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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

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

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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.

© State of NSW through Transport for NSW 2019 Page 3 of 48



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




• integration with T HR CI 12002 ST Durability Requirements for Civil Infrastructure and the

associated technical note TN 042: 2017

• other minor revisions




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



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




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




• 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.




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




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




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)




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

characteristics © State of NSW through Transport for NSW 2019 Page 13 of 48



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




• 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




• 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.




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.




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.




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




• 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




• 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




• 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




• 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.




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.




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)




• 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.


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.



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




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.




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




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




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.




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




• 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.




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.




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.




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




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.




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)




• 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




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

t hr ci 12130 st track drainage - transport for nsw · as 3600 concrete structures . as 3706...

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