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Track Drainage
T HR CI 12130 ST
Standard
Version: 2.0
Issue date: 18 December 2019
© State of NSW through Transport for NSW 2019
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T HR CI 12130 ST Track Drainage
Version: 2.0 Issue date: 18 December 2019
Important message This document is one of a set of standards developed solely and specifically for use on
Transport Assets (as defined in the Asset Standards Authority Charter). It is not suitable for any
other purpose.
The copyright and any other intellectual property in this document will at all times remain the
property of the State of New South Wales (Transport for NSW).
You must not use or adapt this document or rely upon it in any way unless you are providing
products or services to a NSW Government agency and that agency has expressly authorised
you in writing to do so. If this document forms part of a contract with, or is a condition of
approval by a NSW Government agency, use of the document is subject to the terms of the
contract or approval. To be clear, the content of this document is not licensed under any
Creative Commons Licence.
This document may contain third party material. The inclusion of third party material is for
illustrative purposes only and does not represent an endorsement by NSW Government of any
third party product or service.
If you use this document or rely upon it without authorisation under these terms, the State of
New South Wales (including Transport for NSW) and its personnel does not accept any liability
to you or any other person for any loss, damage, costs and expenses that you or anyone else
may suffer or incur from your use and reliance on the content contained in this document. Users
should exercise their own skill and care in the use of the document.
This document may not be current and is uncontrolled when printed or downloaded. Standards
may be accessed from the Transport for NSW website at www.transport.nsw.gov.au
For queries regarding this document, please email the ASA at [email protected] or visit www.transport.nsw.gov.au © State of NSW through Transport for NSW 2019
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T HR CI 12130 ST Track Drainage
Version: 2.0 Issue date: 18 December 2019
Standard governance
Owner: Lead Civil Engineer, Asset Standards Authority
Authoriser: Chief Engineer, Asset Standards Authority
Approver: Executive Director, Asset Standards Authority on behalf of the ASA Configuration Control Board
Document history
Version Summary of changes
1.0 First issue 9 Apr 2015
2.0 Second issue. Changes include: design and documentation of subsurface drainage pipes; track drainage near turnouts or special trackwork; pipe culverts that cross the rail corridor; pipe lining repairs; integration with T HR CI 12130 MA; integration with T HR CI 12002 ST and the associated technical note TN 042: 2017; other minor revisions.
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T HR CI 12130 ST Track Drainage
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Preface The Asset Standards Authority (ASA) is a key strategic branch of Transport for NSW (TfNSW).
As the network design and standards authority for NSW Transport Assets, as specified in the
ASA Charter, the ASA identifies, selects, develops, publishes, maintains and controls a suite of
requirements documents on behalf of TfNSW, the asset owner.
The ASA deploys TfNSW requirements for asset and safety assurance by creating and
managing TfNSW's governance models, documents and processes. To achieve this, the ASA
focuses on four primary tasks:
• publishing and managing TfNSW's process and requirements documents including TfNSW
plans, standards, manuals and guides
• deploying TfNSW's Authorised Engineering Organisation (AEO) framework
• continuously improving TfNSW’s Asset Management Framework
• collaborating with the Transport cluster and industry through open engagement
The AEO framework authorises engineering organisations to supply and provide asset related
products and services to TfNSW. It works to assure the safety, quality and fitness for purpose of
those products and services over the asset's whole-of-life. AEOs are expected to demonstrate
how they have applied the requirements of ASA documents, including TfNSW plans, standards
and guides, when delivering assets and related services for TfNSW.
Compliance with ASA requirements by itself is not sufficient to ensure satisfactory outcomes for
NSW Transport Assets. The ASA expects that professional judgement be used by competent
personnel when using ASA requirements to produce those outcomes.
About this document
This standard specifies the life cycle (design, construction and installation, maintenance,
decommissioning and disposal) requirements for track drainage on the TfNSW Metropolitan
Heavy Rail Network.
This standard is a second issue and changes to the previous version include the following:
• design and documentation of subsurface drainage pipes
• track drainage near turnouts or special trackwork
• pipe culverts that cross the rail corridor
• pipe lining repairs
• integration with T HR CI 12130 MA Track Drainage manual requirements
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T HR CI 12130 ST Track Drainage
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• integration with T HR CI 12002 ST Durability Requirements for Civil Infrastructure and the
associated technical note TN 042: 2017
• other minor revisions
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Table of contents 1. Introduction .............................................................................................................................................. 8
2. Purpose .................................................................................................................................................... 8 2.1. Scope ..................................................................................................................................................... 8 2.2. Application ............................................................................................................................................. 9
3. Reference documents ............................................................................................................................. 9
4. Terms and definitions ........................................................................................................................... 13
5. Risk and safety ...................................................................................................................................... 14 5.1. Risk assessment .................................................................................................................................. 15
6. Environment ........................................................................................................................................... 15
7. Heritage .................................................................................................................................................. 16
8. Approved materials ............................................................................................................................... 17 8.1. New and infrequently used materials .................................................................................................. 18
9. General design requirements ............................................................................................................... 19 9.1. Stormwater discharge .......................................................................................................................... 19 9.2. Restrictions and constraints................................................................................................................. 20 9.3. Drainage system type .......................................................................................................................... 21 9.4. Trackside structures ............................................................................................................................ 22 9.5. Multiple tracks ...................................................................................................................................... 22 9.6. Drainage design life ............................................................................................................................. 23 9.7. Design average recurrence interval ..................................................................................................... 23 9.8. Peak flow rate ...................................................................................................................................... 24 9.9. Prohibited configurations ..................................................................................................................... 24
10. Surface drainage.................................................................................................................................... 25 10.1. Cess drains ...................................................................................................................................... 26 10.2. Catch drains ..................................................................................................................................... 27 10.3. Mitre drains ...................................................................................................................................... 27
11. Subsurface drainage ............................................................................................................................. 27 11.1. Design traffic loads .......................................................................................................................... 28 11.2. Pipes ................................................................................................................................................ 28 11.3. Repairs to existing pipe culverts ...................................................................................................... 31 11.4. Trenching and backfill ...................................................................................................................... 32 11.5. Pipe embedment .............................................................................................................................. 33 11.6. Inlets and outlets .............................................................................................................................. 34 11.7. Pits ................................................................................................................................................... 35 11.8. Aggregate drains ............................................................................................................................. 37 11.9. Flushing points ................................................................................................................................. 38 11.10. Geotextiles ....................................................................................................................................... 38 11.11. Turnouts and special trackwork ....................................................................................................... 39
12. Documentation requirements ............................................................................................................... 41 © State of NSW through Transport for NSW 2019 Page 6 of 48
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12.1. Drawings .......................................................................................................................................... 41 12.2. As-built drawings ............................................................................................................................. 43 12.3. Reports ............................................................................................................................................ 43 12.4. Asset management .......................................................................................................................... 44 12.5. Plastic drainage product approval ................................................................................................... 44
13. Construction .......................................................................................................................................... 44
14. Maintenance ........................................................................................................................................... 44
15. Decommissioning or disposal ............................................................................................................. 45
Appendix A Product approval specification – plastic drainage products ........................................ 46
Appendix B Critical zones for a turnout ............................................................................................... 48
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1. Introduction Track drainage systems divert stormwater and groundwater away from track formation and the
supporting ground and mitigate track flooding. For typical ballasted track, rainfall percolates
through the ballast and is directed sideways over the soil capping layer of the formation and
then away into the track drainage system. Without adequate track drainage, the track formation
may become saturated and weakened, which can lead to failure. Formation failure may be
indicated by mud pumping up through the ballast, repeated vertical and horizontal track
alignment problems, heaving or settlement.
Typical track drainage systems comprise surface types such as cess drains, catch drains, mitre
drains or grated drains, and subsurface types such as below ground pipes, pits and aggregate
drains.
External stormwater drainage systems that cross from one side of the rail corridor to the other
require structures such as box culverts, pipe culverts, open channels and underbridges
spanning natural watercourses and constructed floodways. The primary function of these
drainage structures is not track drainage; however, they are often used as an outlet for track
drainage rail infrastructure.
Regular inspection, examination, routine maintenance and repairs when required of drainage
systems are essential to maintaining the integrity of track formation, supporting embankments
and cuttings.
2. Purpose This standard specifies the design, construction and installation, maintenance,
decommissioning and disposal requirements for track drainage systems on the TfNSW
Metropolitan Heavy Rail Network (formerly known as the RailCorp network).
2.1. Scope This standard provides the requirements for track drainage within the rail corridor of the TfNSW
Metropolitan Heavy Rail Network and includes surface and subsurface stormwater drainage of
the track formation, supporting embankments and cuttings. Refer to TS TOC 1 Train Operating
Conditions (TOC) Manual – General Instructions, which defines the areas associated with the
network.
This standard covers the following:
• track drainage surface drains (including cess drains, catch drains and mitre drains)
• track drainage subsurface drains (including pipe culverts and aggregate drains)
• repairs and linings to existing pipe culverts
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• subsurface drainage pipe culverts (associated loading, pipe, trenching, backfill,
embedment, inlet, outlet and pit requirements) for:
o access road pipe culverts within the rail corridor
o other drainage pipe culverts that cross the rail corridor such as regional or council
stormwater drains
This standard does not cover the following:
• waterway and flood design for all other (non-track drainage) culverts; refer to
T HR CI 12020 ST Underbridges, T HR CI 12110 ST Earthworks and Formation,
T HR CI 12200 ST Access Roads and T HR CI 12190 ST Service Installations within the
Rail Corridor for these requirements
• box and arch culvert structural design or selection; refer to T HR CI 12020 ST for these
requirements
• track formation design; refer to T HR CI 12110 ST for these requirements
This standard does not cover drainage design for bridges, structures and buildings within or
properties outside the rail corridor; however, associated stormwater run-off and track drainage is
covered.
2.2. Application This standard applies to service providers and particularly civil engineering designers for track
drainage on the TfNSW Metropolitan Heavy Rail Network.
In addition to the requirements of this standard, asset decisions need to take into account the
life cycle cost considerations specified in T MU AM 01001 ST Life Cycle Costing.
This standard applies to new track drainage installations and modifications to existing track
drainage.
When using this standard, if it is considered that the intent of stated requirements is not clear,
clarification should be obtained from the Lead Civil Engineer, Asset Standards Authority (ASA).
Where a conflict in requirements exists between this standard and any other referenced
standard or document, this standard takes precedence.
3. Reference documents The following documents are cited in the text. For dated references, only the cited edition
applies. For undated references, the latest edition of the referenced document applies.
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Australian standards
AS 1657 Fixed platforms, walkways, stairways and ladders - Design, construction and
installation
AS 3572 Plastics - Glass filament reinforced plastics (GRP) – Methods of test
AS 3600 Concrete structures
AS 3706 Geotextiles – Methods of test
AS 3996 Access covers and grates
AS 4100 Steel structures
AS 4139 Fibre-reinforced concrete pipes and fittings
AS 4678 Earth-retaining structures
AS 4799 Installation of underground utility services and pipelines within railway boundaries
AS 5100 Bridge design
AS/NZS 2566.1 Buried flexible pipelines – Part 1: Structural design
AS/NZS 2566.2 Buried flexible pipelines – Part 2 Installation
AS/NZS 3725 Design for installation of buried concrete pipes
AS/NZS 4058 Precast concrete pipes (pressure and non-pressure)
Transport for NSW standards
ESC 200 Track System
ESC 215 Transit Space
ESC 302 Structures Defect Limits
ESC 520 Level Crossings
MN A 00100 Civil and Track Technical Maintenance
SPC 207 Track Monitoring Requirements for Undertrack Excavation
SPC 301 Structures Construction
T HR CI 12002 ST Durability Requirements for Civil Infrastructure
T HR CI 12008 ST Capacity Assessment of Underbridges
T HR CI 12020 ST Underbridges
T HR CI 12030 ST Overbridges and Footbridges
T HR CI 12080 ST External Developments
T HR CI 12101 ST Geotechnical Problem Management
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T HR CI 12110 ST Earthworks and Formation
T HR CI 12111 SP Earthwork Materials
T HR CI 12130 MA Track Drainage
T HR CI 12190 ST Service Installations within the Rail Corridor
T HR CI 12200 ST Access Roads
T HR EL 12002 GU Electrolysis from Stray DC Current
T MU AM 01001 ST Life Cycle Costing
T MU AM 01003 ST Development of Technical Maintenance Plans
T MU CI 12140 GU Geotechnical Instrumentation and Monitoring Guidelines
T MU MD 00005 GU Type Approval of Products
T MU MD 00006 ST Engineering Drawings and CAD Requirements
T MU MD 20001 ST System Safety Standard for New or Altered Assets
T MU MD 20002 ST Risk Criteria for Use by Organisations Providing Engineering Services
TMC 302 Structures Repair
TS TOC 1 Train Operating Conditions (TOC) Manual - General Instructions
Transport for NSW drawings
CV 0115011 Ballast retaining wall
CV 0205421 Track Drainage - Typical Sections and Notes
CV 0277517 'L' Retaining Wall - Type 1
CV 0400998 Ballast Cage (Lobster Pot) with Removable Lid
CV 0497068 Pipe Culverts Headwalls to Suit Pipes 225-600 mm Diameter
CV 0497069 Pipe Culverts Headwalls to Suit Pipes 675-1800 mm Diameter
CV 0517943 Single Pipe Headwall to Suit Pipes 225-600 mm Diameter
CV 0517944 Single Pipe Headwall to Suit Pipes 675-600 mm Diameter
CV 0517945 Twin Pipe Headwall (Splayed Wings) to Suit Pipes 225-600 mm Diameter
CV 0517946 Twin Pipe Headwall (Splayed Wings) to Suit Pipes 675-1800 mm Diameter
CV 0517947 Twin Pipe Headwall (Straight Wings) to Suit Pipes 225-600 mm Diameter
CV 0517948 Twin Pipe Headwall (Straight Wings) to Suit Pipes 675-1800 mm Diameter
Legislation
Heritage Act 1977
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Work Health and Safety Act 2011
Other reference documents
Australian Rainfall and Runoff (ARR): Ball J, Babister M, Nathan R, Weeks W, Weinmann E,
Retallick M, Testoni I, (Editors), Australian Rainfall and Runoff: A Guide to Flood Estimation,
Commonwealth of Australia (Geoscience Australia)
NSW Government, Safe design of structures code of practice (available from SafeWork NSW)
Office of Environment and Heritage 2005, State Agency Heritage Guide – Management of
Heritage Assets by NSW Government Agencies
Office of Environment and Heritage, State Heritage Register
RailCorp Section 170 Heritage and Conservation Register
RailCorp Section 170 Heritage and Conservation Register - Movable heritage
RMS QA Specification 3552 Subsurface drainage pipe (Corrugated Perforated and Non-
Perforated Plastic)
RMS QA Specification 3553 Seamless Tubular Filter Fabric
RMS QA Specification R11 Stormwater Drainage
RMS QA Specification R23 Plastic Flexible Pipes
RMS QA Specification R33 Trench Drains
RMS QA Specification R63 Geotextiles (Separation and Filtration)
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4. Terms and definitions The following terms and definitions apply in this document:
AEO Authorised Engineering Organisation
AEP annual exceedance probability; the probability of an event being equalled or exceeded
within a year expressed as a percentage (for example, 2% AEP)
ARI average recurrence interval; the average time period between occurrences equalling or
exceeding a given value expressed as a number of years (for example, 50 year ARI)
ARR Australian Rainfall and Runoff guide document by Geoscience Australia
ASA Asset Standards Authority
catch drain (also known as top drain or cut-off drain) intercepts overland flow or run-off before it
reaches the track and related structures such as cuttings or embankments
cess area from the edge of the ballast profile to either the edge of the embankment or the toe of the cutting
cess drain drain located at formation level at the side of the track
culvert arch, box, oval or circular shaped structure with integral walls, roof and floor
Darcy-Weisbach equation an equation that relates head loss due to friction along a given length of pipe to the average velocity of the fluid flow
FRP fibre reinforced polymer (or plastic), also called fibre reinforced composite (FRC)
main line track main running lines, crossing loops, refuge loops and sidings with a maximum
permissible speed greater than 25 km/h
mitre drain connected to cess and catch drains to remove water or to provide an escape for
water from these drains
peak flow rate the highest flow discharged from the catchment under consideration having
evaluated the most critical storm duration with a particular average recurrence interval
pipe embedment zone the pipe support materials including the bed zone, haunch zone, side
zone and overlay zone
possession closure of one or more lines to allow work to be carried out in the Danger Zone
using a Local Possession Authority (LPA) or a Track Occupancy Authority (TOA)
railway corridor the extent of land over which a railway line passes (typically fenced along
boundaries) that is owned, leased, or otherwise utilised by the rail operator/state
Rational method a formula expression of peak discharge as proportional to the product of
rainfall intensity, catchment area and a runoff coefficient dependent on the catchment basin
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RIM rail infrastructure manager; in relation to rail infrastructure of a railway, means the person
who has effective control and management of the rail infrastructure, whether or not the person-
(a) owns the rail infrastructure; or
(b) has a statutory or contractual right to use the rail infrastructure or to control, or provide,
access to it
(RIM approval or acceptance within this standard refers to written agreement by the Civil design
technical manager or equivalent position of the RIM's organisation)
SFAIRP so far as is reasonably practicable
siding track all operating lines which are not main lines
TfNSW Transport for NSW
TMP technical maintenance plan
track drainage drainage of the track formation including diversion of water away from cuttings
and embankments
ULX underline crossing; the passage of services, such as pipes and cables, crossing below a
railway line
6-foot area between two tracks
5. Risk and safety Safe design is mandated in the Work Health and Safety Act 2011 and shall be incorporated into
the design of track drainage. Guidance on the safe design of structures is in the NSW
Government Safe Design of Structures Code of Practice (available from SafeWork NSW).
The Authorised Engineering Organisation (AEO) shall establish and implement a design
process system that manages safety across the full life cycle of the structure. The design
process system shall be developed in accordance with T MU MD 20001 ST System Safety
Standard for New or Altered Assets.
The design of track drainage shall take into account the safety and human factors
considerations for installation, construction, operational, maintenance and decommissioning
workers. Particular safety considerations for track drainage may include the following:
• access to inlets and outlets
• handrails and barriers
• trenching dimensions and benching
• pit sizing and grating weights
• confined spaces
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• working during rainfall events
• working in the rail corridor and safe places
5.1. Risk assessment Where required, risk assessments shall be site-specific and shall assess risk against the risk
criteria defined in T MU MD 20002 ST Risk Criteria for Use by Organisations Providing
Engineering Services.
Particular track drainage risk aspects that should be considered include, but are not limited to,
the following:
• existing, proposed and standard average recurrence interval storm effects
• historical flooding, blockages, scouring and formation failure
• type of structure, durability and potential for degradation
• site conditions, including formations, cuttings and embankments
• potential for ground settlements
• presence of hazards at the site, for example, structures, track turnouts, level crossings and
waterways
• track speed and type of rolling stock
• ongoing maintenance
• other noncompliances
The risk assessment shall be used to establish the extent of mitigation required, including over
and above standard requirements.
Risk assessments shall be submitted for acceptance by the rail infrastructure manager (RIM).
6. Environment The design of track drainage shall involve assessing and managing environmental impacts for
the whole of the asset life.
The design should also optimise sustainability opportunities over the life cycle of the asset, such
as the following:
• durability of materials to last for the expected design life (including any impacts from
aggressive soils and water tables)
• components (including any chemicals for operations and maintenance use) should not
contain any substance of high toxicity if a substance of lower toxicity is available that could
be just as effective
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• use of recycled and recyclable materials if they meet operational requirements
• visual impact and amenity
• resilience to climate change
• integrate green infrastructure without accelerating deterioration or preventing examinations
• use of only low maintenance species with non-invasive root systems adjacent to rail
infrastructure
• ability and ease to maintain and retro-fit improvements over time
• disposal and re-use at life cycle end
7. Heritage Transport agencies are responsible for maintaining and appropriately managing heritage items
under their stewardship and control. The Heritage Act 1977 is designed to protect, maintain and
manage environmental heritage in NSW, including items of archaeological significance.
Where changes are proposed to items with heritage significance, the following applies:
• for items listed on the NSW Office of Environment and Heritage (OEH) State Heritage
Register, the provisions of the Heritage Act shall be met
• for items listed on a state agency Section 170 Heritage and Conservation Register, the
principles and relevant guidelines contained within the OEH State Agency Heritage Guide
– Management of Heritage Assets by NSW Government Agencies shall be followed
Whilst rail heritage listings typically comprise a station group or precinct, a number of structures
are separately listed as individual items.
In station precincts, drainage structures may be included in the heritage curtilage, so the
maintenance of these related elements should be considered sympathetically.
Heritage significance should be considered at a sufficiently early stage of a project to be
satisfactorily addressed in concept designs.
Where drainage structures need to be modified, anticipated maintenance requirements for
maintaining and conserving the heritage fabric shall be taken into account at all design stages.
Alternative approaches to conservation, including appropriate means of protecting significant
fabric from damage and vandalism, may be required for drainage structures (and remnant
sections) that are no longer being used.
All approvals required from the Office of Environment and Heritage shall be obtained prior to
commencement of detailed design. The RIM shall be informed and professional heritage advice
obtained, and notification shall be made in accordance with the legislation.
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8. Approved materials Approved construction material for track drainage components shall be in accordance with
Table 1 and the other requirements in this standard.
Table 1 – Approved materials
Component Material Standard section number
Surface drain lining See Table 2 10
Subsurface pipes See Table 3 11.2.4
Box culverts Reinforced concrete (refer to T HR CI 12020 ST Underbridges)
N/A
Headwalls (inlets and outlets)
Reinforced concrete 11.6
Precast pits Wet cast reinforced concrete 11.7
Cast in situ pits Reinforced concrete 11.7
Grates Galvanised steel and fibre reinforced polymer (FRP) 11.7.4
Ballast cages Galvanised steel 11.7.5
Aggregate drain subsoil pipe
Corrugated perforated and non-perforated plastic 11.8
Aggregate drain subsoil pipe lining
Seamless tubular filter fabric 11.8
Flushing points Concrete and cast iron 11.9
Subsurface drain trench lining
Geotextile 11.10
For components not listed in Table 1, approved construction materials for main structural
elements are steel and concrete in accordance with AS 4100 Steel structures and AS 3600
Concrete structures respectively or AS 5100 Bridge design.
For track drainage structures with proposed concrete and steel material grades and strengths
outside the scope of the Australian standards noted, the designer shall nominate the
appropriate standard for the material and this shall be subject to approval by the Lead Civil
Engineer, ASA.
Timber and masonry materials shall not be used as structural elements in the design of new
track drainage structures. In special circumstances, such as for heritage reasons, the use of
masonry is approved for existing structures and as facing material for new structures.
Approved proprietary products such as plastics, FRP and polymer concrete, where specified,
shall also be designed and installed in accordance with the manufacturer's specifications.
For prohibited configurations, see Section 9.9.
For grated channels, also see Section 10.1.
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8.1. New and infrequently used materials Any products specified in the design documentation that can be reasonably deemed to be new
or infrequently used shall be identified by the AEO and referred to the Lead Civil Engineer, ASA
for approval.
The AEO designer shall ensure that the manufacturer, constructor and maintainer understand
any particular requirements or practices relating to such products prior to release of the design
documentation, which shall include documentation of these requirements.
Durability requirements shall be in accordance with Section 9.6.
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9. General design requirements Typical details, sections and notes for track drainage are shown in CV 0205421 Track Drainage
- Typical Sections and Notes. Where the designer proposes to adopt a standard design or detail
for a specific location, the designer shall assess the currency and suitability of the standard
design for use, and where necessary, shall specify modified or alternative designs. Modified or
alternative designs shall comply with the relevant TfNSW and Australian standards.
This standard shall be read in conjunction with T HR CI 12130 MA Track Drainage, which is a
manual that provides guidance for the design process, installation and maintenance aspects for
effective track drainage together with diagrams.
Track drainage shall be designed and arranged to collect and convey water flows calculated in
accordance with this standard. No other drainage shall be discharged into the track drainage
system without the approval of the Lead Civil Engineer, ASA.
All associated stormwater run-off from within and outside the rail corridor shall be accounted for
and integrated where applicable in the track drainage design.
Where the existing track alignment or earthworks profiles differ from the design alignment and
T HR CI 12110 ST Earthworks and Formation, the maximum stormwater flow rate case shall be
accounted for in the drainage design analysis and the design solution shall also cater for the
track and earthworks profiles at the design standard alignments (unless otherwise advised by
the RIM).
Underbridge deck drainage systems and waterways crossing the rail corridor shall be in
accordance with T HR CI 12020 ST and shall integrate with the track drainage system.
Level crossings shall be in accordance with ESC 520 Level Crossings and shall integrate with
the track drainage system.
Track monitoring requirements are specified in SPC 207 Track Monitoring Requirements for
Undertrack Excavation. Transit space requirements are specified in ESC 215 Transit Space.
Construction aspects are in Section 12 and Section 13.
Where a conflict exists between standards and specifications, the requirements of this standard
shall take precedence, then CV 0205421, then Roads and Maritime Services (RMS)
specifications and then Australian standards.
9.1. Stormwater discharge Stormwater run-off from bridges and structures over track shall not be discharged into the track
drainage system. Stormwater run-off from station buildings and station platform hard surfaces
may be discharged directly into track drainage pits, provided the following are satisfied:
• run-off is piped from a platform pit into a track drainage pit
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• debris and sediment is filtered and captured by trash racks and grating devices that are
managed and maintained within the station platform
• the track drainage system has adequate capacity for the additional flow
• additional relatively clean water can be used to flush downstream drainage networks
• the system is approved by the RIM
All track drainage systems shall be designed to discharge to an approved watercourse or
existing drainage system, and the approval of the appropriate authority shall be obtained in
advance of discharge.
Detention basins and other hydraulic structures may be required to control stormwater
discharge to satisfy local authority approvals. These structures, where required, shall be
designed in accordance with this standard and AS 3600 and AS 4100 or AS 5100 when within
the railway corridor.
External development requirements are in T HR CI 12080 ST External Developments.
9.2. Restrictions and constraints The design of track drainage shall take into account potential restrictions and constraints
including, but not limited to, the following:
• live operating conditions
• existing drainage system capacity and invert levels
• track possessions
• site-specific geotechnical conditions
• staged construction
• temporary works
• installation methods (for example trenching, jacking, drilling or boring pipes)
• trial assembly prior to track possession
• cutting and embankment stability
• ballast and formation profiles (standard and non-standard)
• track geometry
• stability of excavations and nearby structures
• stability of other structures (for example, retaining walls, platforms, overhead wiring
structures (OHWSs), buildings, and so on)
• service routes
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• access points for construction and maintenance
• other rail infrastructure (including existing drainage systems and other rail structures)
• non-rail infrastructure (including services)
• railway corridor boundaries
• future modifications to the rail corridor
• outlet waterway requirements
• malfunctioning drainage systems (particularly at critical locations)
Potential conflicts with existing services shall be taken into account and allowed for in the
design. Service searches shall be conducted and the locations of these services shall be
indicated on the design documentation. Service searches shall be supplemented by trial pits to
ensure the accuracy of the service search information and determine the depths of the services.
9.3. Drainage system type The type of drainage system selected for each location is dependent on the site restrictions,
constraints, water source, track structure and maintenance requirements.
The two types of drainage systems considered in this standard are surface and subsurface.
Surface drains (also referred to as open drains) shall be used in preference to subsurface drains
wherever possible, as surface drains are more easily inspected and maintained. Most systems
will only have to cater for surface run-off.
The order of preference for drainage types shall be as follows:
a. surface drains (cess drains, catch drains, mitre drains)
b. subsurface piped drains (slotted and non-slotted)
c. subsurface aggregate drains with subsoil pipes (perforated and unperforated)
d. subsurface aggregate drains
Combinations of these noted drainage system types may be used. Crowning of formation
capping surface should also be considered to minimise subsurface drains.
Subsurface drains shall be used where adequate surface drainage cannot be provided, either
due to some restriction or lack of available fall due to outlet restrictions. Locations where these
circumstances may occur includes, but is not limited to, the following:
• trackside structures
• cuttings
• track junctions
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• multiple tracks
• underbridges
• access roads
• high water table areas
Subsurface aggregate filled trench drains (without pipes) shall only be used where adequate
subsurface piped or subsoil pipe systems cannot be provided.
9.4. Trackside structures For trackside structures such as platforms walls, tunnel walls, retaining walls, bridge supports,
buildings, overhead wiring structures and signal equipment, surface run-off water shall be
intercepted and diverted away from the structure footing and foundation.
Where a cess drain next to a structure is unavoidable, the following should be considered in the
design:
• a surface fall away from the structure with a horizontal clearance of at least 1000 mm to the
cess drain
• a lined cess drain or an integrated slotted drain to transfer water away from the structure
• maximising clearance to track centreline
• structure undermining and destabilising
• seepage water and weepholes from retaining structures
At platforms, sloping the formation cross fall away from the platform wall should be considered
in preference to providing drains next to the platform wall. Where two tracks are between
platforms, provision of a 6-foot centre drain system is the preferred arrangement.
9.5. Multiple tracks For two or more tracks, track drainage requirements shall be as follows:
• surface run-off water from one track shall not traverse another track to drain away
• where two tracks are present without a formation crown in the 6-foot, at least a centre
surface drain shall be provided
• where three or more tracks are present, at least one surface drain shall be provided in the
centre of one of the 6-foot areas
• for main line tracks, the 6-foot centre surface drains, where provided, shall include
subsurface carrier pipes with pits
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• surface drains should include an integrated subsurface slotted pipe system where
recommended by geotechnical engineering advice
Unnecessary excavation or trenching that disturbs the capping layer should be avoided.
At turnouts and special track work, the turnout track and the nearest through track may be
considered as a single track to satisfy the surface run-off water traverse requirement, where
formation cross falls or crowns cannot be provided due to site constraints. Formation cross falls
and surface drainage paths shall be directed to minimise drainage pits and minimise surface
water run-off from one track traversing another track to drain away where possible.
The installation of additional tracks on the outside of existing tracks shall not compromise the
integrity and effectiveness of the drainage for the existing tracks. Where necessary, the
drainage system for the existing tracks shall be redesigned and configured to comply with the
requirements of this standard.
9.6. Drainage design life The design life and durability of track drainage elements, including pits and non-track drainage
pipe culverts that cross the rail corridor are specified in T HR CI 12002 ST Durability
Requirements for Civil Infrastructure.
The referenced design life is typically 120 years and includes particular requirements for spun or
rolled concrete members and the type of environment (such as whether the water is abrasive,
acidic or alkaline).
The minimum design life of non-buried track drainage elements such as grates and covers that
are replaceable shall be 50 years.
The manufacturer's specifications shall be referred to in relation to the various environmental
conditions and circumstances for which the concrete or pipe is deemed to be suitable.
9.7. Design average recurrence interval The average recurrence interval (ARI) for track drainage storm and flood design for main line
track shall be 50 years (2% annual exceedance probability (AEP)).
Siding track, including stabling facility open track drainage design shall have a minimum design
ARI of 25 years (4% AEP).
The design ARI for non-track drainage crossings shall be in accordance with T HR CI 12020 ST
and T HR CI 12110 ST.
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9.8. Peak flow rate Estimation of the volume of surface water that is required to be drained shall be determined
using the 'Rational' method as detailed in Australian Rainfall and Runoff (ARR), adopting the
design average recurrence interval in Section 9.7.
The estimated run-off for a complying ballasted track formation capping layer should be based
on a 10 year ARI coefficient value (C10) for surface clay having a value of 0.9 at the upper
bound rainfall intensity. Other surface type run-off coefficient values should be selected as
described in ARR.
A range of storm events representing varying rainfall durations in ARR shall be investigated.
The drainage design shall be carried out adopting the critical rainfall event and the peak flow
rate for each catchment area.
The catchment areas required for peak flow rate calculations shall be determined using (in order
of preference) site survey, site measurements, or suitably scaled topographic maps.
Water flowing into the rail corridor from adjoining properties and streets, including any detention
systems, shall be taken into account.
Where the design inflow rate from other external drainage systems cannot be accurately
determined, the design flow rates shall not be less than the outlet capacity of that system.
9.9. Prohibited configurations Prohibited configurations for track drainage are as follows:
• plastic subsurface pipes (all types) such as glass filament reinforced (GRP), polyvinyl
chloride (PVC), polypropylene (PP) and high-density polyethylene (HDPE), unless
specifically type approved by the ASA
• inverted syphon systems
• downstream culvert opening size and cross-section area less than the upstream culvert
opening (to minimise blockages)
• pumped systems (unless in an approved non-free draining tunnel)
• track drainage structures used as service routes or that contain service apparatus or
equipment
• proprietary drainage cell systems used without the prior approval of the Lead Civil
Engineer, ASA
These requirements apply to both modifications to existing and proposed track drainage
structures.
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10. Surface drainage Requirements for surface drains such as cess drains, catch drains and mitre drains, are as
follows:
• flow capacity shall be greater than the design peak flow rate without overtopping the
channel
• desirable minimum gradient along the drain is 1% (1 in 100 slope)
• minimum allowable gradient along the drain shall be 0.5% (1 in 200 slope)
The material forming the open channel shall be capable of sustaining the maximum permissible
design velocity without scour or erosion. Table 2 provides maximum velocity values for varying
lining types.
Table 2 – Maximum permissible velocities
Channel lining type Velocity (m/s)
Fine sand 0.45
Silt loam 0.60
Fine gravel 0.75
Stiff clay 0.90
Coarse gravel 1.20
Shale, hardpan 1.50
Grass covered 1.8
Stones 2.5
Asphalt 3.0
Boulders 5.0
Concrete 6.0
Where cast in situ concrete lining is specified for surface drains, the minimum thickness shall be
100 mm. Where fibre reinforced concrete lining is specified for surface drains, then non-metallic
fibres shall be used.
The design of surface drainage systems shall take into account the following requirements:
• scouring and erosion (refer to Table 2)
• a minimum 10% blockage of open drain cross-section area (minimum 30% blockage where
ballast can potentially fall into the drain)
• possible obstructions from trackside structures
• the interface with the formation and capping of adjacent tracks
• formation cross fall changes (particularly at platforms, turnouts and multiple tracks)
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• avoiding potential water ponding on the surface within the rail corridor
• manufacturers specifications
• maintenance requirements including safety aspects such as handrails and barriers (also
refer to AS 1657 Fixed platforms, walkways, stairways and ladders - Design, construction
and installation)
Site investigations, such as potholing of the ballast, shall be undertaken to confirm formation
levels and cross falls particularly at strategic locations of existing tracks.
10.1. Cess drains For ease of maintenance, over-sized open channels should be adopted for cess drains to allow
a certain degree of sediment build-up to occur and still work effectively. The minimum
dimensions in millimetres of an open channel as illustrated in Figure 1 shall be A= 200, B= 200,
C= 300.
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Figure 1 – Minimum channel sizes (not to scale)
Where locating cess drains, formation design shoulder distances and typical track cross-
sections are specified in T HR CI 12110 ST.
Where track drainage is incorporated within existing track constraints (for example, cuttings,
between tracks) and the design shoulder distance cannot be achieved, open channels shall be
at an adequate distance from the track to prevent ballast spill into the channel area. In this case,
the edge of the channel closest to the track shall be a minimum of 2800 mm from the design
track centre. This minimum edge distance shall be increased as required based on track
configuration (rail size, sleeper type, ballast depth) and track curvature.
Requirements for grates and covers, where used, are in Section 11.7.4.
Proprietary polymer concrete grated channel surface drainage systems and FRP systems,
located at or within the track formation design shoulder and cess standard distances or within
the rail live load surcharge zone, require the approval from the Lead Civil Engineer, ASA.
The top of lined and unlined channels shall be no higher than the top of the adjacent track
formation surface level.
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10.2. Catch drains Catch drains shall be provided to the uphill side of a cutting to intercept and divert water from
flowing down the cutting face and shall have 1000 mm minimum horizontal clearance to the top
edge of the cutting. Benched cuttings may also require additional catch drains.
Catch drains shall be provided to the uphill side of embankment batters to intercept and divert
water from flowing along the embankment toe and shall have 1000 mm minimum horizontal
clearance to the embankment toe.
Catch drains shall be either lined or unlined depending on the local soil conditions and design
peak flow rates. Half round pipes may be used instead of concrete lined channels.
10.3. Mitre drains Where mitre drains are required, they shall be provided at regular centres with 100 m maximum
spacing. They shall be installed at the ends of cuttings.
The ends of mitre drains shall be splayed to disperse water quickly and reduce scouring.
11. Subsurface drainage Subsurface drains shall be provided along the cess, and between, across, or under tracks
where required for the following:
• where adequate surface drainage cannot be provided, either due to a restriction or lack of
available fall or gradient due to outlet restrictions
• multiple tracks
• where the water table is at or near earthworks level
• diverting of ground water and seepage
• relieving water pressure where artesian conditions exist
Subsurface drainage lines should have a straight horizontal alignment.
Subsurface drainage systems shall be designed to transfer surface run-off, ground water and
seepage, and water collected from other drainage systems to which the new system is being
connected.
If a drainage system is required to remove ground water and seepage, then a detailed
hydrogeology and geotechnical investigation is required to determine the volume of water for
the sizing of drains.
At locations where subsurface drainage is critical for geotechnical stability, installation of
instrumentation such as piezometers shall be considered to supplement functionality of the
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drainage system. Further details are in T HR CI 12101 ST Geotechnical Problem Management
and T MU CI 12140 GU Geotechnical Instrumentation and Monitoring Guidelines.
Where connecting to existing drainage systems, a detailed site survey shall be undertaken and
the flow capacity, sizes, levels and integrity shall be investigated to confirm system suitability
prior to design of the additional drainage.
11.1. Design traffic loads Drainage systems shall be designed for effects of traffic loads from rail, road, and construction
vehicles.
11.1.1. Rail traffic
Where railway live loads are applicable, pipes, headwalls and pits shall be designed for the rail
traffic load specified in T HR CI 12020 ST.
Railway load dynamic effects (impact factor) for complying concrete pipes shall be adopted in
accordance with AS/NZS 3725 Design for installation of buried concrete pipes, which varies
linearly from 1.4 (α=0.4) at 0.3 m depth to 1.0 (α=0.0) at 3.5 m depth or greater (where the
depth is measured from the top of rail).
Railway load and dynamic effects for other complying pipe materials and components shall be
in accordance with AS 5100.
11.1.2. Road and construction traffic
Pipes, headwalls and pits located within the rail corridor, including under vehicle access roads,
shall be designed for at least the T44 road traffic design load specified in T HR CI 12030 ST
Overbridges and Footbridges.
The requirements for heavy construction plant and equipment such as cranes shall be
nominated by the RIM and included, where applicable, in the design.
11.2. Pipes The capacity of the proposed drainage system shall be determined using the peak flow rate
calculated by the Rational method, with adjustment made for subsurface water, water collected
from other systems and potential blockages of at least 10%. The peak flow velocity within the
pipe shall be less than the manufacturer's recommended maximum limits. Drainage pits along
the pipe network shall not overflow at the peak flow rate.
The minimum requirements for pipes also apply to box culverts, where used for track drainage.
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11.2.1. Pipe size
Pipes larger than the design size may be adopted to reduce the likelihood of the system
becoming blocked and also enable easier cleaning. The minimum pipe diameter shall be
225 mm (for ease of maintenance).
Where culverts are extended, also see Section 9.9 for culvert sizing.
11.2.2. Pipe gradient Requirements for track drainage pipe gradients are as follows:
• desirable minimum gradient along the pipe is 1% (1 in 100 slope)
• where this desirable minimum gradient cannot be achieved due to site constraints, pipe
gradients may be laid flatter to 0.5% (1 in 200 slope)
• pipe gradients flatter than 0.5% (1 in 200 slope) shall require the approval of the Lead Civil
Engineer, ASA
Other drainage pipe culverts that cross the rail corridor such as regional or council stormwater
drains shall have a minimum allowable gradient along the drain of 1% (1 in 100 slope). Where
these other (non-track drainage) pipe gradients are required to be flatter, approval of the Lead
Civil Engineer, ASA shall be obtained.
Steep pipelines shall be protected against bedding wash out and restrained against sliding
where applicable.
11.2.3. Pipe depth The depth of pipes shall be as follows:
• 1600 mm minimum measured from top of rail to top of pipe or pipe encasing, for pipes
under the track or within the rail live load surcharge zone
• 600 mm minimum measured from the design cess invert level to top of pipe, for pipes
running parallel to the track
For track drainage locations only, where it is not possible to comply with these pipe depth
requirements stated in the previous paragraph due to site constraints and achieve an effective
drainage system design, the pipe depth may be reduced to the following:
• 1200 mm minimum measured from top of rail to top of pipe or pipe encasing, for pipes
under the track or within the rail live load surcharge zone
• 300 mm minimum measured from the design cess level or 1000 mm measured from top of
adjacent rail (whichever produces the lowest invert level) to top of pipe, for pipes running
parallel to the track
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11.2.4. Acceptable pipes
Pipes shall be supplied and installed in accordance with the requirements specified in Table 3.
Table 3 – Acceptable pipe requirements
Material Manufacture (standard)
Pipe type Minimum strength Class (1)
Installation (design standard)
Installation (specification) (3)
Reinforced concrete
AS/NZS 4058 non-slotted 4/6 (2) CV 0205421/ AS/NZS 3725
RMS QA R11 Stormwater Drainage
Fibre reinforced concrete
AS 4139 Slotted and non-slotted
4 (2) CV 0205421/ AS/NZS 3725
RMS QA R11
Type approved plastic(4)
Type approval conditions
Slotted (perforated) and non-slotted
Type approval conditions (2)
CV 0205421/ AS/NZS 2566
RMS QA R23 Plastic Flexible Pipes
Steel (5) - - - - -
Notes:
(1) The required strength of buried concrete pipes to be determined in accordance
with AS/NZS 3725.
(2) Refer to Section 11.5 and Section 11.11. For ULXs installed during a possession
or within 10 m of turnouts, minimum pipe strength is Class 6. Due to risk of poor
embedment, only rigid reinforced concrete non-slotted pipes are permitted for these
ULX installations.
(3) Refer to SPC 301 Structures Construction for application of RMS specifications.
Installation specifications include allowable pipe joint types. Manufacturer's
specification limitations also apply. Also refer to T HR CI 12130 MA for guidance.
(4) Type approved plastic products are listed at the Transport for NSW website at
www.transport.nsw.gov.au.
(5) For steel pipe electrolysis, stray currents, potential corrosion and infrastructure
protection, the following apply:
• AS 4799 Installation of underground utility services and pipelines within railway
boundaries
• T HR CI 12002 ST
• T HR EL 12002 GU Electrolysis from Stray DC Current
• other specific requirements stated by the Lead Electrical Engineer, ASA
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11.2.5. Slotted and perforated pipe types
Where slotted and perforated subsurface pipes are used, the following shall also apply:
• strength reductions for the slots shall be included in the design and shall be based on
manufacturer’s recommendations
• in areas of high water table and flat ground, slotted pipes should be used instead of
non-slotted pipes as they can also collect water between pits
• slots in slotted pipes shall be orientated to allow water flow along the pipe invert centrally
between the slots
• for pervious (sandy soil) installations, the bed zone material shall be impervious and
profiled within the trench to direct seepage water towards the pipe base
• embedment zone shall be aggregate materials in accordance with Section 11.8 and placed
in accordance with Section 11.4
• trench lining of aggregate materials shall be a geotextile filter fabric in accordance with
Section 11.10
• slotted pipes and perforated pipes shall not be used for under track pipe work or other
drainage pipe culverts that cross the rail corridor such as regional or council stormwater
drains
11.3. Repairs to existing pipe culverts Existing pipe culverts may require repair due to structural or hydraulic integrity loss at some
stage in their asset life cycle.
For the purpose of this standard, refurbishment means like-for-like replacement, rehabilitation or
repair of structural components to provide the equivalent load capacity, functionality and
performance as the original component.
For substandard existing pipe culverts, a risk assessment in accordance with Section 5.1 and a
cost-benefit analysis, which considers upgrade requirements, shall determine feasibility of the
repair and be submitted to the RIM for approval.
Guidance for general repair methods and procedures are documented in TMC 302 Structures
Repair.
The designer shall document appropriate repair methods and materials. Refer to Section 8 for
further requirements about approved materials.
The design life for the refurbishment or repair works shall neither be less than the expected
remaining life of the existing pipe culvert nor less than 25 years, and approved by the RIM.
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The designer shall develop a technical maintenance plan (TMP) for the repaired pipe culvert
and lining.
Where the pipe repair or lining involves a system that is untested on the TfNSW Metropolitan
Heavy Rail Network, a more frequent cycle of examinations for the initial period immediately
after installation shall be undertaken to confirm satisfactory performance (say at one week, one
month and then six months after installation, and at significant rainfall events).
11.3.1. Pipe lining systems Deteriorated piped culvert drainage lines may be repaired by lining with proprietary lining
systems. In this case, the following conditions shall apply:
• the maximum internal dimension of the existing pipe culvert shall not exceed 1200 mm
• the lining material shall comply with a recognised and proven local or international standard
(Section 8 applies to the other structural materials)
• the design methodology for the lining system shall comply with a proven and recognised
local or international standard
• where the hydraulic performance of the repaired and lined pipe culvert cannot practically
achieve the design ARI peak flows, a reduced design ARI is acceptable, provided there are
no adverse effects from the works such as upstream flooding, scouring or operational
impacts compared to the existing pipe culvert drainage effects
• where an existing pipe culvert does not satisfy the design ARI peak flows and is associated
with adverse hydraulic effects, pipe lining shall not be a repair option
• where the repaired pipe and lining, in combination, cannot practically achieve the design
live loads defined in Section 11.1, mainline freight (MF) plus dynamic load allowance (DLA)
loading defined in T HR CI 12008 ST Capacity Assessment of Underbridges may be
adopted for pipes not carrying heavy coal freight (HC) rail traffic
• the design of the repair by pipe lining (including the lining design itself) shall be undertaken
by an appropriate AEO
• the lining system shall have a proven minimum design life of 25 years
• the selection of the repair option shall be based on a consideration of life cycle costs
including comparison of conventional repair options and pipe lining options
11.4. Trenching and backfill Trench dimension requirements are as follows:
• minimum trench width shall be the pipe external diameter plus 150 mm on each side
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• for longitudinal drains located either within 2500 mm of the track centre line or between
tracks where track centres are less than 6000 mm, the minimum trench width shall be the
pipe external diameter plus 100 mm on each side
• for pipes running in parallel, a horizontal clear space of 300 mm between pipes shall be
provided to allow compaction to take place
• the horizontal clear distance between separate ULX trenches shall be at least 3000 mm
Pipe embedment shall be in accordance with Section 11.5.
Trenches shall be backfilled, compacted and tested above the pipe embedment zone with
suitable soil material, including structural zone material and capping, in accordance with
T HR CI 12110 ST and T HR CI 12111 SP Earthwork Materials.
Soil compaction shall be homogenous throughout the lift and loose fill layer thickness shall be
150 mm maximum when using hand-held compacting equipment.
Where trenching has disturbed the capping layer for non-slotted pipes, the capping layer shall
be reinstated to a minimum depth of 300 mm from formation surface level.
All ULX open cut trenched excavations and pipes, including underbores, shall cross at an angle
of 90° ± 5° to the track, and shall have a straight alignment between adjacent pits.
Longitudinal open cut trenched excavations or pipes shall not be located under sleepers or
bearers.
Water should not be allowed to pond in open trenches within the rail corridor. During rain or
when rain is forecast, or if there is active seepage or surface flow into the open trench, then the
trench should be backfilled on the same day as the excavation.
Non-trenched track drainage ULX excavations, such as underbores, shall also satisfy below
ground service requirements in accordance with T HR CI 12190 ST Service Installations within
the Rail Corridor.
Trenching, backfill and pipe embedment installation requirements, including soil type, soil
compaction and testing, shall be clearly indicated on design drawings.
11.5. Pipe embedment Pipe embedment and support shall be in accordance with the installation (design standard)
shown in Table 3. An appropriate embedment type such as 'HS' support for concrete pipes (or
an equivalent support for other pipe types) comprising compacted bed, haunch, side and
overlay zones in accordance with AS/NZS 3725 shall be selected to suit the loading and
construction time constraints.
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For determining the class of pipe to be specified in a subsurface drainage system, the
embedment and support type assumed shall be appropriate for what can be achieved during
construction.
Most under track drainage is constructed during track possessions where the more stringent
requirements for placement and compaction of embedment material cannot always be satisfied.
For ULXs planned to be constructed during a track possession period, as a provisional
measure, type 'U' support or uncontrolled compaction in accordance with AS/NZS 3725 shall be
used to determine the pipe strength class required in design for concrete pipes. Therefore, a
rigid reinforced concrete pipe with minimum strength Class 6 would be applicable for ULXs
constructed during a track possession. Type 'U' support shall not be constructed.
Controlled low strength materials (CLSMs) including cement stabilised sands normally require
additional time to achieve sufficient pipe support stiffness prior to backfill material placement
and subsequent live loadings. CLSM and stabilised soils shall not be used for pipes installed
during a track possession unless approved by the RIM.
11.6. Inlets and outlets To prevent soil erosion, all inlet and outlet points that are not fitted with a pit shall be provided
with an appropriate size concrete headwall to suit the ground profile. For standard concrete
headwalls, refer to the following:
• CV 0497068 Pipe Culverts Headwalls to Suit Pipes 225-600 mm Diameter
• CV 0497069 Pipe Culverts Headwalls to Suit Pipes 675-1800 mm Diameter
• CV 0517943 Single Pipe Headwall to Suit Pipes 225-600 mm Diameter
• CV 0517944 Single Pipe Headwall to Suit Pipes 675-600 mm Diameter
• CV 0517945 Twin Pipe Headwall (Splayed Wings) to Suit Pipes 225-600 mm Diameter
• CV 0517946 Twin Pipe Headwall (Splayed Wings) to Suit Pipes 675-1800 mm Diameter
• CV 0517947 Twin Pipe Headwall (Straight Wings) to Suit Pipes 225-600 mm Diameter
• CV 0517948 Twin Pipe Headwall (Straight Wings) to Suit Pipes 675-1800 mm Diameter.
Where standard designs or details are used, also refer to Section 9.
Concrete for inlets and outlets shall have a minimum characteristic compressive strength of
32 MPa and shall comply with AS 3600 (or AS 5100 when subject to rail traffic loads).
Where the face of the headwall is closer than 2150 mm to the track centreline or where railway
surcharge applies, the headwalls shall also be designed to provide strength and stability to
resist the applied loadings, and transit space requirements.
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The ground covering at the pipe inlet and outlet points shall be capable of withstanding the peak
flow rates. Scour protection or energy dissipating devices may be required if existing ground
cover cannot withstand the design rate. The maximum permissible velocities provided in Table 2
shall be used to determine the appropriate ground covering lining type.
Ballast and soils should be prevented from entering the inlet. For reference, details are shown in
drawing CV 0115011 Ballast retaining wall and drawing CV 0277517 'L' Retaining Wall Type 1.
Where the sediment load of the water being discharged from a drainage system is high, a silt
trap should be included. Typically, an established rail corridor that complies with standard
requirements would have a low sediment load.
11.7. Pits Pits shall be provided as access points for surface water and for maintenance of the drainage
system. General requirements for pits are as follows:
• concrete for pits shall have a minimum characteristic compressive strength of 50 MPa and
shall comply with AS 3600 (or AS 5100 when subject to rail traffic loads)
• design traffic loads shall be as specified in Section 11.1
• precast pits with risers used to accommodate varying depths shall be adopted in
preference to cast in situ pits
• only wet cast concrete pits shall be permitted (not dry cast)
• precast pits units with thinned wall sections (such as for unused pipe connections) shall not
be permitted where rail or road surcharge loads are applicable
• any gaps between the pit wall and pipes shall be grouted and sealed
• penetrations in pit walls for drainage pipes shall be above the base slab top surface level
• the pit entry surface level shall be no higher than the adjacent ground finished surface level
or adjacent cess drain invert level where applicable
• at a surface drain low (or gully) point, where ballast cages are not applicable, at least one
pit should include side entry opening slots with 100 mm to 125 mm clearance height to
provide an alternative inlet flow path to mitigate surface grating blockages at these pits
• permanent access to the pit and inside the pit shall comply with AS 1657
A pit table and all the specific details for pits shall be included in the design drawings.
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11.7.1. Spacing and set-out
Pit spacing and set-out requirements are as follows:
• pits shall be spaced at 30 m to 50 m centres, except through platforms where spacing shall
be 20 m to 30 m centres
• pits shall be located at the transition between pipe sizes and at changes in direction and
abrupt changes in grade
• clearance between the pit and adjacent sleepers or bearers should not be less than
150 mm
• configuration issues arising from placing straight pipes alongside curved tracks shall be
taken into account (for example, this situation may require reduced pit centres)
• pits shall be set out to ensure the minimum amount of pipe cutting is required during
installation (that is, whole pipe lengths should be used between pits)
11.7.2. Dimensions Pit width shall be the maximum size available to enable proper placement of the pit and ballast
cage where applicable, without clashing with the sleepers or bearers.
The minimum internal plan dimensions of a pit shall be as follows:
• 450 mm x 450 mm for depths of 1 m or less where located outside the 6-foot
• 600 mm x 600 mm for depths greater than 1 m where located outside the 6-foot
• 900 mm x 900 mm for depths greater than 1 m where located outside the 6-foot and where
inspection access is required
• 600 mm wide (perpendicular to the tracks) x 900 mm (along the track), to accommodate
inspection access where located within the 6-foot
11.7.3. Internal access Where the internal pit height (including risers) exceeds 1200 mm, the following (in addition to
AS 1657 requirements) shall be provided:
• step rungs shall be provided at 300 mm vertical centres
• step rungs shall be located on the face of the oncoming train traffic (that is, either Sydney
face for the Down track or Country face for Up track) or the face of the shortest sighting
distance for pits located within the 6-foot so users can view oncoming rail traffic
• pit riser heights shall be selected such that step rungs do not come within 50 mm of the top
or bottom of the riser
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11.7.4. Grates
The grate and cover minimum load classification for all pits (unless noted elsewhere in this
section) shall be Class D (8000 kg nominal wheel loading) in accordance with AS 3996 Access
covers and grates. At locations where vehicular traffic load over the grate or cover is strictly
precluded, such as below station platforms and under ballast cages, the strength may be
reduced to Class B (2670 kg nominal wheel loading). All grating and cover materials shall
comply with Section 8.
For locations where access for off track equipment is limited, pit grates shall be designed for
easy manual removal and security. For example, these grates on a pit shall be manufactured in
two sections rather than one and shall be lockable.
11.7.5. Ballast cages A ballast cage (also referred to as a lobster pot) prevents ballast spilling into a pit and shall be
provided for all pits as follows:
• within 2800 mm of a ballasted track centre
• where pit location constraints result in the possibility of ballast covering a pit
Ballast cages, where required, shall comply with the following requirements:
• be of heavy duty construction capable of withstanding live traffic loading from road vehicles
(see Section 11.1.2) or from construction machinery
• be positioned to the outside edges of the pit
• not extend above the top of sleeper level
• be provided in accordance with CV 0400998 Ballast Cage (Lobster Pot) with Removable
Lid, or details modified as necessary to suit specific locations
• where the standard drawing cannot be used, the designer shall modify or develop a
suitable ballast cage drawing, subject to approval by the RIM
11.8. Aggregate drains Aggregate drains are only suitable for use where a small flow of ground water or seepage is
expected. They shall not be used for the collection of surface water, except where permitted in
T HR CI 12020 ST.
The design of permeable drains may be carried out using the Darcy-Weisbach equation.
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The permeability of clean gravel can range from 0.01 m/s to 1.0 m/s. The aggregates used in
aggregate drains are either 20 mm nominal size or 53 mm nominal size (ballast). The
permeability of these aggregates shall be taken as follows:
• 20 mm aggregate k = 0.15 m/s
• 53 mm aggregate k = 0.40 m/s
Aggregate drains shall have a pipe system flushing points in accordance with Section 11.9. The
aggregate drain subsoil pipe, where used, shall be as follows:
• be corrugated plastic of 65 mm or 100 mm diameter perforated or non-perforated type
complying with RMS Specification 3552 type 1 pipe
• have seamless tubular filter fabric complying with RMS Specification 3553
• pipe gradients in accordance with Section 11.2.2
• pipe depths in accordance with Section 11.2.3
Trenching and backfill shall be in accordance with Section 11.4 and CV 0205421.
Geotextile fabric, where used shall be in accordance with Section 11.10.
11.9. Flushing points Subsoil pipe systems within aggregate drains shall have flushing points. Flushing points shall be
provided generally at intervals of not more than 60 m and at abrupt changes of grade and
alignment. On long and straight subsoil pipe runs (for example, straight pipe lengths of 1 km or
more) flushing points can be installed at a maximum interval of 120 m.
Flushing points shall consist of ‘T’ or ‘L’ connections in the subsoil pipe, with pipe connections
extending to the surface for regular flushing with water to clear the subsurface drain of fouling
material.
Flushing entry points not at a pit shall have a cast iron cap set in a concrete surround so as to
be clearly visible for maintenance. Flushing exit points shall be set in a pit or concrete headwall
unit (for example, an outlet complying with RMS Specification R33 Trench Drains).
Flushing points shall be clearly indicated on design drawings and TMPs.
11.10. Geotextiles The main purpose of a geotextile used in subsurface drainage is to act as a permeable filter,
which helps prevent silting-up of the drain it is protecting. The selected geotextile shall achieve
the following characteristics:
• good permeability through the fabric material
• durability (including the ability to survive during construction)
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• good filtering qualities
• resistance to clogging by fine particles
• ability to stretch and conform to the shape of an open trench
An appropriate geotextile filter fabric shall be selected which satisfies both the filtration criteria
suited to the in situ soil and the site drainage conditions.
The selected geotextile shall exhibit the following mechanical properties as a minimum when
tested in accordance with AS 3706 Geotextiles – Methods of test:
• tear strength of 590 N
• burst strength of 4600 N
• grab strength of 1200 N
• G Rating of 3500
Geotextiles, where used in subsurface drainage trenches shall fully line the trench and surround
the aggregate material. Joints of geotextile fabric shall be minimised and where required should
have minimum end overlaps as follows:
• 200 mm, but not exceeding 300 mm at the top of the trench
• 1000 mm along the trench base and sides
• 300 mm along the pipe, where slotted subsurface pipes are wrapped
The wrapped trench aggregate shall be covered by a minimum of 100 mm thickness of topping
aggregate graded to the formation and cess drain surface profile.
The geotextile shall comply with RMS Specification R63 Geotextiles (Separation and Filtration).
11.11. Turnouts and special trackwork Special trackwork includes catch points, expansion switches, diamonds, slips and the like. Track
component terms and definitions are specified in ESC 200 Track System.
Subsurface track drainage pipes and excavations should not be located under, or within 10 m of
turnouts or special trackwork, as specified in SPC 207. For track drainage, this '10 m zone', as
shown in Appendix B, shall include the following area:
• under a supporting bearer, and within 10 m along the track from a supporting bearer of a
turnout or special trackwork
• transversely within the rail live load surcharge zone, taken as 2.5 m minimum from the
nearest associated track centreline
At some existing sites, it is not possible to comply with all track drainage clearance
requirements. Where pipeline locations within this nominal '10 m zone' are approved by the
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Lead Track Engineer, ASA, additional subsurface drainage requirements for that whole pipeline
segment between pits are as follows:
• trenched and underbored excavations should not be located in a 'critical zone' as defined in
Section 11.11.1
• a risk assessment in accordance with Section 5.1, which at least considers an alternative
pipeline location out