Attachment 5 - Slope Stability Assessment · RAL20/0005

Mr Peter Loxton                                                                                 16162-001-Rev0
                                                                                                   22 July 2016

4.4    Drainage
It is essential that finished gradients around the house are formed to ensure that natural runoff is directed
away from building walls and footings. Surface protection (e.g. proprietary matting in combination with
plantings, or rock ‘rip rap’) must also be placed to prevent erosion and undermining of any proposed
structures by possible stormwater flows.

Subsurface drainage must be installed behind retaining walls in order to prevent the development of
hydrostatic pressure (e.g. slotted ‘aggi’ pipe wrapped in filter ‘sock’ placed in gravel backfill).

All excess stormwater collected around the proposed residence (including overflow from rainwater tanks)
must be directed by pipes to the legal point of downstream discharge (presumably the existing watercourse).



5.0     SUMMARY & CONCLUSIONS
Based on the findings of our assessment we consider, from a geotechnical viewpoint, that the site is suitable
for the proposed addition and that there should be a Very Low Risk of slope instability. This advice is subject
to implementation of the recommendations given in this report.



6.0     LIMITATIONS
Your attention is drawn to the document Limitations, which is attached to this letter report.

Please contact the undersigned should you wish to discuss any of the above matters.

Yours faithfully

TECTONIC GEOTECHNICAL PTY LTD




Ashley Davey BEng (Geological) MIEAust RPEQ 8159
Director/Principal Geotechnical Engineer


Attachments: Qualitative Terminology for Use in Assessing Risk to Property
             Some Guidelines for Hillside Construction
             Limitations




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