J001783-001-R-Rev1

Ashley and Caroline Hermes


7.0      DEVELOPMENT IMPACTS & MITIGATION MEASURES
It is our opinion that this site is suitable for the proposed development, from a geotechnical viewpoint, subject
to implementation of the recommendations provided in this report. The potential impacts on slope stability of
the proposed development have been considered, and the measures recommended below have been
designed to mitigate those impacts. Building development should follow normal slope maintenance
procedures and the document ‘General Guidelines for Hillside Construction’, which is attached in
Appendix C.

  7.1 Earthworks
Earthworks should be carried out in accordance with Australian Standard AS 3798-2007 Guidelines on
earthworks for commercial and residential developments.

7.1.1 Site Preparation & Trafficability
Site preparation in building and pavement areas should include the following:

 Strip the surface of vegetation, organic matter, organic rich soils (topsoils) and severely root affected
      soils.

 ‘Proof roll’ the stripped surface by several passes of a minimum 8 tonne roller to identify loose or soft
      areas.
Loose/soft areas identified by proof rolling and/or inspection will require treatment by either of the following
methods:

     Over-excavation and replacement with suitable fill compacted in layers (refer Section 7.1.4); or
     Re-compaction of the loose or soft material provided that it does not contain substantial organic
         matter or deleterious substances.
At the time of the investigation the site was trafficable in a 4WD vehicle. However, following stripping of
topsoil materials, trafficability issues should be anticipated following rainfall. Due to the potential for poor
trafficability, it would be prudent to allow for the placement of a compacted granular fill layer particularly in
access road and laydown areas. A geotextile separation layer between the natural ground and granular fill
may also be required.
Site drainage should also be implemented during construction to prevent saturation of subgrade soils and
batters, with erosion protection provided.

7.1.2 Excavatibility
Excavations into the colluvium, residual soil, or extremely weathered material should be achievable using
conventional small to large earthmoving equipment (i.e. 6 to 20 tonne excavators). Ripper attachments
and/or hydraulic breakers may be required in medium strength (or stronger) mudstone or excavations
beyond the test pit termination depths.

7.1.3 Re-use as Fill
Fill won from excavations on the site may be suitable for reuse as structural fill, provided that oversize
material is removed (e.g. cobbles/boulders in colluvium). The residual/colluvial clays may also be difficult to
handle or compact when wet, and will require careful moisture conditioning. Due to the proposed volume of
fill and the aforementioned issues, it may necessary to replace some/all excavation spoil with suitable
imported fill.
Any organic rich topsoil must not be used as fill to support structural loads, however it may be used in
landscaping areas.




J001783-001-R-Rev1