ECM_22343520_v1_Geotechnical Investigation · 132000.200173.1

                                          PROPOSED RENOVATIONS
                                          2 ARAKOON CRESCENT, SUNSHINE BEACH

            6.0        GEOTECHNICAL RECOMMENDATIONS
            6.1        Earthworks
            Excavations for the lower level and new garage are anticipated to range up to about 2 m deep. Isolated
            relatively deep excavations may be required for underground services and footings or other specific
            elements. Filling less than 1 m high is anticipated to form final levels, with filling to the east of the residence
            limited to landscaping only, which should not exceed 0.5 m high.
            The advice give herein should be treated as preliminary to aid in project planning, and Tectonic must review
            detailed design drawings for the residence prior to construction.

            6.1.1         Site Preparation and Trafficability
            Following clearing of existing vegetation, any tree stumps and large roots should be ‘grubbed out’. Any
            organic rich topsoil or uncontrolled fill should then be stripped away from at grade or building subgrades and
            set aside. Similarly, all footings and remaining structural elements from the existing residence should be
            removed and ‘grubbed out.’ Based on the ASI boreholes and site observations, stripping depths to remove
            existing unsuitable upper soils should be relatively shallow however, deeper areas of unsuitable materials
            may be present across the site, particularly related to the existing structures (e.g. retaining wall backfill,
            service trenches, footing excavations). Topsoil materials must not be used in structural fill; however, may be
            placed across landscaping areas.

            It should be noted that compaction of such relatively ‘clean’ sands as structural fill requires the addition of
            substantial volumes of water (‘flooding’) combined with the use of vibratory compaction equipment (typically
            a vibrating plate). Care must be taken with the use of vibratory equipment (e.g. compactors or sheet piling)
            to ensure that there are no adverse impacts on surrounding structures. The impacts from ground vibration
            must be closely monitored and managed during construction. It would be prudent to conduct a dilapidation
            survey of neighbouring structures prior to commencement of construction; and furthermore it is
            recommended that a suitably qualified and experienced civil/structural RPEQ is engaged to provide a
            vibration management plan for the proposed construction works. Our preliminary recommendation would be
            that allowance is made for equipment and works such that the peak particle velocity does not exceed
            10 mm/s, where measured at the property boundary.

            The exposed natural subgrade following excavations will likely be in a loose condition and must be
            compacted by several passes of a vibrating plate or minimum 4 tonne vibrating smooth drum roller, in
            conjunction with surface application of ample water, to achieve the required compaction.
            Due to the potential for development of poor trafficability during construction, placement of a minimum
            150 mm thick granular working platform may be required across laydown areas. Specific platform design
            would be required prior to mobilisation and trafficking of any heavy mobile plant on the site (e.g. mobile
            cranes, concrete pumps or piling rigs).

            Due to the highly permeable nature of the sands at this site, stormwater is expected to rapidly infiltrate the
            ground, making un-sealed surface drainage ineffective for the control of flows. Any sealed areas should be
            graded to ensure free drainage of stormwater away from construction areas, and to a control point(s).

            6.1.2         Excavations
            Excavations through the soils should be achievable using conventional earthmoving plant (e.g. small or
            larger excavators with toothed buckets). Temporary unsurchaged cuts in the very loose to loose sand could
            be formed at 1V:2H, and at 1V:1.5H in medium dense (or denser) sand, for batters up to 3 m in height. Flatter
            batters or temporary retention may be required if groundwater seepage is encountered or if sloughing of dry
            sand occurs at the batter surface. Deeper cuts, if required, will require temporary shoring, unless assessed
            and approved by Tectonic during construction.

            Permanent cuts or fills greater than 1 m must be retained. Permanent cut and fill batters up to 1 m high shall
            not exceed 1V:2.5H. Any permanent soil and fill batters will require erosion protection (e.g. revegetation or
            surface protection). Similarly, improvements to the vegetation (i.e. with endemic native species) on the
            natural high dune face downslope of the residence would aid in restricting the development initial surficial
            failures.


             24 February 2023
             Report No. 22484-001-Rev0                               14
Document Set ID: 22343520
Version: 1, Version Date: 16/03/2023