Landslide Hazard Report_compressed

Specialists in transport geotechnics

6 CONSTRAINTS/ PRECAUTIONS/ RECOMMENDATIONS

6.1 General
Good hillside engineering construction practice is considered mandatory during development of
the site. The notes and illustrations attached in Appendix 3 of this report outline some typical
hillside construction guidelines including, earthworks, erosion control and drainage practices for
hillside areas, which should be applied to this site.

6.2 Foundations
It is recommended that the foundations for the shed be designed and constructed in accordance
with AS2870 Residential Slabs and Footings. As a minimum, piers should extend to found at
depth in the underlying hard residual soil strata (1.5m into clays, or 0.5m into weathered rock if
encountered).

6.3 Drainage
The control of drainage is important to the stability of the proposed development. The following
recommendations are made with respect to drainage for the site:
   •    Well designed and engineered surface water controls should be used to reduce the
        infiltration potential of the site during and following rainfall. Surface water from the site and
        from areas upslope of the site must be diverted away from footing systems, cut and fill
        batters and retaining walls. The use of appropriate self-flushing spoon drains is
        recommended.
   •    Subsurface drainage must be installed behind retaining walls in order to prevent the
        development of hydrostatic pressure. This normally comprises slotted ‘aggi’ pipe wrapped
        in filter ‘sock’ and placed in gravel backfill.
   •    Discharge from rainwater tanks, roof water and runoff collection systems must be
        controlled and discharged as diffuse flow at least 10 metres down slope of any footing,
        batter or retaining structure.
   •    Any water disposal must be controlled and discharged as diffuse flow at least 10 metres
        down slope of any footing, batter or retaining wall.
   •    All excess stormwater collected from proposed pavements (driveways/road) and around
        the proposed shed (including overflow from rainwater tanks) must be directed by pipes or
        lined channels to the legal point of downstream discharge.

6.4 Earthworks
The following recommendations are made for earthworks on the site:
    •   Vegetation acts to reinforce and protect the soil profile on a sloping site. Therefore,
        vegetation clearance should be kept to the minimum necessary to undertake the works
        and should be limited to the immediate vicinity of the building envelope and works area.
    •   Earthworks on the site should be minimised as far as possible.
    •   Any fill should be placed under a Level 1 Inspection and Testing regime in accordance
        with the requirements of AS3798-2007 “Guidelines on Earthworks for Commercial and




10 May 2022                        CGC-SR-2022-011-R01-Rev01                                   Page 14