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Appendix A- Stormwater Management Plan
Plans and drawings
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Log in to see the plans as drawn PROPOSED BOUNDARY REALIGNMENT
STORMWATER MANAGEMENT PLAN
VERSION 0
FOR
GL WALKER
HOUSE 18
LOT 5 on RP202304 PEARSONS ROAD,
COOROY
MAY 2021
AD
FH
RO
NS
SO
AR
PE
Callaghan & Toth
Civil, Environmental &
Hydraulic Engineers
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Callaghan & Toth
DOCUMENT HISTORY
Document Reference: No: 2102 SWMP_Rev0.doc
Project Manager: GL Walker
Author: Lex Toth, RPEQ
Client: GL Walker
Contact Person: GL Walker
DISTRIBUTION LIST
POSITION ON
NAME ORGANISATION MANAGEMENT REVISION REVISION REVISION REVISION
TEAM 0 1 2 3
GL Walker Client 1
Lex Toth Callaghan & Toth Author 1
Tara Norley Noosa Council Assessment Officer 1
REVISION LIST
REVISION DATE DISTRIBUTED ISSUED BY CHECKED BY
0 30 April 2021 Lex Toth Monte Plasman
The information contained in this report is confidential and proprietary to Callaghan & Toth Civil,
Environmental & Hydraulic Engineers. It may only be used by the person to whom it is provided,
for the stated purpose for which it is provided, and must not be imparted to any third person
without the prior written approval of Callaghan & Toth. Callaghan & Toth reserves all legal rights
and remedies in relation to infringement of its rights in respect of its confidential information.
©
Callaghan & Toth
2021
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Callaghan & Toth
CONTENTS
1. INTRODUCTION................................................................................................. 3
1.1 Response to Conditions of Approval ......................................................................... 3
2. DESCRIPTION.................................................................................................... 3
3. FLOODING ......................................................................................................... 4
4. STORMWATER DESIGN AND ASSESSMENT ................................................. 7
4.1 Proposed On-Site Stormwater Collection Process ..................................................... 7
4.1.1 Rainfall Data ........................................................................................................ 7
4.2 Hydrology .................................................................................................................. 7
CONCLUSIONS ......................................................................................................... 8
LIST OF REFERENCES
1. Noosa Council Planning Scheme – SC6.7 – PSP6 Engineering Design Standards
2. QUDM – 2016 Edition
LIST OF FIGURES
Plan 2102-01A Stormwater Management and Driveway Access 5
Plan 2102-02A Driveway Longitudinal Section 6
LIST OF TABLES
Table 1.1 Response to Information request 3
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Callaghan & Toth
1. INTRODUCTION
The site subject to this report is at No.18 Pearsons Road, Cooroy. The existing lot contains
one house, two driveways (only one concreted), a pool, and a shed. The back half of the lot
is undeveloped and is vegetated by grasses and shrubs. A new lot will be created in this
rear area, with access via a 4.5m wide easement for access and services along the northern
boundary.
The stormwater management assessment undertaken in this project considers:
• The extension of the existing interlot drainage system to collect flows from the new
driveway, the new house and yard runoff,
• the increase in impervious area of the lot due to the proposed additional building and
measures which can be incorporated into the design to attenuate the resultant
increase in runoff back to predevelopment levels.
The existing dwelling catchment drains to Pearsons Road. The rear yard and new driveway
drain to an existing interlot drainage system in lot 17.
The new dwelling site and battle axe driveway drain to the north east corner as shown on
plan 2102-01A the proposed new drainage system will replicate the existing catchment split.
1.1 Response to Conditions of Approval
TABLE 1.1: Response to Information Request
NUMBER CONDITION RESPONSE
2a Demonstrate that there will be no offsite impacts and that Details shown on Plan
the runoff from the site is suitably controlled to ensure that 2102-01A and Section
the downstream environment is not adversely affected or 4.2
destabilised
2b Details of collection and discharge of stormwater runoff Details shown on Plan
from the buildings and the handstand areas 2102-01A
2c Details of how the proposed Lot 20 will not increase Details shown on Plan
stormwater runoff (volume and velocity) into proposed Lot 2102-01A and Section
21, specifically with the increase in hardstand area (i.e. 4.2
driveway)
2d Any required stormwater easement in proposed Lot 21 for Details shown on Plan
the benefit of proposed Lot 20 2102-01A
2e The structures for the operational phase of the Details shown on Plan
development, including size of the pipes required, levels, 2102-01A
grades, discharge points, etc
2f Be consistent with any site-specific geotechnical report This SWMP is
recommendations consistent with the
Encompassing
Subdivision SWMP
which was based on a
geotechnical report
2. DESCRIPTION
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Callaghan & Toth
The site is on a 2,000m² parcel of land which has frontage to Pearsons Road. There is an
existing underground interlot drainage system with an outlet to a bioretention and detention
basin in the park to the east. The existing lot drains to a recent subdivision which considered
the detention and treatment of this lot as two residential lots.
3. FLOODING
The existing house drains toward Pearsons Road. The downpipes discharge into existing
kerb and channel which flows to the new subdivision detention/bioretention basin.
The runoff from the existing half of the property to be subdivided currently drains to a low
point at the north east corner where an interlot drainage pipe stub has been placed to allow
for extension of the interlot drainage system. Plan 2102-01A shows the new development
will maintain this flow path and therefore have no effect on the neighbouring property.
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10 Toth Environmental
SP298773 17 Environmental &
SP298773 Hydraulic Engineers
FH
16 SP298773
5
RP202304
(Existing Description)
Proposed
Proposed
Lot 21
Lot 20
FH
Page 7
MATCH EXISTING FOOTPATH
WITH 2.5% CROSSFALL
85th PERCENTILE VEHICLE
NATURAL SURFACE
DATUM RL 106.000
HORIZONTAL CURVES rige 138.22
VERTICAL CURVES L3.32. |L1.54L1.92] | 3.37 | L8.63 L11 L5.5 L10.07
L0.24
-714% |2.5%
-4% 112.5% 4.9% -2.5% -0.7% -3.6% 6%
VERTICAL GRADES 13.32. |L1.54L1.92] | 3.37 | L8.63 L11 L5.5 10.07
L0.24
g 2/5/8) 3/5} 8/8 B/e 8 8 o 8
DESIGN 2 N]Sle}, Bla] ofa 09 | 2 2 © 4 3
a DID! DH Qa|D oO|;|oO a|D a a a a
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a aAaldaild ald ald ala a a a a
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SURVEY 2 N]e}e} Sle} sje 00 | «0 N St N a
ee a DID! DH o|;oO oO|;|oO a|D a a a oO
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CHAINAGE aigje| gis) 8 % is
Q/LQ)O Qi o|So alo ° “9 ° 9
oO om} | LO o;|™Mm ald AlN ~” oO Tt +
18 PEARSONS RD DRIVEWAY LONGITUDINAL SECTION
A1 HORZ SCALE 1:200
A1 VERT SCALE 1:200
=|
Toth Environmental )
Environmental &
Hydraulic Engineers
PO BOX 2305
NOOSA HEADS 4567
8/41 Sunshine Beach Road
Phone 54749081
www.callaghanandtoth.com.au
designed] ADT
drawn MP.
checked MP
datum AHD DERIVED
. PM 116146
Origin (BM.) RL 107.206
approved
SURVEYED BY
project
Client
title
Q. 1.25 2.5 3.75
1:250(A3)
MURRAY & ASSOCIATES
PHONE (07) 54412188
LOT RECONFIGURATION
18 PEARSONS ROAD
COOROY Q. 4563
WALKER COLEMAN P/L ATF
DRIVEWAY LONG SECTION
LOT 5 on RP202304
Parish of TEWANTIN
County of MARCH
NOOSA SHIRE COUNCIL
Locality of COOROY
scale SCALE SHOWN IS ORIGINAL DRAWING SCALE
DO NOT SCALE FROM THIS DRAWING
USE ONLY DIMENSIONS PROVIDED
56.25 Meters. 12.5}
REVISIONS
ment] revision details date
A | FOR APPROVAL 04/21
J
FILES
COMPUTER DIRECTORY
X:\JOBS\CT PRO N PROG\2102
FOR APPROVAL
Sheet 2 of 2 sheets
drawing number
2102-02
date 27 APRIL 2021
/
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Callaghan & Toth
4. STORMWATER DESIGN AND ASSESSMENT
4.1 Proposed On-Site Stormwater Collection Process
The developed site was divided into Sub-Catchments as shown on Plan 2102-01A and the
stormwater collection system is listed below:
1. The rear of Lot 20 will have its stormwater runoff collection in a new interlot drainage pit
in the north east corner, refer Plan 2102-01A.
2. The new concrete driveway generally slopes to the rear Lot 21. The driveway will have
crossfall to the north which will drain via a mountable integral kerb to a new interlot
drainage pit in the north east corner.
3. The new Lot 21 will have its stormwater runoff collection in a new interlot drainage pit in
the north east corner, refer Plan 2102-01A.
4.1.1 Rainfall Data
The meteorological data used for the BOM IFD table for Cooroy was used for the runoff
calculations.
4.2 Hydrology
The site has been modelled as part of the previous subdivision to determine the detention
capabilities of the subdivision including this subdivided Lot 18.
The flood study shows that this lot was modelled using the same runoff coefficient and time of
concentration for the pre-development and post-development conditions as the newly created
lots for the previous subdivision. Therefore, runoff alteration improvements were included in
the sizing of the existing subdivision detention basin.
As part of the original adjacent subdivision, interlot drainage pipes were sized as per QUDM
to cater for No.18 being two residential lots.
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CONCLUSIONS
The existing Rainwater Detention Basin which is connected to the new lots via existing
interlot drains will be able to attenuate the runoff concentrations back to predevelopment
levels. As well, the external existing interlot drains were sized to carry runoff from this site
when fully developed. Therefore, the development will not have an impact on the hydrology
of the adjacent property.
The extension of the existing interlot drainage pits and pipes provides a runoff collection
system for the new driveway and house so that runoff will be collected inside the property
boundary. This will reduce the runoff to neighbouring properties to less than the existing
conditions.
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