DESIGN REPORT ON SITE STORMWATER AND SOIL MANAGEMENT

www.lp-consulting.com.au

T: +61 2 9223 4444

M: +61 416 256 955

A: Suite 2, Level 8, 15 Castlereagh Street Sydney NSW 2000

P: P.O. Box 814 Kensington NSW 1465

E: [email protected] ACN: 165 018 968 ABN: 61 165 018 968

• DESIGN AND PROJECT MANAGEMENT

• CIVIL ENGINEERING

• WATER AND WASTEWATER ENGINEERING

• BUILDING AND INFRASTRUCTURE

• HYDRAULIC AND FIRE SERVICES

• SYDNEY WATER REGISTERED

WATER SERVICING COORDINATOR,

DESIGNER AND PROJECT MANAGER

• EXPERT TECHNICAL ADVICE

DESIGN REPORT ON SITE STORMWATER AND SOIL MANAGEMENT Ref: 2015-0524 Tuesday, 12 April 2016 EQUITY SITE HOLDINGS PTY TD C/- Lallees Enterprises Pty Ltd 1/108a Irrubel Road NEWPORT NSW 2106 Attention – Mr Leon Fredkin ([email protected]) RE: - 110 ADDISON ROAD, MARRICKVILLE

SITE STORMWATER MANAGEMENT FOR DEVELOPMENT APPLICATION

INTRODUCTION AND OVERVIEW

This design report addresses the Site Stormwater Drainage Management for the proposed Development

Application. LP Consulting Australia (LP Consulting) has prepared the following Drawings in support of the

drawings prepared by Architects Nicholas & Associates (AN & A): -

Site Stormwater Drainage

DA-STW-001 Title Sheet and Locality Plan

DA-STW-002 Legend, Abbreviations and Drawing List

DA-STW-003 General Notes

DA-STW-004 Erosion and Sediment Control Plan

DA-STW-005 Erosion and Sediment Control Details

DA-STW-101 Site Stormwater Drainage - Basement Plan

DA-STW-102 Site Stormwater Drainage - Ground Floor Plan

DA-STW-103 Site Stormwater Drainage - Level 1 Plan

DA-STW-104 Site Stormwater Drainage - Level 2 Plan


DA-STW-105 Site Stormwater Drainage – Level 3 Plan

DA-STW-106 Site Stormwater Drainage – Loft Plan

DA-STW-107 Site Stormwater Drainage - Roof Plan

DA-STW-201 Site Stormwater Drainage – Basement Pump Out Pit Details

DA-STW-202 Site Stormwater Drainage – Stormwater Treatment and OSD Tank Details

DA-STW-203 Site Stormwater Drainage – Rainwater Reuse Tank Details

The design plans address the following key areas:-

1. Constraints setting the Finished Floor Level (FFL) and the site levels across the proposed

development.

2. The roof stormwater collection system is reticulated separate to the in ground surface drainage and

drains to a rainwater re-use tank.

3. All pavement areas are contained and drained through a Water Sensitive Urban Device (WSUD)

device and into an On-Site Detention (OSD) Tank.

4. Drainage from the site reticulates into the Council stormwater system located in Illawarra Road and

is limited to pre-development flows by the discharge control pit.

We refer to previous studies undertaken and the proposal methodology for the Site Stormwater Management

for the above site.


THE EXISTING SITE

The existing site is on the corner of Illawarra Road and Addison Road, the site is bounded on the southern

and eastern boundaries by existing two (2) storey residential developments. Handley Street provides an

additional street frontage at the south eastern corner of the site.

The attached Site Plan prepared by AN & A shows that:

Addison Road falls from RL 9.96m to RL 9.71m from west to east along the road frontage;

Illawarra Road falls from RL 9.88m to RL 9.32m from north to south along the road frontage;

Handley Street falls away from the site to the east from RL 8.93 at the south eastern corner of the site

boundary;

The site falls gradually from north western corner to south eastern corner from RL 10.10m to RL 8.93m

N


FLOOD AFFECTED LAND

Reference is made to the Marrickville Council (Council) Development Control Plan (DCP 2011) Section 2.22

– Flood Management and Flood Mapping which explains the extent of flood affected land.

Figure 1 below shows that the site is located within the flood planning area for overland flow. This requires

local overland flow to be assessed for the 1 in 100 Year storm event round the development.

Figure 1 – Flood Planning Area (Overland Flow) Map

110 Addison Road


Figure 2 below shows that the proposed development is located within the flood liable land area. Flood

Liable Land is identified as land possibly subject to the Probable Maximum Flood Level (PMF) of the Cooks

River.

Figure 2 – Flood Liable Land Map

The Flood Planning Area requirements are more stringent than the Flood Liable Area requirements and as

such will be referenced throughout this report.

Reference should be made to the previous Flood Study submitted for this site which addresses the flooding

issues and determines appropriate Flood levels for the 100 year Average Recurrence Interval storm, which

has led to the determination of Floor levels.

110 Addison Road


PROPOSED FINISHED FLOOR LEVELS

The proposed Finished Floor Level (FFL) is required to be set to satisfy Council’s DCP 2011 Section 2.22

Flood Management. Council requires 500mm freeboard between the overland flow levels and the FFL of the

proposed building ground floor. The ground floor is a mixture of retail, commercial and residential space.

The following initiatives are proposed for the development:-

The FFL for the proposed development will be set at RL 10.60m AHD which is 500mm above the

highest boundary level of RL 10.10m AHD at the intersection of Illawarra Road and Addison Road.

The proposed basement carpark entry ramp at the south eastern corner of the development off

Handley Street will have a threshold of RL 9.70m which is greater than 500mm above the boundary

level of RL 8.95m at Handley Street.


SITE STORMWATER SYSTEM

Refer to the attached information including:-

Drawing DA-STW-102 for site grading and levels

Drawing DA-STW-102 for site stormwater layout

The site in-ground stormwater system has been designed to capture the 1 in 100 Year Annual Recurrence

Interval (ARI) storm event. This system collects and drains all paved areas around the proposed building. A

site grading plan has been prepared and stormwater pits and pipes located to drain the site from north to south

The in-ground site stormwater system drains through a Water Sensitive Urban Design (WSUD) treatment

device into an On-Site Detention (OSD) tank before being discharged from site into Council’s drainage system.

These elements of the site stormwater management plan are discussed in further detail later in the report.

ROOF WATER SYSTEM

Refer to attached information including:-

Drawing DA-STW-102 for site stormwater layout

Drawing DA-STW-106 and 107 for roof drainage layout

The roof of the proposed building is a flat roof with pitched metal sections falling to gutters at the loft level. The

roof water for the proposed development is collected and discharged through Rainwater Outlets in the flat

roofed areas and eaves gutters in the pitched roof areas through a series of DN100mm downpipes to ground

level and draining at the podium level to the proposed rainwater tank located under the external common area.

This system is detailed further on design plans DA-STW-102 to STW-107.

All downpipes and overflows have been designed to accommodate the 1 in 100 year ARI storm event and in

accordance with AS3500 Part 3 and the Building Code of Australia.


BASEMENT PUMPOUT SYSTEM


Drawing DA-STW-101 for Basement Pumpout Pit location

Drawing DA-STW-201 for Basement Pumpout Pit details

All exposed areas of the site that drain to the basement are drained to a central pump-out pit located in the

south western corner of the basement.

The storage volume has been calculated based on the 1 in 100 year ARI storm event for a 2 hour storm

duration with an intensity of 34.6mm/hr. The storage control volume provided between the top and bottom

water levels is 2.8m3.

ON SITE STORMWATER DETENTION (OSD)


Drawing DA-STW-102 for OSD tank location

Drawing DA-STW-202 for OSD tank details

Council’s DCP 2011 Section 2.25 states that all multi-unit residential developments require OSD with the pre-

development flow for sites greater than 1000m2 to assume ‘state of nature’ when determining the pre-

development flow.

Storm events ranging from 1 in 5 Year to 1 in 100 Year ARI are to be controlled and limited to the pre-

development Peak Site Discharge (PSD) as outlined in Supplement 2 of the Stormwater and On Site Detention

Code.


An ILSAX model has been completed using DRAINS, an urban stormwater runoff and routing software

program. The site area has been determined at 1500m2 with a 100% impervious ratio for the post development

catchment. The following design criteria have been included in determining the size of the OSD tank:-

Depth of OSD Tank 0.55m

Volume of OSD Tank 23m3

Orifice Diameter 240mm

High Early Discharge Crest Level RL 9.20m

High Early Discharge Co-efficient 1.6

OSD Overflow Level RL 9.45m

The table below presents a comparison of the pre and post development flows from the DRAINS analysis and

demonstrates that the post development flows are limited to the pre-development flows for storm events

ranging from 1 in 5 Year to 1 in 100 Year ARI:

STORM EVENT

(ARI)

PEAK SITE DISCHARGE (L/sec)

PRE-DEVELOPMENT POST DEVELOPMENT

5 45 43

10 54 44

20 66 46

50 73 49

100 82 59

The OSD Tank has been provide as a suspended reinforced concrete tank in the south western corner of the

basement with an outlet connection to the existing Council kerb entry pit located in Illawarra Road.


RAINWATER REUSE


Drawing DA-STW-102 for rainwater tank location

Drawing DA-STW-203 for rainwater tank details

Reference is made to Council’s DCP 2011 Section 2.17 Water Sensitive Urban Design in relation to rainwater

reuse. For mixed use developments compliance with BASIX and/or installation of fittings and fixtures to meet

the following Water Efficiency Labelling and Standards (WELS) and rainwater tanks to meet as seen below


A water balance has been undertaken using the MUSIC Numerical model, to optimise the rainwater usage

for the proposed development while also ensuring compliance with BASIX and/or WELS. Climate statistics

from the Sydney – 6 minute template have been utilised in the analysis.

Rainwater reuse has been allocated to the following:-

Irrigation of landscape gardens and trees in planters;

Car washing;

WC flushing in residential units.

The irrigation will be of the landscape gardens within the common area and the trees located within the

planters. The assumption has been made that garden areas requires irrigation at a rate of 20mm/m2/week

and trees within planters requiring 15L/day/tree. This equates to a total water usage of 400L/day.

Car washing will occur in the washing bay at the south eastern corner of the development. It has been

assumed that 4 cars per day will be washed at 40L/car. This equates to a total of 160L/day allocated to car

washing

In addition to these rainwater reuse has been allocated to WC flushing for all residential properties within the

development. At 4L/flush with a population of 60 people assuming equal numbers male and female the total

usage per day is 700L/day.

The total water usage allocated to rainwater reuse is 1.26kL/day.

The proposed development has a total roof area of 1100m2 which will drain to a 24,000L rainwater tank

located underneath the external common area alongside the OSD tank as seen on drawing DA-STW-102.

When this system is analysed with climate statistics it provides a total rainwater reuse for irrigation of 99%.

The table below presents the water balance results from MUSIC with the reuse demand highlighted.


ON SITE STORMWATER TREATMENT


Drawing DA-STW-102 for WSUD treatment device locations

Drawing DA-STW-202 for Stormfilter details

The requirement for On Site Stormwater treatment is discussed in Council’s DCP 2011 Part 2.17. Section

2.17.4 and outlines the percentage reductions required for urban developments:

MUSIC modelling has been conducted to demonstrate that the targets set by Council have been met by the

proposed treatment train.

The stormwater treatment train layout is shown on drawing DA-STW-102 and allows for the following:-

5 off Enviropods at collection pits draining to the OSD tank;

One off 24,000L rainwater tank collecting all roof water from the proposed development for irrigation,

car washing and WC flushing purposes;

A Stormwater 360 Stormfilter with 15 off cartridges.


The results from the MUSIC analysis are presented below showing the total percentage reduction achieved

by the proposed treatment train described above.

The proposed stormwater quality treatment train as outlined above results in compliance against the

percentage reduction rate required to be achieved by Council.

DESIGN REPORT ON SITE STORMWATER AND SOIL MANAGEMENT

Documents

Transcript of DESIGN REPORT ON SITE STORMWATER AND SOIL MANAGEMENT