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

        Table 2: Stability Risk Levels
            Risk Level            Example Implications(1)

            VH     Very High      Unacceptable without treatment. Extensive detailed investigation and research, planning and
                   Risk           implementation of treatment options essential to reduce risk to Low; may be too expensive and not
                                  practical. Work likely to cost more than value of property.

            H      High Risk      Unacceptable without treatment. Detailed investigation, planning and implementation of treatment
                                  options required to reduce risk to Low. Work would cost a substantial sum in relation to the value of
                                  the property.

            M      Moderate       May be tolerated in certain circumstances (subject to regulators’ approval) but requires investigation,
                   Risk           planning and implementation of treatment options to reduce risk to Low. Treatment options to reduce
                                  to Low risk should be implemented as soon as practicable.

            L      Low Risk       Usually acceptable to regulators. Where treatment has been required to reduce the risk to this level,
                                  ongoing maintenance required.

            VL     Very Low       Acceptable. Manage by normal slope maintenance procedures.
                   Risk

        Note: (1) The implications for a particular situation are to be determined by all parties to the risk assessment and may depend
        on the nature of the property at risk; these are only given as a general guide.

        Given the geology and topography of this site, it is unlikely that a landslide could affect the proposed
        development area. Sand dune slopes are generally close to the ‘limit of equilibrium’ for slope stability
        where the surface gradient is about 30° (58%), although often lower (26˚ to 28˚) for very loose sands.
        Our measurements indicate that natural overall gradients ranged up to about 10°. The limit of
        equilibrium is the ‘tipping point’ to instability, where the factor of safety (FOS) of the slope is
        approximately 1.0. The FOS of a slope is the balance (ratio) between the forces driving instability (e.g.
        soil weight, groundwater pressure) and the resisting forces (e.g. soil friction and cohesion).
        Sand dune slopes generally remain stable (i.e. FOS greater than 1.0) when they are:
                well vegetated (mix of ground cover, shrubs and small trees);
                not subjected to concentrated stormwater flows;
                not surcharged with additional loads (e.g. fill); and
                not undercut by excavation or erosion.
        Where dunes are well vegetated, the plant roots can provide a surface reinforcing layer which may
        enable dunes to stand up relatively steeply, particularly when combined with soil suction. Direct
        discharge of stormwater onto dune slopes may cause channel erosion, undermining and disturbance of
        vegetation, and development of generally localised instability.
        The primary trigger for large-scale instability of sand dunes is when the toe of the dune is disturbed.
        This may be caused by excavations or natural erosion. The potential for significant erosion of the dune
        immediately down slope from the site is considered negligible, provided that future disturbances (e.g.
        excavations etc.) are managed with sufficient engineering consideration. Given the setback of the
        property from the coastline, the risk from erosion of the sand dune by coastal process leading to
        instability at the site is also assessed to be negligible.
        Considering the existing site conditions (Ref. Section 4), and subject to the implementation of
        recommendations given below, it is assessed that there should be a Low Risk of global slope instability
        affecting the proposed development. Regulators (NC) normally require that a Very Low or Low Risk of
        landslide affecting the property must be demonstrated to enable development approval. Summarised in



        Geotechnical Investigation
        30 January 2026 | 25408-001-Rev0                                                                                                    9
Document Set ID: 25158026
                  24528612
Version: 1,
         2, Version Date: 10/09/2026
                          13/02/2026