Reference document Geotech Investigation · MCU22/0087.01

                                            PROPOSED UNIT DEVELOPMENT
                                            37 BOTTLEBRUSH AVENUE, NOOSA HEADS

            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/retaining
            walls/swimming pool, then rising up at 1V:1H, as illustrated in Text Figure 10.




                                       Text Figure 10: 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 4 m BGL (existing ground levels) and, it
            is likely that the basement footprint will extend close to some of the site boundaries, so some form of
            temporary shoring may 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 sheet piles. Such shoring techniques would likely require lateral restraint, and this is conventionally
            achieved by anchoring. However, the proximity to neighbouring properties would require a number of
            permissions to be obtained for subterranean access. Therefore, it is suggested that internal struts/propping
            be considered to provide lateral restraint for the shoring system.

            Anchored or propped sheet pile would likely require pre-drilling to prevent adverse vibrations during sheet
            pile installation. Temporary lateral support can be provided by installation of helical steel anchors (similar to
            screw piles) or internal props/struts connected to walers. As a permanent basement wall is constructed
            inside the temporary structure, the sheet pile wall becomes sacrificial.

            Other shoring methods that could be considered include contiguous or non-contiguous piles and secant
            piles. 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. Detailed design will also need to account for relevant
            factors of safety to maintain the temporary and long-term stability of the retention system.




             13 May 2022
             Report No. 22151-001-Rev0                              13
Document Set ID: 22198682
Version: 1, Version Date: 05/12/2022