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Assessment of development impacts and treatment of the cut and filled areas.

Where the site is to be located, the site is near level and there is a cut batter to the west of
the proposed construction site, facing uphill. The are immediately downhill form the
proposed siter is near level.

The construction site is to have a spoon drain or diversion mound on the high side of the
house area to divert water away from the proposed dwelling.

Given the treatment of this site to be as recommended above - he overall effect of the
development on site stability is negligible .

Measures recommended to mitigate impacts

The measures to mitigate the impacts of the proposed dwelling are the diversion of water
away from the cut area using a spoon drain and or mound and the limiting of the fill batter
and fill batter slope.

No additional measures are required to mitigate impacts of the proposed construction on
the site.

Summary and Conclusions

Below is a chart of landslip risk by The Australian Geomechanical Society,
“Landslip Risk Management Concepts and Guidelines" published by The Australian
Geomechanical Society. Australian Geomechanics Society. Australian Geomechanics
Society.

                        TABLE 1 – RISK LEVEL IMPLICATIONS

Risk Levels.
VH                  VERY HIGH RISK                      Extensive detailed investigation and
                                                        research, planning and implementation
                                                        of treatment options essential to reduce
                                                        risk to acceptable levels – may be to
                                                        expensive and impractical.
H                   HIGH RISK                           Detailed investigation, planning and
                                                        implementation of treatment options
                                                        required to reduce risk to acceptable
                                                        levels
M                   MODERATE RISK                       Tolerable provided treatment plan is
                                                        implemented to maintain or reduce risks.
                                                        May be accepted.
L                   LOW RISK                            Usually accepted. Treatment
                                                        requirements and responsibility to be
                                                        defined to maintain or reduce risk.

VL                  VERY LOW RISK                       Acceptable. Manage by normal slope
                                                        maintenance procedures.




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No evidence of previous movement, seepage o r soil creep was observed in the areas.

It is our opinion that provided the site is managed & maintained in an orderly manner with
respect to surface runoff; the risk of slope instability will not increase from a “low risk”.

The following drawings by the Australian Geomechanics Society are attached to assist in
showing good hill side management.

Please find additional notes pages 174 and 175 of AUSTRALIAN GEOGUIDE LR8
(CONSTRUCTION PRACTICE by the Australian Geomechanics Society.




                                   BE Civil RPEQ
For and on behalf of Sunrise Design Qld Pty Ltd.




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                 AUSTRALIAN GEOGUIDE LR8 (CONSTRUCTION PRACTICE)
HILLSIDE CONSTRUCTION PRACTICE
Sensible development practices are required when building on hillsides, particularly if the hillside has more than a low
risk of instability (GeoGuide LR7). Only building techniques intended to maintain, or reduce, the overall level of landslide
risk should be considered. Examples of good hillside construction practice are illustrated below.




WHY ARE THESE PRACTICES GOOD?
Roadways and parking areas - are paved and incorporate kerbs which prevent water discharging straight into the
hillside (GeoGuide LR5).
Cuttings - are supported by retaining walls (GeoGuide LR6).
Retaining walls - are engineer designed to withstand the lateral earth pressures and surcharges expected, and include
drains to prevent water pressures developing in the backfill. Where the ground slopes steeply down towards the high
side of a retaining wall, the disturbing force (see GeoGuide LR6) can be two or more times that in level ground.
Retaining walls must be designed taking these forces into account.
Sewage - whether treated or not is either taken away in pipes or contained in properly founded tanks so it cannot soak
into the ground.
Surface water - from roofs and other hard surfaces is piped away to a suitable discharge point rather than being allowed
to infiltrate into the ground. Preferably, the discharge point will be in a natural creek where ground water exits, rather
than enters, the ground. Shallow, lined, drains on the surface can fulfil the same purpose (GeoGuide LR5).
Surface loads - are minimised. No fill embankments have been built. The house is a lightweight structure. Foundation
loads have been taken down below the level at which a landslide is likely to occur and, preferably, to rock. This sort of
construction is probably not applicable to soil slopes (GeoGuide LR3). If you are uncertain whether your site has rock
near the surface, or is essentially a soil slope, you should engage a geotechnical practitioner to find out.
Flexible structures - have been used because they can tolerate a certain amount of movement with minimal signs of
distress and maintain their functionality.
Vegetation clearance - on soil slopes has been kept to a reasonable minimum. Trees, and to a lesser extent smaller
vegetation, take large quantities of water out of the ground every day. This lowers the ground water table, which in turn
helps to maintain the stability of the slope. Large scale clearing can result in a rise in water table with a consequent
increase in the likelihood of a landslide (GeoGuide LR5). An exception may have to be made to this rule on steep rock
slopes where trees have little effect on the water table, but their roots pose a landslide hazard by dislodging boulders.
Possible effects of ignoring good construction practices are illustrated on page 2. Unfortunately, these poor construction
practices are not as unusual as you might think and are often chosen because, on the face of it, they will save the
developer, or owner, money. You should not lose sight of the fact that the cost and anguish associated with any one of
the disasters illustrated, is likely to more than wipe out any apparent savings at the outset.

                                    ADOPT GOOD PRACTICE ON HILLSIDE SITES




174                        Australian Geomechanics Vol 42 No 1 March 2007

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                   AUSTRALIAN GEOGUIDE LR8 (CONSTRUCTION PRACTICE)




WHY ARE THESE PRACTICES POOR?
Roadways and parking areas - are unsurfaced and lack proper table drains (gutters) causing surface water to pond and
soak into the ground.
Cut and fill - has been used to balance earthworks quantities and level the site leaving unstable cut faces and added
large surface loads to the ground. Failure to compact the fill properly has led to settlement, which will probably continue
for several years after completion. The house and pool have been built on the fill and have settled with it and cracked.
Leakage from the cracked pool and the applied surface loads from the fill have combined to cause landslides.
Retaining walls - have been avoided, to minimise cost, and hand placed rock walls used instead. Without applying
engineering design principles, the walls have failed to provide the required support to the ground and have failed,
creating a very dangerous situation.
A heavy, rigid, house - has been built on shallow, conventional, footings. Not only has the brickwork cracked because
of the resulting ground movements, but it has also become involved in a man-made landslide.
Soak-away drainage - has been used for sewage and surface water run-off from roofs and pavements. This water
soaks into the ground and raises the water table (GeoGuide LR5). Subsoil drains that run along the contours should be
avoided for the same reason. If felt necessary, subsoil drains should run steeply downhill in a chevron, or herring bone,
pattern. This may conflict with the requirements for effluent and surface water disposal (GeoGuide LR9) and if so, you
will need to seek professional advice.
Rock debris - from landslides higher up on the slope seems likely to pass through the site. Such locations are often
referred to by geotechnical practitioners as "debris flow paths". Rock is normally even denser than ordinary fill, so even
quite modest boulders are likely to weigh many tonnes and do a lot of damage once they start to roll. Boulders have
been known to travel hundreds of metres downhill leaving behind a trail of destruction.
Vegetation - has been completely cleared, leading to a possible rise in the water table and increased landslide risk
(GeoGuide LR5).
      DON'T CUT CORNERS ON HILLSIDE SITES - OBTAIN ADVICE FROM A GEOTECHNICAL PRACTITIONER
More information relevant to your particular situation may be found in other Australian GeoGuides:
    •    GeoGuide LR1 - Introduction                                     •   GeoGuide LR6 - Retaining Walls
    •    GeoGuide LR2 - Landslides                                       •   GeoGuide LR7 - Landslide Risk
    •    GeoGuide LR3 - Landslides in Soil                               •   GeoGuide LR9 - Effluent & Surface Water Disposal
    •    GeoGuide LR4 - Landslides in Rock                                   GeoGuide LR10 - Coastal Landslides
    •    GeoGuide LR5 - Water & Drainage                                 •   GeoGuide LR11 - Record Keeping
The Australian GeoGuides (LR series) are a set of publications intended for property owners; local councils; planning authorities;
developers; insurers; lawyers and, in fact, anyone who lives with, or has an interest in, a natural or engineered slope, a cutting, or an
excavation. They are intended to help you understand why slopes and retaining structures can be a hazard and what can be done with
appropriate professional advice and local council approval (if required) to remove, reduce, or minimise the risk they represent. The
GeoGuides have been prepared by the Australian Geomechanics Society, a specialist technical society within Engineers Australia, the
national peak body for all engineering disciplines in Australia, whose members are professional geotechnical engineers and engineering
geologists with a particular interest in ground engineering. The GeoGuides have been funded under the Australian governments’
National Disaster Mitigation Program.




                              Australian Geomechanics Vol 42 No 1 March 2007                                              175

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Report No: W7412 sl.
Client Name: Eleanor Glenn.
Report Date: August 11, 2023.
Site Address: No 73 Eungella Drive, Black Mountain.