SUPERSEDED Compiled Reference Document - MCU24 0153 & OPW24 0202 (As Published)

                                       Text Figure 9: Footing depth required to prevent undermining

        Site drainage should be designed to readily remove surface water and to prevent ponding of water on
        subgrade areas during construction and also adjacent to foundations and perimeter slabs once
        construction is completed. It is recommended that footings be inspected by a suitably qualified and
        experienced engineer prior to placement of steel reinforcement and pouring of concrete to confirm
        allowable bearing pressures and cleanliness of excavations.
        If any soil conditions encountered during construction are found to differ from those noted in the
        geotechnical investigation, Tectonic should be notified immediately and an inspection carried out to
        determine if changes to footing design are required.


        6.4             Temporary and Permanent Retention
        Excavations for the basement level may extend to depths of around 7 m BGL (existing ground levels) and
        the basement footprint will extend close to some of the site boundaries, so some form of temporary
        shoring will be required to support the basement excavation.
        Based upon our experience with similar sites, we anticipate that temporary shoring may be achieved by
        use of reinforced concrete contiguous pile wall. Sheet piling is not considered suitable for this site due
        to the depth of the excavation, the risk of consolidation of loose sands from vibratory effects and the
        potential for lateral movements to result in distress to existing structures or underground services behind
        the boundary walls. An alternative a secant pile wall configuration could be considered along with
        propping of the shoring wall with the use of internal struts. The temporary wall can also act as the
        permanent basement wall if appropriately designed.
        Installation of such piles in this setting would require the use of cast in place CFA piles. We understand
        that the client has been in consultation with a specialist contractor who has a small specialised rig that
        would be capable of installing such piles on this terrain. The advice of a specialist shoring contractor
        must be sought regarding feasibility, design and installation of the proposed retention and subsurface
        drainage system. It will be necessary to conduct numerical analysis to optimise the retention system.


        Proposed Unit Development
        30 September 2024 | 24265-001-Rev0                                                                           15
Document Set ID: 23376055
Version: 1, Version Date: 28/11/2024