Geotech

                              PROPOSED UNIT DEVELOPMENT
                              27 BOTTLEBRUSH AVENUE, NOOSA HEADS

It should be noted that this modelling addresses the global stability of the proposed works; however, the
stability of the retaining walls (modelled as high strength structures along the northern side of the building)
must be addressed by others as part of detailed design.




                                                        T
                            AF
Text Figure 9: Slope/W output for long term conditions



6.0      GEOTECHNICAL RECOMMENDATIONS
       R
General recommendations to help maintain the stability of the site are given in the document Some
Guidelines for Hillside Construction, which is attached.

6.1       Additional Investigation
Due to inaccessibility at the time of investigation, a deeper borehole may be required in the north-eastern
D

corner of the site depending on the chosen temporary retention system. Should a cantilevered temporary
retention system be adopted, the required ‘toe in’ depth beneath the proposed excavation level may be
relatively deep (e.g. in excess of 10 m). As the current investigation in this area was limited to handheld
equipment, the subsurface conditions below about 3 m BGL are somewhat unknown. Previous experience
in the greater Noosa area indicates that relatively high strength weathered rock of the Noosa Quartz Diorite
formation underlies the ancient dune at depth, which could pose a risk to the constructability of the chosen
temporary retention system. The deeper borehole should be drilled at least to the depth of the proposed
temporary retention system ‘toe in’ to confirm the deeper subsurface conditions. Tectonic could provide a
quote for the deeper investigation, following confirmation of the temporary retention system and removal of
the existing residence.

6.2       Development Limitations
It is anticipated earthworks will include cuts for the lower level of up to about 6 m deep to the rear,
daylighting to the front. Localised filling less than 0.5 m high is anticipated to form finished surface levels.
Should proposed cuts/fills exceed these quantities, Tectonic must assess the impacts on slope stability
before construction.



10 November 2021
Report No. 21286-001-Rev0                                9