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SC3395-SWMP Rev A
Attached to the e-mail OPW15/0134 Application for Operational Works - 60 Hofmann Dr Noosaville.
SITE BASED STORMWATER MANAGEMENT PLAN
For
KNOWLES GROUP
Proposed Townhouse Development at
Lot 4 Hofmann Drive
Noosaville
Job Ref: SC- 3395
July 2015
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SC3395-Lot 4 Hofmann Drive, Noosaville 1
AUTHORSHIP INFORMATION
Site Based Stormwater
REPORT TITLE
Management Plan
Affected
Properties
Street Address Hofmann Drive, Noosaville
RP Description Lot 4 on SP 222982
Prepared For Knowles Group
Date July 2015
Report Status For DA Approval
Prepared By
Name Matt Johnson
Qualifications BE (Civil)
Company Empire Engineering Pty Ltd
Phone Number 07 5477 6437
Reviewed By
Name Troy Paulsen
Qualifications BE (Civil), CPEng, RPEQ 6990
Company Empire Engineering Pty Ltd
Phone Number 07 5477 6437
REVISION DATE Reviewed/ Approval
O 29.11.2011
A 17.07.2015
Document Qualifying and Ownership Statement:
The contents of this document represent an assessment of the facts and circumstances pertaining to this
matter, as they are known to the writer at the time of preparation. It is possible that upon completion and
distribution of this document further information may come to hand that impact upon the findings,
recommendations or conclusions drawn in this document. This document and its contents remains the
property of Empire Engineering and cannot be reproduced in whole or in part for any reasons that could be
considered to be outside the exact, intended original use of this document.
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SC3395-Lot 4 Hofmann Drive, Noosaville 2
TABLE OF CONTENTS
1.0 Introduction ............................................................................................................. 3
1.1 Background ......................................................................................................... 3
1.2 Scope .................................................................................................................. 3
1.3 Existing Topography ............................................................................................ 3
1.4 Proposed Development........................................................................................ 5
2.0 Water Cycle Management ....................................................................................... 6
2.1 Background ......................................................................................................... 6
2.2 Wastewater Minimisation ..................................................................................... 6
2.3 Stormwater Harvesting Tanks .............................................................................. 6
3.0 Water Quality Management .................................................................................... 7
3.1 Background ......................................................................................................... 7
3.2 Construction Phase.............................................................................................. 7
3.3 Operational Phase ............................................................................................... 8
3.3.1 Water Quality Objectives.................................................................................. 8
3.3.2 Pollutant Export Modelling ............................................................................... 8
3.3.2.1 Rainfall Data................................................................................................ 9
3.3.2.2 Treatment Nodes ......................................................................................... 9
3.3.3 Effectiveness in Pollution Reduction............................................................... 10
4.0 Stormwater Quantity Management....................................................................... 11
5.0 Conclusions .......................................................................................................... 12
APPENDIX A – STORMWATER MANAGEMENT PLAN..................................................... 13
APPENDIX B – STORMWATER QUALITY MUSIC MODELLING ....................................... 14
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SC3395-Lot 4 Hofmann Drive, Noosaville 3 1.0 Introduction 1.1 Background This report is to accompany and be considered part of an application to Noosa Council for a proposed townhouse development at Lot 4 Hofmann Drive, Noosaville. 1.2 Scope Empire Engineering Pty Ltd was commissioned by Knowles Group Pty Ltd to develop a Site Based Stormwater Management Plan (SBSWMP) to outline water management strategies for the proposed development that will comply with Council’s relevant planning scheme policies, Queensland Development Code and the Environmental Protection Act (1994) and associated Environmental Protection (Water) Policy 1997. This report presents the results of a SWMP and outlines the proposed measures to be adopted in relation to stormwater quality management and stormwater quantity management for the subject site and the proposed development. 1.3 Existing Topography The subject site is described as Lot 4 on SP 222982 with a total area of 6189m2. The site is bounded by Hofmann Drive to the north-east and an environmental reserve to the remaining boundaries. The site is currently a vacant lot with an existing swale running along the western boundaries of the site. See Figure 1.1 and 1.2.
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SC3395-Lot 4 Hofmann Drive, Noosaville 4
Subject Site:
Lot 4 Hofmann Dr,
Noosaville
N
Figure 1.1 Subject Site
Figure 1.2 View from Street
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SC3395-Lot 4 Hofmann Drive, Noosaville 5 The site grades from approximately RL5.00 to RL3.00 over 80m (approximately 2.5%) to the southern boundary. A swale exists that currently collects stormwater sheet flow from the site along the western and southern boundary, discharging into the environmental reserve adjacent to the site. The environmental reserve is deemed the lawful point of discharge for the subject site. 1.4 Proposed Development Schematic architectural drawings prepared by Oksic Designs depict a proposed 30 townhouse residential development with associated driveway and carparking facilities.
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SC3395-Lot 4 Hofmann Drive, Noosaville 6
2.0 Water Cycle Management
2.1 Background
The purpose of this section of the SWMP is to outline water saving measures that will be implemented in
the design and construction of the proposed development.
2.2 Wastewater Minimisation
To reduce the impact of water demand from the development and to minimise the loading on the existing
sewerage network, it is intended to reduce the wastewater leaving the site through the use of “at source”
measures. This will include:
Water saving shower roses with a AAA rating or better
Dual flush toilet cisterns that do not exceed 6 litres on full flush and 3 litres on half flush
The use of 3 star (or higher) water efficient appliances
2.3 Stormwater Harvesting Tanks
Subsequent to the State Government’s repeals to mandatory rainwater tank usage, the developer has not
opted to utilise rainwater harvesting or re-use related to this development.
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SC3395-Lot 4 Hofmann Drive, Noosaville 7
3.0 Water Quality Management
3.1 Background
A requirement of the proposed development is that Stormwater quality treatment shall be provided to meet
the design objectives set out in Section 2.4 of DERM’s Urban Stormwater Quality Planning guidelines 2010
and the associated with State Planning Policy (SPP) 4/10 Healthy Waters. The scope typically
encompasses the ‘post construction’ phase of the development however ‘construction phase’ water quality
is briefly addressed.
3.2 Construction Phase
Table 3.1 has been adapted from Table C4.1 of Brisbane City Council’s (BCC) Stormwater Best
Management Practices 2000 and details the typical stormwater pollutants which may be generated during
the construction phase of the development.
Pollutant Sources
Litter Paper, construction packaging, food packaging,
cement bags and off-cuts
Sediment Unprotected exposed soils and stockpiles during
earthworks and building
Hydrocarbons Fuel and oil spills, leaks from construction equipment
Toxic Materials Cement slurry, solvents, cleaning agents, wash waters
pH Altering Substances Cement slurry, wash waters
Table 3.1 –Typical Construction Phase Pollutants
The following measures should typically be implemented prior to the commencement of
construction:
Education of all site workers in sediment and erosion procedures
Specified storage areas for construction materials and plant that are bunded to prevent
any spillages from escaping
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SC3395-Lot 4 Hofmann Drive, Noosaville 8
During the construction phase of the development, silt fences should be erected downstream of all
disturbed areas. In addition erosion and sediment control devices should be regularly inspected and
maintained following storm events. An Erosion and Sediment Control Plan has been provided as part of
the operational works application.
3.3 Operational Phase
During the operational stage of the development, the following impacts have been identified in relation to
stormwater runoff and water quality of the receiving waterways:
Gross pollutants which include human derived litter, course sediment and vegetation
Sediment and suspended solids
Nutrients such as phosphorous and nitrogen
To target these potential pollutants stormwater quality improvement devices (SQID’s) are proposed to be
incorporated within the design.
3.3.1 Water Quality Objectives
The water quality objectives (WQO’s) for this site were determined in accordance with Appendix 2 of the
State Planning Policy (SPP) Dec 2013.
Table 3.2 indicates the minimum load reduction targets required to be met:
Pollutant Minimum Reduction Targets
Total Suspended Sediments (TSS) 80%
Total Phosphorus (TP) 60%
Total Nitrogen (TN) 45%
Gross Pollutants (>5mm) 90%
Table 3.2 - Water Quality Objectives
3.3.2 Pollutant Export Modelling
The Model for Urban Stormwater Improvement Conceptualisation (MUSIC) has been utilised to calculate
pollutant loads from the proposed development and to predict performance characteristics of the proposed
treatment train. Modelling parameters used were adopted from the Water by Design “Music Modelling
Guidelines for South-East Queensland”, and the updated MUSIC Version 5 recommended parameters for
Bio-retention basin nodes. MUSIC modelling setup and results are attached within Appendix B.
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SC3395-Lot 4 Hofmann Drive, Noosaville 9
Under the proposed conditions, the site was ‘split’ into three land use catchment nodes; the roofed area,
driveways and ground level uses. The pollutant export parameters utilised were based on the Urban
Residential pollutant loads, refer Table 3.3.
TSS Log TP Log TN Log
Flow Type Surface Type
Mean Std Dev. Mean Std Dev. Mean Std Dev.
Roof N/A N/A N/A N/A N/A N/A
Baseflow
Driveways 1.00 0.34 -0.97 0.31 0.20 0.20
Parameters
Ground Level 1.00 0.39 -0.97 0.31 0.20 0.20
Roof 1.30 0.39 -0.89 0.31 0.26 0.23
Stormflow
Driveways 2.43 0.39 -0.30 0.31 0.26 0.23
Parameters
Ground Level 2.18 0.39 -0.47 0.31 0.26 0.23
Table 3.3 – Pollutant Export Values Adopted (Urban Residential)
3.3.2.1 Rainfall Data
Rainfall data for the site was chosen to give the best representation of actual conditions. A time period of
10 years between 1973 and 1983 was selected from the Cooroy Composite station, using a six minute time
step.
3.3.2.2 Treatment Nodes
The following devices have been used in the treatment train to reduce these pollutant loads to achieve WQO’s.
Bio-Retention Basin – A combined area of 90m2 of designated Bio-retention to treat carpark,
landscape, and roof catchments to achieve the WQO’s was modelled. An extended detention
depth of 200mm with a filter media of 180mm/hr sandy loam hydraulic conductivity has been
modelled. The location of this device is shown on the attached Appendix A.
Gross Pollutant Traps – Baskets installed to the top of each gully pit receiving to trap coarse
sediment prior to entering the drainage system. These GPT’s were modelled with the pollutant
removal characteristics of a Stormwater 360 ‘EnviroPod’ (i.e. retains 100% of gross pollutants and
coarse sediment within the range of 0.5mm to 5mm for all flows up to and including the design
storm event for the catchment).
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SC3395-Lot 4 Hofmann Drive, Noosaville 10
3.3.3 Effectiveness in Pollution Reduction
The water quality development model was set up with the incorporation of the above devices to reduce
pollutant export to WQO levels. Table 3.4 indicates the predicted pollutant mean values of stormwater
discharged from Lot 1 as calculated by MUSIC:
Pollutant Percentage Load Reduction
Total Suspended Solids (TSS) 85.1%
Total Phosphorus (TP) 61.6%
Total Nitrogen (TN) 53.6%
Gross Pollutants (>5mm) 98.0%
Table 3.4 - Flow Based Pollutant Load Reduction
The MUSIC modelling results shown above indicate that the treatment train will adequately treat TSS, TP
and TN generated by stormwater runoff in accordance with the targets required under the water quality
objectives stated previously.
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SC3395-Lot 4 Hofmann Drive, Noosaville 11 4.0 Stormwater Quantity Management The subject site is located adjacent to an environmental wetland reserve. Site inspections of the adjacent stormwater infrastructure within the Hofmann Drive road reserve identified that captured water from the local upstream catchment is directed to this wetland. As the wetland is under the control of a local statutory authority, it is deemed to be the legal point of discharge for the subject site. As such all captured stormwater from the site is proposed to be discharged to the wetland via the overflow outlet from the proposed bio-filtration device. The location of the site relative to the upstream urbanised catchment is at the downstream end of the network and adjacent to the point of discharge. In addition, the time of concentration for the subject site is much less than that of the total catchment area hence relief of the site occurs well before the upstream catchment reaches its peak discharge. With these points being considered, it has been determined that on- site detention would have no beneficial impact to peak flow discharge rates and as such no detention is proposed within the development.
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SC3395-Lot 4 Hofmann Drive, Noosaville 12
5.0 Conclusions
This report has outlined a total water cycle strategy to be adopted in the construction and operational
works phase of the development which satisfies the acceptable solutions set out in Councils planning
scheme policies.
Wastewater minimisation strategies will be adopted to reduce the demand on Council’s existing
infrastructure,
Best practice and practical water quality improvement devices are proposed which include coarse
sediment traps, and a combined Bio-retention area of 90m 2,
Due to the sites location adjacent to the point of discharge for the total catchment area, no
detention of stormwater is proposed for the site.
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SC3395-Lot 4 Hofmann Drive, Noosaville 13
APPENDIX A – STORMWATER MANAGEMENT PLAN
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13
APPENDIX A — STORMWATER MANAGEMENT PLAN
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LEGEND
SITEWORKS AND DRAINAGE PLAN
EMP RE
Bundaberg Gladstone Sunshine Coast
9 Princess Street Bundaberg Qld 4 Goondoon Street Gladstone Qld 45 Brisbane Road Mooloolaba Qld
PO Box 2052 Bundaberg Qld 4670 PO Box 1743 Gladstone DC Qld 4680 PO Box 102 Mooloolaba Qld 4557
T: 07 4154 4894 F: 07 4154 4274 T: 07 4972 5387 T: 07 5477 6437 F: 07 5444 4216
E N G I N E E R I N G E: [email protected] E: [email protected] E: [email protected]
ACN 112761510 ABN 21112761510
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SC3395-Lot 4 Hofmann Drive, Noosaville 14
APPENDIX B – STORMWATER QUALITY MUSIC MODELLING
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APPENDIX B —- STORMWATER QUALITY MUSIC MODELLING
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SC3395-Lot 4 Hofmann Drive, Noosaville 15
Figure B.1 – MUSIC Model Node Layout
Figure B.2 – MUSIC Model Treatment Train Effectiveness
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SC3395-Lot 4 Hofmann Drive, Noosaville 16
Figure B.3 – MUSIC Model ‘Bio-retention’ Node
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er r :A00teRoot—
Properties of BO__| | | | | oj oj oj | jy jj
Location Hs
;~ Inlet Properties
Low Flow By-pass (cubic metres per sec) 0.000 Is Base Lined? [7] Yes [7] No
i i 100.000
High Flow By-pass (cubic metres per sec) — Vegetation P ies
fae sree © Vegetated with Effective Nutrient Removal Plants
Extended Detention Depth (metres) 0.20
Surface Area (square metres) 90.00 © Vegetated with Ineffective Nutrient Removal Plants
Filter and Media Properties © Unvegetated
Fitter Area (square metres) 90.00
Unlined Filter Media Perimeter (metres) 38.00 Pr me =="
Overflow Weir Width (metres) 2.40
Saturated Hydraulic Conductivity (mm/hour) 180.00
Fiter Depth (metres) 0.40 Underdiain Present? (Yes [FJ No
TN Content of Filter Media (mg/kg) 400 Submerged Zone With Carbon Present? © Yes [¥] No
Orthophosphate Content of Filter Media (mg/kg) 50.0 ect fe ned 0.00
Infiltration Properties
Exiiration Rate (rm/t) 0.00 | —_ | | Nia | More |
| |X gancet || <F Beck || Brish |
a a a yy a a a
Figure B.3 — MUSIC Model ‘Bio-retention’ Node