REFERENCED Document Slope Stability Assessment MCU13/0151

                                                                                  Report No. 13N 682




3.     GEOTECHNICAL RECOMMENDATIONS FOR CONSTRUCTION



In addition to the implementation of good hillside building practices outlined in “Some Guidelines
for Hillside Construction” (which has been provided as an attachment to this report), GTS also
provide the following recommendations and geotechnical constraints for the construction of the
proposed residence.

       3.1      Earthworks

Drawings provided by Loftus Studio indicate that the proposed residence will comprise a three
story dwelling, constructed using a combination of lightweight materials and masonry walls,
predominantly on or below ground level.

Based on the drawings provided (Loftus Studio Project No. 1301, WD2.1) some excavation and
filling will be required to facilitate construction of the lower ground and ground floors.

These excavations are expected to be no greater than 1.5m to 2.0m depth with the deepest
excavation adjacent to the proposed stair landing.

Borehole information for the site suggests that excavations should be expected to encounter loose
to medium dense silty sand to a minimum of 3.0m depth. Based on local geological mapping, it is
reasonable to assume that this material extends to depths greater than the extent of borehole
investigations.

While these materials can be easily excavated, excavations in this material are expected to exhibit
extremely poor stability even in the short term. Subsequently, it is recommended that all
excavations/batters be constructed to the following maximum grades:

Where temporary batters are required,

       -     1V:1H - For all excavations in silty sands.

Where permanent batters are required the following maximum grades should be adopted:

       -     1V:2H - For all excavations in silty sands.

Grade recommendations may be increased should ground conditions during construction be more
favourable than those expected based on the results of the site investigation.

All permanent slopes should be protected against erosion in the long term by the planting of
vegetation or the installation of appropriate erosion protection.

No personnel should be permitted to enter excavations greater than 1.5m vertical height unless the
excavations are battered or shored appropriately. Personnel should also exercise caution when
working in close proximity (<1m) of cut slopes due to the risk of slope instability especially during
or after periods of wet weather.




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