Geotech

                             PROPOSED UNIT DEVELOPMENT
                             27 BOTTLEBRUSH AVENUE, NOOSA HEADS

Retaining structures must be founded as per the recommendations in Section 6.4.2 above with the footings
also designed to account for lateral loads imposed by the retaining wall. Detailed design must include an
assessment of internal and global stability. A solution using screw piles to support retaining walls, possibly
including raked piles, may be feasible although bending and shear capacities would need to be carefully
checked in design from a soil-structure interaction viewpoint. Additional lateral capacity may be achieved by
incorporating a deeper pile cap that also acts as a shear key attracting passive resistance from the sands in
front of the wall.

6.6      Drainage
Surface diversion drainage should be constructed above the crest of any new cut or fill embankment or
retaining walls (e.g. grassed or landscaped swales or diversion mounds). Adequate site drainage must be
installed to ensure that stormwater runoff is directed away from building walls, footings, batters and retaining
walls.
Although unlikely, if groundwater seepage is encountered during excavations, Tectonic must be notified to
assess the impact on stability.




                                                      T
Subsurface drainage must be installed behind any retaining walls (e.g. slotted ‘aggi’ pipe wrapped in filter
‘sock’ placed in gravel backfill). Depending on matters such as the extent of drainage installed and site-
specific groundwater conditions, the designer must make an assessment of hydrostatic pressure to be
accounted for in the design of the retaining structure. It is assumed that any pool floors will include a
hydrostatic pressure relief valve. The outlet pipe from this valve must be taken to ‘daylight’ at the ground
surface.
                            AF
All excess stormwater collected around the residence (including overflow from rainwater tanks etc.) must be
directed by pipes or lined channels to discharge into the existing stormwater infrastructure along Bottlebrush
Avenue. Subsurface disposal of stormwater must not be undertaken.



7.0      SUMMARY & CONCLUSIONS
Based on the findings of our assessment it is assessed that there would be a Low Risk of slope instability
affecting the proposed development subject to implementation of the recommendations given in this report.
       R
8.0      LIMITATIONS
Your attention is drawn to the document Limitations, which is included in Appendix C of this report. The
statements presented in this document are intended to advise you of what your realistic expectations of this
report should be, and to present you with recommendations on how to minimise the risks associated with the
D

services provided by Tectonic for this project.




10 November 2021
Report No. 21286-001-Rev0                              14