Compiled Reference Documents - MCU24/0153 & OPW24/0202

        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
        It is anticipated earthworks may include cuts for the basement level of up to about 7 m deep with only
        minor filling expected to be required up to about 1 m in height to form finished surface levels. Should
        proposed cuts/fills exceed this quantity, Tectonic must assess the impacts on slope stability before
        construction.


        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 site observations and boreholes, topsoil (where
        present) stripping depths should generally range between 0.1 m and 0.2 m BGL, with uncontrolled fill
        encountered to depths of between 0.4 m to 0.6 m BGL. It is noted that deeper pockets of topsoil or
        uncontrolled fill may exist and deeper, localised grubbing out of tree roots may be required.
        Rubbish was noted during soil testing by ASI at a depth of 0.7 m BGL. Three boreholes (designated BH2,
        BH2A and BH2B) were drilled by Tectonic in this area to delineate the extent of this rubbish, however, no
        deleterious material was encountered at those locations. It would be prudent to allow to investigate this
        area further by excavation of test pits prior to construction commencing to assess if rubbish is present
        and to what extent.
        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.
        Specific platform design would be required prior to mobilisation and trafficking of any heavy mobile
        plant on the site (e.g. cranes, concrete pumps or piling rigs).




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