2

Stormwater Management Plan 6 Townson Road,

Marsden Park, NSW, 2765

CONTENTS

1.0 INTRODUCTION......................................................................................................... 3

2.0 SITE LOCATION AND DESCRIPTION .................................................................. 3

3.0 DEVELOPMENT PROPOSAL .................................................................................. 4

4.0 EXISTING STORMWATER NETWORK ................................................................ 4

5.0 PROPOSED STORMWATER NETWORK .............................................................. 4

6.0 STORMWATER QUANTITY MANAGEMENT ..................................................... 5

7.0 STORMWATER QUALITY MANAGEMENT ........................................................ 5

7.1 RAINWATER TANKS ............................................................................................. 5

7.2 GROSS POLLUTANT TRAPS (GPT) ................................................................... 6

7.2.1 Humeceptor ................................................................................................................... 6

7.2.2 SPEL StormSack ........................................................................................................... 6

7.2.3 Bio-Retention Basin ...................................................................................................... 6

7.3 WATER QUALITY OUTCOME – MUSIC MODEL........................................... 6

8.0 STREAM EROSION INDEX (SEI) ............................................................................ 7

9.0 OVERLAND FLOW PATHS ...................................................................................... 7

10.0 CONCLUSION ............................................................................................................. 8

APPENDIX A – SITE PLAN AND CIVIL DRAWINGS .................................................... 9

APPENDIX B – PCSWMM CALCULATOR REPORT ................................................... 10

APPENDIX C – MUSIC-LINK REPORT .......................................................................... 11

APPENDIX D – STREAM EROSION INDEX CALCULATIONS ................................. 12

3

Stormwater Management Plan 6 Townson Road,

Marsden Park, NSW, 2765

1.0 INTRODUCTION

Richmond and Ross Pty Ltd, Consulting Engineers, have been engaged to prepare a Stormwater

Management Plan for the proposed development at 6 Townson Road, Marsden Park, NSW, 2765. No

responsibility to third parties under the law of contract, tort or otherwise for any loss or damage is

accepted.

The purpose of this assessment is to provide advice with respect to stormwater management for the

proposed development. The results of this study are limited to this scope.

This assessment has been prepared by reviewing published topographic maps, physical land survey,

hydraulic and hydrological calculations, available Ariel photography of the site and in accordance

with Blacktown Development Control Plans below:

Part A – Introduction and General Guidelines.

Part D – Development in the Business Zones

Part J – Water Sensitive Urban Design and Integrated Water Cycle Management

2.0 SITE LOCATION AND DESCRIPTION

The subject site is located at 6 Townson Road, Marsden Park, NSW, 2765 being Lot 44 in DP

1175138. The total area of the lot is approximately 2.223Ha (22230m2). The Lot generally slopes

towards Bells creek which runs through the Lot and is bounded by Townson Road to the North and

Richmond Road to the West. The existing impervious area is approximately 2500m2 which comprises

of a gravel road, concrete driveway and ground floor slabs of previously existing buildings. There is

no record or evidence of existing on-site underground stormwater drainage network. The site drains

via surface runoff to Bells Creek.

Figure 1 Proposed Development Satellite View (Extract from NearMap)

Development

extent

Lot boundary

4

Stormwater Management Plan 6 Townson Road,

Marsden Park, NSW, 2765

Figure 2 Proposed Development Map View (Extract from NearMap)

3.0 DEVELOPMENT PROPOSAL

It is proposed to construct a bulk goods premises and two additional future takeaway food premises

on part of the lot at 6 Townson Road, Marsden Park. The bulk goods premises are proposed to have a

floor area of 1469m2 and an office within the premises with an area of 150m

2. The two future

takeaway food premises are proposed to have a floor area of 282m2 each.

4.0 EXISTING STORMWATER NETWORK

The site currently drains via surface overflow into Bells Creek. Additionally, there is a culvert

discharging stormwater into the south western corner of the site boundary. The stormwater from this

culvert then flows along the southern boundary via surface flow to Bells Creek.

5.0 PROPOSED STORMWATER NETWORK

It is proposed to construct a new stormwater network to convey stormwater through and from the site

on the following principles:

A new network of pipes and pits is proposed to convey the runoff from the site to the bio

retention basin for treatment.

Total roof area including the future takeaway food premises is 2225m2. Three rainwater tanks

will collect all the runoff from the roofs. A 55kL tank for the bulk goods premises, 30kL tank

for future takeaway food premises 1 and 40kL tank for future takeaway food premises 2. The

collected water will be used for toilet flushing and landscape irrigation within the site.

Analysis from MUSIC indicates a minimum of 80% of non potable water demand of the site

Development

extent

Lot boundary

5

Stormwater Management Plan 6 Townson Road,

Marsden Park, NSW, 2765

is achieved by this arrangement. See stormwater quality management in section 7 for more

details.

A system consisting of swales, bio retention basin, Humeceptor and a SPEL stormsack treat

the runoff before discharging to existing stormwater pit on Townson road. See stormwater

quality management in section 7 for more details.

As per BCC DCP Part J, WSUD, the site does not lie within the catchment areas subject to

OSD requirements. Therefore, an OSD is not proposed to control peak flows.

6.0 STORMWATER QUANTITY MANAGEMENT

Reuse of rainwater from the proposed rainwater tanks will control the amount of runoff leaving the

site and into the council’s stormwater network.

7.0 STORMWATER QUALITY MANAGEMENT

A stormwater treatment train is proposed comprising of the following components.

7.1 RAINWATER TANKS

The rainwater tanks were designed to allow for reuse of collected rainwater for toilet flushing and

landscape and bio retention watering. Reuse has been estimated as 0.1kL/day per pan, 0.3kL/year/m2

scaled as PET-rain for landscape irrigation and 0.4kL/year/m2 scaled as PET-rain for bio retention

and swale watering. See table 1 below for further details.

Table 1 Proposed rainwater tanks

Size

Modelled

size Total re use rates

% Reuse

Met Target

Rainwater tank

1 30kL 24kL

Pans 4xa 0.4kL/day 86.07 80

Rainwater tank

2 40kL 32kL

Pans 4xa 0.4kL/day 80.25 80

Landscape 130m2 39kL/year

Rainwater tank

3 55kL 44kL

Pans 1x 0.1kL/day 85.90 80

Landscape 1150m2 345kL/year

Bio retention 120m2 48kL/year

a It is assumed that the future takeaway food premises will have 2 male and 2 female pans each

6

Stormwater Management Plan 6 Townson Road,

Marsden Park, NSW, 2765

7.2 GROSS POLLUTANT TRAPS (GPT)

7.2.1 Humeceptor

A Humeceptor STC5 has been proposed to treat runoff entering the bio retention basin from the

western side. Humeceptor’s PCSWMM calculator was used to determine the minimum humeceptor

size requirement and an STC5 was selected. The STC5 model will achieve an 89% reduction in TSS

levels as per the PCSWMM calculator. See attached report in Appendix B. The Humeceptor is located

on hardstand areas for ease of maintenance.

The Humecpetor satisfies the BCC’s requirement for treatment of total hydrocarbons.

7.2.2 SPEL StormSack

A SPEL StormSack is proposed within the overflow pit of the bio retention basin to provide pollution

control for runoff that bypasses the bio retention basin during storms with high rainfall intensities.

7.2.3 Bio-Retention Basin

A 100m2 bio-retention basin with a minimum filter area of 80m

2 is proposed. Details of the bio-

retention basin will generally be in accordance with BCC’s standard drawings with modifications as

shown in the attached civil drawings. Inflows to the bio-retention basin are via a headwall on the

western end and a surcharge pit on the eastern end. Both the headwall and the surcharge pit are as per

BCC’s standard drawings.

7.3 WATER QUALITY OUTCOME – MUSIC MODEL

A MUSIC model was prepared for the proposed treatment train. The model was prepared using the

latest MUSIC-Link data, BCC’s default MUSIC nodes and in accordance with BCC’s requirements.

See figure below for treatment train as modelled in MUSIC and Appendix C for MUSIC link report.

Figure 3 Treatment train and pollution removal as modelled in MUSIC

7

Stormwater Management Plan 6 Townson Road,

Marsden Park, NSW, 2765

The overall pollutant removal for the site has been summarised in Table 2 below. An improvement in

discharged water quality can be expected by installing the proposed treatment train.

Table 2 Treatment levels for the site

Sources Residual

Load % Reduction

Targets

(%)

TSS (kg/yr) 1120 74.5 93.3 80

TP (kg/yr) 2.06 0.71 65.6 65

TN (kg/yr) 11.2 3.96 64.8 45

GP (kg/yr) 120 0 100 90

8.0 STREAM EROSION INDEX (SEI)

The potential for stream erosion to occur at downstream waterways is determined by calculating the

‘stream erosion index’ of the development. Stream erosion index is determined by comparing the post

development flows from the site with the flows considered to be ‘stream forming’. Stream forming

flow (also known as Qcritical) is described as 25% of the 50% AEP flows of the site under natural

conditions. The procedure used to calculate SEI used is as required by BCC’s Developer Handbook

for WSUD and outlined below.

The critical flow rate was calculated as stated in BCC’s Developer handbook for WSUD. Refer to

Appendix D for detailed calculations. A generic node with a high flow bypass equivalent to the

critical flow was added to the MUSIC model immediately before the receiving node for both pre-

development and post development condition. The mean annual flows obtained from the new MUSIC

model are as follows:

Table 3 Stream erosion index

Mean Annual

Flow (Ml/yr)

Pre-Development Conditions, Qpre 0.388

Post Development Conditions, Qpost 0.230

Stream erosion index (SEI)

Qpost/Qpre 1.687

Target (As per BCC’s Developer

Handbook for WSUD) 1 - 3.5

9.0 OVERLAND FLOW PATHS

If storms higher than the design storm occur, the site is graded to allow an overland flow path to form

which protects the buildings. Overland flows will exit the site via the main entry road/ramp and

towards Townson road. Overland flows will then flow towards Bells creek.

8

Stormwater Management Plan 6 Townson Road,

Marsden Park, NSW, 2765

10.0 CONCLUSION

A system has been proposed for the control of stormwater on the subject site, which considers the

requirements for water pollution control and quantity control.

The proposed system will result in adequate environment protection and reduction in water pollutant

loads based on modelling. We believe the system satisfies the requirements of Blacktown City

Council.

9

Stormwater Management Plan 6 Townson Road,

Marsden Park, NSW, 2765

APPENDIX A – SITE PLAN AND CIVIL DRAWINGS

249°34'25"

256°04

'30"

248°39'25"

251°45'10"

174°06'20"

174°22'10"

176°09'20"

77°29'50"

2.223 ha

BY TITLE

26.565

TOWNSON ROAD

No.6

249°34'25"

256°04

'30"

248°39'25"

251°45'10"

174°06'20"

174°22'10"

176°09'20"

77°29'50"

2.223 ha

BY TITLE

26.565

TOWNSON ROAD

No.6

249°34'25"

256°04

'30"

248°39'25"

251°45'10"

174°06'20"

174°22'10"

176°09'20"

77°29'50"

2.223 ha

BY TITLE

26.565

TOWNSON ROAD

No.6

249°34'25"

256°04

'30"

248°39'25"

251°45'10"

174°06'20"

174°22'10"

176°09'20"

2.223 ha

BY TITLE

26.565

TOWNSON ROAD

No.6

10

Stormwater Management Plan 6 Townson Road,

Marsden Park, NSW, 2765

APPENDIX B – PCSWMM CALCULATOR REPORT

Humeceptor® Design Summary - 1/2

Humeceptor® DesignSummary

PCSWMM for Humeceptor®

Project InformationDate 3/08/2018Project Name Kennards HireProject Number 170322Location Marsden PArk

Designer InformationCompany Richmond + Ross Pty LtdContact Harshad

RainfallName PARRAMATTA N (MASONS DR)

State NSW

ID 6612

Years of Records 1984 to 2006

Latitude 33°47'30"S

Longitude 151°1'5"E

Notes

N/A

Water Quality ObjectiveTSS Removal (%) 85

Drainage AreaTotal Area (ha) 0.371

Imperviousness (%) 87.9

The Humeceptor® System model STC 3 achievesthe water quality objective removing 88% TSS for aRoads & Hardstand particle size distribution.

Upstream StorageStorage Discharge(cu-m) (L/s)

0 0

Humeceptor® Sizing Summary

Humeceptor® ModelTSS Removal

%STC 2 82STC 3 88STC 5 89STC 7 89STC 9 92

STC 14 93STC 18 94STC 23 95STC 27 96STC 40 97STC 50 97STC 60 98

Humeceptor® Design Summary - 2/2

Particle Size DistributionRemoving finer sediment particles (<100 microns) from runoff ensures that more of the pollutants, such ashydrocarbons and heavy metals, are captured and are not discharged into our natural waterways. Thetable below lists the particle size distribution used to define the annual TSS removal.

Roads & HardstandParticle

Size Distribution SpecificGravity

SettlingVelocity

ParticleSize Distribution Specific

GravitySettlingVelocity

µm % m/s µm % m/s0.2 0.1 2.65 0.0004

22.55 9.9 2.65 0.000599.94 40 2.65 0.0070

340.67 40 2.65 0.05241000 9.9 2.65 0.16912000 0.1 2.65 0.2870

Humeceptor® Design Notes

Humeceptor® performance estimates are based on simulations using PCSWMM for Humeceptor®and historical rainfall data.

Design estimates listed are only representative of specific project requirements based on totalsuspended solids (TSS) removal.

Only the STC2 and Multiceptor™ units are adaptable to function with a grated inlet and/or inlinepipes.Only the Multiceptor™ models STC 3 to STC 27 may accommodate multiple inlet pipes.

Inlet and outlet invert elevation differences are as follows:

Inlet and Outlet Pipe Invert Elevations DifferencesInlet Pipe

Configuration STC 2 STC 3 to STC 27 STC40 to STC60

Single inlet pipe 75 mm 25 mm 75 mm

Multiple inlet pipes 75 mm 75 mm Only one inletpipe.

Design estimates are based on stable site conditions only, after construction is completed.

Design estimates assume that the drainage network is not submerged during zero flows. Forsubmerged applications, please contact your local Humes™ Water Solutions representative for anAquaceptor™ .

Design estimates may be modified for specific spills controls (Humeceptor® EOS). Please contactyour local Humes™ Water Solutions representative for further assistance.For pricing inquiries or assistance, please contact Humes™ Water Solutions, Ph. 1300 361 601,www.humeswatersolutions.com.au

11

Stormwater Management Plan 6 Townson Road,

Marsden Park, NSW, 2765

APPENDIX C – MUSIC-LINK REPORT

Project Details

Project: 6 Townson Road, Marsden Park (KennardsHire)

Report Export Date: 16/08/2018

Catchment Name: Kennards Hire

Catchment Area: 0.786ha

Impervious Area*: 160.0%

Rainfall Station: 67035 LIVERPOOL(WHITLAM

Modelling Time-step: 6 Minutes

Modelling Period: 1/01/1967 - 31/12/1976 11:54:00 PM

Mean Annual Rainfall: 857mm

Evapotranspiration: 1261mm

MUSIC Version: 6.3.0

MUSIC-link dataVersion: 6.30

Study Area: Blacktown

Scenario: Blacktown Development

Company Details

Company: Richmond + Ross PTY LTD

Contact: Harshad

Address: Level 1, 38 Willoughby Road, Crows Nest

Phone: 02 9490 9600

Email: harshadv@richmondross.com.au

Treatment Train Effectiveness

Node: Post-Development Node Reduction

Flow 16.9%

TSS 93.3%

TP 65.6%

TN 64.8%

GP 100%

Treatment Nodes

Node Type Number

Bio Retention Node 1

Rain Water Tank Node 3

GPT Node 2

Source Nodes

Node Type Number

Urban Source Node 14

MUSIC-link Report

* takes into account area from all source nodes that link to the chosen reporting node, excluding Import Data Nodes

Comments

MUSIC modelling guidelines indicate baseflow has no effect on impervious areas. Therfore no values are needed.

NOTE: A successful self-validation check of your model does not constitute an approved model by Blacktown City CouncilMUSIC-link now in MUSIC by eWater – leading software for modelling stormwater solutions

1 of 4

Passing Parameters

Node Type Node Name Parameter Min Max Actual

Bio Bioretention (20x5) Hi-flow bypass rate (cum/sec) None None 100

Bio Bioretention (20x5) PET Scaling Factor 2.1 2.1 2.1

GPT Humeceptor Interim Blacktown Node 2013-07-19 Hi-flow bypass rate (cum/sec) None None 100

GPT SPEL StormSack Blacktown Node 2015-05-14 Hi-flow bypass rate (cum/sec) None None 0.011

Post Post-Development Node % Load Reduction None None 16.9

Post Post-Development Node GP % Load Reduction 90 None 100

Post Post-Development Node TN % Load Reduction 45 None 64.8

Post Post-Development Node TP % Load Reduction 65 None 65.6

Post Post-Development Node TSS % Load Reduction 85 None 93.3

Pre Pre-Development Node % Load Reduction None None 0

Pre Pre-Development Node GP % Load Reduction None None 0

Pre Pre-Development Node TN % Load Reduction None None 0

Pre Pre-Development Node TP % Load Reduction None None 0

Pre Pre-Development Node TSS % Load Reduction None None 0

Rain Rainwater Tank 1 % Reuse Demand Met 80 None 86.07

Rain Rainwater Tank 2 % Reuse Demand Met 80 None 80.25

Rain Rainwater Tank 3 % Reuse Demand Met 80 None 85.8977

Urban Food 1 roof (280m2) Area Impervious (ha) None None 0.028

Urban Food 1 roof (280m2) Area Pervious (ha) None None 0

Urban Food 1 roof (280m2) Total Area (ha) None None 0.028

Urban Food 2 roof (280m2) Area Impervious (ha) None None 0.028

Urban Food 2 roof (280m2) Area Pervious (ha) None None 0

Urban Food 2 roof (280m2) Total Area (ha) None None 0.028

Urban Kennards building roof (1660m2) Area Impervious (ha) None None 0.166

Urban Kennards building roof (1660m2) Area Pervious (ha) None None 0

Urban Kennards building roof (1660m2) Total Area (ha) None None 0.166

Urban Landscape behind food 1 (450m2) Area Impervious (ha) None None 0

Urban Landscape behind food 1 (450m2) Area Pervious (ha) None None 0.045

Urban Landscape behind food 1 (450m2) Total Area (ha) None None 0.045

Urban Landscape behind food 1 bypassing (70m2) Area Impervious (ha) None None 0

Urban Landscape behind food 1 bypassing (70m2) Area Pervious (ha) None None 0.007

Urban Landscape behind food 1 bypassing (70m2) Total Area (ha) None None 0.007

Urban Landscape behind food 2 (130m2) Area Impervious (ha) None None 0

Urban Landscape behind food 2 (130m2) Area Pervious (ha) None None 0.013

Urban Landscape behind food 2 (130m2) Total Area (ha) None None 0.013

Urban Landscape near bioretention (430m2) Area Impervious (ha) None None 0

Urban Landscape near bioretention (430m2) Area Pervious (ha) None None 0.043

Urban Landscape near bioretention (430m2) Total Area (ha) None None 0.043

Urban Landscape on ramp (140m2) Area Impervious (ha) None None 0

Urban Landscape on ramp (140m2) Area Pervious (ha) None None 0.014

Only certain parameters are reported when they pass validation

NOTE: A successful self-validation check of your model does not constitute an approved model by Blacktown City CouncilMUSIC-link now in MUSIC by eWater – leading software for modelling stormwater solutions

2 of 4

Node Type Node Name Parameter Min Max Actual

Urban Landscape on ramp (140m2) Total Area (ha) None None 0.014

Urban Landscape on ramp bypassing (350m2) Area Impervious (ha) None None 0

Urban Landscape on ramp bypassing (350m2) Area Pervious (ha) None None 0.035

Urban Landscape on ramp bypassing (350m2) Total Area (ha) None None 0.035

Urban Pavement (2500m2) Area Impervious (ha) None None 0.25

Urban Pavement (2500m2) Area Pervious (ha) None None 0

Urban Pavement (2500m2) Total Area (ha) None None 0.25

Urban Pre-dev landscape (5840m2) Area Impervious (ha) None None 0

Urban Pre-dev landscape (5840m2) Area Pervious (ha) None None 0.584

Urban Pre-dev landscape (5840m2) Total Area (ha) None None 0.584

Urban Pre-dev pavement (1200m2) Area Impervious (ha) None None 0.12

Urban Pre-dev pavement (1200m2) Area Pervious (ha) None None 0

Urban Pre-dev pavement (1200m2) Total Area (ha) None None 0.12

Urban Pre-dev roof (820m2) Area Impervious (ha) None None 0.082

Urban Pre-dev roof (820m2) Area Pervious (ha) None None 0

Urban Pre-dev roof (820m2) Total Area (ha) None None 0.082

Urban Ramp Pavement (1570m2) Area Impervious (ha) None None 0.157

Urban Ramp Pavement (1570m2) Area Pervious (ha) None None 0

Urban Ramp Pavement (1570m2) Total Area (ha) None None 0.157

Only certain parameters are reported when they pass validation

NOTE: A successful self-validation check of your model does not constitute an approved model by Blacktown City CouncilMUSIC-link now in MUSIC by eWater – leading software for modelling stormwater solutions

3 of 4

Failing Parameters

Node Type Node Name Parameter Min Max Actual

Urban Food 1 roof (280m2) Baseflow Total Nitrogen Mean (log mg/L) 0.32 0.32 0.11

Urban Food 1 roof (280m2) Baseflow Total Phosphorus Mean (log mg/L) -0.82 -0.82 -0.85

Urban Food 1 roof (280m2) Baseflow Total Suspended Solids Mean (log mg/L) 1.1 1.1 1.2

Urban Food 2 roof (280m2) Baseflow Total Nitrogen Mean (log mg/L) 0.32 0.32 0.11

Urban Food 2 roof (280m2) Baseflow Total Phosphorus Mean (log mg/L) -0.82 -0.82 -0.85

Urban Food 2 roof (280m2) Baseflow Total Suspended Solids Mean (log mg/L) 1.1 1.1 1.2

Urban Kennards building roof (1660m2) Baseflow Total Nitrogen Mean (log mg/L) 0.32 0.32 0.11

Urban Kennards building roof (1660m2) Baseflow Total Phosphorus Mean (log mg/L) -0.82 -0.82 -0.85

Urban Kennards building roof (1660m2) Baseflow Total Suspended Solids Mean (log mg/L) 1.1 1.1 1.2

Urban Pre-dev roof (820m2) Baseflow Total Nitrogen Mean (log mg/L) 0.32 0.32 0.11

Urban Pre-dev roof (820m2) Baseflow Total Phosphorus Mean (log mg/L) -0.82 -0.82 -0.85

Urban Pre-dev roof (820m2) Baseflow Total Suspended Solids Mean (log mg/L) 1.1 1.1 1.2

Only certain parameters are reported when they pass validation

NOTE: A successful self-validation check of your model does not constitute an approved model by Blacktown City CouncilMUSIC-link now in MUSIC by eWater – leading software for modelling stormwater solutions

4 of 4

12

Stormwater Management Plan 6 Townson Road,

Marsden Park, NSW, 2765

APPENDIX D – STREAM EROSION INDEX CALCULATIONS

Time of concentration and design intensity

Tc = 0.76A0.38 where Tc is in hours and A in km2

Tc = 0.76 ×7860

1000 × 1000

0.38

= 0.1205hrs = 7.23mins

Design Tc adopted = 7mins

I7min2yr

= 88mm/hr (Obtained from BCC′s Enginering Guidelines Table 3)

Coefficient of runoff

C2 = FF2 x C10

FF2 = 0.74 (As per ARR 1987, Book 2, Vol 1, Table 5.1)

C10 = 60% (As per ARR 1987, Book 2, Vol 2, Fig 5.1)

C2 = 0.74 x 0.6 = 0.444

50% AEP (Q2) peak flow rate

Q2 = 0.000278 x C2 x I7min2yr

x A

Q2 = 0.000278 x 0.444 x 88 x 7860

Q2 = 85.4l/s

Stream forming flow rate (Qcritical)

Qcrit = 25%Q2 (As per BCC’s DCP, Part J)

Qcrit = 0.25 x 85.4 = 21.35l/s