MCU14/0024 - Response to Information Request - Attachment 3

builder should seek guidance from this office on temporary shoring, benching or other suitable
techniques.

The allotment will support a typical form of residential construction. Structural foundations should be
designed by a competent person in accordance with AS 2870, accepted engineering theory and the
geotechnical conditions reported by this office.

All earthworks should be constructed in accordance with AS3798-1996 ‘Guidelines on earthworks for
commercial and residential developments’ and sound engineering theory.

The builder must ensure the stability of neighbouring structures is maintained through not
undermining their foundations. This is achieved via restricting any earthworks to above a line
radiating downwards at an angle of 1 in 1.5 (vertical to horizontal) from the base of the
foundation/structure to be protected.

The proposed method of construction is for a blockwork dwelling supported on ground slabs. The
allotment is suitable for this form of construction, any excavations for lower floor areas must adhere to
the recommendations contained herein.

Retaining walls for landscaping purposes would need to be constructed with consideration of maintaining
stability of the surrounding ground during construction. Such measures would include limiting the slope of
any excavations to a slope of 1 vertical to 1.7 horizontal and protecting the works against stormwater
scour. The retaining wali designs must allow for the lateral soil pressures expected including additional
surcharging from sloping backfills.

Although we consider the allotment stable in its current form there will always be a risk of landslip under
severe stormwater conditions.

Measures that will reduce this risk include the following but are not limited to.

The finished ground surface should be leveled and graded to ensure no concentration of stormwater
runoff leading to ground scour can occur.

Any collected stormwater from areas other than the roof should be disposed of downslope from the
proposed dwelling and should also ensure no ground scour can occur.

All stormwater runoff from hard landscaped areas should be directed around the perimeter of the house
and contained within the site via diversion bunding, scour proof drains and field inlets.

All stormwater collected from roofed areas should be directed to storage tanks for re-use. Overflow from
the tanks should be disposed of via rubble soakage pits downslope of the dwelling.

No stormwater runoff should be allowed to flow over any exposed excavated embankment faces or filled
batters.

Areas adjacent existing gullies must be protected against stormwater scour are susceptibie to instability
from erosion effects and over saturation. With this considered, structures should not be located adjacent
s. Also, the area adjacent the flanks of the gullies should be protected from scour via vegetation
and limiting surface grades.

 

Alt existing cross allotment flows from neighbouring properties must also be considered, managed and
maintained. Clear unhindered drainage paths must be provided and maintained during and beyond
construction. All constructed retaining walls must have effective drainage measures upstope and beyond
the walls to relieve any sub-surface water pressure/build-up. These drains must be maintained and
flushed out regularly. To achieve this we recommend bringing the upstream end of the drain to surface
and capping off to allow future flush out.

We have attached guidelines for hillside construction extracted from Australian Geomechanics vol. 35

March 2000 — “Landslide Risk Management”. These references provide commentary on good design
and building practice.

SCG Consulting Engineers 4 SCG Ref: 23277(SL)