geotech report · MCU15/0087

Slope Stability and Geotechnical Assessment
1 Natasha Avenue, Noosa Heads




        Access to the dune escarpment should be limited and restricted to established pathways
         suitably protected from erosion.

        Short term or long term loads should not be placed on or near the top of the escarpment.

        Any retaining structure greater than 0.6 metres in height should be designed and certified by
         a professional engineer in accordance with the requirements of AS4678-2002: Earth
         Retaining Structures. The engineer designing the retaining wall should treat the retained soils
         as saturated.

        Earthworks on the site be undertaken in accordance with the requirements of AS3798-2007
         “Guidelines on earthworks for commercial and residential developments”. In particular, the
         subgrade under the fill must be cut into a series of horizontal benches prior to fill placement.

        All roof water and concentrated water runoff should be direct into the stormwater system.
         Roof water may also be retained by storage tanks (rainwater tanks) however the tank
         overflow must be redirected into the stormwater. Coffey recommend that overflow lines have
         twice capacity of all inflow lines to ensure the tanks do not overtop and saturate the soils near
         the structure or tanks.

        Any tanks should be located away from the escarpment.

        Control of surface water flows is important for slope stability control. We recommend the use
         of well designed and engineered surface water controls that would aim to divert runoff away
         from the escarpment, retaining walls and footings. The use of self-flushing spoon drains or
         diversion bunds is recommended. All runoff should be diverted to the street or stormwater
         system on the site

        Any swimming pool overflow should be controlled and diverted to the stormwater system.

        All stormwater systems including guttering, down pipes and overflows must be regularly
         maintained.

        All household waste water must be directed to the sewer system.

        We recommend the observation and adherence to Good Hillside Practice as published by the
         Australian Geomechanics Society in 2007 along with Australian Geoguides attached in
         Appendix E.

7.7.2.       Footing Systems
Footing systems should be designed in accordance with the following recommendations.

        As far as feasible, any section of the house or pool which is located over the escarpment
         should be cantilevered from footings constructed at the top of the escarpment.

        A piled footing system is recommended for the structure. Due to the risks associated with
         vibrations, a bored pile system is recommended. Screw piers could also be considered.

        A minimum embedment of 8 metres is recommended for piles located on the escarpment
         slope or within 3 metres of the top of the escarpment.

        A minimum embedment of 5 metres is recommended for piles within 8 metres of the top of the
         escarpment.

        A minimum embedment of 1.5 metres is recommended for piles more than 8 metres from the
         top of the escarpment.


Coffey
GEOTKPAR02068AA/A                                                                                           9
12 August 2015