Urban Main Drainage Standard - watercorporation.com.au · Design Standard No. DS66 Urban Main...

Acquisition Group Infrastructure Design Branch

Design Standard No. DS66

Urban Main Drainage Standard

VERSION 2

REVISION 0

30 JUNE 2011

Design Standard DS 66


Uncontrolled if Printed of 92

Ver 2 Rev 0

© Copyright Water Corporation 1991-2011

FOREWORD

The intent of Design Standards is to specify requirements that assure effective design and delivery of fit for

purpose Water Corporation infrastructure assets for best whole-of-life value with least risk to Corporation

service standards and safety. Design standards are also intended to promote uniformity of approach by asset

designers, drafters and constructors to the design, construction, commissioning and delivery of water

infrastructure and to the compatibility of new infrastructure with existing like infrastructure.

Design Standards draw on the asset design, management and field operational experience gained and

documented by the Corporation and by the water industry generally over time. They are intended for

application by Corporation staff, designers, constructors and land developers to the planning, design,

construction and commissioning of Corporation infrastructure including water services provided by land

developers for takeover by the Corporation.

Nothing in this Design Standard diminishes the responsibility of designers and constructors for applying the

requirements of WA OSH Regulations 1996 (Division 12, Construction Industry – consultation on hazards

and safety management) to the delivery of Corporation assets. Information on these statutory requirements

may be viewed at the following web site location:

http://www.commerce.wa.gov.au/WorkSafe/Content/Industries/Construction/Further_information/National_

standard_for_construction.html

Enquiries relating to the technical content of a Design Standard should be directed to the Principal Engineer,

Water Drainage Civil & Standards Section, Infrastructure Design Branch. Future Design Standard changes,

if any, will be issued to registered Design Standard users as and when published.

Manager, Infrastructure Design Branch

This document is prepared without the assumption of a duty of care by the Water Corporation. The document is not

intended to be nor should it be relied on as a substitute for professional engineering design expertise or any other

professional advice.

Users should use and reference the current version of this document.

© Copyright – Water Corporation: This standard and software is copyright. With the exception of use permitted by the

Copyright Act 1968, no part may be reproduced without the written permission of the Water Corporation.




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DISCLAIMER

This Standard is intended solely for application to the acquisition of water infrastructure in Operating Areas in

Western Australia where the Water Corporation has been licensed to provide water services subject to the terms

and conditions of its Operating License.

This Standard is provided for use only by a suitably qualified professional design engineer who shall apply the

skill, knowledge and experience necessary to understand the risks involved and undertake all infrastructure design

and installation specification preparation work.

Any interpretation of anything in this Standard that deviates from the requirements specified in the project design

drawings and construction specifications shall be resolved by reference to and determination by the design

engineer.

The Corporation accepts no liability for any loss or damage that arises from anything in the Standard including

loss or damage that may arise due to the errors and omissions of any person.




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REVISION STATUS

The revision status of this standard is shown section by section below:

REVISION STATUS

SECT. VER./

REV.

DATE PAGES

REVISED

REVISION DESCRIPTION RVWD. APRV.

1 1/0 02.98 All New Version SS

1 1/2 05.02 1.3 2.1.4 updated SS JD

1 1/2 05.02 1.4 Table 1.1 revision status

amended

SS JD

1 1/2 05.02 1.5 Table 1.3 revision status

amended

SS JD

N/A 2/0 30.06.11 All Removed and amalgamated into

this section and section 8

SS PF


1 2/0 30.06.11 All New version, Reformatted,

renamed section 1Edited clauses

1.1 & 1.3

SS PF



renamed section 2 and revised

SS PF

4A 1/0 02.98 All New Version SS

4A 1/1 03.00 All Amended to comply with

Developers Manual

SS JD


renamed section 3 and deleted

clauses in Developers Manual

SS PF

4B 1/0 02.98 All New Version SS

4B 1/1 03.00 4B.3 1.5-1.9 amended to comply with

Developers Manual

SS JD


Developers Manual

SS JD

4B 1/1 03.00 4B.13 4.1.1-4.1.3,4.2.2 amended to

comply with Developers Manual

SS JD

4B 1/1 03.00 4B.14 4.3.1,4.3.2 amended to comply

with Developers Manual

SS JD


Developers Manual

SS JD

4B 1/1 03.00 4B.17 7 amended to comply with

Developers Manual

SS JD




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SECT. VER./

REV.

DATE PAGES

REVISED



renamed section 4 Edited

clauses. Revised cl 4.1(a) & (c),

4.2.2, 4.2.4 para.1 and 4.2.6(c).

Added cl 4.2.11.2 to 6, 4.2.11.8,

4.2.12 & 4.3.1

SS PF

4C 1/0 02.98 All New Version SS

4C 1/1 03.00 4C.4 2.1 and 2.2 amended to comply

with Developers Manual

SS JD


renamed section 5.Amended cl

5.1(a) to (c), 5.2 and 5.3

SS PF

5A 1/0 02.98 All New Version SS

5A 1/2 05.02 5A.6 1.11 included revised version of

AR&R

SS JD

5A 1/2 05.02 5A.7 2.1 included revised version of

AR&R

SS JD

5A 1/2 05.02 5A.9 2.1.6 included revised version of

AR&R

SS JD

5A 1/2 05.02 5A.13 2.2.1 included revised version of

AR&R

SS JD

5A 1/2 05.02 5A.14 2.2.2(c) and 2.2.2(f) included

revised version of AR&R

SS JD

5B 1/0 02.98 All New Version SS

5B 1/1 03.00 5B.3 1. amended to comply with

Developers Manual

SS JD


renamed section 6. Edited Cl

6.2.2 ©(i), 6.2.3 & 6.7.1.

Amended Cl 6.1(a) to (d),(j)

&(n),6.2.1.1, 6.2.1.5(a) &(b),

6.2.2.2, 6.2.2.2(d))(ii),

6.2.2.2(f)(i), 6.2.3.2, 6.3.1(f),

6.3.2.2(c), 6.3.2.3(b), 6.3.2.4,

.3.4(b), 6.3.15.1, 6.4.1(g), Table

6.6, 6.4.4, 6.4.5, 6.6.2(b),(c) &(f),

6.6.7(d), 6.6.12 &13, 6.7.4 (b)

&(n), 6.7.5.2, 6.8.2(a) to

(f)6.8.5(d), 6.8.6(b),6.8.7,and

6.8.7.1.

Added Cl 6.1(k) & (l), 6.7.2,

6.7.3.1, 6.11, 6.12 and 6.13.

SS PF





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SECT. VER./

REV.

DATE PAGES

REVISED



renamed section 7. Edited cl 7.1,

7.2(h) & 7.6(k). Amended cl

7.2(a) to (c), 7.9(d)(iv),7.4(f),

7.7.1(a)(i) and Table 7.2

SS PF


renamed section 8 & revised

SS PF

Appln 1/0 02.98 All New Version SS

Appln 1/1 03.00 1 Last para - update SS JD


renamed section 9. Address

amended

SS PF

Gloss 1/0 02.98 All New Version SS

Gloss 1/1 03.00 G.1 Access Chamber - update SS JD

Gloss 1/1 03.00 G.3 Design Engineer, Developer,

Developers Manual, Engineer,

Engineering firm – update

SS JD

Gloss 1/1 03.00 G.5 MH or AC, Principal - update SS JD


renamed section 10. Edited,

Deleted AAMGL, NAASRA,

artifical wetland & constructed

wetland. Added Edge

Protection, Department of

Water and CGL.

SS PF

11 2/0 30.06.11 All Deleted SS PF




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Design Standard No. DS66 Urban Main Drainage Standard

CONTENTS Section Page

1 Introduction.....................................................................................................................................11 1.1 Purpose.............................................................................................................................................11 1.2 Scope.................................................................................................................................................11 1.3 Criteria.............................................................................................................................................11 1.4 Standard Drawings .........................................................................................................................11 1.5 Brand Names ...................................................................................................................................11 1.6 Design Standards.............................................................................................................................11 1.7 Construction Standards..................................................................................................................11 1.8 Access to Existing Water Corporation Systems...........................................................................11 1.9 Unauthorised Works.......................................................................................................................12 1.10 Funding of Projects.........................................................................................................................12

2 Strategic Planning and Conceptual Design ..................................................................................13

3 Submission of Design ......................................................................................................................16

4 Construction ....................................................................................................................................17 4.1 Introduction.....................................................................................................................................17 4.2 Construction Requirements ...........................................................................................................17

4.2.1 General .........................................................................................................................17 4.2.2 Occupational Safety and Health ...................................................................................17 4.2.3 Setting Out....................................................................................................................17 4.2.4 General Earthworks ......................................................................................................18 4.2.4.1 Clearing and Protection of Remnant Vegetation..........................................................18 4.2.4.2 Dieback Control............................................................................................................18 4.2.4.3 Topsoil Management ....................................................................................................18 4.2.4.4 Dust Control .................................................................................................................19 4.2.4.5 Erosion and Sediment Control......................................................................................19 4.2.4.6 Weed Control................................................................................................................19 4.2.4.7 Fill over pipes or conduits ............................................................................................19 4.2.4.8 Open drains and compensating basins..........................................................................20 4.2.4.9 Levees...........................................................................................................................20 4.2.4.10 Tolerances ....................................................................................................................20 4.2.5 Trench Excavation........................................................................................................20 4.2.6 Dewatering ...................................................................................................................20 4.2.7 Installation and Bedding...............................................................................................20 4.2.8 Laying and Jointing of Reinforced Concrete Pipes and Box Culverts.........................21 4.2.8.1 General .........................................................................................................................21 4.2.8.2 Tolerances ....................................................................................................................21 4.2.9 Infiltration.....................................................................................................................21 4.2.10 Protection of Other Services.........................................................................................21 4.2.11 Reinforced Concrete Structures....................................................................................21 4.2.11.1 General .........................................................................................................................21 4.2.11.2 Cement..........................................................................................................................21 4.2.11.3 Aggregate......................................................................................................................22 4.2.11.4 Water ............................................................................................................................22 4.2.11.5 Sand ..............................................................................................................................22 4.2.11.6 Reinforcement ..............................................................................................................22 4.2.11.7 Formwork .....................................................................................................................22 4.2.11.8 Concrete Finishes .........................................................................................................22 4.2.11.9 Curing ...........................................................................................................................23




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4.2.11.10 Tolerances ....................................................................................................................23 4.2.11.11 Construction joints .......................................................................................................23 4.2.12 Brickwork .....................................................................................................................23 4.2.13 Backfill .........................................................................................................................23 4.2.13.1 General .........................................................................................................................23 4.2.13.2 Backfill for reinforced concrete pipes ..........................................................................23 4.2.13.3 Backfill adjacent to structures ......................................................................................24 4.2.14 Restoration....................................................................................................................24

4.3 Inspection Requirements During Construction ...........................................................................24 4.3.1 General .........................................................................................................................24 4.3.2 Required Site Inspections .............................................................................................24

4.4 Testing Requirements .....................................................................................................................24 4.4.1 Line and Level ..............................................................................................................24 4.4.2 Infiltration.....................................................................................................................24 4.4.3 Substandard work or materials .....................................................................................25

5 As Constructed Requirements .......................................................................................................26 5.1 Introduction.....................................................................................................................................26 5.2 Details...............................................................................................................................................26

5.2.1 Drawings.......................................................................................................................26 5.3 Submission of As Constructed Drawings......................................................................................27

6 Design Criteria ................................................................................................................................28 6.1 Introduction.....................................................................................................................................28 6.2 Drainage Design ..............................................................................................................................29

6.2.1 Hydrological Design.....................................................................................................29 6.2.1.1 Design average recurrence interval for minor systems. ...............................................29 6.2.1.2 Design average recurrence interval for major systems.................................................29 6.2.1.3 Level of service for a minor system .............................................................................29 6.2.1.4 Level of service for a major system .............................................................................30 6.2.1.5 Coefficients of Runoff..................................................................................................30 6.2.1.6 Rainfall intensity - frequency - duration ......................................................................31 6.2.1.7 Design methods ............................................................................................................31 6.2.2 Hydraulic Design..........................................................................................................36 6.2.2.1 General .........................................................................................................................36 6.2.2.2 Specific criteria for the design of components of a drainage system...........................36 6.2.3 Water Sensitive Urban Design .....................................................................................40 6.2.3.1 Issues ............................................................................................................................40 6.2.3.2 Multidisciplinary Approach .........................................................................................40

6.3 Drainage Pipes and Conduits.........................................................................................................41 6.3.1 General .........................................................................................................................41 6.3.2 Installation and Bedding...............................................................................................41 6.3.2.1 General .........................................................................................................................41 6.3.2.2 Foundations ..................................................................................................................42 6.3.2.3 Backfill .........................................................................................................................42 6.3.2.4 Reinforced concrete pipe..............................................................................................42 6.3.3 Cover to Pipes or Conduits...........................................................................................42 6.3.4 Concrete Encasement ...................................................................................................43 6.3.5 Location of Drainage Pipes or Conduits in Private Property .......................................43 6.3.6 Location of Drainage Pipes or Conduits in Road Reserves .........................................43 6.3.7 Location of Drainage Pipes or Conduits in Vested Reserves.......................................43 6.3.8 Requirements for Easements for Drainage Pipes or Conduits .....................................44 6.3.9 Requirements for Reserves for Drainage Pipes or Conduits ........................................44 6.3.10 Crossing of Roads, Railways and Other Services ........................................................44 6.3.10.1 General .........................................................................................................................44 6.3.10.2 Services passing through drainage pipes or conduits ...................................................45 6.3.10.3 Siphons under services .................................................................................................46




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6.3.11 Junctions.......................................................................................................................46 6.3.12 Pipes, Fittings and Joints ..............................................................................................46 6.3.13 Splay Pipe Bends. .........................................................................................................46 6.3.14 Box Culverts and Link Slabs........................................................................................47 6.3.14.1 General .........................................................................................................................47 6.3.14.2 Installation ....................................................................................................................47 6.3.14.3 Cast in-situ base slabs...................................................................................................47 6.3.14.4 Joints.............................................................................................................................48 6.3.14.5 Bends ............................................................................................................................48 6.3.15 Subsoil Drains ..............................................................................................................48 6.3.15.1 General .........................................................................................................................48 6.3.15.2 Pipes .............................................................................................................................48 6.3.15.3 Filters............................................................................................................................48 6.3.15.4 Box culverts..................................................................................................................48

6.4 Access Chambers.............................................................................................................................48 6.4.1 General .........................................................................................................................48 6.4.2 Construction Materials for Access chambers...............................................................50 6.4.3 Brick Access Chambers................................................................................................50 6.4.4 Precast Concrete Access chambers ..............................................................................50 6.4.5 Access chamber Covers................................................................................................51 6.4.6 Bends and Junctions at Access Chambers....................................................................51

6.5 Culverts ............................................................................................................................................51 6.6 Open Drains.....................................................................................................................................51

6.6.1 General .........................................................................................................................51 6.6.2 Guidelines for Open Drains Accessible to the Public ..................................................52 6.6.3 Guidelines for Open Drains in Fenced Reserves..........................................................53 6.6.4 Location of Open Drains in Private Property...............................................................54 6.6.5 Location of Open Drains in Road Reserves .................................................................54 6.6.6 Location of Open Drains in Reserves Vested to Other Authorities .............................54 6.6.7 Requirements for Easements for Open Drains .............................................................54 6.6.8 Land Requirements for Reserves for Open Drains.......................................................54 6.6.9 Crossing Railways and Other Services.........................................................................55 6.6.9.1 Crossing of railways .....................................................................................................55 6.6.9.2 Crossings of buried services.........................................................................................55 6.6.9.3 Crossings below above-ground services.......................................................................56 6.6.10 Services Parallel To Open Drains ................................................................................56 6.6.11 Protection of Existing Flora .........................................................................................56 6.6.12 Fencing and Edge Protection........................................................................................57 6.6.12.1 Fencing .........................................................................................................................57 6.6.12.2 Edge protection.............................................................................................................57 6.6.13 Location of Fencing and Edge Protection ....................................................................58 6.6.13.1 Trapezoidal open drains ...............................................................................................58 6.6.13.2 Structures accessible to the public ...............................................................................59

6.7 Structures.........................................................................................................................................59 6.7.1 General .........................................................................................................................59 6.7.2 Type Drawings .............................................................................................................59 6.7.3 Design...........................................................................................................................59 6.7.3.1 Materials .......................................................................................................................59 6.7.3.2 General Requirements ..................................................................................................59 6.7.4 Trash Racks, Safety Screens and Guard Rails .............................................................60 6.7.5 Road Bridges, Access Crossings and Occupational Crossings ....................................61 6.7.5.1 General .........................................................................................................................61 6.7.5.2 Design...........................................................................................................................61

6.8 Compensating Basins......................................................................................................................61 6.8.1 Design...........................................................................................................................61 6.8.2 General .........................................................................................................................62




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6.8.3 Location........................................................................................................................63 6.8.4 Land Requirements for Compensating Basins .............................................................63 6.8.5 Requirements for Easements for Compensating Basins...............................................63 6.8.6 Fenced Compensating Basins.......................................................................................63 6.8.7 Unfenced Compensating Basins...................................................................................64 6.8.7.1 Ornamental Lakes and Landscaped Basin....................................................................64 6.8.7.2 Dry Basins ....................................................................................................................65

6.9 Connections......................................................................................................................................66 6.9.1 General .........................................................................................................................66 6.9.2 Silt Trapping of Lateral or Property Drains .................................................................66 6.9.2.1 General .........................................................................................................................66 6.9.2.2 Connecting drains up to and including 600 mm nominal diameter..............................66 6.9.2.3 Connecting drains larger than 600 mm nominal diameter ...........................................67

6.10 Operational Requirements for Construction over or near Existing Water Corporation Drains

...........................................................................................................................................................67 6.11 Engineering Design Process ...........................................................................................................67 6.12 Environmental and Social Analysis...............................................................................................67 6.13 Safety Consideration.......................................................................................................................68

6.13.1 Safety............................................................................................................................68 6.13.2 Risk Assessment ...........................................................................................................69 6.13.3 Safety in Design ...........................................................................................................69 6.13.4 Signage .........................................................................................................................70 6.13.5 Water Corporation Standards .......................................................................................70

6.14 Services Crossing Water Corporation Land ................................................................................70 6.14.1 General .........................................................................................................................70 6.14.2 Location of Markers .....................................................................................................70 6.14.3 Marker Specification ....................................................................................................70

7 Design Drawings Criteria...............................................................................................................72 7.1 Introduction.....................................................................................................................................72 7.2 Drawing Standards .........................................................................................................................72 7.3 Locality Plan....................................................................................................................................74 7.4 Design Data Plan .............................................................................................................................75 7.5 Major Event Plan............................................................................................................................78 7.6 Longitudinal Section.......................................................................................................................79 7.7 Access Chambers, Splay Bends, Junctions and Intersecting Services .......................................80

7.7.1 Access chambers ..........................................................................................................80 7.7.2 Splay Bends ..................................................................................................................81 7.7.3 Junctions.......................................................................................................................81 7.7.4 Intersecting Services.....................................................................................................81

7.8 Structures.........................................................................................................................................81 7.9 Compensating Basins......................................................................................................................82 7.10 Open Drains and Natural Watercourses ......................................................................................82

8 Drawings ..........................................................................................................................................84 8.1 Metropolitan Main Drainage, Urban Main Drainage Standard -Drawings .............................84 8.2 Reference Drawings ........................................................................................................................85

9 Application for Connection to Stormwater Main Drain.............................................................86

10 Glossary............................................................................................................................................87




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1 Introduction

1.1 Purpose

The Urban Main Drainage Standard sets out requirements and provides guidance for Design

Engineers involved in the design and construction of drainage assets for the Water Corporation within

the Perth Metropolitan Region Planning Scheme. The Standard is aimed at ensuring that the main

drainage assets of the Water Corporation provide developments with effective flood protection up to

the Water Corporation’s level of service. The Standard also acknowledges principles of total water

management and encourages designs that integrate works within the urban environment to enhance

water conservation and minimise the transport of pollutants to valuable receiving waters.

1.2 Scope

The standard covers the criteria and rules applicable to the design and construction of new drainage

systems as well as extensions and modifications to existing systems.

1.3 Criteria

The criteria in the standard have been derived from those of the former Metropolitan Water Authority,

Public Works Department and Water Authority of Western Australia and modified and interpreted to

conform to the recommendations of Australian Rainfall and Runoff, Revised Edition 1997. The

criteria are subject to change from time to time.

1.4 Standard Drawings

The drawings contain information which is complementary to that contained in the text and shall

therefore be read in conjunction with the corresponding parts of the standard.

Design Engineers and Contract Superintendents shall ensure that they have the latest issue of the

drawings.

1.5 Brand Names

Where a brand name is indicated, a similar material or product may be used if approved by the Water

Corporation.

1.6 Design Standards

The Design Engineer shall be responsible for the design of the works irrespective of the requirements

of the standard.

1.7 Construction Standards

Where compliance with Australian or Water Corporation Standards is required, it represents the

minimum acceptable standard and does not preclude the use of materials and workmanship of a higher

standard.

1.8 Access to Existing Water Corporation Systems

Water Corporation installations shall not be opened or entered even for inspection or survey purposes

without the approval of the Asset Manager or an authorised officer from Perth Region on each

occasion.




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1.9 Unauthorised Works

The construction of Main Drainage works before the approval of a submission in accordance with the

requirements of the standard may prejudice the reimbursements of monies for any works so

constructed or delay the clearance of the diagrams of survey for a subdivision.

1.10 Funding of Projects

A proponent shall consult the Water Corporation during conceptual development of a drainage

proposal to determine the funding requirements.




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2 Strategic Planning and Conceptual Design

The purpose this section is to provide brief outline on how the strategic planning and concept design

for urban drainage are developed in Western Australia and the roles and responsibilities of different

agencies.

In November 2005, the Water Resources Cabinet Sub-Committee endorsed a framework for the

management of drainage functions across Western Australia. The roles and accountabilities proposed

for both the Department of Water and the Water Corporation build upon this endorsed framework.

The framework identified the role of the Department of Water in establishing the Arterial Water Plan

(Drainage) identifying the land requirements for flood and drainage management.

The West Australian State Government is committed to the management of drainage to:

• protect the health of waterways, wetlands and marine environments;

• facilitate appropriate land use changes; and

• assess the potential of drainage water as a resource.

The Department of Water is responsible for strategic drainage policy and strategic drainage

planning across Western Australia.

Drainage planning is required to manage the complex drainage and water management issues and

meet the following objectives:

• Provide protection from flooding caused by stormwater or inundation from seasonal or long

term groundwater level fluctuations

• Protect valued natural resources (such as wetlands, waterways and recreation areas) and

receiving water bodies

• Maintain or improve the quality of surface and groundwater systems

• Facilitate opportunities for water conservation, re-use and recycling

• Assess the potential for drainage water in a catchment to be used as a resource

The drainage service providers, the Water Corporation and the Local Government are responsible for

infrastructure planning, design and delivery of the urban drainage service.

The Water Corporation is a licensed service provider for urban drainage within the Perth Metropolitan

Region Scheme (MRS) and provides a main drainage services to an estimated 40% of the MRS

catchment with local government providing the drainage services to the catchment that connects to the

main drains.

Local governments manage the total drainage services in the remaining areas of Perth that require

urban drainage management, and provide urban drainage services in country towns across Western

Australia.




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The objectives for integrating land and water planning are that Water planning should accommodate

and integrate with land use planning. Increasingly, it is intended that water planning should precede

land use planning. This will not only provide an important natural resource management context for

land planning, but will identify resource opportunities, constraints and incompatible land use

activities.

To meet the requirements of Department of Water and Department of Planning, the Better Urban

Water Management Document was published by the West Australian Planning Commission and the

Department of Planning in consultation with the Department of Water. It provides guidance on the

implementation of State Planning Policy 2.9 Water Resources which is a requirement of the State

Water Strategy for Western Australia. Figure 4 of the Better Urban Water Management Document

illustrates integrating water planning with land planning process.

Figure 2.1 illustrates the drainage planning framework that implements drainage planning from the

broad strategic level to the more detailed planning to ensure effective integration with land use

planning processes. It also conforms to the requirements within the framework outlined in the State

Water Plan and aligns with other related water planning documents e.g. Regional Water Plans and

Drainage and Water Management Plans.

Water Corporation’s requirement should be obtained by the developer for any development within

Water Corporation Drainage Operating areas at the preliminary planning stage to determine the

detailed drainage requirements to protect the drainage system.




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LAND PLANNINGDRAINAGE PLANNING

State Water Plan

(State Drainage Strategy)

Regional Water Plans

(Strategic Drainage

Issues)

Drainage & Water

Management Plan

Arterial Drainage

Infrastructure Planning/Design

(WC / LG)

Input to Drainage

Planning

Service Providers

DPI /WAPC

DoW

Developers

LEGEND

Area of planning

influenced

Planning Influence

Planning Hierarchy

DoW

Service Provider Developer

DoW DoP / WAPC

State Planning Strategy

(inc State Drainage Strategy)

Regional Strategies

(inc Strategic Drainage Issues)

Regional SchemeLocal Planning

Strategy

Local Planning

Scheme

(TPS)

Local Structure Plan

Regional/Sub

Regional/District

Structure Plan

Subdivision Plan

(incl Water Sensitive Urban Design &

Local Drainage Planning)

(Developer / LG)

Drainage /Waterway

Objectives

Roles/

Responsibilities

Base Data

Modeling

Cross Agency

Drainage

Committee

Environmental

Assessment

Stakeholder

Consultations

Abbreviations

Department of Water DoW

Western Australian Planning Commission WAPC

Department of Planning DoP

Local Government LG

Water Corporation WC

Figure 2.1: Planning framework integrating drainage planning with land planning processes.




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3 Submission of Design

The submission of the engineering design of urban main drainage works shall be in accordance with

the requirements set out in the Developers Manual.

Although the Developer’s Manual treats a submission as though it is to be prepared by a Design

Engineer from outside the Water Corporation, it shall be followed, and adhered to as far as

practicable, by any Water Corporation officer preparing a design for urban main drainage works.




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4 Construction

4.1 Introduction

(a) This section of the standard refers to works being undertaken by a Contractor that will form

part of the Water Corporation’s main drainage system. Construction of works undertaken by

the Water Corporation shall also follow the general principles of these requirements.

(b) The Design Engineer shall be responsible for ensuring compliance with the requirements of this

section of the standard.

(c) The Design Engineer shall ensure that any Contract is administered under the provisions of

General Conditions of Contract AS4000-1997 (version Mar 2010) as amended by the Water

Corporation and available in read only format from the Water Corporation’s website at

http://www.watercorporation.com.au/ under: Your Business / Suppliers / Terms & conditions of

contract., and this part of the standard. Unless stated otherwise the requirements of this section

of the standard shall be applied where AS 4000 - 1997 and this section of the standard are in

conflict.

(d) The Design Engineer shall be responsible for ensuring that the Contractor is informed of the

requirements of this section of the standard.

4.2 Construction Requirements

The following are the minimum requirements for the construction of Water Corporation drainage

works:

4.2.1 General

(a) Tolerances for specific purposes have been specified in the following clauses. Tolerances for

works other than those specified in the following clauses are:-

Horizontal ± 0.10 m Vertical ± 0.05 m.

(b) Compaction tests on sand material shall be carried out with a Standard Perth Sand

Penetrometer.

4.2.2 Occupational Safety and Health

The Contractor shall ensure that the works are carried out and maintained in compliance with the

legislative requirements relating to occupational safety and health and the Water Corporation’s

requirements available in Water Corporation’s website at http://www.watercorporation.com.au/

under: Your Business / Suppliers/Heath safety and environment for contractors/OSH information.

4.2.3 Setting Out

(a) Pipe drains, access chambers, open drains and compensating basins shall be set out in

accordance with the alignments and levels shown on the working drawings. Setting out

tolerances are:


(b) The concept of the works and the alignments (both vertical and horizontal) shown on the

drawings shall not be altered in any way without the prior approval of the Manager, Asset

Management in Perth Region.




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4.2.4 General Earthworks

The following and the information in Water Corporation’s web site

http://www.watercorporation.com.au under Your Business/Suppliers/Heath Safety and Environment

for Contractors/Environmental information sets the minimum requirements for managing the

environmental impact for general earthworks.

4.2.4.1 Clearing and Protection of Remnant Vegetation

(a) Clearing of the site shall be restricted to the area of the works and shall be carried out with a

minimum of disturbance to existing trees and remnant native vegetation. Existing trees shall

not be disturbed for temporary works such as access tracks or spoil areas. Where practicable

and appropriate, existing vegetation within the area of the works should be retained to help

stabilise the soil and control erosion.

(b) Clearing of mature trees for construction convenience should be avoided where possible. For

example, the clearing of trees overhanging a drain, so that there is continuous clearance for an

excavator to operate, may be convenient for construction/maintenance but is not essential and is

therefore considered to be undesirable. Mature trees should be retained unless their presence

interferes with the function and operation of the finished works.

4.2.4.2 Dieback Control

(a) When works are carried out within an identified dieback area, special provisions need to be

employed to minimise the risk of spreading the fungus and soil contaminated with the fungus

and its spores.

(b) Where possible, vehicles and plant should avoid entering dieback areas. If entry is necessary,

then all plant and equipment shall be cleaned free of soil prior to entering and prior to leaving

the site.

(c) Soil shall not be transported from known or suspected dieback areas unless:

• measures are taken to avoid loss of soil in transit, and

• the destination site is already infected with the dieback fungus.

4.2.4.3 Topsoil Management

(a) Following clearing, topsoil and remnant vegetation debris within the area of the works shall be

removed and stockpiled on site for later use in rehabilitation.

(b) To reduce potential losses from wind and water erosion, topsoil stockpiles shall not exceed one

metre in height.

(c) Topsoil stockpiles should be temporarily stabilised with a cover of vegetation to minimise

erosion during construction.

(d) Stockpiles shall be placed away from drainage lines.

(e) Runoff flowing from above the site shall be diverted around or away from the stockpiles.

(f) Topsoil infested with weeds or dieback infested material shall not be used in rehabilitation or

revegetation works. This material shall be removed off site to an approved site.




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4.2.4.4 Dust Control

(a) The area of the works should be limited to minimise disturbance and potential dust hazard.

(b) Traffic movement shall be controlled in areas of disturbed soils.

(c) Bare soil areas may be progressively revegetated or watered to reduce dust.

(d) Where a site is exposed to strong winds, additional measures such as windbreaks, wind fences

and/or soil stabilisation techniques may need to be employed.

(e) All works shall follow the Department of Environmental Protection’s guidelines for prevention

of dust and smoke pollution.

4.2.4.5 Erosion and Sediment Control

(a) An Erosion And Sediment Control Plan shall be prepared prior to commencement of the works.

The plan shall address the compatibility of the site’s features with the proposed works and shall

outline the measures to be employed to minimise soil erosion and control sediment deposition.

The plan shall cover the construction phase and include the initial operating period of the

works.

(b) A stable temporary drainage system shall be established through the site and clean runoff water

should be diverted around the works.

(c) Work shall be carried out in accordance with the Erosion and Sediment Control Plan.

(d) Construction activities should follow a minimal clearing policy by disturbing the smallest area

possible at each stage of the works

(e) Early rehabilitation and revegetation should occur after completion of works in any area.

(f) Unnecessary vehicle movements shall be restricted to reduce wear and soil disturbance.

4.2.4.6 Weed Control

(a) Intact native vegetation should be retained and protected where possible.

(b) Topsoil from weed infested areas should not be stockpiled or spread in areas less affected by

weeds.

(c) Weed infested topsoil shall, where possible, be removed from site and disposed of at a licenced

land fill. If this is not possible such material shall only be used on areas of the site that are

already infested with weeds...

(d) Where intact natural vegetation must be cleared, its topsoil, containing native seeds and other

supportive organisms is preferred for rehabilitation of the works.

4.2.4.7 Fill over pipes or conduits

Where general filling is required above the natural ground surface it shall be placed and compacted

before the construction of the drain unless the top of the drain is 1.0 m or more below the natural

surface. The fill may then be placed after the drain has been constructed and the drain shall be re-

inspected on completion of the filling.




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4.2.4.8 Open drains and compensating basins

(a) Open drains and compensating basin banks berms and channels shall be constructed to the

grades and levels shown on the drawings.

(b) Where banks or berms are to be filled, the fill (which may be on site material), shall be

compacted in 300 mm (max) layers to give a minimum reading of 5 blows per 300 mm.

4.2.4.9 Levees

Levees shall be constructed from selected material of low permeability, compacted as specified by the

Design Engineer on the drawings.

4.2.4.10 Tolerances

Tolerances for general earthworks are:

Horizontal ± 0.10 m Vertical ± 0.05 m

4.2.5 Trench Excavation

The length of excavation shall not exceed 300 metres at any one time on any work face.

This requirement may be further restricted by Local Authority regulations.

4.2.6 Dewatering

(a) The need for dewatering shall be carefully considered to ensure adverse impacts on the adjacent

environment are minimised. These impacts include effects on vegetation, fauna, soils and

property:

• through lowering of the groundwater table in the vicinity of the dewatering operation. (e.g.

drying of vegetation)

• through raising of the groundwater table in the vicinity of the discharge point. (e.g. water

logging of crops, tree roots and building foundations)

• through raising of flows and water levels in watercourses downstream of the discharge

point. (e.g. flooding of vegetation and fauna habitat)

• through increasing turbidity and pollution of downstream watercourses. (e.g. waterborne

silt smothering wetland vegetation and blinding aquatic fauna)

(b) Where dewatering of works is necessary, the discharged water shall be collected in a temporary

settling pond to remove particulate matter prior to discharge to the drainage system. The

degree of settlement required will be dependent on the characteristics of the soil being

dewatered and the method of dewatering adopted. Water shall not be discharged into a drain

unless it is of similar or better quality than the water normally flowing in the drain.

(c) Procedures developed in accordance with the Water Corporation’s guidelines titled “Water

Corporation Acid Sulphate Soil and Dewatering Management Strategy” shall be adopted for

dewatering of areas where acid sulphate soil is present.

4.2.7 Installation and Bedding

The installation and bedding of drainage pipes and conduits, including box culverts shall be in

accordance with Clause 6.3.2 and Clause 6.3.14 of section 6 of the standard.




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4.2.8 Laying and Jointing of Reinforced Concrete Pipes and Box Culverts.

4.2.8.1 General

(a) Drainage pipes and conduits, including box culverts, shall be laid to line and grade and jointed

in accordance with Clause 6.3.2 and Clause 6.3.14 of section 6 of the standard.

(b) Pipe reinforcement exposed by on site cutting of pipes shall be coated with an epoxy coating

approved by the Water Corporation.

4.2.8.2 Tolerances

(a) The horizontal deviation of any drainage pipe, conduit or box culvert drain shall not exceed 25

mm from the true alignment. There shall be no obvious sharp changes of direction.

(b) The maximum deviation from grade shall not exceed 10 mm above or 20 mm below true grade

line.

(c) The grade of any drainage pipe, conduit or box culvert drain shall not be flatter than 1.10 times

its allowable minimum grade.

(d) Invert levels at structures shall be a maximum of ± 10 mm from the designed invert shown on

the drawing.

4.2.9 Infiltration

(a) Reinforced concrete pipes, access chambers and structures shall be free from infiltration that is,

or in the opinion of the representative of the Water Corporation has the potential for,

transporting soil or other deleterious material into the drain. Minor infiltration from hairline

cracks in reinforced concrete pipes, structures and access chambers that in the opinion of the

representative of the Water Corporation will heal autogenously, may be permitted.

(b) An access chamber shall be considered to be leaking if any beads of water which appear on the

internal wall of the access chamber grow or run or drops of water which appear in the access

chamber in any joint fall from the joint at the rate of more than one drop per minute.

4.2.10 Protection of Other Services

Without limiting the requirements of AS 4000 - 1997 the protection of the services of other

authorities shall be in accordance with Clause 6.3.3 and Clause 6.3.10 of section 6 of this standard.

4.2.11 Reinforced Concrete Structures

4.2.11.1 General

(a) Structural concrete shall be to Australian Standard AS 3600 - 2009, Concrete structures.

(b) The use of concrete additives is restricted and approval for their use shall be obtained from the

Water Corporation in each instance.

(c) The use of sealants or similar products to correct leakage as a result of construction faults is not

permitted.

4.2.11.2 Cement

(a) All cement used shall be Portland cement in accordance with AS 3972 and obtained from an

approved manufacturer.




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(b) Cement shall be delivered to the site fresh and in sealed bags and are stored in a weather-proof

shed until such time that it is to be used. Any bag showing signs of deterioration or setting shall

be rejected.

4.2.11.3 Aggregate

(a) Fine aggregate shall be well graded, clean, sharp and free from clay and organic impurities in

accordance with AS 1141.

(b) Coarse aggregate shall be crushed granite or diorite clean and free from all impurities and dust in

accordance with AS 1141.

(c) The maximum particle size shall not exceed 20mm.

4.2.11.4 Water

Water for use in concrete and mortar shall be of potable quality, free from any impurities harmful

to concrete, mortar or steel.

4.2.11.5 Sand

(a) Sand for mortar shall be crushed stone or natural sand free from all deleterious substances and

have a uniform grading.

(b) Sand for bedding or backfilling shall be clean sand free from roots, clay or any deleterious matter.

4.2.11.6 Reinforcement

(a) Reinforcement shall conform to AS/NZS 4671.

(b) All reinforcement shall be free from rust and other foreign matter.

4.2.11.7 Formwork

(a) Formwork shall conform to Australian Standard AS 3610 - 1990, Formwork for concrete.

(b) Formwork shall not be stripped less than two days after the pouring of the concrete. Where

formwork is stripped from suspended slabs after two days such slab shall be shored for a

minimum of a further five days. All props shall be removed prior to construction on or

backfilling over suspended slabs.

4.2.11.8 Concrete Finishes

Formed concrete finishes shall be in accordance with AS3610 as follows:

(a) Normally exposed to view e.g. headwalls, ............................. Class 3

wing walls etc

(b) Not normally exposed e.g. inner walls ................................... Class 4

of access chamber etc

(c) Permanently concealed (buried)............................................. Class 5

Top of base slabs of structures shall be float finished to uniform texture.




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4.2.11.9 Curing

(a) Curing of structural concrete shall continue for not less than 7 days from the time of casting.

• Vertical surfaces - Formwork shall be left in position for a minimum of 2 days and a

suitable curing compound shall be applied to all stripped and exposed surfaces within 2

hours of removal of formwork.

• Horizontal surfaces - the area shall be flooded with 25 mm of water for a minimum of 7

days OR a suitable curing compound shall be applied to all stripped and exposed surfaces

within 2 hours of removal of formwork.

(b) Alternative methods of curing shall not be used without the approval of the appropriate Asset

Inspector in Perth Region.

4.2.11.10 Tolerances

Overall tolerances for finished structures are:


4.2.11.11 Construction joints

Construction joints shall not be made without the approval of the Design Engineer.

4.2.12 Brickwork

(a) Bricks shall be hard well burnt, pressed or wire cut clay brick in accordance with AS/NZS 4455.

The bricks shall have minimum characteristic unconfined compressive strength of 20 MPa and

absorb when saturated, not more than 10% of their own weight of water. Brickwork shall be in

accordance with AS3700.

(b) Bricks shall be of uniform shape and size, carefully conveyed and unloaded at the site. No chipped

or broken bricks shall be used, and no pieces of brick to be used except where necessary as

closures.

4.2.13 Backfill

4.2.13.1 General

(a) Backfill shall be compacted to achieve a minimum reading of 8 blows per 300 mm under all

trafficable areas and 5 blows per 300 mm elsewhere or compacted to a dry density equal to or

better than the dry density of the surrounding undisturbed soil.

(b) The Contractor shall be responsible for ensuring that the required compaction is obtained.

Particular care shall be taken along side boundaries of properties and under roads.

(c) The results of any compaction tests shall be submitted to the Water Corporation’s Asset

Inspector at the site inspection of the relevant section of drain.

4.2.13.2 Backfill for reinforced concrete pipes

The minimum requirements for backfill for the installation of reinforced concrete pipes should be in

accordance with Australian Standard 3725 – 2007, "Design for installation of buried concrete pipes"

and Australian Standard 3725 Supplement 1 – 2007, "Design for installation of buried concrete pipes -

Commentary".




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4.2.13.3 Backfill adjacent to structures

Backfill shall not be placed adjacent to any access chamber within 5 days of completion of the

brickwork or adjacent to any structure within 5 days of the final concrete pour.

4.2.14 Restoration

The Contractor shall ensure that property damaged during the course of the works shall be reinstated,

at the Contractor's cost, to a condition as near as practicable to that existed prior to the

commencement of work.

4.3 Inspection Requirements During Construction

4.3.1 General

General inspection requirements are included in the Developers Manual.

4.3.2 Required Site Inspections

(a) The Contractor shall request a site inspection by the Water Corporation at the following stages

of construction:

(i) When testing for line and level in accordance with Clause 4.4.1 of this Section is to be

carried out.

(ii) Before drains have been concrete encased.

(iii) When pipe laying is complete.

• Reinforced concrete pipes shall be inspected before any fill material is placed.

• Other pipes may be covered to a depth of 150 mm to reduce thermal movement, but

the Water Corporation may direct that sections of the pipe be uncovered, at the

Contractor's expense, to allow for inspection.

(iv) After trenches and excavations have been backfilled and testing for infiltration in

accordance with Clause 4.4.2 of this section is possible.

(v) After construction of the bases of access chambers and structures.

(vi) After completion of access chambers and structures.

(vii) When the Contractor considers that the works have reached the stage of Practical

Completion.

4.4 Testing Requirements

4.4.1 Line and Level

(a) The line and level of a drain shall be checked.

(b) Pipe drains shall be tested for straightness in the horizontal and vertical directions and for

freedom from obstructions. The contractor shall test in the presence of the Water Corporation

representative to the tolerances set out in Clause 4.2.3 of this section.

4.4.2 Infiltration

Pipe drains, structures and access chambers shall be checked for infiltration, in accordance with the

requirements of Clause 4.2.9, a minimum of seven days after the Works have been backfilled and the

dewatering equipment has been removed.




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4.4.3 Substandard work or materials

Any substandard work or materials shall be made good at the Contractor's expense.




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5 As Constructed Requirements

5.1 Introduction

(a) This section of the standard sets out requirements for the production and submission of as

constructed information for gravity drains and associated works.

(b) The as constructed information shall consist of drawings marked up to reflect the constructed

situation of the works.

(c) As constructed information shall be transferred from hard copy to CAD drawings in accordance

with Water Corporation’s Design Standard DS80- WCX CAD Standard, Water Corporation

eXternal (WCX) Manual and project brief.

(d) The As Constructed drawings, in the required form, shall have been accepted by the Water

Corporation before:-

• a Final Inspection clearance certificate will be issued.

and/or

• works will be taken over by the Water Corporation.

and/or

• a letter of clearance will be issued for a subdivision.

and/or

• Water Corporation contributions towards works will be paid.

5.2 Details

5.2.1 Drawings

(a) As Constructed drawings shall be prepared in accordance with the requirements of Section 14

of Water Corporation’s Design Standard DS80. Minor variations to size and shape of access

chambers and structures are to be shown as amendments on the design drawings. Major

variations to the design may require a new drawing to reflect the As Constructed situation.

(b) The As Constructed drawings shall include at least:-

• Corrected distances along the route of the drain.

• Invert levels at access chambers and structures.

• Levels for top of access chambers and top of structures.

• The position of access chambers and structures by cadastral ties (or by MGA94 coordinates

where cadastral ties are not possible).

• Finished contours for compensating basins and open drains.

• The actual storage capacity, to the design TWL, of compensating basins noted in the design

data on the drawing.

• Bedding information of piped drains and culverts.




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• Junction locations.

• The extents of remnant vegetation and planted vegetation.

• Variations from design.

5.3 Submission of As Constructed Drawings

(a) As Constructed drawings shall be submitted in accordance with the requirements of Section 14 of

Water Corporation’s Design Standard DS80 and Water Corporation’s Developers’ Manual

(b) Where a drain crosses land or infrastructure controlled by any other authority a copy of the signed

As Constructed drawings shall be forwarded to the relevant controlling authority.




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6 Design Criteria

6.1 Introduction

This part of the standard sets out the criteria to be used in the design of drainage works and includes

some operational requirements concerning construction over or near existing Water Corporation

drains:

(a) Development of the concept design shall be based on best planning practices supplemented

with best management practices appropriate to the design. The design shall address the issues

of water conservation and landscape protection as well as the more traditional drainage issues

of peak flow attenuation, discharge capacity, safety, environmental risks, operation and

maintenance. The design should consider ways to maximise the “degree of naturalness” and the

aesthetics of the drainage system as a resource for the community. Reference should be made

to the Department of Water’s Stormwater Management Manual for Western Australia.

(b) All new designs shall comply with the Water Corporation's Drainage planning for the area with

due regard to the Department of Water’s arterial drainage strategy. Provision shall be made to

connect adjoining areas to the design catchment, where feasible.

(c) New designs should incorporate appropriate elements of Water Sensitive Urban Design as

outlined in Department of Water’s Stormwater Management Manual for Western Australia...

(d) Where possible, new main drains should be integrated with landscaped open space. As part of

the Water Corporation’s commitment to the environment, natural water courses and vegetation

within and immediately fringing a natural water course shall be retained where feasible. The

governing hydrological characteristics of the water course shall be preserved where practicable.

(e) When the Water Corporation determines that the development of an area has an impact on the

Water Corporation's existing drainage system, the extent of the redesign required shall have the

objective of minimising the impact on that system.

(f) It is essential that any new drainage works, and the impact of those works on the existing

system and its environment, is examined under both level of service design criteria and major

event conditions. Any areas at risk from a major event should be highlighted on the design data

plan. As part of a design philosophy of guided land use, the Design Engineer shall recommend

minimum building levels on the Major Event Plan for the areas at risk from the major event.

Responsibilities associated with the major event are outlined in Clause 6.2.1.4 of this section.

(g) For the redevelopment of existing urban areas the Developer shall provide on site flow

compensation, if required by the Water Corporation, to ensure that the critical duration peak

discharge into the main drain does not exceed the current design magnitude. Appropriate Water

Sensitive Urban Design (WSD) elements and water resource management principles shall be

incorporated, where practicable, in the redevelopment design.

(h) Survey data used for design shall be checked against the invert level of the existing drain at the

point of connection.

(i) Drainage schemes shall be designed so that land will be drained by gravity in preference to a

pumped system.

(j) Drains shall be designed to serve all land within the topographical catchment of the drain.

• In low lying areas where shallow water tables occur, drainage design should incorporate

opportunities to enhance the local/regional landscape. For example, to provide a “drainage

waterway” which not only adds recreational and wildlife habitat values, but assists with




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water quality improvement and re-use initiatives provided this does not reduce the flood

conveyance capacity of the main drain.

• On higher land where there is greater separation from the water table, drainage design

should focus on site retention and infiltration as a water conservation measure.

(k) Assessment on the need for geotechnical investigations shall be made at appropriate stage of

the design and necessary investigations shall be carried out in accordance with AS 1726 –

Geotechnical site investigations.

(l) Assessment on the need for acid sulphate soil investigations shall be made at appropriate stage

of the design and necessary investigations shall be carried out to meet the requirements in

Water Corporation’s guidelines titled “Water Corporation Acid Sulphate Soil and Dewatering

Management Strategy”.

(m) The Water Corporation currently uses INFOWORKS for hydrological and hydraulic modelling.

Use of this model is preferred in cases where the Water Corporation requires the analysis or

design to be based on computer modelling. Under these circumstances, the use of other

computer models will require approval from the Manager, Infrastructure Planning Branch.

6.2 Drainage Design

6.2.1 Hydrological Design.

The hydrological design of the Water Corporation's drainage systems shall be based on the guidelines

recommended in Book 8 of AUSTRALIAN RAINFALL AND RUNOFF, VOLUME 1 Edition 1997.

6.2.1.1 Design average recurrence interval for minor systems.

Table 6.1 is representative of the appropriate Design Average Recurrence Intervals (ARI) for minor

systems. It should be noted that designs prior to 1986 may have used an average recurrence interval

less than five years. For proposed developments in existing areas contact should be made with the

Manager, Infrastructure Planning Branch through the Manager, Development Services Branch to

determine design criteria.

Table 6.1: Minor System Design Average Recurrence Intervals

Category of Development Design ARI

Rural areas, POS & Regional Open Space 5 years

Urban Residential 5 years

Commercial/Industrial 10 years

Compensated commercial/industrial/urban

residential

10 years

6.2.1.2 Design average recurrence interval for major systems

The Design Average Recurrence Interval for major drainage systems shall be 100 years.

6.2.1.3 Level of service for a minor system

The normal level of service that shall be provided by new components of the Water Corporation's

main drainage system for a minor storm event are listed below.




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(a) Open Drains

The normal level of service provided by the Water Corporation, by newly taken over,

constructed or upgraded open drains, shall be the containment within it's banks, with a

minimum freeboard of 300mm, of the flows from a minor design storm of critical duration.

(b) Drainage pipes or conduits

The normal level of service provided by the Water Corporation in urban areas, by all newly

taken over, constructed or upgraded drainage pipes or conduits shall be the containment of the

flows from a minor design storm of critical duration.

(c) Compensating and Detention Basins

The normal level of service provided by the Water Corporation shall be the containment in the

basin of the runoff from a 10 year average recurrence interval design storm of critical duration

with a minimum freeboard of 300 mm above the design top water level. This level of service

shall apply to compensating basins and detention basins that will form part of the Water

Corporation’s main drainage asset.

(d) Culverts

The normal level of service provided by the Water Corporation shall be for a culvert to

discharge the runoff from the design storm event for a minor system with a minimum freeboard

at the headwater of 300 mm and to discharge the flow from a 10 year ARI storm of critical

duration without overtopping the culvert.

6.2.1.4 Level of service for a major system

(a) The normal level of service for a major system shall be the containment of the flows from a

major storm event of critical duration within designated flow paths and flood plains as agreed

with the Local Authority and other responsible agencies. Identification and maintenance of

major event flood paths and designation of flood plains is NOT the responsibility of the Water

Corporation.

(b) The minimum design freeboard to the finished floor level of any existing or proposed building

within the catchment shall be as set by the Local Authority or relevant building authority

(Typical minimum freeboard would be 300mm).

(c) Important community facilities (e.g. hospitals), requiring a greater security from flooding due to

the significance of the consequence of potential damage, should be identified on the Major

Event Plan and the minimum freeboard increased to incorporate community protection

standards.

(d) The level of service with regard to the design of culverts and bridges (i.e. depth and velocity of

flow over the top of the structure) is to be determined for each structure by consultation with

the relevant road authority.

6.2.1.5 Coefficients of Runoff

(a) For the calculation of runoff from a catchment using the Rational Method, Design Engineers

may use the coefficients of runoff for the relevant conditions from Table 6.2 as a guide.




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(b) Designers who elect to use other techniques, such as runoff routing, for estimating runoff shall

obtain approval for the use of the other technique from the Water Corporation’s Manager,

Infrastructure Development Branch. The appropriate calibration parameters or coefficients to

be used shall be verified with the Manager, Infrastructure Planning Branch. Computer models

may be used in accordance with Clause 6.1(m) of this section.

Table 6.2: Rational Method Design Coefficients of Runoff for various land uses and soil types

LAND USE SAND –

CALCAREOUS

SAND –

BASSENDEAN

CLAYEY SAND CLAY

POS/RURAL 0.05 0.10 0.15 0.30

*RESIDENTAIL 0.15 0.20 0.25 0.40

* RESIDENTIAL

WITH DIRECT ROOF

CONNECTION

0.30 0.35 0.40 0.55

INDUSTRIAL 0.75

COMMERCIAL 0.75 to 0.9

*RESIDENTIAL refers to a residential zoning code of between R12.5 and R50. Coefficients for

zoning densities outside these limits should be verified with the Water Corporation before being

incorporated into the design.

6.2.1.6 Rainfall intensity - frequency - duration

The rainfall intensity - frequency - duration (IFD) relationships used in the hydrologic design are as

set out in AUSTRALIAN RAINFALL AND RUNOFF, VOLUME 1 and VOLUME 2, Edition 1997.

Representative curves for the Perth Metropolitan Region have been prepared for use in design

calculations and are included as Figures 6.1 to 6.3.

6.2.1.7 Design methods

Designs using the Rational Methods will be accepted only for small drainage systems. As the Rational

Method cannot be used to simulate flow behaviour throughout a complex network, larger drainage

systems will require full hydrograph investigation using computerised numeric models approved by

the Water Corporation and as outlined in Clause 6.1(k) of this section.




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Figure 6.1




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Figure 6.2




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Figure 6.3




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BLANK PAGE




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6.2.2 Hydraulic Design

6.2.2.1 General

The hydraulic design of the Water Corporation's drainage system shall incorporate the

recommendations and methodology of AUSTRALIAN RAINFALL AND RUNOFF, VOLUME 1,

Edition 1997, Book 7, Aspects of Hydraulic Calculations and Book 8 - Urban Stormwater

Management, with particular reference to Section 1.6.

6.2.2.2 Specific criteria for the design of components of a drainage system

(a) General

Design Engineer shall use the formulae and coefficients shown in Table 6.3 for the applicable

drain type and condition. For pipes other than reinforced concrete the Colebrook – White

formula should be used with roughness coefficients based on the manufacturer’s

recommendations. Roughness coefficients for alternative pipe and culvert materials shall be

approved by the Water Corporation. Design Engineers who choose to use a formula other than

Colebrook – White, shall obtain approval for the use of the alternative formulae from the

Manager, Infrastructure Planning Branch and shall include a statement justifying the use of that

formula with the calculations. InfoWorks software uses Mannings formula for all drain

types/surfaces.

Table 6.3: Roughness Coefficients for Drainage Elements

Drain Type Formula Roughness

Coefficient

Condition

k = 0.6 mm v ≤ 1.5 m/sec and access chamber

losses ignored

Reinforced Concrete Pipe Colebrook – White

k = 0.15 mm v > 1.5 m/sec and access chamber

& other losses included

Concrete Box Culvert Manning n = 0.013

Base Flow Channels and Swales Manning n = 0.015 Earth channel with toe protection

Open Drain Side slopes at 1:2 or

steeper*

Manning n = 0.030 Poorly vegetated +

Open Channels and Swales with

Side slopes at 1:6 or flatter

Manning n = 0.035 Grassed †

Vegetated Open Channels and

Swales with Side slopes at 1:6 or

flatter

Manning n = 0.08 Clear waterway base with banks

vegetated with reeds and sedges†

Heavily Vegetated Open

Channels and Swales

Manning n > 0.11+ Heavily vegetated with reeds and

sedges†

* This type of channel is not recommended for new works. See §6.2.2.2 (d) (i)

+ To determine “n” for other conditions refer to AUSTRALIAN RAINFALL AND RUNOFF

Tables 4.1 and 14.17

† Scour potential before grass or vegetation is established shall be investigated




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(b) Drainage pipes or conduits

(i) Each section of pipe or conduit shall be designed to flow full, but not under head. The

main drain shall be designed to accommodate minor event design storm runoff from all of

the upstream catchment with a recommended minimum freeboard of 0.3 metre at the

upstream end of the Local Authority connection. Piping between compensating basins

shall be checked considering the requirements of Clause 6.2.1.3 (c) of this section.

(ii) Flow velocities in drainage pipes or conduits running full should be kept between 0.75

m/s and 5.0 m/s. Consideration shall be given to the possibility of siltation from

prolonged base flows.

(iii) The replacement of natural watercourses or open channels with drainage pipes or

conduits is inconsistent with the principles of Water Sensitive Urban Design. In such

situations, the Design Engineer will be required to justify the use of a pipe or conduit. In

certain circumstances, the Design Engineer may be required to demonstrate how the

values of the natural watercourse or open channel have been incorporated elsewhere into

the design.

(iv) Refer to sections 6.3, 6.4 and 6.9 of this section of the standard for detailed requirements

for design of drainage pipes and conduits.

(c) Culverts

(i) Culverts designed to the details required in Section 3 of the Concrete Pipe Association of

Australia publication, Hydraulics of Precast Concrete Conduits, Pipes and Box Culverts,

Hydraulic Design Manual would meet the requirements of AUSTRALIAN RAINFALL

AND RUNOFF, VOLUME 1, Edition 1997, Book 7- Aspects of Hydraulic Calculations,

and Book 8- Urban Stormwater Management.

(ii) Where appropriate, the potential for safe thoroughfare for wildlife should be considered

when sizing culverts

(iii) Refer to sections 6.3.14 and 6.5 of this section of the standard for other requirements for

design of culverts.

(d) Open drains in fenced reserves

(i) The use of steep sided open drains is discouraged. This type of drain should only be

considered where restricted site conditions rule out the use of other types of conveyance.

New proposals for steep sided open drains will only be approved where it can be

demonstrated that other options are not feasible.

(ii) Where environmentally and socially beneficial and otherwise practicable, existing steep

sided open drains in fenced reserves should be rehabilitated. The design objectives of

rehabilitation include landscape integration and enhancement and restoration of natural

land gradients. This type of rehabilitation is subject to funding arrangement acceptable to

the Water Corporation

(iii) The design of steep sided open drains will vary with the types of soil encountered. As a

general rule to minimise silting or scour, the range of design peak velocities allowable

(for the flow from a minor system design storm) is from 0.3 m/s to 1.2 m/s for drains

constructed in sand or from 0.3 m/sec to 1.5 m/sec for drains constructed in clay.

(iv) Open channel sections of steep sided drains shall be designed to flow with a minimum

freeboard of 0.3 metre with the flow from a minor system design storm. Design depths of




Ver 2 Rev 0


flow shall be calculated having due regard to the hydraulic grade lines of the upstream

connecting pipelines or culverts.

(v) Refer to sections 6.5, 6.6 and 6.7 of this section of the standard for detailed requirements

for design of open drains and associated works.

(e) Urban Streams, Swales and Open channels accessible to the public

(i) The minimum capacity of a vegetated, paved or pitched floodway (including paths,

cycleways and roads that act as floodways) and the incorporated natural water course,

base flow channel or low flow pipe, shall be the design flow for the minor design storm.

The performance of the drain in a major storm event shall be examined to ensure that any

flows that are not contained within the floodway are contained within the designated flow

path shown on the Major Event Plan.

(ii) The maximum velocity within the vegetated floodway or base flow channel shall be less

than 1.2 m/s. Design velocities for flow over the floodway shall be chosen having regard

to the maintenance of the proposed bank condition (e.g. earth or well vegetated), and

public safety. Minimum velocities to limit silting on the flood plain are normally

disregarded.

(iii) Because the floodway will carry significantly more flow than the base flow channel or

low flow pipe, culverts, road bridges and pedestrian bridges have the potential to restrict

the flows from a major storm event. To protect the structure and so that pedestrian and

vehicular traffic is not placed in hazardous situations during a major event the design of

the structure shall consider the frequency of overtopping and the associated

velocity/depth relationship (with the inherent risk to public safety) and the downstream

scour potential.

(iv) Floodways that are normally designated as pedestrian accessways shall have a maximum

depth x velocity product of 0.32 m²/s for the major event1. Trafficable floodways shall

have a maximum depth x velocity product of 0.4 m²/s for the major event2. On roads and

kerbed pavements, the depth shall be taken as the depth in the channel adjacent to the

kerb. On unkerbed pavements, the depth shall be measured above the low point of that

pavement section.

(v) The base flow channel shall be designed to prevent nuisance surface flooding. The use

of low flow pipes is discouraged and will not be approved unless better options are not

feasible. Low flow pipes are considered to be inconsistent with Water Sensitive Urban

Design principles. .

(vi) Where practicable and subject to acceptance by the Water Corporation, occasional pools

should be designed into the base flow channel to assist in providing habitat and genetic

refuges during dry seasons.

(vii) The minimum capacity of the base flow channel (or low flow pipe if one must be used)

shall be a flow that on average will not normally be exceeded more than ten times per

year.

_________________________________________________________________________

1 Keller & Mitsch (1992). Stability of Cars and Children in Flooded Streets. Int. Symp. Urban Stormwater Management 1992, Sydney. 2 Institution of Engineers, Australia (1997). Australian Rainfall & Runoff. Vol. 1.

Argue (1986). Storm Drainage Design in Small Urban Catchments. ARRB Special Report No. 34.

Neville Jones & Associates and Australian Water Engineering (1994). Queensland Urban Drainage Manual, Vol.1. Dept of Primary

Industries - Water Resources, IMEA, Brisbane City Council.




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(viii) The base flow shall be contained within the base flow channel at a depth not greater than

250 millimetres (or within a base flow pipe that is just flowing full. A base flow channel

shall be a maximum of 400 mm deep and a minimum of one metre wide. The minimum

size of a base flow pipe shall be 300 mm nominal diameter

(f) Compensating basins

(i) Small systems - The following methods are acceptable only for estimates of storage

requirements, feasibility studies or initial planning investigations and for the design of

small systems with up to three basins:

• the Modified Copas Equation,

• a graphical mass curve approach based on the peak inflow rate obtained from using

the Rational Method, or

• the methods described in Section 7.5.6 of AUSTRALIAN RAINFALL AND

RUNOFF, Volume 1 Edition 1997, Book 7-A Guide to Flood Estimation, Volume 1.

The Modified Copas Equation is

If the Rational Method is used:

• to design a small system located downstream of a compensating basin, or

• to prepare the conceptual design for a drainage system located downstream of a

compensating basin

The design flow and relevant hydraulic grade line (HGL) in the main drain downstream of

the basin and proposed drainage system shall be provided by the Water Corporation.

(ii) Complex systems - For the design of the storage requirements for large or complex

systems a non linear storage routing model acceptable to the Water Corporation or

computer model in accordance with Clause 6.1(m) shall be used.

( )S Q t p t tp t

Qs c s

c= ⋅ ⋅ − ⋅ + +

⋅

0 06

2

.

where : S = Storage volume required (m³)

Q = Peak run off for storm duration ts (L/s)

p = Average compensated design discharge

(L/s)

ts = Critical storm duration (mins)

tc = Time of concentration (mins)




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(iii) In the design of compensating basins, allowance may be made for "bank storage", in

addition to the storage contained in the basin. To arrive at a suitable estimate of bank

storage, the rate at which water can be accepted into the voids of the surrounding soil

should be considered. Bank storage assumptions, if incorporated, should be

substantiated by an assessment of the amount of water infiltrated into the banks. The

amount of water infiltrated depends on the permeability of the bottom of the basin and

the underlying soil, the depth to the ground water table, the basin geometry and period of

inundation.

(iv) The use of steep sided compensating basins in fenced reserves is discouraged. New

proposals for steep sided basins will be approved only where it can be demonstrated that

other options are not feasible.

6.2.3 Water Sensitive Urban Design

6.2.3.1 Issues

In designing a drainage system with a commitment to responsible water resource management

approach, the Design Engineer must resolve a number of issues:

• What are the functions of the drain and what are the constraints that the drain may need to

address? For example: Flood protection; Water Quality renovation to meet catchment targets;

Maintenance of environmental flows in receiving waters; etc.

• What are the impacts on groundwater and on the environment (both the built and natural

environments) both during construction and after completion of the drainage works?

• How can the drain contribute to the enhancement of environmental values and

landscape/aesthetics of the surrounding land?

6.2.3.2 Multidisciplinary Approach

The Design Engineer should enlist the skills of a multi-disciplinary professional team for advice on

how to best incorporate the principles of Water Sensitive Urban Design into the drainage design. The

following may need to be addressed:

• Identify ways to make the drain aesthetically pleasing and add to the amenity values, including

landscape and recreation values, of the surrounding land.

• Assess the feasibility and suitability of drainage water use/re-use for irrigation of adjacent

parklands or playing fields

• Identify ways to make the drain function as a wildlife corridor and be attractive as habitat for

wildlife common and/or in need of habitat in urban areas.

• Identify opportunities for introduction of pollutant removal techniques to improve water quality

and the appropriateness of those techniques.

The Water Sensitive Urban Design requirements shall be determined by consulting the Department of

Water regarding design and the Local Authority regarding their agreement for the ongoing

maintenance. The final approval of the design must be by the Water Corporation, but a maintenance

agreement shall be in place before such approval.




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6.3 Drainage Pipes and Conduits

6.3.1 General

(a) Methods and criteria that shall be used for the hydraulic design of drainage pipes and conduits

are detailed in Clause 6.2.2 of this section.

(b) Gravity piped drains should be constructed using reinforced concrete pipes manufactured to AS

4058 - 1992, Precast concrete pipes (pressure and non pressure). The use of other materials

will require special approval.

(c) Except at certain compensating basin outlets, parallel subsoil drain pipes and swale drain base

flow pipes, the minimum size pipe allowable in a main drainage system is 450 mm nominal

diameter. Box culverts shall have a minimum cross section of 450 mm by 300 mm.

(d) Pipe diameters along a main drain should not decrease in the downstream direction (other than

at compensating basin outlets) irrespective of steeper grades. If a decrease of diameter occurs

due to a staged upgrading, a special transition section shall be provided.

(e) Where an existing open channel is being replaced with a piped drain, any groundwater control

function of the open channel must be maintained by the piped drain to avoid subsequent

groundwater rise. Unless not required by the Water Corporation, this shall be achieved by

constructing the piped drain as a subsoil drain (using slotted pipe and filter materials) or by

supplementing the piped drain with a smaller sized subsoil drain laid parallel to the larger piped

drain.

(f) Subject to more stringent requirements by the owners of other services the preferred minimum

clearance between parallel services is 600 mm, except in the case of parallel subsoil drains

supplementing a larger piped drain, in which case there is no minimum clearance.

(g) Lateral connections should preferably be at crown to crown with the outlet pipe except in cases

stated in Clause 6.3.1(h).

(h) In special cases of lateral connections, such as subsoil drains (where maximum depth is

necessary for maximum effectiveness), the connection may be installed with its invert 150 mm

above the invert of the outlet pipe.

(i) In all cases, lateral connections installed below crown to crown with the outlet pipe, shall all be

checked to ensure that there will be no properties flooded by water from the main drain during a

storm.

(j) The use of low flow pipes to transport base flows in swales and channels should be avoided

wherever possible. Artificial streams with base flow channels are preferred in suitable

locations. If flows are unlikely to be continuous throughout the year, the stream shall be

designed to ensure that residual water pools will drain effectively. Refer also to the relevant

Clauses under 6.2.2.2 (e) of this section.

6.3.2 Installation and Bedding

6.3.2.1 General

(a) Requirements for the installation and bedding of drainage pipes and conduits shall be

determined by depth, nature of the ground, groundwater level and type and size of installation

and in-service and construction loading conditions. Each case should be considered separately.

(b) Where drains are laid at a grade of 1:5 or steeper, special consideration shall be given to the

bedding and anchorage of the pipe or conduit.




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(c) Compaction tests shall be carried out with a "Perth Sand Penetrometer"

6.3.2.2 Foundations

The minimum requirements for the foundation of trenches are as follows:

(a) Foundations in sand areas shall be dry sand, compacted to achieve a minimum reading of 6

blows per 300 mm to a minimum depth of 0.75 metre below the foundation level.

(b) Foundations in clay areas shall be sound undisturbed clay. Disturbed or unsound areas shall be

removed to sound material and shall be backfilled with coarse clean sand compacted to achieve

a minimum reading of 6 blows per 300 mm, or compacted 20 mm "all-in" crushed granite or

similar approved material.

(c) Where the foundation is rock, the trench shall be excavated to a further 75 mm and the

excavated material replaced with compacted coarse clean sand (refer Australian Standard AS

3725 - 2007 "Design for installation of buried concrete pipes").

(d) Pipes or conduits laid in trenches with unsound foundations shall be supported on piles and

bearers approved by the Water Corporation.

6.3.2.3 Backfill

(a) Backfill material shall be sand or granular material suitable for compaction.

(b) The standard of compaction of backfill to be achieved shall be the higher of the requirements

of:

• Clause 6.3.2.3(c) of this section,

• Australian Standard AS 3725 - 2007 "Design for installation of buried concrete pipes" and

Australian Standard AS 3725 Supplement 1 - 2007 "Design for installation of buried

concrete pipes- Commentary", or

• The authority in control of the land in which the drain or structure is to be constructed.

(c) Backfill shall be compacted to achieve a minimum reading of 8 blows per 300 mm under all

trafficable areas and 5 blows per 300 mm elsewhere or compacted to a dry density equal to or

better than the dry density of the surrounding undisturbed soil.

6.3.2.4 Reinforced concrete pipe

The installation of reinforced concrete pipes designed to be part of a Water Corporation main drain or

sub soil drain should be in accordance with Australian Standard AS 3725 - 2007 "Design for

installation of buried concrete pipes" and Australian Standard AS 3725 Supplement 1 - 2007 "Design

for installation of buried concrete pipes - Commentary". This standard has been tabulated in the

Concrete Pipe Association publication "Concrete Pipe Selection and Installation". The minimum

installation requirement for reinforced concrete pipes designed to be part of a Water Corporation main

drain or sub soil drain shall be "Type U" support to Australian Standard AS 3725 - 2007 "Design for

installation of buried concrete pipes", with the foundation requirements specified in Clause 6.3.2.2 of

this section.

6.3.3 Cover to Pipes or Conduits

(a) The minimum cover to drainage pipes or conduits other than the base flow pipes in swale drains

shall be 750 millimetres.




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(b) The minimum cover to drainage pipes or conduits under roads and trafficable right of ways

shall be 900 millimetres

(c) The minimum cover to the base flow pipe in a swale drain shall be 300 millimetres.

6.3.4 Concrete Encasement

(a) Drainage pipes and conduits shall be concrete encased in the circumstances indicated below:

(i) Where considered necessary for reducing abnormal maintenance such as at river or ocean

outfalls.

(ii) To provide structural strength when cover has been increased or reduced.

(iii) When future access or maintenance will be difficult.

(iv) As required by the Water Corporation.

(b) Concrete used for encasement shall be Class N25 and be reinforced. Minimum thickness of

concrete around the pipe barrel and collar shall be 150 mm.

6.3.5 Location of Drainage Pipes or Conduits in Private Property

(a) Where there is a choice between locating a drain in public or private land the drain should be

located in public land.

(b) Drainage pipes or conduits shall be located in private property only if subject to the provision

of an easement in favour of the Water Corporation.

6.3.6 Location of Drainage Pipes or Conduits in Road Reserves

(a) Drainage pipes or conduits laid in the road reserve should be located in accordance with the

requirements of the latest Utility Providers Code of Practice for Western Australia.

(b) The preferred alignment for drains is 4.0 m.

(c) Other alignments may be used, after written agreement has been obtained from the relevant

authority.

(d) Drains 450 mm diameter and larger shall be considered as Trunk Services and may be laid

within the Trunk Services alignment by agreement with the relevant authorities.

(e) Drainage pipes and conduits shall not be laid within the reserves of controlled access roads

unless a written agreement of the controlling authority has been obtained.

6.3.7 Location of Drainage Pipes or Conduits in Vested Reserves

(a) Where a drainage pipe or conduit is laid in land already vested in an authority other than the

Water Corporation, one of the following land instruments shall be obtained:

• An easement over the existing reserve of the other authority.

• A reserve excised from the existing reserve of the other authority.

(b) Where a drainage pipe or conduit will be laid adjacent to the boundary of private properties in a

reserve of unrestricted width such as a Public Open Space, Recreation Reserve, etc, the pipe

shall be positioned so that the Water Corporation's total land requirements for access to and

protection of the drain shall be within the reserve and shall not impose any encumbrance on the

adjacent private property.




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(c) Where a drain will be laid in a road reserve, a Pedestrian Access Way, a Right of Way, or

similar, and the width of the reserve is less than the total width of the Water Corporation's land

requirements for protection of the drain, as detailed on Drawing DG16-8-6, the total width

required shall be made up by appropriate easements on the adjoining properties. Refer also to

Clause 6.3.8(e).

6.3.8 Requirements for Easements for Drainage Pipes or Conduits

(a) The requirements for easements for drainage pipes or conduits shall be determined at the

preliminary investigation stage of the drain design and the necessary easements shall be granted

free of charge to the Water Corporation.

(b) Easements over drainage pipes or conduits are required to make present and future owners of a

property aware that there is an encumbrance on the property.

(c) All drainage pipes or conduits which will be laid in private property shall be provided with an

easement.

(d) The minimum width of an easement shall be as detailed on drawing DG16-8-6

(e) The alignment of drainage pipes or conduits should be on the centreline of the easement.

6.3.9 Requirements for Reserves for Drainage Pipes or Conduits

(a) Drainage pipes or conduits shall be located in a drain reserve when required by the Water

Corporation.

(b) The requirements for reserves for drainage pipes or conduits shall be determined at the

preliminary investigation stage of the drain design and the necessary reserves shall be granted

free of charge to the Water Corporation.

(c) The minimum width of a reserve for a drainage pipe or conduit shall be as detailed on drawing

DG16-8-6.

6.3.10 Crossing of Roads, Railways and Other Services

6.3.10.1 General

(a) The number of drain crossings under freeways, controlled access roads and railways should be

kept to a minimum.

(b) Drains should be located so that crossings under all roads and railways are approximately at

right angles to the road or railway reserve boundary.

(c) If a diagonal road crossing must be made, the angle between the drain and the normal to the

road reserve boundary should not exceed 45°.

(d) Where it is proposed to lay drains crossing under freeways, controlled access roads and

Westrail land the following conditions shall be complied with:

• Written approval for the crossing shall be obtained from the controlling authority.

• Unobstructed access to access chambers within the road or rail reserve shall be available

from outside the reserve.

(e) Drains crossing railway reserves shall be laid to comply with the requirements of the "Railways

of Australia Code for the Installation of other Parties' Services and Pipelines within Railway

Boundaries".




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(f) Subject to more stringent requirements by the owners of the other service, a minimum vertical

clearance of 150 mm should be maintained between drainage pipes or conduits and all other

services. Where this cannot be accomplished Clause 6.3.10.2 or Clause 6.3.10.3 of this section

applies.

6.3.10.2 Services passing through drainage pipes or conduits

(a) Services intersecting a drainage pipe or conduit shall be diverted to clear the outside of that

conduit by a minimum of 150 mm wherever possible.

(b) Services shall not pass through drainage pipes or conduits unless an access chamber is provided

at the intersection.

(c) Where a service is to cross an existing main drain the access chamber structure shall be sized to

provide sufficient unimpeded waterway around the service so that the existing level of service

at upstream connections is maintained and maintenance requirements will be minimal.

(d) Services passing through drainage pipes or conduits shall be constructed to the lines shown in

Figure 6.4. While a pipe is shown, the principles apply to box culverts and other conduits.

(e) Services will be permitted to pass through drainage pipes or conduits only when it can be

proved to the Water Corporation that all other possible routes have been found to be

impracticable.

(f) All services shall be protected by a sleeve, preferably a reinforced concrete pipe or similar,

designed to be self supporting with no intermediate supports and located so as to minimise

interference to the flow in the drain.

(g) The angle from the centreline of the service to the centreline of the Water Corporation drain

shall be within 70° to 110°

Figure 6.4

WATER CORPORATION

CONDUITWATER CORPORATION

CONDUIT




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6.3.10.3 Siphons under services

Siphons will only be approved in exceptional circumstances. The design concept incorporating a

siphon shall be approved by the Manager, Infrastructure Planning Branch at the preliminary planning

stage.

6.3.11 Junctions

(a) Junctions, other than cut-in junctions, shall be at an access chamber or a structure.

(b) Cut-in junctions are permitted on any main drainage conduit where the ratio of the nominal size

of the main drain to the nominal size of the lateral drain is equal to or greater than 3:1.

Junctions should not be re-entrant. The minimum angle from the main drain shall be 45°.

6.3.12 Pipes, Fittings and Joints

(a) Only one type of pipe shall be used between any two access chambers.

(b) Gravity piped drains should be constructed using reinforced concrete pipes.

(c) Sub soil drains should be constructed using reinforced concrete or PVC pipe.

(d) Reinforced concrete pipes should be Class 3 minimum to Australian Standard AS 4058 - 1992,

Precast concrete pipes (pressure and non pressure).

(e) PVC pipe should be Class SN8 minimum to Australian Standard AS 1260 -2009 PVC pipes and

fittings for drain, waste and vent applications.

(f) Joints in concrete pipes should be rubber ring joints

(g) Joints in PVC pipe should be solvent welded for pipe sizes up to and including 300mm nominal

diameter. PVC pipes larger than 300mm nominal diameter shall be rubber ring jointed.

(h) Pipes shall be jointed in accordance with the manufacturer's recommendations. Refer also to

field joints shown on drawing DG16-8-1.

6.3.13 Splay Pipe Bends.

(a) The minimum size pipe that shall be manufactured as a splay bend shall be 900 millimetres.

(b) Splay pipe bends should be accomplished by using factory made bends fabricated from rubber

ring jointed pipes.

(c) Each pipe length in a splay bend shall incorporate only one change of direction. The maximum

change of direction in each pipe length shall be 22.5o. Where a splay bend incorporates more

than one pipe the change of direction at each pipe shall be equal.

(d) Each pipe manufactured as a splay bend shall be manufactured so that the socket is located on

the upstream end of the pipe.

(e) Elliptically reinforced pipes manufactured as splay bends shall have the top of pipe clearly

marked.

(f) A typical splay pipe bend arrangement together with criteria for the use of splay pipe bends are

shown on Drawing DG16-8-1. Refer also to Clauses 6.4.1. (i) and 6.4.1(j) of this section

dealing with location of splay bends.




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6.3.14 Box Culverts and Link Slabs

6.3.14.1 General

(a) For spans up to 1200 mm, box culvert sections shall comply with AS 1597.1 - 2010, Small

culverts (not exceeding 1200 mm span and 1200 mm height). For spans over 1200 mm, box

culvert sections shall comply with AS1597.2 – 1997, large culverts (from 1500 mm span and up

to and including 4200 mm span and 4200 mm height) for carrying roadway and railway loading

specified by AS 5100.

(b) Because of the difficulty in bedding precast invert and base units, only crown units installed on

cast in-situ base slabs shall be used as part of a main drain.

(c) Link slabs may be used with box culverts.

(d) During transport and handling of box culverts and link slabs the manufacturer's

recommendations shall be observed.

6.3.14.2 Installation

(a) Precast box culverts shall be placed on a cast in-situ, reinforced, concrete base slab.

(b) Culverts shall be installed with a joint gap of 5 mm to 10 mm between units. Joints shall be

made good by either of the following methods:-

• A foam joint spacer shall be used between units and the joint filled with a 3:1 sand cement

grout made workable with plasticiser. Joints shall be covered with a sand band (Rocla

Sandband or similar approved sealing strip) after grouting.

• By placement of a 150 mm minimum width by 100 mm minimum thickness concrete

bandage reinforced with SL41 mesh.

(c) Culverts and link slabs shall be set in a 3:1 sand/cement mortar bed.

6.3.14.3 Cast in-situ base slabs

(a) The slab shall be laid on a minimum of a 100 mm thick layer of compacted coarse clean sand or

crushed granite. The minimum foundation requirements shall be as specified in Clause 6.3.2.2

of this section.

(b) To prevent the legs of crown units being forced inwards by consolidation of the backfill

material cast in-situ reinforced concrete base slabs shall have rebates cast into the slab to

provide a recess for the legs. Rebates shall not be formed by pouring a concrete infill after the

crown units have been laid on the base.

(c) The minimum rebate depth for box culverts up to 1200 mm span is 10 mm. For box culverts

with spans of 1200 mm and over, the minimum rebate depth shall be 25 mm. Allowance for

dimensional tolerances in culvert span and leg width, shall be made when locating and sizing

rebates.

(d) The length of the slab shall be sufficient to allow for a 10 mm joint gap between units.

(e) The slab shall be designed as a one way slab in accordance with Australian Standard AS 3600 -

2009, Concrete structures. The main reinforcement shall be normal to the legs of the box

sections and the minimum slab thickness shall be 150 mm.




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6.3.14.4 Joints

Box culvert joints shall be made as specified in Clause 6.3.14.2 of this section.

6.3.14.5 Bends

Splay bends shall be accomplished by using factory made splay cut box culvert units.

6.3.15 Subsoil Drains

6.3.15.1 General

(a) Subsoil drains form part of a Water Corporation main drain only when they are installed as the

main drain itself or to act as a ground water control when a drain is piped.

(b) The extent of subsoil drain intended to be the responsibility of the Water Corporation shall be

clearly delineated on the drawings.

(c) Subsoil drainage must provide adequate separation from valuable wetland areas. Permission

from the Department of Water is required to construct open drains or install subsoil drains at

levels lower than the Control Groundwater Level (CGL). The CGL must be determined in

consultation with the Department of Water.

(d) Incorporation of sub-soil drains into main drains is dependent on confirmation that the soils that

are to be drained are isotropic, to ensure the required permeability is provided. An analysis

shall be provided by the Design Engineer.

6.3.15.2 Pipes

Only approved perforated or slotted circular pipes shall be used in Water Corporation subsoil drains.

Solid pipes laid with open joints in lieu of slotted pipes will not be approved.

6.3.15.3 Filters

Slotted pipes shall be laid in a granular filter which has a cloth filter surround as shown on Drawing

DG16-3-21.

6.3.15.4 Box culverts

Box culverts may be used as subsoil drains as shown on Drawing DG16-3-21.

6.4 Access Chambers

6.4.1 General

(a) Access chambers shall be designed to the criteria specified in this section and the details shown

on Drawings DG16-3-1 to 3-7 inclusive.

(b) Junctions at access chambers shall comply with the requirements of Clause 6.3.11 of this

section.

(c) Full detailed drawings shall be supplied for all access chambers as follows:-

• greater than 6 metres deep and/or

• outside the sizes shown on the standard drawings and/or

• as required by Table 6.6.




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(d) Approved construction materials for access chambers are detailed in Table 6.6. Alternative

construction materials may be approved by the Manager, Infrastructure Design Branch.

(e) At any access chamber on a main drain, the main drain outlet (downstream) pipe should be no

higher than crown to crown with the main drain inlet (upstream) pipe.

(f) Inlet pipes other than main drains (e.g. connections) shall be located completely under the

corbel (or conversion) slab and to Water Corporation approval. The standard height to corbel

slab can be increased to accommodate this requirement. The preferred level for these inlets is

crown to crown and the minimum level should not be lower than springing to springing.

(g) Inlet pipes should not enter directly opposite or interfere with ladders.

(h) The maximum allowable distances between access chambers are shown in Table 6.5

(i) It should be possible to view any point in a pipe drain from at least one access chamber and

only one change of direction (i.e. splay bend) should be included between access chambers.

Consequently access chambers shall be provided on pipe drains at the following locations:

(i) At a change of grade.

(ii) At a change of direction if a splay bend is not permissible.

(iii) At a change of pipe diameter.

(iv) At intersections of main drains.

(v) At connections, where the ratio of inside diameters of lateral drain to main drain is

greater than 1:3.

Table 6.5

Pipe

Diameters (mm)

Max. Allowable

Distance Between

Access chambers (m)

300 100

375 120

450 140

525 160

600 180

675 200

750 220

900 240

1050 260

1200 280

1350 300

1500 350

1650 & OVER 400

(j) An access chamber shall be provided within one hundred metres of a splay bend.

(k) The location and orientation of access chambers shall permit the removal of covers without

being restricted by existing or proposed fences and retaining walls.




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(l) Within road reserves, access chambers shall be positioned within the 3.0 metre to 4.2 metre

alignment or as agreed with relevant authorities.

(m) Access chamber covers should be clear of the kerb where possible.

6.4.2 Construction Materials for Access chambers

Materials approved for use in the construction of access chambers are detailed in Table 6.6.

Table 6.6

CONSTRUCTION

MATERIAL

PIPE DIA mm DEPTH m # DRG No REMARKS

BRICKWORK ≤900 ≤2.4 DG16-3-1** Design drawings required for

larger drains

BRICKWORK ≤2100 2.4

to

6.0

DG16-3-2** Design drawings are required

for larger &/or deeper drains

IN SITU

REINFORCED

CONCRETE

May be only used below corbel slab & when access chamber is deeper than 2.4

metres. General dimensions and criteria of standard brick access chambers apply.

Design drawings required for each access chamber.

PRECAST

REINFORCED

CONCRETE *

≤750 ≤6 DG16-3-7**

# Depth is measured from top of cover to invert of downstream pipe

* May be used for depths greater than 6 metres when structural design drawings incorporating

ladders and platforms, to Water Corporation requirements, are approved by the Water

Corporation (a minimum 1500 mm diameter access chamber section will be required)

** Details of reinforced concrete foundation slab are to be included in the Drawings by the

Designer Engineer considering the foundation condition and ground water level.

6.4.3 Brick Access Chambers

(a) The minimum clearance from the internal diameter of a pipe at the internal face of an access

chamber wall to the nearest side wall should not be less than 100 mm.

(b) The minimum clearance between the outside diameters of any two drains entering a brick

access chamber should be 100 mm at the internal face of the access chamber wall.

(c) The wall thickness on brick access chambers shall not be reduced to accommodate pipe spigots

or sockets. If necessary the pipe sockets shall be removed or a larger access chamber shall be

used.

6.4.4 Precast Concrete Access chambers

(a) The access chamber segments shall be reinforced concrete spun sections to AS4058.

(b) The maximum outside diameter of a pipe connected to access chamber shall not exceed 30% of

internal diameter of the access chamber.




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(c) Cut sectional area of an access chamber segment in any horizontal plane shall not exceed 60%

of the total sectional area in that plane.

(e) A minimum wall width of 250mm shall be allowed between holes cut for pipe openings.

6.4.5 Access chamber Covers

Access chamber covers shall be rectangular, cat iron and in two equal parts conforming to Australian

Standards AS3996-2006.

Load classifications of the covers to be used at different locations shall be as follows.

• Road pavements, road verges, driveways, car parks and trafficable right-of-ways – Class D.

• Lots, parks and reserves – Class C.

6.4.6 Bends and Junctions at Access Chambers

Permissible arrangements for bends and junctions are shown on Drawing DG16-8-1.

6.5 Culverts

(a) Methods and criteria that shall be used for the hydraulic design of culverts are detailed in

Clause 6.2.2 of this section.

(b) Culverts shall extend past each boundary of a road reserve allowing the erection of a fence (to

the end of the open drain) on an alignment in keeping with the usual setbacks for building in the

area.

(c) Culvert inlet and outlet structures shall comply with the requirements of Clause 6.7 of this

section.

(d) A minimum berm width of 1.0 metre shall be provided between the back of the culvert inlet and

outlet structures and the reserve boundary.

(e) Slopes steeper than 1 vertical to 6 horizontal are not permissible for the vehicular access from

the road reserve to the maintenance berm.

6.6 Open Drains

6.6.1 General

(a) Methods and criteria that shall be used for the hydraulic design of open drains are detailed in

Clause 6.2.2 of this section.

(b) Where an open drain can be constructed as an integral part of Public Open Space, an unfenced

open drain allowing public access should be constructed and integrated with existing natural

vegetation and the landscaping of the open space. These drains shall be protected by an

easement.

(c) The creation of new steep sided open drains is not consistent with the principles of Total Water

Management adopted by the Water Corporation. Public access must be denied from steep sided

open drains. Steep sided open drains shall be located in a fenced reserve. Proposals for this

type of drain will not be approved by the Water Corporation if better methods can be

implemented. Approval shall be sought at the preliminary investigation stage.

(d) Natural water courses shall be retained and where possible, degraded watercourses should be

rehabilitated.




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(e) Levees should be avoided wherever possible.

(f) Where the flow from an open drain has the potential to cause hazardous conditions for road

traffic during severe storms, the Design Engineer shall inform the Local Authority, or the Main

Roads WA when applicable, and arrange warning signs.

(g) The Design Engineer shall recognise the functions that a vegetated drain can perform, including

filtering of various forms of particulate pollutants, providing bank stabilisation to limit erosion,

enhancing habitat value, providing potential wildlife corridors and improving the appearance of

a development site.

6.6.2 Guidelines for Open Drains Accessible to the Public

(a) An unfenced open drain accessible to the public may be a natural watercourse, a landscaped

open drain or a swale drain. The aim in the design of this type of open channel drain is to

minimise the nuisance flooding by drains within recreational areas. The design should create a

watercourse and floodplain generally accessible to the public for recreational purposes for most

of the year, while still having the required design capacity in the floodway for peak flows. The

watercourse should be integrated with the landscaping for the open space.

(b) Where a natural water course is to be retained its flow regime should be maintained. If the

capacity of the watercourse is insufficient to convey the additional runoff due to urbanisation

the runoff shall be controlled by:

• constructing compensating and detention basins within the catchment to limit the

magnitude of flows to the predevelopment peak value (environmental constraints and depth

to groundwater may limit the use of this method), and/or

• constructing a grassed floodway which runs parallel to the natural watercourse and will

convey flows in excess of the natural watercourse capacity as a supplementary channel.

The grassed floodway shall be designed to ensure that small base flows are conveyed within

the natural watercourse and that the area remains accessible to the public for all times apart

from when the capacity of the natural water course is exceeded.

(c) Landscaped drains shall have a vegetated floodway with a base flow channel. The base flow

channel shall be a minimum of 1.0 metre wide and a maximum of 400mm deep. Vegetated

bank protection is preferred to formal toe protection. Formal toe protection shall not be used

without the approval of the Water Corporation. Fully developed vegetation will enhance

surface stability and control erosion of the drain. The vegetation should not significantly

restrict flow capacity. Landscaped drains should be used:

• where natural watercourses have been severely degraded and cannot be retained due to

planning constraints

• to control the potential for post-development groundwater rise to levels above the Control

Groundwater Level (CGL).

• where it is estimated that the base flow will occur for more than six months of the year

(d) Swale drains consist of a grassed floodway with or without a base flow pipe constructed below

the invert of the channel. The base flow pipe shall not be less than 300 mm nominal diameter

and shall not exceed 900 mm diameter unless justified on a cost/benefit basis. Base flow pipes

shall only be used where:

• they are required to control probable rise in groundwater; and

• base flows are likely to cause a public health or safety risk.




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(e) Swale drains should be used where: applicable, and where

• base flows only occur for short duration each year; and

• the need to control the groundwater is not a significant factor

(f) Where public access is uncontrolled, side slopes of 1 vertical to 8 horizontal or flatter are

preferred for safe access to the waters edge. However side slopes of 1 vertical to 6 horizontal

are permitted, in localised areas, around structures and in heavily vegetated areas. Steeper side

slopes are permitted elsewhere when safety fencing/edge protection is installed.

(g) The layout of this type of open drain shall meet the maintenance requirements of the Water

Corporation. The responsibility for maintenance together with the provision of landscaping

shall be determined in consultation with the Water Corporation and the Local Authority. The

Water Corporation's responsibility for maintenance is normally limited to the permanent

channel while the flood plain area is maintained by the Local Authority as part of the POS. To

satisfy this undertaking, a maintenance agreement, negotiated with the Local Authority, is

required to be submitted with the submission.

(h) Design of lateral connections shall be given special consideration.

(i) Lateral connections shall be located at drop, inlet or outlet structures wherever possible.

(j) Bank protection shall be considered at transitions of depth of flow and surface slope to

minimise erosion during flows in excess of the base flow capacity.

(k) Drawing DG16-2-2 shows the general criteria for landscaped open drains, swale drains and

landscaped natural watercourses that form part of the main drainage system.

(l) The landscaped floodway shall be designed to provide for public safety and environmental

compliance and to be erosion free and to minimise future maintenance.

(m) Toe protection approved by the Water Corporation shall be provided at all outlet, drop and

junction structures, at all bends, in unsuitable ground conditions and elsewhere as required by

the Water Corporation.

6.6.3 Guidelines for Open Drains in Fenced Reserves.

(a) The use of steep sided open drains is now discouraged. New proposals for such drains will

only be approved where it can be demonstrated that other options are not feasible. Where the

use of steep sided open drains is unavoidable, they shall be sited in fenced reserves.

(b) Side slopes for open channels shall be no steeper than 1 vertical to 1.5 horizontal in sandy soil,

and 1 vertical to 1 horizontal in very cohesive soils.

(c) Open drains in fenced reserves shall be aligned so that a berm, preferably with a minimum

width of 4.0 metre, is provided on one side for machine access and a walkway, with a minimum

width of 1.0 metre, on the opposite side. Where possible a 4.0 metre berm shall be provided on

each side of the drain.

(d) When vehicular access is required from the road reserve to the maintenance berm, access slopes

steeper than 1 vertical to 6 horizontal are not permissible

(e) The centreline of the excavation shall normally be parallel to the reserve boundaries. Actual

alignment in each case shall be chosen with regard to depth of excavation, but the width of

walkway is to be kept to a minimum with an absolute minimum of 1.0 metre.




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(f) Berms should be graded at 1 vertical to 20 horizontal (approximately) away from the centre of

the drain. A surface drainage system shall be provided and directed to suitable collector drains

where directed by the Water Corporation (e.g. in soils with poor soakage characteristics).

(g) Toe protection, approved by the Water Corporation, shall be provided at all outlet, drop and

junction structures, at all bends and in bad ground (unstable ground or loose sandy ground) and

elsewhere as required by the Water Corporation.

6.6.4 Location of Open Drains in Private Property

Open drains shall only be located on private property if that property is owned by the Water

Corporation or another authority from which an easement allowing the drain to remain in perpetuity

has been obtained.

6.6.5 Location of Open Drains in Road Reserves

Open drains shall not be located in or intrude into any road reserve unless written permission has been

obtained from the controlling authority before the proposal is submitted for approval. A copy of such

permission shall be included with any submission.

6.6.6 Location of Open Drains in Reserves Vested to Other Authorities

Where an open drain is to be constructed on land already vested in a State or a local authority other

than the Water Corporation one of the following land entitlements shall be obtained:

• An easement on the existing reserve of the other authority.

• A reserve excised from the existing reserve of the other authority.

6.6.7 Requirements for Easements for Open Drains

(a) The requirements for easements shall be determined at the preliminary investigation stage of

drain design and the necessary easements shall be granted free of charge to the Water

Corporation.

(b) Easements over open drains in private property are required:

• to protect the drain from adverse development proposals in perpetuity

• to allow for access to and maintenance of the drain

(c) Open drains which will be constructed in land that will remain private property shall be

protected by an easement (refer Clause 6.6.4).

(d) The width of an easement for an open drain shall be determined in consultation with the Water

Corporation and the agency or authority responsible for flood management but shall not be less

than the floodway at the design water level for minor storm event (1:5 or 1:10 years ARI) plus

300 mm. Refer to Clause 6.2.1.1 of this section.

6.6.8 Land Requirements for Reserves for Open Drains

(a) The land requirements for open drains shall be determined at the preliminary investigation

stage of drain design and the necessary land in fee simple or reserves shall be granted free of

charge to the Water Corporation as part of the land development process.

(b) Land for open drains is required for the following purposes:

• For public safety, to enable restriction of access to the public where the drain is steep sided




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• To protect the drain from development proposals in perpetuity.

• To allow for access to and maintenance of the drain.

• To provide opportunity for revegetation to promote water quality improvement.

(c) Additional land may need to be provided to other vesting authorities to cater for environmental,

multiple service corridors and recreation. Association of the land required for drainage with

such other reserves may present an opportunity for more efficient land use within the

community.

(d) The width of a reserve (or land in fee simple) shall be calculated as shown on Drawing DG16-

8-6. The minimum width of a reserve (or land in fee simple) to be vested in the Water

Corporation shall be 15.0 m.

6.6.9 Crossing Railways and Other Services

6.6.9.1 Crossing of railways

Where it is proposed to construct an open drain across Westrail property, or a private railway, the

drain shall be constructed to comply with the requirements of the "Railways of Australia Code for the

Installation of other Parties' Services and Pipelines within Railway Boundaries".

Liaison with the Chief Civil Engineer, Westrail, or the appropriate private owners is necessary at all

stages.

6.6.9.2 Crossings of buried services

(a) New Open Drains Crossing Existing Services

Where it is proposed to construct an open drain across a buried service such as

telecommunication cables or a gas main, the proposal shall comply with the following

conditions:-

• Written approval for the crossing shall be obtained from the service authority.

• Open drains should be located so that crossings of other services are approximately at right

angles to the service or the service realigned to suit.

• A minimum clearance of 200 mm below the design invert of an open drain should be

maintained.

(b) New Services Crossing Existing Open Drains

Where it is proposed to construct a new service such as a gas main or telecommunication cables

across an existing open drain, the proposal shall comply with the following conditions:-

• The new service should be installed either above the one hundred year flow level or below

the drain invert such that 600 mm cover is maintained between the service and the drain

invert.

• Where the new service is constructed above the 1 in 100 year flow level maintenance

access along the drain shall be maintained.

• Pipe supports or the like, or scour valves or their supports, or any access chambers of any

type shall not be located within the base width or base flow channel of any open drain.




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• Where the service carries any potential pollutant, special permission is required. Any

requirements for public health and safety shall be determined at the time of submission and

installed at the cost of the servicing authority.

• Marker posts shall be provided at the location of all services crossing a Water Corporation

open drain. For details of marker posts and their location see Clause 6.14 of this section

6.6.9.3 Crossings below above-ground services

Where it is proposed to construct an open drain below an above-ground service such as high tension

power lines, the proposal shall comply with the following conditions:

• Approval in writing for the crossing shall be obtained from the service authority.

• Open drains should be located so that crossings of other services are approximately at right angles

to the service.

• All conductive materials shall be earthed to Western Power requirements

6.6.10 Services Parallel To Open Drains

Open drains shall Services parallel to be laid no closer than the alignments shown in Figure 5.5.

Figure 6.5.

6.6.11 Protection of Existing Flora

Drainage installations shall be planned to minimise the damage to existing flora. In the case of trees

and understorey the general principle to be followed is illustrated in Figure 6.6.




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Figure 6.6

6.6.12 Fencing and Edge Protection

6.6.12.1 Fencing

Fencing should be in accordance with the standard fences detailed on Drawings GX54-4-2 & 4-3.

6.6.12.2 Edge protection

Edge protection shall be of two types as detailed below

(a) Type E1 - This type of edge protection shall include posts top rail, mid rail as per details

in AS 1657 but designed to the loading requirements for barriers in AS1170.1. The

height from base/floor shall not be less than 1.1 metre. Refer to Figure 6.7.

(b) Type E2 - This type of edge protection shall include posts top rail , bottom rail at height

100 mm from the base/floor, vertical members spaced with gaps not exceeding 100 mm

as per details in AS 1926.1 and designed to the loading requirements for barriers in

AS1170.1 . The height from base/floor shall not be less than 1.2 metre. Refer to Figure

6.7.

Type E1 edge protection shall be used at locations accessible to only adults and where a

person could fall more than 1.0 metre. If the surface on which the fall could occur has

protrusions etc to cause injury or has a depth of water more than that required for recovery or

has water flowing at a velocity to drag a person and cause injury then this type of edge

protection shall be provided irrespective of the height of fall.




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Type E2 type edge protection shall be used at locations accessible to adults and children and

where a child could fall more than 400 mm.

Figure 6.7

6.6.13 Location of Fencing and Edge Protection

The type of fence to be used at different locations of a main drain system shall be agreed with the

Water Corporation.

The general use of fencing and edge protection at different locations of urban main drain are as

follows

6.6.13.1 Trapezoidal open drains

(a) Rear and side of private residential properties only -

Free standing Hardifence or Colorbond fence - 1.8 metre high, Additional cost of any other type

of fence that is acceptable to the Water Corporation and required by owners of private

residential properties shall be borne by the owners.

(b) Road frontages and public properties -

Chainmesh Fence Type 1 – 1.8 metre high (no barbed wire). If determined by the Water

Corporation, at specific locations, Chainmesh Fence Type 1 – 1.2 metre high (no barbed wire).

Alternative fencing arrangements to improve amenity or to provide a higher level of security

(e.g. Chainmesh Fence with Buried Selvedge Barbed Extension & Razor Wire at top and

ground level- Drawing GX54-5-1) may be considered by the Water Corporation.




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(c) Industrial properties

Chainmesh Fence Type 1 – 1.8 metre high (no barbed wire). Alternative fencing arrangements

to improve amenity or to provide a higher level of security (e.g. Chainmesh Fence with Buried

Selvedge Barbed Extension & Razor Wire at top and ground level- Drawing GX54-5-1) may be

considered by the Water Corporation

6.6.13.2 Structures accessible to the public

A pool safety fence, 1.4 metre high approved by the Water Corporation or edge protection Type

E1/E2 dependent on the results of risk assessment.

6.7 Structures

6.7.1 General

(a) For safety reasons, all structures accessible to the public shall have safety fencing or guard

rails, and safety screens as required.

(b) Where a subsidiary open drain enters a larger deeper drain, the drop shall be constructed on the

subsidiary drain and the junction made grade to grade.

6.7.2 Type Drawings

Drawings for typical open channel structures for steep sided drains, indicating various functional

design features, are included as part of this standard. Since there is a wide scope for innovation in the

design of structures for landscaped open drains, landscaped natural watercourses and swale drains

typical structures have not been included.

6.7.3 Design

6.7.3.1 Materials

(a) Structures shall have a design life in keeping with that of the piped and open channel sections of

drain, and shall therefore be constructed predominantly of reinforced concrete or 230/350 mm

brickwork. The use of other materials requires specific Water Corporation approval. Materials

for structures constructed in unfenced open drains should be in keeping with the aesthetic design

aims of the landscaped open drain in its POS environment, while meeting the normal functional

and safety requirements of main drainage structures.

(b) Reinforced concrete structures shall be designed to comply with AS3600, AS/NZS4671 and

AS S3610.

(c) The minimum class of concrete for major structures shall be Grade N40 and that for minor

structures shall be Grade N32

(d) Brickwork shall be designed to comply with AS3700 and AS/NZS4455.

6.7.3.2 General Requirements

(a) Provision for the installation of stop boards to enable the control of water levels in the upstream

open drain shall be included in the design of inlet structures where requested by the Water

Corporation.

(b) The design of outlet structures requires that the effects of turbulent flow be minimised by the

provision of a combination of:

(i) A suitable stilling basin to dissipate excess kinetic energy.




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(ii) A downstream cut-off wall to prevent damage to the structure by scour.

(iii) Toe protection to protect the adjacent section of drain against scour.

(c) Provision of an upstream cut-off wall to prevent failure of the structure by "piping" is not

normally necessary except in the case of short culverts where there is a large differential head

between upstream and downstream discharge levels.

(d) Control of the velocity acceleration due to drawdown in the upstream channel at a structure

shall be considered. A notched inlet weir is the preferred method of control.

6.7.4 Trash Racks, Safety Screens, Guard Rails and Safety Barriers

(a) Single culvert inlets up to and including 1350 mm nominal diameter culvert inlet shall have

trash racks fitted. The requirement for trash racks with multi barrel culverts shall be negotiated

with the Water Corporation.

(b) The bar of trash rack installed within fenced area should be at 300 mm centres.

(c) All pipes (that are not culverts) should have inlet and outlet safety screens fitted.

(d) Safety screen bars shall be at 150 mm centres.

(e) All safety screens and trash racks should be designed to incorporate the features shown on

drawing DG16-3-13.

(f) Bars on trash racks and safety screens shall not be steeper than 45o to the horizontal.

(g) The maximum length of screen permitted without intermediate staging for maintenance

personnel shall be 2.5 metres.

(h) To assist with raking, bars on trash racks and safety screens shall be designed with minimum

intermediate support bars.

(i) Safety screens on outlet structures shall be hinged at the top and designed to swing and float

upwards with water pressure. An outlet screen should be fitted only if the inlet is screened and

all connections are trapped.

(j) Culverts having connections of 750 mm nominal diameter or larger should be fitted with safety

screens.

(k) Where screens are fitted to inlets, trash racks shall be considered upstream of the inlet. Points

to be considered include:-

• flow

• potential debris load from catchment. e.g. heavily vegetated, industrial area, etc

• access

• consequences of flooding if a blockage was to occur.

(l) The maximum design flow velocity through the openings of safety screens or trash racks should

be 0.9 metre/second.

(m) Minimum area of openings on screens or trash racks at inlets should be 3 times the area of the

inlet.




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(n) Safety fencing or edge protection shall be provided at all structures where there is danger to the

public or to maintenance staff based on risk assessment. Refer to Clause 6.13

(o) Railing to assist maintenance staff during cleaning operations shall be considered.

(p) Road Safety Barriers shall be provided at culvert locations where the culvert headwalls are

located within the clear zone distances outlined in Table 4.1 of the Austroads Guide to Road

Design Part 6: Roadside Design, Safety and Barriers. Road Safety Barriers shall conform with

the requirements of AS 3845: Road Safety Barrier Systems.

(q) Provision of bridge delineator signs at culverts shall be considered.

6.7.5 Road Bridges, Access Crossings and Occupational Crossings

6.7.5.1 General

(a) The requirement of a bridge crossing of an open drain shall be justified by economic

comparison with the alternatives such as a culvert.

(b) Bridges should preferably be at right angles to the drain or natural watercourse.

(c) Levels of roadways at bridges should conform as far as possible with levels of the adjacent

roads subject to the requirements for clearance of bridges above water level. Where it is

necessary for the road level to rise over a bridge, the grades and vertical curves shall conform to

relevant road design practice. On access crossings and occupational crossings a lesser standard

can be adopted, but proper approaches with grades and radii appropriate to the expected use

shall be provided. The impact on the flow path of the major storm event shall be considered.

6.7.5.2 Design

(a) All vehicular bridges across drains or natural watercourses shall be designed in accordance

with AS 5100- Bridge Design in conjunction with current MRWA or Local Authority

requirements.

(b) Where a vehicular bridge is to be located in a road reserve, provision shall be made to separate

pedestrian traffic from vehicular traffic.

(c) Where a vehicular bridge is to be used for an occupational crossing the minimum trafficable

width shall be 2.4 metres.

(d) The provision of pedestrian occupational crossings or walkways across drains or watercourses

is subject to agreement between the developer, the Local Authority and the Water Corporation.

The design shall provide safe access across the drain as well as adequate waterway to pass the

design flow. The minimum width of any pedestrian occupational crossing shall be 1.2 metres.

6.8 Compensating Basins

6.8.1 Design

Methods to be used for the design of compensating basins are covered in Clause 6.2.2.2 of this section

of the standard.




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6.8.2 General

(a) Compensating basins may either be steep sided and located in a fenced reserve or be unfenced

and located in POS or similar with side slopes suitable for public safety. The type chosen will

depend on a number of factors, one of which will be compatibility with the surrounding

development. The potential for water sensitive design opportunities, for water quality

improvement and for integration with recreational facilities shall be taken into account when

selecting the type of basin.

(b) Compensating basins offer opportunities to provide valuable visual and recreational amenity for

humans.

(c) If a compensating basin is to have a permanent water area, then objectives should be set as to

what functions (other than peak flow compensation) the basin should be designed to achieve.

These could include functions such as:

• enhancement of habitat area near an existing small isolated area of natural habitat.

• creation of a particular type and area of habitat which is not represented nearby

• re-creation of some of the original conditions if the basin is located in a severely degraded

area which was once a natural wetland.

(d) The agreement of the Local Authority shall be obtained for the type of basin to be used. The

Water Corporation does not take responsibility for the maintenance of flood plain areas of

unfenced compensating basins that are used as landscaped POS.

(e) Basins should be designed to either permanently contain water, at a minimum depth of 300 mm,

or to have a completely dry base surface in between times of inundation when flows are

compensated. Base flow pipes and sub soil drains may be required to maintain the dry

condition. The Design Engineer shall confirm that the groundwater level is suitable to maintain

the necessary minimum depth of water in the basin where shallow groundwater is the source of

the permanent water body. If the groundwater level is not suitable for long term maintenance of

a “permanent” water body within the basin then the basin shall be designed as a “dry" basin.

(f) For new works, the invert level of the outlet from a compensating basin shall be no lower than

the CGL for the site. .

(g) To allow for the control of basin water levels it is recommended that provision for stop boards

be incorporated into the structure where water leaves the basin. Particularly in regard to “wet”

basins, the ability to vary water level and also to completely drain the basin is a valuable

operational and management tool. To account for long term water table changes, it is

considered prudent to include provision for stop boards or other simple water level control

devices at all inlet and outlet structures. The necessity for stop boards shall be confirmed with

the Water Corporation during the preliminary investigations.

(h) Lateral connections to compensating basins shall be made in accordance with the Water

Corporation's standard details. Connections shall be trapped in accordance with Clause 6.9.2 of

this section of the standard.

(i) Drawings of typical structure arrangements are included in the Standard.

(j) The written approval of the Water Corporation's Manager, Infrastructure Design Branch shall

be obtained for the use of any alternative storage technique.




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(k) The potential for fire hazard in and around vegetated compensating basins must be recognized

and appropriate firebreaks provided.

6.8.3 Location

(a) Compensating basins shall be located only as follows:-

• in private property only if that property is owned by the Water Corporation or another

authority from which an easement allowing the basin to remain in perpetuity has been

obtained.

• in a reserve vested to the Water Corporation

• in a reserve vested to another authority if the area of the compensating basin is covered by

an easement to the Water Corporation.

(b) Compensating basins shall not be located in or intrude into any road reserve unless written

permission is obtained from the controlling authority before the proposal is submitted for

approval. A copy of such permission shall be included with any submission.

6.8.4 Land Requirements for Compensating Basins

(a) The land requirements for compensating basins shall be determined at the preliminary design

stage and the necessary land in fee simple or reserves shall be granted free of charge to the

Water Corporation as part of the land development process.

(b) Land for compensating basins is required for the following purposes:-

• For public safety, to enable restriction of access to the public where the compensating basin

is steep sided

• To protect the compensating basin from development proposals in perpetuity

• To allow for access to and maintenance of the compensating basin.

6.8.5 Requirements for Easements for Compensating Basins.

(a) The requirements for easements shall be determined at the stage of drain design and the

necessary easements shall be granted free of charge to the Water Corporation.

(b) Easements over compensating basins are required for the following purposes:

• To protect the compensating basin from adverse development proposals in perpetuity.

• To allow for access to and maintenance of the compensating basin.

(c) Compensating basins which are accessible to the public and which will be constructed in land

that will remain private property (refer Clause 6.8.3(a)) or land that will be vested to an

authority other than the Water Corporation shall be protected by an easement.

(d) The area of the easement for a compensating basin shall include all land not controlled by the

Water Corporation (except for road reserves) within the flood plain at the design water level for

minor storm event (1:10 years ARI) plus 300 mm. Refer to Clause 6.2.1.1 of this section.

6.8.6 Fenced Compensating Basins

(a) Steep sided compensating basins are discouraged. New proposals for steep sided basins will be

approved only where it can be demonstrated that other options are not appropriate.




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(b) Fenced compensating basins shall;

• be protected by a reserve or constructed in Water Corporation land as described in Clause

6.8.4 of this section.

• have side slopes no steeper than one vertical to one and one half horizontal.

• have a minimum maintenance berm width of 4.0 metres from the top of the compensating

basin bank to the boundary fence.

• be fenced as follows:

(i) Fencing should be in accordance with the standard fences detailed on drawings

GX54-4.2 & 4.3.

(ii) Urban

Rear and side of residential properties only - Free Standing Hardifence or

colourbond fence - 1.8 metre high.

Road frontages and public properties - Chainmesh Fence Type 1 – 1.8 metre high

(no barbed wire). If determined by the Water Corporation, at specific locations,

Chainmesh Fence Type 1 – 1.2 metre high (no barbed wire). Alternative fencing

arrangements to improve amenity or to provide a higher level of security (e.g.

Chainmesh Fence with Buried Selvedge Barbed Extension & Razor Wire at top and


(iii) Industrial

Chainmesh Fence Type 1 – 1.8 metre high (no barbed wire). Alternative fencing

arrangements to improve amenity or to provide a higher level of security (e.g.

Chainmesh Fence with Buried Selvedge Barbed Extension & Razor Wire at top and


• be provided with edge protection in accordance with Clause 6.6.12.2 of this section at

appropriate locations based on risk assessment. .

• have an earth access ramp at a slope no steeper than one vertical to four horizontal

• be designed with a view to keeping any base area that is normally dry, drained.

• be designed to incorporate a flood plain within adjacent POS. A fenced compensating

basin is provided with storage to cope with most storms up to the design storm, and by

dishing the surrounding parkland or by use of a natural depression, a flood plain can be

provided to accommodate the major event. The flood plain is thus available for

recreational use for most of the year.

6.8.7 Unfenced Compensating Basins

Compensating basins of the ornamental lake or dry basin types may be unfenced

6.8.7.1 Ornamental Lakes and Landscaped Basin

(a) In the case of an ornamental lake or landscaped basin, a maintenance agreement negotiated with

the Local Authority is required to be submitted with the submission.




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(b) The Water Corporation's responsibility shall be limited to the permanent water area, (i.e. below

the normal low water level), and main drainage structures, while the Local Authority shall be

responsible for the maintenance of the flood plain area, (usually as a part of the surrounding

POS), and all other structures.

(c) Where a maintenance agreement, satisfactory to the Water Corporation, cannot be negotiated

with the Local Authority, the basin shall be constructed in the form of a steep sided fenced

basin as described in Clause 6.8.6 of this section.

(d) The depth of the permanent water body in an ornamental lake or pond shall be a minimum of

300 mm.

(e) A typical example of an ornamental lake design is shown on drawing DG16-4-2. Typical

structure details are shown on drawing DG16-3-10. Refer to Figure 6.8 for a sketch of a typical

ornamental lake arrangement.

(f) Opportunities for water quality improvement within ornamental lakes shall be investigated by

the Design Engineer. Management practices should be implemented to restrict entry of trash,

litter and sediment and to prevent fertilizer enriched runoff from entering the lake and drainage

system.

6.8.7.2 Dry Basins

(a) In the case of a dry basin, a maintenance agreement shall be negotiated with the Local

Authority and the agreement is required to be submitted with the initial submission.

(b) The maintenance arrangement for a dry basin is normally that the Water Corporation's

responsibility is limited to the main drainage piping and structures, while the Local Authority

maintains the subsoil piping and the flood plain area, usually as part of the surrounding POS.

• Where such an arrangement is acceptable to the Local Authority, the basin shall be

protected by an easement to the Water Corporation. The easement requirements are

specified in Clause 6.8.5(d) of this section.

• Where such an arrangement is unacceptable to the Local Authority, the basin shall be

constructed in the form of a steep sided fenced basin as described in Clause 6.8.6 of this

section.

Figure 6.8: Typical Ornamental Lake




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(c) Subsoil drains shall be incorporated to facilitate a return to dry conditions after inundation.

(d) A typical example of a dry basin design is shown on drawing DG16-4-3. Typical structures are

shown on drawing DG16-3-10.

6.9 Connections

6.9.1 General

(a) An application shall be made in writing, to the Water Corporation, on the appropriate form for

any connection to an existing main drain or compensating basin. A copy of the form is in

section 9 in this standard.

(b) The connection of any conduit installed as an overflow or scour, to any main drain or

compensating basin shall be approved by the Operations staff in Perth Region.

(c) Any connecting structure within a Water Corporation drain reserve shall become the property

of the Water Corporation. Any part of the connection upstream of the drain reserve boundary

remains the property of the property owner or the Local Authority. Connection structures

within POS (including CB connections) remain the property of the property owner or Local

Authority

(d) Example arrangements of the connections of lateral or property drains are shown on Drawing

DG16-3-11.

(e) Any property connected to a main drain should have only one connection.

(f) The number of connections to main drains shall be kept to a minimum.

(g) Any connection of an open drain to a piped main drain shall be via a section of piped drain.

(h) All drains connecting into a main drain by a piped drain shall be trapped as specified in Clause

6.9.2 of this section of the standard.

(i) Drains carrying trade waste shall not be connected to a main drain. Prevention of accidental

overflow to a main drain shall be investigated by the Design Engineer. The design shall

incorporate any necessary safety features required by the Water Corporation.

(j) Backwash water from swimming pools is considered to be a trade waste.

6.9.2 Silt Trapping of Lateral or Property Drains

6.9.2.1 General

All lateral or property drains connecting into a main drain by a piped drain shall be trapped.

6.9.2.2 Connecting drains up to and including 600 mm nominal diameter

Connections, up to and including 600 mm nominal diameter, shall be trapped at the first access

chamber upstream of the connection point as follows:-

(a) Connections up to and including 300 mm nominal diameter are to be trapped with a TYPE A

trap access chamber as shown on Drawing DG16-3-20.

(b) Connections over 300 mm nominal diameter up to and including 600 mm nominal diameter are

to be trapped with a TYPE B trap access chamber as shown on Drawing DG16-3-20.




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(c) The trap access chamber shall be positioned as close as possible to the Main Drain but not

within Water Corporation property.

6.9.2.3 Connecting drains larger than 600 mm nominal diameter

(a) Connecting drains larger than 600 mm nominal diameter shall be trapped as follows:

• All gullies (or the downstream gully on a pair of gullies) and property drains connected to

the lateral drain shall be trapped, or

• Trap all drains, up to and including 600 mm nominal diameter, that are connected to the

lateral drain in accordance with Clause 6.9.2.2. Any gully or property drain directly

connected to the nominated lateral drain that is larger than 600 mm nominal diameter shall

also be trapped.

(b) Large special trap access chambers on the lateral drain will only be considered if the above

options are fully investigated and found to be impracticable.

6.10 Operational Requirements for Construction over or near Existing Water

Corporation Drains

The construction of, or alteration to, any building is subject to the approval of the Water Corporation

under Section 148 of the Metropolitan Water Supply, Sewerage and Drainage Act. Application shall

be made to the officer in control of "protection of services” in Perth Region to determine the Water

Corporation's requirements for the protection of any drainage infrastructure.

6.11 Engineering Design Process

The Corporation’s Engineering Design Process Manual of Requirements shall be used in the design of

Water Corporation’s engineering assets.

The manual describes the roles of the Corporation’s Design Manager and Designer in the design

process and provides or references:

• Design process guidance notes

• Templates for process documents and design outputs

Any submission of design work to the Water Corporation shall be carried out and delivered in

accordance with the current Engineering Design Process Manual.

Design work shall not be delegated to equipment suppliers or other contractors.

For issue of Engineering Design Process Manual and associated documents email request to

[email protected]

6.12 Environmental and Social Analysis

An environmental and social analysis shall be conducted and strategies to avoid or mitigate issues

/constraints shall be addressed by the Design Engineer as follows:

1. Environmental issues (including greenhouse gas abatement) or constraints (including social and

aboriginal and European heritage; Native Vegetation clearing) which may impact on the project

proceeding to acquisition or asset operation. The Corporation Planner’s Environmental

Checklist shall be used to identify environmental issues and constraints.




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2. Environmental risk assessment. Environmental risk assessments shall be conducted in

accordance with the Corporation Environmental Risk Assessment Package (ERAp).

The outcome of the ERAp will assist in the:

• Development of an environmental approvals strategy and programme.

• Provision of resources for the completion of the works.

• Identification of additional work requirements – surveys, studies and analyses for

assessment of project impacts, for example clearing.

• Identification of where the project is to be referred to either the Federal or State authorities

for assessment under the relevant environmental protection legislation.

Referral to the authorities is typically required where the environmental impacts cannot be managed

through avoidance, redesign or other mitigation measures.

• Development of the Construction Environmental Management Framework (CEMF) and

subsequent Construction Environmental Management Plan (CEMP)

At all times through project development (in both planning and scoping) the advice of the EIA &

Approvals Section in Environment Branch through the Manager, Development Services should be

sought with respect to the completion of the ERAp and obtaining the relevant environmental

approvals.

3. The assistance of EIA & Approvals Section in Environment Branch should be sought with

respect to referrals, outcome of referrals and correspondence with the Environmental

Protection Authority (EPA) and Department of Environment and Conservation (DEC).. All

communications and correspondence with the EPA and DEC shall be sent via the EIA &

Approvals Section and be in accordance with the documents referred to in the Corporation

Guidelines to the Environmental Approvals Process. It is important that the EIA & Approvals

Section is included in all communications to ensure that individual projects do not impact on

other works or become constrained by other developments with respect to environmental

approvals.

6.13 Safety Consideration

6.13.1 Safety

The adoption of the design requirements stated in this standard shall be assessed against the risk of

injuries to a person or a child that can be caused by the drainage infrastructure being designed which

include but not limited to the following.

- drowning due to unexpected rise in water level

- fall into drain due to inadequate edge protection

- fall due to slippery surfaces

- entry into drain pipe or conduit

- swept into pipes or conduit

- swept against safety screens or hard objects

- unauthorised entry into fenced area.




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- health issues arising from contaminated water.

The Design Engineer shall be responsible for assessment of these risks that could occur during

construction and operation stages of a main drain and inclusion of additional or upgraded design

requirements as necessary. Where drainage infrastructure is accessible to public, engagement of risk

professional skilled in public safety risk assessment is recommended to assess the risks and evaluate

the risk mitigation strategies.

The detailed information in Royal Life Saving Society Australia – Guidelines for Water Safety in

Urban Water Developments (2004) are to be considered in developing risk mitigation strategies

The following design criteria may be considered.

(a) Locate play areas and bicycle paths above the design top water level for 1:10 year ARI storm

events.

(b) Construct crossings in POS 300 mm above the design top water level for 1:100 year ARI storm

events.

(c) Provide edge protection from where a person could fall more than a meter. at a location where

the depth of water is not greater than 500mm.

(d) Provide child proof edge protection from where a child could fall more than 300 at locations

accessible to children.

(e) Ensure visibility of water from access to all crossings.

(f) Shape ground profile and/or change environments in and around structures, deep water areas

(greater than 400 mm at normal water level) and slopes steeper than 1V:6H by providing

appropriate fencing/edge protection or impenetrable vegetation. Interim fencing may be

required before establishment of vegetation.

(g) Avoid any features that invite or encourage access to water (purpose designed flora plants are

acceptable).

(h) Design the system to enable a person to readily exit a drain or a waterway before being

drowned or swept into unsafe areas such as pipe/culvert inlets.

(i) Avoid sudden change of water depth in open drains and compensating basins by limiting

embankment slopes and heights of any retaining system incorporated on the slopes.

(j) Provide benches of adequate width to

(k) Include Inlet screen or freeboard in culvert

Provide warning signs at appropriate locations in consultation with Local Authority to warn people of

possible dangers.

6.13.2 Risk Assessment

Risk assessment shall be carried out in accordance with AS/NZS ISO 3100 – Risk Management

Principles and Guidelines and the Water Corporation’s Risk Assessment guidelines.

6.13.3 Safety in Design

Designers shall provide the client with a written Report (Safety in Design Report) on the OSH aspects

of their design work in accordance with the requirements of WA OSH Regulation 3.140

(Responsibilities of Designers) and the National Standard for Construction Work 2008 (Designers,




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Clients and Contractors). The Water Corporations "Safety in Design" work instruction which provides

instruction on the compilation of this report can be found within the Engineering Design Process

referred to at Clause 6.11 of this section.

6.13.4 Signage

Signs shall be provided at drainage infrastructure in accordance with the requirements in Water

Corporation’s standard S197- Site Security, Public Safety and OSH Signage Standards.

6.13.5 Water Corporation Standards

The requirement in the following Water Corporation Standards/Guidelines shall be complied in

developing design for a main drain.

(a) S081- Site Security and Public Safety

(b) S389- Risk Assessment Criteria

(c) S151- Prevention of Falls Standard

(d) DS 62- Site Security & Public Safety Design Guidelines

(e) DS100 – Suspended Flooring (Grid Mesh and Chequer plate)

(f) S197 – Site Security, Public Safety and OSH Signage Standards

6.14 Services Crossing Water Corporation Land

6.14.1 General

(a) Services crossing under Water Corporation land shall have a minimum of 0.75 metre cover

unless approved otherwise by the Water Corporation. Services crossing open drains shall have

cover in accordance with Clause 6.6.9.2 of this section.

(b) Markers shall be provided at the location of all buried and above ground services crossing

Water Corporation land when required by the Water Corporation.

6.14.2 Location of Markers

Markers shall be located as follows:

(a) Above any buried service at points of entering or leaving the Water Corporation property

(b) Adjacent to any above ground service at points of entering or leaving the Water Corporation

property

(c) Above all horizontal changes of direction within Water Corporation property

(d) At points along the route at not greater distance than 200 metres between consecutive markers

or at any lesser distance when directed by the Water Corporation.

6.14.3 Marker Specification

(a) Where the authority responsible for the service being installed does not have a standard marker,

markers shall be similar to that shown in Figure 6.9 and shall:

(i) Be made from incombustible material




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(ii) Have legible permanent incombustible wording comprising:

• The name and phone number of the owner of the service

• A description of the service

• The depth of the service below ground level

(b) Details of the markers, their form of construction and the wording to be shown thereon shall be

submitted for approval and shall accompany the application for any service to cross Water

Corporation property.

Figure 6.9: Buried Service Marker Details

(c) Markers shall be oriented to be read from inside Water Corporation property.




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7 Design Drawings Criteria

7.1 Introduction

This part of the Standard specifies the Water Corporation's requirements for the preparation of design

drawings for the construction of drains.

Requirements for the design supplements as listed below are specified in Developers Manual.

(a) The surveyor's precalculated plan.

(b) The drainage development plan.

(c) The supplementary survey plan.

(d) The design calculations.

(e) The soils investigation report.

(f) The water quality management report.

7.2 Drawing Standards

(a) The drawings shall be prepared in accordance with the Water Corporation’s Design Standard

DS80.The drawing standards detailed in this Section shall also apply to all Design Drawings

and As Constructed Drawings.

(b) Drawings shall be similar to the drawing examples listed in Section 8 of this standard. They

shall comply with the requirements of this Section and contain relevant data similar to the data

shown on the examples.

(c) Drawings shall be numbered in accordance with the Water Corporation Design Standard DS80.

Figure 7.1

DM16-0-0A

Bundle

Sheet

Revision

Plan Set

(d) The Bundle number component of the Drawing Number (refer Figure 7.1) shall be in

accordance with the convention shown in Table 7.1




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Table 7.1

Bundle No. Type of Drawing

1 Locality Plans, Scheme Plans, etc.

2 Longitudinal Sections

3 Structures (includes Access chambers)

4 Compensating Basins

5 Pump Stations

6 Fencing

7 Flow Gauging

8 Criteria

9 Miscellaneous

(f) Drawings shall be A1 size (594 mm x 841 mm) to match the Water Corporation’s standard A1

sheet

(g) The standard of linework and lettering on drawings shall be suitable for legible reproduction

from microfilm. Lettering shall be in upper case with a minimum height of 2.5 mm on all

drawings except cadastral plans of scale 1:5000 or smaller, where for practical reasons, the

minimum size lettering shall be 2.0 mm.

(h) The Water Corporation's Plan - Bundle - Sheet numbers, file number, and if available, Capital

Investment Program Number, shall be shown on each drawing. See Drawing DG16-1-1

(Locality Plan, Example Drawing).

(i) Drawings shall have a north point and appropriate scale bars.

(j) Plans and details or sections on drawings shall be oriented so that the direction of flow is from

right to left.

(k) Street names and lot boundaries shall be shown along with the lot numbers of all lots affected

by the works.

(l) Levels shall be based on the Australian Height Datum (AHD) and shall be shown to the nearest

0.01 m.

(m) Contours shall be to AHD with a maximum interval of 0.5 m for plans to a scale of 1:1000, 1.0

m for plans to a scale of 1:2000 and 2.0 m for plans to a scale of 1:5000.

(n) Batters, slopes and grades shall be given as ratios of vertical distance to horizontal distance

with the vertical distance equal to unity.

(o) Pipe grades of 1:50 and steeper shall be shown to the nearest 0.1. Grades flatter than 1:50 shall

be shown to the nearest whole number.




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(p) The invert levels, sizes, positions and types of existing and proposed works and obstructions

shall be shown where applicable.

(q) Existing and proposed works, structure levels, services, existing surface levels and finished

surface levels shall be separately identified.

(r) Cut and fill shall be separately identified.

(s) A locality plan shall be included on the drawing where necessary.

(t) All reference drawings and standard drawings relevant to a particular drawing shall be listed on

that drawing.

(u) A "Dial Before You Dig" symbol shall be included on all Longitudinal sections, General

Arrangements and Site Plans.

(v) The notice shown in Figure 7.2, certifying that all services have been checked with the relevant

Authority, shall be included on a design drawing, preferably the Longitudinal Section. Where

there is no longitudinal section the notice shall be included on the Locality Plan if available or

otherwise on the site plan for the works.

(w) Warning notices shall be included on a drawing when applicable. See Figure 7.3 for example

notice. Refer to Clause 6.13.4 of section 6.

(x) A reference to any maintenance agreement affecting the proposal shall be included on any

relevant drawing.

Figure 7.2

Figure 7.3

7.3 Locality Plan

(a) The plan shall be similar to Drawing DG16-1-1 and shall be supplied when the longitudinal

section for the works is on more than one sheet.

(b) Where a longitudinal section is not required the supply of a separate Locality Plan is optional.

However, where a Locality Plan is not supplied, the requirements listed below shall be included

on whichever drawing is the most suitable.

All relevant authorities, including the Water Corporation

(Drainage, Sewerage & Water), Telstra, Western Power,

Alintagas, all other utilities and the Local Authority have

been advised of the proposal. Existing and proposed

services and works in the vicinity of the proposal have

been shown on this drawing. All requirements have been

complied with.

CERTIFIED…………………….DESIGN ENGINEER

DANGER

OVERHEAD & UNDERGROUND

POWER CABLES




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(c) The Locality Plan may be combined with the Design Data Plan. The title of the combined

drawing shall be Locality Plan and Design Data Plan.

(d) The scale should be 1:5000.

(e) The plan shall be orientated so that the direction of north is straight up the drawing and shall

include the following information:

• The routes of existing and proposed drains.

• Drain names and compensating basin names.

• Local Authority boundaries and the names of the relevant Local Authorities.

• The extent of each Longitudinal Section and a reference to the appropriate drawing number.

• A list of all drawings and standard drawings included in the submission, along with their

respective plan numbers.

7.4 Design Data Plan

(a) The plan shall be similar to Drawing DG16-1-2.

(b) The Locality Plan may be combined with the Design Data Plan. The title of the combined

drawing shall be Locality Plan and Design Data Plan.

(c) The scale should be 1:5000.

(d) The plan shall be orientated so that the direction of north is straight up the drawing.

(e) The plan shall indicate the basis of design for the section of drain being submitted and shall

show the following information:

(i) The routes of existing and proposed main and lateral drains and the boundary of the areas

served by the section of drain.

(ii) Ground level data showing:-

• Contours of the existing natural surface.

• The extent, level and contours (separately identified) of any proposed cut or fill.

• Surface levels at all significant low points within sub catchments.

• Ground water levels at relevant locations and the estimated maximum ground

water level contours if available.

(iii) Street names, lot boundaries and lot numbers.

(iv) Residential and non-residential areas defined separately.

(v) Boundaries of each of the internal sub catchments included in the catchment area (which

shall be separately identified) and their areas and runoff coefficients.

(vi) Flow direction and volume indicated by an arrowhead on the drain line and a number

giving the flow in litres per second at:-




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• Relevant design points. (Points of confluence or interest).

• Entry points for all gravity flows originating in the overall catchment but outside

the area being designed.

• Entry points for all pumped flows entering the area being designed.

(f) The following attachments shall be provided with the design data plan where applicable.

(i) For all compensating basins, an attachment containing the following design data:

• The design method

• Wet or Dry Basin

A Area of Catchment (ha)

C Weighted Coefficient of Runoff

S10 10 Year Storage Capacity Required (m3)


TWL10 10 Year Top Water Level (m AHD)


LWL Low Water Level (m AHD)

WSA Normal Water Surface Area (m2)

CGL Control Groundwater Level (m AHD)

• Any Additional Comments:

Time of Concentration

Runoff Coefficients

Groundwater assumptions

Actual Storage Volume to Design TWL (Sa)(m3)

Inflow (controlled or uncontrolled) (L/s)

Information on any outlet control device

Open drains not to be piped

Upstream Local Authority Compensating Basins to be retained

Soakage rate assumption

Extreme storm event comments (e.g. For 100 year storm event the Main

Drain will surcharge at certain locations, upstream and downstream of

compensating basins, hence TWL100 should be reassessed for artificial

compensation)




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Extent of vegetation plantings (e.g. reed beds) within the basin

(ii) For relevant design points, (points of confluence or interest), an attachment containing

the following design data:






TWL10 10 Year Top Water Level (AHD)






Runoff Coefficients

(iii) For the entry points of all gravity flows entering the area being designed from within the

overall catchment, an attachment containing the following design data:




Q Total Design Discharge (L/s)



TWL10 10 Year Top Water Level (AHD)







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Runoff Coefficients

(iv) An attachment, for the entry points of all pumped flows entering the area being designed,

containing the following design data:



As Area of Sub catchment (ha)


P Pump Rate (L\s)

7.5 Major Event Plan

(a) The plan shall be similar to Drawing DG16-1-3.

(b) The scale should be 1:1000 or 1:2000.

(c) The plan shall be orientated so that the direction of north is straight up the drawing.

(d) The plan shall summarise the design parameters, assumptions and calculations for a one in one

hundred year storm event.

(e) The plan shall show the route, and where property other than road or drainage reserves are

affected, the extent of the flow paths for the major event.

(f) The plan shall show the area flooded during a major event.

(g) The plan shall show ground level data including:-

(i) Contours of the existing natural surface.

(ii) The extent, level and contours (separately identified) of any proposed cut or fill.

(iii) Finished spot heights along the centreline of the flow path.

(iv) Street names, lot boundaries and lot numbers where lots are within the flow path or area

flooded.

(v) At relevant points on major flow paths, the direction of flow indicated by an arrowhead

in the flow path, the quantity of flow in m³/s, the velocity in m/s and the estimated flood

levels. For a compensating basin or low point the estimated flood level and the volume

stored in m3.

(vi) The outline and floor level of affected buildings and recommended minimum floor levels

for future buildings.




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7.6 Longitudinal Section

(a) The drawing shall be similar to Drawing DG16-2-1.

(b) The scales should be 1:1000 horizontal and 1:100 vertical.

(c) Distances and open drain base widths shall be in metres to the nearest 0.1m. Pipe, box culvert

and other conduit sizes shall be in millimetres.

(d) Batters, slopes and grades shall be given as ratios of vertical distance to horizontal distance

with the vertical distance equal to unity.

(e) The drawing shall include a plan covering the relevant section of drain and a longitudinal

section of the drain through the intersection points of all bends.

(f) The plan shall be oriented so that the downstream end of the drain is on the left hand side of the

drawing and shall show:-

(i) Existing and proposed drains.

(ii) Drain alignments and position of access chambers and structures.

(iii) Street names, lot boundaries, lot numbers and structure numbers.

(iv) The direction of north.

(v) Details of the existing drain to which the proposed drain will be connected.

(vi) Reserve and easement boundaries and dimensions where applicable.

(vii) All existing and proposed services and obstructions shall be shown and described.

(g) The longitudinal section shall have a Datum line related to AHD and shall be orientated so that

the downstream end of the section is on the left hand side of the drawing.

(h) The information shown below the Datum Line in tabular form on the longitudinal section, and

where applicable plotted on the section itself, shall include:-

(i) The running distance in metres with the lowest distance on the left. Distances at

structures are at pipe ends or at inside structure faces.

(ii) The natural surface level.

(iii) The finished surface level where it differs from the natural surface level.

(iv) The existing invert, when applicable.

(v) The designed invert.

(vi) The Hydraulic Grade Line for the design storm event.

(vii) The Hydraulic Grade Line for the 1 in 100 year storm event.

(i) The section itself shall be plotted to scale above the Datum line and shall depict:

(i) Existing and proposed surface levels.




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(ii) Existing and proposed inverts and crowns of all conduits.

(iii) Existing and proposed services and obstructions.

(iv) Existing and proposed connecting drains.

(v) The Hydraulic Grade Line for the design storm event.

(vi) The Hydraulic Grade Line for the one in one hundred year storm event.

(vii) Cut or fill.

(j) Shown above the longitudinal section in dimension form shall be the following information:-

(i) The location of the drain.

(ii) The pipe (or box culvert) size, type, class and grade shown above the dimension line and

the joint type (for Reinforced Concrete Pipes) shown below the dimension line.

(iii) A notation indicating where a particular type of pipe material is mandatory.

(iv) Open channel base width, side slope and grade.

(v) The design flow and velocity for each section of drain

(vi) A statement detailing the design basis of the drain.

(k) The following information shall be shown above the dimension lines referred to in the

preceding clause:-

(i) Structure type and number and a reference to the drawing detailing that structure.

(ii) The diameter, invert level and direction of any connection.

(iii) The angle of any bends in a pipe or open drain not at an access chamber or structure.

(l) Where a pipe drain consists of multiple pipes or conduits, or the pipe has special bedding a

typical cross section shall be drawn.

(m) Where an open drain or channel is lined, or is in fill, or has side slopes with more than one

batter a typical cross section shall be drawn.

7.7 Access Chambers, Splay Bends, Junctions and Intersecting Services

7.7.1 Access chambers

(a) For all access chambers fitting the standards, a detailed arrangement to a minimum scale of

1:25 shall be provided. The arrangement shall be similar to those shown on Drawing DG16-8-1

and shall include the following:-

(i) A plan of the access chamber showing the type of construction, the location of the

standard ladders and the corbel slab opening.

(ii) The location, size, class and invert level (to the nearest 0.1m) of all pipes and the

intersection of their centre lines at a common point known as the IP (intersection point).

For straight through access chambers with no inlets the centre of the access chamber can

be taken as the IP.




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(iii) The IP located with respect to cadastral boundaries and the access chamber dimensioned

about the IP.

(iv) The location of the access chamber cover relevant to cadastral boundaries.

(v) The Access Chamber Number, number of corbel slab, type of cover and any necessary

surround.

(vi) The proposed top of cover level.

(b) Any access chamber not fitting the standards or any non standard portion of an access chamber,

shall be fully detailed. A minimum of a plan and two views or sections shall be provided.

7.7.2 Splay Bends

(a) For all splay bends, a detailed arrangement to a minimum scale of 1:25 shall be provided. The

arrangement shall be similar to that shown on Drawing DG16-8-1 and shall show pipe size and

class, drain centreline, the offsets from cadastral boundaries, the IP (intersection point) and the

angle of the bend.

(b) A detail of each type of splay cut pipe (or box culvert) shall be provided.

(c) For elliptically reinforced drainage pipes, top of pipe shall be clearly indicated on any detail of

a splay cut pipe.

7.7.3 Junctions

All junctions not fitting the standards shown on Drawing DG16-3-20 shall be detailed.

7.7.4 Intersecting Services

Where other services intersect a drain a minimum of a plan and two views or sections shall be

provided.

7.8 Structures

(a) The drawing shall be similar to, or be a combination of, one or more of the example structure

Drawings DG16-3-10 to 3-15 and shall include a locality plan drawn to a suitable scale.

(b) The preferred scale is 1:25.

(c) The structure number shall be included in the title block and under each plan where more than

one structure is included on the drawing.

(d) The plan shall be orientated so that the direction of flow is from right to left and the following

complied with:-

(i) Structures shall be drawn to scale, fully dimensioned and located with reference to

cadastral boundaries.

(ii) A minimum of a plan and two views or sections are required.

(iii) Earthworks, fill, backfill, surface drainage, bank treatment and bank protection shall be

specified or detailed.

(iv) Construction materials, reinforcement, protective coatings on steel components,

foundations, compaction, concrete curing and formwork shall be specified.




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(v) Screens, gratings, ladders, stop boards and weepholes shall be detailed where applicable.

(vi) Any bridge, access way, occupational crossing shall be treated as a structure. Any

connection which is not covered by a standard drawing shall be treated as a structure.

7.9 Compensating Basins

(a) The drawing shall be similar to, or a combination of, one or more of the example compensating

basin Drawings DG16-4-1 to 4-3.

(b) The preferred scale is 1:250. The minimum scale is 1:1000.

(c) A minimum of a plan and one section shall be provided.

(d) Compensating basins shall be drawn to scale with the plan orientated so that the direction of

flow is from right to left. The following shall be complied with:-

(i) Adequate information for setting out the excavations shall be provided.

(ii) All pipes and structures shall be fully located. Banks, channels and subsoil drains shall

be detailed and dimensioned.

(iii) Top water level and low water level shall be specified.

(iv) The Control Groundwater Level (CGL) for the site shall be included on the drawing.

(v) Existing and proposed surface levels shall be shown and any earthworks, surface

drainage, bank treatment and protection, fencing and maintenance access shall be clearly

specified.

(vi) The design data for compensating basin as shown in Clause 7.4 of this section shall be

included on the drawing.

(vii) Staged construction shall be indicated where applicable.

(viii) The path and estimated water level for the design of major “event” shall be indicated on

the drawing.

(ix) Where the basin is required to provide a nutrient stripping function, the plan shall be

detailed to show the requirements of that function.

(x) The extent of any vegetation to be planted within the basin shall be included on the

drawing.

7.10 Open Drains and Natural Watercourses

(a) For reasons of clarity and ease of construction, open drains and drains affecting natural

watercourses require more detail than those shown on a longitudinal section. These details

shall be provided on additional drawings.

(b) The preferred scales are from 1:25 to 1:250. The minimum scale is 1:1000.

(c) Details are required of:-

(i) Fencing.

(ii) Protection of existing flora.




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(iii) Berm drainage.

(iv) Earthworks, levees and surface drainage connections through levees (including details or

specification of flap gate installation).

(v) Bank and toe protection.

(vi) Extents of planted vegetation (including reed beds, fringing vegetation and riffle zone

vegetation) required for water quality management purposes.




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8 Drawings

8.1 Metropolitan Main Drainage, Urban Main Drainage Standard -Drawings

The Title of the Plan Set for the Drawings is METROPOLITAN MAIN DRAINAGE, URBAN

MAIN DRAINAGE STANDARD -DRAWINGS. The Plan Set Number is DG16.

DRAWING ISSUE TITLE

DG16-1-1 B LOCALITY PLAN

EXAMPLE DRAWING

DG16-1-2 B STANDARD DATA PLAN

EXAMPLE DRAWING

DG16-1-3 B MAJOR EVENT PLAN

EXAMPLE DRAWING

DG16-2-1 B LONGITUDINAL SECTION

EXAMPLE DRAWING

DG16-2-2 C LAND SCAPED OPEN DRAINS AND SWALE DRAINS

EXAMPLE DRAWING

DG16-3-1 C STANDARD BRICK ACCESS CHAMBERS TO 2.4M DEEP

GENERAL ARRANGEMENT FOR PIPES UP TO 900MM NOMINAL

DIAMETER

DG16-3-2 C STANDARD BRICK ACCESS CHAMBERS FROM 2.4M TO 6.0M DEEP

GENERAL ARRANGEMENT FOR PIPES UP TO 2100MM NOMINAL

DIAMETER

DG16-3-3 NOT USED

DG16-3-4 B STANDARD BRICK ACCESS CHAMBERS

DETAILS OF CORBEL SLABS

DG16-3-5 C STANDARD BRICK ACCESS CHAMBERS TO 2.4M DEEP

DETAILS OF RC SURROUNDS

DG16-3-6 B STANDARD BRICK ACCESS CHAMBERS FROM 2.4M TO 6M DEEP

DETAILS OF ACCESS CHAMBER COVERS, FRAMES AND SURROUNDS

DG16-3-7 B STANDARD PRECAST RC ACCESS CHAMBER

GENERAL ARRANGEMENT

DG16-3-8 & 9 - FUTURE ISSUE

DG16-3-10 C STANDARD INLET AND OUTLET STRUCTURES

FOR UNFENCED COMPENSATING BASIS

DG16-3-11 C STANDARD CONNECTIONS (OUTLET STRUCTURES FROM PIPED

DRAINS)

FOR FENCED OPEN DRAINS AND FENCED COMPENSATING BASINS

DG16-3-12 B INLET STRUCTURE FOR FENCED COMPENSATING BASIN




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DG16-3-13 B STANDARD PIPE INLET STRUCTURE AND

TRASH RACKS AND SAFETY SCREENS

DG16-3-14 B OUTLET STRUCTURE

DG16-3-15 B STANDARD CONTROL STRUCTURES –SHEET 1 OF 2

DG16-3-16 A STANDARD CONTROL STRUCTURES SHEET 2 OF 2

DG16-3-17 B TOE PROTECTION

DG16-3-18 - FUTURE ISSUE

DG16-3-20 B STANDARD CUT IN JUNCTIONS FOR 150 – 675 DIA PIPES

AND TRAP ACCESS CHAMBES FOR 150 – 600 DIA PIPES

DG16-3-21 B SUBSOIL DRAINS

DG16-4-1 B FENCED COMPENSATING BASIN

EXAMPLE DRAWING

DG16-4-2 B ORNAMENTAL LAKE COMPENSATING BASIN

EXAMPLE DRAWING

DG16-4-3 B DRY COMPENSATING BASIN

EXAMPLE DRAWING

DG16-8-1 B ACCESS CHAMBER AND SPLAY BEND CRITERIA

DG16-8-2

TO

DG16-8-5

-

FUTURE ISSUE

DG16-8-6 B RESERVE AND EASEMENT CRITERIA FOR DRAINS

DG16-9-1 A STANDARD LADDER DETAILS

8.2 Reference Drawings

DRAWING ISSUE TITLE

GX54-4-2 A POOL TYPE, POST AND RAIL AND TWO RAIL CHAINWIRE FENCES.

GX54-4-3 A CHAINMESH TYP 1 AND FREE STANDING FENCES

GX54-5-1 A 1.8M CHAINWIRE FENCE WITH BURRIED SELVEDGE, BARBED

EXTENSION AND RAZOR WIRE AT TOP AND GROUND LEVEL.




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9 Application for Connection to Stormwater Main Drain

APPLICATION FOR CONNECTION TO STORMWATER MAIN DRAIN Please complete this form and return it together with two copies of Drawings of the proposed connection at least fourteen days prior to the commencement of work to:-

The drawings accompanying this form shall show the following:- 1. Dimensions to locate the connection horizontally with reference to cadastral boundaries. 2. Location of any trap access chambers/gullies and details of any proposed access chambers, gullies cut-in-junctions, or

structures that are not to Water Corporation standards. 3. Details of the connecting drain including size, type of pipe, invert levels together with gully levels and floor levels of

proposed and/or existing buildings. 4. The location and lot number of the property to be connected.

APPLICANT TO COMPLETE THIS SECTION

APPLICANT Name..................................................................................... Phone............................

Address ................................................................................. P’code ...........................

CONTRACTOR Name..................................................................................... Phone............................

Address ................................................................................. P’code ...........................

CONNECTION Location..............................................................................................................................

Nearest Intersection ...........................................................................................................

[ ]To Open Drain [ ] To Piped Drain [ ] To Access chamber [ ] To Exist. Structure [ ] To Comp. Basin

Signature of Applicant .............................................................................................. Date ..............................

OFFICE USE ONLY

Drain Name ..................................................................... No............................ File ................................

CONDITIONS OF APPROVAL [ / ] Your line is to discharge stormwater only. [ / ] Existing structures, access chambers and pipes are to be adequately protected during construction. [ / ] The connection shall be trapped in accordance with the Urban Main Drainage Standard. Trap access chambers shall be

in accordance with Drawing DG16-3-20 attached. Trap access chambers shall not be located within the Water Corporation drain reserve.

[ ] Piles must be used where your connecting drain crosses existing Water Corporation services. [ ] This connection will be constructed by Water Corporation staff at your cost. [ ] Details of connecting structure attached [ ] This connection will be constructed by the contractor nominated above. [ ] ..Special Conditions ............................................................................................................................................... ............................................................................................................................................................................. .............................................................................................................................................................................

This application is valid until …./…./….

In order for necessary inspections to be made, please contact …………………………………………………..

on …………………………. at least two days prior to the commencement of work

APPROVED BY............................................................................................................ Date……………………

Team Leader Network Expansion PO Box 100, LEEDERVILLE, WA 6902 Development Services Branch Water Corporation John Tonkin Water Centre 629 Newcastle Street, Leederville PO Box 100 LEEDERVILLE WA 6902




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10 Glossary

In the standard the following words, expressions and abbreviations shall have the meanings or

interpretations assigned to them below and do not necessarily apply to the meanings or interpretations

given in any relevant legislation or other Water Corporation publications.

Access Chamber A chamber constructed in a piped drainage system in which a person can

enter to inspect or maintain the drain

AHD Australian Height Datum

AMG Australian Mapping Grid

Area Served The area served by a section of drain is the area from which water flows or

can be made to flow to the section of drain concerned

ARI Average Recurrence Interval

ARR97 Australian Rainfall & Runoff, 1997 Revision

ARRB Australian Road Research Board

Arterial Drain An arterial drain is an existing or proposed conduit or channel, whether

nature or constructed, which is essential to the safe discharge of surplus

stormwater, now or in the future.

It is a planned drainage facility which, if limited or restricted by land use

developments, would result in significant storm flow damage to existing or

future residential or commercial property development, or have social and/or

environmental consequences for a community if not adequately managed or

maintained.

* All Water Corporation main drains are Arterial Drains or portions of

Arterial Drains

* A drain or drainage course becomes an Arterial Drain when designated as

such by the Department of Water, acknowledged by the responsible Local

Authority and is shown on the Arterial Drainage Scheme Plan compiled by

the Department of Water

* An Arterial Drain is not necessarily controlled by the Water Corporation

but may be comprised wholly or partially of drains for which Local

Authorities or other bodies are responsible

Arterial Drainage

Scheme

The arterial drainage scheme is a legislative responsibility of the Department

of Water whereby, practical and economic provision is made, by, on behalf

of, or in consultation with, the Department of Water the planning,

management, maintenance, financing extending and improving of drainage

services to serve the Perth Metropolitan Scheme Area

Arterial Drainage

Scheme Plan

The arterial drainage scheme plan is a document compiled by the

Department of Water and amended and reviewed from time to time to show

the essential components of the Scheme including:

* Drainage catchments

* Lakes, swamps, wetlands, watercourses and other features related to

natural drainage

* Areas of existing, proposed and potential development

* The major components of the existing drainage systems identifying arterial




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drains and differentiating as to the kinds of drains

* Declared drainage courses

* The major components of the proposed drainage systems identifying

arterial drains and differentiating as to the kinds of drains and the persons

or bodies to be liable for the provision and maintenance of that drainage

* Land subject to a charge and land likely to be subject to a charge (existing

or proposed Drainage Areas) by the Water Corporation for main drainage

Australian Height

Datum

Australian height datum is the datum that shall be used for all levels

included in any submission to the Water Corporation

Biotic Relating to living things or to biological matter

Branch Drain See Main Drain

CALM Department of Conservation and Land Management

Catchment The catchment of a drain or section of drain is the area of land from which

water flows or can be made to flow to a main drain or pumping station by

gravity drains

CB Compensating Basin

Compensating

Basin

A compensating basin is a drainage structure or feature that is designed to

delay the passage of stormwater by providing surcharge storage

Concept(ual) plan A preliminary plan of a development or proposed works showing general

elements only and how they inter-relate. Is usually a precursor to more

detailed planning and/or design

Conduit A conduit is a pipe, tunnel or artificial channel above, on or under the

ground used or intended to be used for the conveyance of surplus water.

Connection A connection is the structure or fitting by or at which a non Water

Corporation drain is connected to a main drain

CGL Control Groundwater Level determined following the requirements of the

Department of Water. Values used for CGL shall be to the approval of the

Department of Water.

Department of Water A department of the government of Western Australia

Design Engineer The Engineer or Engineering firm appointed by the Principal to design a

drainage system for submission to the Water Corporation

Detention basin A compensating basin – a drainage structure or feature that is designed to

delay the passage of stormwater by providing surcharge storage

Developer The person or organization that has made an arrangement with the Water

Corporation to provide drainage infrastructure

Developers

Manual

A manual published by the Water Corporation

Development Proposed works that will alter the pre-existing natural or built environment

Distance between

access chambers

The distance between access chambers is the horizontal length between the

intersection points of drains at access chambers or the centre points of

straight through access chambers measured through the intersection points of

any intermediate bends

Drain A drain is a conduit that may be used permanently or intermittently or a




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watercourse or other natural channel, used or intended to be used for the

removal of surplus storm water or for the diversion of water that might flow

onto any land and includes compensating basins structures and other

appurtenances used in connection with such a conduit

Drainage Area A Drainage Area is an area of land in the State of Western Australia

declared by legislation to be a drainage area

Drop Structure A drop structure is a structure provided on an open drain or channel that

achieves an immediate or sudden or local drop in the invert level of that

drain or channel

Edge Protection Edge protection is used to reduce the risk of fall of a person from one level

to another.

Engineer A person qualified to be a Chartered Professional Engineer and who has

appropriate engineering experience

Engineering firm An organization which has in its employment an Engineer

Floodway The floodway of an open drain or a landscaped open drain is that part of the

waterway required to carry the stormwater when the capacity of the base

flow channel or low flow pipe is exceeded

Freeboard The freeboard for any particular section of drain is the vertical distance from

the lowest natural surface level at that section to the design top water level at

that section

Gauging weir A gauging weir is a structure provided on a channel that is fitted with a

gauge and a means of measuring the flow in that channel

Greenbelt A relatively wide strip of undeveloped, reserved land in an urban area that

acts as a barrier or provides a break to unrestricted urban expansion

Groundwater Water that occupies the pores and cavities within the soil and rocks of the

earth’s surface. Bouwer1

states that not all underground water is

groundwater. Groundwater has a pressure that is greater than atmospheric

pressure – it will flow freely into a hole exposed to atmospheric pressure.

HGL Hydraulic Grade Line

IFD Intensity Frequency Duration

IL Invert Level

IMEA Institute of Municipal Engineering Australia

Industrial waste Industrial wastes include all waterborne waste, discharged from an industrial

process or other waterborne waste except waste of the kind and quality

ordinarily discharged from residential premises.

Inlet structure An inlet structure is a structure provided at the upstream end of a conduit,

pipe drain or culvert.

Invert level The invert level is the lowest level of a drain at any particular cross section

IP Intersection Point

Junction A junction is a fitting provided in a conduit or pipe drain to allow for the

connection of a lateral drain

Landscaped

natural

watercourse

A landscaped natural watercourse when used as a Water Corporation Main

Drain consists of a natural watercourse that is combined with a grassed

floodway to dispose of the runoff of flows from storms greater than the

minor design storm event




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Landscaped open

drain

A landscaped open drain when used as a Water Corporation Main Drain is

an unfenced publicly accessible open drain that comprises a landscaped

floodway and an incorporated base flow channel flow pipe

Lateral drain A lateral drain is any stormwater drain, that is not controlled by the Water

Corporation, which is connected to a main rain

LWL Low Water Level

Main Drain A main drain is an existing of proposed drain within the Metropolitan Area

that is declared under legislation and controlled by the Water Corporation.

Any Branch Drain that has been declared as above is also a Main Drain.

Major event A major event is a large magnitude storm during which stormwater flows

exceed the designated level of service capacity of any part of a drainage

system operated by the Water Corporation and the resulting stormwater

overflow has the potential for damage to life or property

Major system ARR87 defines the major drainage system as the many planned and

unplanned drainage routes which convey runoff arising from major storms.

The major drainage system generally follows the natural pattern, sometimes

causing damage along the way.

Metropolitan Area The Metropolitan Area is the area encompassed by the boundary of the Perth

Metropolitan Region Planning Scheme.

MH or AC Access chamber

Minor event A minor event is a relatively small magnitude storm during which

stormwater flows are normally contained within the designated level of

service capacity of any part of a drainage system operated by the Water

Corporation.

Minor system ARR87 defines the minor drainage system as the gutter and pipe network

capable of carrying runoff from minor storms. The routes of minor systems

may differ from the natural drainage path, to conform with street layouts and

other obstructions

MRWA Main Roads Western Australia

Outlet structure An outlet structure is a structure provided at the downstream end of a

conduit or pipe drain

PAW Pedestrian Access Way

Pollution Pollution is the addition to or concentration in the environment, by direct or

indirect means, or any dangerous, injurious or obnoxious substance, whether

solid or liquid or gaseous

POS Public Open Space

Predevelopment

conditions

Conditions that prevail prior to a development

Principal The person, organization, Local Authority or Government Authority

responsible for funding the construction of a main drainage scheme

Property drain A property drain is a drain that connects a property to a main drain or a

lateral drain. (A property drain is also a lateral drain)

Proponent A key stakeholder in the process of land development or development of

proposed works. The proponent is usually the initiator of a particular

proposal (cf. service provider, approval agencies). The proponent may be a

person, Local Authority, Government Authority, agency or organisation




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(including the Water Corporation) that proposes a scheme to be

implemented. The proponent is generally responsible for stewardship of

development of the scheme.

Runoff Stormwater that exceeds interception losses and “runs off” into the drainage

system

Sedges Plants of the family Cyperaceae, mostly herbs (plants which do not produce

a woody stem), can be tall and grass-like (such as papyrus) common to damp

habitats and wetlands

Shall Shall refers to a mandatory requirement

Should Should, refers to a requirement to be adopted unless circumstances justify a

variation. Any variation shall be approved by the Water Corporation.

Siltation Accumulation of sediments deposited by moving water

Stakeholders Any person, organization, landowner, agency or authority that will be

affected by or has a significant interest in the outcomes of a development

Structure plan A broad development plan which generally forms the basis of an application

for rezoning of land. Describes how the land is to be allocated between

various uses and how the various services (roads, drainage, etc) are to be

provided

Surplus water Surplus water is storm water, surface water or underground water which

accumulates or may accumulate to the detriment or disadvantage of any

person or property

Swale A natural swale is a linear depression formed by wind erosion or by the build

up of ridges either side of an area of land. Swale drains are shallow

depressions or channels of linear form with gentle side slopes used for

collecting, treating and transporting stormwater runoff.

TWL Top Water Level

WANG West Australian Natural Gas

WAPC Western Australian Planning Commission

Waste Waste includes any matter or thing of whatever kind or in whatever form

that if discharged, causes or is likely to cause pollution and also includes any

matter or thing described in the bylaws to be waste.

Water Corporation Water Corporation is the body corporate known as the Water Corporation of

Western Australia

Water Sensitive

Urban Design Water Sensitive Design is a design philosophy and techniques which aim to

harmonise urbanization and effective water resource management:

* to reduce changes to natural water balances that affect aquifer recharge

and wetland ecology,

* to protect groundwater, surface waterways and wetlands from urban

pollution,

* to promote urban forms that encourage water conservation

Works Works are defined as any physical activity carried out to construct, operate,

maintain or remove any structure or asset of a main drainage system

WSUD Water Sensitive Urban Design

Zone of

construction

Zone of construction is the cross section of earth about the centreline of a

main drain that is deemed to be disturbed during the construction of that

main drain




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