slope stability

Integra Partnerships                                                                             22340-001-Rev0
                                                                                              14 September 2022

3.6    Drainage
Given the sandy nature of the site, rainfall is generally expected to rapidly infiltrate any unsealed surfaces. If
necessary, diversion drainage should be constructed to divert seepage and/or runoff away from the building
pad areas and batter slopes to prevent saturation and erosion.
Permanent site drainage must be installed to ensure that stormwater runoff is directed away from proposed
building walls, footings and retaining walls (e.g. positive gradients and/or channel drains). Future building
and landscaping must be carried out to maintain good drainage. Surface diversion drainage should be
constructed above the crest of any new cut or fill embankments (e.g. grassed or landscaped swales or
diversion mounds).

Although unlikely, if groundwater seepage is encountered during excavations, Tectonic must be notified to
assess the impact on stability.

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.
All excess stormwater collected around the buildings (including overflow from rainwater tanks, pool etc.)
must be directed by pipes or lined channels to discharge into the existing stormwater infrastructure along
Wyandra Street.

Subsurface disposal of stormwater, such as by an infiltration pit, must not be undertaken.



4.0     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




Jarrad McVey BEng (Civil) MIEAust                           Ashley Davey BEng (Geological) RPEQ 8159
Geotechnical Engineer                                       Principal Geotechnical Engineer


Attachments: Figure 1 – Site Plan
             Borehole Reports and Explanatory Notes
             Limitations




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