220508.2 - Response to Information Request OPW

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DME Projects Pty Ltd
P.O. Box 7481
Sippy Downs, QLD, 4556
Tel 0438 157 612
ABN 79 224 274 637

                        Response to Information Request (OPW23/0179) – 128 Gympie Tce Noosaville
                                                                                        Page |2
See below advice and image that has been provided by the preferred contractor, showing the extent
of each type of shoring construction; the referred attachment (paper from the Gold Coast
municipality) is included in this response.


        As per offer sent our intention is to use a CFA-piled secant-wall for your basement, except
        where it is proposed you utilise the existing retention wall done by the development to the
        ‘East’.

        For clarity CFA-piling (Continuous Flight Auger) is a system of pile installation that is vibration
        and collapse free due the immediate replacement of excavated soil with concrete, and has a
        very low noise level compared to alternate piling methods of vibration and driving.

        The secant description is the overlapping round piles ‘secanting’ one another as per the
        diagram below.

        The benefit of this system is in preventing running dry or wet sand from falling into the
        excavation, as is possible with the gaps that are left with Contiguous or soldier pile systems.

        This is sometimes only evident in rain events, or once the sand layers dry out after exposure
        to air.

        The layout of the proposal for this site is shown below in a 3D schematic to protect the
        neighbour to the ‘West’ and provide a safe working space for the developments construction.

        The existing sheets are shown in grey.

        For additional information:

        This technique is now the preferred system of most councils for basement related works in
        built up areas, as it is the least disturbance; vibration, risk of collapse and noise, in both
        saturated and dry soils.

        Concrete Piled walls are also less prone to movement and so less risk in terms of services
        below ground, where even small movement or loss of bedding material can affect
        infrastructure.

        We have attached a paper from the Gold Coast municipality highlighting their change in
        preference, for the reasons stated above.

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DME Projects Pty Ltd
P.O. Box 7481
Sippy Downs, QLD, 4556
Tel 0438 157 612
ABN 79 224 274 637

                         Response to Information Request (OPW23/0179) – 128 Gympie Tce Noosaville
                                                                                      Page |3




Notwithstanding the above, we acknowledge Councils concerns regarding the impact to the projects
ability to provide dense deep planting and offer that the reduction is not significant enough to justify
a change to driven sheet piles for the full extent of the excavation. As per the advice above, driven
sheet piling by its nature introduces vibrations into the ground that have a significantly higher
likelihood of impacting adjoining structures. The adjacent lot to the west is developed and has an
appreciable dwelling constructed close to the boundary. The contractor has considered this and is
proposing the best method of ground support accordingly based on the advice of specialist ground
support engineers. It is our opinion that best practice engineering methods should be considered
and implemented as a project priority.

We also offer that the proposed boundary fencing is to be core filled block wall that typically has
strip footing similar to the width of the proposed pile wall (in sand) and that the pile wall may only
project >100mm further into the site depending on the alignment/location within the site. The pile
wall cap will also be at a depth below finished surface allowing for potential planting closer to the
wall without preventing root establishment into deeper ground.

Further to this, the structural engineering drawings were provided in the original submission to
demonstrate the extents of the temporary and permanent works with the information that was
available at the time. It is expected the design iterations and plan amendments will be required
following award of the contract and we propose that these can be submitted to Council for
information prior to the prestart meeting. It was not the intention that the structural engineering
plans be included in the Operational Works approval approved documents.

Issue
     Flooding and access to the basement. The driveway ramp to the basement does not
     incorporate the required 300mm freeboard above the defined flood level (DFE).
     Information Required
          3. Amend the driveway and access design to ensure that 300mm freeboard above the DFE
          is achieved for all openings to the basement or provide a passive flood barrier system
          which will achieve the equivalent level of protect and flood immunity for the basement.

Page 4

DME Projects Pty Ltd
P.O. Box 7481
Sippy Downs, QLD, 4556
Tel 0438 157 612
ABN 79 224 274 637

                        Response to Information Request (OPW23/0179) – 128 Gympie Tce Noosaville
                                                                                             Page |4
The proposed design achieves a continuous flood bund/barrier above the 1%AEP Defined Flood
Event as per the Planning Scheme Flood Hazard Overlay Code Table 8.2.6.3 AO6.5 editors note that
states “ Editor's note—Basements should have flood immunity above the 1%AEP defined flood event
with alternative means to mechanical pumping used to achieve such immunity”

Compliance with the AO does not require the basement flood immunity design to achieve the
1%AEP plus freeboard and freeboard has not been incorporated into the design accordingly. This
was investigated during the MCU application phase and in our opinion was confirmed by email from
Mark Lewis to Dale Martin on 16th February 2023 with the following:
    In regard to the specific site I would suggest that the driveway would need to achieve the 1%AEP
    level as a minimum before entering the basement. If that requires works on the driveway of the
    neighbouring property to achieves grades the adjoining property would need to be in agreement
    and I would suggest that you would need to ensure that your new works do not adversely impact
    on the adjoining development.

It is not possible to ramp the driveway to a higher level without introducing grades that are in excess
of the limits of AS2890.1, this was thoroughly tested during earlier design development. The site is
narrow and the requirement to access via the existing easement arrangement (not directly to
Gympie Tce) is a constraint that does not allow for any additional height to the driveway bund.

We also offer to Council that the basement is not a habitable space, will be constructed using
concrete and other flood resistant products and as such achieves compliance with all parts of QDC
MP 3.5. – Construction of Buildings in Flood Hazard Areas.

Issue
     The submitted dewatering management plan requires amendment.
     Information Required
          4. Provide an updated dewatering management plan that includes the following:
                   i. The DMP states that the shoring design is provided in Appendix C – however only
                   the civil engineering plans are provided. Include plans which show the location and
                   type of temporary shoring, groundwater spears, treatment and monitoring equipment
                   location and space requirements. Why do the structural engineering plans (provided
                   separately) only show shoring on 3 sides of the excavation? The type of CFA piling
                   (contiguous or secant) should also be stated on plan
                   ii. Remove references to ‘steel sheet piling’ on page 10 and refer to CFA secant piling.
                   Please note that the references should reflect the proposed method or the alternate method
                   chosen by the civil engineer.
                   iii. Update section 6.5.2 and 6.5.3 (Water Quality Monitoring) to include continuous
                   monitoring of pH and dissolved oxygen at the release point from the treatment
                   system. Total iron and aluminum are to be sampled where identified in the document
                   as ‘if required’.
                   iv. Update the figure in Appendix A to also show the stormwater network and specifically the
                   stormwater pit which the dewatering system will discharge into and the outlet headwall.
                   v. Update section 6.4.3 to identify that discharge is to the stormwater network prior to
                   entering the canal system.
                   vi. There seems to be plenty of room in the frontage of the site for establishing a
                   groundwater monitoring bore outside of the excavation and shoring system in which

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DME Projects Pty Ltd
P.O. Box 7481
Sippy Downs, QLD, 4556
Tel 0438 157 612
ABN 79 224 274 637

                         Response to Information Request (OPW23/0179) – 128 Gympie Tce Noosaville
                                                                                      Page |5
                 to monitoring groundwater drawdown and quality. Update the monitoring section of
                 the DMP to incorporate such a monitoring location.
                 vii. Section 7 (Noise) is to be updated to refer to the default noise standard for pumps
                 in Section 440T of the EPAct. The EEP (Noise) objectives currently referenced are
                 long-term objectives rather than a specific enforceable standard.
                 viii. Provide dilapidation reports for neighbouring properties and any other structures or
                 infrastructure identified as being within the estimated cone of depression associated with the
                 groundwater drawdown.

We have spoken with the author of the report and offer to Council that there will be a range of
amendments required to the report prior to construction, including but not limited to the
identification of the contractor and responsible persons, confirmation of the type/brand/details of
proposed plant and equipment and other specific information relating to the contractors proposed
construction methodologies, including ground shoring and ground support as identified by Council.
We do not consider that the amendments requested in this item will fundamentally impact the
outcomes of the plan and request that Council condition the approval as such, with the requirement
to provide a complete amended Dewatering Management Plan to Council for approval prior to the
prestart meeting.

Notwithstanding this, we provide the following to Council regarding item iv) and the proposed point
of discharge. The images below show the existing stormwater pit within the Gympie Tce frontage of
the adjoining lot to the east, in front of the existing bus stop. This pit is the closest to the site and
most suitable for discharge of the groundwater. Further details regarding pumping, pipework
type/alignment and the interaction with the public will be clarified in the amended report, to be
submitted prior to works commencing.

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DME Projects Pty Ltd
P.O. Box 7481
Sippy Downs, QLD, 4556
Tel 0438 157 612
ABN 79 224 274 637

                         Response to Information Request (OPW23/0179) – 128 Gympie Tce Noosaville
                                                                                      Page |6




Issue
     A number of the submitted engineering plans are stamped “not for construction” and have not
     been signed by the RPEQ.
     Information Required
          5. Provide amended plans that are for approval and construction and are signed by the
          RPEQ.

The Engineering Plans have been amended and are now marked For Construction and signed by
RPEQ accordingly.

We trust that this additional information is acceptable to Council and look forward to approval of
the proposed work. If you have any questions regarding this response please contact me directly.


Yours Faithfully



Dale Martin - Director
B Eng (Civil), RPEng, RPEQ
DME Projects Pty Ltd