RFI - D - Civil Engineering Response

ISSUES 10 & 11
The proposed development includes significant earthworks to construct the basement
level and these works have the potential to impact on adjoining properties. The applicant
has not provided a geotechnical report to support the proposed development. The
submitted material does not demonstrate how the proposed development achieves:
        i. The Eastern Beaches Locality Code Specific Outcome O11 (e)
        ii. The Earthworks Code:
                a. Specific Outcome O3

Information Required:
Demonstrate how the proposed development achieves The Eastern Beaches Locality
Code Specific Outcome O11 (e) and The Earthworks Code Specific Outcome O3

Provide a geotechnical report for the subject site and the proposed development. The
report must be prepared by a Registered Professional Engineer of Queensland (RPEQ).
The report must include but not be limited to:
       A site specific investigation of the soil types and the structural integrity
       A construction methodology including any measures to protect adjoining
       lands/buildings/structures and existing services within the subject site and the
       adjoining properties. Please note that all measures must be wholly contained
       within the subject site unless written approval from the adjoining land owner is
       provided

RESPONSE

There are a number of construction methods that can be used to avoid undermining
adjacent structures, these include:
     Underpinning the adjacent foundations. This is done by excavating with a bucket
       or by vacuum a narrow column at key footing positions to support their foundations
       below the garage excavation. It also has the added benefit of not imposing a
       surcharge load to the garage wall once construction is complete. Alternatively,
     A temporary shoring system such as sheet piles to the property boundary would
       support any adjacent structures during excavation of the garages. The garage wall
       would need to be structurally designed to manage some surcharge load from the
       adjacent structures as well.

Both design issues are related to the building structure and as such would be assessed
against the Building Act, Building Regulation, QDC, and the BCA as part of the future
Building Application. The response to this item confirms there are multiple construction
options that could be taken, to resolve excavation adjacent to any neighbouring
structures.

A geotechnical site investigation would be required to enable the structural design and as
part of any future Building Application submission. Given that these items are required
with future applications and there are two demonstrated scenarios above for construction
at the boundary, it is recommended that approval conditions mandating the consideration
of adjoining structures for design of building retaining walls be included with a Decision
Notice.




2008 – Margit Cres, Sunrise Beach                                                        2
CL/cl