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response to information request updated letter - pomona subdivision 19.11.2021
19 November 2021 Patrick Murphy Noosa Council [email protected] RE: Response to Information Request RAL21/0017 – 25 Pavilion Dr, Pomona Council issued a further advice request on 13 September 2021. The applicant provides the following additional information in response to the items: 1. The waterway to be clearly identified on all plans. 2. Amended plans which provide for 10 metres of rehabilitation either side of the waterway. 3. The bio-basin to be re-located outside of the 10-metre-wide waterway rehabilitation area. Please find attached response from Joshua Lee – North Coast Environmental Services including: Revegetation either side of the drainage feature is not expected to significantly enhance water quality outcomes as compared to the existing grass cover about, and within, the drainage feature. Furthermore, no vegetative riparian values are associated with the drainage feature within the site or within adjoining sites to the immediate north and south. The request to revegetate the drainage feature is therefore not considered a priority conservation outcome for the site….It is noted a very significant net gain in riparian habitat; approximately 0.38ha, will arise as a result of the development given the proposal to rehabilitate the currently denuded Riparian Protection Area in the west of the site. We seek to further discuss the matter with Council’s environmental officer and Coordinator of Development Assessment with an onsite meeting.
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4. Provide an accurate plan of the 1%AEP inundation extent at year 2100 for the
development site and demonstrate that all proposed filling is located outside
of this inundation extent.
Peak Urban have directly addressed this matter in their updated Stormwater Management
Plan dated 28 October 2021.
The corner of Lot 10 is shown to be partially inundation in the 1% (2100) AEP (noting
it is flood free in smaller events including the 1% AEP). A flood impact assessment
was completed using NSC “Pomona Flood Model” in order to demonstrate no off-site
impacts, no loss of floodplain storage and compliance with the Flood Overlay Code.
The proposed 3m wide open drain along the southern boundary to Lot 10 is able to
manage the flood flows through this part of the site. Refer to Section 2.2 for this
assessment.
5. Either amend the proposal plans and preliminary earthworks plans to
demonstrate no filling within the 1%AEP (2100) inundation extent, or provide
a flood impact assessment which demonstrates no loss of floodplain storage
and no off-site flood impacts associated with the filling.
Peak Urban have directly addressed this matter in their updated Stormwater Management
Plan dated 28 October 2021.
The corner of Lot 10 is shown to be partially inundation in the 1% (2100) AEP (noting
it is flood free in smaller events including the 1% AEP). A flood impact assessment
was completed using NSC “Pomona Flood Model” in order to demonstrate no off-site
impacts, no loss of floodplain storage and compliance with the Flood Overlay Code.
The proposed 3m wide open drain along the southern boundary to Lot 10 is able to
manage the flood flows through this part of the site. An additional shallow cut area is
to be provided in Lot 10 to off-set the loss of flood plain storage. Refer to Section 2.2
for this assessment.
6. Either amend the plans to ensure all works are fully contained within the
subject lot, or If works within Lot 4 RP809059 are required to support the
application, then amend the application to include this lot and include
landowners consent.
All works are to be fully contained within the subject site as per the Service Layout Plan
by TODS dated 11/11/2021.
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7. Provide a detailed site survey, with 0.25m contour intervals, in order to
illustrate the existing drainage patterns on the site.
The detailed contour survey is included with the response and referenced within Peak
Urban’s Flood Storm Water Management Plan.
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8. Justify how the proposed discharge from the bioretention basin does not
represent a concentration of flow onto the neighbouring lot and how
discharge rights can be secured over the neighbouring lot in order to ensure
that the outlet from the bioretention basin will not be impeded in the future.
Is there any reason why the discharge from the bioretention basin cannot be
directed onto the balance of proposed lot 10 instead, in order to avoid these
issues with the neighbouring lot?
Preliminary Drawings have been prepared for the proposed bio-retention basin. The size
of the basin is based on parameters contain in the Stormwater Management Plan prepared
by Peak Urban. TODs plans demonstrate the required bio basin filter area (120m2) and
storage volume can be provided with the allocated space in the plan of development.
1 in 4 batters have been adopted throughout except for a 1 in 2 batter on the northern side
of the basin. There should be no need for any retaining walls in the bio basin. The outlet
from the basin is directed to the west towards the creek as well as discharging into the
balance area of lot 10 in a non-worsening manner.
9. Provide revised sizing/modelling and associated engineering drawings and
reporting for the detention storage proposed for the development site,
which achieves the following:
a. Includes analysis for the 1%AEP (2100) event
b. Is undertaken using the ensemble storms approach of ARR2019
c. Clarify the continuing loss assumed for impervious site areas. The
pervious initial loss reported in the SWMP appears to be much lower
than the recommendations of either QUDM or ARR2019 and is likely
to result in under-sizing of the detention storage due to an over-
estimate of the pre-development peak flows. Justify the assumed
initial loss or adopt a revised value consistent with QUDM and
ARR2019
d. Update the basin design to ensure the freeboard requirements of
QUDM are achieved for the 1%AEP (2100) event
e. Demonstrates no increase in peak flows for all events up to and
including the 1%AEP (2100) event, for the range of durations
applicable to the downstream land, not just the critical duration at
the site boundary
f. Consider whether detention storage is necessary if discharges from
the bioretention basin are directed to the West into the balance lot
10, rather than the neighbouring property.
Peak Urban have directly addressed this matter in their updated Stormwater Management
Plan dated 28 October 2021.
a. Updated to include the 1% (2100) AEP event.
b. Modelling completed using ARR2019 ensemble storms.
c. Sensitivity assessment of losses completed using 30mm initial loss (refer
Section 2.1.5). Results achieve a similar outcome to the smaller initial loss
of 10mm originally used.
d. Discussion of freeboard in the 1% (2100) AEP is presented in Section 2.1.4.
e. Peak flows for a range of durations are presented in Appendix B. This
shows that the peak is critical with respect to non-worsening.
f. As discussed in Section 2.1.4, an existing flow path direct runoff north and
into an existing dam. This discharge point has been maintained so as to
not impact the water catchment of these farm dams. Non-worsening has
been achieved in the smaller events to this property. In the larger events,
the small increase noted would be drowned out by flooding from Cooroora
Creek.
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10. Provide an updated MUSIC model and SWMP which includes all catchment
areas flowing to the bioretention basin in the model.
Peak Urban have directly addressed this matter in their updated Stormwater Management
Plan dated 28 October 2021.
MUSIC modelling has been updated to reflect this request and detailed in Section 3.
Bioretention filter area has reduced to 80m2.
11. Provide travel paths for the required waste collection vehicle, demonstrating
how it will manoeuvre on site without having to use more than a 3 point turn
to turn around.
The garbage truck turning plan for the turning head is included as part of the revised
engineering design.
12. Provide a plan indicating all the vegetation, on road reserve, required to be
cleared to ensure safe sightlines.
TODs provide the following comments regarding the site lines and vegetation:
The road reserve boundary is set back 6m from the existing nominal kerb
alignment meaning there is adequate space for a car to stop and see vehicles on
Pavilion Street without being impacted by property fences. The required safe
intersection distance (SISD) in each direction for vehicles exiting the new road,
when taken 3-5 back from the nominal kerb line generally meets the minimum
requirements in Austroads Part 4A.
The standard design requirements as set out in table 3.2 for a 60kph design speed
is between 114-123m. The visibility to the north is unobstructed and exceeds
250m. The visibility to the south is slightly impacted by the low crest at the
intersection of Sandy Street and a sag in Pavilion Street approximately 115 south
of Sandy Street in front of No 20 Pavilion Street. The visibility in this direction is
approximately 103m (adjacent to the entry to the caravan park), however it should
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be noted that given this is an existing street Extended Design Domain standards
can be adopted, which would reduce the visibility requirements to between 81 and
89m. The visibility in this direction exceeds the EDD sight distance requirements.
A site check has confirmed that no clearing of existing vegetation is required – refer
photos below.
Sight Visibility to the South of proposed intersection shown below
Sight Visibility to the North of proposed intersection shown below
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13. Noting that all retaining structures must be within the lot they support, or
otherwise be covered under an easement, provide additional detail on the
proposed retaining walls. The detail must be prepared by a Registered
Professional Engineer of Queensland and include but not be limited to:
a. cross sections at the highest point of each of the proposed retaining
structures indicating the location of the walls and foundations in
relation to the property boundaries, the proposed building pad and
finished ground levels;
b. the type of wall construction (material, foundations, etc.);
c. the structures required to collect and convey existing overland flows
that are impacted on by the construction of the walls;
d. any fencing to be installed on top of or beside the walls;
e. the location of any services, above or below ground, adjacent to the
proposed walls.
The retaining wall details are included as part of the updated TOD engineering plans and
specific comment below:
The preliminary drawings show proposed earthworks for the site that includes
providing level house pads for future owners to build on. We have shown indicative
locations and heights for retaining walls on the preliminary drawings; however it is
planned to minimise the extent of retaining walls for aesthetic and costs reasons.
Full extent of retaining walls will be determined during the detailed
design/Operational Works phase. A typical detail for a concrete sleeper wall has
been included in the preliminary engineering drawings, however it should be noted
that as these are proprietary items they are designed and certified by the
supplier/contractors RPEQ.
In order to construct the bio retention basin, it will be necessary to import fill to the
site to lift the blocks and road level above the basin levels. The amount of fill will
be refined during the detail design.
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14. Provide RPEQ written certification, certifying that the proposed filling
works and retaining structures, will not cause a worsening of stormwater
conditions by adversely altering stormwater drainage characteristics
external to the site, including, but not limited to:
a. additional ponding on neighbouring properties;
b. increased runoff onto neighbouring properties;
c. redirect overland flows.
TODs plans have been designed in coordination with Peak Urban’s Stormwater
Management Plan, which conclude:
It has been demonstrated that non-worsening of peak flows has been achieved
to the discharge point for events up to the 10% AEP event (refer Table 2-7).
The results show that there is non-worsening for events up the 5% AEP, with a
minor increase noted in the larger events. The intent of sizing the detention
basin is to mitigate flows up to the 10% AEP storm event to ensure non-
worsening of discharges into the downstream flow path. In larger events, flows
from the site will start to sheet flow across the rear of the site to Cooroora Creek.
As the discharge point for the site becomes inundated from Cooroora Creek
flooding in the major storm event, it is considered that the very minor increases
noted from the site become inconsequential as a result of downstream site
being drowned out by creek flooding. The catchment size of Cooroora Creek
reporting past the site is approximately 1,400 ha. The very minor increases in
peak flows in the major event would be considered to not result in any
quantifiable change to downstream flooding conditions.
15. Provide cross sections – including the finished ground levels of the
proposed works and neighbouring properties – for the sections marked in
the snippet below, including a 2m wide footapth:
Updated cross sections are provided through the relevant areas with finished levels.
16. Provide Unity Water’s written approval for a low-pressure sewer system for
the proposed development.
17. If the proposed lots cannot be connected to sewerage reticulation,
amended plans are required with minimum lots sizes of 2,000m2.
TODs provide the following comments in regard to the Unitywater sewer connections.
There is an existing sewer main traversing the site aligned with the rear of existing
dwellings/properties along Pavilion Street. Noosa A H & I Society Inc (Pomona Show
Grounds) have given their in-principle support to permit the extension of the existing
gravity sewer main within their property to allow the new lots to be fully services by a
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gravity sewer main. Unity Water have confirmed that if the agreement between JNE
Developments Pty Ltd and Noosa A H & I Society Inc cannot be concluded then Unity
Water will permit low-pressure sewer system as an alternative system. As such we have
revised our preliminary engineering drawings to show the proposed gravity sewer. It
should be noted that this sewer line can be extended in the future to service the
development of lots to the north the subject site.
18. Provide details on the easements proposed to be extinguished, including,
but not limited to:
a. Purpose of the easements;
b. Reason for extinguish them;
c. Benefited party(ies) written agreeing to the extinguishment of these
easements.
Agreement has been granted from the existing property owner to re-direct their
stormwater to the new street - so the stormwater easement (Easement C in lot 21
SP316902) is no longer required.
Easement D in lot 21 SP 316902 is for sewer, Unity Water have confirmed that
Easement D can be extinguished to reflect the new road and lot layout.
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Pursuant to the Development Assessment Rules, the applicant has given the assessment
manager the information requested in the information request. Please proceed with the
assessment of the application at your earliest convenience.
If you have any further queries in relation to the above, please do not hesitate to contact
myself.
Regards,
Jack Lewis B.Sc Hons UNSW M.Plan Otago MPIA MQELA
Planner/Director
Pivotal Perspective Pty Ltd
0406 334 227
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