RFI - D - Civil Engineering Response

Page 2

Our Reference: 2008

23 July 2020


Property Projects Australia
PO Box 1264
New Farm Qld 4005

Attention: Alan Irvin



Dear Alan,


RE:      RESPONSE TO COUNCIL INFORMATION REQUEST DATED
         19/05/2020, APPLICATION No. MCU20/0037
         11 MARGIT CRESCENT, SUNRISE BEACH
         (LOT 135 on RP132135)


We refer to Council’s Information Request letter dated 19 May 2020, and provide the
following partial response to engineering items as listed in the above request.

ISSUE 9
The proposed development includes 2 separate driveways and no on-site manoeuvring
area to permit vehicles to exit in a forward gear. The 2 driveways will result in a loss of
on-street parking space. The proposal does not achieve the specific outcomes of the
relevant codes and is not in accordance with the relevant probable solution:
       i. The Eastern Beaches Locality Code:
                a. Specific Outcome O42, Probable Solutions S42.3 and S42.4
       ii. The Driveways and Carparking Code:
                a. Specific Outcome O1, Probable Solution S1.2
                b. Specific Outcome O8
                c. Specific Outcome O11, Probable Solution S11.1
       iii. The Transport, Roads and Drainage Code:
                a. Specific Outcome O4

Information Required:
Provide amended plans that achieve the specific outcomes of the applicable codes and/or
are in accordance with the probable solutions. Alternatively provide sufficient justification
from suitably qualified persons to demonstrate how the development achieves the specific
outcomes of the applicable codes

RESPONSE
TTM Consulting Pty Ltd (TTM) have prepared a traffic impact statement for the proposed
development (Ref: 20BRT0181), providing justification to demonstrate how the
development achieves the specific outcomes of the applicable codes. A copy of TTM’s
statement has been enclosed with this letter.




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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.




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ISSUES 12 & 13
The basement level of the proposed development extends across the full width of the
subject site and has the potential to cause ponding on the subject site and/or direct
surface runoff on to the adjoining properties. The submitted material does not
demonstrate how the proposed development achieves The Earthworks Code - Specific
Outcomes O1 and O2.

Information Required:
Demonstrate how the proposed development achieves The Earthworks Code - Specific
Outcomes O1 and O2

Provide a preliminary stormwater design for the proposed development. The design must
be prepared by a suitably qualified person and include but not be limited to:
       The existing overland flows and the proposed overland flows,
       Maintenance of overland flows within the subject site,
       The drainage system for the proposed roof areas, hardstand areas, grassed areas
       and pool surrounds.

RESPONSE
There are 0.96m wide landscape strips to each side of the subject site. This is sufficient
space to manage overland flow from major design storms beyond the capacity of the
building gutters. To demonstrate, the estimated catchment to the rear yard is determined
as follows:




Roof Catchment 105m2.




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Ground Catchment 182m2.




Upstream Catchment 315m2.




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[OCR of page images]
 

Ground Catchment 182m?.

   

Upstream Catchment 315m2.

 

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The upstream catchment is assumed to be worst case from the rear yards only. A quick
check of Streetview confirms that the two upstream properties discharge their roofwater
to the kerb and channel in Orealla Crescent and the property surfaces have been built up
so that any gutter runoff would flow to the street as well.

         Roof Catchment       = 105m2
         Ground Catchment = 497m2
         Ground Fraction Imp = 0.61
         Time of Concentration= 5 minutes

         Q100 (includes >Q20 from roof catchment) = 48L/s

This flow would probably be split each way around the proposed building and would easily
be managed by “scupper” pipes through the terraced wall, down to the driveway area
below. Alternatively, a 250x250 floor grate with 100mm of water above the grate surface
can capture 24L/s at 50% capacity. One of these on each side as “relief” would be
sufficient to convey any major storm surface water to Margit Crescent. Again, design of
the building surrounds and site stormwater management would be addressed as part of
a hydraulic design in accordance with AS3500.2 to be incorporated in a Building
Application.




                                    Indicative Ground Level Drainage




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                                    Indicative Garage Level Drainage

Site Drainage is typically developed in coordination with other consultants where their
input is required in detailed design phase. The above calculations are provided to
demonstrate that there are suitable ways of managing any major storm surface flows
around that building without impacting on the neighbouring properties or incurring local
flooding inside the proposed dwellings. Final design coordination of this can be
conditioned for certification by a hydraulic designer or RPEQ engineer as part of a
Decision Notice.


ISSUES 14
An existing Unitywater sewer main runs across the site adjacent to the rear boundary and
the proposed works have the potential to impact on the sewer main and its ongoing
maintenance. The submitted material does not demonstrate how the proposed
development achieves The Existing Services - Specific Outcomes O1 and O2

Information Required:
Provide written approval for the proposed works from Unitywater

RESPONSE
The position of the buildings with respect to the Unitywater sewer main along the rear
boundary are addressed under the Queensland Development Code QDCMP1.4 (Dec
2013). The QDC is applied to a development in accordance with the Qld Building Act 1975
and Building Regulation.
The provisions of the QDC are currently met as demonstrated by the below excerpt from
the architectural drawings, highlighting the distance from the sewer to the building. It is
acknowledged that the swimming pools may need to be shifted to comply with the QDC,


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but this is not a fundamental imposition to being able to decide this Material Change of
Use application, and would be addressed as part of a future building application with a
mandatory concurrence agency referral to Unitywater as an interested party. This is
required for any building approval to demonstrate compliance with the QDC.




We trust this satisfactorily addresses the above issues raised in Council’s Information
Request letter.




Yours sincerely,




____________________________________________
CAMERON LANDRETH – DIRECTOR (RPEQ 19358)
BEng (Hons), NER, RPEQ
For and on behalf of:
BARLOW SHELLEY CONSULTING ENGINEERS (AUST) PTY LTD




2008 – Margit Cres, Sunrise Beach                                                      7
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