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Stormwater Management Plan
Attached to the e-mail MCU16/0081 Geotechnical report, Landscape Plan, SMP, Traffic report - Email 3 of 3.
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Log in to see the plans as drawnSITE BASED STORMWATER MANAGEMENT PLAN
For
KNOWLES GROUP
Proposed Aged Care Facility at
Walter Hay Drive,
Noosaville
Job Ref: SC- 5594
Revision B
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SC5594 – Walter Hay Dr, Noosaville 1
AUTHORSHIP INFORMATION
Site Based Stormwater
REPORT TITLE
Management Plan
Affected
Properties
Street Address Walter Hay Drive, Noosaville
RP Description Lot 3 on SP 246584
Prepared For Knowles Group
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
A 04.05.16 T.Paulsen
B 17.06.16
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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SC5594 – Walter Hay Dr, 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........................................................................................ 4
2.0 Water Cycle Management ....................................................................................... 5
2.1 Background ......................................................................................................... 5
2.2 Wastewater Minimisation ..................................................................................... 5
2.3 Stormwater Harvesting Tanks .............................................................................. 5
3.0 Water Quality Management .................................................................................... 6
3.1 Background ......................................................................................................... 6
3.2 Construction Phase.............................................................................................. 6
3.3 Operational Phase ............................................................................................... 7
3.3.1 Water Quality Objectives.................................................................................. 7
3.3.2 Pollutant Export Modelling ............................................................................... 7
3.3.2.1 Rainfall Data................................................................................................ 8
3.3.2.2 Treatment Nodes ......................................................................................... 9
3.3.3 Effectiveness in Pollution Reduction................................................................. 9
4.0 Stormwater Quantity Management....................................................................... 10
4.1 Background ....................................................................................................... 10
4.2 Site Drainage Constraints and Opportunities ...................................................... 10
4.2.1 Drainage Constraints ..................................................................................... 10
4.2.2 Drainage Opportunities .................................................................................. 10
4.3 Modelling Overview............................................................................................ 11
4.3.1 Methodology .................................................................................................. 11
4.3.2 Catchment Areas ........................................................................................... 11
4.3.3 Roughness Coefficients ................................................................................. 12
4.3.4 Storm Events ................................................................................................. 12
4.3.5 Backwater Condition ...................................................................................... 12
4.3.6 On-Site Detention .......................................................................................... 12
4.4 Modelling Results.............................................................................................. 13
5.0 Conclusions .......................................................................................................... 14
APPENDIX A – STORMWATER MANAGEMENT PLAN..................................................... 15
APPENDIX B – STORMWATER QUALITY MUSIC MODELLING ....................................... 16
APPENDIX C – XP-STORM MODELLING .......................................................................... 19
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SC5594 – Walter Hay Dr, 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 aged care facility at Walter Hay 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 3 on SP 246584 with a total area of 26,104m2. The site is bounded by Walter Hay Drive to the south-west, and existing Noosa National Park to the remaining boundaries. See Figure 1.1.
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SC5594 – Walter Hay Dr, Noosaville 4
Subject Site:
Walter Hay Dr,
Noosaville
N
Figure 1.1 Subject Site
A crest exists approximately 30m off the south-western boundary and 70m off the eastern boundary at
RL12.50. The site falls away from this crest at approximately 3.0% grade towards the western and
southern boundaries. Swales exist inside the site off the western boundary and outside the site off the
south-western boundary. These link up with underground stormwater connections to cross the roads
Walter Hay Drive and Eenie Creek Road. The stormwater connections and swales are deemed lawful
points of discharge for the subject site.
1.4 Proposed Development
Schematic architectural drawings prepared by Oksic Designs depict a proposed 90 bed aged care facility
development with associated driveway and car parking facilities.
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SC5594 – Walter Hay Dr, Noosaville 5
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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SC5594 – Walter Hay Dr, Noosaville 6
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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SC5594 – Walter Hay Dr, Noosaville 7
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 will be 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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SC5594 – Walter Hay Dr, Noosaville 8
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 Tables 3.3 & 4.3.
Parameter Value
Rainfall threshold (mm) 1
Soil storage capacity (mm) 500
Initial storage (% capacity) 10
Field capacity (mm) 200
Infiltration capacity coefficient (a) 211
Infiltration capacity exponent (b) 5.0
Initial depth (mm) 50
Daily recharge rate (%) 28
Daily baseflow rate (%) 27
Daily deep seepage rate (%) 0
Table 3.3 – Rainfall-runoff Parameters Adopted (Urban Residential)
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 3.4 – 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.
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SC5594 – Walter Hay Dr, Noosaville 9
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 – An area of 120m2 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 these
devices is shown on the attached Appendix A.
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 3.5 indicates the predicted pollutant mean values of stormwater
discharged from Lot 1 as calculated by MUSIC:
Pollutant Percentage Load Reduction
Total Suspended Solids (TSS) 89.3%
Total Phosphorus (TP) 61.8%
Total Nitrogen (TN) 58.4%
Gross Pollutants (>5mm) 100%
Table 3.5 - 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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SC5594 – Walter Hay Dr, Noosaville 10 4.0 Stormwater Quantity Management 4.1 Background The proposed development has the potential to alter the existing hydrologic and hydraulic characteristics of the subject site unless suitable mitigation is achieved via careful hydraulic design of the proposed stormwater management drainage system. With urbanisation there is potential for sites to create or exacerbate drainage problems to downstream areas and/or drainage infrastructure. The purpose of this section of the SWMP is to determine the general requirements for bulk stormwater management for the proposed development. The design shall ensure that rainfall event discharges are mitigated and conveyed from the site in a manner that complies with Council’s Urban Stormwater Planning Guidelines and does not result in a worsened drainage situation to downstream infrastructure, without causing a nuisance or annoyance to residents/property owners. 4.2 Site Drainage Constraints and Opportunities 4.2.1 Drainage Constraints The increase of impervious areas will impact on the existing downstream boundary condition compared to pre-development peak flows. Therefore, a volume of detention will be required to limit flows to that of pre- development. This will required an detention volume over and above the bio-retention basin. 4.2.2 Drainage Opportunities The second existing swale off the western boundary is deemed the lawful point of discharge for the site as this is where the majority of site surface flows concentrate. The swale has adequate depth for Bio-retention basin and detention volume.
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SC5594 – Walter Hay Dr, Noosaville 11 4.3 Modelling Overview 4.3.1 Methodology The software package XP-STORM V2016, has been used to model the site in its current and post- developed state. The modelling has been undertaken to determine detail design parameters of on-site detention to replicate pre-development peak flow rates. As the development falls within the ‘Urban Residential’ development category (QUDM Table 7.02.1), the minor (10yr ARI) and major (100yr ARI) storm events were primarily sized for underground and overland design flows respectively. All events ranging from 1, 2, 5, 10 20, 50 and up to the 100yr were analysed to compare pre/post development discharges ensuring ‘non-worsening’ discharge. The development modelling and analysis undertaken was based on the information provided by the detailed site survey and preliminary architectural layouts. A rational method check of the pre-development scenario was conducted to calibrate the XP- STORM model. 4.3.2 Catchment Areas The subject site has been modelled in its existing pre-development and proposed post-development states with the catchment areas illustrated in Tables 4.1 & 4.2 and Appendix A. In its pre-development state the subject site was modelled as one hydrologic node to replicate the existing sheet flow situation for the lot. XP-STORM model outputs are included in Appendix C of this report. Node Description % Impervious Area (Ha) ‘PRE’ Landscape 0 0.890 Total Catchment (ha) 0 0.890 Table 4.1 - Pre Development Node Sub-Catchment Areas Node Description % Impervious Area (Ha) Combined Roof 100 0.355 Post-development Carpark/hardstand areas 100 0.197 Catchments Landscape 0 0.441 Total Catchment (ha) 55 0.993 Table 4.2 - Post Development Sub–Catchment Areas
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SC5594 – Walter Hay Dr, Noosaville 12 4.3.3 Roughness Coefficients The conduits and links used within the model are based on the ultimate design scenario for the internal roadways and overland flow paths. Mannings “n” roughness coefficient values are specified as 0.014 for RCP pipes and 0.011 for uPVC pipes. For overland flow within the sub-catchment areas a Mannings “n” value of 0.014 for concrete areas and 0.035 for vegetated areas was adopted. 4.3.4 Storm Events Storm patterns were setup using Australian Rainfall and Runoff storm patterns for Area 3 with intensity frequency duration data taken for the local area. Storm durations of 10, 15, 20, 25, 30, 45, 60 and 90 minutes were investigated for the pre and post developed scenarios. 4.3.5 Backwater Condition The site’s outlet node identified as ‘1.0’ has been modelled assuming a free outlet. 4.3.6 On-Site Detention It is calculated from the development site plan that the proposed development will increase impervious areas on the site from 0% to 55%. The proposed increase in impervious areas has the potential to increase peak flow rates to the existing drainage system. To mitigate potential increases in flow rates it is planned to detain stormwater flows on-site and discharge at a mitigated rate to the existing swale. Mitigation of flow is provided by approximately 335m3 of detention volume over and above the Bio-retention basin extended detention volume and small areas of ponding in the carpark. Flows from this storage volume will be throttled by a reduced cross-sectional area connection at the Bio-retention basin outlet (210mm), and an overflow weir. Flows from minor storms up to and including the 10 year ARI are to be conveyed in the underground drainage system. Major storm events exceeding the ARI10 year, up to and including the peak ARI 100 year events will overtop the Bio-retention basin weir and flow overland into Council’s road reserve.
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SC5594 – Walter Hay Dr, Noosaville 13
A concept drainage layout plan has been included as Appendix A of this report.
4.4 Modelling Results
A node layout plan is included in Appendix C of this report and the resultant peak flow rates are displayed
in Table 4.3 & 4.4.
ARI Design Storm (min) Peak Flow (m3/s)
1 90 0.101
2 60 0.150
5 60 0.208
10 60 0.247
20 60 0.289
50 60 0.335
100 60 0.383
Table 4.3 – Pre-Development Peak Flow Rate Results
3
ARI Design Storm (min) Peak Flow (m /s)
1 60 0.101
2 60 0.118
5 60 0.133
10 60 0.158
20 60 0.249
50 60 0.324
100 60 0.382
Table 4.4 – Post-Development (mitigated) Peak Flow Rate Results
As can be seen in Tables 4.3 & 4.4 the post-development peak flow rates to the existing drainage system
compare well to that of the existing pre-development site discharges. This is due to the large volumes of
on-site detention proposed to be included as part of the development.
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SC5594 – Walter Hay Dr, Noosaville 14
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 includes a Bio-
retention area of 120m2;
A total 335m3 of detention volume is proposed to mitigate peak flows to that of the pre-
development scenario to ensure a situation of ‘non-worsening’.
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SC5594 – Walter Hay Dr, Noosaville 15
APPENDIX A – STORMWATER MANAGEMENT PLAN
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APPENDIX A — STORMWATER MANAGEMENT PLAN
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LEGEND
CONCEPT STORMWATER MANAGEMENT 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 NG I N E E R I NG E: [email protected] E: [email protected] E: [email protected]
ACN 112761510 A B N 2 1 1 12761510
Page 18
LEGEND
CONCEPT STORMWATER MANAGEMENT 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 NG I N E E R I NG E: [email protected] E: [email protected] E: [email protected]
ACN 112761510 A B N 2 1 1 12761510
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SC5594 – Walter Hay Dr, Noosaville 16
APPENDIX B – STORMWATER QUALITY MUSIC MODELLING
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APPENDIX B —- STORMWATER QUALITY MUSIC MODELLING
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SC5594 – Walter Hay Dr, Noosaville 17
Figure B.1 – MUSIC Model Node Layout
Figure B.2 – MUSIC Model Treatment Train Effectiveness
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Figure B.3 – MUSIC Model ‘Bio-retention A’ Node
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Properties of BIA al
an GE) _) Products >>
(Inlet Properties ———__________________ | Lining Properties
Low Flow By-pass (cubic metres per sec) 0.000 Is Base Lined? (] Yes [7] No
ligh Fi ic metres 100.000
High Flow By-pass (cubic per sec) = Veasbaion open
;~ Storage Properties 6 H 3 z
© Vegetated with Effective Nutrient Removal Plants
Extended Detention Depth (metres) 0.20
Surface Area (square metres) 120.00 © Vegetated with Ineffective Nutrient Removal Plants
Filter and Media Properties —— _| © Unvegetated
Filter Area (square metres) 120.00
Unlined Fiter Media Perimeter (metres) 44,00 [- Ouilet Properties
Overflow Weir Width (metres) 2.40
Saturated Hydraulic Conductivity (mm/hour) 180.00
Fiter Depth (metres) 0.40 Underdrain Present? (] Yes [©] No
TN Content of Filter Media (ma/kg) 400 Submerged Zone With Carbon Present? © Yes [¥] No
Orthophosphate Content of Filter Media (mg/kg) 50.0 0.00
[Infiltration Properties
Exfitration Rate (mm/hr) 0.00 | | Notes. | More |
| XM cence || << Back || A Finish
T T T T T T T 7 T T T T T T T ro T T T T 7 T Y Y T T T T 7 T T
Figure B.3 — MUSIC Model ‘Bio-retention A’ Node
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APPENDIX C – XP-STORM MODELLING
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19
APPENDIX C — XP-STORM MODELLING
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SC5594 – Walter Hay Dr, Noosaville 20
Figure C.1 – XP Storm Pre-Development Catchment Plan
Figure C.2 – Pre-developed Peak Flow Hydrograph
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Figure C.3 – XP Storm Post-Development Catchment Plan
Figure C.4 – Post-developed Peak Flow Hydrograph