MCU25 0087 - Reference Document - Geotech assessment report (As Published) · MCU25/0087

        Ultimately, the advice of a specialist piling contractor should be sought regarding pile design and
        construction. However, where steel screw piles are adopted site specific load testing and the results of
        this geotechnical investigation should be considered by the structural engineers in validating any generic
        torque to capacity ratios provided as part of the proposed design. An assessment of potential vibration
        effects on nearby structures and monitoring requirements should also be included.
        Footing design should also account for potential soil reactivity to be equivalent to Class M.
        All footings should found such that they are not adversely affected by any adjacent excavations, trenches,
        retaining walls, or in ground structures that are not designed to support building loads. Footings should
        found at least below a plane extending 1 m horizontally from the base of
        trenches/excavations/swimming pool, then rising up at 1V:1H, as illustrated in Text Figure 11.
        Where consideration is given to the use of high level footings to the western side of the residence,
        structural designers should allow for the deepest founding depth of either:
             Founding footings below the zone of active earth pressure (within this zone reduced foundation
              capacity and adverse interaction with the seaward retention system are anticipated); or
             The arrangement should comply with Text Figure 11, with the relevant plane taken from the
              equivalent ground level at the front of the exposed piled wall following the most onerous erosion
              Case 2 in the stability modelling (Ref. Section 5.2.1).




                    Text Figure 11: Zone of influence diagrams – footings to be founded below these lines

        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.


        6.3             Temporary and Permanent Retention
        Excavations are expected to range up to around 4 m BGL (existing ground levels) and, given that the
        planned excavation extends close to some of the site boundaries and underground infrastructure (e.g.
        underground services), some form of temporary shoring will likely be required.
        Based upon our experience with similar sites, we anticipate that temporary shoring may be achieved by
        use of sheet piles, however Unitywater and NC requirements for their infrastructure may restrict the use
        of sheet piles. Shoring of deeper cuts would likely require lateral restraint, and this is conventionally


        Geotechnical investigation
        19 November 2025 | 25289-001-Rev0                                                                         20
Document Set ID: 24631529
Version: 1, Version Date: 24/03/2026