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Civil Response
MPN CONSULTING PTY LIMITED
STRUCTURAL AND CIVIL ENGINEERS
Level 5, 39 Sherwood Road, Toowong, Qld, 4066
P O Box 328, Toowong, Qld, 4066
Phone 61 7 3335 4555
Email [email protected]
Web www.mpnc.net.au
ABN 39 062 191 799
Fee File: 9279
10 May 2022
Noosa Shire Council
Development Services
C/O Town Planning Alliance
57 Manilla Street
EAST BRISBANE QLD 4169
Attention: Tara Nunn
Dear Tara
RE: REQUEST FOR INFORMATION RESPONSE – RAL22/0007
83 BUTLER ST TEWANTIN
Please find enclosed response to the stormwater items noted in Noosa Shire Council’s
information request letter dated 8 April 2022.
Issue – Stormwater
The submitted documentation indicates that “Stormwater will be collected and conveyed in a new pit
and pipe network that outlets to the existing stormwater network to the south west of the site, in the
Ghostgum Court road reserve and the Butler Street road reserve.”
It is not clear that the existing stormwater network to the south west of the site is designed to cater
with the additional stormwater from the finished development.
Information Required
Demonstrate that the existing stormwater infrastructure is able to cater for the additional
stormwater post development.
Response
Currently, 1070m2 of existing catchment flows across the western boundary towards the
stormwater network to the south west of the site. Refer to the pre-development sketch
DA.02 attached to this letter.
In the post-development scenario only lot 4 (744m2) is proposed to connect
to the stormwater network to the south west of the site.
Document Control
Excellence with Economy in Engineering Approved
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Page 2
10 May 2022
The other lots are intended to have the following stormwater connections:
• Lot 1, 2, 3 – kerb adapter connections to Butler Street
• Lot 5 – Kerb adapter connection to Ghostgum Court
Refer to drawing DA.01 in Appendix 3 of the Stormwater Management Plan prepared by
MPN Consultants for details of the proposed stormwater connections.
Rational Method Calculations have been undertaken for the pre-development and post-
development flows to the south west of the site. The results indicate that the peak flows are
non-worsening from the pre-development scenario to the post-development scenario. Refer
Table 1 below and the attached calculations for details.
South West Catchment
Peak Flows (m3/sec)
Average 2 5 10 20 50 100
Recurrence
Interval (Years)
Site Pre- 0.031 0.043 0.050 0.059 0.075 0.086
Development
Site Post- 0.024 0.033 0.038 0.046 0.058 0.066
Development
Table 1 – Rational Method Flows
Attached for your reference are:
• Pre-development catchment sketch
• Rational method calculations
Yours faithfully
Sam Rowen
For and on behalf of
MPN CONSULTING PTY LIMITED
sr:sr
Excellence with Economy in Engineering 2
l:\9000-9999\9200-9299\9279\rfi\10-05-22 nsc rfi response.docx
Page 3
EXISTING
LEGEND PROPOSED
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PROPERTY BOUNDARY
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N
5.00 CONTOUR 5.00
BUILDING
CONCRETE
T
EDGE OF BITUMEN
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S
N
KERB AND CHANNEL
E
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SW STORM WATER MAIN
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W WATER MAIN
T
T
N S SEWER MAIN
SW
S
T TELECOMMUNICATIONS
E
W
E U/G ELECTRICITY
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O/H ELECTRICITY
T
N
T
FENCE
SW
S
II
N
RW RW ROOFWATER RW RW
E
W
KERB ADAPTER
W
T
T
TREE
SW
S
N
II II
II
E
II II
II
II
II
II
II
W
W
T
T
II II
II
II
II
II
II
II
II
N
N
S
N
N
E
W
II
N
II
W
T
T
S
N
E
W
II
II
W
T
T
S
N
E
E
W
T
II
W
II
T
E
T
T
RW RW RW
N
E
W
II
W
T
T
N
E
W
W
T
II
T
N
E
W
W
W
T
T
N
E
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W W
TE TE
T
II
WALL
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N
EXISTING
RET
T
CATCHMENT
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WALL
N
TO SOUTH
T
II
RET
WEST
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N
1070m2
WALL
T
II
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RET
N
T
W
N
II
T
A 09.05.22 PRELIMNIARY ISSUE SR LS
S ISSUE DATE AMENDMENT BY APP
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S
∅
S S S S S S S S S COPYRIGHT: THIS DESIGN AND PLANS ARE NOT TO BE USED OR REPRODUCED
S
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WHOLLY OR IN PART WITHOUT WRITTEN PERMISSION OF MPN
SW SW SW SW
II
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CONSULTING PTY LIMITED 2018 ©
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T N
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T N
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ABN: 39 062 191 799 P: 61 7 3335 4555
39 Sherwood Road, Toowong, Qld, 4066 E: [email protected]
CLIENT:
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NOT FOR CONSTRUCTION
ENDEAVOUR FOUNDATION
1 INTO 5 LOT SUBDIVISION
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83 BUTLER STREET TEWANTIN
W W W W QLD, 4565
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PRE-DEVELOPMENT
CATCHMENT PLAN
DESIGN: SR DRAWN: JCM SCALES: AS SHOWN
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CHKD: APPRD: DATE:
mpn JOB DRAWING No. REV
0 5 10 12.5 9279 DA.02 A
SCALE 1:250 (A1) 1:500 (A3)
PRELIMINARY
Page 4
83 Butler St, Tewantin QLD 4565
Rational Method Calculations
File: 9279
Date: 06/05/22
Stormwater Drainage Runoff - Calculations Unit Value Reference / Comments
Existing condition
Average Recurrence Interval (ARI) Years 2 5 10 20 50 100
Area ha 0.107 0.107 0.107 0.107 0.107 0.107 Existing predeveloped lot catchment to west
fi 0.250 0.250 0.250 0.250 0.250 0.250
C10 0.75 0.75 0.75 0.75 0.75 0.75 QUDM Table 4.5.3
Fy 0.85 0.95 1 1.05 1.15 1.2 QUDM Table 4.5.2
Cy = Fy * C10 0.6375 0.7125 0.75 0.7875 0.8625 0.9
Time of concentration (tc) minutes 5 5 5 5 5 5 QUDM Table 4.6.3 residential
Rainfall Intensity (I) mm / hr 163 201 223 253 292 322.0
Qpost (Peak Runoff) = (C*I*A)/360 m3 / s 0.031 0.043 0.050 0.059 0.075 0.086
Stormwater Drainage Runoff - Calculations Unit Value Reference / Comments
Developed Condition
Average Recurrence Interval (ARI) Years 2 5 10 20 50 100
Area ha 0.0744 0.0744 0.0744 0.0744 0.0744 0.0744 Post development Lot 4
QUDM table 4.5.1 - Urban residential - lot density excluding
fi 0.750 0.750 0.750 0.750 0.750 0.750 roads (max value in range given in table.)
C10 0.83 0.83 0.83 0.83 0.83 0.83 QUDM Table 4.5.3
Fy 0.85 0.95 1 1.05 1.15 1.2 QUDM Table 4.5.2
Cy = Fy * C10 0.7055 0.7885 0.83 0.8715 0.9545 0.996
Time of concentration (tc) minutes 5 5 5 5 5 5 QUDM Table 4.6.3 residential
Rainfall Intensity (I) mm / hr 163 201 223 253 292 322.0
Qpost (Peak Runoff) = (C*I*A)/360 m3 / s 0.024 0.033 0.038 0.046 0.058 0.066