P. L. Richard Pang

Geotechnical Engineering Office

Civil Engineering and Development Department

AGS (HK) 1-day Seminar on Geotechnical Baseline Report

5 October 2013

Background

• HKSARG General Conditions of Contract for Civil Engineering Works (1999) - Modelled on the ICE CoC (5th Edition) – Clause 13 (1) - “The Contractor shall be deemed to have examined and inspected the

Site … the nature of the ground and sub-soil …”

– Clause 13 (2) - “No claim by the Contractor for additional payment shall be allowed on the ground of any misunderstanding in respect of the matters referred to in sub-clause (1)”

– Contractor carries the ground risk under Clause 13 of GCC

• Concerns expressed – Bidders are not pricing for the contingency because of competitive bidding

– Overall consequential cost for the Client/Owner is not lowered but sometimes much higher

– Not equitable in principle as the Client/Owner benefits from the project in the long term and should thereby bear the ground risk

– Contractors should not be the “insurer” of the ground but should be employed for their technical competence

– Client/Owner should have better knowledge about the ground up to the moment of tendering

– Insufficient pre-tender site investigation causing major geotechnical risks not identified at early stage

Norwegian Tunnelling Contracts

• The project owner is responsible for the ground conditions • The contractor is responsible for the efficient execution of the works • Bill of Quantity (BoQ) – Unit Price Contracts

– The quantities for all works activities/operations are included in the BoQ – The BoQ items/rates cover all activities/operations that may possibly be needed

• Variations in quantities – The Contractor is reimbursed as per actual performed quantities and his tendered unit prices, which remain

fixed within a preset range of variation (+/- 100% for some contracts)

• Time-equivalents system – Those works activities which are expected to influence the progress are concerted into time parameters,

which are quoted in the contract – Different time parameters must be quoted for different scenarios/applications

• Adjustment on contractual construction time – Based on the predefined time parameters, the total estimated time and total actual time are calculated – Completion time adjustment is the difference between the total estimated time and total actual time

(Kleivan, 1989)

(Since 1970; based on

hard rock drill and blast

tunnelling experience;

lowest project cost)

Timeline Year Title Author

1991 Proposals for Risk Sharing in Cavern and Tunnel Construction Contracts (Unpublished) Ove Arup - Berdal Stromme

1994 Constructing the Team Michael Latham

1997 ASCE Geotechnical Baseline Reports for Underground Construction: Guidelines and

Practices ASCE (Essex)

1998 Review of GCC for Construction Works for the Government of the HKSAR Jesse B. Grove III

1999 General Conditions of Contract for Design and Build Contracts (1999 Edition) ETWB

2001 Construct for Excellence (Chapter 5 – Achieving Value in Construction Procurement) CIRC

2003 The Joint Code of Practice for Risk Management of Tunnel Works in the UK ABI and BTS

2004 Review of Project Implementation Issues of Harbour Area Treatment Scheme (HATS) Stage I ETWB

2004 ETWB TC(W) No. 17/2004 ETWB

2004 GEO Technical Guidance Note No. 24 (TGN 24) GEO

2005 ETWB TC(W) No. 6/2005 ETWB

2005 ETWB TC(W) No. 15/2005 ETWB

2005 GEO Technical Guidance Note No. 25 (TGN 25) GEO

2006 A Code of Practice for Risk Management of Tunnel Works (1st Edition) ITIG

2007 ASCE Geotechnical Baseline Reports for Construction - Suggested Guidelines

Application to Design-Build Procurement ASCE (Essex)

2012 A Code of Practice for Risk Management of Tunnel Works (2nd Edition) ITIG

2013

Guidelines on Contractual Aspects of Conventional Tunnelling

(Previous ITA publications on contractual sharing of risk were published in 1988, 1990,

1992, 1996 and 2011)

ITA

Important Events in Hong Kong (1)

• Proposals for Risk Sharing in Cavern and Tunnel Construction Contracts (1991) – Recommendation on risk sharing approach – HK Government showed strong interest but considered technical, contractual and

implementation details should be further studied

• The Grove Report (1998) – Recommendation on Owner’s acceptance of ground risk

• General Conditions of Contract for Design and Build Contracts (1999) • Clause 13, Inspection of the Site (Alternative I - Method Statement Approach) • The Contractor will have to provide a Sub-surface Assessment and Method Statement at the

time of tender • The Contractor is required to commence ground investigation within 7 days of being given

possession of the Site to verify the Sub-surface Assessment • Claim is entitled if the sub-surface conditions are significantly worse than those indicated in

the Sub-surface Assessment and thereby resulted in significant change in the (i) selected construction method, (ii) design, (iii) resources, and/or (iv) temporary works

• The Supervising Officer (SO) is given a number of powers and functions under Clause 13 Alternative I, e.g. valuation and extension of time for completion

• The preferred use is for a Method Statement instead of the customary placing of all the sub-surface risk on the Contractor

• The Contractor will have to make a case and the SO will make a decision based on the information available

Important Events in Hong Kong (2)

• Construct for Excellence, CIRC (2001) – Recommendations on systematic risk management and equitable risk

sharing

• Review of Project Implementation Issues of HATS Stage 1 (2004) – On equitable risk sharing, “… suitable contract terms will be introduced to

the effect that the contractors will be recompensed for additional expenses and time spent if ground conditions encountered are worse than expected.”

– For risk management, “ … designers will in future be required to provide a comprehensive risk management plan at the design stage …”

• HKSARG Works Policy Technical Circulars (2004 & 2005) – ETWB TC(W) No. 17/2004 - Impossibility/Unforeseen Ground

Conditions/Utility Interference – ETWB TC(W) No. 6/2005 - Implementation of Systematic Risk

Management in Public Works Projects – ETWB TC(W) No. 15/2005 - Geotechnical Control for Tunnel Works

HATS Stage I Review

TUNNEL G

TUNNEL C

TUNNEL D

TUNNEL E

TUNNEL F

TUNNEL AB

Areas of

significant

ground

settlement

• Significant ground settlement in many areas -

up to 1.8 km from the tunnels

• Major public concern due to the extent and

magnitude of the impacts

• Major increase in cost (extra $2.3B over original

project sum of $6.2B) and long delay (4.5 years)

HATS Stage I Tunnels - Drawdown

Groundwater drawdown in highly

fractured rock mass Under-drainage of marine/alluvial

clays and CDV leading to

piezometric drop and settlement Tunnel ‘C’

SOUTH NORTH

Aquitard inhibiting recharge Alluvial sand channel

MARINE DEPOSIT MARINE DEPOSIT

FILL FILL FILL FILL

MARINE DEPOSIT

ALLUVIAL CLAY ALLUVIAL SAND

ALLUVIAL SAND

TUFF BEDROCK TUFF BEDROCK CDV/MDV

CDV/MDV

CDV/MDV CDV/MDV CDV/MDV

FILL

mPD

20

-10

-20

-30

-40

-50

-60

-70

-80

-90

10

0

(from Pang, 2011)

Tunnel Failures worldwide

Developments in Government’s Policy on Risk

Management and Geotechnical Control of Tunnel

Works

• ETWB TC(W) No. 17/2004 on Impossibility/Unforeseen Ground Conditions/Utility Interference (1.6.2004)

• ETWB TC(W) No. 6/2005 on Implementation of Systematic Risk Management in Public Works Projects (21.6.2005)

• ETWB TC(W) No. 15/2005 on Geotechnical Control for Tunnel Works (29.9.2005)

Extract from ETWB TC(W)s (1)

• ETWB TC(W) No. 17/2004 - Impossibility/Unforeseen Ground Conditions/Utility Interference – “It is acknowledged that the Government … will in the long run bear all the costs of

the works, including the cost of the risks, either under the same contract or in subsequent contracts … It is therefore in the interest of the Government to reduce these risks or to minimize the overall cost of the risks wherever practicable.”

– “Project officers should … satisfy themselves that sufficient ground information has been made available prior to commencement and during the detailed design. The extent of ground investigation and/or geotechnical analysis should be adequate for estimating construction cost and duration to an acceptable degree of accuracy.”

– “Should there be uncertainties about the effect of any underground structures on the design and cost of the temporary works and/or permanent works, such uncertainties should be explicitly mentioned in the tender documents so that the associated risk can be priced in the relevant BQ items by the tenderers.”

– “… it may be desirable for the project officers to have more site investigation data or utility search after the occupation of the works site with a view to verifying the ground condition and hence confirming the design prior to tender.”

– “… The contract documents should state clearly that the contractor would be responsible for any investigation works necessary to carry out his obligations under the contract, such as temporary works, by way of the inclusion of a Particular Specification clause.”

– “…project officers should consider to adopt remeasurement approach for underground works…”

– “Where unforeseen ground conditions might have a substantial impact on the required temporary works, consideration may be given to providing separate items in the BQ for these temporary works.”

Extract from ETWB TC(W)s (2)

• ETWB TC(W) No. 6/2005 - Implementation of Systematic Risk Management in Public Works Projects – “ETWB has reviewed the international risk management practice and developed

proposals to manage risks on projects in the Public Works Programme (PWP) in a systematic manner.”

– “SRM should be carried out for public works programme projects with cost estimates exceeding $200M throughout the project period…”

– “Approval for exemption could be given by an officer of not lower than D2 level within the Works Department who should satisfy himself that the potential risks associated with that project have generally been managed or are minimal and can be effectively managed by existing departmental or project procedures.”

– Risk Manager, Project Risk Management Plan, Project Risk Register and Risk Treatment Plan (ETWB Risk Management User Manual)

• ETWB TC(W) No. 15/2005 - Geotechnical Control for Tunnel Works – “The Project Department (PD) shall ensure that the documentation for the

geotechnical design of all permanent tunnel works and the associated temporary works is submitted to the Geotechnical Engineering Office (GEO) of the Civil Engineering and Development Department (CEDD) as set out in this Circular.

The GEO shall audit the geotechnical design and the implementation of the geotechnical design, site supervision and risk management during construction…”

Technical Guidance and References from GEO

• GEO TGN 24 Site Investigation for Tunnel Works

• GEO TGN 25 Geotechnical Risk Management for Tunnel Works

• Catalogue of Hong Kong Tunnels

• Catalogue on Notable Tunnel Failure Case Histories

• GEO Publication No. 1/2007 EG Practice in HK

• Mapping and Classification Sheet for Rock Tunnels

• Mines Division Practice Notes and Guidance Notes

• GEO Report on Ground Control for Slurry TBM Tunnelling

• Ground Control for EPB TBM Tunnelling (in preparation)

GEO TGN 24 - Site Investigation for Tunnel Works

• Extracts from GEO TGN No. 24 – “SI for projects involving tunnel works should be phased. This approach is

necessary as different phases of the project have different requirements.”

– “Sufficient time should be allowed in the construction programme for the results of additional GI and site inspection and monitoring to be fed back into the design and risk management processes…”

– “… The client should include adequate funding for SI in the project cost estimate. ”

The TGN promotes: – In view of the importance of planning of ground investigation and interpretation

of the results, when consultants are selected for major tunnel projects, significant weight should be placed on their geological and geotechnical engineering knowledge and expertise, and on their knowledge and experience of local ground conditions

– SI should identify geological and hydrogeological conditions as well as utilities and buried installations

GEO TGN 24 - Site Investigation for Tunnel Works

The TGN promotes: – For the benefit of planning, design and construction of tunnel projects, all factual

geological data, particularly that revealed from tunnel faces, should be documented

– Pre-tender SI should be sufficient to obtain data for the reference tunnel design including risk control and mitigation measures and for contract preparation

– Horizontal or directional coring should be carried out immediately on confirmation of the tunnel alignment, in order to yield early data to maximise its benefit for the design

– New boreholes should generally extend to a sufficient depth below the invert of the tunnel/shafts. For tunnels in rock, this should be at least 2.5 x tunnel diameter (or crown to invert dimension) below the invert

– Where boreholes are found close to or intercepting the tunnel, the risk of these boreholes not properly grouted should be assessed. All metal casings should be removed and boreholes properly grouted

– Additional GI, e.g. probing ahead, during construction

GEO TGN 25 - Geotechnical Risk Management

for Tunnel Works

• Extracts from GEO TGN No. 25 – “Geotechnical risk management should be an integral part of the overall project

risk management, and be an integral consideration in the planning, design, procurement and construction of all tunnel works.”

– “Geotechnical risk management should be undertaken at the start of every project. It is a cyclical process that continues throughout the duration of the project, with all the activities being reviewed and the assessment updated on a regular basis. The client should ensure that qualified professionals with relevant geotechnical and tunnelling experience are employed in the project risk assessment/ management team. Insurance of the risk does not remove the need or reduce the responsibility for the client to ensure safety is properly managed.”

– “Site investigation, including a comprehensive desk study, site reconnaissance, a carefully designed project-specific ground investigation and a condition survey of the sensitive receivers, is an essential element in identifying geotechnical risks.”

GEO TGN 25 - Geotechnical Risk Management

for Tunnel Works

Important Aspects: – Client responsibility – Competent personnel – Systematic risk management (early stage input and systematic and

continuous management) – Risk identification, assessment and control (risk register and GBR/GRC) – Traceability to action parties (those who have the best means of

controlling the risk) – ALARP principle – Risk acceptance criteria – Low probability and high consequence events – emergency

management – Unexpected combinations of factors/magnitude of single factor – Contract control and risk sharing – Standards for protective, preventive and precautionary measures – Audit by party not directly involved in project implementation

TGN 25 - Geotechnical Risk Management

- Examples of Geotechnical Hazards

Examples of Geotechnical Hazards Risk Treatment Options

Variable rockhead and mixed ground conditions Avoid/reduce the risk, e.g. by selecting a

suitable tunnel alignment based on

adequate site investigation

Reduce the risk, e.g. by specifying or

selecting appropriate tunnelling

method(s) with adequate additional site

investigation during construction

Treat the risk, e.g. by specifying

appropriate ground support (e.g. precast

segmental linings with back grouting),

ground strengthening, groundwater

control and containment measures, and

implementing preventive or protective

works

Presence of buried obstructions or voids (e.g. corestones, boulders, disused

piles, old seawalls, cavities in karst and other artifacts)

Presence of foundations and other subsurface installations

Presence of permeable zones that may be subject to high groundwater

pressure or that may convey large quantities of inflow

Presence of weak or compressible ground (e.g. weak/fractured zones, faults,

fissures, clay-coated discontinuities, granular soils and soft/compressible

soils). Ground under very high or very low insitu stress

Presence of explosive or poisonous gas (e.g. methane) or other aggressive

chemicals

Salinity of groundwater

Contaminated ground, e.g. due to ingress of leachate from landfill

Government Tunnel Projects

with Risk Sharing Mechanism

(Note: Information based solely on submissions made to GEO.)

• Project Departments: – DSD, 4 projects – HyD, 1 project – CEDD, 2 projects

• Contract Type Adopted:

– Design and Build: 3 – Engineer’s Design: 2

• Examples of Risk Sharing Mechanism

• GBR (forms part of the contract documents) • Differing Site Conditions (DSC) clause (included in the Special

Conditions of Contract) • Remeasurement for items with uncertain quantities • Extension of Time allowed

Lai Chi Kok Transfer Scheme (Ip et al., 2009)

– Comprehensive risk management plan at the design stage – Sufficient ground investigation works – Risk register maintained during the design stage and carried

through to the construction stage – Geotechnical Data Report

• Factual information that is relevant to the tendering made known to the tenderers

– Geotechnical Baseline Report (GBR) • Conditions based on which the tenderers are expected to submit their

tenders • Forms part of the contract documents

– Differing Site Conditions (DSC) clause to effect the equitable sharing of risks

– GBR and DSC enable a contractual baseline to assess the validity of the principle of a claim

– Use of remeasurement for items with uncertain quantities and allow extension of time if the ground conditions are worse than the GBR

HATS Stage 2A (Tai et al., 2009)

– Comprehensive ground investigation at planning stage

– Risk register being continually updated and to be carried through to the construction stage

– Design-bid-build contract with remeasurement of major works items

– Specification of the drill and blast method and water inflow limit in the contract

– Reimbursement of payment for works in dealing with ground conditions and with uncertain quantities

– Provisions in the contract for extension of time for completion of the works

• Example of “Differing Site Clause” used – “The Contractor’s Proposals shall be deemed to have been based on the Sub-

surface Conditions provided in the GBR…” – “If, during the execution of the Works, the Contractor encounters sub-surface

conditions which are significantly worse than the Baseline Sub-surface Conditions and such as to necessitate change in (i) the selected construction methods, (ii) design, (iii) resources and/or (iv) temporary works, he shall within 7 days of it becoming apparent that the sub-surface conditions will give rise to a claim notify the Supervising Officer (SO) in writing…”

– “… the SO shall value those changes in accordance with the principle of Clause 61(4) he considers necessary to deal with the sub-surface conditions and, if the SO considers that the Contract is fairly entitled to an extension of time for the completion of the Works or any Section thereof, he shall grant extension of time and adjust the Contract Sum accordingly.”

– “The Baseline Sub-surface Conditions and the Contractor’s Proposals shall represent the yardstick for such valuation and extension of time.”

Extract from the SCC of a PWP Project

Contract Form

• Pilot Use of NEC in PWP

– Since 2009, > 40 contracts have been selected as pilot

– Works Departments to adopt NEC form in all public works contracts including design and build contracts for tenders first gazetted or called in 2015 and 2016 as far as possible

• Risk Allocation

– Conventional contract:

– Contractors to make allowance in their tender price to cover the risk of financial loss due to unforeseen ground conditions while the Government pays the priced allowance irrespective of whether the risk will materialize or not

– NEC:

– Contractors need not price the concerned risk allowance in their tender price while the Government pays only when such ground risk materialises

– Tenderers can thus offer lower bid for contracts

– Compensation events, Contractor’s entitlement to EOT and payment

Key Issues

• Site investigation You cannot deal with the geotechnical risks if you do not know what you do not

know; allow sufficient time for adequate site investigation and apply engineering geological skills; identify gaps and possible variations

• Geotechnical risk management It is important to identify systematically the hazards and risks section by section

of the tunnel taking into account the construction methods (esp. identify the brittle failure modes) and ensure mitigation measures are taken - Just knowing the mitigation measures that need to be taken is not good enough; designs should be robust and documented (for independent audit); the client takes ownership of the geotechnical risks

• Information/Knowledge dissemination and Standards Safety-critical information and knowledge need to be consolidated and

disseminated; set minimum standards and performance limits in the contract

Key Issues

Contract issues Design-bid-build versus Design and Build Design responsibility well defined Systematic Risk Management (geotechnical hazards, construction methods

related risks and GI data gaps to be identified section by section) Reference design to be buildable and supported by adequate GI for

tendering Estimating using Risk Analysis (ERA) – assess gaps in GI data and possible

variations in ground conditions and their impact on cost and programme GDR and GBR/GRC Differing Site Conditions clause (define “significantly worse than Baseline”) Clear basis for remeasurement and assessment of claims (SMART principle) Competent personnel (include for agreeing ground conditions encountered) NEC (simplicity, clarity, promotes good management, risk sharing)

Tunnel construction in Hong Kong

(~460 km up to 2012; ~0.42 km of tunnels/sq km of land area)

END

References (1)

ABI/BTS (2003). The Joint Code of Practice for Risk Management of Tunnel Works in the UK.

ASCE (2007). ASCE Geotechnical Baseline Reports for Construction - Suggested Guidelines. The Technical Committee on Geotechnical Reports of the Underground Technology Research Council. American Society of Civil Engineers.

CIRC (2001). Construct for Excellence. Report of the Construction Industry Review Committee, Hong Kong, 213 p.

http://www.legco.gov.hk/yr00-01/english/panels/plw/papers/plw0611-487e-scan.pdf

Director of Audit (2004). Harbour Area Treatment Scheme Stage I. Report No. 42 of the Director of Audit, Chapter 3, 31 March 2004, Audit Commission, Hong Kong, 68 p. http://www.aud.gov.hk/pdf_e/e42ch03.pdf

ETWB (2004). Impossibility/Unforeseen Ground Conditions/Utility Interference. Environment, Transport and Works Bureau Technical Circular (Works) No. 17/2004, Hong Kong SAR Government, 6 p.

http://www.devb.gov.hk/filemanager/technicalcirculars/en/upload/66/1/C-2004-17-0-1.pdf

ETWB (2005a). Implementation of Systematic Risk Management in Public Works Projects. Environment, Transport and Works Bureau Technical Circular (Works) No. 6/2005, Hong Kong SAR Government, 8 p.

http://www.devb.gov.hk/filemanager/technicalcirculars/en/upload/8/1/C-2005-15-0-1.pdf

References (2)

ETWB (2005b). Geotechnical Control for Tunnel Works. Environment, Transport and Works Bureau Technical Circular (Works) No. 15/2005, Hong Kong SAR Government, 12 p. http://www.devb.gov.hk/filemanager/technicalcirculars/en/upload/8/1/C-2005-15-0-1.pdf

Grove III, J. B. (1998). Review of General Conditions of Contract for Construction Works. Agreement No. CE 99/97. Report for the Government of the HKSAR.

http://www.constructionweblinks.com/Resources/Industry_Reports__Newsletters/Nov_6_2000/grove_report.htm (uploaded on the website in 2000)

GEO (2005a). Site Investigation for Tunnel Works. Technical Guidance Note No. 24 (TGN24), Geotechnical Engineering Office, Civil Engineering and Development Department, Hong Kong, 8 p. Updated in 2009.

http://www.cedd.gov.hk/eng/publications/guidance_notes/doc/TGN24.pdf

GEO (2005b). Geotechnical Risk Management for Tunnel Works. Technical Guidance Note No. 25 (TGN25), Geotechnical Engineering Office, Civil Engineering and Development Department, Hong Kong, 10 p. Updated in 2009. http://www.cedd.gov.hk/eng/publications/guidance_notes/doc/TGN25_2a.pdf

GEO (2009). Ground Control for Slurry TBM Tunnelling. GEO Report No. 249. Geotechnical Engineering Office, Civil Engineering and Development Department, Hong Kong, 57 p. http://www.cedd.gov.hk/eng/publications/geo_reports/geo_rpt249.htm

References (3)

GEO (2012). Catalogue of Notable Tunnel Failure Case Histories (Up to October 2012). Geotechnical Engineering Office, Civil Engineering Development Department, Hong Kong, 237 p. http://www.cedd.gov.hk/eng/publications/geo/notable_tunnel.htm

GEO (2013). Catalogue of Hong Kong Tunnels (Up to September 2013). Geotechnical Engineering Office, Civil Engineering Development Department, Hong Kong, 59 p. http://www.cedd.gov.hk/eng/publications/geo/hktunnel.htm

Grov E. (2012). Contract Philosophy in Norwegian Tunnelling. Contracts in Norwegian Tunnelling Publication No. 21. Norwegian Tunnelling Society.

HKIE (2007). Tunnels and caverns in Hong Kong. Invited Paper. Commemorative Volume of the 40th Anniversary of the Southeast Asian Geotechnical Society, Malaysia, 8-11 May 2007.

HKSARG (1999a). General Conditions of Contract for Civil Engineering Works 1999 Edition. The Government of the Hong Kong Special Administration Region. http://www.devb.gov.hk/filemanager/en/content_188/gf548.pdf

HKSARG (1999b). General Conditions of Contract for Design and Build Contract 1999 Edition. The Government of the Hong Kong Special Administration Region. http://www.devb.gov.hk/filemanager/en/content_188/gf5491.pdf

Ip, A.W.C., Lam, E.W.C. and Cheung, P.C.W. (2009). Design and Planning of Lai Chi Kok Transfer Scheme, Hong Kong. ITA-AITES World Tunnel Congress 2009, 22-28 May 2009.

ITA (2013). Guidelines on Contractual Aspects of Conventional Tunnelling. ITA – Working Group No. 19 Conventional Tunnelling. International Tunnelling and Underground Space Association.

References (4)

ITIG (2012). A Code of Practice for Risk Management of Tunnel Works (2nd Edition). The International Tunnelling Insurance Group.

Latham, M. (1994). Constructing the Team. Final Report of the Government/Industry Review of Procurement and Contractual Arrangements in the UK Construction Industry. HMSO.

LegCo (2004a). Harbour Area Treatment Scheme Stage 1. Public Accounts Committee (PAC) Report - 23 June 2004, Chapter 3, Legislative Council, HKSAR, 28 p.

http://www.legco.gov.hk/yr03-04/english/pac/reports/42/ch3.pdf

LegCo (2004b). Review of Project Implementation Issues of Harbour Area Treatment Scheme (HATS) Stage. Paper for discussion by Legislative Council Panel on Planning, Lands and Works on 29 June 2004, CB(1)2221/03-04(03), Legislative Council, HKSAR, 20 p. http://www.legco.gov.hk/yr03-04/english/panels/plw/papers/plw0629cb1-2221-3e.pdf

Ove Arup – Berdal Stromme (1991). Proposals for Risk Sharing in Cavern and Tunnel Construction Contracts. Report prepared for Consultancy Agreement for the Cavern Projects Studies (CAPRO). Geotechnical Control Office, Civil Engineering Services Department, Hong Kong. (Unpublished)

Pang, P.L.R. (2011). Geotechnical control and risk management of tunnel projects In Hong Kong. Proceedings of the International Conference on Tunnelling & Trenchless Technology 2011, Kuala Lumpur, Malaysia, pp. 41-51.

Tai, R., Chan, A. and Seit, R. (2009). Planning of deep sewage tunnels in Hong Kong. ITA-AITES World Tunnel Congress 2009, 22-28 May 2009.