STORMWATER MANAGEMENT REPORT · to the existing site discharge point on the North East corner of the property via existing pipe and surface inlet pit system, detention basin and bio-retention

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ACOR Consultants Pty Ltd (ACN 079 306 246) (ABN 40 079 306 246)

STORMWATER MANAGEMENT REPORT Homebush Apartments Stage 2 -21 Parramatta Rd, Homebush, NSW

Prepared for: Hyside Projects Subtwo Pty Ltd

Acor Project Number: SY190976

Document no: SY190976_SWMR

Issue no: Revision E

P:\SY19\SY190976\Reports\Stormwater Management Report\SY190976_SMR_Rev E_200107.docx Page 2 of 14

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Table of Contents

1 Executive Summary ........................................................................................ 3

2 Introduction ..................................................................................................... 3

2.1 Purpose of Report ............................................................................. 3

2.2 Project Description............................................................................. 3

2.3 Guidelines and Standards.................................................................. 3

3 Existing Conditions .......................................................................................... 4

3.1 Existing Site ....................................................................................... 4

3.2 Existing Stormwater Drainage ........................................................... 4

4 Proposed Development ................................................................................... 5

4.1 Proposed Site Development .............................................................. 6

4.2 Proposed Stormwater Drainage Layout ............................................. 6

4.3 Design of Proposed Drainage System ............................................... 6

5 Conclusion ...................................................................................................... 6

Appendices

Drawings ........................................................................................... 7

C1.01 Proposed Ground Floor Stormwater Plan ......................................... 8

C2.01 – Existing OSD/Bio-retention Details ..................................................... 9

C2.02—Existing Ground Floor As Built Plans ................................................ 10

C2.03—Existing Rain Water Reuse Tank details ........................................... 12

C3.01 – Proposed Soil Erosion and Sedimentation Plan ............................... 13

MUSIC Model .................................................................................. 14

Revision Date Purpose Prepared By Approved By

A 19/11/2019 Preliminary for client review Robert Gruber Robert Gruber

B 28/11/2019 For DA Submission Approval Robert Gruber Robert Gruber

C 03/12/2019 Updated For DA Submission Approval

Robert Gruber Robert Gruber

D 05/12/2019 Updated For DA Submission Approval


E 07/01/2020 Updated Scope- For DA Submission Approval



1 Executive Summary

This Stormwater Management Report has been prepared by ACOR Consultants for the proposed Stage 2 mixed

use development located at 21 Parramatta Rd, Homebush NSW.

This report documents the methodology involved in determining the existing design of the stormwater and water

quality treatment train and the new stormwater management works required for the new building works.

The report finds that the Stage 1 installation of rainwater tanks, a bio-retention system and a on site detention

system, constructed in in 2017, for the site containing blocks A, B and provision for block C , will achieve the

required water quality performance requirements as required by the Strathfield Consolidated Development

Control Plan (2005) and the Strathfield Council Stormwater Management Code (1994) for this Stage 2 Block C

development.

This report is based on:-

1. Acor Consultants stormwater management plans SY13-0538

2. Stratrsurv “As Built” Drawings dated 17th August 2017 (Refer appendix A)

3. SJB Stage 2 Concept Design Report dated 5th November 2019

2 Introduction

2.1 Purpose of Report

This Stormwater Management Report has been prepared by ACOR Consultants for the proposed multi storey

building development located at 21 Parramatta Rd, Homebush NSW.

This report documents the methodology involved in determining the existing stormwater management system

and proposed stormwater drainage system for the stage 2 development, including the integration with existing

site stormwater quantity and quality management.

2.2 Project Description

ACOR Consultants has been engaged by Hyside Projects Subtwo Pty Ltd to prepare a Stormwater Management

Plan and Water Quality Modelling report for the proposed development located at Cnr Powell St and Parramatta

Rd, Homebush, NSW.

The proposed Stage 2 construction site is located within the existing Stage 1 mixed use development site

completed in August 2017..

The existing Stage 1 site contains 4 levels of basement carparking, podium level retail and open public and

community areas and residential buildings known as Block A and Block B

This Stage 2 development will consist of construction of 24 storey building from ground podium level, consisting

of ground level retail and multi storey serviced and residential apartments

2.3 Guidelines and Standards

The stormwater system is to be designed to the local authority and water authority requirements:

Strathfield Council Stormwater Management Code

Strathfield Council Consolidated Development Control Plan

Water Sensitive Urban Design (WSUD) is to be designed to the following documents:

‘Part N of Strathfield Consolidated Development Control Plan 2005 – Water Sensitive Urban Design

(WSUD)’ published by Strathfield Council

Strathfield Council WSUD Reference Guideline’ published by Strathfield Council


3 Existing Conditions

3.1 Existing Site

The site bound to the North by M2 Motorway, to the East by Council parkland and a M2 motorway entry ramp, to the South by Parramatta Rd and to the West by Powell St.

Proposed new building fronts Parramatta Road and its street address is to be known as 21 Parramatta Road, Homebush.

3.2 Existing Stormwater Drainage

The site incorporates an approved stormwater management system which included the future stage 2 works. Proposed Stage stormwater management system will connected directly to the existing approved system,. Please refer to

Appendix A drawings for details.


4 Proposed Development


4.1 Proposed Site Development

The proposed development will include the construction of a residential complex as well as a number of retail

outlets and open space at the ground floor level. The stormwater system will be designed to convey the 100 year

ARI storm event for the property.

The proposed Stormwater management layout will be as shown in Appendix A.

4.2 Proposed Stormwater Drainage Layout

Stormwater from the proposed building roof and podium areas will be directed through piped system connecting

to the existing site discharge point on the North East corner of the property via existing pipe and surface inlet pit

system, detention basin and bio-retention system completed in 2017

The proposed stormwater system is designed to convey up to a 1 in 100 year stormwater event. Refer Appendix

A for Drawings.

4.3 Design of Proposed Drainage System

4.3.1 On-Site Detention

The site currently includes an on-site detention basin of volume 141m3 located at the North East border of the

property The existing layout is as shown in Appendix A.

The existing site also includes 2 rainwater reuse tanks sized at 9.250kl each which are located in Basement 2

collecting roof water from existing Blocks A and B, also shown in Appendix A.

4.3.2 Maintenance Plan

Provision for litter bins, signage, education and regular sweeping of the accessible drainage catchments will

continue to help to reduce litter loads generated by the site.

The recommended maintenance regime for the tertiary treatment processes has been instigated by the property

manager and ensures suitable pollutant removal efficiencies of the systems.

4.3.3 Stormwater Quality Management

The proposed drainage system has been designed in accordance with the Strathfield Council requirements. The

requirements are found in the Strathfield Council publication ‘Part N of Strathfield Consolidated Development

Control Plan 2005 – Water Sensitive Urban Design (WSUD)’.

The following existing water quality targets are achieved as set by the council guidelines:

90% reduction in the post development mean annual load of total gross pollutant (greater than 5 mm).

85% reduction in the post development mean annual load of Total Suspended Solids (TSS).

60% reduction in the post development mean annual load of Total Phosphorus (TP).

45% reduction in the post development mean annual load of Total Nitrogen (TN).

4.3.4 Stormwater Quality Treatment Train

The existing rainwater resue tanks, a bio-retention system and a detention basin to treat the stormwater within

the post-development design.

The proposed roof and podium area stormwater runoff will be directed into the existing stormwater drainage

system connecting the existing bio-retention and detention systems with the urban surface runoff before being

discharged to stormwater connection point indicated above.

4.3.5 MUSIC Modelling

The MUSIC software package was used in 2016 for the Stage 1 development works, to model the water quality

for the post-developed site, which included both Stage 1 and future Stage 2 to calculate the pollutant loads from

the development and the effectiveness of the treatment train. The perviousness of catchment areas is based on

the design as detailed in Appendix A. Roofs, roads and pathways were all designated as 100% impervious,

alhough there was a modes section of deep soli planting contained withi the Stage 1 development works.

The model was run to calculate the reduction in the mean annual loads for the proposed development. A

summary of the results are shown below in Table 3.1. Full MUSIC results are attached in Appendix B.

Table 3.1 – MUSIC Output – Post Developed Mean Annual Loads for the Homebush Apartments

Parameter In Out % Removal

Required

% Removal

Achieved

Total Suspended Solids (kg/yr) 1320 152 85% 88.4%

Total Nitrogen (kg/yr) 18.7 9.9 45% 47.1%

Total Phosphorous (kg/yr) 2.64 0.993 60% 62.4%

Gross Pollutants (kg/yr) 166 0.00 90% 100%

As can be seen in table 3.1 above, the Suspended Solids, Nitrogen, Phosphorus and Gross Pollutants are all

reduced by the treatment train proposed for this development. These results meet the requirements as set by the

Strathfield Council publication ‘Part N of Strathfield Consolidated Development Control Plan 2005 – Water

Sensitive Urban Design (WSUD)’.

5 Conclusion

The existing Stage 1 stormwater management system was designed and constructed to cater for the proposed

future Stage 2 development.

Proposed Stage 2 does not increase impervious or pervious area to the site and proposed roof water downpipes

and podium area drainage will directly interconnect to the existing site stormwater management system,

incorporating approved rainwater reuse tanks, bio-retention and detention systems which will continue to

improve stormwater quality discharge to Council system.

The above measures achieve the requirements as set out by ‘Part N of Strathfield Consolidated Development

Control Plan 2005 – Water Sensitive Urban Design (WSUD)’ in conjunction with the ‘Stormwater Management

Code’ both published by Strathfield Council.


Drawings


C1.01 Proposed Ground Floor Stormwater Plan


C2.01 – Existing OSD/Bio-retention Details


C2.02—Existing Ground Floor As Built Plans



C2.03—Existing Rain Water Reuse Tank details


C3.01 – Proposed Soil Erosion and Sedimentation Plan


MUSIC Model

Figure 1 - MUSIC Model Layout and Results for the Stage1 and Stage 2Homebush Apartment Complex

Documents

STORMWATER MANAGEMENT REPORT · to the existing site discharge point on the North East corner of the property via existing pipe and surface inlet pit system, detention basin and bio-retention