: Natural silty sand was encountered beneath the fill in Bores 1 and 3 and continued
     to between 1.25 m and 1.65 m depth. The fine to medium grained silty sand was grey in colour
     and contained some clay fines.
    Sandy and Silty Clays: Underlying the fill in Bores 2 and 4 and the silty sand in Bores 1 and 3,
     natural sandy and silty clays were encountered to the termination of the bores at 4.0 m depth.
     The clays initially were typically grey streaked brown/orange brown in colour, grading to a grey
     mottled red-brown colour with depth.

No groundwater seepage was encountered in the bores at the time of investigation. It should be noted,
however, that groundwater depths and ground moisture conditions are affected by climatic conditions
and soil permeability, and will therefore vary with time.




Acid Sulfate Soils Investigation, Proposed Medical Centre                            94967.00.R.001.docx
36 & 40 Hofmann Drive, Noosaville                                                              May 2019