Mining & Mined Caverns - Parsons Brinckerhoff

solutions 

Network 

ISSUe NO. 74 APRIL 2012 A technical journal by Parsons Brinckerhoff employees and colleagues http://www.pbworld.com/news/publications.aspx 

Mining & Mined Caverns 

P A r S o N S B r I N C k e r H o F F

Table of Contents 

APRIL 2012 http://www.pbworld.com/news/publications.aspx 

Introduction: Leadership in Mining and 

Mined Caverns – (Mark Dimmock) ...............................1 

MINING 

Feasibility Studies, Geological Assessments, 

Resource Estimation 

Mining Feasibility Studies – An Outline of the Technical 

Input, Requirements and Purpose of Mining Feasibility 

Studies – (Marco Maestri) ..........................................4 

Geological Assessment and Resource Estimation of 

Coal Deposits and Their Influence on Mine Design – 

(Aidan Parkes/Sam Moorhouse/Jonathan O’Dell) ........9 

The Relevance of International Reporting Codes and 

Their Practical Application to Resource Estimation – 

(Sam Moorhouse/Aidan Parkes) ...............................13 

Sustainability and Community Involvement 

Innovating a Better Environment Through a 

Sustainable Approach to Mining – (Ben Hall) ..............17 

Reshaping Social Impact Assessment: Implications 

for Resource Companies and Their Role in Housing 

Provision – (Ceit Wilson) ...........................................19 

Looking at Mining Differently - 3D Visualisation 

Helps to Take the Guess Work Out – (Alan Hobson/ 

Dylan Swan) .......................................................... 22 

Conveyor Systems 

High Lift Belt Conveyors for Underground Hard Rock 

Haulage – (John C. Spreadborough) ..........................25 

Conveyor Technology Selection for a Large 

Copper Project – (Scott Tapsall) ................................30 

Network 

Mining & Mined Caverns 

Guest Editors for this issue: Mark Dimmock and Nick Edmunds 

EPCM Risk Management 

Parsons Brinckerhoff Global Mining EPCM 

Risk Management: A Proactive Approach – 

(Jereme Evans) ..................................................... 33 

Stabilization of Mine Sites 

Fenwick Heap Stabilisation – (Russell Bayliss/Alan 

Common/Jeff Jennings)............................................36 

Mined Cavern Stability Survey and Risk Assessment 

for Multiple Use Storage Facilities – (Adrian Dolecki/ 

Gideon Jones) ..........................................................41 

MINED CAVERNS AND UNDERGROUND 

TUNNELS 

Mined Caverns 

Geologic / Hydrologic Requirements for Successful 

Mined Underground Hydrocarbon Storage Caverns – 

(Bruce Russell) ........................................................46 

A Conceptual Design for a Geological Disposal 

Facility for the UK’s Radioactive Wastes – (Steven 

Majhu/Peter Gaskell) ...............................................49 

Mined Caverns for Hydro-electric Projects – 

(Andrew Noble) ........................................................52 

Underground Tunnels 

Ground Observational Methods in Mined Tunnel 

Support Systems – ((Adrian Dolecki/Gideon Jones) ....55 

The Design of Sprayed Concrete Linings (SCL) to 

Form Junction Chambers for Tunnels in London Clay – 

(Binh Soo Liew/Terry Howes/Rory McKimm) ..............59 

Network 

Future Issue ............................................................62

In 2011, Parsons Brinckerhoff made the strategic decision 

to target the growing mining and resources market in 

a more focussed and comprehensive manner. On a global 

scale, the market offers substantial opportunities for mining 

services providers, both now and for the longer-term. 

Our clients have been telling us over recent 

times that what they are looking for is leadership – both 

in thought and delivery of their projects. When Parsons 

Brinckerhoff established the global mining business one 

year ago, we did so with a vision of being a leading provider 

of EPCM (engineering-procurement-construction management) 

services, leveraging the participation of Balfour 

Beatty operating companies in the development of mining 

and resources infrastructure (pit to port) along the development 

spectrum (concept to commissioning). 

The intent was to harness the broad range of capabilities 

within Parsons Brinckerhoff and Balfour Beatty, 

while building further capability and capacity to present 

an attractive offering to the market – that of an integrated 

contractor and services provider bringing the best study, 

engineering and delivery leadership to mining projects. 

Our core strategy is in four parts: 

1. To acquire capability in the key areas of process and 

mine planning; 

2. To continue our organic growth strategy of ‘following 

clients’ and diversifying across commodities; 

3. To leverage the capabilities of all Balfour Beatty operating 

companies; and 

4. To reinforce and develop core competency in delivery 

systems and procurement. 

We remain committed to our vision and strategy 

and have made considerable progress since inception of 

the business. 

Capability acquisition 

The first element of our strategy is to acquire mine planning 

and process engineering capability. These capabilities 

Network 

Leadership in Mining and Mined Caverns 

by Mark Dimmock, Sydney, Australia, +61 2 92725183, mdimmock@pb.com.au 

Performance for the mining industry will come from leadership. Those companies that invest in leadership 

skills – both management and technical thought leadership – will be the winners. Technical innovations 

are a bi-product, rather than the driver of this. 

enable us to become involved in projects at the earliest 

stage, thereby developing stronger collaborative relationships 

with mining companies. 

Whilst we are active in the acquisition of companies 

with specialized mining capabilities, we have also 

deemed it prudent to develop our core capabilities organically. 

We are expanding our mining engineering capability 

from the UK, initially into regions in Africa. We 

are also pursuing organic growth in process engineering. 

Organic growth will provide us with a platform to 

leverage any acquisition, and an ability to more readily 

integrate any acquisition. 

Geographic and commodity expansion 

Currently, Parsons Brinckerhoff’s global mining business is 

effectively in three stages of maturity: 

1. Australia’s Hunter Valley and Queensland region is the 

most mature, based on Parsons Brinckerhoff having long 

established relationships with many coal-mining clients, 

including the large diversified mining companies. 

• In the Hunter Valley, Parsons Brinckerhoff is considered 

a leader in the mining sector – a reputation 

earned over many years of delivering high quality 

studies and successfully executing projects. That 

reputation was reinforced by the completion of the 

Mangoola Project with Xstrata Coal in 2011, ahead 

of time and under budget. Parsons Brinckerhoff is 

also delivering the Ulan Project for Xstrata Coal and 

the Bengalla Expansion for Rio Tinto & Westfarmers. 

• In Queensland, Parsons Brinckerhoff secured the provision 

of EPCM services for BHP Billiton Mitsubishi Alliance’s 

sustaining capital program. We are also continuing 

to conduct studies in this region for Xstrata 

and this is positioning us well for future delivery work. 

2. Western Australia, Southern Africa (South Africa and Mozambique) 

and Australia’s South Central region all have 

enormous forecast expenditure on mine infrastructure 

APRIL 2012 http://www.pbworld.com/news/publications.aspx Introduction 

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Feasibility Studies, Geological Assessments, Resource Introduction Estimation 


2 

and are emerging, or re-emerging, as significant regions 

where Parsons Brinckerhoff is building client relationships 

and establishing our business. 

• From the foundations established in the Western Australian 

region over the last several years, study work 

for Atlas Iron has converted into execution work. In 

addition, we have completed studies for many clients, 

and a number of the projects where we provided the 

studies are now moving to delivery, and we are wellplaced 

to continue working with these clients, which 

include Rio Tinto, Aston Resources and Xstrata Coal. 

• Parsons Brinckerhoff also secured the EPCM for a 

rail maintenance facility in Western Australia’s Pilbara 

region for Fortescue Metals Group, and continues to 

provide services to Arafura on its rare earth project. 

• Australia’s South Central is also re-emerging in the resources 

sector. The multi-award winning Jacinth-Ambrosia 

Mineral Sands Project, and the infrastructure 

study undertaken for government, has maintained 

our brand as a leading player. 

• In Africa, Parsons Brinckerhoff will be assisting Anglo 

Platinum as part of an owner’s team on two platinum 

projects in South Africa in 2012. Also, the Tweefontein 

Project in South Africa has now been endorsed 

by the Xstrata Coal board and is likely to proceed to 

execution this year. 

• We are currently completing the feasibility study for 

Eurasian Natural Resources Corporation’s (ENRC) Estima 

Project in Mozambique. In this project, we are 

responsible for the full study, including mining (UK 

team), process and non-process infrastructure. 

3. There are a number of new regions in which Parsons 

Brinckerhoff is developing our mining business. These 

include Indonesia, Canada, Mongolia, and Brazil. 

In 2012, we will continue to strengthen our focus 

on client relationship management (CRM) and the differing 

needs of our clients. 

Balfour Beatty leverage 

Parsons Brinckerhoff is the professional services division 

of Balfour Beatty and, as such, continues to pursue joint 

opportunities with the overall Balfour Beatty group. This includes 

bidding on a number of projects with Balfour Beatty 

Rail in Asia and Southern Africa. 

A number of senior staff from Balfour Beatty’s 

construction businesses have been transferred to Parsons 

Brinckerhoff in response to feedback from clients that our 

approach to EPCM is strengthened with a contractor’s perspective 

and strong leadership in managing projects. As our 

business grows in 2012, we will continue deploying staff 

from the broader group and reinforcing project leadership. 

Network 

Delivery systems 

Parsons Brinckerhoff has commenced its transition to 

an EPCM business, characterised by a department structure 

which includes: construction management, construction 

services, procurement, SHEQ (safety, health, 

environment, quality), and IR/HR (industrial relations/ 

human resources). Department leaders are responsible 

for providing a consistent platform of policy, systems, 

processes and procedures. The advantages of this consistent 

approach across the business include an ability 

to quickly deploy knowledgeable staff to projects, and 

the ability to start a project with a readily mobilised system 

and experienced users. 

In 2012, we are also implementing a consistent, 

robust project controls system to further build and 

consolidate consistent excellence in project delivery. 

What makes us different? 

Our business model is to engage in projects at their 

earliest stage, working with our clients on evaluating the 

business case for their projects, and continuing our participation 

through to delivery. For us to be successful in 

this approach, we need to differentiate our offering. 

Our differentiators are our depth and experience 

across the Balfour Beatty group to complete the 

project and our very experienced study management 

team, supported by Parsons Brinckerhoff’s broad range 

of engineering capabilities. We have developed a global 

mining methodology for execution of studies and delivery 

of projects, with basic principles that can be readily 

applied to contracts in any region of the world. 

The mining services sector already has a number 

of significant global providers. So what will make us 

stand out from the crowd? Our ability to lead the way in 

integrating the very best thinking on mine planning and 

processing with clever and innovative engineering solutions 

and flawless project delivery capabilities. 

In this issue: thought leadership 

and excellence 

The articles in this issue demonstrate the fine minds 

and capabilities Parsons Brinckerhoff has in place, underpinning 

our commitment to ongoing investment in 

mining services leadership. 

Network’s Mining & Mined Caverns issue commences 

at the same point our clients do, with articles that 

provide insight into the process of evaluating the resource, 

a particular expertise of our UK-based mining practise. 

Sustainability and social license is a critical aspect 

of mining and, in the second section of this edition, 

the articles demonstrate how Parsons Brinckerhoff is

applying technology and making a positive contribution. 

Our third section is focused on conveyor technology 

and provides two good case studies on evaluation 

and use of contemporary technologies. Other sections 

are themed around risk management, a pertinent 

area when it comes to mining, and Parsons Brinckerhoff’s 

work in supporting mining projects. 

Mined caverns and tunnels is a sector where 

Parsons Brinckerhoff is a leading player. These articles 

demonstrate our depth of experience and knowledge in 

the space. Those pertaining to caverns for hydrocarbon 

storage, radioactive waste storage, and hydro-electric 

Network 

projects illustrate applications for mined caverns in different 

market sectors while articles about ground observation 

methods and sprayed concrete linings demonstrate 

the methodologies that we have employed. 

I have enjoyed serving as guest editor for this 

publication on mining and mined caverns, and appreciate 

the effort by all of the authors to share their knowledge 

and lessons learnt. I also want to thank the other 

guest editor, Nick Edmunds; the guest reviewers, Tim 

Smirnoff, Joanne Conradi, Graham Sterley, Tim Reichwein; 

and the editors, John Chow and Susan Lysaght, for 

their work on compiling and organizing this publication. 

Mark Dimmock 

Managing Director of Global Mining 

Introduction 


3

Feasibility Studies, Geological Assessments, Resource estimation 


4 

Parsons Brinckerhoff is currently focussed on feasibility 

studies in Africa, with an emphasis on coal prospects. 

This article highlights the process of a typical study with 

a discussion on common pitfalls and a case study. 

Mining Development Process 

Once an exploration resource with sufficient potential 

to warrant further investigation is discovered – and that 

can prove to be a lengthy and expensive process – the 

process of securing funding and carrying out a series of 

feasibility studies begins. A mining feasibility study is an 

important evaluation tool to assess the economic and 

technical feasibility of the project, as well as to identify 

flaws (fatal or otherwise) as part of the associated risk 

assessment. The context and process leading up to the 

implementation of mining is shown in Figure 1. 

The ultimate purpose of a feasibility study should be: 

1. To define and assess the project - specifically: 

• Scope 

• Technical nature 

Network 

Mining Feasibility Studies - An Outline 

of the Technical Input, Requirements and 

Purpose of Mining Feasibility Studies 

by Marco Maestri, Godalming, UK, maestrim@pbworld.com, +44(0)7917 212350 

Figure 1 - Mining Development Process 

• Project resources and reserves 

• Costs 

• Schedule 

• Economics 

• Risks 

2. As a sales document – used to support funding and 

offer confidence to investors who may not have technical 

expertise or access to the technical data. Scandals 

involving the corruption of raw data have led to 

the implementation of international reporting standards 

– the most notable of which include the JORC 

code (Australia), SAMREC code (South Africa) and NI 

43-101 (Canada). Adherence to these codes ensures 

consistency in the level of confidence and language 

on which lay persons (investors) can rely. 

3. As a planning document – at each stage the previous 

study should act as a ‘blueprint’ for the next 

level – e.g., a prefeasibility study should act as a 

planning document for the definitive feasibility study 

and so on. 

Typically, Parsons Brinckerhoff would concentrate 

on (1) and (3) from the list above and, as an independent 

consultant, would not be involved in the 

marketing of a resource development project, having to 

maintain a degree of independence from this process. 

Accuracy 

Feasibility studies are often prefaced with a term indicating 

the level of study accuracy: ‘preliminary’, ‘pre’, ‘final’, 

‘bankable’, ‘definitive’ are some of the terms often 

seen in the industry and understanding what they mean 

is an important part of the process. A list of common 

names used in the industry is shown in Figure 2, with 

the Parsons Brinckerhoff standard terminology shown in 

the top boxes.

Figure 2 - Common Names Used for the Feasibility Study Stages 

What Is Involved? 

A mining feasibility study is a multi-disciplinary evaluation 

of a mining project that integrates all facets of the 

mining business, including technical, political, regulatory, 

environmental and economic facets. High-level 

factors that require consideration in a feasibility study 

are shown in Figure 3. 

The complete mining life cycle is shown in Figure 

4, giving context to feasibility studies (shaded). 

Figure 3 - Feasibility Study Inputs 

Network 

The levels of study are: 

Scoping Study. A scoping study is carried out very early 

in the project life to determine if the project is economically 

viable and technically feasible. It may be used as 

a basis for acquiring exploration areas or making a commitment 

for exploration funding. A high-level mining scenario 

is usually considered at this stage, along with a 

risk assessment and a fatal flaw analysis, to highlight 

any potential ‘show stoppers’. At scoping level, the investment 

risk may be relatively small but it is obviously 

undesirable to expend further funds on something that 

has no chance of being economically viable. 

Scoping studies typically have an estimation accuracy 

of +/- 30%. A scoping study determines whether 

the expense of a full prefeasibility study is warranted. 

Prefeasibility Study (PFS). A prefeasibility study is a 

comprehensive study whose main features are: 

• Completion of a geological assessment and resource 

estimate, which will quantify the tonnage and quality 

of the mineral deposit. The resource will be quan- 

Feasibility Studies, Geological Assessments, Resource Estimation 


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6 

Figure 4 - Mining Project Life Cycle 

tified according to recognised international resource 

reporting standards (see “The Relevance of International 

Reporting Codes and Their Practical Application 

to Resource Estimation”, in this publication); 

• Production of a geological model to be used as a basis 

for mine design (see “Geological Assessment and 

Resource Estimation of Coal Deposits and Their Influence 

on Mine Design” in this publication); 

• Investigation of the most suitable scale of operation; 

• Conducting a technical options study (on all mining, 

processing & civil engineering options); 

• Following the options study, selection of the best solution 

taken through to the definitive feasibility study 

(DFS) stage for detailed evaluation; 

• Completion of preliminary studies on geotechnical, environmental, 

and infrastructure requirements; 

• Completion of bench scale metallurgical tests and 

preliminary process design; 

• Estimation of cost based on factored or comparative 

prices; and 

• An assessment of the environmental and social fatal 

flaws. The environmental impact assessment (EIA) 

and the social impact assessment (SIA) process can 

be initiated at this stage. 

Prefeasibility studies typically have an estimation 

accuracy of +/- 20% to 25%. A prefeasibility study 

will determine whether or not to proceed with a definitive 

feasibility study. These studies are typically carried 

out by a third-party mining consultant (such as Parsons 

Brinckerhoff). However, if the expertise is available and 

independence is not an issue then they can be completed 

by in-house teams. 

Network 

Definitive Feasibility Study. The definitive feasibility 

study, typically based on the most attractive alternative 

for the project as previously determined, is the most 

detailed and should remove all significant uncertainties 

and present the relevant information with back up material 

in a concise and accessible way. The definitive feasibility 

study has several objectives: 

• To demonstrate with reasonable confidence that the 

project can be constructed and operated in a technically 

sound and economically viable manner; 

• To provide a basis for detailed design and construction; 

• To enable finance for the project to be raised from 

banks or other sources; and 

• To provide the basis for permitting and regulatory approvals. 

The definitive feasibility study typically has an 

estimation accuracy of +/-10 to 15%. 

The Importance of Getting it Right 

The early stages of the feasibility study process are important 

– the scoping and prefeasibility study levels are 

when design options can be flexed and tested. It is acceptable 

for scoping studies to be based on very limited 

information or speculative assumptions in the absence 

of hard data. The study is directed at the potential of 

the property and the study should err on the side of 

optimism – getting it wrong at this stage will not be as 

costly as rejecting an otherwise economically viable project 

due to being too risk adverse. 

Influence on the outcome diminishes once the 

project has reached the definitive feasibility level, the 

options and design should be more or less fixed, with

Figure 5 - Leverage of Early Work 

only specifics to be decided upon, as Figure 5 illustrates. 

It is also important to remember that each 

stage of the process adds value and that the study process 

needs to be of the highest quality to deliver maxi- 

Figure 6 - Impact of Study Phases on Project Value 

mum value (see Figure 6). If something is missed or an 

optimal option is not investigated or selected, it is very 

difficult to realise the true value of the project. 

Common Pitfalls and Misconceptions 

The most common pitfalls and misconceptions that lead to 

the failure or under-performance of a feasibility study are: 

1. “Bankable” does not mean bankable. It is best to 

avoid using the emotionally charged term ‘bankable’ 

feasibility study due to the misconceptions surrounding 

the word. Many clients believe that a ‘bankable’ 

document is just that – a document that can be taken 

to a bank in exchange for cash. Unfortunately, this is 

not the case and the term is misleading. At the very 

least, the lender will require its own due diligence and 

internal review before any investment. Then the project, 

albeit economically feasible, may not meet the 

Network 

lenders criteria for investment. 

For this reason, 

Parsons Brinckerhoff uses 

the term ‘definitive’ feasibility 

study, which should 

achieve the minimum criteria 

to facilitate the procurement 

of bank debt. 

2. Failure to integrate 

study disciplines. Having 

study contributors operating 

in isolation can lead 

to failure to identify fatal 

flaws or material issues. 

Parsons Brinckerhoff acts as overall project manager 

for the studies we are involved in and completes 75% 

in-house which helps to mitigate this issue. 

3. Failure to peer review the document. Failure to conduct 

a thorough peer review 

with ‘outsiders’ eyes 

leads to groupthink and 

an unhealthy emotional 

attachment to a project. 

4. Failure to involve all 

stakeholders. A comprehensive 

stakeholder analysis 

and communication 

plan is required to ensure 

all stakeholders are kept 

‘in the loop’. This ensures 

that misunderstandings 

and late scope changes 

are kept to a minimum. 

5. Should be ‘Fit for Purpose’. Studies all too often concentrate 

time and effort (and, importantly, money) on 

relatively unimportant technical issues (e.g., overanalysing 

preliminary data) at the expense of critical 

business and project delivery issues. 

6. Poor housekeeping. Geological interpretation is the 

basis of any study. A rigorous QA/QC must be carried 

out on the geological database before undertaking a 

project or design to understand the validity/state of 

the data. 

7. A feasibility study is not a guarantee of success. A 

feasibility study is just that – a study to determine 

whether or not a project is feasible from a technical, 

regulatory and financial point of view. Just because 

a project is undergoing a feasibility study does not 

mean that the results will be positive. 

8. Poor continuity. All too often, the handover from one 

study to another (for example, from prefeasibility study 



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Parsons Brinckerhoff Case Study 

In 2009, Parsons Brinckerhoff was commissioned 

to undertake both pre-feasibility (+/-25%) and definitive 

feasibility (+/-10%) studies on a coal resource 

in the Waterberg area of South Africa, located 5km 

to the west of the Grootegeluk Colliery and the Medupi 

Power Station. This was a large project with production 

rates of up to 15 million tonnes per annum 

(Mtpa) of run-of-mine (ROM) coal yielding 10Mtpa of 

saleable thermal coal over a 21 year mine life. 

The studies included a detailed investigation 

of the requirements for on-site and off-site infrastructure, 

mine design and scheduling, engineering, coal 

handling and preparation, hydrogeology and geotechnical 

engineering & personnel and equipment. This 

is an example of a large multi-disciplinary project 

with several contributors with integration of inputs 

between the various disciplines key to the success. 

The client was a joint venture between two 

companies – one based in South Africa and one in 

Australia. As the project was being managed out of 

the UK, effective communication and engaging the 

various stakeholders was essential. 

to definitive feasibility study) is not as effective as it 

should be, which leads to ineffective knowledge transfer. 

This could result in reduced value in the original 

study, missing a key conclusion or unnecessary re-work. 

Innovation within the feasibility study 

process 

Innovation within the feasibility study process is interlinked 

with innovation within the mining industry as a 

whole. Assuming that a feasibility study has to assess 

three main criteria - technical, regulatory and economic 

- possible innovations in these categories, which will 

change the way projects are assessed or the assessment 

itself, are shown below: 

1. Technical. This category covers a wide range: resource 

identification and verification, mineral extraction, processing, 

haulage technology, amongst many others. 

Once the resource in the ground has been verified, 

the way it is extracted, processed and delivered to 

the market determines whether a project is feasible 

or not. Advances in technology - such as automated 

mining equipment or x-ray sorting processing methods 

- can result in a previously un-feasible project becoming 

viable and keeping on top of new technology 

is an integral part of the feasibility process. 

2. Regulatory. There is a growing movement toward sus- 

Network 

tainable development and social responsibility in the 

industry. Guidelines now require compliance. Expect 

environmental controls to get tighter in the future 

and compliance will play a major role in the feasibility 

study process, even more so than now. Additionally, 

government intervention, such as high taxes or nationalisation, 

especially in developing countries, may 

have a big impact on whether a project could be considered 

feasible or not. 

3. Financial. Because mining is a mature industry, nearly 

all of the extremely attractive projects - the ‘low lying 

fruit’ - have been developed, and most mining studies 

are of a marginal nature when assessed using traditional 

feasibility techniques. The risk is, of course, 

that the assessment is too cautious and focused on 

the downside, which means that good projects are 

potentially being rejected at the feasibility stage. 

The traditional valuation technique for a feasibility 

study is a discounted cash-flow (DCF) model which 

is well understood and deals with costs and revenue. An 

alternative method of valuing a mining project that could 

be adopted is the real options analysis (ROA) method. 

The ROA method places a value on ‘real options’ when 

undertaking certain true-to-life business decisions, such 

as deferring, abandoning, expanding, staging, or contracting 

a capital investment project. Although there is 

some similarity between modelling real options and financial 

options, ROA takes into account uncertainty surrounding 

the parameters that determine the value of the 

project and applies a value to the company’s ability to 

respond to them. On the whole, ROA valuation methods 

are seen as more ‘optimistic’ than classic DCF methods 

and could be usefully employed when assessing more 

marginal studies, although the risk involved will also 

need to be properly assessed and communicated. 

Marco Maestri is a principal mining engineer whose expertise 

lies in feasibility studies, project management, CAD mine design 

& scheduling and financial analysis. He is currently the project 

manager for a pre-feasibility project in the Limpopo region of 

South Africa and has recently managed a successful coal definitive 

feasibility study in the same region. He also has experience 

managing and providing technical input to feasibility projects in 

Europe and Australia. 

References 

• The Role of Feasibility Studies in Mining Ventures (Nethery, 

2003) 

• The Use and Abuse of Feasibility Studies (Mackenzie & 

Cusworth, 2007) 

• Mine Investment Analysis (Gentry & O’Neil, 1984)

Network 

Geological Assessment and Resource 

estimation of Coal Deposits and Their 

Influence on Mine Design 

by Aidan Parkes, Manchester, UK, +44 (0)161-200-5178, aidan.parkes@pbworld.com; Samuel Moorhouse, Manchester, 

UK, +44 (0)1612-200-9847, sam.moorhouse@pbworld.com; and Jonathan O’Dell, Manchester, UK, +44 (0)1612- 

200-2216, jonathan.odell@pbworld.com 

Parsons Brinckerhoff has undertaken a number of feasibility 

studies for coal deposits in sub-Saharan Africa 

(see “Mining Feasibility Studies - An Outline of the Technical 

Input, Requirements and Purpose of Mining Feasibility 

Studies”, this publication), to determine the economic 

viability of extracting these potential resources. 

The feasibility process and reporting of mineral deposits 

is governed by a number of international codes, and 

associated guidelines (see “The Relevance of International 

Reporting Codes and Their Practical Application to 

Resource Estimation”, this publication). 

An important aspect of the feasibility study 

process is the undertaking of a geological assessment 

and resource estimation, which will quantify the tonnage 

and quality of the mineral deposit. To do this the 

Competent Person (CP) must demonstrate an understanding 

of the geology of the deposit, in particular its 

extent, quantity and quality, as well as any associated 

geological structures. The resource can then be classified 

based on the CP’s confidence of the available data, 

and quantified according to international resource reporting 

codes. 

The geological assessment and resource estimation 

process is a prerequisite for robust appraisal 

of mining potential including mine design, planning and 

scheduling (Figure 1). This article summarises the key 

stages in the assessment process and highlights some 

novel approaches employed by Parsons Brinckerhoff geologists 

during the various feasibility studies. 

Stage 1: Data selection and audit 

The goal of the selection and audit process is to produce 

a robust, finalised database, comprising suitable 

spatial, geological and quality data (Table 1), upon which 

a geological model can then be constructed. 

Data selection involves a detailed assessment 

of the data made available to Parsons Brinckerhoff by its 

clients. The CP will identify reliable information, discarding 

that without a verifiable audit trail. 

Once the finalised dataset has been selected, a 

thorough audit process is performed through systematic 

and comprehensive validation of raw data, to ensure: 

• Borehole locations and license boundaries use the 

same co-ordinate system; 

• Stratigraphical depths are consistent between handwritten, 

geophysical logs and sample intervals; 

• Coal analyses match laboratory certificate sheets, 

and are accurate; and 

• Statistical analysis of laboratory results is performed 

to identify any abnormal values. 

In a recent study, it was found that sampling 

had been completed on an ad-hoc basis instead of the 

recommended approach of using depths that relate 

directly to lithology, as per the geophysical logs. This 

resulted in the mismatching of drilling, lithology, and 

sample depths between boreholes, making it necessary 

to adjust sample depths to ensure compatibility 

with the geophysical logs. 

Data quality issues were overcome by using 

the percentage of core recovered during drilling (“core 

recovery”) as a direct indicator of data reliability. Because 

sections of poor core recovery (often relating 

to minor faulting) lacked adequate sample data and 

subsequent analysis, they were deleted from the database. 

Here, where insufficient analytical data was 

unavailable, resources were downgraded during classification, 

and greater geological losses were applied 

(Stage 3 below). This methodology allowed integration 

of the core recovery, sample, and lithology datasets 

despite their apparent depth differences. 



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DATA TYPE 

Spatial 

Geological 

Quality 

Network 

Figure 1 – The four key stages in the geological assessment and resource estimation process 

Survey of borehole locations 

Digital terrain models 

Boreholes 

Geophysical logs 

Outcrop 

Maps 

Aerial geophysics 

Seismic surveys 

Core recovery 

Coal samples 

Table 1 – Components of the geological database 

SOURCES RATIONALE 

Enables the spatial context of geological and 

quality data to be established 

Topographical surfaces provide physical constraint on the extent 

of coal seams and are used as an elevation reference surface 

Provide the basic framework of coal seam 

positions and dimensions 

Laboratory analysis of coal samples (of different wash fractions) 

including raw density, calori�c value, yield, coking properties and 

percent of ash, moisture and sulfur, phosphorous, etc.

Stage 2: Geological modelling 

Construction of a geological model is fundamental to modern 

resource estimation, enabling the data collected for a 

deposit to be visualised, and its extent and quality to be 

reliably and accurately quantified. Furthermore, the model 

can then be submitted to mining engineers as a basis for 

subsequent mine design. 

Parsons Brinckerhoff uses in-house geological 

modelling and resource estimation software 1 to produce 

accurate 3-D models of deposits. Data selected during the 

audit process (Stage 1) is imported into the software’s internal 

database management system 2 . Coal deposits are 

then modelled using the integrated stratigraphical modelling 

process (ISM) designed specifically for stratiform deposits 

(where the deposit forms a layer or layers within the 

stratigraphical sequence). The ISM approach comprises 5 

key steps (Table 2). 

Steps Purpose 

1: Data Validation 

Testing the database for 

potential sources of error 

2: Interpolation of 

drill hole data 

3: Modelling of stratigraphy 

4: Compositing and modelling 

of qualities 

5: Construction of Horizon 

Adaptive Rectangular Prism 

(HARP) block model 

Table 2 - The basic steps of geological modelling 

Interpolation of geological 

data between boreholes 

Generation of a stack of 3-D 

surfaces for the roof (top) and 

�oor (bottom) of each 

geographical unit. 

Compositing of analytical data 

for each geological unit to 

produce a single range of coal 

qualities, which are then 

extrapolated for the site. 

Construction of a block 

model. Individual blocks 

contain all geological and 

quality data for the 3-D space 

it represents. Igneous 

intrusions and faults can be 

incorporated into the block 

model 

In a recent Parsons Brinckerhoff study, the block 

model produced in the above process contained approximately 

25,000 individual blocks for each coal seam and 

each block contained specific calculated quality parameters. 

This block model was then used as a basis for resource 

assessment and deductions made for other fac- 

Network 

1 Parsons Brinckerhoff global mining uses Maptek Vulcan® software to undertake geological modelling. 

2 Vulcan® uses Maptek Isis® database management system 

tors, such as faulting, weathering and igneous intrusions, 

as described below. 

The software is also capable of modelling orebodies 

(Figure 2). In a recent study, this methodology was 

used to digitise a series of dolerite intrusions (a basic igneous 

rock type) that were identified within a coal deposit using 

lithological and geophysical logs, and geological maps. 

Parsons Brinckerhoff geologists digitised the 

3-D shape of the intrusion by producing a series of polygons 

based upon borehole (vertical thickness of the intrusion) 

and outcrop data (the intrusion’s areal extent at 

surface). The polygons formed the frame for subsequent 

generation of a solid triangulation (a shape formed by 

numerous triangles). 

Furthermore, the methodology was also utilised 

to model the effects and extent of burning associated 

with the intrusion of hot magma next to the coal, enabling 

burnt coal to be quantified and classified differently. 

To do this the polygons produced were expanded 

by a distance determined from a study of the sample 

analyses, and a second triangulation produced. Once 

produced, the triangulations (3-D shapes) are incorporated 

into the block model, allowing an assessment of 

the quantity of the coal affected by the intrusion(s). 

Figure 2 – Modelling of ore-bodies and dolerite intrusions is performed 

using wire-frame / triangulation solids 

Stage 3: Resource classification and estimation 

Development of the block model enables accurate estimation 

of the resource, incorporating dimensions, tonnages 

and coal quality properties that vary spatially. 

The relative confidence of specific areas of the 

deposit is measured using a formal classification procedure 

as set out in existing international codes and 



11



12 

guidelines. Parsons Brinckerhoff widely uses the Australasian 

JORC Code although a number of codes exist 

internationally (see “The Relevance of International 

Reporting Codes and Their Practical Application to Resource 

Estimation”, this publication). 

Geological confidence is assessed in terms of 

quantity and quality of available data and the complexity of 

the structure of the deposit. Coal is formally categorised 

into different classifications: Measured, Indicated and Inferred 

categories (of decreasing confidence). The categories 

are each defined by pre-existing criteria and specific 

parameters governed by the codes. 

Stage 4: Influence on mine design 

Geological assessment and resource estimation are required 

prior to the mine design phase of feasibility studies, 

as they allow: 

• Production of a 3-D geological model that enables the 

properties of the mineral deposit to be assessed spatially; 

• Classification of the resource into Measured, Indicated 

and Inferred status. This determines the confidence attributed 

to the resource and whether there is scope for 

subsequent mine design to be implemented. Only Measured 

and Indicated resources (regarded as more reliable) 

may be considered as reserves; 

• Input of coal production/quality data into mineral processing 

software by mine designers for coal handling 

and preparation plant (CHPP) design; and 

• Understanding of the coal products that can be produced 

with specific characteristics that match the client’s requirements, 

as the block model can be used to output 

tonnages based on specific quality parameters. 

Risk Profiles and Management 

There are a number of potential risks that may affect a resource 

statement, including issues with data often related 

to poor practice during collection and analysis, geological 

uncertainty (i.e., continuity of the geology between boreholes) 

and the modelling process. 

To ensure that risk is kept to a minimum and that 

all estimates are similar to one another, a number of international 

reporting codes and guidelines exist. These codes 

and guidelines ensure that all geological assessments and 

resource estimates follow the same basic principles and 

provide details on best practices, including the spacing of 

boreholes for resource classification to the amount of core 

recovered during exploration drilling. 

The most commonly used international codes 

and guidelines are: the South African Code for Reporting 

of Exploration Results, Mineral Resources and Mineral 

Reserves (SAMREC); the Australasian Joint Ore Reserves 

Network 

Committee (JORC) and The Code for Reporting of Mineral 

Resources and Ore Reserves (the JORC Code); and, the 

Canadian National Instrument 43-101: Standards of Disclosure 

for Mineral Projects and the CIM Definitions Standard 

(NI-43-101). 

Parsons Brinckerhoff’s use of a staged approach 

to the assessment and resource estimation process 

is also an important control for reducing risk, enabling 

risks to be identified and managed at each stage 

of the process. 

Summary and Conclusions 

Geological assessments and resource models are an integral 

part of a feasibility study. When conducted by experienced 

and qualified geologists (Competent Persons) 

and in line with international reporting codes, they provide 

a technically accurate and certified resource assessment 

valued by the client. Resource reports are important because 

they: 

• Provide detailed assessments of the dimensions, tonnages 

and quality of a mineral deposit; 

• Serve as a precursor to further studies, estimating the 

value of a deposit and thus the likelihood of a projects 

financial reliability (i.e., the feasibility study); 

• Contain detailed geological information, preferably as 

a geological model, required for mine design, scheduling 

and the drawing up of potential mineral processing 

plants (e.g., CHPP); and 

• Are valuable as a stand-alone document (e.g., as a Competent 

Person’s Report) as they are recognised internationally, 

possibly assisting with client requirements, such 

as: raising of funds for further exploration; securing capital 

to begin extracting the deposit; providing the legal requirements 

necessary for listing associated companies 

on international stock exchanges/financial markets. 

Aidan Parkes is a mining geologist and has recently been involved 

in resource assessments for pre-feasibility and feasibility studies, 

constructing geological models for coal deposits in southern Africa. 

He has a BSc (Hons) in earth systems science and a PhD in glacial 

geomorphology. 

Sam Moorhouse is a senior geologist specialising in resource estimations 

for coal deposits in southern Africa and sedimentary deposits 

in China. He holds a MESci (Hons) in earth sciences from the University 

of Oxford and is a Fellow of the Geological Society of London. 

Jonathan O’Dell is chief geologist for Parsons Brinckerhoff and a 

Competent Person in coal geology. He has a broad range of experience 

working on coal deposits in the UK, Indonesia, South Africa, 

Bangladesh and Russia.

Network 

The Relevance of International Reporting 

Codes and Their Practical Application to 

Resource estimation 

by Samuel Moorhouse, Manchester, UK, +44 (0)161-200-9847 sam.moorhouse@pbworld.com; and 

Aidan Parkes, Manchester, UK, +44 (0)161-200-5178 aidan.parkes@pbworld.com 

Parsons Brinckerhoff undertakes resource assessments 

of mineral assets and commodities around the 

world. This article explains the methodology for estimating 

resources in compliance with international reporting 

codes and the protocols which must be adhered to. 

Abundant literature exists which discusses the nuances 

of the different reporting codes and guidelines; this paper 

summarises how they can be practically applied, 

with specific references to coal. 

The purpose of international reporting codes 

Reporting codes are internationally recognised documents 

that afford a standardised framework on which 

mineral resource estimates can be publically reported. 

To the geologist they also provide a mandatory system 

for resource classification; a method for separating resources 

into different categories of varying confidence 

levels. The presence of these guidelines affords comfort 

to asset holders and potential investors in that the reputation 

of individuals and companies are under scrutiny 

when they produce reports. Today, 

any public resource report 

must adhere to these codes. 

Where it all began 

In 1969 the share prices of 

Australian mining company 

Poseidon NL skyrocketed as 

the potential of their recently 

identified nickel (Ni) deposit 

was made public. This was initiated 

by a high Ni concentration 

quoted by local geological consultants, 

Burrill & Associates, 

and further compounded by the 

extraordinarily high Ni price, at 

the time induced by the Vietnam 

War. These events led to the infamous Poseidon Bubble, 

which eventually burst as the Ni concentration was found 

to be considerably lower than the value quoted, but only 

after Poseidon’s share price had climbed to $280 from 

$0.03. Later, in Indonesia, the Canadian Bre-X owned 

gold deposit was uncovered as a fraud after shavings of 

gold jewellery were identified in the samples, losing investors 

billions of dollars in the process. The economic 

repercussions of these events signalled the change in 

mining legislation and marked the inception of the reporting 

codes we use today. 

Detailed resource definitions accompany the 

codes in their respective guidelines, both of which vary 

between countries. Each set of guidelines relates to the 

dominant deposits and specific stratigraphical sequences 

endemic within that country. Whilst the language 

differs slightly, the principles behind the codes are the 

same (see Figure 1). 

A process of aligning international reporting 

codes is currently underway, and is being developed by 

Country Common abbreviation Reporting Code Coal Reporting Guideline 

Australia 

South Africa 

Canada 

Europe 

2004 JORC Code 

SAMREC 

NI 43-101 

PERC 2008 

The Australasian Code for Reporting of 

Exploration Results, Mineral Resources 

and Ore Reserves, by the Australasian 

Joint Ore Reserves Committee 

The South African Code for the 

Reporting of Exploration Results, 

Mineral Resources and Mineral 

Reserves 

Figure 1 – Components of the geological database 

National Instrument 43-101: Standards 

of Disclosure for Mineral Projects and 

the CIM De�nitions Standard 

Pan-European Code For Reporting of 

Exploration Results, Mineral Resources 

and Reserves 

Australian Guidelines for 

Estimating and Reporting of 

Inventory Coal, Coal Resources 

and Coal Reserves, 2003 

SANS 10320:2004: South African 

guide to the systematic 

evaluation of coal Resources and 

coal Reserves 

Geological Survey of Canada 

Paper 88-21: A Standardized 

Coal Resource/Reserve 

Reporting System for Canada 

Reporting for Exploration 

Results, Resources and 

Reserves for Coal 



13



14 

the Committee for Mineral Reserves International Reporting 

Standards (CRIRSCO). The current members 

and their associated standards are Australasia (JORC), 

South Africa (SAMREC), Canada (CIM), Europe (PERC), 

United States (SME), Chile (Comisión Minera de Chile) 

and very recently Russia (NAEN). 

Achieving code compliancy 

Here, JORC Guidelines for Coal are used as illustration. 

The guidelines stipulate that resources are classified 

and reported according to three basic principles that 

must be observed: 

Transparency: the provision of clear, unambiguous 

information. 

Materiality: all relevant data is presented to allow 

reasoned and balanced conclusions to be made by 

the reader. 

Competence: the report is based on work undertaken 

by the Competent Person (CP); an individual of recent 

relevant experience (typically five years) in a specific 

commodity, that is suitably qualified and who abides 

by an enforceable professional code of ethics (i.e. is a 

member of a recognisable professional body). 

The definition of a resource 

Resources simply refer to a mineral deposit that 

might, under assumed and justifiable technical and 

economic conditions, become economically extractable. 

The geologists’ role is to identify and assess 

these resources. 

The commonly quoted and often cited relationship 

between exploration results, resources and reserves (extract 

from 2004 JORC Code) is shown in Figure 2. 

Network 

Figure 2- General relationship between exploration results, mineral Resources and ore Reserves 

Resource classification 

Resources are sub-divided into different classifications, 

providing a platform on which the geologist can 

convey the varying levels of confidence across the deposit. 

Practically this translates to: the lower the quantity 

and/or quality of data, the lower the confidence, 

the lower the classification and the greater the losses 

applied to that region of the resource. In the JORC 

Code, a resource is classified into Measured, Indicated 

or Inferred categories. 

Progressing beyond resource to a reserve involves 

application of more rigorous and detailed criteria, 

“modifying factors”, which are relevant at that time. A 

reserve is deemed economically mineable and can only 

be generated from Measured and Indicated classifications. 

Reserves require development of a mine plan and 

schedules in further pre-feasibility and feasibility studies 

(see “Mining Feasibility Studies - An Outline of the 

Technical Input, Requirements and Purpose of Mining 

Feasibility Studies”, this publication). 

Resource classification is realised through the 

application of points of observation (PoOs) which are 

intersections of strata (i.e., coal), at known locations, 

that provide information allowing the presence of a 

potential resource to be unambiguously determined. 

Practically, this denotes the requirement of obtaining 

sufficient quantity and quality of data to confidently determine 

the presence and the characteristics of a mineral 

deposit, primarily in the form of drilling boreholes 

and logging, sampling and analysing the core extracted 

from the boreholes. 

Quantity of information: Is the coal 

continuous? 

An increased density of PoOs within a given 3-dimensional 

space exudes greater confidence in the deposit. 

To achieve Measured status, a maximum 

borehole spacing of 500 metres 

is allowed, i.e., boreholes cannot 

be greater than this distance 

apart. Indicated status calls for 1km 

spacing, and for Inferred status up to 

4km is permitted. 

The purpose of these devised 

borehole locations are to satisfy 

the concept of continuity. Inferred 

and Indicated categories refer to coal 

where lateral continuity in the deposit 

can only be assumed but not verified. 

Measured coal has enough data 

available to confirm continuity.

Quality of information: Is the data robust? 

Data quality is investigated by thoroughly following the 

audit trail. The primary examples of these parameters 

include, but are not restricted to: 

• Borehole co-ordinates surveyed by reputable professionals; 

• Exploration boreholes drilled with a substantial amount 

of core recovered (normally >95%); 

• Signed handwritten lithological logs from the field geologist; 

• Geophysical logs; 

• Adequate quantity of coal sampled; and 

• Coal analysis carried out by an accredited laboratory. 

In many cases much of the above data can be 

absent. It is the role of the Competent Person to best 

decipher this information, accurately assess its reliability 

and determine how the resource should be classified. 

With lower certainty, greater losses are applied 

and the final quoted tonnage is lowered (see Figure 3). 

RESOURCE 

Low level of 

confidence 

Reasonable 

level of 

confidence 

High level of 

confidence 

Inferred 

Indicated 

Measured 

Figure 3 – Geological losses and classification 

20% deduction to 

Resource tonnage 





The deductions applied reflect the overall confidence 

in the deposit but are typically around 20-25% for 

the lowest levels, and relate to the quality and quantity 

of data available but also the assurance in the lateral 

continuity of the deposit between points of observation. 

Conclusions 

• Codes and guidelines are different. Codes refer to how 

the resource should be reported. Guidelines provide 

a “manual” for the geologist to follow, devised and 

refined based on the experience and work of many 

professionals over a number of years. 

• Guidelines are useful because they provide tangible 

requirements that resource exploration must satisfy. 

They help to justify the decisions made by the geologist 

during resource classification. 

• The geologist must be a Competent Person (CP). Previous 

experience of a deposit is vital for assessment 

and classification. 

• Whilst it can be easy to strictly follow guidelines from 

Network 

the outset, it can be useful for the CP to subjectively 

examine the data as a whole. By exercising their knowledge, 

experience and discretion, CPs can ask themselves: 

“How much do we really know about this deposit?” 

Applying a more generalised outlook to the data 

can help to move away from guideline specifics (such 

as precise borehole spacings and core recoveries). 

• Additional data, such as seismic and aerial geophysical 

surveys or geostatistical analysis, cannot be translated 

to specific PoOs but can still aid the CP in deducing 

that the mineral in question is laterally continuous. 

• Observing all aspects of the data together can lead 

to advantageous balancing of guideline “rules” (e.g., 

abundant and wholly reliable data could permit the acceptance 

of wider borehole spacings. Conversely, absent 

information and complex geology could result in 

only closely-spaced boreholes being allowed). 

• It is important that the involvement of professionally 

qualified and experienced practitioners is sought at 

the very early stages of projects. This can optimize 

the approach to assessing a deposit and can significantly 

reduce costs. 

Future outlook 

Reporting codes and their guidelines have developed 

significantly since their inception in the 1970s. The result 

is a series of well-established documents familiar 

within the geological and mining community. However, 

this process is still ongoing, with the terminology of the 

different documentation in a constant process of being 

rewritten and updated. For example, a current topic of 

discussion is the definition of a resource, which JORC 

calls “a concentration or occurrence of material of intrinsic 

economic interest ... (of which) there are reasonable 

prospects for eventual economic extraction”. 

The clarity of this statement is under scrutiny due to 

the ambiguity associated with the term “reasonable 

prospects for eventual economic extraction”. The initial 

assessment of a deposit requires a judgement to 

be made by the CP with respect to the techno-economic 

factors likely to influence the prospect of economic 

extraction. These criteria are applied fully during conversion 

of resources to reserves through application 

of modifying factors (as discussed previously) but nevertheless 

an initial consideration of the extractability 

of a resource must be made early in the assessment 

process. Opinion may differ markedly between CPs 

and their interpretation of the ease of extraction of the 

mineral and knowledge of local mineral markets. JORC 

has recently (October 2011) called for views on such 

matters to be submitted by the mining community. Fur- 



15



16 

thermore, the Australian Securities Exchange is starting 

to diverge from JORC by developing its own code 

similar to the Canadian principles, which were set up 

by the Canadian Securities Administrators and therefore 

require an increased input from lawyers (instead 

of simply technically qualified persons) when writing or 

publishing public reports. 

Reporting codes and guidelines continue to 

evolve, with terminology, definitions and requirements 

being updated every few years. As the mining sector becomes 

a more global entity, new codes are being developed 

in emerging mineral economies, with the notable 

acceptance of the Russian NAEN code by CRIRSCO as 

recently as November 2011. Parsons Brinckerhoff con- 

Network 

tinues to flourish in this evolving environment utilising 

codes and guidelines from all over the world in their mineral 

assessments. 

Sam Moorhouse is a senior geologist specialising in resource 

estimations for coal deposits in southern Africa and sedimentary 

deposits in China. He holds a MESci (Hons) in earth sciences 

from the University of Oxford and is a Fellow of the Geological 

Society of London. 

Aidan Parkes is a mining geologist and has recently been involved 

in resource assessments for pre-feasibility and feasibility 

studies, constructing geological models for coal deposits in 

southern Africa. He has a BSc (Hons) in earth systems science 

and a PhD in glacial geomorphology.

Network 

Innovating a Better environment Through 

a Sustainable Approach to Mining 

by Ben Hall, Brisbane, Australia +61 7 3854 6706, be1hall@pb.com.au 

Parsons Brinckerhoff has been in the fortunate position 

of assisting a client, Sirius Minerals, with an innovative integration 

of engineering solutions which presents an environmentally 

and commercially positive approach to several 

major environmental issues currently being faced by 

Queensland, Australia. 

Sirius Minerals approached Parsons Brinckerhoff 

to undertake an input study for the requirements of a solution 

potash mine in the middle of Queensland. Preliminary 

information gathered during some drilling operations indicated 

that the size of the salt member containing the potash is 

several tens of cubic kilometres, which is currently Australia’s 

largest documented salt deposit. With potash prices on 

the increase, this deposit is raising a fair degree of interest. 

The mining technique known as solution mining 

appears to be the most suitable approach based on the 

geology of the deposit. The process requires the pumping of 

large volumes of water into the salt member, the salt is then 

dissolved into the water and pumped back to the surface. 

The salt is processed out and the water is returned to the 

mining process. Herein lay the first major consideration 

for the project – sourcing water in 

an environmentally responsible manner while 

maintaining strong project economics. 

Sourcing water 

The centre of Queensland is quite hot and 

dry with evaporation rates over 2.5m (8.2ft) 

per year (see Figure 1). 

Sirius Minerals asked Parsons Brinckerhoff 

to consider a solution mining operation 

that has the potential to extract over 5 million 

tonnes per year of potash salt. Solution mining 

at that scale of operation would require a 

water supply in the order of 20-30 gigalitres 

per annum. At the location of the salt member, 

there are no major waterways or dams. 

While there are several traditional options for 

obtaining water in such a situation, they are 

either costly or have potential environmental 

consequences, such as lowering the water table or diverting 

natural drainage. Therefore the first challenge was to 

identify a large volume of water that would be inexpensive 

and environmentally neutral or positive. 

Coal seam gas water 

The coal seam gas (CSG) industry in Queensland is providing 

promising economic opportunity and is expanding 

rapidly. However, the process of extracting gas from coal 

seams also generates a high volume of water. This water 

is saline and is a significant environmental issue. Public 

outcry against the salt deposits left by evaporation ponds 

(used to dispose of large amounts of water in the preliminary 

stages of the CSG industry) led to the Department 

of Environment and Resource Management issuing 

a moratorium in early 2011 on all new evaporation ponds, 

leaving the CSG producers to find an alternative way to 

deal with these vast volumes of water. The cost of dealing 

with the waste water and its salt content is currently 

estimated at over 2 billion dollars and likely to increase. 

Figure 1 – Evaporation rates for Australia (source: Australian Bureau of Meteorology) 



17



18 

The Parsons Brinckerhoff planning team working 

on the background study suggested that there may be a 

synergy between the coal seam gas producers, for whom 

the water is a waste product, and our client, Sirius Minerals. 

Sirius Minerals, who by the nature of solution mining 

of salts is already expert in the processing of salt containing 

water, was very receptive to the idea and this suggestion 

immediately sparked a flood of creative ideas. It 

was proposed that the coal seam gas produced water be 

pumped to central Queensland via a 500km pipeline and 

brought to the project site where it could be treated and 

used as process water. 

Power supply 

The second major consideration for the project is finding sufficient 

power for the operation of the solution mining, ideally 

drawing on renewable resources. Queensland already has 

a shortfall in reserve energy generation capacity, which has 

been predicted to grow to between 341 and 779 megawatts 

by 2013-2014. 1 As such, drawing hundreds of megawatts 

of capacity from the grid is not likely to be a viable option. 

For this reason many regional miners build their own power 

infrastructure, using either coal or natural gas. Carbon considerations 

and rising natural gas prices have increased the 

costs associated with coal and gas power and, therefore, 

renewable options are attracting more attention. 

Solar power is now a viable and cost effective 

option for Queensland due to the many days of sunshine 

prevalent in the region, but without a storage solution solar 

power cannot supply the consistent power needed for 

24/7 mining operations. However, given the suitable climate, 

large amounts of available land and the significant 

source of saline water in the CSG wastewater, another 

technology presents itself as a solution. 

Solar thermal pond power generation using Organic 

Rankine Cycle power plants is a technology that has proved 

effective in areas where there is high solar exposure and 

large areas of flat land, one of the most well known power 

plants of this type being the Bet Ha-Arava 5MW pond 

in Israel. The solar exposure in central Queensland is very 

high, and the terrain is quite flat. High levels of salt are also 

required, and CSG water is saline. Based on the technology 

used in Israel, a 20 hectare solar thermal pond can 

generate 5MW of power at the minimum and, with recent 

advances, potentially up to 20% more. 

A site layout has been proposed consisting of 24 

solar ponds with their associated evaporation ponds, and a 

collection dam. This arrangement would be able to receive 

1 http://www.aemo.com.au/planning/0410-0088.pdf 

Network 

suitable volumes of water produced from CSG and would 

allow for a minimum of 120MW of power generation. The 

layout is expandable, such that more ponds could be built 

to allow for greater power generation capacity. This might 

be used to run additional industrial operations or to provide 

cheap, baseload renewable power to the Queensland 

electricity grid. 

excess salt 

During the life cycle of a solar pond, water is evaporated 

from the surface of the pond and the salt remains. The salinity 

within the pond can get to levels that reduce the efficiency 

of the power generation. Periodically, highly saline 

water is removed from the pond and placed into evaporation 

ponds where the salt will crystallize and then require 

disposal. Disposal of this salt is presently a highly sensitive 

environmental issue in Queensland and the project needed 

a comprehensive and politically acceptable way of dealing 

with the generated salt. 

A potash mine also produces large volumes of sodium 

chloride (NaCl) as a by-product. This is often re-injected 

back into the mine, although it can also be further processed 

into other commercial salt products. One such process is 

the chlor-alkali process, which converts sodium chloride into 

caustic soda for direct sale into the Australian market. 

The power produced by the solar ponds would 

be enough to run a small scale chlor-alkali plant. Between 

the solar ponds and the potash mine, a significant 

quantity of high purity (ideal for chlor-alkali) sodium 

chloride will be produced. This would be sent to the 

chlor-alkali plant for processing, and the lower purity 

NaCl from both the ponds and the potash mine would 

be re-injected back into the mine. 

The concept design process has been closely 

integrated with Sirius Minerals who is very receptive of, 

and indeed generates, new and innovative ideas. By combining 

knowledge from across the breadth of Parsons 

Brinckerhoff, and including alternative technologies and 

approaches, this project shows the potential to address 

major environmental challenges as part of the design of 

mining and process industries. 

For more information on this project, please visit 

the Sirius Minerals website: http://www.siriusminerals.com 

Ben Hall is project manager and team leader in the mechanical 

engineering group in Australia. He has over 10 years of experience 

and his particular interest is combining engineering services with 

sustainable practice in the environmental and commercial sectors.

Network 

Reshaping Social Impact Assessment: 

Implications for Resource Companies and 

Their Role in Housing Provision 

by Ceit Wilson, Brisbane, Australia, +61 7 38546766, cwilson@pb.com.au 

The Bowen Basin holds the largest coal reserves in Australia, 

with deposits covering a total approximate area 

of 60,000km 2 . The rapid expansion of the mining industry 

and accompanying population growth in this region 

has placed significant pressure on already limited social 

infrastructure existing in local rural and regional communities. 

In particular, most resource towns have experienced 

recurring housing shortages and ongoing housing 

affordability concerns. 

Dealing with these impacts is posing significant 

planning challenges not only for government, but 

increasingly for mining companies. In parallel with the 

growth in mining development, there has been a growing 

movement in the industry towards more social responsibility 

and sustainable development. However, the 

absence of a governance or regulatory framework for 

managing housing impacts has left some operations illprepared 

to meet these changing expectations. 

This article discusses the role mining companies 

have taken in the planning and delivery of housing 

infrastructure within the Bowen Basin and explores 

the changing legislative environment which is currently 

shaping their response to housing impacts. 

The Role of Mining Companies in 

Housing Provision 

In Queensland, most mining companies assist their 

workforce and the broader community in attaining housing 

and accommodation through a range of formal and 

informal housing policies. These include: 

• Private workforce accommodation provision and subsidisation 

policies, for example, on-site accommodation 

for Fly-in Fly-out (FIFO) and Drive-in Drive-out (DIDO) 

workforces, local rental or purchasing subsidies; 

• Internal company employment policies and plans (e.g. 

preferencing local resident labour first); 

• Public-private land and housing development partner- 

ships (e.g. with local governments and commercial 

housing providers); and 

• Public-private community services partnerships and 

plans (e.g. provision of housing and employment to 

community workers, such as doctors). 

The range of these housing strategies demonstrates 

that mining companies have considerable interest 

in, and control over, the provision of housing infrastructure 

to the communities in which they operate. This 

reflects several factors, including a change in tax and 

regulatory environment in Queensland, which has led 

mining companies to employ accommodation models 

with a greater focus on operational costs rather than 

a capital focus. These housing strategies also cater to 

the ‘normalised’ contemporary planning environment 

and the lifestyle-related preferences of employees. They 

also attempt to address the displacement of broader 

community members who, without the ‘mine salary’ 

or employer support, are more vulnerable in a housing 

pressure environment. This role is typically undertaken 

through public-private partnerships (e.g., with local governments, 

commercial organisations or local community 

housing providers) and may be viewed as a positive example 

of industry partnerships driven by corporate social 

responsibility (CSR) considerations. 

From a planning perspective, these housing 

strategies can seem to be ad-hoc, isolated and reactive. 

In many cases, broader community provision is driven by 

the need to secure mineworkers and key service workers 

(e.g., doctors, teachers) for the local workforce. The 

housing strategies adopted by multiple mining companies 

present a number of significant challenges to local 

communities, the effect of which has been documented 

succinctly elsewhere (McKenzie et al. 2009; Phillips 

2010). These challenges have been the motive for recent 

reform initiatives introduced by the Queensland 

State Government to improve strategic planning for the 



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20 

impacts of mining operations on resource communities. 

Since 2008, the Queensland Government has 

introduced a series of comprehensive policy initiatives 

which strengthen the social impact assessment (SIA) 

of resource projects within the existing environmental 

impact statement (EIS) process. 

Changing Policy Context 

Sustainable Resource Communities Policy 

At a state level, the sustainability performance of major 

resource developments has traditionally been undertaken 

at the approvals stage where the environmental impact 

statement (EIS) is a key factor in the government decision 

to either grant tenure or reject the application and 

in determining the scope of any approvals, environmental 

authorities, permits and tenures for a proposed new 

mining development. Under this system, the findings of 

the social impact assessment (SIA) have been generally 

‘statistical-based’ and rarely used in a broader capacity 

to identify actions needed to be taken in order to prevent 

the impacts from occurring outside the development site, 

such as in nearby towns or regional communities. 

Based on the need to improve the means by 

which social and cumulative impacts of resource development 

are addressed, the Queensland State Government 

introduced the Sustainable Resource Communities 

Policy, which applies to all new or expanded major 

resource development projects. This policy requires 

the development of Social Impact Management Plans 

(SIMPs), which are a legislative mechanism to facilitate 

the ongoing management of impacts identified in the 

SIA across the life-cycle of resource developments. The 

plans are prepared by the proponents and outline the 

forecast changes to communities in terms of local and 

cumulative effects, the agreed strategies for mitigating 

the effects, and the responsibility of various parties in 

relation to the strategies. SIMPs are reported as separate, 

stand-alone documents which, in turn, have brought 

SIA issues to the forefront of the EIS process. 

Implications for resource clients 

By legislation, resource companies are only responsible 

for the provision of housing to accommodate their project 

workforces. There has been a concerted move however, 

by the State Government, to require resource companies 

– as a condition of SIMPs – to provide direct housing 

for key service workers and low-income earners within 

the general community. This requirement has emerged 

in light of specific conditions placed on the recently approved 

Curtis Island Liquefied Natural Gas (LNG) Project 

in the Surat Basin. In addition to the provision of project 

Network 

workforce housing, it was conditioned that the proponent, 

Queensland Gas Company (QGC), mitigate its impact on 

accommodation for low income households ‘through the 

provision of new or additional supply of housing stock… 

or by contributing to a government sponsored community 

and affordable housing initiative’ (DEEDI 2010, p.163). 

This was supported by the condition that QGC provide 

resources for community housing at the rate of ‘1 unit 

of accommodation for every 8 imported workers’ (DEE- 

DI 2010, p.164). This indicates significant institutional 

change in that, rather than being voluntary, the role of 

mining companies in providing housing to the wider community 

now has the potential to be mandated by the state 

as a condition to the granting of mining tenure. Such policy 

suggests expectation by the State Government that 

mining companies share responsibility for and contribute 

to housing development in resource towns beyond their 

own operational needs. 

Major Resource Projects Housing Policy 

A common theme that can be drawn from recently implemented 

resource-related policies is the need to optimise 

the liveability and sustainability of resource communities, 

particularly with regard to community permanence 

and development of housing affordability. In August 

2011, the State Government introduced the Major Resource 

Projects Housing Policy (MRPHP) (DEEDI 2011), 

a policy which is intended to guide proponents of major 

resource projects in considering accommodation and 

housing issues as part of the EIS process. Specifically, 

the policy sets out principles to be used by government, 

industry and community each time a resource project 

is subject to environmental and social impact assessment. 

This MRPHP is intended to work alongside the SIA 

and SIMP process to ensure that the identification and 

management of worker accommodation and broader 

housing impacts, as part of project development, are 

comprehensive and take account of Queensland State 

Government policy settings. 

Implications for resource clients 

The MRPHP provides greater opportunity for resource 

companies to engage in a more coordinated and effective 

approach to planning for growth in Queensland. This 

policy however, presents several potential risks, particularly 

to projects currently undergoing environmental impact 

assessment for approval (Cawthera 2011). At the 

basis of this policy is the need to address the increasing 

adoption of FIFO commute operations by the mining 

industry as an alternative to the development of new, 

permanent accommodation solutions. One recent major

esource project, submitted to the Queensland Coordinator 

General this year, proposed a controversial ‘100 

per cent’ FIFO operational workforce. The MRPHP thus 

states that resource project proponents must locate 

a proportion of their operational workforce in local resource 

towns, despite underlying emphasis throughout 

the policy on giving workers ‘choice’ on where they live 

(DEEDI 2011, p.7). As a result, it is likely that commuter 

workforces will become more restricted, with flow-on impacts 

to the effectiveness of attraction and retention 

competitive strategies and the flexibility of operation 

rosters employed by companies. 

The MRPHP also requires project proponents 

to provide greater detail of their workforce breakdown 

and accommodation strategy. In most cases, workforce 

and accommodation planning is not typically conducted 

concurrently with project planning and assessment activities, 

as staffing figures projected in the early phases 

of a project may change as project and roster requirements 

are reviewed. When outlining accommodation village 

strategies, project proponents must also include 

details of the projected size, design and location. These 

details are typically only finalised later in the development 

application process, a phase which may occur 

potentially several years after project approval and the 

grant of mining tenure. Where previously required only 

to provide overview of a project’s potential impacts, this 

policy demands that project proponents have a comprehensive 

understanding of all housing elements prior to 

submission of an EIS, including workforce, commuting 

structures and workforce housing options. In effect, the 

MRPHP requires a level of certainty and detail which has 

not traditionally been seen at the time of approval. 

Conclusion 

The involvement of mining companies in housing provision 

has raised challenges for planners, government and 

proponents as never before. Where previously driven by 

pragmatic commercial decisions, planning and legislative 

policy now poses very real implications for the role of 

mining companies in housing delivery. Only through early 

open-dialogue between government, mining companies 

and community can we begin to clarify the expectations of 

our clients for planning and housing delivery in resource 

areas. Parsons Brinckerhoff is working with our clients to 

manage and draw opportunity from the increased scope 

of social impact assessment in Queensland and has 

recently developed several Social Impact Management 

Plans (SIMPs) for major mine projects, including Wandoan 

Coal Mine (Xstrata) and Caval Ridge Coal Mine (Billiton 

Mitsubishi Alliance). With the impacts of major resource 

Network 

projects on housing affordability and availability under 

greater scrutiny by government, Parsons Brinckerhoff is 

well poised to help our clients with SIA and workforce accommodation 

solutions. 

Ceit Wilson is an urban and regional planner with a particular 

interest in mining and resource development projects. In addition 

to her planning experience, she assists the community consultation 

team with social impact assessment and stakeholder 

consultation activities. In 2011, she was awarded the Minister’s 

Town Planning Prize for her thesis, which examined mining companies 

and their role in resource community development. 

Reference List 

• Cawthera, J 2011, Potential risks and opportunities for (client) 

on the release of the Queensland Government’s Major 

Resource Projects Housing Policy, prepared by Parsons 

Brinckerhoff, Brisbane: Queensland. 

• Department of Employment, Economic Development and 

Innovation (DEEDI) 2010, Coordinator-General’s report on 

EIS: Queensland Curtis Liquefied Natural Gas project, accessed 

28th October 2011, http://www.deedi.qld.gov.au/ 

cg/queensland-curtis-lng-project.html 

• Department of Employment, Economic Development and 

Innovation (DEEDI) 2011, Major Resource Projects Housing 

Policy: Core principles to guide social impact assessment, 

Queensland Government: Brisbane. 

• Department of Tourism Regional Development and Industry 

(DTRDI) 2008, Sustainable Resource Communities Policy: Social 

Impact Assessment in the Mining and Petroleum Industries, 

Queensland Government: Brisbane. 

• Franks, D, Brereton, D and Moran, C 2008, Managing the 

Cumulative Impacts of Multiple Mines on Regional Communities 

and Environments in Australia, paper presented to the 

‘International Association for Impact Assessment’, Assessing 

and Managing Cumulative Environmental Effects Special 

Topic Meetings, 6-9 November 2008, Calgary, Canada. 

• Haslam McKenzie, F, Brereton, D, Birdsall-Jones, C, Phillips, 

R and Rowley, S 2008, A Review of the Contextual Issues Regarding 

Housing Market Dynamics in Resource Boom Towns, 

AHURI Positioning Paper No.105, Housing and Urban Research 

Institute of Western Australia: Perth. 

• Phillips, R 2010, Policy Responses to Complex Housing Problems: 

The Roles of Markets, Hierarchies and Networks, paper 

presented at the ‘4th Australasian Housing Researchers 

Conference’, 5-7 August 2009, Sydney, Australia. 

• Wilson, C 2010, Housing Resource Communities: The Role 

of Mining Companies in Rural Development, Unpublished 

Undergraduate Thesis, School of Geography, Planning and 

Environmental Management, University of Queensland, 

Brisbane. 



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Technology as an enabler 

Dating back to prehistoric times, mining is one of the 

oldest activities undertaken by mankind and has been 

a fundamental contributor to sound economies around 

the world. Whether it’s the extraction of commodities 

such as iron ore, coal and base metals for industry and 

manufacture, or precious or semi-precious stones for 

consumer use, mining is the critical activity to extracting 

these commodities. 

But unlike our forebears of the early 19th century, 

who fossicked (searched) for riches with limited 

implements, today there is a vast array of sophisticated 

tools available to the modern mining industry. However, 

the industry also has many more considerations, such 

as stringent government regulations, environmental 

impacts, health and safety of employees, community 

concerns and shareholder value. 

To address many of these concerns, proponents 

of large projects are increasingly turning to 3D 

visualisation software to give client and community 

stakeholders an opportunity to ‘experience’ infrastructure 

before it is built. 

Case Study - Tampakan Copper–Gold Project 

in the Philippines 

Xstrata Copper has recently adopted 3D technology, 

with the assistance of Parsons Brinckerhoff’s 3D visualisation 

team, for the proposed Tampakan Copper– 

Gold Project in the Philippines. 

Background 

The Tampakan Project is located on the southern Philippines 

island of Mindanao and is one of the largest undeveloped 

copper–gold deposits in the Australia-Pacific 

region. The controlling interest in Tampakan is held by 

Xstrata Copper, with management control of the project 

Network 

Looking at Mining Differently – 

3D Visualisation Helps to Take 

the Guess Work Out 

by Alan Hobson, Brisbane, Australia, +61 7 38546585, ahobson@pb.com.au; and Dylan Swan, Brisbane, Australia, 

+61 7 38546463, dswan@pb.com.au 

operating through Xstrata’s Philippines-based affiliate, 

Sagittarius Mines Incorporated (SMI). 

After positive findings from an extended pre-feasibility 

study, SMI launched a US$74 million feasibility 

study in mid-2009 to determine whether the Tampakan 

Project would advance to development stage. As part of 

the study, Parsons Brinckerhoff’s 3D visualisation team 

helped prepare images and animations for the environmental 

and social impact assessment (ESIA) and for interactive 

community consultation displays. Xstrata Copper 

is committed to running the Tampakan Project in line 

with current leading environmental and social practices. 

Xstrata Copper had very clear goals for the first 

stage of the project: to give people a visual impression 

of the project’s layout and an understanding of the benefits 

it would bring, the potential impacts it might have, 

and what the mining process would entail. Developing 

a realistic simulation of the project was one way to give 

stakeholders, including representatives of the Philippines 

Government, a realistic impression of what was 

being proposed. 

SMI developed a mobile Community Information 

and Resource Centre (mCIRC). This was a Bedouin-style 

tent complete with community exhibits, interactive 

touch-screens, and plasma TVs with live animation. 

It was demountable; however, the logistics required 

to move it around the region were complex, including 

transport, a power generator and security. 

Parsons Brinkerhoff was engaged to develop 

visual content for the mCIRC which included 3D animations, 

simulations, and still shots, all of which were 

placed on an interactive touch-screen application (see 

Figure 1). This method encouraged the community to 

interact with the images of the proposed mine site and, 

through this, to gain a greater understanding of it. The 

content was tailored to suit various audiences and was

Figure 1 – Touch Screen Dashboard for the Tampakan Project 

presented in a number of languages and at differing 

learning levels. 

The data set was extremely large and the Parsons 

Brinckerhoff visualization team was on a tight 

timeline to meet the ESIA deadline. 

Details of 3D visualization for the 

Tampakan Project 

Touch Screen Dashboard 

The Dashboard is a presentation tool that allows quick and 

easy access to all visualisation data. It shows a map of the 

mine site area with icons to display visualizations from that 

location which includes: 

• Video – animated mining processes and computer generated 

fly-through animations; 

• Images – photos, computer generated renders and before/after 

comparisons; 

• 3D interactive software –similar to a computer game 

where the user is able to navigate around the scene to 

view points of interest in 3D (see Figure 2). 

Clicking on an icon opens up a large window 

over the map (known as a lightbox effect) with the content 

described above. It also features controls to hide 

or show layers. 

Implementation 

The software uses standard HTML, CSS, JavaScript and 

Network 

Flash and runs via a web browser. Add-on software includes 

Acrobat Reader for 3D PDFs, Navisworks Freedom 

and Anark for the 3D interactive products. All of the 

software is included on the CD/DVD when it is delivered 

to the client. No installation is required for the Dashboard 

product itself which is self-contained and does 

not require connections to servers. 

Benefits 

The implementation method allows for a very flexible 

and portable presentation which is: 

• Non-linear – all data is available directly and intuitively 

via spatially located icons on a map, which avoids 

the need to search through lists of files, folders or 

slideshows. This allows presentations to be adjusted 

very quickly for different audiences and questions 

are answered immediately by having fast access to 

all the data. 

• Adaptable – it is designed to be used on a standalone 

computer, but is easily transferred to intranet/internet 

environments or even large public touch screens with 

minimal changes required thanks to the use of web 

technologies and small data size. 

• Easy to use – just click once on any icon to display the 

content from that location and click again to close it 

(see Figure 3). 

• Scalable – this interface can be used for a simple map 



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Figure 2 – Example of 3D interactive software 

Figure 3 – Computer generated images 

with some photos or expanded to include almost any 

type of visual product using the same template. 

Seeing is believing 

It took more than a year for the mCIRC to be completed 

and it was deployed in June 2010. Community reaction 

to mCIRC has been extremely positive, and SMI 

Network 

was happy with the final 

product. 

Through the mC- 

IRC, local communities 

and other stakeholders 

have gained a comprehensive 

picture and understanding 

of the proposed 

Tampakan Project 

that has gone beyond 

what could have been 

achieved using traditional 

engagement methods. 

Alan Hobson is technical 

executive of VDC (virtual 

design and construction) & 

innovation. He is involved 

in delivery of VDC, visualisation, 

and geographic information 

system solutions for mining related projects within 

Australia and internationally. 

Dylan Swan is a visualisation consultant for Parsons Brinckerhoff 

with many years experience as a programmer and project 

manager. He has an honours degree in civil engineering and 

diplomas in information technology and 3D animation.

Network 

High Lift Belt Conveyors for 

Underground Hard Rock Haulage 

by John C. Spreadborough, Brisbane, Australia, +61-7-3854-6406, SpreadboroughJ@pbworld.com 

The scale of underground hard rock mass mining 

operations is increasing. The International Caving 

Study 1 categorized current and future underground 

mass mining operations by production rate as: ‘large’, 

‘bulk’ and ‘super’. 

The ‘large’ category was defined as producing 

4–6 million tonnes per annum (Mt/a); ‘bulk’ as producing 

10–20 Mt/a; and ‘super’ as producing or planning to 

produce in excess of 25 Mt/a. 

The ‘super’ mines are addressing production 

rates exceeding 40 Mt/a and lifts up to 2000 meters. 

The haulage systems for these ‘super’ underground 

mass mining projects are based on hoisting and belt 

conveying technologies (Figure 1), and in some cases 

incorporate multiple parallel streams with multiple serial 

flights in each stream. The proposed Resolution Cop- 

Figure 1 - High lift belt conveyor 

per Mine in Arizona will incorporate three 2000-meter 

lift parallel hoisting streams in each production shaft 

for 40 Mt/a. The proposed Chuquicamata Copper Mine 

in Chile will incorporate one stream of three conveyor 

flights at slopes up to 6.8 degrees for 45 Mt/a with a 

total lift of 1500 meters. 

Table 1 – Details of ‘large’, ‘bulk’ and ‘super’ mass mining operations 

Table 1 and Figure 2 present details of a selection 

of operations in each of these categories. 

This article presents an overview of current belt 

conveyor systems in underground mass mining operations, 

and describes their lift and production rate limits. 

These limits of application are illustrated with reference 

to the limits of application of drum and friction winder 

hoisting systems. 

1 The International Caving Study was carried out over the period 1997 - 2004 by the Julius Kruttschnitt Mineral Research Centre, the University of 

Queensland (Brisbane, Australia) and the Itasca Consulting Group (Minneapolis, USA). The study was sponsored by a number of major international 

mining companies. These included Codelco (Chile), DeBeers (South Africa), LKAB (Sweden), Newcrest, Rio Tinto and WMC (Australia). 



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Haulage Systems for Underground Mass Mining 

Belt Conveying Systems 

Details of belt conveyors currently operating or planned for 

future operation in underground mass mining operations 

are presented in Table 2. These conveyors are configured 

for slopes of around 10 degrees based on the limiting 

slope for rubber tyred mining equipment. 

Belt conveying is a continuous process. Each conveyor 

in a multi-flight conveyor stream delivers to the tail of 

the downstream conveyor. 

Belt conveying systems for hard rock mines incorporate 

a crushing station to reduce the run-of-mine material 

to a size suitable for conveying, and a tramp detection 

and removal system to remove tramp material from the 

ore stream to prevent belt damage and blockage. 

Network 

Figure 2 – Vertical lift vs. annual production of ‘large’, ‘bulk’ and ‘super’ mass mining operations 

Table 2 – Details of high lift belt conveyors in underground mass mining operations 

2 Note: ST****: ST = steel cord, **** = strength rating 

Figure 3 - Friction Winder 

Hoisting Systems 

Hoisting is a batch process which 

incorporates crushing stations, 

tramp detection and removal systems 

similar to those provided 

for belt conveying systems, skip 

loading stations, skip hoists and 

skip dumping stations. 

A balanced skip hoisting 

system incorporates a winder, 

a headframe, a pair of skips and 

interconnecting ropes. The winder 

and the interconnecting ropes are 

arranged to support the skips so 

that one skip balances the other - 

that is, one is raised as the other 

is lowered. 

Hoisting systems are driven 

by either drum or friction winders 

(Figure 3). The head ropes 

of a drum winder are terminated 

at the winder drum and coil onto 

the drum as the associated skip 

is raised, and off the drum as the 

skip is lowered. The head ropes 

of a friction winder pass over the 

drum and are driven by friction between 

the rope and the drum shell 

(see Figure 4).

Figure 4 – Schematic diagrams - drum and friction winders 

Lift and Production Rate Characterization 

Free Length 

Belt conveying and hoisting systems are limited in lift 

and production by the strength and weight properties of 

the belt or rope respectively. 

The ratio of the strength of a tension element 

to its weight per unit length is known as its free length 

- that is, the maximum length that can support its own 

weight. The weight of the rubber that encases and protects 

the conveyor belt cords reduces the free length of 

the assembly. 

The standard range of steel cord belt constructions 

defines the combinations of cord pitch and cord diameter 

that provide for greater free 

lengths, thus higher belt strengths. 

Conveyor belting is also 

provided with additional cord protection 

rubber covers at the carry 

side (the side subjected to material 

abrasion). The required cover 

thickness depends on the application 

loading conditions, loading 

frequency, and material lump size, 

density and abrasiveness. 

An application that is categorized 

as having a light cover 

duty can be fitted with a belt having 

lighter covers than can an 

application assessed to have a 

severe cover duty. Hence, belt con- 

Network 

structions for light duty applications 

have greater free lengths. 

Figure 5 illustrates the 

impact of belt strength and cover 

duty on belt free length for a range 

of belt constructions and for two 

extremes of cover duty. The free 

length of conveyor belting ranges 

from around 2 km for low strength 

carcasses to around 8 to 10 km for 

high strength carcasses, depending 

on the cover duty. 

The free length of winder 

ropes is constant across a range of 

rope diameters at around 17 km. 

Safety Factors 

Belt factors of safety are selected 

for an application taking into account 

measures to ensure the 

integrity of the splice fabrication, 

the fatigue duty to which the splice is subjected, and the 

additional stresses generated in the belt at the head 

end transition. 

The minimum belt factor of safety for a high 

lift underground hard rock application is approximately 

5.2 where: 

• the splice fabrication assessment is favorable 

• the splice life assessment recognises the issues associated 

with life expectancy, consequences of failure and 

the physical demands of the application 

• the head end transition geometry is generous. 

Rope factors of safety for hoisting systems are 

selected for rope life, taking into account the fatigue duty 

Figure 5 – Free length of conveyor belting and winder ropes 



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28 

to which the rope is subjected. A rope factor of safety of 

5.1 has been applied in this characterization of lift and 

production rate. 

Speed 

Belt conveyor production is constrained by practical limits 

on the belt speed. These limitations are associated 

with noise and dust generation, and the risk of damage 

and injury. 

Hoisting system production is also restricted by 

practical limits on the rope speeds that are associated 

with rope and shaft guide resonance effects. The hoisting 

system characterizations presented below are based 

on maximum rope speeds of 19 m/s. A typical hoisting 

cycle is depicted in Figure 6. The cycle time of a hoisting 

system increases linearly with increasing lift. 

Figure 6 – Hoisting cycle for characterization and lift and production rate 

Network 

Figure 7 – Lift and production rate characteristic curves for high lift belt conveyors 

Belt Conveyors 

The maximum belt tension in a high lift belt conveyor is at 

the high tension side of the discharge pulley and is calculated 

as the sum of the tail end tension and the carry side 

secondary, slope and main resistances. 

The productivity of a belt conveyor is independent 

of its length or lift. 

Typical belt conveyor lift and production rate 

characteristic curves are presented in Figure 7 for belt 

widths increasing from 1.0 meter in steps of 0.2 meters, 

and belt carcasses from ST500 to ST7100. 

Hoisting Systems 

The maximum rope tension in a hoisting system is calculated 

as the sum of the weights of the head ropes, 

the conveyance and payload, and the tail ropes. 

The payload of a hoisting 

system reduces with increasing 

lift. The cycle time increases with 

increasing lift. The productivity of 

a hoisting system reduces with 

increasing lift due to both the reducing 

payload and the increasing 

cycle time. 

Typical lift and production 

rate characteristic curves are presented 

in Figure 8 for a two-head 

rope drum winder and a six-head 

rope friction winder with head 

rope diameters from 20–60 mm. 

Comparison of Belt 

Conveyors and Hoisting 

Systems 

Figure 9 presents the lift and production 

rate characteristic curves for 

high lift belt conveyors overlaid on 

those for drum and friction winders. 

Drum and friction winders 

can operate at lifts exceeding 

2000 meters and are limited in 

production to around 4000 t/h 

for two-rope drum winders, and 

around 10,000 t/h for six-rope 

friction winders. Hoisting systems 

are operated in serial and 

parallel combinations to deliver 

the production rates and lifts required 

for the ‘super’ mass mining 

operations. 

Belt conveyors are limited

in lift to around 800 meters by belt 

strength. Belt conveyors are unlimited 

in production beyond 10,000 

t/h. Relatively uncomplicated serial 

combinations of belt conveyors can 

deliver the lift requirement of a ‘super’ 

mass mining operation. 

The characteristic curves 

presented in Figure 9 illustrate that 

the production rate and lift requirements 

of a ‘super’ mass mining 

operation can be delivered by serial 

combinations of belt conveyors at 

conservative belt speeds and with 

conventional belt constructions. 

A ‘beyond super’ duty with 

a 2000 meter lift at 10,000 t/h 

would require, allowing for lift losses 

at the transfers, a conveyor system 

with two streams of 5000 t/h, each 

with four flights of 520 meter lift. 

The belt would be two meters wide, 

ST5500 running at 6 m/s. 

A comparable hoisting system 

for this duty would require three 

streams of 3333 t/h, each with two 

flights of 1085 meter lift. The winder 

would be a six-rope friction winder. 

The head ropes would be 60 mm diameter 

hoisting 96 t payload skips. 

Comparative capital cost estimates 

for these systems indicate a 

20% disadvantage for the conveyor 

system. Demand power estimates indicate 

a 30% RMS (root-mean-square) 

power advantage and 50% peak power 

advantage for the conveyor system. On this basis, the 

life-of-mine costs will favor the conveyor system. 

Conclusion 

This article has presented an overview of current high 

lift belt conveyors and their application to underground 

hard rock haulage. Their lift and production rate characteristics 

have been compared with vertical shaft 

hoisting systems based on two-rope double-drum and 

six-rope friction winders. 

These characterizations have been presented in 

the context of the increasing scale of current and future 

underground mass mining operations. Production rates 

are approaching 45 Mt/a in mines planned to operate with 

lifts up to 2000 meters. 

Network 

Figure 8 – Lift and production rate characteristic curves for drum and friction winders 

Figure 9 – Lift and production rate characteristic curves for winders and high lift belt conveyors 

Relatively uncomplicated multi-flight belt conveyors 

are being applied to haulage systems for underground 

hard rock mass mining operations in configurations capable 

of application at these extremes of duty. 

These multi-flight belt conveyor haulage systems 

can offer significant reliability, flexibility and operating 

cost advantages. 

John Spreadborough is a mechanical engineer and technical executive 

who specializes in bulk materials handling. He has over 

25 years of experience in the mechanical design, construction and 

commissioning of materials handling plants and equipment for a 

range of bulk materials, and has been involved in the design of 

hoisting systems and high lift conveyors for both coal and hard 

rock. His credentials include BEngMech, MIEAust and RPEQ. 



29



30 

Parsons Brinckerhoff has had a major involvement in technical 

studies for a large scale green-field open pit copper mine 

in South-East Asia, designed to process up to 66 million 

tonnes of ore annually. 

The most economical transportation method 

identified for ore and waste rock was a conveyor system. 

The project is located in mountainous and densely vegetated 

terrain, so the most suitable type of conveyor system 

required investigation. 

Parsons Brinckerhoff’s involvement with the project 

spanned over three years with engineering and management 

of the extended prefeasibility and trade-off study 

phases, then as owner’s engineer and consultant engineer 

for the feasibility study conducted by others. 

Conveyor technologies 

Two conveyor technologies were considered: a conventional 

conveyor system and Doppelmayr’s proprietary 

RopeCon®system. 

Conventional conveyor systems are common 

in mining (see Figure 1). They consist of a reinforced 

rubber belt running on rotating idlers, which are positioned 

to form the belt into a trough shape. The belt is 

driven by pulleys connected to motors and gearboxes. 

Conventional conveyors range dramatically in length 

Network 

Conveyor Technology Selection 

for a Large Copper Project 

by Scott Tapsall, Brisbane, Australia, +61 7 38546934, stapsall@pb.com.au 

Figure 1 - Conventional overland conveyor 

(over 20km), capacity (over 10,000 tonnes per hour) 

and power, depending on their application. They are predominantly 

mounted on the ground, or on an elevated 

structure where necessary. Conventional conveyors can 

traverse horizontal curves, with the minimum radius dependant 

on capacity and belt tension. Many different 

manufacturers and designers are able to supply a conventional 

conveyor system. 

RopeCon® is a new technology with limited installations 

around the world. The system combines conveyor 

and aerial ropeway technologies (see Figure 2). The belt 

has integrated axles and wheels that run along fixed steel 

ropes. The belt is flat, but has corrugated sidewalls to 

contain material, and is driven by motorised pulleys. The 

largest capacity RopeCon® currently in operation is rated 

at 1,200 tonne per hour (tph), but systems have been 

designed up to 20,000 tph. The system is suspended 

above the ground, forming a catenary between towers, 

which may be up to 1,500 m apart. The ability of Rope- 

Con® to traverse horizontal curves is limited to small directional 

changes at the supporting towers. 

Pre-feasibility Study (PFS) 

A required capacity of 12,000 tph was calculated for 

the ore and waste rock conveyors. This is a very high 

capacity, with few long conveyors in the world running 

at this level. Due to seismicity concerns at the site, 

the client requested the conveyor design minimise elevated 

structure. The ground on site has the potential 

to form acid with exposure to air, which needed to be 

taken into consideration for waste rock disposal and 

major earthworks during construction. The transport 

distance was approximately 3.5 km for ore, and 12 km 

for waste rock. 

A conservative approach was taken for a conventional 

conveyor. Sufficient design was carried out to verify 

that it would be functional, but a full dynamic analysis of 

the design was not performed to optimise the profile. The 

resulting designs required very large earthworks quantities 

due to the terrain.

Figure 2 - RopeCon® cross section and installation 

A RopeCon® system was also designed to determine 

if there were benefits, given the rugged terrain. 

Since the largest RopeCon® in operation had a capacity 

of 1,200 tph, the capacity was limited to 6,000 tph 

per system to moderate the scale-up risk. Therefore 

two RopeCon®s had to run in parallel to achieve the 

required 12,000 tph. 

At PFS level, the two systems were relatively comparable 

in installed cost, although RopeCon® had lower 

predicted operating costs. 

After a period of evaluation, the RopeCon® solution 

was selected. It required approximately 1% of the 

earthworks for the conventional conveyor system. This 

meant the RopeCon®: 

• could be installed 12 months earlier, removing the 

construction of the conveyor from the critical path; 

• required far less treatment of potentially acid forming 

(PAF) cuts and spoil; 

• had far less environmental impact. 

Trade-off Studies (TOS) 

The trade-off studies aimed to optimise the PFS design 

to reduce the capital cost estimate and the construction 

schedule. Changes included: 

• an assessment of optimal crusher, concentrator and 

waste rock deposition locations, leading to new conveyor 

alignments and increased lengths; 

• ore conveyor capacity reduced from 12,000 tph to 

10,000 tph and waste rock to 6,000 tph; 

• RopeCon® conveyors designed for the full 10,000 tph capacity 

during this phase. This meant that parallel Rope- 

Con® systems were not required as they were in the PFS; 

• waste rock system capable of carrying ore to allow pro- 

Network 

duction to continue if the ore system was inoperable; 

• horizontal curves permitted for the conveyor alignments 

(however it was found this resulted in no cost reductions). 

The new designs resulted in the RopeCon® being 

slightly more expensive than the conventional conveyor 

system, but the construction time was significantly less 

due to the reduced earthworks. The RopeCon® scale-up 

risk from 1,200 tph to 10,000 tph was considered a disadvantage. 

This, combined with the lower capital cost of the 

conventional conveyor, meant a conventional system was 

selected for the TOS. 

As there were still topography and geotechnical 

uncertainties at the site, both technologies were investigated 

further in the feasibility study. 

Feasibility Study 

During the feasibility study (FS), a change in mine design 

required a revised crusher location and an increase 

in the ore conveyor capacity to 11,000 tph. The ore 

conveyor system was now 8.5 km long, the waste system 

12 km. Site investigations during the FS revealed 

ground conditions were not as good as expected during 

the PFS and subsequent trade-off studies. This resulted 

in a large increase in earthworks quantities, as the batter 

angles were reduced to ensure slope stability. It increased 

the length of construction and increased the 

amount of PAF rock disturbed during construction. 

The increase in earthworks added considerable 

cost to the conventional conveyor system. Since 

RopeCon® uses distantly spaced towers, the increase 

in earthworks and cost was minor in comparison. The 

increased cost and risk for the conventional system 

meant the RopeCon® was selected for the FS. 



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Post Feasibility Study 

The RopeCon® system still had a considerable scale-up 

risk, so a risk mitigation project was undertaken by Parsons 

Brinckerhoff staff, as part of the owner’s team. Key 

design staff and independent peer reviewers were invited 

to join the review team. 

The project involved the following primary activities 

by Doppelmayr and the review team: 

• Doppelmayr produced designs that could be reviewed 

for constructability, maintainability, safety, calculation 

accuracy, etc.; 

• Doppelmayr carried out design, construction and testing 

of the components identified as being critical and 

outside of comparable service elsewhere. The key components 

are belt, wheels, axles and frames; 

• The review team visited various RopeCon® design 

and manufacturing sites. The team also viewed the 

in-progress designs of other RopeCon® client’s 

systems; 

• The review team visited working RopeCon® installations. 

The overall result was a very high level of confidence 

in Doppelmayr and the RopeCon® technology, and 

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the RopeCon® design is no longer considered one of the 

highest risks on the project. 

Conclusion 

High capacity conveyor systems provide an efficient means 

of transporting bulk materials over long distances. Choosing 

the most suitable type of conveyor depends on many 

variables, including capacity, terrain, ground conditions, 

cost and constructability. 

First of a kind technologies can add significant 

value to certain projects if the risks are correctly managed. 

For this project, Parsons Brinckerhoff determined 

that the RopeCon® system was the best solution. Whilst 

RopeCon® may also be suitable for other mines and projects, 

an analysis should be undertaken to determine the 

best solution for each site. 

Scott Tapsall is a senior mechanical engineer involved in materials 

handling work at Parsons Brinckerhoff and has twice been seconded 

to major mining clients to work on studies for large open cut 

copper mines. He has a mechanical engineering degree from the 

Queensland University of Technology.

Network 

Parsons Brinckerhoff Global Mining ePCM 

Risk Management: A Proactive Approach 

by Jereme Evans, Singleton, NSW, Australia, +61 488 720 270, Evansjer@pbworld.com 

Risk management within the resources industry can be 

viewed as an evolution. At the beginning, risk management 

established the fundamental process of identifying, 

assessing and controlling hazards. Inevitably 

risk professionals began developing specialist risk 

analysis techniques, providing a more methodical approach 

to assessing risks associated with processes, 

activities and assets. Examples of such techniques include 

HAZOP (hazard and operability study) & HAZID 

(hazard identification study) where, even after decades 

of application, the fundamental processes remain unchanged 

today demonstrating their effectiveness. However, 

these fundamental risk analysis processes are 

currently failing to meet the growing demand for risk 

analysis requirements in the engineering, procurement 

and construction management (EPCM) environment, 

requiring risk specialists to 

develop new techniques. 

Fast forward to the 

21st century, the business 

environment has become 

more risk adverse. Stringent 

regulation, improved 

corporate governance, and 

public opinion are inducing 

industries to adopt new techniques 

in the development 

of proactive risk management 

strategies and practices, 

improving an organisation’s 

ability to achieve 

business objectives, protect 

the environment and its people. 

Parsons Brinckerhoff 

recognises this challenge 

and is providing assistance 

to clients in achieving their 

project goals through the 

delivery of a specialised risk 

Figure 1 – Parsons Brinckerhoff Risk Management Framework 

management system. Established hazard analysis techniques 

used in the EPCM environment (e.g., HAZOP) 

are no longer fulfilling the demands of total EPCM risk 

management, where all various types of project risks 

(HR, project schedule, reputation, etc.) require a different 

approach to be managed. Although techniques 

like HAZOP are still very much an effective tool for 

EPCM projects, with the current risk climate within the 

resources sector demanding more stringent risk analysis/management, 

a ‘one size fits all approach’ will fail 

to meet expectations. 

Parsons Brinckerhoff has developed a risk 

management framework enabling each individual project 

to have tailor made risk management techniques 

in line with client risk management standards that reflect 

the client’s risk appetite. Figure 1 illustrates this 

ePCM Risk Management 


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34 

process and how both client and Parsons Brinckerhoff 

policies and systems are applied. 

Creating a risk management system that provides 

complete EPCM scope coverage requires initiating 

new hazard study types and applying variations of 

existing hazard studies. New hazard study techniques 

incorporating other factors, like community impact and 

user behavioural considerations (e.g., RAMBO, defined 

below), are emerging as a more common option for managing 

risk. Another emerging trend is the development 

of industry specific hazard studies (e.g., OMAT, defined 

below), tailored for managing risks specific to the operating 

environment. Parsons Brinckerhoff’s risk management 

system enables the use of these emerging hazard 

study techniques, as well as traditional techniques, providing 

greater flexibility and ability in assisting clients 

achieve their goals. An example of Parsons Brinckerhoff 

using this approach to risk management is the Bengalla 

Expansion Project (BEP) located in the Hunter Valley, 

Australia. Parsons Brinckerhoff has been engaged by 

Coal & Allied to manage the phase 1 expansion of their 

current operations, which will result in increasing annual 

coal production by approximately 20%. Phase 1 incorporates 

the expansion of current infrastructure and the 

coal handling and preparation plant (CHPP) and increasing 

the size of the heavy mobile equipment (HME) fleet. 

This project incorporates the client’s risk management 

framework and, through the application of specialist risk 

analysis techniques, ensures that all risks in the delivery 

of the EPCM scope are captured whilst maintaining 

compliance to client requirements. Specialist risk analysis 

techniques used on BEP include: 

Hazard Operability Study (HAZOP) – This is the most recognised 

method of hazard study, traditionally managing 

risks covering the entire lifecycle of the asset. HAZOPs 

are orientated towards managing health, safety and environmental 

risks and are reliant on the application of 

terms/phrases prompting the identification of hazards. 

Parsons Brinckerhoff applies HAZOP traditionally in the 

construction/assembly of mechanical assets. For the introduction 

of new HME (e.g., Komatsu 830E trucks) to the 

BEP, HAZOPs have been applied to identify risks in operating 

and maintaining the new asset. All tasks relating to 

the new asset are examined, ranging from pre-operation 

inspection to specific scheduled maintenance activities. 

This risk analysis process allows Parsons Brinckerhoff to 

provide recommendations to the client and the original 

equipment manufacturer on what improvements can be 

made to the physical asset prior to hand over and suggestions 

to improve maintenance methodologies. 

Network 

Hazard Identification Risk Analysis (HAZID) – A HAZID 

is one of the most flexible hazard study methods and is 

performed in the early stages of the project. HAZIDs flexibility 

comes from enabling the facilitator to select a scope 

for the hazard study in cases where traditional topics may 

not be covered in other hazard study methods. During 

the planning phase of EPCM projects, this risk analysis 

method is commonly used, as it captures both strategic 

and operational risks derived from the project delivery, 

ranging from reputational to risks from industrial relations 

(IR). Parsons Brinckerhoff has used this technique in the 

execution of the Bengalla Expansion Project, covering topics 

from project HR/IR management to expansion of coal 

handling and preparation plants. 

Construction Hazard Assessment Implication Review 

(CHAIR) – CHAIR is a three (3) tiered risk analysis tool 

derived from the WorkCover Authority of New South 

Wales. A relatively new hazard study (in relation to 

HAZOP), CHAIR is a tool used to reduce health and safety 

risks associated with the construction, maintenance 

and demolition of an asset (typically infrastructure but 

can be applied to any asset). CHAIR is divided into three 

(3) levels of risk analysis based upon what stage of the 

lifecycle of the asset is being assessed. Parsons Brinckerhoff 

has used CHAIR in the delivery of infrastructure, 

including public roads (e.g., the Bengalla Link Road project 

in early 2011, which was outside the scope of the 

current expansion work). 

Operability and Maintainability Analysis Technique 

(OMAT) – OMAT is a six (6) step task-orientated risk 

assessment technique developed by the Minerals Industry 

Safety and Health Centre (University of Queensland) 

in consultation with the Earth Moving Equipment Safety 

Round Table (EMESRT) which is comprised of ten (10) 

multi-national mining organisations. This elaborate 

process has been developed specifically for managing 

risks to operators and maintainers of heavy mobile 

equipment (HME) for mining, with the use of industry 

recognised design philosophies from EMESRT. Requiring 

specific software and a rigid approach, OMAT enables 

projects to pinpoint specific risks from operation and 

maintenance of HME. Parsons Brinckerhoff used this 

risk analysis technique in the delivery of HME for the 

Bengalla Expansion Project, including facilitating a workshop 

on the Hitachi EX5500-6 using OMAT. Although 

improvements have been made with the application of 

OMAT on Parsons Brinckerhoff projects, it has proven 

to be more effective when applied by the original equipment 

manufacturer.

Figure 2 – Parsons Brinckerhoff Risk Value Chain 

Reliability, Accessibility/Availability, Maintainability, 

Buildability and Operability Assessment (RAMBO) – 

RAMBO is a risk analysis technique which examines 

the lifecycle of an asset focusing on the five (5) key 

topics. Although RAMBO and HAZOP share a similar 

approach of using key phrases to prompt the identification 

of hazards, RAMBO places emphasis on the 

buildability and reliability of an asset. RAMBO has 

been found to be effective in design of high risk and 

high use workspaces. Parsons Brinckerhoff has applied 

RAMBO in the design and construction of new 

eating/dining rooms (aka crib rooms) for mine employees 

of the Bengalla project. 

Building on the knowledge and information obtained 

from delivering high quality projects to our clients, 

Parsons Brinckerhoff aims to leave its mark on projects 

by continuing to add value to client’s risk management 

activities even after the project team has demobilised. 

Parsons Brinckerhoff’s project risk management system 

Network 

has been structured to provide 

clients with a baseline 

risk profile at the completion 

of the project. This improves 

the client’s ability to identify 

additional opportunities for 

improvement during mine 

operation and maintenance 

activities. Building on the lessons 

learned from the different 

levels of risk assessment 

in the delivery of a project, 

the client is provided with a 

library of risk information, 

including specific risk reduction 

techniques. Figure 2 illustrates 

this process, where 

each level of risk analysis is 

used to improve not only the 

delivery of the project but the 

operation of the asset. 

The Bengalla Expansion 

Project applies this process 

of transferring risk information through the client’s 

change management system and a formal handover of 

all risk information, at the completion of the project. 

Such approaches to risk information handover have 

proven to be welcomed by clients, enabling them to further 

improve future risk management processes. 

Through the development of an integrated 

EPCM risk management system and the application of 

risk analysis techniques tailored to analyse the project 

risks of each individual project, Parsons Brinckerhoff 

has established a robust process to enable the effective 

delivery of an EPCM project. 

Jereme Evans is a risk management specialist with over 10 years 

experience in developing risk management solutions for internal 

application and client requirements. He has worked in a number 

of industries, including resources, construction and aviation, within 

Australia and internationally, and has exposure to various risk management 

methodologies. 



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36 

Fenwick Heap is a former coal mine spoil heap in North 

Tyneside, in the North East of England (Figure 1). Since 

the demise of the local coal mining industry in the 1960s 

and 1970s, dereliction and contamination have blighted 

the area and the public health risk presented by the heap 

was increasing owing to encroaching housing developments 

and the uncontrolled combustion of the colliery 

waste. Parsons Brinckerhoff was commissioned by the 

Homes and Communities Agency (HCA), formerly English 

Partnerships, to design and manage the remedial works. 

The heap was around 8 hectares in plan and extended 

up to 17m in height. It was comprised of a central 

mound (which was combusting) and adjacent crusted-over 

slurry lagoons, which were impounded by the heap and 

further dry spoil bunds (mounds). Remedial works were 

planned to involve excavation, cooling, and controlled 

replacement of the bund materials, followed by capping 

with low permeability clays to minimise the production of 

leachate by percolating rainwater. The excavation of the 

central mound would expose the very soft lagoon slurries 

which would tend to slump into the excavation. 

Previous design proposals included full excavation 

of the heap with excavation of the lagoon slurries by dragline 

and controlled mixing of coarse colliery spoil and fine 

slurries to produce a suitable compacted backfill, possibly 

with the ex-situ mixing of cement or lime additive for stabilisation. 

However, the feasibility of this proposal was not 

supported by any laboratory or field validation testing and 

was further constrained by lack of working space. 

The Parsons Brinckerhoff design limited excavation 

to the immediate area of combustion, and involved re-grading 

of the over-steepened perimeter batters (slopes) for public 

safety. The advantages included a greatly reduced expense 

and time of excavation with corresponding reductions in potential 

environmental nuisances of dust and noise, and the 

reduction in measures required to ensure compliant earthworks 

of mixed and ex-situ stabilised materials. However, 

this design also required the in-situ stabilisation of the very 

soft lagoon slurries, both for support of the surface crust for 

trafficability in areas of capping, and to provide slope stability 

in areas of excavation and re-grading of batters. 

Network 

Fenwick Heap Stabilisation 

by Russell Bayliss, Newcastle, UK, +44 (0)191 2261234, baylissr@pbworld.com; 

Alan Common, Newcastle, UK, +44 (0) 07875 297287, alan.common@geomarine.co.uk; 

Jeff Jennings, Newcastle, UK, +44 (0)191 2261234, jenningsj@pbworld.com 

Figure 1 – Fenwick Heap, central mound combustion 

engineering Aspects of the Stabilisation 

Low permeability clay capping 

The capping clay was site-won glacial till (boulder clay) 

extracted from a borrow pit southwest of the heap. 

The great benefit of site-won capping material 

was the avoidance of haulage of the potentially massive 

quantities of alternative imported material. A further 

benefit was the security of source, giving greater 

financial certainty to the contract. 

Analysis of the column strength and slope stability 

In order to excavate, extinguish and re-compact the 

17m depth of burning coarse colliery waste forming 

the central mound of the heap, it was necessary to 

form batters in the surrounding very soft lagoon slurry. 

There are two principle mechanisms for potential slope 

instability in the slurry: 

• Slip zones, typically analysed as circular slip planes. This 

is the routine method of slope stability assessment. 

• Extrusion, where the retained material squeezes laterally 

at depth. This is a particular consideration for very soft 

materials where it generally predominates. (Figure 2) 

The design of the stabilisation was in accordance 

with Eurocode BS EN 1997: Part 1. The stabilisation 

was temporary works but relied upon adequate 

stabilisation of an abnormal material to prevent mass

Figure 2 – Slurry strength 

failure. It was therefore classified as Geotechnical Category 

3 and it was thus required to adopt routine Category 

2 design but verified by field-testing and inspections. 

The design of the stabilisation also generally 

adopted the recommendations of BRE guidelines 

Eurosoilstab CT97-0351. These are generally aimed 

at stabilisation of very soft and organic natural clay 

soils. Application to the stabilisation of coal processing 

slurry therefore incurs an element of innovation 

which was carefully assessed from preliminary testing 

and further supported the need for verification 

by field-testing and inspection. Interlocking panels of 

stabilised columns are also recommended over a grid 

layout for slopes in very soft soils. 

A simple approach to overall slope stability on 

circular slip planes was adopted using Taylor stability 

curves to assess short-term (undrained) safe slope 

angle against minimum average shear strength and a 

maximum slope height of 16m (Figure 3). 

Thus, for resistance to overall rotational fail- 

Figure 3 – Rotational stability 

Network 

ure, an average shear strength of, say, 50 kPa would 

allow selection of a maximum slope angle of 32˚, and 

the corresponding spacing of columns could be calculated 

for a range of column strengths, based upon the 

nominal column diameter of 600mm (Figure 4). 

Consideration of the required resistance against 

extrusion takes into account the increase of shear strength 

with depth within the slurry (Figure 2) for derivation of both 

the disturbing force due to lateral earth pressure and the 

resisting force due to cohesion (Figure 5). 

Thus, for resistance to extrusion, an average 

shear strength of, say, 90 kPa would require a nominal 

slope angle of 32˚. In this case, the average shear 

strength is that at the base of the excavation and the 

corresponding spacing of columns could again be calculated 

for a range of column strengths, based upon 

the nominal column diameter of 600mm (Figure 6). 

The selection of column layout and spacing is 

thus dependent upon the strengths which might be 

achieved, and hence the results of the stabilisation trials. 



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38 

Figure 4 – Column spacing based on rotational stability 

Figure 5 – Extrusion stability 

Figure 6 – Column spacing based on extrusion 

Use of cement or lime. 

Rationale 

Lime and cement are traditionally used to improve 

soils with poor engineering properties. This improvement 

is as a result of hydration of lime and cement, 

Network 

taking up excess water, and 

also by cation exchange on the 

surface of individual clay particles 

– the resultant flocculation 

giving a relatively immediate 

improvement in the strength 

of the clay fraction. With time, 

both lime and cement tend to 

stabilise soils by forming cementitous 

bonds between the 

soil particles. 

The slurry lagoon generally 

comprises of sand to clay sized 

particles with high water content. 

The clay sized particles are generally 

derived from the mudstone 

parent rock of the coal workings. 

The addition of quick lime will take 

up water as described above, but 

any improvement due to cation 

exchange is less certain. Hence, 

initial laboratory trials were carried 

out to confirm the feasibility 

and effectiveness of lime and/or 

cement stabilisation of the slurry 

material. 

Laboratory Trials 

Samples of slurry obtained by 

trial pitting were prepared at 

varying additions of lime and cement 

and strength tested in accordance 

with BS1924: Part 2 at 

ages up to 60 days and 30 days. 

It was clear that the 

higher additions of lime gave a 

very quick improvement of the 

slurry but limited increase of 

stabilisation with time. In comparison, 

the additions of lesser 

amounts of lime and the additions 

of cement showed smaller 

initial improvements but increasing 

strength with time, typical of 

the development of cementitous 

bonds. The increased slurry 

strengths achieved in the laboratory were less than 

that shown by calculation to provide reasonably economic 

slopes to the deepest excavation. Further sampling 

and testing were therefore carried out at higher 

percentages of lime, cement and mixture of lime and

Figure 7 – Shear strength from laboratory trials 

Figure 8 – Shear strength from field trials 

cement mixtures; and using the higher specification 

CEM1 cement. 

These results (Figure 7) showed significantly 

higher strengths but considerable inconsistency 

thought in part due to variation in the original condition 

of the slurry for particular sets of data; a phenomenon 

to be expected in reality on site. 

Nonetheless, these later data showed that 

adequate strengths should be achievable at about 5% 

CEM1. There was little apparent benefit in higher cement 

content. A blend of 3% lime and 3% CEM1 gave an 

Network 

apparent early improvement but 

that was not necessary in this 

application and thus discounted. 

It should be noted that 

the strengths of soils stabilised 

under laboratory conditions 

might be in the region of 

60% higher than that achieved 

under site conditions. Thus, 

the design strength of 90 kPa, 

shown in calculation, should be 

based on an admixture proportion 

which gives a laboratory 

strength in the region of 150 

kPa. This was a significantly 

high target strength, particularly 

given the relatively innovative 

application to the stabilisation 

of lagoon slurry. It was essential 

that the results of the laboratory 

trials were validated on 

site at the earliest opportunity. 

Field Trials 

Once the specialist equipment 

had been established on site, 

work began on the shallower 

columns for stabilisation of the 

surface of the lagoons using cement 

additive at selected proportions. 

Thus it was possible to 

use these less critical columns 

to calibrate equipment and to 

subsequently test the column 

strengths achieved on site. 

Undisturbed U100 opentube 

samples were obtained from 

the freshly constructed columns and 

aged in the laboratory before unconfined 

compression strength (UCS) 

tests, or by pocket-penetrometer (PP) where the samples 

were too stiff or brittle to extrude. 

The results show some apparent inconsistency, 

but confirm that adequate strength could generally 

be achieved within 3 weeks (Figure 8). There was 

again no apparent benefit in using higher proportions 

of cement which might only increase the risk of less 

predictable brittle behaviour. The works proceeded on 

the basis of a 5% CEM1 additive (70kg/m3), to be validated 

as specified by Swedish Vane Test (RColPT) and 

Cone Penetration Test (ColPT). 



39



40 

Figure 9 – Shear strength from ColPTs 

Figure 10 – Shear strength from RColPTs 

Figure 11 – Fenwick Reclamation 

Network 

Construction 

RColPT is an accepted standard for in situ stabilised 

soil columns but requires the vane to be embedded 

to the base of the column and equipment may fail if 

too high a column strength is materialised. Similarly, 

ColPT may deviate into the surrounding soil at depth. 

Both were therefore carried out with only a few days 

aging of the columns. Adequate strength gain was 

demonstrated from the RCoIPT and CoIPT tests (Figure 

9 and Figure 10) although a trial pitting exercise 

was required to assess strength gain in the shallower 

part of the column sections, prior to excavation of 

the central mound. 

Conclusion 

The remedial works were completed in late 2010. 

During the course of the process of extinguishing the 

spoil, some 120,000m 3 of spoil were excavated, extinguished, 

cooled then placed and compacted. Temperatures 

in excess of 1,000°C were recorded and 

specific measures were required to control the dust 

associated with fine ash and the movement of hot 

air. A regime of air quality monitoring had been instigated 

before the contract and was continuous until 

contract completion. 

Upon completion, the borrow pit was reinstated 

to the original landform, with the addition of some 

scrapes and hollows to encourage wetland flora, using 

the original top soil material. Fenwick Heap was 

sown with a variety of seed mixes to provide a gradual 

transition from conservation grassland to grass, trees 

and shrubs. The public right of way around the heap 

was reinstated to bridleway specification with regard 

to the popular equestrian use of the area. During the 

contract, a calculation of the carbon footprint of the 

site was made and, to offset the effect of this, an 

additional 60 trees were planted as a feature on the 

junction of two informal footpaths (Figure 11). 

Russell Bayliss is geotechnical team leader in the Parsons 

Brinckerhoff Newcastle office. 

Dr. Alan Common is a civil and geotechnical engineer. His 

PhD thesis was on the effects of electrolytes on the deformation 

behaviour of clays. He was formerly a Parsons 

Brinckerhoff employee. 

Jeff Jennings is a chartered civil engineer with thirty-seven years 

civil engineering and construction experience , both in the UK in 

the Middle East, specialising in contract administration.

Network 

Mined Cavern Stability Survey and 

Risk Assessment for Multiple Use 

Storage Facilities 

by Adrian Dolecki, Cardiff, UK, +44 2920 827 032, doleckia@pbworld.com and Gideon Jones, Cardiff, UK, +44 2920 

827 074, jonesgi@pbworld.com 

The decommissioned Corsham Mine complex (until recently, 

classified) is located beneath a UK Ministry of 

Defence (MOD) site in rural Wiltshire, UK. The belowground 

history of the site commenced in the 19th century 

with the quarrying of a labyrinth of mines using 

haphazard room and pillar mining methods for extraction 

of Great Oolite ( an oolitic limestone referred to as 

Bath Stone), used locally for building in the Bath area. 

The mines were acquired by the War Office around 

1935 and were converted for military purposes as part 

of the World War II effort, including an ammunition storage 

depot with its own underground railway station. 

In the process, the Royal Corps of Engineers 

removed considerable amounts of rock spoil from 

around and below the existing pillars before apply- 

ing additional strengthening measures to the original 

mine pillars and roof sections (Figure 1). This was to 

ensure that the overhead cover was sufficiently supported 

to resist impact from aerial bombardment. In 

the Cold War years from 1961 to 1991, further conversion 

work was completed for the Central Government 

War Headquarters (outside of London), for 4000 staff 

in the event of nuclear war, and equipped with its own 

hospital, telephone exchange, BBC studio and the RAF 

command centre. An underground lake and treatment 

plant provided all the drinking water needed whilst 12 

huge tanks could store the fuel required to keep the 

four massive generators, in the underground power station, 

running for up to three months. The air within the 

complex could also be kept at a constant humidity and 

Figure 1 - Mine roof support Figure 2 - Mine enviroment 



41



42 

heated to around 20 degrees Celsius (Figure 2). 

The existing underground complex comprises 

approximately 115 hectares and 60 miles of underground 

roadways, approximately 30m below ground 

level and bisected by Brunel’s Box Railway tunnel, the 

main line between London and South Wales. 

Project Overview 

Under a nationwide framework contract, in 2010 Parsons 

Brinckerhoff was commissioned to undertake a 

an extensive baseline geological condition assessment 

of pillar and roof stability and, for some above ground 

areas scheduled for divestiture (e.g., the Rudloe No. 2 

site), a ground hazards and development constraints 

plan. The total mine space was split into 21 distinct 

survey areas within six mine complexes and under 

strict military control and direction. Parsons Brinckerhoff 

mobilised two, 3 man survey teams, (in tandem 

with asbestos survey teams) working continuously for 

three months undertaking a risk assessment of mine 

stability (and for asbestos containing material). Thousands 

of supporting pillars were assessed. 

Figure 3 - Data Collection Form 

Network 

Classification System 

Using field data collection forms (Figure 3), a pillar and 

roof classification system (Figures 4 and 5) was developed 

specifically for the project and input into a site 

based GIS system. A complete catalogue of the whole accessible 

area of the mine was mapped. The classification 

system followed best practice rock engineering guidance 

and mining legislation. This assisted in establishing a 

long term inspection and monitoring regime for the mine 

in accordance with the UK Management and Administration 

of Safety and Health at Mines Regulations 1993(7) 

(MASHAM) as required by the HM Inspectorate of Mines. 

The mine complex is vast and each district, or 

area, is being used by workers at varying frequencies. 

How frequently an inspection should take place will vary 

from area to area and should be based on hazard identification 

and risk assessments. Therefore, a guideline 

inspection frequency regime was specified, dependent 

on classification and accessibility requirements. 

Mine Condition and Risk Assessment 

The general condition of most areas of the Corsham

Figure 4 - Mine Pillar Classification System 

Figure 5 - Mine Roof Classification Systm 

Network 

Mine survey are considered to be good as the majority 

of the pillars surveyed have been assigned a Class 1 

category. In areas where re-engineering of the pillars 

and roof has not taken place, the average pillar and rock 

condition is generally reduced, with greater evidence 

of bed delamination and weathering along natural rock 

fractures. Notwithstanding the above, direct evidence of 

pillar stress, even in areas where re-engineering has not 

taken place, was found to be very rare. 

For parts of the complex scheduled for surface 

divestiture, for example below the Rudloe No. 2 site, 

66% of the area below the site surface boundary was 

found to be affected by the mine workings (the remainder 

being un-worked). The wider Corsham Mine surveys 

provided rock quality data for the whole of the development 

boundary which were then assimilated to assess 

the representative condition below the Rudloe No. 2 site 

(Figure 6). 

A conservative threshold of overburden thickness, 

equal to five times the average room (void) 

height, has been taken in order to be adequately protective 

of ground subsidence for the range of development 

options likely to be considered. This equates to 

a reasonable overburden rock thickness threshold of 

≥20m (Figure 7). 



43



44 

Figure 6 - Mine Condition Survey 

Figure 7 - Typical Long Section 

Network 

Three initial risk zones have been derived from this 

20m threshold value. The 20m value represents the lower 

bound of the middle risk category, Zone 2 (ranging from 

20m to 22m), with the remaining two categories derived 

using the remaining data range (16m to 22m for Zone 1). The three risk categories adopted 

are presented below in Table 1. The risk categories in 

Table 1 have been used to zone the site for development 

purposes, as shown on the development constraints plan 

(Figure 8). The rock conditions observed within the mine 

workings were good and all structural supports were generally 

in a good condition. The only viable rock failure mech- 

anism is roof collapse. 

However, although delamination 

of the roof rock is 

likely to remain a possibility 

in places over time, we 

consider the risk of significant 

void propagation (i.e., 

migration to ground level) 

to be very low. 

Conclusion 

Parsons Brinckerhoff considers the risk of mining-related 

ground subsidence associated with the Corsham 

Mines to be very low. Nevertheless, because of time 

and access limitations on the survey, the lack of sufficient 

information currently to geotechnically characterise 

the superficial geology, and the general uncertainty 

regarding the type and layout of future development, a 

precautionary approach to construction has been adopted 

across all areas intended for development. This 

has resulted in a conservative, yet reasonable, set of 

assumptions being applied and recommended which,

Risk Zones 

(Relative Level of 

Risk Increasing in 

the Direction of 

the Arrow) 

Table 1 - Risk Zones 

Minimum 

Rock 

Thickness 

(m) 

Figure 8 - Development Constraints Plan 

Maximum 

Rock 

Thickness 

(m) 

1 >22 - 

2 20 22 

3 16



46 

This article describes the basic requirements for mined 

underground hydrocarbon storage caverns in non-salt 

rocks. Emphasis is placed on those primary geologic and 

hydrologic conditions necessary to assure the excavation 

of successful completed caverns. 

Fenix & Scisson, Inc. conceived and built the 

first mined liquid petroleum gas (LP Gas) storage cavern 

in the U.S. in Texas in 1950 and went on to construct 

about 75 of the approximately 85 caverns built in this 

country during the 34-year period of 1950-1984. Following 

a construction hiatus of 26 years in the U.S., 

Parsons Brinckerhoff is currently mining a large butane 

storage cavern in West Virginia. The greatest amount 

of new cavern activity in recent years has been in Asia. 

Storage of large volumes of moderate vapor pressure 

hydrocarbon liquids in underground storage caverns 

generally offers many advantages over surface storage in 

steel pressure vessels, if suitable rock conditions can be 

found. As defined here, moderate vapor pressure liquids 

include the most widely stored LP Gases (propane and 

butane), plus propylene (an olefin), anhydrous ammonia 

and ethane (at the high end of the moderate vapor pressure 

range). The principal advantages of underground 

cavern storage for these products are: 

• Lower construction cost 

• Lower operating and maintenance costs 

• Enhanced security 

• Lower insurance cost 

• Greater longevity 

• Enhanced use of limited land areas 

Another storage method, steel tank refrigerated 

storage, on surface or at shallow burial depth, may be 

construction-cost competitive with underground cavern 

storage of the moderate vapor pressure liquids, however, 

this relatively uncommon alternative generally has higher 

operating and maintenance costs and is not discussed 

further in this article. 

Network 

Geologic/Hydrologic Requirements 

for Successful Mined Underground 

Hydrocarbon Storage Caverns 

by Bruce Russell, Houston, Texas, 1-281-589-5843, russellb@pbworld.com 

Many of the above-listed advantages also accrue 

to the underground cavern storage of large volumes of 

low vapor pressure hydrocarbon liquids such as crude 

oil, fuel oil, diesel, etc. However, the primary advantage, 

that of lower construction cost, often does not hold true 

because large surface steel tanks for these products are 

quite competitive. Storage of these low vapor pressure 

products in underground caverns is not practiced in the 

U.S. but has been implemented in a few cases in Asia 

and Scandinavia for various reasons. 

Liquid hydrocarbons are stored in two basic types 

of man-made underground caverns: 

• Caverns solution-mined in salt (including salt domes and 

bedded salt) 

• Caverns mined by miners in non-soluble rocks of many 

types (often termed conventionally-mined, or mined 

caverns) 

Large-volume storage caverns in salt can generally 

be constructed at significantly lower cost than similar 

sized caverns in non-salt rock. However, the cost advantage 

of salt versus non-salt is not available throughout 

large land areas that are devoid of usable salt deposits. 

This discussion is restricted to the subsurface conditions 

necessary for successful conventionally-mined caverns. 

The assessment of salt deposits for storage cavern construction 

is not included in this article. 

The basic requirements for mined storage caverns, 

with emphasis on geologic/hydrologic conditions, 

are listed and described below. 

Basic Requirements for Mined Storage Caverns 

The determination of suitability of any particular site for 

construction of a mined underground storage cavern involves 

the evaluation of many diverse factors, which can 

be subdivided into the following two broad categories: 

A. Geotechnical factors – Geologic and hydrologic conditions 

(the primary subject of this paper)

B. Other factors – Logistical, economic, environmental and 

political considerations (listed below but not further 

discussed) 

• Proximity to refineries, production or consumption centers 

and transportation networks of pipelines, roads, 

railways and waterways 

• Availability, zoning status and cost of land, compatibility 

with activities conducted on neighboring tracts 

• Availability of utilities 

• Permitting requirements 

• Security of site 

• Construction costs (including union versus non-union 

labor) 

Storage caverns have been mined in all general 

rock types, which are classified into three broad 

categories - sedimentary, igneous and metamorphic. In 

the U.S., shale caverns are most numerous, followed 

by those in limestone and igneous rocks, and lesser 

numbers in other rock types. Nearly impermeable rock, 

with adequate strength, is the ideal and some shale 

formations readily qualify in this regard. Of greatest 

concern is the possibility of encountering major ground 

water inflows unexpectedly during construction which 

could cause abandonment or very expensive remedial 

action. Highly fractured rock of any type and cavernous 

carbonate rocks (some dolomites and limestones) are 

examples of high risk rock. 

Subsurface geologic and hydrologic conditions 

of importance for storage cavern development include 

the interrelated physical and chemical engineering properties 

and ground water conditions of rock formations 

being considered as potential hosts for desired cavern 

construction. For a prospective rock formation to be considered 

suitable for cavern construction, it must meet the 

following geotechnical requirements: 

1. Adequate structural strength to allow economical mining 

of reasonably large openings which will remain stable 

for decades, with a minimum of artificial support. 

2. Low permeability which will prevent major ground water 

inflow into the cavern, and potential leakage of 

stored product. 

3. Presence of favorable and stable ground water conditions 

which will remain dependable throughout the 

planned lifetime of the cavern to assure containment 

of the stored product. 

4. Physical and chemical inertness among the stored 

product, the cavern host rock and ground water. 

Adequate Structural Strength 

Compressive strength of a rock can be measured on 

core samples in the laboratory, but more important is 

Network 

the strength of the rock mass which cannot be directly 

measured. Following are the principal interrelated conditions 

that affect the rock’s overall strength and how it will 

behave when intersected by excavated cavern openings: 

• Compressive strength 

• Type, spacing, orientation, cohesion, width, filling material 

and surface character of structural discontinuities 

including faults, fractures, joints, shear zones, 

bedding and foliation planes, contacts, veins, dikes 

and open cavities. 

• In situ state of stress. 

Low Permeability 

Permeability of a rock is a measure of its ability to transmit 

fluid under a pressure gradient. Two types of permeability 

must be considered: 

• Primary permeability – The permeability allowing fluid 

flow between mineral grains. Primary permeability in 

directions parallel and normal to bedding in sedimentary 

rocks is often quite different, with horizontal values 

generally higher. Significant primary permeability 

is considered to be very negative with respect to suitability 

for cavern construction because it cannot be 

remedied by grouting. 

• Secondary (or fracture) permeability – permeability due 

to fractures or dissolved openings. Moderate fracture 

permeability can often be significantly reduced by cement 

grouting during cavern construction. Cavernous 

solution permeability in dolomite or limestone could 

be catastrophic to cavern mining. 

Favorable and Stable Ground Water Conditions 

Mined underground storage caverns have historically 

been developed under a basic hydrologic containment 

principle. Simply stated, the cavern must be placed at 

sufficient depth below the natural water table (or below 

the piezometric level in the case of confined water-bearing 

rocks) to ensure that the ground water pressure exerted 

at the level of the cavern is greater than the vapor 

pressure of the product stored within the cavern (at the 

prevailing temperature). In the case of a permeable host 

rock, this will allow potential ground water seepage into 

the cavern, while preventing product leakage upwards or 

outwards from the cavern. One vertical foot of ground 

water exerts a pressure of 0.433 psi per foot at the base 

of the column. The depth of a cavern must be greater 

than the theoretical minimum depth needed, with respect 

to ground water pressure, to provide a margin of safety 

against the potential danger of overfilling or overpressuring 

the cavern, lowering of the water table and even some 

human error during storage operations. 



47



48 

Mined storage caverns are classified into two 

broad classes: “wet” and “dry.” Wet caverns are defined 

as those mined in rocks that have sufficient permeability 

to allow ground water flow into the workings, at atmospheric 

pressure, during the mining process. Lesser inflow 

is to be expected during storage operations, with the 

rates dependent upon vapor pressure of the stored product. 

It is critical to maintain storage pressure at a safe 

level in wet caverns. Exceeding the protective ground water 

pressure will likely blow the water seal, initiate product 

leakage and probably render a cavern unusable for a 

long, uncertain time period. 

Dry caverns are defined as those that are mined 

in tight rocks with very low permeability, that have no 

noticeable flow of ground water into the workings during 

mining, and no flow during storage operations. 

When designing a new mined storage cavern, 

regardless of the prognosis of “wet” or “dry” conditions, 

it must be placed below the effective water level 

to a depth allowing a hydrologic safety factor, in the 

event that actual conditions turn out to be more permeable 

than predicted. 

Outside the U.S., certain sites have been encountered 

where concern exists regarding the long-term 

maintenance of stable ground water conditions due to 

particular combinations of rock permeability, ground water 

recharge potential and topography. To avoid the 

perceived risk of a loss of the vital ground water pressure, 

especially during construction, a few storage cavern 

developers have seen fit to install artificial “water 

curtains” consisting of networks of mined openings and 

boreholes above and/or between large storage chambers. 

No water curtains were installed during construction 

of the approximately 85 mined storage caverns constructed 

in the U.S. 

Physical and Chemical Inertness 

The stored product should be physically and chemically 

inert to the cavern host rock and to ground water as any 

physical or chemical reaction could cause contamination 

of the product and/or deterioration of the rock. It 

is also important that the cavern host rock be resistant 

to deterioration by ground water. Fortunately, compatibility 

problems among stored products, cavern rock and 

ground water are rarely encountered but such possibilities 

must always be considered. 

Geotechnical Feasibility Investigations 

Geotechnical feasibility studies for selecting specific sites 

and confirming suitability for storage cavern construction 

are normally carried out in a series of phases, progress- 

Network 

ing from preliminary low expense screening investigations, 

on to intermediate investigations of individual sites 

and finally to the more costly detailed studies that include 

core drilling, borehole hydrologic testing with packers and 

laboratory tests of representative core samples to determine 

pertinent rock engineering properties. 

Experience is an important factor in feasibility 

investigations for selection of the optimum combination 

of most suitable rock unit with respect to its engineering 

properties, plus an adequate depth to assure an appropriate 

hydrologic safety factor. The opportunity for a feasibility 

study geologist to observe rock behavior during a 

cavern mining operation helps to put the feasibility study 

observations in perspective. 

Sites lacking in suitable rock qualities and/or 

proper hydrologic conditions should be rejected. Borderline 

cases may be accepted with the realization that construction 

costs will be significantly higher than the normal. 

Sedimentary rocks sometimes present difficult 

feasibility choices, for example in the case where a preferred 

rock unit with excellent engineering properties 

happens to be a little too shallow to have the desired 

hydrologic safety factor. A deeper, but less desirable 

unit, from the standpoint of rock structural quality, may 

have the desired hydrologic safety factor. Tradeoffs are 

sometimes necessary in the final analysis, when a particular 

rock unit must be selected for construction, or 

the site has to be rejected. 

Storage Cavern Design and Construction 

Planning 

Underground storage cavern mining always faces risk 

due to unknown subsurface conditions. A major goal of 

the feasibility study is to reduce this risk to a minimum. 

Thorough and accurate characterization of the proposed 

cavern construction horizon, and enclosing rock units, 

by means of the various steps of the geotechnical feasibility 

study is vital in order to provide the necessary 

information to cavern design engineers and avoid costly, 

unpleasant geologic or hydrologic surprises during cavern 

mining. Modeling of the collected geologic and hydrologic 

data makes it available to cavern designers in 

the most usable form. 

Rock strength, orientation and magnitude of 

maximum horizontal stress, and the orientation of significant 

discontinuities such as faults, fracture patterns 

and formation bedding/or foliation are important to 

the designers for determining the preferred directions 

of cavern long-dimension workings, as well as heights, 

continued on page 54

Network 

A Conceptual Design for a Geological 

Disposal Facility for the UK’s 

Radioactive Wastes 

by Steven Majhu, Manchester, UK, majhus@pbworld.com, +44(0)7770 334148 and Peter Gaskell, Manchester, UK, 

gaskellp@pbworld.com, +44(0)7825 298445 

The development and construction of a geological disposal 

facility (GDF) for radioactive waste will be amongst 

the largest engineering programmes ever undertaken in 

the UK. The purpose of this multi-billion pound project 

is to dispose of the legacy radioactive waste and potentially 

those wastes associated with a programme of new 

nuclear power station construction. 

Parsons Brinckerhoff has been responsible for 

the preparation of generic designs for a geological disposal 

facility to support the Nuclear Decommissioning 

Authority’s (NDA) Radioactive Waste Management Directorate 

(RWMD). 

A Geological Disposal Facility 

Although there are various options for the design of a GDF, 

there are some general features that will be common to 

all designs. A GDF would comprise a number of basic elements 

including surface facilities, underground access, underground 

disposal facilities and supporting infrastructure 

and services. An example of what a geological disposal 

facility may look like is shown in Figure 1. 

The surface facilities include those for the receipt 

and transfer of waste from either rail or road transport to 

underground. They also include all the necessary facilities 

for the support of ongoing construction and the provision 

of essential services (power, water and ventilation). 

Waste would be transported underground and emplaced 

in disposal vaults or tunnels depending upon the 

type and nature of the waste and package. 

Geology 

Through its ‘Managing Radioactive Waste Safely’ (MRWS) 

programme [2], the UK Government has decided that a 

site for a geological disposal facility should be found by 

voluntarism, an approach in which communities express 

an interest in participating in the process that would ultimately 

provide the site or sites for a GDF. This means 

Figure 1 - Generic Geological Disposal Facility [1] 

that the geological environments available for the GDF 

will depend on the locations of sites identified by the 

siting partnerships set up by local communities. Hosting 

a GDF is likely to bring significant economic benefits 

to a community in terms of employment and infrastructure, 

maintained over a long period, and any community 

that ultimately hosts a geological disposal facility will 

be keen to understand and agree to the nature of these 

benefits. The approach that the RWMD will take until 

such time as more specific information becomes available 

is to define a limited number of generic geological 

environments, encompassing typical UK geologies, for 

use in illustrative engineering designs. Three geological 

host rock environments have been considered at this 

stage, relating to a higher strength rock, a lower strength 

sedimentary rock and an evaporite rock. 

Overview of Design and Construction 

The depth of the disposal horizon in conjunction with the 

properties of the geological environment will be important 



49



50 

in determining the extent to which the geosphere 1 provides 

isolation and containment of the radioactivity in the 

waste, and in determining the constructability, excavation 

characteristics, support requirements and longevity of any 

underground structures. The maximum depth of construction 

is likely to be defined by practical and economic considerations. 

The increasing difficulties of construction tend to 

impose a practical limit to the depth of disposal of approximately 

1000m below ground surface. However, it may be 

possible to construct a GDF at a greater depth if necessary. 

The underground disposal facility would be accessed 

by shafts and potentially a drift (inclined tunnel), 

however the number and type of underground accesses 

would, in practice, depend on a number of factors, including 

the geological environment and the volume of radioactive 

waste to be disposed. The drift would be constructed 

at a gradient of 1 in 6 and, at depths between 500m and 

650m, would be between 3km and 4km long depending 

on the host rock. The current drift design includes a 5.5m 

diameter, concrete hydrostatic lined section and then 5.5m 

high x 5m wide to the facility horizon or 5.5m diameter 

for its full length depending on the host rock. All vertical 

access shafts would have a finished diameter of 8m and 

would be excavated using well established technology. Permanent 

shaft support would be provided by concrete and 

hydrostatic lining installed where necessary to prevent the 

ingress of water, and a nominal concrete lining where a 

hydrostatic lining is not required. 

Underground excavation would be undertaken 

utilising standard tunnelling techniques such as drill and 

blast, road header and/or tunnel boring machine (TBM) depending 

upon the properties of the host rock. 

Excavation profiles and dimensions would be 

determined based on the prevailing geotechnical characteristics 

of the host rock, and would be sufficient to provide 

adequate long-term stability for the duration of the 

construction, operation and closure phases (currently assumed 

to be approximately 110 years). The disposal vault 

and tunnel cross-sections would vary in size and shape 

from 16m x 16m in a higher strength rock (Figure 2), to 

11.5m x 9.6m in a lower strength sedimentary rock (Figure 

3) and 5.5m x 10m in an evaporite rock (Figure 4). 

Maintenance requirements for the support systems 

will vary with the host rock, but as rock strength reduces 

and/or depth increases, then more reliance would be placed 

on the supports. At this stage, it is assumed that general 

underground tunnel support would be rock bolt, mesh and 

shotcrete, as required to ensure the longevity of openings. 

Network 

1 The rock surrounding a GDF is located below the depth affected by normal human activities and is therefore not considered to be part of 

the biosphere. 

Figure 2 - Excavation Profiles for a Higher Strength Rock [1] 

Figure 3 – Excavation Profiles for a Lower Strength Sedimentary Rock [1] 

Figure 4 - Excavation Profiles for an Evaporite Rock [1] 

The underground infrastructure and support facilities 

have been designed to allow the disposal of waste to 

take place at the same time as ongoing construction by 

providing segregation between these activities. 

The decision on closure of the facility would be 

made after all the waste has been emplaced and following 

consultation with the local community. Closure of the 

underground part of the disposal facility involves backfilling 

the disposal vaults and tunnels, sealing the underground 

openings, and backfilling and closing the access ways. 

The underground layouts are currently idealised, in 

that vaults and disposal tunnels are constructed with uniform 

dimensions on a regular grid pattern. To provide some 

flexibility, they have been arranged in groups/modules (panels) 

which would be constructed in ‘blocks’ of suitable geol-

Figure 5 – Illustrative underground layout in a higher strength rock [1] 

ogy (Figure 5). In practice, at a specific site, disposal vaults 

and tunnels would be located and sized based on the sitespecific 

hydrogeological and geotechnical conditions. 

Nevertheless, indicative studies show that the underground 

area of host rock required for a disposal facility 

to accommodate the 2007 UK Radioactive Waste Inventory 

would be in the order of 5.6km 2 in a higher strength rock environment 

(such as granite) [1]. However, in practice it may be 

possible to build a geological disposal facility over a smaller 

area, by building disposal vaults and tunnels on different levels, 

although this would depend on the geology of the site. 

Next Steps 

The generic designs outlined above have been developed 

to allow an understanding of the implications of implementation 

including such aspects as the underground layout, 

the programme of disposal, the employment opportunities 

and the likely cost. As the MRWS process progresses, details 

of a geological environment, site specific characteristics 

and the disposal system design will become available. 

The generic designs will then evolve from generic to sitespecific 

as site information becomes available at the more 

detailed level and as issues that are recognised today are 

resolved [3]. The current programme assumes a 10 year 

construction period with first waste emplacement in 2040. 

Implementing this project will require a wide 

portfolio of skills to cover the programme management, 

engineering and scientific aspects of the work. To support 

the delivery of this important project, a group of 

companies – the Orchid 2 group – has joined together 

Network 

to offer a seamless team of industry experts with the 

skills required to bring the project to fruition. 

For more information: 

www.nda.gov.uk 

References 

1 Nuclear Decommissioning Authority, Geological Disposal: 

Generic Disposal Facility Designs, NDA/RWMD/048, 

2010 

2 Defra, BERR, Welsh Assembly, Department of the 

Environment Northern Ireland, Managing Radioactive 

Waste Safely: A Framework for Implementing Geological 

Disposal, Cm 7386, 2008. 

3 Nuclear Decommissioning Authority, Geological Disposal: 

Steps towards Implementation, NDA/RWMD/013, 

2010 

Steven Majhu is assistant director of mining services in Manchester, 

UK. He has been involved with work on the geological disposal 

facility for RWMD since 2005 and was lead author on a NDA published 

report which outlined illustrative designs for a geological disposal 

facility in a number of different geological settings. He holds 

a BSc (Hons) geology and MSc in micropalaeontology. 

Peter Gaskell is a mining engineer and has worked on generic 

facility designs since 2008. He has also been involved in disposability 

assessments for different waste packages and in identifying 

the impacts of changes to the waste inventory on generic 

designs. He has a BSc (Hons) mining engineering, PhD (rock 

mechanics, mining subsidence) and is a Chartered Engineer. 

2 The Orchid group consists of Parsons Brinckerhoff, the British Geological Survey, Nuvia, Gardiner & Theobald, the National Nuclear Laboratory, 

the University of Manchester, Oxford Technologies, Nuclear Technologies and SKB International. 



51



52 

Large hydro-electric projects often comprise mined 

caverns to house the turbines and generating equipment. 

The cavern becomes the powerhouse and must 

be linked to the surface by several tunnels, adits and 

shafts, depending upon the configuration. 

Parsons Brinckerhoff is currently involved in a 

number of hydro-electric projects and has experience in 

hydropower caverns from the civil engineering, geotechnical 

engineering and mechanical-electrical engineering 

perspectives. For the latter, Parsons Brinckerhoff is 

the owner’s engineer for the 1,332 MW capacity Ingula 

Pumped Storage project in South Africa, having undertaken 

tender stage designs for the mechanical-electrical 

components of the scheme, most of which are housed 

within twin caverns (see Figure 1). 

The Parsons Brinckerhoff hydropower team is also 

engaged as lenders’ technical advisor (LTA) for two pumped 

storage hydropower schemes in Israel, each with significant 

amounts of tunnelling and each with a pair of mined 

caverns housing turbines and generation equipment. The 

team is also pursuing an LTA position for a medium-sized 

conventional hydropower scheme in Laos with 10km of 

tunnels and a large underground cavern complex. 

Network 

Mined Caverns for 

Hydro-electric Projects 

by Andrew Noble, Sydney, Australia, +61 2 92725427, anoble@pb.com.au 

Figure 1 - Powerhouse cavern layout for the 1,332 MW Ingula pumped 

storage project in South Africa 

The future of cavern engineering for hydropower, 

both conventional and pumped storage, appears to 

be solid, as developers need to go further afield to 

explore the hydropower potential in remote and mountainous 

areas and, in steep terrain, creating a large 

cavern is more cost effective than the alternative of 

stabilising an external slope for the construction of a 

surface powerhouse. 

Pumped storage hydropower schemes 

Pumped storage hydropower is becoming increasingly 

prevalent in countries where other forms of renewable 

energy, such as wind power, have expanded. The grid requires 

stability which is offered by the near instantaneous 

generation of electrical power when a pumped storage 

scheme starts up, and can be used to balance the supply 

when other supply schemes have fluctuating outputs. 

The concept is to use a closed system of water 

(excluding evaporation from the reservoirs) to generate 

electricity by allowing water to flow by gravity from an upper 

reservoir to a lower reservoir through tunnels, shafts 

and turbines. The same water is later pumped up from 

the lower to upper reservoirs through the same facilities. 

While some schemes use a silo-type powerhouse 

(basically a deep shaft near the lower end), the 

majority comprise underground caverns. The selection 

of suitable rock conditions deep within the mountain 

is a challenge for the geological team to assess, including 

a ‘Plan B’ in the event that rock strata are not 

aligned as expected or unfavourable joint orientations 

are encountered. 

A key aim of the designer for pumped storage 

schemes is to develop as much head (H) over as little 

horizontal distance (L) as possible, in other words to 

minimize the L/H ratio. This is principally for economic 

reasons and means that the tunnel waterways designer 

needs to understand the economic driver for the optimum 

layout. 

However, the greater the operating head usually 

means the greater the constructability challenges. Deep

shafts are required in such schemes and an obvious 

optimization is to consider reducing the total waterway 

length by making a steeply inclined shaft and shortening 

the lower tunnel length; conceptually this all makes 

good sense providing that the time and cost and risks 

are appropriately considered with experienced constructors 

during the design phase. A vertical raise bore shaft 

300m deep is far more straightforward than an inclined 

60-degree shaft, although there can be significant cost 

savings in shortening the overall waterway lengths, especially 

if the shaft and lower tunnel are to be steel 

lined, and there are plenty of successful precedents 

where the steeply inclined shaft was selected. 

Access adits, services tunnels and cavern 

complexes 

All hydropower schemes that contain headrace tunnels, 

shafts or caverns require access adits. For schemes 

with a powerhouse cavern, there could be several kilometres 

of tunnels spiraling down from the surface to 

cavern level, resulting in a network of adits and tunnels. 

Some key issues with caverns are: 

Fire-and-Life-Safety (FLS) 

This is related to the means of egress in the event of 

emergency. The transformers are normally housed within 

a separate and adjacent cavern to the main powerhouse 

cavern. This is partly because a single span cavern 

would be very large but more importantly to create 

a separation for safety issues. A dedicated fire fighting 

network is necessary to deal with fires and this often 

requires gravity fed water mains. 

Given that these power stations usually require 

permanent staffing, the whole safety issue is a key aspect 

of initial layout design, requiring close interaction 

between the designers for rock mechanics, hydraulics, 

constructability, FLS, and geotechnics. 

Complex hydraulics of the waterways connections 

Depending upon the final cavern orientation, the final 

arrangement of waterway (headrace) tunnel connections 

may need to be adjusted. The dominant decision in cavern 

design is often the long axis orientation to suit the 

encountered geological jointing. 

Proximity of caverns 

As mentioned above, normally there are at least two 

caverns in any major underground powerhouse complex; 

the main powerhouse cavern and a smaller transformer 

cavern. These need to be as close as possible to minimise 

the costs of the high voltage busbars connect- 

Network 

ing the generators to the transformers, but that offset 

must be weighed against cavern stability and costs for 

support. This is an area where the tunnel designer has 

freedom to optimise the layout in conjunction with the 

other disciplines. 

Confinement and in-situ stresses 

The majority of caverns for hydropower schemes are located 

in hard rock and most remain unlined, i.e., without 

a secondary permanent concrete lining. If the rock is not 

sufficiently sound to stand with only conventional rock 

support, then the economics of the cavern option may 

be in doubt. Also, the complex array of adjacent openings 

would realistically only be manageable in a rock 

mass that is basically sound. 

Confinement, however, is another issue. Although 

the cavern is not a water filled space, the connecting 

waterways on the upstream and downstream 

sides contain high and low pressure water, respectively. 

Those waterways, tunnels or shafts, will be designed 

so that the internal water pressure is contained safely 

within the confines of the mountain and, unless expensive 

steel linings are used extensively, the location of 

the cavern is partly dictated by the confinement design. 

The cavern itself is analysed for the known in-situ stress 

regime deep in that part of the mountain. 

Geotechnical investigations for hydropower 

caverns 

Most caverns for hydropower are located deep into the 

mountainside and access to the ground surface directly 

above the cavern location is often very difficult. In remote 

locations, the challenges will be the terrain, which 

is likely to be very steep as the caverns are frequently 

located where there is a significant height difference, 

and the dense vegetation cover. 

It is not uncommon for inclined bore holes to be 

drilled to reach the planned cavern location, sometimes 

extending to several hundreds of metres depth. For the 

pumped storage schemes in Israel, the developer was 

constrained from accessing many parts of the mountainside 

above the proposed cavern location due to the 

presence of a national park. This required the investigation 

team to make the best use of those areas where 

access was granted, and this resulted in deep vertical 

boreholes, up to 780m deep, to recover rock core samples 

(see Figure 2). This task in itself was a major undertaking, 

with a 20-foot long container required just to 

house the core boxes for each hole. 

The author also has experience of feasibility 

studies for various projects in Africa where the drill rigs 



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were dismantled into manageable sizes, and carried by 

hand up extremely steep hillsides to the drilling location, 

then reassembled. In one case this took a team of 20, 

four days. Helicopters are also used on some large jobs 

to reach critical areas. 

The Lender(s) and the Lenders’ Technical 

Advisor (LTA) 

Generation projects are considered by financiers to be 

among the most secure investments, since with growing 

demand for electricity the market is reasonably assured, 

and the cash flows reasonably certain. The resurgence 

of hydro generation development, particularly in Asia 

and Africa, has led to increased demand for project finance 

for hydro projects. But there are several unique 

features and risks associated with hydro projects that 

financiers need to be aware of. 

In project financing, considerable attention is 

paid to risk. Lenders will examine all aspects of the 

project in great detail to assure that the project will 

function as planned and produce the revenues needed 

to meet operating expenses and service debt. The role 

of the LTA is to identify risks that might influence the 

viability or affect the cash flow of the project, and to 

offer strategic advice on how to avoid or mitigate those 

Network 

Figure 2 – The mountainside housing the powerhouse cavern for a pumped storage scheme in Israel that Parsons Brinckerhoff is advising the 

lenders on 

Geologic/Hydrolic Requirements for...continued from page 48 

widths and height-to-width ratios of the openings. 

The U.S. mined hydrocarbon storage caverns 

range in size from the first one at only 20,000 barrels 

to the maximum of 1,550,000 barrels. These caverns 

are now 27 to 61 years old. The fact that a high percentage 

of these facilities are still in active service is a 

testament to the success of this niche industry. 

risks. The lenders expect their technical advisors to 

point out, at a high level, whether the technology adopted 

is appropriate and what the potential or realised 

items of concern are. The avoidance of reputational 

damage is a key aspect of lenders involvement. When 

structuring the conditions of the loan and the payback 

model, the LTA may recommend that the model takes 

into account the likelihood of delays, which could result 

in consequential delays to the owner’s ability to generate 

revenue and begin to repay the loan. 

This article does not explore the lender’s perspective 

in depth, but is included here to provide an 

overview of what issues may give rise to concern for 

lenders. It is also important to understand that the ultimate 

objectives of the developer and lender are the 

same – a successful project that delivers a satisfactory 

and sustainable financial return. The LTA’s duty of 

care is to the lenders, but objectives are aligned with 

the developer’s. 

Andrew Noble is a technical executive (hydropower and tunnels), 

for Parsons Brinckerhoff in Australia. A chartered civil engineer 

and chartered environmentalist with 23 years experience in 16 

countries, he specialises in the management, design and construction 

of tunnels for hydro-power, water supply and rail projects. 

Bruce Russell has over 50 years of geological engineering experience 

which includes 15 years of mining geology, focused on a 

wide range of mineral deposits in the western U.S., Bolivia and 

the Republic of Korea, followed by 35 years of geological and 

engineering studies related to the development and evaluation 

of conventionally-mined and solution-mined storage caverns in 

many rock types, including salt, in the Midwest and eastern U.S., 

Asia, Europe, the Middle East and South America. He has a degree 

in geological engineering from the Colorado School of Mines.

Network Network 

Ground Observational Methods in 

Mined Tunnel Support Systems 

by Adrian Dolecki, Cardiff, UK, +44 2920 827 032, doleckia@pbworld.com and Gideon Jones, Cardiff, UK, +44 2920 

827 074, jonesgi@pbworld.com 

The city of Bristol, England is served by an existing combined 

sewer system with inadequate capacity, leading 

to the flooding of historic buildings and combined flow 

spills to Bristol’s Floating Harbour. A two year, £9.5 million 

scheme for improving storage capacity up to 4500 

m³ was developed by Wessex Water, the local utility provider. 

The selected option was an 805m long tunnel from 

a drive shaft in a very restricted city centre area (Figure 

1) and an existing 3.66m diameter, 75m deep reception 

shaft. The tunnel passes below the University of Bristol’s 

Civil Engineering Department and its “earthquake shaking 

table” (used for seismic testing) and the Red Lodge 

Museum, an historic building constructed in 1580. The 

project has presented interesting technical challenges 

related to the city centre’s infrastructure, access, topography 

and underlying geology. 

Wessex Water appointed Specialist Engineering 

Services Ltd (SES) as tunnelling contractor for the project, 

and they in turn engaged Parsons Brinckerhoff as 

their geotechnical designer for design of temporary support 

and construction supervision. 

Figure 1 - Drive shaft 

Project Overview 

An extensive site investigation programme of 20 boreholes 

and recovery of 1200m of rock core and downhole 

geophysics identified over 160 changes in ground strata, 

and rock strengths in excess of 480 megapascals (MPa). 

The cost of the investigation was £900,000, indicating 

the importance of understanding the geotechnical risks 

in relation to health and safety, method of construction, 

timescales and cost. 

The tunnel was to be constructed through variable 

soft to very hard ground, ranging from weak saturated 

mudstones and siltstones to very hard interbedded 

sandstone, limestone and conglomerates of Coal Measures, 

Millstone Grit and Carboniferous Limestone, fractured 

and steeply inclined into the advancing face. Water 

pressures of up to six bar (600 kPa) were to be expected, 

as was significant geological faulting and folding. 

The construction method was considered in 

light of the anticipated geology and groundwater conditions. 

The option of using a tunnel boring machine 

(TBM) posed potential major risks in the successful 

completion of the tunnel drive, risks which included 

very abrasive ground, the likelihood of frequent changes 

of face tools being required under large heads of 

water, and the difficulties and cost in recovering a TBM 

if a major incident occurred. The extensive mining experience 

of SES led to the selection of the traditional 

coal mining technique of drill and blast (Figure 2), using 

conventional steel support sets to suit the changing 

ground conditions. Although slower, the method 

was selected on the basis of least risk. 

Geology and Ground Support 

Interpretation and assessment of the geology and ground 

investigation data to predict ground risk (Figure 3) led to the 

determination that the spacing of the steel sets could be 

varied along the drive in order to optimize the support systems, 

using an observational approach and cost effective 

methodology. The NGI Tunnelling Quality Index “Q” and rock 



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56 

Figure 2 - Twin boom jumbo in confined space tunnel section 

mass rating (RMR) were used to calculate the maximum 

unsupported span for the tunnel. An excavation support 

ratio (ESR), related to the use for which the excavation is 

intended and the extent to which some degree of instability 

is acceptable, of 1.6 was considered to be appropriate. 

The maximum unsupported spans, calculated 

Network 

using “Q”, were used to produce support classes for the 

tunnel, which relate to the type of support to be used, the 

spacings of the support and the maximum unsupported 

front. The resultant spans and ground support classes are 

summarised in Tables 1 and 2. 

Along the length of the proposed tunnel drive, 

the predicted support classes are based on the results 

of this calculation (Table 1) and also on structural data 

relating to shear zones and faults from the borehole logs. 

The anticipated support classes for the proposed tunnel 

are detailed on Figure 3, however, they were indicative and 

intended to highlight difficult ground conditions associated 

with faults, shear zones and high groundwater pressures. 

If ground conditions as encountered become more stable, 

then consideration could be given to the use of active support 

measures, such as rock bolts. 

The Parsons Brinckerhoff support design for the 

tunnel used a 3 piece set of straight sections, RSJ’s (rolled 

steel joists) measuring 170mm by 150mm in section with 

a horizontal (flat) beam in the crown, inclined side supports 

with pin joints between members and steel struts with side 

and roof lagging as required. 

Figure 3 - Extract from the main tunnel support cross section illustrating predicted versus actual geological conditions, allowable support 

classes and adopted support systems.

Construction 

Due to the size of the machinery and equipment, the 

first 50m of tunnel drive in fractured ground measured 

4.5m wide by 3m high to allow the use of a shovel, con- 

Figure 4 - Tunnel design and construction 

Network 

Q index (Rock Mass Quantity) 10-40 4-10 1-4 0.1-1 0.01-0.1 

Q description Good Fair Poor Very Poor Extremely Poor 

Excavation span (m) 4.5 4.5 4.5 4.5 4.5 

Support Ratio (ESR) 1.6 1.6 1.6 1.6 1.6 

Equivalent dimension (De) 5-10 3.8-5 2.25-3.8 0.95-2.25 0.38-0.95 

Unsupported span (m) 8.0-15.2 6.0-8.0 3.6-6.0 1.52-3.6 0.56-1.52 

Support class Class I Class II Class III Class IV Class V 

Support spacing (m) 1.25 1.25 1.0 0.75 0.5 

Table 1 - Support classes and spacing based on NGI Tunnelling Index “Q”. 

Support 

number 

Support 

class 

Classi�cation 

(based on Q) 

1 V Extremely 

poor 

Support 

type 

Support 

centres 

AS-500-01 500 500 

2 IV Very Poor AS-750-01 750 750 

3 III Poor AS-1000-01 1000 1000 

4 IIFair AS-1250-01 1250 1250 

Table 2 - Active support system specification 

(1) Base channels and Foot Blocks to be installed if required, in locations where floor conditions dictate. 

Unsupported 

front 

Forepoles Mesh 

roof 

Sheet 

sides 

Struts 

Mesh 

sides 

If speci�ed yes no yes yes 




veyor belt muck removal, ventilation duct and a twin 

boom drilling jumbo. The tunnel then followed a 30m 

radius bend, reducing in size to 3.5m wide by 3m high 

on the final drive, still able to accommodate a jumbo 

drilling rig and scoop tram loader. 

This resulted in the removal of up to 18,000 

tonnes of very hard rock. Additional side cross cuts were 

required to allow storage, turning and passing of machinery 

and equipment. The general explosive charge 

used was 50kg per 2m ‘pull’ (round), in 40 to 45 holes 

with up to 20m per week progress with a 5 day week and 

two 11 hour shifts (two pulls a day). A maximum vibration 

peak particle velocity restriction (PPV) of 10mm/ 

sec² was specified. Probing was also carried out up to 

20m ahead of the face to assess water pressure. 

Conclusion 

Parsons Brinckerhoff developed a project specific rationale 

and decision tree system (Figure 5) for almost 

daily construction inspection and monitoring in order to 

record the “as found” conditions, determine the Q index 

range, change (if necessary) the ground support class, 

and document the approval process for the next day’s 

tunnelling with the site team. 

This allowed Parsons Brinckerhoff to make a rapid 

assessment of observational support design based on 

measured Q and RMR, allowing a ’Motivation Request’ 



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Figure 5 - Decision Tree Flow Chart 

Figure 6 - ‘Motivation Request for Change’ Record Sheet 

Network 

for changes (see Figure 6) in support spacings and rapid 

progress. The tunnel was advanced with efficiency gains 

and economical design through good rock strata and prediction 

of unstable ground ahead. The mined tunnel was 

completed with a pulled pipe conveyance system and 

back grouted annulus, to a strict time schedule and to 

budget in April 2009. 

Adrian Dolecki is technical director and head of sector for Parsons 

Brinckerhoff ground engineering in the UK. He has over 30 

years professional experience in geotechnical engineering, with 

extensive experience in both the mining and tunnelling sectors. 

Gideon Jones is a senior engineering geologist for Parsons Brinckerhoff. 

He has over 16 years professional experience in geotechnical 

and mining related investigation and risk assessment.

Network 

The Design of Sprayed Concrete Linings 

(SCL) to Form Junction Chambers for 

Tunnels in London Clay 

by Binh Soo Liew, Godalming, UK, +44(0)1483 528400, liewb@pbworld.com; Terry Howes, Godalming, UK, +44(0)1483 

528400, howest@pbworld.com; Rory McKimm, Godalming, UK, +44(0)1483 528400, mckimmr@pbworld.com. 

Parsons Brinckerhoff is working for National Grid and 

UK Power Networks (formerly EDF Energy) on a number 

of cable tunnels in London. The cables are required 

either to replace existing overhead lines, which are approaching 

the end of their 40 to 50 year design life, or 

to provide new circuits to boost capacity. Previously, 

undergrounding has been achieved by placing cables in 

trenches, but the density of existing buried utilities and 

the potential disruption to busy urban areas has pushed 

our clients towards deep tunnel solutions. 

The length of such cable tunnels can be up to 20 

km and the depth is often between 20m and 50m. Vertical 

alignments are often constrained by existing rail and tube 

tunnels or corridors for future tunnels (e.g. Crossrail). Horizontal 

alignments must, wherever possible, follow existing 

streets and highways. Internal diameters are either 2.2m 

(UK Power Networks) or 4.15m (National Grid). 

Geology of the London Basin 

In summary, the geology of the London Basin comprises 

the following, in order of increasing age: 

Drift deposits: 

• Made Ground (fill, foundations, etc.); 

• Alluvium (soft clays and silts); and 

• River Terrace Deposits (dense sand and gravel). 

Solid deposits: 

• London Clay (stiff over-consolidated clay, low 

permeability); 

• Lambeth Group (interbedded stiff clays, dense sand, 

pebble beds, cemented shelly beds and hard limestone 

bands, with perched water tables); 

• Thanet Sand (very dense silty sand with a thin bed of flint 

cobbles at base); and 

• Chalk (soft white chalk with hard abrasive flint in bands 

of nodules and sheets; highly variable permeability). 

The cable tunnels and associated shafts in Parsons 

Brinckerhoff’s projects pass through all of the above. 

Owing to its inherent short-term stability and ease of excavation, 

the preferred tunnelling medium in London, and the 

one through which most of the deep London Underground 

tube lines have been built, is the London Clay. It is this 

stratum that, in the last two decades, has been subject 

to a revolution in tunnel excavation and support methodology 

based on what was originally termed New Austrian Tunnelling 

Method (NATM) for excavations in rock and is now 

more accurately called Sprayed Concrete Lining (SCL) for 

underground excavations in soft ground. 

Construction using SCL 

The construction of an underground structure using SCL 

is a sequential cyclic process of excavation, installation 

of a temporary primary support layer, followed by 

a secondary permanent structural lining. The sprayed 

concrete is applied to the excavated surfaces using either 

hand held nozzles or remotely operated spray equipment. 

The SCL can incorporate conventional steel reinforcement, 

erected prior to spraying, or discrete steel 

fibres within the wet concrete mix. 

The use of sprayed-concrete for the construction 

of tunnel linings within London Clay was initially used on 

a large scale in the 1990’s on the Heathrow Express Tunnel. 

The use of the technique, specifically in soft ground, 

was questioned and scrutinised after the failure of the 

tunnel lining on the Heathrow project. Investigations revealed 

that the main problems were related to the construction 

process and the level of supervision and control 

over the installation of the sprayed lining. 

Since then, a number of large, complex, non-circular 

cavern structures have been built using SCL in London 

Clay, such as the Jubilee Line Extension stations. The 

method will also be used to provide underground space 

for Crossrail stations. 

The traditional method of constructing a chamber 

within London Clay has involved the use of precast con- 



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60 

crete or cast iron segmental linings combined with reinforced 

concrete headwalls and portals for openings. 

SCL has the advantages of: 

• minimising the degree of over-excavation; 

• eliminating the use of heavy structural elements; 

• providing versatility in forming transitions between 

sections; 

• minimising durability concerns; and 

• reducing construction times. 

Design of an SCL Junction Chamber 

Constructing tunnels in London Clay is typically done using 

tunnel boring machines (TBM) of specific diameters to 

suit the utility application. The formation of larger underground 

chambers is often required for the launch and/or 

reception of the TBM or for providing a junction between 

two or more tunnels. SCL is increasingly being used to 

construct chambers of complex geometry, such that rigorous 

analysis using 3-dimensional finite element models 

is required. The conceptual model described below provides 

a simplified geometry to allow the design to be carried 

out using simple hand calculations. 

Geometric consideration 

A chamber of simple geometry with gradual transitions 

between sections (Figure 1) is preferred. This minimises 

the eccentricity of thrust forces and the structure can be 

designed using simple hand calculations. This potentially 

removes the need for any steel reinforcement in the SCL. 

Consequently, all sections should be circular in 

Figure 1 - Sprayed Concrete Lined Junction Chamber. 

the vertical plane with typically a truncated oblique cone 

(Figure 2) forming the transition between the main tunnel, 

adit and chamber which are of different cross sections. 

The particular configuration shown in Figure 2 

is for the construction of the connection adit after the 

construction of the main tunnel. The adit may be constructed 

from the chamber outwards. 

Network 

Figure 2 - Discrete elements of the junction chamber. 

In the case where the adit is constructed from 

an intermediate shaft to join the main tunnel, the junction 

chamber should be constructed with a short tunnel at the 

connection with a domed temporary headwall awaiting the 

breakthrough of the main tunnel. Figure 3 shows the configuration 

for such a situation. Instead of truncated oblique 

cone, a truncated right cone is used for the transition element 

from adit to main body of the junction chamber. 

Figure 3 - An alternative configuration for the junction chamber 

constructed from adit to intermediate shaft. 

Principal elements and Analysis 

Main Chamber (Cylindrical) 

The main chamber is basically a cylinder which is subject 

to compressive hoop load due to the surrounding 

ground and superimposed loadings. The horizontal 

ground pressures applied by London Clay on the structure 

are determined with reference to the coefficient of 

earth pressure at rest (Ko). Due to the uncertainty and 

the variation of Ko with time, the designs for excavations 

in London Clay at depths below ground level of up 

to 30 metres consider Ko values that range between 

0.7 and 1.4.

With reference to Muir Wood (2009) 1 , the difference 

in horizontal and vertical stresses in the ground will 

result in an elliptical thrust line profile within the lining. An 

extract from Muir Wood (2009) 1 is included in Figure 4. 

Figure 4 - Extract from Muir Wood (2009) defining the shape of the 

thrust line. 

Therefore, the design of the SCL lining is based 

on keeping the thrust line within the thickness of the lining. 

Details of this will be shown in the following sections. 

Transition Cone 

As previously mentioned, the junction chamber can 

take the two forms as shown in Figures 2 and 3. In 

both cases there is a transition piece required as the 

diameters of the tunnel/adit are smaller than that of 

the main chamber. 

We can visualise the cone as formed by a series 

of discrete circular hoops increasing in diameter as shown 

in Figure 5. It is therefore simple to analyse as a circular 

hoop in accordance with Muir Wood (2009) similar to the 

main chamber above. 

Figure 5 - Visualisation of transition cone as discrete series of hoops. 

Network 

Dome Headwall 

The dome headwall can be designed similarly to domed 

shaft bases. The extract from Table 178 of the Reinforced 

Concrete Designer’s Handbook 2 , which shows the forces 

relating to a dome, is shown in Figure 6. 

Figure 6 - Extract from Table 178, RC Designers Handbook– Forces 

relating to dome structure. 

Conclusions 

A simple method has been described to show how an 

SCL chamber can be broken down into discrete structural 

elements, each of which can be analysed using 

traditional empirical calculations. 

The method is being applied to the production 

of designs and design checks for underground excavations 

in London Clay for chambers of varying cross 

section. This technique is based on the fundamental 

‘middle third’ rule and the classical arch theory allowing 

a simple analytical approach. 

Although it is far from new, Parsons Brinckerhoff’s 

application of the principle to SCL chamber design 

is innovative in its simplicity. 

Binh Soo Liew is a senior tunnel engineer in the Godalming office 

and is a chartered civil engineer with 11 years experience in the 

design and construction of soft ground tunnels in London Clay. 

Terry Howes is a principal tunnel engineer in the Godalming 

office; he is a chartered civil engineer with over 30 years experience 

in engineering design and construction including tunnels 

in London Clay. 

Rory McKimm is the head of discipline for the tunnelling group in 

Parsons Brinckerhoff’s Godalming office. He is a Chartered Engineer 

and Fellow of the Geological Society with over 25 years experience 

in tunnelling, rock engineering, mining and geotechnics. 

1 Muir Wood A.M. – Thomas Young and the Brunels: Masters of Masonry Analysis, Proceedings of ICE, Civil Engineering February 2009 162, No CEI. 

2 Reynolds C.E. and Steedman J.C. - Reinforced Concrete Designer’s Handbook Tenth Edition 



61

APRIL 2012 http://www.pbworld.com/news/publications.aspx PB Network 

62 

Future Issue 

Key Parsons Brinckerhoff staff from around the world have been asked to share their experiences and perspectives for the 25th Anniversary Issue 

of Network, Parsons Brinckerhoff’s technical journal. 

Network 75, The Future of Cities and Urban Infrastructure 

The articles will portray how cities will change in the 21st century, covering these themes: 

• Visions of how cities and the urban environment will evolve in the next 10 to 25 years 

• Adaptation of infrastructure to changing needs, and improvements in infrastructure that pave the way to better living in all parts of the world 

• The roles that planners, engineers, designers, and other infrastructure developers will play in: 

– Inspiring new ideas and innovative thinking for habitat and urban living 

– Creating and implementing better and more effective infrastructure 

– Enhancing the future of our communities 

The topics will cover any aspect of infrastructure, including transportation, buildings, power/energy, resources, sustainability, project implementation, 

water, climate change, and the environment. 

Contact editors Susan Lysaght/John Chow. 

Our Goal 

The goal of Network is to promote technology transfer by featuring articles 

that: 

• Tell readers about innovative developments. 

• Appeal to a broad range of readers. 

• Include only essential information in a readable format. 

• Encourage readers to contact authors for more information. 

Guidelines for Articles 

• Articles should conform to Network format (defined below). 

• Keep your article as short as you can—include only relevant details 

and descriptions. 

• Papers written for other publications will not be accepted unless 

they are modified to conform to Network format. 

Network Format 

• Length: Articles should be 1,200 words or less. 

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of each author. 

• Introduction/Overview: Provide a brief paragraph stating your 

topic and how it is significant 

• Body of text: 

– Clearly describe the challenge you faced and how you or your 

team solved it. 

– Provide exact name of client and state your firm’s role and 

responsibilities. 

– Tell what innovative technologies or approaches you developed 

or used. 

– Provide all units of measures in metrics followed by U.S. Custom- 

Network ©April 2012 

Network 

ary in parentheses. For assistance in converting measures, see 

http://www.onlineconversion.com/ 

• Conclusion: 

– What lessons did you learn? 

– What was the impact of your solution on your project? 

– What does your new technology or technique mean to our firm 

and the state-of-the-art of the industry? 

– What is the current status of your project, technique, 

or technology? 

• Biographical Information: Tell us about your work experience, noteworthy 

professional achievements and contributions to particular 

projects in 2-3 sentences at the end of your article. 

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go to for related information. 

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To Submit Your Article 

E-mail article and graphics files to: John Chow, New York, chow@pbworld.com, 

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Parsons Brinckerhoff Inc., One Penn Plaza, New York, NY 10119, 1-212-465-5000. All rights reserved. Articles may be reprinted only with 

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Executive Editor: John Chow, New York, NY, chow@pbworld.com 

Editor: Susan Lysaght, Corporate Communications, New York, NY, lysaght@pbworld.com 

Guest Technical Editors for this Issue: Mark Dimmock, Sydney, Australia; Nick Edmunds, Manchester, UK 

Graphic Designer: Gary Hessberger, Corporate Communications, New York, NY 

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