SUPERSEDED Compiled Reference Document - MCU24 0153 & OPW24 0202 (As Published)

        Executive Summary
        This report details the results of a geotechnical investigation undertaken for a proposed unit
        development at 51 Elanda Street, Sunshine Beach. The investigation comprised drilling of boreholes at
        four locations across accessible areas of the development footprint. This report summarises the results
        of the investigation and provides geotechnical recommendations regarding earthworks and footings,
        together with temporary and permanent basement retention.
        Architectural design drawings provided indicate that the development will comprise a three-storey
        building, over a single level basement carpark. Excavations will be in the order of up to 7 m deep and
        localised filling less than 1 m high is anticipated. Excavations are expected to extend close to the site
        boundaries and therefore, some form of temporary retention will be required.
        The subsurface conditions encountered in the boreholes are summarised as follows:
        ▪     Topsoil – comprising loose silty sand to depths of 0.1 m to 0.2 m below ground level (BGL); then
        ▪     Fill – comprising loose silty sand to depths of between 0.4 m and 1.3 m BGL; then
        ▪     Natural Sands – comprising poorly graded sands mostly being loose to depths of between 1.4 m
              and 2.6 m BGL; then becoming medium dense and increasing to dense below depths of about
              2.8 to 3.8 m BGL.
        No signs of groundwater seepage (‘springs’) were observed during our walk-over. Groundwater was not
        encountered in the boreholes at the time of investigation.
        Provided the recommendations within this report are adhered to, and subject to detailed design and
        construction of the footing and retention system by a suitably qualified and experienced RPEQ structural
        engineer, there should be a Low Risk to property from slope instability.
        Excavations through the existing soils should be achievable using conventional earthmoving plant (e.g.
        small or larger excavators with toothed buckets). Temporary unsurcharged cuts could be formed at
        1V:2H in the very loose to loose sands, and at 1V:1H in medium dense (or denser) sand, for batters up to
        3 m in height, provided groundwater seepage is not encountered and sands do not slough from the
        batter face as they dry out. It is expected that space restrictions will limit battering of temporary cuts on
        the site and so some form of temporary retention system, such as sheet piles or contiguous reinforced
        concrete piles, will be required. These retention systems, which may have to be temporarily braced during
        construction, may also be designed to form the permanent basement walls.
        Footings for the proposed development and any ancillary structures (e.g. retaining walls) must penetrate
        through any fill materials and unsuitable natural soils (i.e. very loose to loose sands) to found at least
        0.5 m into medium dense (or denser) natural sands. Such materials were encountered in the boreholes
        below depths of between about 1.4 m and 2.6 m BGL (existing ground levels). High-level footings would
        be suitable in excavation areas where medium dense (or denser) natural sands are exposed at the
        subgrade level. Piled footings would be required unless excavations expose such materials at or near
        foundation subgrade level. Given the sandy soil profile, where deepened footings are required, steel
        screw piles are considered to be a suitable foundation type. Due to the presence of loose sands,
        together with the close proximity of adjacent buildings, open bored piers or driven piles are not
        considered to be suitable for this site. Cast in place continuous flight auger (CFA) piles may also be
        suitable for both foundation and shoring piles provided a small rig capable of traversing the site can be
        sourced.




        Proposed Unit Development
        30 September 2024 | 24265-001-Rev0                                                                          iii
Document Set ID: 23376055
Version: 1, Version Date: 28/11/2024