Geotechnical Report (1) · MCU21/0212

                                   PROPOSED RESIDENCE
                                   66 SEAVIEW TERRACE, SUNSHINE BEACH

4.3          Geology
Available geological information 1 indicates that the site is underlain by Pleistocene age quartz dune sand
(Ref. extract of published mapping in Text Figure 10 below). The headlands to the north/north-east of the site
are indicated to consist of materials derived of the Tiaro Coal Measures, a late Triassic to Jurassic age
sedimentary deposit. These materials are expected to underly the dune sands proximal to the site.




                                                                     Approx. site location




Text Figure 10: Extract of Gympie Special 1:100,000 Geology Map

4.4          Subsurface Conditions
Detailed descriptions of the subsurface conditions encountered in the boreholes are provided in the
borehole reports attached in Appendix A, along with definition sheets which describe terms and
abbreviations used on the reports. Subsurface conditions encountered in the boreholes are summarised as
below and are illustrated as a cross-section in Figure 2 (attached at end of text).
Borehole BH3 was drilled within the proposed building envelope using a rotary drill rig and encountered:

           Natural Sands – comprising loose, dry to moist, fine to medium grained sands to 1.25 m BGL;
            then becoming medium dense to 4.2 m BGL; followed by
           Interlayered Indurated Sand & Sands – comprising dense materials to 9.3 m BGL, then
            becoming very dense 29.6 m BGL; and consisting of sands, occasionally being weakly cemented
            indurated sand (‘coffee rock’); underlain by
           Residual Soils and Extremely Weathered (XW) Material – comprising, hard, medium to high
            plasticity, sandy clays to the borehole termination depth of 31.45 m BGL.

Boreholes BH1 and BH2 were drilled using hand augering equipment at the eastern edge of the
development area, and at the toe of the dune, respectively. DCP4 was undertaken around the centre of the
main high dune face. These locations encountered/indicated a similar subsurface profile as follows:

           Natural Sands – comprising loose sand (occasionally silty) to between 1.1 m and 1.6 m BGL, then
            becoming medium dense to depths of between 2.3 m and 4.8 m BGL, and dense thereafter to the
            maximum depth of investigation (Ref. attached borehole logs and in situ test results). Borehole
            BH2 at the toe of the high dune encountered the deepest depth to dense (or denser) materials.


1
    Queensland Government, Department of Mines and Energy, 1:100,000 Gympie Special Geology Map, Sheet 9445 & Part 9545, 1999


23 November 2021
Report No. 21370-001-Rev0                                       8