Reference Document - Geotechnical Investigation Report - DBW24/0090 & RAP24/0025

                Rebecca Stead                                                                                    20248-001-Rev0
                                                                                                               3 September 2020

                Materials encountered in the boreholes were consistent with the published geology, comprising dune sands.
                Subsurface conditions are summarised as follows:
                          Very loose to loose sands (silty/poorly graded) from the ground surface to depths between 1.4 m and
                           1.6 m BGL; then
                          Medium dense, poorly graded sand to the borehole termination depths.

                It should be noted that DCP testing extended below the borehole termination depth,s and indicates that the
                sands become dense (or denser) below about 3 m to 3.5 m BGL.

                Groundwater seepage was not encountered during the investigation, with the soils generally being moist.
                Reports of boreholes are attached to this letter, along with explanatory notes.

                2.2       Topography
                As illustrated in Text Figure 4, the site is located on the upper, eastern flank of a large sand dune traced by
                Attunga Heights. The subject site is located just off the dune crest, with the existing residence situated on
                relatively level ground presumably constructed by cut and fill earthworks.
                The natural surface profile has been interrupted by historic landscaping and residential construction at the
                site; with surrounding ground slopes to the east and south of the residence measured at the time of our
                assessment between about 10° and 12°. Steeper ground slopes ranging between about 20° and 22° were
                recorded to the north and north-east of the existing residence, with these gradients continuing down the flank
                of the sand dune beyond the property boundary. Based on our observations, the proposed extension areas
                are to be situated on moderately sloping ground to the western and eastern sides of the existing residence.




                                                                               Subject Site




                Text Figure 4: Ground surface contours, 1 m spacing (courtesy NC interactive mapping)

                Site conditions at the time of our investigation are shown in Text Figures 5 and 6 overleaf.




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Document Set ID: 23080488
Version: 1, Version Date: 27/06/2024