220508.2 - Response to Information Request OPW

DME Projects Pty Ltd
P.O. Box 7481
Sippy Downs, QLD, 4556
Tel 0438 157 612
ABN 79 224 274 637

                        Response to Information Request (OPW23/0179) – 128 Gympie Tce Noosaville
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See below advice and image that has been provided by the preferred contractor, showing the extent
of each type of shoring construction; the referred attachment (paper from the Gold Coast
municipality) is included in this response.


        As per offer sent our intention is to use a CFA-piled secant-wall for your basement, except
        where it is proposed you utilise the existing retention wall done by the development to the
        ‘East’.

        For clarity CFA-piling (Continuous Flight Auger) is a system of pile installation that is vibration
        and collapse free due the immediate replacement of excavated soil with concrete, and has a
        very low noise level compared to alternate piling methods of vibration and driving.

        The secant description is the overlapping round piles ‘secanting’ one another as per the
        diagram below.

        The benefit of this system is in preventing running dry or wet sand from falling into the
        excavation, as is possible with the gaps that are left with Contiguous or soldier pile systems.

        This is sometimes only evident in rain events, or once the sand layers dry out after exposure
        to air.

        The layout of the proposal for this site is shown below in a 3D schematic to protect the
        neighbour to the ‘West’ and provide a safe working space for the developments construction.

        The existing sheets are shown in grey.

        For additional information:

        This technique is now the preferred system of most councils for basement related works in
        built up areas, as it is the least disturbance; vibration, risk of collapse and noise, in both
        saturated and dry soils.

        Concrete Piled walls are also less prone to movement and so less risk in terms of services
        below ground, where even small movement or loss of bedding material can affect
        infrastructure.

        We have attached a paper from the Gold Coast municipality highlighting their change in
        preference, for the reasons stated above.