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MINE SUBSIDENCE BOARD

IN ASSOCIATION WITH

P U T T I N G S E R V I C E A N D T H E N E E D S O F P E O P L E F I R S T

ROADS AND TRAFFIC AUTHORITY

COAL OPERATIONS AUSTRALIA LIMITED

DEPARTMENT OF MINERAL RESOURCES

DEPARTMENT OF URBAN AFFAIRS AND PLANNINGNSW MINERALS COUNCIL

GUIDELINES

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SUBSIDENCE


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CO

NTENTS

Published November 1997

Published by the Mine Subsidence Board,117 Bull Street, Newcastle West, N.S.W. 2302

Copyright by the Mine Subsidence Board

Apart rom any air dealing or the purpose o private study, research, criticism or review,as permitted under the Copyright Act, no part may be reproduced by any process withoutthe written permission o the Publisher.

ISBN 0 646 34358 0

Production - Helen Duncan Communications and MediaDesign & Artwork - Curzon Creative ServicesPrinting - NCP Printing

FOREWORD ............................................................................4

POLICY STATEMENT ..............................................................5

EFFECTS OF COAL MINING ON ROADS ................................6

PROCEDURES .........................................................................7

GRANT OF MINING LEASES AND APPROVALSTO EXTRACT PILLARS/LONGWALLS .....................................7

ROAD ROUTE SELECTION ......................................................7

FLOW CHART FOR GRANT OF MINING LEASE .....................8

CO-ORDINATION OF MINING AND ROADBUILDING ACTIVITIES ............................................................9

CHOOSING BETWEEN ROAD MODIFICATIONSAND COAL STERILISATION ..................................................13

LEGISLATION ........................................................................15

COAL MINING AND ITS EFFECTS ........................................16

TECHNOLOGY OF MINING ...................................................16

UNDERGROUND MINING ....................................................16

SUBSIDENCE EFFECTS .........................................................19

OPEN CUT OPERATIONS ......................................................21

THE IMPACT OF COAL MINING ON ROADS ........................23

STRUCTURE TYPES AND FUNCTIONS ................................23

DESIGN MEASURES TO PROVIDE FOR SUBSIDENCE .........24

CASE STUDIES .....................................................................25


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SECTION3

PROCEDURES3.1

GRANT OF MINING LEASES ANDAPPROVALS TO EXTRACT PILLARS/LONGWALLS

3.1.1 Grant o Mining Leases

Leases to mine coal (mining leases), either or the establishmento new coal mines or or additions to existing coal mines, aregranted pursuant to the Mining Act 1992.

Beore the Minister or Mineral Resources grants a mininglease, the Mining Act requires notices o the proposal to beserved, by the Department o Mineral Resources, on eachgovernment agency that would be materially aected by thegrant o the lease. The Act gives the government agency,upon whom a notice has been served, a statutory right toobject to the granting o the lease or to require conditions to

be included in the lease. Provision is made in that Act or theresolution o any dispute. Subject to the grant o developmentconsent, mining leases are granted by the Minister or MineralResources - Reer Flow Chart.

Under its charter, the Mine Subsidence Board is not bound toobject on grounds o damage compensation, but may advise theChie Inspector o Coal Mines o the risk o damage, i any.

Similarly, beore inviting tenders or a mining l ease, the MiningAct requires the Minister or Mineral Resources to ollow theabove procedures.

Reerence: Schedule 1, Part 2, Division 1, Sections 5-10,Mining Act 1992.

3.1.2 Approvals to Extract Pillars/Longwalls

Section 138 o the Coal Mines Regulation Act 1982, providesthat no method o mining other than the bord and pillar systemshall be used except with the approval o the Minister. Pillarextraction and longwall mining applications are normallyapproved by the Chie Inspector o Coal Mines under delegationrom the Minister or Mineral Resources and subject to suchconditions as may be imposed.

In accordance with approved practice, the Chie Inspectoro Coal Mines examines all applications or approval under

Section 138 o the Coal Mines Regulation Act and processesthem in accordance with Section 3.3.3 - Undermining ExistingRoads.

3.2

ROAD ROUTE SELECTION

3.2.1 General

The selection o a route or a road involves consideration oenvironmental, social, economic, technical and geometricconstraints. On occasions, the various constraints confict andit is necessary to achieve a compromise which optimises thepublic interest and also recognises the legitimate rights o allpersons concerned.

SECTION2

EFFECTS OFCOAL MININGON ROADSThe eects o underground coal mining on roads are theresultant ground movements and damage. Damage is causedby vertical subsidence, horizontal strains, ground curvature andtilt. Subsidence eects may aect the serviceability o roads,bridges and roadside structures. Minor damage, not leadingto unserviceability is also a possibility.

The eect o subsidence on roads and bridge structures can belimited by designing them to accommodate specied strainsand displacements, or by carrying out mitigatory works.

The eects o open cut coal mining on roads are dierent,in that relocation or deviation o a road is oten possible, butmay involve substantial costs and a suitable alternative routemust be ound.

Further details o the impact o coal mining on roads areincluded in Appendix B.

Throughout this document the term roads is to be interpretedas meaning public and classied roads under care and controlo Roads and Trac Authority o NSW or Local Government,but excluding local streets, lanes and secondary roads.


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3.2.2 Constraints

In general, route selection involves the determination o themost suitable route between two nominated end points, butrom time to time, there are complicating actors such as thedesirability or necessity or the road to pass via a third localitywhich may be a centre o growing demand. A range o actorswhich may aect the nal selection o a road route i nclude:

* Trafc Demands

* Topography

* National Parks and Nature Reserves

* State Forests

* Mineral Prospects and Mining Operations

* Airstrips

* Urban and Industrial Areas

* Areas o Signiicant Environmental, Historical or

Archaeological Interest

* Scientifc Establishments

* Pipelines

* Railway Lines

* Other Roads

* Communication Networks

* Irrigation Areas

* Property Owner Requirements

* Flood Prone Areas

* River Crossings

* Geotechnical Aspects

* Projected Growth Areas

3.2.3 Consultation with Public Authorities

As a standard procedure, the Roads and Trac Authorityexchanges correspondence with numerous Commonwealth,State and Local Government authorities regarding its majorroad deviation proposals. The Department o MineralResources and the Mine Subsidence Board are included in thisprocess when appropriate. All potentially aected authoritiesare requested to comment on the Authoritys proposals and,where appropriate, to provide any inormation that may berelevant to the detailed route location, road design, andenvironmental assessment o the project.

Where roads are to be constructed through Mine SubsidenceDistricts, this process o consultation should, in most cases,lead to the accommodation o the Boards requirementsconcerning the siting and design o the roads and bridges.Formal application and approval to construct is required underthe Mine Subsidence Compensation Act. Formal applicationbeore the detailed design stage will acilitate meeting theBoards requirements without delay or change to design.Application should be made as soon as the particular routeis proposed.

3.2.4 Procedures under the Environmental Planningand Assessment Act

Roads are generally covered by the provisions o Part V o theEnvironmental Planning and Assessment Act, 1979, which

makes the Roads and Traic Authority the DeterminingAuthority or its road projects. This requires the Authorityto carry out an environmental assessment o all its roadproposals.

I it is decided that a particular road will have a signicantimpact on the environment, an Environmental Impact Statementis prepared by the Roads and Trac Authority, placed on publicdisplay, and submissions rom interested parties are receivedand assessed.

Finally, a determination report recommending a particular routeor the road is prepared and also made public. In general, orall major roads and bridges in urban areas it is necessary toprepare Environmental Impact Statements.

3.3

CO-ORDINATION OF MINING ANDROAD BUILDING ACTIVITIES

3.3.1 Planning New Roadways(a) General

When the Authority is planning routes or new or replacementroads and/or associated inrastructure, the Department oMineral Resources and the Mine Subsidence Board will benotied o the proposed route as part o the Authoritys planningprocedures. The proposed route would be assessed in termso its interaction with proposed or existing coal mining in thearea traversed.

In order to acilitate these assessments, the Authority will , inconjunction with the Department o Mineral Resources andMine Subsidence Board, arrange liaison meetings where theproposed route can be considered in relation to any mining(planned or existing). The Department o Mineral Resourceswill arrange or the appropriate collieries to attend or berepresented at these liaison meetings.

(b) Liaison Meetings

The goals o the liaison meetings are to:

(1) identiy coal resources and their mining status

(2) establish realistic subsidence design parameters

(3) identiy the most appropriate design solution(including deviation and relocation) or the roadwayand inrastructure, and the associated costs

(4) determine the type and degree o monitoring that maybe appropriate

(c) Design Solutions

When identiying the appropriate design solution, considerationwill be given to designing roads and structures to:

( 1) accommodat e t he pr ed ic t ed subs idenceparameters

(2) make provisions or mitigatory or preventative worksin the uture when and i appropriate

In selecting the appropriate design solution, consideration willbe given to designs that provide the optimal economic solutionor the community.

The liaison meetings will consider the costs o proposed designsolutions and make recommendations to the Department o

FLOW CHART FOR GRANT OF MINING LEASE

1. DMR approves Conceptual Project Development Plan

2. DMR organises Planning Focus Meeting - Designed to

provide early interace between Govt. and company to as-

sist in preparation o EIS and Schedule 1,

Part 2, MA reerencing

Application or Mining Lease lodged

DMR makes reerence to RTA

Schedule 1, Part 2, Division 1,

Section 5 o MA

DMR advises applicant to apply or

Development Consent

DMR provides comments

on EIS to DUAP

Development Consent determined

by Consent Authority

RTA objects to or proposes condi-

tions to be included in the mining

lease Schedule 1, Part 2, Division 1,Section 9 o MA

DMR ollows up any objections/pro-

posals with RTA Schedule 1, Part 2,

Division 1, Section 10 (1) o MA

DMR reers any unresolved

objections/proposals to Premier


Section 10 (1) o MA

Premier determines any

unresolved objections/proposals


Section 10 (2) o MA

Replies with possible requests or

special conditions

The Minister grants Mining Lease

Section 63 Mining Act

Legend

The Minister - Minister for Mineral Resources

MA - Mining Act, 1992

RTA - Roads and Trafc Authority

DUAP - Department of Urban Affairs and Planning


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(b) Liaison Meetings

Collieries preparing such an application should arrange aliaison meeting with the Authority, the Department o MineralResources and the Mine Subsidence Board to allow:

(1) discussion o the mining plan prior to ormal applicationbeing made to the Chie Inspector o Coal Mines. Thecolliery will provide the ollowing inormation:

* Depth o the extraction;

* Thickness o the seam to be extracted;

* Types o extraction (eg, pillar or longwall);

* Proposed start and nish dates;

* Location o proposed starting point;

* A scale drawing (1:8,000 or less) locating the proposedmining and showing appropriate easting and northingco-ordinates and location o aected structures;

* The maximum subsidence, strains and tilts at each othe structures;

* Details o any known geological anomalies that mayaect subsidence.

(2) the Department o Mineral Resources to assess and ratiythe collierys subsidence predictions

(3) the Authority to assess what, i any, mitigatory works and/or monitoring is appropriate, and to submit any specialrequirements that should be attached to the approval tothe Chie Inspector o Coal Mines

(4) the Mine Subsidence Board to determine i the aectedstructures are eligible or compensation under the MineSubsidence Compensation Act, to assess the cost omitigatory works and advise the Chie Inspector o CoalMines i appropriate

(5) the Authority to negotiate with the colliery regarding theallocation o costs that may not be compensatable underthe Mine Subsidence Compensation Act

(6) the colliery to nalise details o the application

(7) the Authority to submit a claim or compensation to theMine Subsidence Board and to obtain their approval orany design and mitigatory works that may be necessarywhen the application is approved by the Chie Inspectoro Coal Mines

(c) Lead Times

The existence o considerable lead times that can be involvedin mitigatory works must be acknowledged by all concernedparties. Some details o the type o works that may be requiredand the times involved are given in Section 3.3.4.

(d) Monitoring

It should also be noted that survey and visual monitoring maybe required in cases where no physical mitigatory works arenecessary. I t will need to commence prior to mining aectingstructures and to continue until, or practical purposes, minesubsidence has ceased.

3.3.4 Protective Measures

(a) Roads Constructed to Normal Design Standards

For roads which have not been designed to withstand groundsubsidence, the Authority would generally require considerablelead time o at least 12 months to be able to organise thecarrying out o any necessary precautionary measures tomitigate the subsidence eect on the aected roads or toenable a suitable alternative route to be arranged to allowsuch work to take place.

I the expected ground subsidence eects are so severe,particularly in regard to bridges, that practical measures to betaken to relieve the subsidence eects would not be adequate,the Authority would require either the undermining o suchstructures to be restricted to partial extraction or, alternatively,the relevant structure to be relocated, depending on which isthe more practicable and least costly option. The cost o thework meeting the approval o the Mine Subsidence Board,will be paid by the Board subject to the provisions o the MineSubsidence Compensation Act.

(b) Roads Constructed to Withstand Subsidence

I the road which is to be undermined has been designed towithstand the eects o a predetermined amount o groundsubsidence, the Authority would consider the applicationreerred to it bearing in mind the design parameters whichhave been incorporated.

Although a road has been designed or ground subsidenceeects, it may still be necessary to do some work on the road,such as survey monitoring. The Authority would generallyrequire considerable lead time o at least three months beorethe undermining was to take place.

(c) General

Notwithstanding any other modications or design eatures,it may also be necessary in isolated occurrences to take aroad out o service during the actual period o undermining.At the very least, an alternative route would need to beavailable in case the road was damaged during undermining.In addition, the Authority would probably arrange or its ownsurvey monitoring o the road beore, during, and ater theundermining o the road. Again, the Authority would generallyrequire considerable lead time beore the undermining is totake place.

All costs o mitigatory works, adjustments, repairs etcapproved by the Mine Subsidence Board, will be paid bythe Board subject to the provisions o the Mine SubsidenceCompensation Act.

3.3.5 Open Cut Mining

It is not possible or roads and structures to remain within opencut mining sites. It is thereore a basic requirement in routeselection that road routes be l ocated away rom areas wherethere are rm plans to mine by open cut, and where suitablealternatives are available, away rom areas likely to be minedby open cut within the lie o the road.

Where prospective open cut mining areas are large and miningplans are not rm, it may not be possible or a proposed new

Mineral Resources and the Mine Subsidence Board regardingthe allocation o costs, particularly when structures aredesigned to make provision or uture protective and mitigatoryworks.

(d) Design Approvals/Parameters

The above procedure will be modied slightly depending onwhether or not the proposed route lies in a declared MineSubsidence District.

(1) In a Mine Subsidence District

Once the route has been selected and the EIS processcompleted, the Authority should submit a ormal buildingapplication to the Mine Subsidence Board or the roadsand any associated inrastructure. Any approval granted bythe Mine Subsidence Board will be subject to conditions.Typically these include the submission o detailed engineeringdrawings certiying that the structures have been designedto accommodate subsidence parameters attached to theapproval, or detailing any provision or uture mitigatory works.

Normally such an application need only be accompanied byplans showing the location and outline o the structures. TheBoards approval should be obtained prior to any detaileddesign works being undertaken.

As part o the approval process, the Mine Subsidence Boardwill obtain current mine subsidence parameters rom theDepartment o Mineral Resources and include them in theapproval conditions.

(2) Not in a Mine Subsidence District

Beore detailed design is commenced, the Authority shouldobtain ormal subsidence parameters rom the Department oMineral Resources.

The Authority should notiy the Mine Subsidence Board othe subsidence parameters adopted or the design, to assistthe Mine Subsidence Board with administration o claims inthe uture.

To ensure that the road network and coal mining operationsin the area can co-exist, it is important that eective liaisonis maintained during the entire planning process. Participantsmust acknowledge that considerable lead times are involvedin the various stages o the process, and must be allowed orin any time scheduling.

3.3.2 Provision or Future Subsidence o ProposedRoads

Where rm mining plans have been developed which areliable to cause subsidence along the route o a proposed road,the Regional Oce o the Department o Mineral Resourcesundertakes to advise the Roads and Traic Authority inresponse to the Authoritys initial approach to public bodies andany subsequent Environmental Impact Statement associatedwith the proposal.

Where the Authority proposes to proceed with a routecrossing coal bearing lands where established mining plansare expected to aect the road within 10 years, the Authoritywill consult with the Department o Mineral Resourcesand mining companies when appropriate, regarding design

and construction o the road to withstand the anticipatedsubsidence. In all cases, Ministerial approval will be obtainedby the Department o Mineral Resources to restrict mining tothe extent to ensure subsidences are limited to those designedor. The use o subsidence tolerant structures will be consideredor all aected bridges. In the case o bridges or whichsuitable designs are not available, the location o the bridgeswill be optimised relative to the mine development plans.

Where mining plans are not rm, but the route is expectedto be aected by mine subsidence within 20 years or withinthe proposed lie o the road, the Authority will also consultwith the Department o Mineral Resources and the miningcompanies concerned to decide upon the design measuresor the road to provide or uture subsidence. An alternativewill be to consider modiying the road in the event that this isnecessitated by open cut or underground mining projects atsome uture time.

Where the Department o Mineral Resources advises thatan economic coal resource exists, but where there are no

established mining plans, the Authority will decide on theextent o design measures to be taken to provide or uturesubsidence in the light o any submission made by the MineSubsidence Board and the advice o the Regional Oce o theDepartment o Mineral Resources.

Where there is a Mine Subsidence District, the Authority willdesign and construct the road to withstand subsidence to theextent that may be required by the Mine Subsidence Board.Formal approval by the Mine Subsidence Board to the proposedroad beore detailed design must be obtained to avoid designchanges or delay. This approval will ensure compensation ordamage i the Authority has constructed the works accordingto Mine Subsidence Board requirements.

3.3.3 Undermining Existing Roads

Pillar extraction and longwall mining applications are normallyapproved by the Chie Inspector o Coal Mines under delegationrom the Minister or Mineral Resources under the provisionso the Coal Mines Regulation Act 1982.

(a) Pillar/Longwall Extraction Approvals

As part o the application process or approval or pillaror longwall extraction o coal by underground methods,collieries are required to address issues associated with the

mining plan and its eect on the ground surace and existingstructures. They are required to identiy all structures aectedby the proposed mining, and to assess the eect o resultingsubsidence on them. In this context:

(1) structures includes ormed roads, batters, embankments,drains, etc

(2) subsidence means all horizontal and vertical groundmovements resulting rom mining, and when major servicesand inrastructure are involved, the colliery should assumeconservative values or the angle o draw, say 35, eventhough subsidence calculations and assessments may bebased on lesser values. This will ensure that the owners/operators o major services are made aware o mining inthe vicinity o their installations and will allow the eectso subsidence on them to be assessed independently.


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Typically, the ollowing subsidence parameters would bespecied in the conditions o approval:

Vertical Subsidence x mm

Compressive Strains y mm/m

Tensile Strains z mm/m

Tilts w mm/m

Radius o Curvature v km

The Board requires the designer to certiy on the drawingsthat improvements covered by the approval will remain sae,serviceable and repairable in the event o the structures beingsubjected to the specied subsidence. The designer is tostate on the drawings the subsidence parameters that wereincluded in the design. This would normally be included withstatements detailing design loads (ie, dead, wind, live andany special loads).

Where a condition o approval requires certication o plansby designer:

- ater subsidence, any damage will be repaired under theprovisions o the Mine Subsidence Compensation Act,but the damage is expected to be consistent with designrequirements.

- serviceable means that the improvement must be ableto continue to be used or the purpose or which it wasdesigned.

- sae means that occupants and users o the improvementmust not be at risk rom loss or reduction o assetintegrity.

- repairable means that materials and their method outilisation allows damage ater subsidence to be repaired/replaced economically.

3.4

CHOOSING BETWEEN ROADMODIFICATIONS AND COALSTERILISATION

3.4.1 The Least Community Cost Principle

It is anticipated that, rom time to time, situations will arisewhere, as a result o a road being aected by a mining proposal,it is necessary to choose between sterilising coal reserves andrelocating or repairing a road to make sae. Whilst it is not

practicable to quantiy in general terms the relative communityand economic merits o sterilising amounts o coal againstrelocating or modiying specic road structures, it is possible toassess all situations in terms o an agreed guidi ng principle.

On this basis, it is agreed that each individual situation willbe assessed on its own merits and the course o action whichrepresents the least cost to the community will be given dueweight. That is, i the cost to the community o coal sterilisati onis less than the cost o modiying or relocating specic roadstructures, then, subject to the Ministers approval, the coal willbe sterilised. I the cost to the community o coal sterilisationis greater than the cost o road modication, then considerationwill be given to the practicality o relocating the road.

3.4.2 Trafc Costs

In determining the cost o any road modications which maybe necessary to allow undermining to proceed, three actorsthat need to be considered are:

(a) Actual Di rect Cost o Modifcations

The actual cost o road modication/repairs or mitigatoryworks, including the provision and maintenance o anytemporary inrastructure, depends on the amount o workrequired, and whether the aected road is already in serviceor in the planning/design stage. The more structures thatrequire modiying or the longer the section o road requiringrelocating, the higher the cost. In addition, the type o roadconstruction greatly infuences cost. Finally, the scope ormodiying an existing road other than by reconstruction islimited when compared to the scope available at the planning/design stage.

The actual cost o any particular proposal is readily denablein that the Roads and Trac Authority can provide budget

estimates or the various types o road construction. Inecessary, these estimates can be veried by the callingo tenders or the work involved. As discussed in previoussections, these costs will normally be borne by the MineSubsidence Board or undermining o existing roads.

In a major road system such as the NSW classied network, itis o paramount importance that the system is operated withoptimal eciency at all times to ensure that the cheapestreliable road transport is provided to the community.

(b) Increased Trafc Operational Costs

Increased traic operational costs will result when it isnecessary to take a particular road out o service to allowmodications, repairs or mitigatory works to be perormed.

When taking an existing road out o service or modicationor reconstruction, arrangements have to be made to ensurethat the system is operated such that there is suicientreserve capacity to cover the unexpected loss o anothernetwork element. In addition, because o the unavailabilityo a particular road or service, it may be necessary to alterthe operating conditions o the system with the result thatcost penalties are incurred. Depending on the nature o theroad being taken out o service, and the conditions applying atthe time, these cost penalties may vary and may be obtained

rom the Authority.

(c) Community Costs

Environmental considerations associated with the modicationor relocation o a road may incur costs to the community.

These considerations will vary and each case must beassessed on its own merits. Some o the actors which meritconsideration include visual impact, aect on natural amenity,noise, vibration, dust, and the availability/desirability oalternative routes.

route to avoid such areas altogether. In such a case theAuthority will determine the most practical route having regardto all constraints including the possible uture mining.

Open cut mining operations are matters which will be approvedor reused by the Minister or Mineral Resources under theprovisions o the Mining Act and the conditions o coal leasesgranted thereunder.

The Department o Mineral Resources undertakes to reerapplications or this type o mining to the Roads and TracAuthority or comment where such mining would directly aectan existing road or a road proposal.

I open cut mining is later proposed and aects the chosenroute, the matter o satisactory deviation o the road shall besubject to agreement between the Authority and the miningcompany concerned.

In order to relocate a section o an existing road, the Authoritywould generally need at least three (3) years notice and shouldbe inormed as soon as a mining proposal is available. (Note:

This assumes that an Environmental Impact Statement or theroad deviation is not required.) In general the Roads and TracAuthority has agreed to deviate roads wherever an acceptablealternative route could be obtained and agreement could bereached in respect o costs.

The Authority recognises that ground consolidation can bea very lengthy process at sites where open cut coal mininghas ormerly been conducted and the areas have beenrehabilitated.

The Authority will select any route in close proximity to anexisting or proposed open cut mine, or crossing an areaormerly mined, in the light o appropriate geotechnical reports,with a view to ensuring that the road is not damaged by groundmovement precipitated by the mining. In a Mine SubsidenceDistrict, the Mine Subsidence Boards approval will be explicitlyobtained in the usual way.

Where operations o an open cut mine are being planned totake place adjacent to an existing transmission line, typicalconditions that the Authority may request the Chie Inspectoro Coal Mines to attach to any approval are:

(1) prohibition o excavation within the road easements.

(2) provision o appropriate geotechnical report detailing

estimated ground movements. The geotechnical reportshould also include a stability analysis o the high wall andtake into consideration any adverse eects on the slopestability due to blasting o the overburden.

(3) requirement to perorm inclinometer and survey monitoringo the ground movement at appropriate intervals.

(4) requirement that areas o open cut mines adjacent toexisting roadways be backlled as soon as mining in thevicinity o the aected roadway is complete.

3.3.6 Forward Mining Plans

The Mine Subsidence Board has current programmes tomonitor mining under major structures subject to potentialsubsidence damage. These involve annual liaison meetings

between the Department o Mineral Resources, collieries andthe Mine Subsidence Board. Roads are recognised as majorstructures within these programmes.

Under these programmes, coal mining companies are requestedto supply mining plans which may aect major structures on theground. Generally, both short term and long term mining plansare obtained rom mining companies. The Mine SubsidenceCompensation Act 1961 contains provisions that, i necessary,require mining companies to provide i normation required bythe Mine Subsidence Board. The Board undertakes to supplythis inormation to the Roads and Trac Authority promptly onbecoming aware o a plan aecting any major structure underthe Authoritys control.

3.3.7 Mine Subsidence Board Approval Process

The Board approves building applications received rom theRoads and Trac Authority or proposed roads, road structuresand road realignments and deviations in Mine SubsidenceDistricts, subject to conditions.

The approval process has been designed so that developerscan submit building applications, including conceptual plans, atthe planning stage. This allows subsidence design parametersto be determined prior to detailed design and planning beingcommenced.

Typically, these conditions o approval may require that:

(a) Final engineering drawings are submitted to the Boardprior to the commencement o construction.

(b) Final drawings are certied by an appropriately qualiedengineer that improvements constructed in accordancewith the speciications and drawings will be sae,serviceable and repairable, taking into account specicmine subsidence parameters or the site(s) involved. (Sitespecic parameters would normally be specied as part othe approval.)

(c) Other special conditions, i appropriate, eg,

- Requirement that a geotechnical report be supplied

- Requirement that special supervision be undertaken

- Requiremen t that work as executed drawings be submittedon completion

- Requirement that special eatures be catered or orprovided or in the design (eg, provision o platorms and

access or relevelling jacks)

- Requirement that progress reports or specic events bereported to the Board (eg, notice o concrete pours, etc)

- Specication o a design levels in food prone areas

- Requirement that geotechnical exploration be undertakento dene limits and extent o old workings

Improvements constructed in a Mine Subsidence District that

do not satisfy the conditions of approval, are not eligible for

compensation under the Mine Subsidence Compensation Act.


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LEGISLATIONLegislation reerred to in the Guidelines includes:

* Roads Act 1993 - which governs the opening, control,administration, construction and maintenance o the publicand classied roads and the relationship between theChie Executive o the Roads and Trac Authority and theother Government and Local Government Authorities andinstrumentalities.

* Environmental Planning and Assessment Act 1979- which embodies the general provisions relating toland use planning, zoning, preparation and exhibition oenvironmental planning instruments, local environmentplans, and environmental impact statements.

* Land Acquisition (Just Terms Compensation) Act1991 - under which the Authority is empowered to resumeland or its various undertakings.

* Mining Act 1992 - covering the issue o titles to mine or

and/or prospect or minerals and coal, and also includesprovisions or including in the Register o Colliery Holdingsnew colliery holdings or making amendments to existingholdings. Approvals or open cut coal mining activities aredealt with under this Act.

* Mine Subsidence Compensation Act 1961 - underwhich the Mine Subsidence Board controls, amongother things, the establishment o roads through MineSubsidence Districts and considers claims or compensationor damages as a result o underground coal mining.

* Other legislation which can aect the siting o roadsincludes various Acts covering the operation o other publicauthorities including, but not limited to:

National Parks and Wildlie Service

State Forests o NSW

Heritage Commission (Commonwealth)

Heritage Council o NSW

National Trust o Australia (NSW)

Sydney Water Corporation

Hunter Water Corporation

Department o Land and Water Conservation

TelstraDepartment o Transport NSW

State Rail Authority o NSW

Department o Urban Aairs and Planning

Department o Public Works and Services

SECTION4

3.4.3 Coal Mining Sterilisation Costs

The determination o the cost o sterilisation o coal due to theneed to protect surace structures, is quite complex. Factorsto be considered are:

(a) The value o coal directly sterilised;

(b) The value o coal indirectly sterilised due to subsidencerestrictions; including the eect o the loss o the aectedportion o the coal mine on the overall operations andviability o the mine;

(c) The community cost arising rom the loss o a non-renewable resource and the shortening o mine lie.

Coal is sterilised directly when it is let in place in order tosupport a surace structure. The two normal methods used toprovide such support are total sterilisation within a nominatedangle o draw or the use o a subsidence control mining method,such as panel and pillar extraction, that may reduce thepercentage o coal recovered rom 90% to less than 50%.

As well as coal being sterilised directly by subsidencerestrictions, a urther quantity is likely to be lost due to thegeometric constraints placed on the mine layout. For example,i a road cuts across one end o a proposed longwall panel atan oblique angle, the whole panel, and possibly an adjacentone also, may be sterilised because o the practical inability torotate panels or to extract irregular pockets o coal by modern,high production longwalls.

As a typical longwall panel can contain in excess o 1,000,000tonnes o coal, the quantity lost due to indirect sterilisationcan quickly become very signicant.

Once the total quantity o coal to be sterilised, both directlyand indirectly, has been determined, the next step is toassign a value to it. For the purposes o these guidelines, thevalue per tonne o coal sterilised will be taken as being thedierence between the market price (at the mine gate) and theincremental cost per tonne o winning the coal. This value ocoal might be higher i other actors have stronger infuences,such as export demands, etc. Users should check this valueat time o estimate.

From an economic viewpoint, it is desirable that non-renewableresources such as coal be exploited to the ullest extentpossible. Similarly, rom the viewpoint o the mining industry, itis desirable to extend the economic lie o each mine or as long

as possible by ensuring that the greatest possible percentageo the coal is mined. However, as with the community costo road works, it is not possible to dene a simple approachto the assignment o value to this actor. Nevertheless,when evaluating a proposal which will involve sterilisation ocoal, every eort should be made to determine whether it isappropriate to adopt a purely economic evaluation that onlyconsiders utilisation o the resource, or should the evaluationbe expanded to include community cost, environmentalimpacts, community attitudes, etc.

3.4.4 Procedural Matters

In order to aord the maximum fexibility in modiying minelayouts, road locations and designs, it is important thatconsultation and the assessment o the relative merits ocoal sterilisation and road modication be carried out at theearliest possible time.

Accordingly, as soon as it becomes apparent that a coal miningproposal is aected by an existing road or a road proposal isaected by an existing coal mining operation, consultationshould commence. This will be initiated by any o the involvedparties depending on circumstances, eg, by the Board when theroad is in a Mine Subsidence District; by the Department oMineral Resources when the road is not in a Mine SubsidenceDistrict; by the Roads and Trac Authority when a roadproposal is involved; by the mining company when requiredby condition o approval o the particular extraction.

Once a course o action has been determined in acordancewith the principles outlined in 3.3.1, 3.3.2 and 3.3.3, i t is likely

that compensation or reimbursement will be payable underthe provisions o the Mine Subsidence Compensation Act1961 or i the Act does not apply, under the terms o a prioragreement between the Roads and Trac Authority and themining company.

Where an existing road is involved, the costs associatedwith precautionary and/or remedial measures by the Roadsand Trac Authority, including the cost o survey monitoring,will be reimbursed by the Mine Subsidence Board subjectto compliance with the provisions o the Mine SubsidenceCompensation Act.

Reerence is made to Section 3.3.2 in respect o designing oruture subsidences.


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CUTAWAY VIEW OF TYPICALMODERN COLLIERY

Longwallmining unit

Bord and pillardevelopment

1 Drit or men and materials access

2 Shat winder house

3 Bathhouse and administration building

4 Workshops

5 Coal preparation plant

6 Coal storage bins

7 Gas drainage system

8 Longwall mining unit9 Coal seam

10 Continuous miner

11 Coal pillar

12 Underground coal bin

13 Main roadway

14 Coal skips bring coal to the surace

(Not to scale. Diagrammatic only)

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COAL MININGAND ITSEFFECTSA1

TECHNOLOGY OF MINING

In 1982-83, nearly 70% o coal in NSW was won byunderground mining methods and the remaining 30% by opencut methods; longwall mining provided approximately 12% othe underground coal production. In 1993-94, 50% o coal waswon by underground mining methods, 77% o which was bylongwall. The total production in NSW has increased rom 67million tonnes in 1982-83 to 84 million tonnes in 1993-94. Morerecent gures are available rom Joint Coal Board publications,Australian Black Coal Statistics and NSW Coal Year Book.

Underground extraction o coal in NSW is generally carried out

at present at depths o mostly less than 500 metres. Nearly50% o total coal production in 1982-83 was at depths lessthan 200 metres. Mining at depths greater than 200 metresis increasing, especially in longwalls.

For coal mineable by underground methods, a practicalminimum seam thickness is 1 metre. The seams mined in thepast mostly all within the thickness range o 2.5 to 3.5 metresand most underground coal production was derived rom seamswithin this range.

Open cut coal extraction in NSW is generally conned to linearoverburden to coal ratios not greater than 10:1 and a maximummining depth o 300 metres. In practice, however, coal by opencut methods is currently mined at much shallower depths.During 1982-83 the greatest depth worked was 88.5 metresand the weighted average overburden to coal ratio was 4.6:1.These gures have not changed signicantly.

A2

UNDERGROUND MINING

Underground mining practices ollowed in NSW all into threemain categories: bord and pillar mining ( rst workings), partialextraction, and total extraction.

Development Headings are roadways (tunnels) that aredriven to provide access to areas o virgin coal. Normally drivenin groups o up to our roadways with cut-throughs betweenthem, they orm a development panel and are used to blockout large areas o coal that will be extracted by longwall orpillar extraction methods.

Bord and Pillar methods o mining are well establishedand widely varied. They comprise a network o undergroundroadways (tunnels), interconnected as shown in Figure 1,leaving blocks o coal, generally square or rectangular inplan view. These are termed pillars. Historically, the sizeso pillars and roadways ormed in this system o mining havebeen specied in lease conditions and under the provisions othe Coal Mines Regulation Act, 1982. In recent years, pillarshave been required to be designed with long term stability toensure mine saety.

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Pillar sizes, and the number o roadways in any particularpanel (mining region), also vary considerably depending onthe purpose o the panel. Any o the extraction systemsdiscussed below require access to the coal to be extracted,and so bord and pillar workings are used as the means oblocking out the coal or this purpose. In this sense, the bordand pillar workings are also reerred to as rst workings, ordevelopment workings.

When bord and pillar workings are developed, they causenegligible surace subsidence and consequently no mining-induced ground strain (see Section Figure 1).

Partial Extraction can take various orms depending onmining conditions, production requirements and constraintssuch as subsidence control. Essentially, partial extractionreers to any mining method where, within a block o coal,large quantities o coal are removed, but some remains. Thismay take the orm o partial pillar extraction, or pillar spli tting,within a panel o bord and pillar workings, or it may be on alarger scale where alternate panels are ully extracted while

the intervening blocks o coal are let intact.

This latter method, sometimes reerred to as panel and pillarmining (Figure 2), is a variation o selective partial pillarextraction methods and is used to prevent or control suracesubsidence. In this method, panels are separated by longbarrier pillars o sucient width to support the overlyingstrata, even i the immediate roo over the extracted panelssags considerably or ails (caves). By careul selection o thepanel and pillar geometry relative to mining height, depth oworkings and strata conditions, surace subsidence can becontrolled successully and the level o dierential subsidenceor lateral strain aecting surace eatures or structures, canbe restricted.

Total Extraction is an extension o partial extraction wherebyas much coal as can saely and economically be mined isremoved rom each panel, leaving only small remnant pillarsor narrow barrier pillars and pillar regions. These oten crushout as the major overlying roo strata settle and the suracesubsides. Total extraction is achieved either by large scalepillar extraction rom bord and pillar workings over a largearea, or by mining o wide blocks o coal between narrowdevelopment panels using the longwall method (see Figure3).

Total extraction is the avoured mining method wheresubsidence is not restricted, as it leads to maximum coalrecovery, and minimum sterilisation o resources. Where thecoal can be totally extracted, prior to construction o suracestructures, they can be built on stable ground which has alreadyundergone complete subsidence. Total extraction results inmore predictable and uniorm strains and subsidences whichsimplies the control o surace development.

A3

SUBSIDENCE EFFECTS

A3.1 General

A subsidence basin orms on the surace when coal is extractedover a wide area. The amount and extent o subsidence

depends on many actors which include the geometry o theextracted area, the layout o unmined pillars, the number oseams mined, the coal recovery rom each seam, the nature othe superincumbent strata and other geological actors.

When development headings are driven, no signiicantsubsidence occurs. Generally, or bord and pillar workings,subsidence can be around 20 mm. Over a large area o pillaror longwall extraction where the critical extraction width isexceeded, subsidence can be up to 65% o seam thickness.

The main elements o a subsidence prole are the verticaldisplacement (subsidence), the change in ground slope and thecurvature o the ground surace which determines the amounto surace strain. These elements can be calculated rom eldobservations o level o and distance between monitoringpoints using standard survey techniques. Proles o subsidenceand associated characteristics are derived rom the eld data.Some o the terminology used in dening surace subsidenceis shown in Figure 4.

In the case o longwall mining, most o the subsidence generally

takes place soon ater mining. In a virgin area, up to 10% omaximum subsidence can occur as delayed subsidence. Inthe case o pillar extraction with standing unmined pillars inthe goa, subsidence can continue or a long time due to thecollapse or gradual ailure o any unmined pill ars over time.

Dykes or ault planes can aect subsidence and strain proles.They can provide a plane o weakness in the strata whichunder certain circumstances could acilitate subsidencemovements. Surace cracking need not necessarily occurwhen such geological eatures are present. The occurrenceo surace cracking and its extent, generally depends on theamount o strain.

The eects o ground movements are important in areaswhen there are structures or surace eatures which requireprotection. Dierent types o structures have dierenttolerances to subsidence.

Construction o new structures can be deerred until mining hastaken place and subsidence is complete. It may be possibleto modiy existing structures to enable them to withstandanticipated subsidence. Proposed structures can be built withallowances or subsidence. Whether subsidence movementsoccur or are allowed to occur under structures or suraceeatures depends on several actors. The importance o thestructure and any socio-economic consequences o damage

will need to be careully considered in relation to the coalwhich could otherwise be sterilised.

A3.2 Underground Extraction

(a) Bord and Pillar Mining (First Workings)

Studies in NSW have observed subsidence values overbord and pillar workings without pillar extraction oapproximately 20 mm.

Determining values o mine subsidence or values o thismagnitude is complicated by other actors. Standards andtolerances o surveys have to be considered and changesresulting rom natural groundwater movement or swelling/contraction o surace soils/clays in excess o 50 mmare not uncommon. This ground movement occurs quiteindependently o any mining infuence.

FIGURE 1SUBSIDENCE FROM BORD AND PILLAR MINING

ZONE OF INFLUENCE

WORKED AREA

SMALL SUBSIDENCE

ORIGINAL SURFACE

COAL SEAM COAL SEAM

A. Bords or RoomsB. Pillars

A

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Undetected geological anomalies or poor mining practicemay lead to unusual subsidence.

Limits can be placed with reasonable condence on suracemovements due to mining as empirical and mathematicalmethods have been proved reliable.

In summary, given good mining design and practice, bordand pillar (irst) workings should cause no damagingsurace subsidence.

(b) Partial Extraction

The subsidence eects o irregular partial extractionmethods can be quite signicant on the surace in termso both vertical displacement and strain. Where thepartial extraction involves pillar splitting or extensive pillar

extraction there can be also a signicant time delay in thedevelopment o total subsidence.

In a panel and pillar extraction operation, it is possibleto careully control and limit the amount o suracesubsidence. This can be achieved by designing the widthso both panels to be extracted and the barrier pillarsbetween them to suit strata conditions and depth. Omore importance, the dierential subsidence over pill arsand panels can be careully evened out so that the suracestrains are negligible, thereby protecting any sensitivesurace eatures.

(c) Total Extraction

Total extraction generally results in 80%-90% recovery, byplan, o the coal seam. In NSW strata conditi ons, maximumsurace subsidence can amount to approximately 65% o

the extracted seam thickness, once the total extractionarea exceeds a critical width.

Over the extremities o the extracted area, peak strainsoccur at the surace (see Figure 4). The magnitude othese strains is dependent on depth and strata conditions.The angle o draw dening the limiting lateral extent osubsidence is also very dependent on strata conditions andcan vary typically rom 0 to 35.

In total extraction, as with all mining methods, given acombination o empirical guidelines based on measuredsubsidence data, structural and geotechnical strataproperties and modern numerical design techniques, itis possible to design mining layouts to predict and hencecontrol surace subsidence with a reasonable degree o

reliability.

A3.3 OPEN CUT OPERATIONS

Ground movements can occur both during the mining operationand ater rehabilitation due to the consolidation o the backll.Very little published inormation is available in Australia onthe ground movements associated with the consolidation andsettlement o backlled areas o open cut mines.

The area o infuence behind the crest o a deep excavationslope depends upon the type o coal measures. Movementshave been observed or a distance o 2.5 and 3.0 timesthe height o the slope behind the crest in clayey soils. Inexcavations in the stronger coal measures, it is generallybelieved that this distance reduces to less than the height othe slope. In clayey material, the movements are presumed to

FIGURE 3LONGWALL MINING

A

E

A. Longwall Panel Extraction CompletedB. Longwall Panel Extraction in ProgressC. Small Remnant Pillar between Longwall PanelsD. Main HeadingsE. Development Headings to create next Longwall Panel

C

B

D


FIGURE 2SUBSIDENCE FROM PANEL AND PILLAR MINING

SECTION

A. Panel 1B. Panel 2C. Standing Pillars

B

A

C



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THE IMPACT OFCOAL MININGON ROADSB1

GENERAL

The primary eects o mining on road pavements andstructures are subsidence displacements, ground strains, tiltand deormation o structures or ootings.

All structures within the angle o draw o the extraction willbe aected by the ground displacements and resulting strainsand tilts. The magnitude o these subsidence eects canbe predicted prior to mining and their eect on existing andproposed structures can be assessed.

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FIGURE 4

(Source: National Coal Board 1975)

TERMINOLOGY ASSOCIATED WITH SUBSIDENCE

ANGLE OF DRAW - Angle between vertical at edge o workingsand line joining edge o workings to 20mmsubsidence point at surace

sm MAXIMUM SUBSIDENCE - Occurs at the centre o the panel when work-ings reach critical width and length

E STRAIN - Lengthening or shortening in subsidencetrough per unit length

M SEAM THICKNESS

W WIDTH OF WORKINGS

(or Limit Angle)

(extracted)


result rom elastic recovery ollowing lateral and vertical stressrelie. In the coal measures, the movements are requentlytraced to shear ailure along discontinuities such as beddingplanes.

Displacements ater backlling are due to the consolidation othe backll material and are a unction o the type o materialand the depth o the ll. Observations have been madeover a period o between three (3) and six (6) years whenbackll material was placed in an open cut. The maximumconsolidation o 40 metres o overburden was observed to be200 mm in this case. The consolidation was also ound to beirregular, refecting variations in the type o material and thedegree o compaction.

Further work is required to predict subsidence in rehabilitatedareas o open cut operations. Structures in the vicinity o opencut mines could suer damage i these are located withinthe zone o infuence o the workings. The development orehabilitated lands should take account o ground movementsdue to the consolidation o the backll or a number o years.

B2

STRUCTURE TYPES AND FUNCTIONS

Subsidence may aect:

(a) Road GeometryHorizontal and vertical alignment, sight distances, etc

(b) Road StructuresDrainage culverts, subsoil drains, concrete kerbs,guardrails, barriers, sumps and outlets, embankments,batter slopes, etc

(c) Natural FeaturesWater courses


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1. Pacifc Highway Catherine Hill Bay

Location: Pacic Highway Catherine Hill Bay

Owner: Roads and Trac Authority

Colliery: Wallarah Colliery

Mining Type: Pillar Extrac tion in two seams(1984-1988)

Depth o Cover: 150 and 180 metres

Subsidence Predictions:

Maximum Subsidence ...........................1400 mm

Maximum Tensile Strain ........................3.5 mm/m

Maximum Compressive Strain ...............5.5 mm/m

Length o Road Aected: 1,200 metres

Actual Subsidence:



Maximum Compressive Strain ...............6.3 mm/mActual Damage: Surace damaged by compression humps

and tension cracks. Road surace wasconsidered very rough.

Method o Repair: Heavy patch ailed areas, place rubberbitumen and geotextile bandage overcracks, overlay pavement with 175mm asphaltic concrete and spray seal,raise guardrails, reconstruct suracedrains, replace pavement markings andsignposts.

Estimated Cost o Repairs: $2,263,608

DESIGNMEASURES TOPROVIDE FORSUBSIDENCESelection o types o pavements and structures that havesome inherent fexibility and that may accommodate someo the subsidence movements are appropriate strategies toadopt when designing roadways that will be exposed to minesubsidence.

Structures can be detailed to incorporate joints that allow theeects o ground strains, curvatures and vertical subsidenceto be accommodated. Such details will allow mitigatory worksto be carried out prior to undermining taking place. This willinclude providing access and details that allow girders andheadstock to be realigned by jacking, or supported on hydraulicjacks during the subsidence event.

When mining plans are available that allow subsidenceparameters to be established with some condence, roadgeometry and grades o drainage lines, etc may be designedto allow or the eects o subsidence, tilts and curvatures onthe road surace, drains, etc.

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CASE STUDIESThe attached case studies have been included in the Guidelinesto illustrate the types o roads that have been undermined andthe type and extent o mitigatory works and monitoring thathave been adopted.

The examples have been selected to illustrate the range oworks that have been undertaken to date when undergroundmining has produced surace subsidence with the potentialto aect roads.

As a result o the work undertaken, the roads have remained inservice and underlying coal resources have been recovered.

1. Pacic Highway Catherine Hill Bay

2. Freemans Drive Cooranbong

3. George Booth Drive Edgeworth

4. Link Road - F3 Freeway to Paciic HighwayDoyalson

5. Rockord Road Bridge Tahmoor


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4. Link Road - F3 Freeway to Pacifc Highway Doyalson

Location: Link Road - F3 Freeway to PaciicHighway Doyalson

Owner: Roads and Trac Authority

Colliery: Munmorah Colliery

Mining Type: Pillar Extraction (1995)

Depth o Cover: 180 metres

Subsidence Predictions


Maximum Tensile Strain ........................4 mm/m

Maximum Compressive Strain ...............4 mm/m

Length o Road Aected: 1,000 metres

Actual Subsidence:




Actual Damage: Cracking and distortion to the roadsurace in the orm o tension cracksand compression humps.

Method o Repair: Repairs were carried out by the Roadsand Traic Authority and includedmilling and paving with asphalticconcrete to the distorted and crackedsections to provide a smooth wearingsurace. Signs warning motorists opotential deormations were erected.Some nal repairs may be required.

Estimated Cost o Repairs: $32,387

5. Rockord Road Bridge Tahmoor

Location: Rockord Road Bridge Tahmoor

Owner: Wollondilly Shire Council

Colliery: Tahmoor Colliery

Mining Type: Longwall (2 adjacent longwall panels1994)

Depth o Cover: 425metres





Length o Road Aected: 75 metre long bridge

Actual Subsidence:




Note: 97% o measured strain values laybetween 0.5 and 1.5 mm/m

Actual Damage: The bridge remained operational duringsubsidence with some restrictions onspeed and lane closures.

Method o Repair: Preventative work put in place prior tosubsidence occurring had the bridgedeck supported by reaction trussesand hydraulic jacks supported by steelalsework. Hydraulic pumps were usedto automatically compensate or anymovement o the bridge deck, keepingit level during subsidence.

Estimated Cost o Repairs: $1,231,339

2. Freemans Drive Cooranbong

Location: Freemans Drive CooranbongMain Road 392

Owner: Lake Macquarie City Council

Colliery: Cooranbong Colliery

Mining Type: Longwall (2 longwall panels 1992)






Length o Road Aected: 900 metres

Actual Subsidence:




Actual Damage: Tension cracks and compression humpsto the road surace. Some ponding owater and loss o crossall drainage.

Method o Repair: Repairs were carried out under thesupervision o a consultant engaged bythe Mine Subsidence Board. Repairsinvolved the removal o the existingseal, regrade and recompact the existingpavement and overlay with a 125 mmthick road base, two coat seal, linemarking.


3. George Booth Drive Edgeworth

Location: George Booth Drive EdgeworthMain Road 223

Owner: Lake Macquarie City Council

Colliery: West Wallsend Colliery

Mining Type: Longwall (3 adjacent longwall panels1994-1995)






Length o Road Aected: 450 metres

Actual Subsidence:




Actual Damage: Cracking and distortion to the roadsurace.

Method o Repair: Repairs involved the rotomilling o theailed sections o the road surace to adepth o 30 to 50 mm and resheetingwith asphaltic concrete.



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INITIAL CONTACTS FOR ENQUIRIESRELATING TO MATTERS COVERED BY THE GUIDELINES

Mine Subsidence Board

Chie Executive Ofcer

District Supervisor - District Ofces at Newcastle, Wyong, Speers Point, Picton and Singleton

Department o Mineral Resources

Coal Mining Inspectorate and Engineering Services

Ofces at St Leonards, Cardi, Wollongong, Lithgow and Singleton

Colliery

Superintendent/Manager o Colliery involved

Roads and Trafc Authority

General Manager Inrastructure and Maintenance - Sydney

Regional Manager Hunter (Newcastle), Regional Manager Southern (Wollongong), Regional Manager Western (Dubbo), RegionalManager South Western (Wagga Wagga), Regional Manager Northern (Lismore)

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