4. 220148 - Slope Stability Report (2) · 132006.2554.01

Seachange Builders                                                                                         22134-001-Rev0
                                                                                                              26 April 2022

1.2       Method and Scope of Investigation
As part of our slope stability assessment, a desk-top study was carried out comprising a review of published
geological maps, slope stability studies and a site investigation report by CSI Soil Testing (CSI Ref. Job No.
14743, dated 3 March 2022).
A walk-over survey was conducted in order to make an appraisal of the general condition of the site in
regard to topography, drainage, vegetation cover, geology, erosion, and condition of existing structures.
The walk-over survey was carried out by an experienced geotechnical engineer from Tectonic on
8 April 2022. The results of the desk-top study and walk-over survey are included in Section 2 below.

1.3       Qualifications of Responsible Engineer
This report has been prepared by Mr Ashley Davey, an RPEQ with over 26 years of experience in
geotechnical engineering, including a number of slope stability projects on the Sunshine Coast.



2.0        DESCRIPTION OF EXISTING CONDITIONS
2.1       Geology and Subsurface Conditions
Available geological information 1 indicates that the site is underlain by Quaternary age dunes, mainly parabolic
comprising ‘quartz sand’.




                                                                                  Approx. Site Location




Text Figure 3: Extract of Gympie Special geology map

The CSI investigation comprised one borehole (designated BH1) at the rear of the existing residence
(proposed pool area). Dynamic cone penetrometer (DCP) testing was conducted adjacent to the
borehole and at one stand-alone location (designated DC1 and DC2, respectively). The borehole
intersected very loose natural silty sand to 0.6 m below ground level (BGL), then very loose to loose
natural sand to about 2 m BGL (borehole termination depth). Medium dense sands are then indicated by
DCP testing to extend to about 3 m BGL, thereafter becoming dense to at least 3.5 m BGL. Similar
variations in soil density were indicated at the location of DC2.

Groundwater was not mentioned in the CSI borehole report, with the soils described as ‘moist’.




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




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