25289-001-Rev0 - The Esplanade (1)-compressed

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