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Acquisition Group Infrastructure Design Branch
Design Standard No. DS66
Urban Main Drainage Standard
VERSION 2
REVISION 0
30 JUNE 2011
Design Standard DS 66
Urban Main Drainage Standard
Uncontrolled if Printed Page 2 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.
Design Standard DS 66
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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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Urban Main Drainage Standard
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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
2 1/0 02.98 All New Version SS
1 2/0 30.06.11 All New version, Reformatted,
renamed section 1Edited clauses
1.1 & 1.3
SS PF
3 1/0 02.98 All New Version SS
2 2/0 30.06.11 All New version, Reformatted,
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
3 2/0 30.06.11 All New version, Reformatted,
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
4B 1/1 03.00 4B.4 2.1-2.4 amended to comply with
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
4B 1/1 03.00 4B.16 6.1-6.4 amended to comply with
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
REVISION DESCRIPTION RVWD. APRV.
4 2/0 30.06.11 All New version, Reformatted,
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
5 2/0 30.06.11 All New version, Reformatted,
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
6 2/0 30.06.11 All New version, Reformatted,
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
6 1/0 02.98 All New Version SS
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SECT. VER./
REV.
DATE PAGES
REVISED
REVISION DESCRIPTION RVWD. APRV.
7 2/0 30.06.11 All New version, Reformatted,
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
8 2/0 30.06.11 All New version, Reformatted,
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
9 2/0 30.06.11 All New version, Reformatted,
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
10 2/0 30.06.11 All New version, Reformatted,
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.
Design Standard DS 66
Urban Main Drainage Standard
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© Copyright Water Corporation 1991-2011
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.
Design Standard DS 66
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Ver 2 Rev 0
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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:
Horizontal ± 0.020 m Vertical ± 0.005 m.
(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:
Horizontal ± 0.01 m Vertical ± 0.01 m.
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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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
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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
ground level- Drawing GX54-5-1) may be considered by the Water Corporation.
(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
ground level- Drawing GX54-5-1) may be considered by the Water Corporation.
• 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
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)
S100 100 Year Storage Capacity Required (m3)
TWL10 10 Year Top Water Level (m AHD)
TWL100 100 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:
• The design method
A Area of Catchment (ha)
C Weighted Coefficient of Runoff
S10 10 Year Storage Capacity Required (m3)
S100 100 Year Storage Capacity Required (m3)
TWL10 10 Year Top Water Level (AHD)
TWL100 100 Year Top Water Level (m AHD)
LWL Low Water Level (m AHD)
CGL Control Groundwater Level (m AHD)
• Any Additional Comments:
Time of Concentration
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:
• The design method
A Area of Catchment (ha)
C Weighted Coefficient of Runoff
Q Total Design Discharge (L/s)
S10 10 Year Storage Capacity Required (m3)
S100 100 Year Storage Capacity Required (m3)
TWL10 10 Year Top Water Level (AHD)
TWL100 100 Year Top Water Level (m AHD)
LWL Low Water Level (m AHD)
CGL Control Groundwater Level (m AHD)
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• Any Additional Comments:
Time of Concentration
Runoff Coefficients
(iv) An attachment, for the entry points of all pumped flows entering the area being designed,
containing the following design data:
• The design method
A Area of Catchment (ha)
As Area of Sub catchment (ha)
C Weighted Coefficient of Runoff
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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© Copyright Water Corporation 1991-2011
END OF DOCUMENT