Appendix G - Slope Stability Certification Report · MCU25/0022

  8        GEOTECHNICAL CONSTRAINTS TO DEVELOPMENT
  The following comments apply to construction on all the site.

  Slope Stability
  The site shows no signs of slope instability and will be cut into rock; however the new slope
  will be considerably steeper than the existing and could be considered medium risk until the
  retaining wall is constructed; once the wall has been constructed the slope can be considered
  low risk; however, the development should not amend or alter other slopes without specific
  geotechnical advice.
  The following recommendations shall be adhered to:
       •    Any site earthworks carried out must comply with A.S. 3798, “Guidelines on
            Earthworks for Commercial and Residential Development”.
       •    Any soil fill should be placed and compacted to “Level 1 Requirements” set out in
            A.S.3798. to comply with Controlled Fill as stated in A.S.2870, “Residential Slabs
            and Footings”.
       •    Excavate all of the clay above the rock in the platform area.
       •    Provide a drainage diversion to the crest of the slope to direct surface water away
            from the crest of the cutting.
       •    Ensure that all of the site is level.
       •    Place fill which is at least CBR 15 or above with less than 15% passing the .075mm
            sieve.
       •    Direct all water away from the site with surface drains.
       •    Dams, ponds, swimming pools, or any auxiliary services such as soakaways or septic
            tanks plants are to be placed away from the site but not below it by at least 50m.
       •    Any fill material encountered shall be excavated and re-used if suitable and if
            unsuitable either modified to be suitable, removed from site or used as landscape fill.
       •    Cut and fill areas may be battered at an angle of up to 1V to 3H or shall be retained
            using engineer approved retaining methods. Steeper slopes may be achievable with
            specific geotechnical advice. Prior to filling any topsoil, grass, roots or other organic
            matter shall be removed from the construction area.
       •    Slopes steeper than 1V to 7H shall be benched to avoid introducing preferential
            failure surfaces.

  Surface Drainage
  All structure roof drainage shall be collected and piped to approved legal points of stormwater
  discharge.
  The ground surrounding the structure shall be shaped so that surface runoff flows away from
  all structures. Drainage should be provided to minimise variations in moisture content in soils
  surrounding and below sites and prevent concentrated run‐off causing erosion.
  During construction, measures will be required to prevent erosion, undercutting and over
  saturating soil areas that may lead to slope instability. The basic principles of managing
  stormwater on any development site are:

193 Sankeys Rd Slope Stability Certification
                                                                                        July 2023
                                                    10