Reference Document - MCU26 0001 & OPW26 0002 - AS PUBLISHED · MCU26/0001

        6.              Geotechnical Recommendations
        General recommendations to help maintain the stability of the site are given in the document Some
        Guidelines for Hillside Construction, which is attached.


        6.1             Development Limitations
        Should any revisions be made to the extent of the proposed development as described in Section 2,
        Tectonic must review these prior to construction to assess if there are any impacts on slope stability.
        To achieve a Low Risk of instability, the following is recommended:
             Unretained filling should be limited to no more than 1 m above the existing ground surface, unless
              assessed and approved by a geotechnical RPEQ.
             All footings must be founded below the zone of influence of the surrounding structures and
              infrastructure (including underground services).
             All retaining walls exceeding 1 m high and/or subject to surcharge loads must be RPEQ designed
              and certified, which must include an assessment of global and internal stability.
             Design and construction of footings shall be undertaken in accordance with Section 6.3.2.
             Formal drainage should be constructed to ensure all stormwater is directed away from the existing
              and proposed structures.


        6.2             Earthworks
        6.2.1           Site Preparation and Trafficability
        Following removal of the existing buildings and associated construction elements (e.g. footings, services,
        etc.), any tree stumps and large roots should be ‘grubbed out’. Any organic rich topsoil and uncontrolled
        fill should then be stripped and set aside. Based on the boreholes, topsoil stripping depths should
        generally range between 0.1 m and 0.2 m BGL, with uncontrolled fill encountered to depths 1.1 m BGL
        (existing ground levels) in borehole BH1. It is possible that deeper pockets of topsoil or uncontrolled fill
        may exist and deeper, localised grubbing out of tree roots may be required.
        Topsoil materials must not be used in structural fill; however, may be placed across landscaping areas.
        Unsuitable natural material such as any saturated, loose or soft materials encountered should also be
        removed during subgrade preparation for bulk earthworks.
        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.
        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 poor trafficability during placement of a minimum 150 mm thick granular
        working platform may be required on soil subgrades along haul roads and across laydown areas.


        Geotechnical Investigation
        30 January 2026 | 25408-001-Rev0                                                                           11
Document Set ID: 25158026
                  24528612
Version: 1,
         2, Version Date: 10/09/2026
                          13/02/2026